Category Paving the Way for Apollo 11

Scratching the Moon

A BOUNCY LANDING

The 6-month hiatus after Surveyor 2 was not due to concern over the loss of that spacecraft, but to the wait for the restartable version of the Centaur. The two-burn configuration traded payload capacity against the hardware to restart the engines and the cryo-propellants that would be vented while coasting in parking orbit, but it offered Surveyor launches in winter months,[33] considerably lengthened the launch windows, and increased the flexibility in selecting the arrival time for optimal illumination at the landing site. The Centaur stage demonstrated its restart capability by a launch on 26 October 1966, thereby completing its test program.

The target for Surveyor 3 was a 60-km-diameter circle in the southeastern part of Oceanus Procellarum, centred 120 km southeast of the crater Lansberg. Its attraction was that although it was crossed by a ray from Copernicus 370 km to the north, at telescopic resolution it was sparsely cratered. The smooth patch of mare material was broken about 20 km to the west by rough hummocky terrain and isolated hills, and was bounded to the east by low ridges. It had been photographed at medium resolution by Lunar Orbiter 1 as target I-P-7, and at high resolution by Lunar Orbiter 3 as III-P-9c. These pictures revealed the presence of sub-telescopic craters in the target circle – with one, just over 1 km in diameter, situated very near the aim point. As a smooth-looking patch of Oceanus Procellarum, it bore a similarity to the Surveyor 1 landing site in the Flamsteed Ring, some 650 km to the west.

Surveyor 3 lifted off from Pad 36B at 07:05:01 GMT on 17 April 1967. The Atlas jettisoned its booster section at T+ 142 seconds and the sustainer engine shut down at T + 238. Once free of the Atlas, the Centaur established the desired circular parking orbit at an altitude of 160 km – with insertion at T+569 seconds. The coasting phase would vary between 4 minutes and 25 minutes, depending on the geometry of the translunar injection – in this case it was to be 22 minutes 9 seconds. While coasting, the Centaur first fired two 50-pound-thrust hydrogen peroxide thrusters to settle the remaining propellants in their tanks, then continuously fired two 3-pound thrusters to maintain this condition. It had two clusters of 3.5 and 6- pound thrusters to control its attitude, and while maintaining its longitudinal axis to the local horizontal it rolled at a rate of 0.17 degree per second in order to even out solar heating of its payload and vented any propellant boil-off.

Owing to the predawn launch, the Centaur emerged from the Earth’s shadow at 07:21:25. About 40 seconds prior to the translunar injection, the 50-pound thrusters fired again to guarantee that the propellants would enter their feed pipes. The main engines were shut down when the inertial guidance system sensed that the requisite velocity had been achieved – in this case at 07:38:49, after a 108-second burn. As on earlier missions, after it had configured and released the spacecraft, the spent stage performed the separation manoeuvre. Once free, Surveyor 3 stabilised itself and then adopted its cruise attitude. The midcourse manoeuvre at 05:00:03 on 18 April lasted 4.3 seconds and the 13.8-ft/sec change in velocity was entirely devoted to achieving the ‘critical component’ required to reduce the divergence from the centre of the target circle from the initial 480 km down to a mere 5 km.

The pre-retro manoeuvre in which the spacecraft departed from its cruise attitude involved starting a yaw of-158 degrees at 23:23:30 on 19 April and a pitch of-76.8 degrees at 23:30:17 to align the thrust axis with the velocity vector. The final roll of -64 degrees initiated at 23:34:35 was to optimise the RADVS. The initial approach was at 23.6 degrees to the local vertical. This would require a significant gravity turn during the vernier phase of the descent to force the trajectory to vertical.

The altitude marking radar was enabled at 23:59:33, and issued its 100-km slant – range mark at 00:01:12.829 on 20 April. The delay to the initiation of the braking manoeuvre was specified as 5.090 seconds. The verniers ignited precisely on time, and the new ‘high-impulse’ retro-rocket 1.1 seconds later – at which time the vehicle was travelling at 8,618 ft/sec. The acceleration switch noted the peak thrust of 9,550 pounds fall to 3,500 pounds at 00:02:00.587, giving a burn duration of 40.0 seconds. After allowing the thrust to tail off, the casing was jettisoned at 00:02:12.429. At burnout, the angle between the vehicle’s thrust vector and velocity vector was 21.1 degrees.

When the RADVS-controlled phase of the flight began at 00:02:14.642, the slant range was 36,158 feet (and because the velocity vector at burnout was offset to vertical, the altitude was 32,900 feet) and the total velocity was 483 ft/sec (and since the vehicle had maintained its thrust along the velocity vector extant at the time of retro ignition, the longitudinal rate was 462 ft/sec). The altimeter had locked on at a slant range of 43,700 feet, only to drop out again. So when the RADVS was given control it aligned the thrust axis along the velocity vector extant at retro burnout

The descent of the Surveyor 3 spacecraft depicted in two sections, one for slant ranges above 1,000 feet and the other below 1,000 feet.

and flew with the verniers at 0.9 lunar gravity, very slowly accelerating as it descended. When the altimeter locked on again at 00:02:15.786, attitude control was switched from inertial to radar, and the thrust axis was swung in line with the instantaneous velocity vector to initiate the gravity turn. On intercepting the ‘descent contour’ at 00:02:33.816, the slant range was 22,300 feet and the speed was 495 ft/sec. By the 1,000-foot mark at 00:03:53.023, the vehicle was descending almost vertically with a sink rate of 103.3 ft/sec. When the 10-ft/sec mark was issued at a height of 46 feet at 00:04:10:623, it seemed to be home and dry.

But at 00:04:13.275, at a height of 30 feet, one of the three angled radar beams lost its lock on the surface. As the flow of data to the closed-loop computer abruptly ceased at 00:04:13.387, the control system reverted to its inertial guidance system to maintain its attitude and throttled the verniers to cancel out 0.9 of lunar gravity. But because the RADVS was no longer operative, it was unable to issue the 14-foot mark intended to cut off the verniers!

At 00:04:18.050 the vehicle touched down with a vertical rate of about 6 ft/sec. Although it was level at this time, the ground was sloping down to the west, causing leg no. 2 to make contact first. In response to the tilt induced by the other two legs touching down, the flight control system – which was in attitude-hold mode and did not realise that it was on the ground – increased the thrust of

The axial forces on the shock absorbers of the three landing legs of Surveyor 3 from first touchdown to finally coming to rest.

verniers no. 1 and 3 to re-establish a level attitude, and this additional thrust caused the vehicle to lift off.

After peaking at about 38 feet, the vehicle made second contact at 00:04:42.030 some 50 feet west of the initial point, this time at a vertical rate of 4 ft/sec. Just as previously, the slope caused leg no. 2 to touch down first and in its effort to hold its attitude the vehicle lifted off again. The engines were cut off by a command from Earth at 00:04:53.907 – at which time the vehicle had peaked at a height of 11 feet and was at 3 feet and falling. Since a portion of the thrust had been aimed laterally at each liftoff, this had built up a horizontal component, with the result that when the vehicle struck the surface its vertical rate was only 1.5 ft/sec but it had a horizontal rate of 3 ft/sec. The elasticity in its legs caused it to rebound several inches and hop another 18 inches further downslope before it settled at 00:04:54.420, some 36 feet west of its second point of contact. The gyroscopes indicated the lander to be tilted towards the west at an angle of about 12.5 degrees from vertical.

An investigation concluded that the most likely cause of the RADVS dropping out as it neared the surface was that its logic ordered a ‘break lock’ as one of the beams crossed a field of rocks – to a microwave radar, angular rocks would have appeared much as broken mirror fragments would to a searchlight. The circuitry was designed to make the radar tracking circuits select the strongest signal if several were present. It was essential to ignore antenna ‘side lobes’ when the radar was preparing for the gravity turn. As Surveyor 3 made the final vertical descent, the scintillating side lobe had obliged the system’s logic to break its lock. As the probability of losing lock on the main beam during the vertical phase of the descent was negligible, it was decided that this problem would be eliminated on future missions by having the flight control system inhibit this side-lobe rejection logic upon receiving the 1,000- foot mark.

The first 200-line picture was received 58 minutes after landing, and a total of 55 wide-angle pictures were obtained in this mode. For this mission, a small visor had been added to the hood of the camera to prevent direct sunlight from penetrating the optical train in the hope of reducing the glare that had afflicted Surveyor 1 when the Sun was above 45 degrees of elevation. Surveyor 3 arrived approximately 23 hours after local sunrise, and in the orientation in which the vehicle landed the camera was on the eastern side with the Sun 11 degrees above the horizon. There was therefore surprise that many of the preliminary pictures were partially or completely obscured by a veiling glare. It was concluded that either engine efflux or fine particles stirred up by the engines during the ‘hot’ landings had coated part of the camera’s mirror such that when that part of the mirror was directly illuminated by sunlight the view of the lunar surface was obscured. In addition, any scene that included terrain which strongly reflected sunlight was similarly degraded. Later, intermittent sticking of the mirror in both its azimuth and elevation motions implied that dust had penetrated its mechanism. The hood rotated in azimuth with the mirror, and the mirror could be rotated in elevation to seal the hood, but the engineers had been reluctant to start off in that configuration in case the mirror failed to open. A better hood was already in development. As events would show, the camera’s operational issues would impair the imaging schedule and the glare would degrade the results. A telemetry problem meant that scanning for the Sun and Earth could not start until 06:32. This issue had appeared at the time of the second contact in the protracted arrival. It proved to be a signal processing failure. The fact that the inoperative RADVS lost its high-voltage supply at the same time implied that the signal processing problem was the result of an electrical arc. After a detailed study of the performance of the system identified a number of short circuits, a work-around was devised to minimise the impact on the surface activities. Meanwhile, the Sun and Earth acquisition was completed at 08:15, and the first 600-line picture was taken at 08:42. By handing over in succession, the Deep Space Network stations at Goldstone in California, Canberra in Australia and Madrid in Spain maintained continuous communication with the lander.

An analysis of the early pictures determined that the horizon was 5 degrees higher than it would have been if the lander were on a level plain – indicating that it was in a shallow depression. From the tilt, it was inferred to be on the eastern interior wall of a medium-sized crater.

In-flight tracking could locate the landing site only to within a few kilometres, but the crater in which the vehicle had settled was able to be identified by comparing the landscape observed at ground level with the overhead view of frame H-154 taken by Lunar Orbiter 3 – although obviously the lander was not present at the time that this picture was taken. This showed that Surveyor 3 was within 2.8 km of the aim point. The area was in frame H-125 taken by Lunar Orbiter 4 in May 1967, but because that mission was mapping from high altitude the resolution was insufficient to show the lander – nevertheless, the resulting refinement of the selenodetic grid enabled the coordinates of the site to be measured to an accuracy of better than +0.01 degree in each ordinate.

Once the crater in which Surveyor 3 landed had been found in overhead imagery, its diameter was measured at about 200 metres. It was actually the largest of a tight cluster of craters arranged in a pattern which would later be dubbed the Snowman. Photoclinometry of H-154 suggested that the crater was about 20 metres deep, that there was a smooth transition from the concave floor, that the slopes of the interior walls averaged 10 to 15 degrees, and that the rim was low and gently convex. There was an inflection in the profile from concave to convex about half way between the centre and the rim crest, in both radial and vertical directions. The ‘ground truth’ of Surveyor 3 offered a means of checking the automated photoclinometry of overhead imagery – in particular, the depth of 20 metres was seen to have been overestimated by about 5 metres.

The overhead view resolved about 100 small craters scattered over the floor, inner slopes and rim of the main crater. These ranged in size from 25 metres down to the effective limiting resolution of 1 metre. Most had gentle interior slopes and rounded rims, but a few had steep interior slopes and sharp rims. Since blocks were of higher albedo than the surface material it was possible to discern blocks down to half a metre in size, and it was evident that most were related to three of the largest craters superimposed on the main crater. By taking bearings on features and relating these to the overhead perspective, the location of the lander could be pin-pointed to within 0.5 metre – it was almost half way between the centre and the rim crest. Because it was at the inflection of the slope, its foot pads were about 7 metres below the rim

A photograph by the 61-inch reflector of the Lunar and Planetary Laboratory of the University of Arizona showing the part of Oceanus Procellarum to the southeast of Lansberg (top left corner) to which Surveyor 3 was assigned. Note the hummocky terrain to the west and the wrinkle ridges to the east. The outline shows the area covered by the next illustration.

crest and about 7 metres above the centre of the cavity. In fact, the eastern rim of the crater proved to be beyond the camera’s horizon in the upslope perspective. In an exercise analogous to field surveying, the wealth of detail within the crater enabled a topographic chart of its interior to be compiled – it was an excellent example of how lunar orbiters and landers could work together. The tilt of the lander was measured by a variety of methods and estimated at 12 degrees, inclined almost due west. The fact that this was several degrees steeper than the local slope of 10 degrees was the result of foot pad no. 1, which was on the downslope side, having come to rest in a small depression.

Whereas Surveyor 1’s verniers had cut off as intended at a height of 12 feet and – as hoped – had not disturbed the surface, the fact that Surveyor 3’s verniers had kept firing through two touchdowns offered an opportunity to investigate how an intense gaseous plume affected the lunar surface material. Although the imprints of the first contact were unidentifiable owing to the highly foreshortened view of the rim of the crater and the problem with the camera made it difficult to look for erosional effects beneath the lander, the site of the second contact was conveniently positioned about

A close up of Lunar Orbiter 3 frame H-154 showing the crater in which Surveyor 3 landed, with the inferred position of the lander indicated by the arrow. (The lander was not present at the time, however.)

A contour map of the crater in which Surveyor 3 landed. The contours were drawn by interpolating between control points derived by the photographic trigonometry method. The probable vertical accuracy is +0.5 metre.

“less than 0.5 mm” which was made by tilting the camera’s mirror to view almost directly downward and taking high-resolution pictures of the surface beneath the camera.

After the success of Surveyor 1, it was decided to introduce the soil mechanics surface sampler that had been intended for later Surveyors, possibly for carriage by a rover. The original design included sensors for direct measurement of position, force and acceleration, but because the telemetry and commanding capability of the initial form of the lander could not support this complexity the position measuring system, strain gauges and accelerometers were deleted. Instead, the actions of the arm would have to be monitored by observing it using the camera, and a limited amount of data would be able to be inferred from measuring the current that the motors drew whilst in operation. The experiment comprised the articulation mechanism, the electronics compartment and their supporting structures and electrical cabling. The mechanism was mounted on the space frame immediately to the left of leg no. 2, in the position formerly occupied by the approach TV camera. The electronics compartment was at the same level and almost midway between legs no. 2 and 3. The electromechanical mechanism comprised an arm and a scoop. The arm consisted of tubular aluminium cross members which could be extended and retracted in a pantograph fashion. The scoop was a container about 13 cm long and 5 cm wide, was rigidly affixed to the arm and its door was opened and closed using an electric motor. Three electrical motors operated through drive trains to extend and retract the arm and to rotate it independently in azimuth and elevation. It was spring-loaded, extended by having an electric motor unreel a metal tape, and retracted by reeling in the tape. The arm had a maximum extension of about 1.5 metres, but was unable to access the ground immediately below its mount. It could be elevated to raise the scoop about 1 metre off the ground. On this mission the azimuth arc of the mechanism subtended 112 degrees, ranging from the left edge of pad no. 2 towards pad no. 3 – although because the legs were spaced at 120-degree intervals it stopped short of pad no. 3. In all, the sampler had an arcuate operating area of 2.2 square metres. It was controlled from Earth, but because there was no onboard memory for complex sequences it had to be operated one command at a time. The fact that it used the same radio channel as the camera meant their use had to be interleaved. The principal investigator was Ronald F. Scott, an engineer at Caltech who had worked on the Surveyor rover proposal, but the hardware had been designed and built by Hughes. Of the overall mass of 15 pounds, the mechanical assembly accounted for 8.4 pounds.

The soil mechanics surface sampler, which was also referred to as the ‘scratcher’, could manipulate the lunar surface material in a number of ways. A trench could be made by opening the door of the scoop to expose its blade, driving the scoop into the ground and retracting the arm. The scoop could hold up to 100 cubic centimetres of loose granular material, or a small rock fragment. The mechanism was designed to dig to a depth of 0.45 metre, providing that the material permitted this. An impact test involved raising the scoop and disengaging the elevation motor by releasing the clutch to allow a torsional spring to assist lunar gravity in drawing the scoop down to disturb the surface. If dropped on top of a rock, the scoop’s blade could serve as a rudimentary geological hammer. There was a 2.5 x 5.1-cm strip on the lower edge of

TV TARGET

FOOTPAD г

The configuration of the Surveyor 3 lander.

the door in order to place a flat face on the lunar surface. A static bearing test would involve placing the scoop, door closed, directly above the target and then driving the scoop down until the motor stalled, with the current providing a measure of the force applied. The arm could also be manipulated to push rocks aside in order to inspect either the underside of the rock or its imprint on the surface.

The checkout of the soil mechanics surface sampler started at 10:00 on 21 April, shortly before the end of Goldstone’s second session. After a pyrotechnic was fired to release the mechanism, JPL engineer Floyd I. Roberson commanded the arm to extend. The picture taken to confirm this showed that the arm had not advanced as far as expected. The command sequence was repeated, and the next picture showed that the arm was in the desired position. He then put it through a series of actions to verify that it could move in azimuth and elevation, checking its progress at each step by TV. This done, the arm was drawn back.

On 22 April the arm was swung to the middle of its operating area, and at 05:15 made its first bearing test of the lunar surface. The scoop was raised, the arm was swung to the right, and the scoop, door open, was driven into the surface at 09:14, after which the arm was retracted in order to scrape its first trench. Next the arm was swung left, beyond the bearing test position. After making a shallow scrape, it was raised and repositioned to make a second scrape on the same line. This time the motor stalled after just 10 cm – evidently it was more difficult to scrape an already existing trench. Meanwhile, the camera had suffered a difficulty moving in azimuth

A model of the soil mechanics surface sampler carried by Surveyor 3.

that limited its ability to support the sampling activity. Work on the second trench resumed on 23 April with a third scrape being made along the same line. Arm work was suspended on 24 and 25 April owing to the heat. Because the latitude of the site was 3 degrees, the maximum solar elevation was 87 degrees. The arm had been left at the inner end of the second trench. Having noticed what appeared to be a rock at that position, the team decided to scoop it up on 26 April, but in the process of doing so the object crumbled. The arm was swung as far right as it could traverse and the sample was deposited on the upper surface of foot pad no. 2 so that the camera could inspect the clump of fine-grained material in colour at high resolution.

On 27 April the arm swung slightly left, away from foot pad no. 2, and conducted a second and third bearing test. It then moved a little further left and scraped a third trench involving 26 retraction steps, with a wide-angle picture being taken after each step and later sequenced to produce a ‘stop-motion’ movie. On 28 April the scoop picked up a small bright object from near the most recently made trench. This was added to the material dumped onto foot pad no. 2 for inspection, but there was loose material in the scoop from the trench and on falling from the scoop this covered the white object. When the scoop was dragged across the pile to expose the object of interest, it was observed to have darkened. Next, the arm made two parallel scrapes

The operating area available to Surveyor 3’s soil mechanics surface sampler.

A picture taken by Surveyor 3 on 28 April 1967 showing the soil mechanics surface

sampler positioned between trenches no. 1 and 2.

successively offset to the left of the third trench in order to widen it, and then a bearing test was performed on its floor. On 29 April half a dozen impact tests were conducted in an arc beyond the recent trench, with the scoop being released from a variety of heights in order to vary the force of the impact. The arm was swung to the left of its operating area on 30 April and the scoop manipulated to draw a partially buried bright object onto the surface – it proved to be a fragment of hard rock, and it was photographed in colour. On 1 May two additional scrapes were made to deepen the second trench and then the scoop was dropped four times with its door open to loosen the floor prior to a final scrape. With the Sun sinking in the west the lander’s shadow masked ever more of the arm’s operating area, so on 2 May the arm ended its operations by swinging over to the right to scrape a short fourth trench alongside the broad third trench.

The results of the arm operations indicated that the material was fine-grained and had sufficient cohesion to create loose aggregations up to several centimetres in size, although such ‘clods’ readily fell apart. When the scoop was pressed on the surface for a bearing-strength test, it left a smooth imprint which had a raised ridge of lumpy

V ‘MPACT □ BEARING О CONTACT

material around the edge. This implied that although the material was compressible, it was only moderately so, and after a certain compression the vertical force tended to displace material sideways. Impact tests were performed, but the ‘spring constant’ of the torsional spring proved insufficient to determine the density in this manner. In general, the first scrape of a trench excavated to a depth of about 7.5 cm, and each successive scrape on the same line gained an additional 5 cm – with the arm having to work harder to achieve this. Bearing tests on the floor of a trench showed that the strength of the material increased significantly at a depth of several centimetres. The deepest excavation achieved was about 18 cm, which was less than half of that for which the arm’s range of operation had been designed. Nevertheless, it provided a valuable insight into the third dimension of the enigmatic fragmental debris layer. There was no indication of textural layering in the walls of the trenches. If there was any change in the grain size, this was on a scale finer than the camera’s resolution. It simply seemed that the upper few centimetres were porous, and hence compressible, whereas the essentially similar material below was more consolidated. Its cohesivity was confirmed by the fact that the trench walls did not collapse. As in the case of the material disturbed by the foot pads, the subsurface was significantly darker than the undisturbed surface – in retrospect, it was more as if the uppermost few millimetres had somehow been lightened. From the fact that no bright angular fragments were uncovered in trenching, it was speculated that while buried they became coated with dark fine-grained material and in this darkened condition were difficult to see in a trench. By implication, it seemed that after a rock had been exposed on the surface for a time it was ‘cleaned off’ by some form of weathering. There were only a few rocks within the arm’s operating area. Most were small and partially buried. The arm picked up one rock for a close examination, but it was too small for its mass to be measured. The jaws of the scoop picked up a small white rock which was about 1.2 cm in size – a task involving 90 minutes of careful remote-control manipulation. The 100-psi pressure which the scoop exerted would have crushed a weak terrestrial rock such as a siltstone or friable sandstone, but the lunar rock remained intact.

The lesson for Apollo was that whilst the lunar material was very fine-grained, it was moderately cohesive and its bearing strength increased significantly at shallow depth.

Surveyor 3’s view was confined to the 200-metre-diameter crater in which it had landed – it could not see the plain beyond. The craters in view ranged in size from 10 cm up to 25 metres. Most of the craters that were less than 3 metres in diameter were fairly shallow, and either had very subdued raised rims or were rimless. Most of the craters between 3 metres and 12 metres in diameter were subdued, but 25 per cent had raised rims and relatively steep walls. It was apparent that most of the small craters had not penetrated beneath the fragmental debris layer within the main crater, and had merely redistributed the material that was already exposed at the surface. The size-frequency distribution was similar to that for this size range seen on the maria by Rangers 7 and 8.

The angular-to-rounded fragments ranged in size from tiny grains up to blocks of about 1.5 metres. The albedo of the undisturbed surface was 8.5 (±2) per cent, and in some cases the albedo of the blocks was one-third brighter. Although the camera

operated most effectively when the Sun was high in the sky, in such illumination the absence of shadows made subtle terrain relief almost impossible to discern – but on the other hand in such illumination it was straightforward to chart the distribution of blocks. Most blocks were relatively angular, with many wedge-shaped and some even tabular. Some of the angular rocks were partially buried, but most of the well – rounded fragments were fairly deeply buried.

In addition to the sparse and random litter of blocks, there were two prominent ‘strewn fields’ of coarse blocks. One was clearly associated with a sharp raised-rim crater about 13 metres in diameter that was embedded in the northeastern rim of the main crater, some 80 metres from the lander. The other was associated with a pair of subdued craters that were located high on the southern wall. The line of sight provided a view inside the northeastern crater, revealing its interior to be full of similar blocks. Exterior to the rim, there were radial lines of blocks. The blocks associated with this crater were the largest, coarsest and most angular in the lander’s field of view. It was evident that they were ejected by the impact that created the crater, and derived from material at a depth of 2 or 3 metres beneath the rim of the main crater. Some of the blocks had almost planar faces, as though they had broken along pre-existing joints. The tabular ones displayed grooves and ridges on their narrowest sides suggestive of lamination parallel to their longest dimension, such as would be produced in flow-banded lavas. The blocks associated with the southern craters were of similar size, but were more rounded and tended to be more deeply buried. Their source was probably the larger of the two craters there, which was 15 metres in diameter. These observations suggested that large blocks associated with subdued craters tended to be more rounded than those associated with sharp raised-rim craters, and those around subdued craters were more buried than those of sharp raised-rim craters. This suggested that freshly exposed blocks were not only eroded by the rain of meteoritic material, but also tended to be reburied as material accumulated – either by the arrival of further ejecta or as a result of downslope motion of loose debris. The fact that the rounded blocks had a pitted texture whereas the angular ones did not, implied that the pitting was caused by the same process that rounded off the angular blocks.

It was also apparent that the surface on the interior of a sizeable shallow crater on a mare plain was similar to that on a relatively level area between such craters. The 200-metre crater in which Surveyor 3 landed had probably been partially filled in by the downslope motion of material on its interior walls, thickening the debris towards the centre. Loose material piled up against the upslope sides of the larger blocks was interpreted as evidence of this process. The strewn fields of coarse blocks associated with 13-15-metre-diameter craters on or near the rim of the main crater implied that the fragmental debris layer was about 2 metres thick there. In contrast, the fact that a 20-metre crater near the centre of the main crater had not excavated blocks served to confirm that the layer there had been thickened. When the main crater was created, its floor would have been several tens of metres deeper and its rim several metres higher and sharper than it is today. By the ‘hinge-flap’ effect of an impact, the debris that formed the rim would have been excavated from the deepest point. In effect, a blocky crater on the rim of a larger crater serves as a ‘drill hole’. The crater on the

A northward-looking section of a panorama taken by Surveyor 3. The outline shows the area covered by the next illustration. (Courtesy of Philip J. Stooke, adapted from International Atlas of Lunar Exploration, 2007)

A portion of the previous illustration featuring a strewn field of boulders around a small crater on the northeastern rim of the crater in which Surveyor 3 landed. (Courtesy of Philip J. Stooke, adapted from International Atlas of Lunar Exploration, 2007)

northeastern rim would offer visiting astronauts an opportunity to recover material excavated from beneath the fragmental debris layer.2

After a detailed analysis of the Surveyor 3 imagery, Gene Shoemaker introduced the term ‘regolith’ to lunar science. This was familiar to terrestrial geologists as the collective name for the rock wastes of whatever origin and however transported that rest on bedrock and nearly everywhere form the surface of the land. On Earth, there are many erosional processes and the regolith includes volcanic ash, glacial drift, alluvial deposits, eolian deposits and soils rich in humus. On the Moon, the primary erosional process was meteoritic impact. Harold Urey had introduced ‘gardening’ for the manner in which the poorly sorted fragmental debris layer was turned over by impacts. The pictures from the two Oceanus Procellarum landing sites hinted that the thickness of the layer increased with age. To start with, the surface would have been bare rock. Any significant impact would have been capable of breaking up and scattering the material. This ejecta would have been progressively eroded by the rain of smaller projectiles. Over time, the layer of debris would have thickened, requiring ever larger impacts to reach the substrate. An important aspect of this process was that it would yield a continuous distribution of fragment sizes, which was expressed by saying that the lunar regolith was seriate.

One scientific task for Surveyor 3 was to monitor the Moon’s passage through the Earth’s shadow. With the Moon at ‘full’ phase and the Earth masking the Sun, this was a lunar eclipse to a terrestrial observer and a solar eclipse to the lander. It was the first opportunity to observe the thermal effects of such an event from the lunar surface and assess inferences drawn from telescopic studies. In particular, Surveyor science team member John M. Saari had been involved in infrared scanning of the Moon’s disk during the lunar eclipse of 19 December 1964, the data from which was processed into isothermal contours that indicated the presence of many ‘anomalies’, mostly associated with craters, where the heat that had been absorbed while the Sun was shining at lunar noon was radiated again at the onset of the eclipse. In addition to monitoring the temperature, Surveyor 3 gave the scientists a bonus: the mirror of its TV camera had the same 35-degree elevation limit as previously, but because the lander was west of the meridian and inclined due west at an angle of 12 degrees by virtue of having settled on a slope, the field of view of the wide-angle frame was just able to include Earth, east of the zenith. Optical observations of the eclipse would yield the first direct measurement of the distribution of the refracted sunlight which weakly illuminates the lunar disk at such times.

Fortunately, the eclipse on 24 April occurred during a period when the Moon was still just above Goldstone’s horizon. A total of 20 images were taken in two sets: the first at 11:24 and the second 37 minutes later. They were taken at two iris apertures, and with several exposures for each of the three colour filters. In the first set, an arc along the northwestern limb of Earth refracted light that varied greatly in brightness, and with a fainter glow at each end containing bright ‘beads’. In the second set, the

And in fact Apollo 12 would do so at precisely this spot.

• INFRARED ANOMALIES

The locations of lunar transient events reported over the years by various observers and infrared ‘hot spot’ anomalies measured during a lunar eclipse on 19 December 1964. (Courtesy of John M. Saari and R. W. Shortfall, Isothermal and Isophotic Atlas of the Moon, NASA, 1967)

brightest refraction had migrated to the northeastern limb. To assess the distribution of cloud on the limb, the geographic coordinates of the ‘beads’ were later calculated and compared to pictures taken by the ESSA 3 meteorological satellite in low polar orbit on the day prior to the eclipse. In some areas cloud in the troposphere occulted some of the refracted sunlight, but the bright ‘beads’ occurred where sunlight passed through regions free of cloud. Of course, the refracted sunlight made it impossible to view the much fainter solar corona.[34]

The thermal properties of the lunar surface inferred from the lander’s temperature data differed from inferences made from telescopic studies, in that the in-situ data showed a higher thermal inertia. However, the data was provided by sensors in place to monitor the thermally controlled compartments, not by instruments specifically designed to study the thermal properties of the lunar surface, and therefore was too crude to draw definitive conclusions.

The plan had called for attempting a ‘liftoff and translation’ manoeuvre by firing the verniers, but this was ruled out by thermal factors. The decision rested upon the temperatures of the thrust chambers of the engines, the flight control electronics, the helium tank, the shock absorbers and the roll control actuator on vernier no. 1 – all of which depended upon solar heating and shadowing in the orientation in which the vehicle came to rest. The key issue was the temperatures of the engines. Irrespective of the orientation, by the time the elevation of the Sun reached about 35 degrees one or other of the engines was sure to exceed its permitted pre-ignition temperature of 105°C. Hence, any attempt to lift off had to be made either early in the morning or late in the afternoon. For Surveyor 3, the thermal situation was complicated by the fact that the lander was on a slope, which significantly altered the manner in which shadows were cast. To preserve the option of this experiment, the helium tank had not been vented. Also, given that at no time during the protracted landing had the forces on the shock absorbers imparted even half the load endured by Surveyor 1, it had been decided not to lock the legs. Whilst the helium was significantly depleted, as the tank absorbed solar heat its pressure increased to 2,735 psia.[35] By the time of the eclipse, however, it had been decided not to attempt to fire the verniers. The legs were monitored to determine whether the rapid decline in temperature at the onset of the eclipse prompted the shock absorbers to leak, but they retained their integrity. At 20:36 on 24 April, the helium tank was finally vented.

Surveyor 3 had two flat beryllium mirrors situated to enhance the camera’s view of the underside of the vehicle. That is, the camera was between legs no. 2 and 3 and the mirrors were affixed to leg no. 1. One mirror was 35 x 22 cm and gave a view of the lower portion of crushable block no. 3 and the area beneath vernier no. 3. The other mirror was 9 x 33 cm and viewed the area beneath vernier no. 2. The fact that the verniers were cut off at a height of only 3 feet suggested there might be signs of surface erosion, but since the vertical velocity at the third contact was only 1.5 ft/sec the crushable blocks probably did not strike the surface. Unfortunately, the hopes of viewing beneath the lander were foiled by the fact that when the Sun was low in the sky the pictures were ‘washed out’ by the glare from the coating on the main mirror of the camera, and when the Sun was high in the sky the area of interest was in the lander’s shadow! It had been hoped to fire the downward-pointing cold-gas thruster on leg no. 2 to follow up on Surveyor 1’s surface erosion experiment, but this time obtaining good ‘before’ and ‘after’ pictures of the test area. However, pictures taken when the Sun was low in the east were washed out by glare, pictures taken when the Sun was high lacked the shadows required to highlight the minute changes likely to result from such a weak thrust, and in the late afternoon the area was in the lander’s shadow – so the test had to be cancelled.

Between 10:29 and 11:06 on 30 April, Surveyor 3 snapped wide-angle pictures of Earth illuminated as a crescent with the dawn terminator running the length of South America. These were the first colour pictures of Earth taken from deep space.[36] The filters had been revised to provide an improved spectral match to standard colorimetry functions.

Following sunset at 18:38 on 3 May Surveyor 3 monitored the rate at which the temperature fell, and at 00:02 on 4 May was commanded to hibernate.

In total, the camera took 6,326 pictures. Owing to the glare from contamination of the main mirror, usable images could be obtained only over a limited azimuth range during the early morning and late afternoon. This glare, combined with the difficulties in moving the mirror, made it impossible to obtain all of the systematic surveys of the landscape which had been planned. About 8 per cent of the pictures were taken at wide-angle to provide panoramas at specific illumination phases. The glare impaired detailed photometry, but the colorimetry confirmed that the surface was essentially grey. The glare precluded photographing the stars for use as celestial references to precisely determine the orientation of the camera, and hence the true orientation of the lander, but on one occasion it did manage to photograph Venus, which helped to some extent.

Although Surveyor 3 was unable to view the plain surrounding the crater in which it landed, scientists were delighted to have the opportunity to survey the interior of a medium-sized crater on a mare! In effect, therefore, its observations complemented those by Surveyor 1 of the open plain. In general, the character of the lunar surface material appeared to be similar at the two sites. The soil mechanics surface sampler was active for a total of 18.3 hours. It executed 5,879 commands, during which it made seven bearing-strength tests, thirteen impact tests and four trenches to provide data on the strength, texture and structure of the lunar material to a depth of 18 cm. In particular, it found that the bearing strength of the material increased with depth, even although there was no discernible change in the grain size – it was just that the uppermost few centimetres were more porous. Although sequences of commands to enable the sampler to perform complex operations had been stored on magnetic tape for step-by-step uplinking, for much of the time it was actually operated in real-time and monitored by TV.

Surveyor 3 evidently succumbed to the chill of the lunar night, because attempts to reactivate it after sunrise were unsuccessful.

RANGERS FOR APOLLO

When on 25 May 1961 President Kennedy challenged his nation to land a man on the Moon before the decade was out, the sky scientists were unimpressed but the geologists were delighted.

On 8 June Hugh Dryden advised the Senate Committee on Aeronautics and Space Sciences that NASA intended to make use of automated spacecraft to strengthen the manned lunar program. In particular, it was essential to find out whether the surface would support the weight of the Apollo lander. As Dryden put it, ‘‘We want to know something about the character of the surface on which the landing is to be made, and obtain as much information as we can before man actually gets there.’’ Following up, Abe Silverstein provided some details. For a start, Ranger would be extended by four Block III missions. Congress authorised the funding for these missions several weeks later.

Clifford Cummings, JPL’s Lunar Program Director, visited NASA on 21 June and told Edgar Cortright and Oran Nicks, the two managers in Silverstein’s office who were responsible for Ranger, that the greatest single contribution this project could make to Apollo would be to provide high-resolution imagery to enable the nature of the lunar surface to be characterised to provide the information needed to design the landing gear of the Apollo lander. For this, the Block III would replace the surface package subassembly with a TV system that was more sophisticated than that made for the Block II. In the interim, some insight would be provided by the Block II radar altimeter and the accelerometers of the surface capsule as this impacted and rolled to a halt.

JPL recommended that the contract to develop the high-resolution TV system go to the same company that supplied the camera for the Block II, and this was agreed.

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The shuttering sequence of the six cameras of the Block III Ranger spacecraft’s high – resolution TV system.

On 5 July 1961 JPL discussed the design of the system with the Radio Corporation of America, and it was decided to use a shutter (which was not a standard feature on a continuous-scan TV system) to define a ‘frame’ on a vidicon tube. The contract was signed on 25 August. Responsibility for the design, fabrication and testing of the system was delegated to the company. Harris Schurmeier’s Systems Division would monitor the work. On 31 August, Cummings appointed Allen E. Wolfe as the Ranger Spacecraft Systems Manager to assist James Burke with the increased work. Wolfe had replaced Gordon Kautz as Project Engineer in the Systems Division when Kautz was made Burke’s deputy. Wolfe’s first responsibility would be to steer the remaining Block II spacecraft through all phases of assembly and testing, and then supervise the development of the Block III.

The design of the high-resolution TV subsystem was finished in September 1961. It had three major assemblies: a tower superstructure incorporating a thermal shield to stand on the top of the hexagonal bus; a central box to house the main electronics; and, above, a battery of six cameras and their individual electronic systems. It used two types of camera. The ‘A’ type had a lens with an aperture ratio of f/1 and a focal length of 25 mm. The ‘B’ type had an f/2 lens with a focal length of 75 mm. There were two ‘A’ cameras and four ‘B’ cameras. The vidicons were all the same, but the entire 11-mm square image would be used for the full (F) frame and only the central 3-mm square for the partial (P) frame. One ‘A’ and one ‘B’ camera would operate a 5.12-second cycle in which the shutter fired to expose its vidicon and this was read out over an interval of 2.56 seconds, then erased over the next 2.56 seconds. They were to operate out of phase so that a frame was taken every 2.56 seconds. The other cameras would require 0.2 second to fire the shutter and perform the readout, and 0.6 second to erase. The faster cycle time for these cameras was because a smaller

area was to be scanned. They were to be cycled to take a frame every 0.2 second, in the hope that one camera would be able to provide a close-up picture just prior to impact. The cameras were mounted at angles designed to provide overlap to enable the relationship of one frame to be related to those preceding and following. The TV subsystem would have its own battery, independent of the bus, and a pair of 60-watt transmitters. Unlike the Block II, whose flow of pictures would conclude when the separation of the surface package caused the high-gain antenna to lose its lock on Earth, the Block III would continue to send pictures until it hit the surface. In all, the high-resolution TV subsystem would be 160 kg.6

As in the case of the Block I, the low-gain antenna would be in a fixed position at the top of the tower. The designers of the Block III had the luxury of being able to exploit the full payload capacity of the Atlas-Agena B, and this allowed some degree of redundancy in the basic systems.

On 19 September 1961 NASA announced that the Block IIIs were to be launched in January, April, May and August 1963 – certainly they were to be over before the first soft-landing Surveyor, which was expected in 1964.

THE GEMINI LEGACY

When NASA decided in 1962 that Apollo would use the lunar orbit rendezvous mission mode, many people doubted that orbital rendezvous would be feasible. The primary objective of the Gemini program was to explore the issues. The ten manned missions flown between March 1965 and November 1966 not only established that rendezvous and docking was feasible, by testing a variety of techniques it gave the Apollo planners the flexibility of options. This inspired a workaround to the fact that the combined Apollo vehicles exceeded the payload capacity of the Saturn IB, in the form of the dual AS-207/208 rendezvous. Gemini also showed that astronauts could endure the space environment for longer than any Apollo mission would require. Given that the longest American space flight at the time of President Kennedy’s commitment to Apollo was Al Shepard’s 15-minute suborbital arc, on which he was weightless for only a couple of minutes, this was welcome news. The fuel cells that were to power the Apollo spacecraft were tested on Gemini, as were a fully inertial reference platform for guidance and navigation, a spaceborne radar, a state-of-the-art digital computer to process the radar data for rendezvous, and bipropellant ablative thrusters. Gemini established that a spacecraft could be steered through re-entry for recovery at a specific location. This increased confidence in the ‘atmospheric skip’ manoeuvre that was to be used by an Apollo spacecraft returning from the Moon. By enabling astronauts to learn how to operate outside a spacecraft, Gemini inspired a rescue option for the crew of an Apollo lunar module that was unable to dock with its mothership. And, of course, by training a cadre astronauts and flight controllers Gemini allowed Apollo to get off to a running start.

As Robert Gilruth, Director of the Manned Spacecraft Center, observed: ‘‘In order to go to the Moon, we had to learn how to operate in space. We had to learn how to manoeuvre with precision to rendezvous and to dock; to work outside in the hard vacuum of space; to endure long-duration in the weightless environment; and to learn how to make precise landings from orbital flight – that is where the Gemini program came in.’’

Author’s preface

For millennia human beings have peered at the Moon in the sky and wondered what it might be. Within months of its establishment on 1 October 1958, the National Aeronautics and Space Administration set out to develop a program of robotic lunar exploration. In 1961 President John F. Kennedy raised the stakes by challenging his nation to land a man on the Moon within that decade. The resulting Apollo program dominated the agency’s activities throughout the 1960s and into the early 1970s.

It is impractical to cover all the strands of this effort in a single volume in equal detail. Nor can any given strand be properly appreciated in isolation. My approach is therefore to write a series of books, each of which applies a magnifying glass to a certain number of strands and glosses over others. This book focuses on what was known about the Moon at the dawn of the space age and details the robotic projects that paved the way for the first Apollo lunar landing, in particular the Surveyors that soft-landed to investigate the physical and chemical nature of the lunar surface and the Lunar Orbiters sent to reconnoitre possible landing sites.

As such, this book complements: Apollo – The Definitive Sourcebook, which was compiled with Richard W. Orloff and supplements an account of how the Apollo program was organised with the minutiae of each flight; How NASA Learned to Fly in Space – An Exciting Account of the Gemini Missions, which explains the key contribution that the Gemini crews made to the success of Apollo; and The First Men on the Moon – The Story of Apollo 11, which covers that mission from start to finish. In Exploring the Moon – The Apollo Expeditions, which I recently reissued in enlarged format, I detailed what the astronauts of each mission did whilst on the lunar surface. It also complements the excellent To a Rocky Moon – A Geologist’s History of Lunar Exploration by Donald E. Wilhelms, and the International Atlas of Lunar Exploration by Philip J. Stooke.

I used the mission reports as my primary source of information – there are many thousands of pages available on the NASA Technical Report Server. Millions of dollars were spent developing and flying the vehicles used to take close-up pictures of the Moon and, like the mission reports, until recently they remained in archives. I have assembled some of the contiguous photographic sequences taken by the Lunar Orbiters to illustrate the process by which the site for the first Apollo landing was selected. To my knowledge, they have never previously been made available to the public in this form. I have also freely intermixed units of measure, largely following the choice of the appropriate mission reports. Unless stated otherwise, all times are GMT in 24-hour format. Launch, parking orbit, midcourse and terminal phase times are usually specified to the nearest second, but for a Surveyor spacecraft’s powered descent the event times are specified to several decimal places.

In the 1960s NASA was a young and aggressive agency which embodied the ‘can do’ spirit of America at that time in tackling audacious engineering challenges with a tremendous sense of urgency – motivated by the desire to be the first to explore a new world. This is an account of a strand of that story that is often reduced to a few paragraphs in popular histories.

David M. Harland Kelvinbridge, Glasgow January 2009

MISSION ACCOMPLISHED

The three successful Rangers satisfied the objective set for the Block III series in terms of supporting Apollo. The maria proved to be cratered on all scales, but with a smoothly undulating surface of generally shallow slopes. And the presence of large blocks of rock lying on the surface suggested sufficient bearing strength to support a lander. In addition, radio tracking had enabled the estimate of the mass of the Moon to be much improved. It also established the axis that is aligned towards Earth to be about 1 km longer, with the centre of mass being offset several kilometres from the geometric centre in a direction away from Earth.

When some 200 scientists gathered at the Goddard Space Flight Center in April 1965 to discuss the combined results of the Ranger project, Harold Urey and Gerard Kuiper still disagreed about whether the Moon was thermally differentiated. Thomas Gold insightfully noted that the pictures represented a mirror in which each person saw evidence to support his own hypothesis.

One lesson of Ranger was that lunar geological units were so severely blurred by impact ‘tilling’ at the fine scale that in undertaking photogeological mapping it was better to use a medium scale of 1:1,000,000, as was used by the Air Force Chart and Information Center in St Louis for its Lunar Astronautical Chart series.

Ranger had provided a close look at several sites, but what was required next was for an orbiter to provide a broader view at better-than-telescopic resolution and for a soft-lander to provide ‘ground truth’.

SATELLITE SHOCK

The first International Polar Year was held between 1882 and 1883 to coordinate meteorological, magnetic and auroral studies. The eruption of Krakatoa in

Indonesia on 20 May 1883 had a temporary but significant effect on the atmosphere. A second International Polar Year was held 50 years later. In 1950 the International Council of Scientific Unions proposed to exploit the technologies developed in the years since the Second World War to undertake geophysical research on a global basis to study the solar-terrestrial relationship. In early 1952 it was agreed that this International Geophysical Year would run from July 1957 to December 1958, a period which was expected to coincide with the time of maximum solar activity in the 11-year cycle of sunspots. In early 1954 the National Security Council said the US “should make a major effort during the International Geophysical Year”, and directed the Pentagon to provide “whatever support was necessary to place scientists and their instruments in remote locations” to make observations.

In August 1953 physicist Fred Singer outlined to the International Congress of Astronautics a 45-kg satellite for MOUSE (Minimum Orbital Unmanned Scientific Experiment). He spent the next year promoting it. In October 1954 he canvassed the US delegation to the meeting in Rome, Italy, of the International Geophysical Year’s Steering Committee, and as a result a resolution was passed which encouraged participants to investigate the possibility of launching a satellite as the highlight of the program.

In November 1954 Charles Wilson told journalists he did not care if the Soviets were first to put up a satellite. Despite the National Security Council directive for “a major effort’’ in support of the International Geophysical Year, it was not until 1955 that Wilson endorsed a satellite. In July 1955 Eisenhower announced that the US would put up a satellite for the International Geophysical Year. Eisenhower saw it as a one-off scientific venture. He assigned to the Pentagon the decision for how it should be achieved. There was intense rivalry between the services, because such a spectacle would boost that service’s claim to be assigned a greater responsibility for long-range missiles. Shortly before Eisenhower’s announcement, Donald Quarles, Chief of Research and Development at the Pentagon, had set up a committee chaired by Homer Joe Stewart, a physicist at the University of California at Los Angeles, to review the capabilities of the services. The National Security Council had stipulated that the satellite must not impede the development of the Atlas missile, which was only now beginning to gear up as a ‘crash’ national program. This ruled out the Air Force.

The Army proposed Project Orbiter, claiming that if the Redstone missile, which was an improved V-2, were to be fitted with three upper stages, a satellite would be able to be launched by January 1957, which was before the start of the International Geophysical Year. The Navy had Project Vanguard, in which an improved form of the Viking ‘sounding’ rocket introduced in 1949 for stratospheric research would be augmented with two upper stages. Part of the rationale for the Stewart Committee selecting Vanguard was the perceived greater reliability of requiring only two upper stages, instead of three. In addition, the Committee was impressed by the in-line configuration of the Vanguard stages, as opposed to clustering small solid rockets to form the upper stages of the Redstone launch vehicle. Nevertheless, Stewart himself had supported the Army’s proposal. One factor was that whereas the Redstone was a weapon and was classified, the Viking was not classified. Another rationale, added later, was that it would be better to use a ‘civilian’ rocket for this scientific project. The Committee was not concerned that Vanguard would not deliver as early as the Army claimed for Orbiter – it was simply presumed that the first satellite would be American, and provided that it was launched within the period of the International Geophysical Year it would serve its purpose. On 9 September 1955 the Pentagon endorsed the Committee’s recommendation. The spherical Vanguard satellite would weigh about 1.5 kg, and would transmit a radio signal that would allow the study of electrons in the ionosphere and thus make a unique contribution to the International Geophysical Year.

Since the services were only loosely controlled by the Department of Defense, the Army set out to contest the decision, emphasising that the Redstone could launch a satellite without impeding military work. When on the Stewart Committee, Clifford C. Furnas of Buffalo University had sided with the Army. Now at the Pentagon, he advised the Army to have its missile ready as a backup in case Vanguard faltered.

On 1 February 1956 the Army Ballistic Missile Agency was established at the Redstone Arsenal, Major General John B. Medaris commanding. It was to develop an intermediate-range ballistic missile named Jupiter. As the warhead would enter the atmosphere at a faster speed and be subjected to greater heating than that of the short-range Redstone, it was decided to test the new re-entry vehicle by firing it on a ‘stretched’ Redstone equipped with two upper stages made by clustering small solid rockets. The fact that this ‘Jupiter-C’ would enable the Army to develop and test a vehicle capable of launching a satellite was, of course, entirely coincidental! When the first test flight on 20 September 1956 reached a peak altitude of 1,000 km and flew 4,800 km down the Air Force’s Eastern Test Range from Cape Canaveral, the Pentagon directed Medaris to personally guarantee that Wernher von Braun did not inadvertently place anything into orbit! One criticism of Vanguard was that although its first stage was based on the Viking, the project really involved developing a new integrated vehicle in a period of only 2 years. With Vanguard running late, Medaris sought permission to launch a satellite, but the Secretary of the Army refused – in fact, the Army Ballistic Missile Agency was ordered to destroy the remaining solid rockets obtained for the upper stages. In response, Medaris decided to leave them in storage to ‘assess’ their shelf life!

In public, Eisenhower maintained that launching a satellite was a one-off venture for the International Geophysical Year. In fact, this was a cunning ruse, because the aim was to use Vanguard to set the precedent of a US satellite passing over foreign territory, and thus preclude a legal challenge when the US began to send up satellites for military functions such as reconnaissance.

Soon after the US announced that it would launch a satellite for the International Geophysical Year, the Soviet Union said it intended to do the same. In mid-1957 the Soviet magazine Radio told its readers how to go about ‘listening’ to this satellite. In late August the TASS news agency announced the successful test flight of a ‘‘super long range’’ missile which was capable of striking ‘‘any part of the world’’. When a Soviet delegate at an International Geophysical Year meeting in Washington in late September was asked whether the promised satellite was imminent, he replied: ‘‘We won’t cackle until we’ve laid our egg.’’ In other words, wait and see!

On 4 October the 84-kg Sputnik was placed into an orbit which ranged in altitude between 220 and 950 km and transmitted its incessant ‘beep, beep, beep’ signal.

The news caused a world-wide sensation, but Eisenhower was not concerned. At a press conference on 9 October he dismissed Sputnik as a ‘‘small ball in the air’’ that ‘‘does not raise my apprehensions, not one iota’’. On the other hand, the mass of the satellite showed the capability of the Soviet intercontinental-range ballistic missile, and Eisenhower ordered an end to the administrative difficulties that were impeding funding for the American missile programs.

Lyndon Baines Johnson was not only the senior Democratic senator for Texas, as the Democratic leader in the Senate he essentially controlled majority congressional support for the legislative program: put simply, without his backing, the Republican administration was ineffective. Johnson saw Sputnik in terms of national security – the satellite could well have been an orbital bomb, waiting to be instructed to fall on an American city. He ordered a Congressional investigation into the state of national security preparedness. As a result, the public became aware that there was a ‘‘missile gap’’; and, almost overnight, ‘space’ was transformed from a fantasy into something that the US should be leading, since otherwise national prestige would be damaged.1

After the launch on 3 November of a heavier Sputnik with a canine passenger, Eisenhower demanded an increase in the pace of Vanguard, which was in trouble, and also authorised the Army Ballistic Missile Agency to prepare a Jupiter-C in case Vanguard should fail. Medaris had the solid rockets for the upper stages retrieved from storage and let von Braun loose.

On 6 December 1957 Vanguard ignited, lifted a few centimetres off the pad, then collapsed back and exploded in a fireball. On 31 January 1958 the Army launched a satellite using essentially the same vehicle configuration as the Stewart Committee had rejected. On being asked for permission to inform Washington of the success, Medaris reputedly said: ‘‘Not yet, let them sweat a little.’’ The satellite, Explorer 1, was integrated into the solid rocket of the final stage and inserted into an orbit which ranged between 360 and 2,550 km. The Geiger-Mueller tube it carried was supplied by James van Allen, a physicist at the University of Iowa, and detected the presence of charged-particle radiation trapped within the Earth’s magnetic field, far above the atmosphere.

With the development of nuclear-armed intercontinental-range ballistic missiles threatening to make manned strategic bombers obsolete, the Air Force reacted to the prospect of its strike force becoming ‘silo rats’ by claiming that it needed to develop a manned space flight capability. Its Ballistic Missile Division, headed by General Bernard Schriever, devised Man In Space Soonest. This envisaged a progression of steps that would result in an Air Force officer landing on the Moon in 1965. When this was submitted to the Pentagon in March 1958 the response was lukewarm – in

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On 6 December 1957 the Vanguard rocket explodes within seconds of ignition.

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Details of the Explorer 1 satellite, with the instrument section integrated with the solid – rocket final stage.

part owing to the estimated cost of $1.5 billion, but also due to the absence of a clear military necessity. In fact, the proposal was an example of what would be referred to in today’s parlance as a demonstration of ‘the vision thing’.

No sooner had the Army developed its Jupiter intermediate-range ballistic missile than the Pentagon assigned operational control of all land-based missiles with ranges exceeding 320 km to the Air Force, thus limiting the Army to ‘battlefield’ missiles. In fact, the Air Force had no use for the Jupiter, since it had just developed its own Thor intermediate-range ballistic missile.

The only prospect for the Army Ballistic Missile Agency was therefore to develop powerful launch vehicles for satellites. On 19 December 1957 the Army proposed the National Integrated Missile and Space Vehicle Development Program. Like the Air Force, the Army saw itself as the obvious service to explore space. In 1959 it proposed Project Horizon to achieve a manned lunar landing in 1965, but this was received no more enthusiastically than the rival Man In Space Soonest.

OUTCOME UNKNOWN

Surveyor 4 was similar to Surveyor 3, with a soil mechanics surface sampler, but it also had a magnet on foot pad no. 2 to investigate whether there were magnetic particles in the surface material. It was to employ the last of the single-burn Centaur stages and fly essentially the same direct ascent trajectory as Surveyor 2 to aim for Sinus Medii. It lifted off from Pad 36A at 11:53:29 GMT on 14 July 1967. Both the Atlas and the Centaur performed satisfactorily, with translunar injection at 12:04:57. The spacecraft deployed its legs and omni-directional antenna booms, and, on being released, cancelled the inherited rates, acquired the Sun and deployed its solar panel. When commanded to acquire Canopus some 6 hours later, it did so without incident. It was decided to postpone the midcourse manoeuvre from the nominal 15 hours into the flight, and make it 24 hours later. The 10.5-second burn at 02:30:04 on 16 July imparted a change in velocity of 33.78 ft/sec to trim the initial divergence of 175 km from the centre of the 60-km-diameter target circle to a mere 8.5 km.

The pre-retro manoeuvre in which the spacecraft departed from its cruise attitude involved starting a roll of + 80.4 degrees at 01:24:44 on 17 July and a yaw of + 92.7 degrees at 01:29:34. This aligned the thrust axis with the velocity vector as that would be at retro ignition. The roll of -25.3 degrees at 01:35:05 was to optimise the illumination for post-landing imaging of crushable block no. 3. A landing on the prime meridian involved making an approach at 31.5 degrees to local vertical, as opposed to 23.6 degrees for Surveyor 3 at 23°W and 6.1 degrees for Surveyor 1 at 43°W. This would require a greater gravity turn in the vernier phase to force the trajectory to vertical. If successful, this mission would ‘open the door’ to sending future landers to targets in the eastern portion of the Apollo zone.

The altitude marking radar was enabled at 02:00:17, and issued its 100-km slant – range mark at 02:01:56.080. The programmed delay to the initiation of the braking manoeuvre was 2.725 seconds. The verniers ignited precisely on time, and the retro – rocket 1.1 seconds later – at which time the vehicle was travelling at 8,606 ft/sec. With everything apparently normal, the downlink fell silent at 02:02:41.018, when 40.9 seconds into the predicted 42.5-second duration of the retro-rocket’s burn. The vehicle was at an altitude of 49,420 feet, travelling at 1,092 ft/sec, and nominally 2 minutes

Outcome unknown 315

Details of the Surveyor spacecraft’s solid-fuel retro-rocket.

20 seconds from landing. The Deep Space Network was unable to re-establish contact with it.

The engineering team that studied the telemetry realised that whatever the fault was, it had cut the downlink within an interval of 0.25 millisecond without showing any indication in the preceding telemetry. The cause of the failure was not apparent. The only noteworthy unusual development was a slight modulation in the thrust of verniers no. 1 and 2, but it was not evident how this could have been relevant. The investigation listed four possible causes, without rating them in order of likelihood: (1) the breakage of a critical power lead in a wiring harness, or the failure of an

electrical connector, or the failure of a solder joint; (2) damage to the spacecraft’s circuitry from the rupture of the casing of the retro-rocket; (3) a transmitter failure; or (4) damage to the spacecraft’s circuitry caused by the rupture of a pressure vessel such as a shock absorber or a helium tank, nitrogen tank or vernier propellant tank. Since there was judged to be a “relatively low probability’’ of any of these failure modes recurring, no hardware changes were ordered.

Interestingly, if Surveyor 4’s problem was simply a transmitter failure, then it is highly likely that the vehicle landed safely.

APOLLO UNDERWAY

On 24 September 1961 NASA announced that the Manned Spacecraft Center to be built near Houston, Texas, would supersede the Space Task Group. It would not only design, develop, evaluate and test manned spacecraft, but also train astronauts and manage mission operations. Robert R. Gilruth, head of the Space Task Group, was made Director of this new centre.

On 1 November, NASA restructured its headquarters. As part of this review, the offices of Space Flight Programs and Launch Vehicle Programs were wrapped up, and new program offices were created for Manned Space Flight, Space Sciences, and Applications. This raised Manned Space Flight to office status, as opposed to a subdivision of Space Flight Programs. The effect was to put the administration of all the agency’s activities (some of which were aeronautical) on a par with the Office of Manned Space Flight, although that office had fully three-quarters of the budget. In effect, James Webb had gathered the power of decision-making into headquarters, since the directors of all the ‘offices’ and ‘centres’ would report to Robert Seamans, the Associate Administrator who, as the agency’s ‘general manager’, would have budgetary control.

The obvious candidates to be Director of the Office of Manned Space Flight were Abe Silverstein and Wernher von Braun, but because their relationship was stormy Webb had sought an outsider, and on 21 September hired Dyer Brainerd Holmes. As general manager of the Major Defense Systems Division of the Radio Corporation

Specifically, the cameras were designated Fa (25-mm), Fb (76-mm), P1/P2 (76-mm) and P3/P4 (25-mm).

 

Detail of the Block III Ranger spacecraft.

 

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On 20 February 1962 an Atlas rocket lifts off with a Mercury capsule containing John H. Glenn for an orbital mission.

 

of America, Holmes had built the Ballistic Missile Early Warning System on time and on budget, which was no mean feat.7 Silverstein returned to the Lewis Research Center, this time as its Director.

Homer Newell was promoted from Silverstein’s deputy to become Director of the Office of Space Sciences. Edgar Cortright became Newell’s deputy, and Oran Nicks superseded Cortright as Director of the Lunar and Planetary Programs Division. As one of his first acts, Nicks established individual offices in the Lunar and Planetary Programs Division for Ranger and Surveyor, and also for the Mariner interplanetary program. For Ranger, William Cunningham was Program Chief, Walter Jakobow – ski was Program Engineer and Charles Sonett served in an interim capacity as Program Scientist. James Burke at JPL was delighted with this structure, because it integrated engineering and science in a single program office and greatly simplified his relationship with NASA headquarters.

Holmes promptly assigned Joseph F. Shea, a systems engineer who had run the development of the inertial guidance system for the Titan intercontinental-range ballistic missile, to resolve the protracted debate about how Apollo would fly to the Moon – the ‘mission mode’ issue.

On 28 November, NASA announced that North American Aviation of Downey, California, had been awarded the contract to develop the Apollo spacecraft. On 21 December, Holmes set up the Manned Space Flight Management Council. Drawing on senior managers at headquarters and the field centres, this would set policy for manned space planning. At its first meeting, the Council decided on a launch vehicle which would become known as the Saturn V. A single launch would be capable of dispatching an Apollo circumlunar mission. It might even be possible to undertake a lunar landing with a single launch. A landing mission involving Earth orbit rendezvous could certainly be done using just two launches.

On 20 February 1962, America finally inserted a man into orbit, with John Glenn riding an Atlas missile to circle the globe three times. On 7 June NASA decided on lunar orbit rendezvous as the mode for Apollo. On 7 November, it announced that the Grumman Aircraft Engineering Corporation of Bethpage, New York, had been awarded the contract to develop the Apollo lunar module.

By the end of 1962, therefore, NASA had taken all the key decisions that defined how it would address Kennedy’s challenge.

BMEWS used large radar stations in Alaska, Greenland and England to provide the US with the famous ‘‘fifteen minute’’ warning of a Soviet ICBM strike over the north pole.

SETBACK AND RECOVERY

On 26 August 1966 the command module of CSM-012 arrived at the Cape in a container prominently labelled ‘Apollo One’.

North American Aviation was to have shipped it several weeks earlier, but the failure of a glycol pump in the environmental control system had led to the exchange of this unit with its CSM-014 counterpart. Although the customer acceptance review identified other ‘‘eleventh-hour problems’’ associated with the environmental control system, NASA had taken receipt.

The Office of Manned Space Flight held the AS-204 design certification review on 7 October, and declared that the launch vehicle and the spacecraft ‘‘conformed to design requirements’’ and would be flightworthy once a number of deficiencies had been overcome. Sam Phillips issued a list of these deficiencies to Lee B. James at the Marshall Space Flight Center, Joseph Shea at the Manned Spacecraft Center, and John G. Shinkle, Apollo Program Manager at the Kennedy Space Center, requiring speedy compliance. On 11 October Phillips was informed by Carroll Bolender of a report he had received the previous day from Shinkle detailing increasing delays in the preparation of CSM-012. When the spacecraft was delivered, 164 ‘engineering orders’ had been identified as ‘open work’ – despite the fact that the accompanying data package had listed only 126 such items. By 24 September the list had grown to 377, and Shinkle ventured that about 150 of the 213 additional orders ought to have been identifiable by the manufacturer prior to the customer acceptance review. The issues included the environmental control system (which had failed again), problems with the reaction control system, a leak in the service propulsion system, and even design deficiencies with the couches that had obliged the company to send engineers to the Cape. On 12 October Phillips wrote to Mark E. Bradley, Vice President of the Garrett Group, whose AiResearch Division had supplied the environmental control system under subcontract to North American Aviation, explaining that its reliability threatened a “major delay” to the AS-204 mission. To Phillips, the problems seemed “to lie in two categories: those arising from inadequate development testing, and those related to poor workmanship”. A replacement was delivered on 2 November, and testing resumed as soon as it was in place. However, the unit malfunctioned and had to be returned to the company.

On 25 October the propellant tanks of the service module for CSM-017, assigned to AS-501, failed catastrophically in a test at North American Aviation. The normal operating pressure was 175 psi, but it had failed after 100 minutes at the maximum requirement of 240 psi. The test had been ordered following the discovery of cracks in the tanks of CSM-101, assigned to AS-207. The failure was particularly puzzling because the tanks of CSM-017 had been subjected to 320 psi for several minutes in ‘proof testing’. ASPO set up an investigation, which was to report by 4 November. As SM-012 had been through the same test regime, Shea grounded it pending this report. The problem was determined to be stress corrosion in the titanium resulting from the use of methyl alcohol as a test liquid. The point of the test was to verify the integrity of the tanks, and because the hydrazine and nitrogen tetroxide propellants were toxic another fluid had been used – and unfortunately this had caused damage! The remedy was to switch to a fluid that was compatible with titanium, and it was decided to use freon in the oxidiser tank and isopropyl alcohol in the fuel tank, with the additional stipulations that the systems must not have been previously exposed to the actual propellants and that after the tests the system must be purged by gaseous nitrogen. With the issue resolved, the tanks of SM-012 were removed for inspection and confirmed to be free of cracks.

The crew for the CSM-014 mission was announced on 29 September 1966. Wally Schirra would be in command, flying with Donn Eisele and Walt Cunningham. They would be backed up by Frank Borman, Tom Stafford and Michael Collins. Schirra was the only experienced man of the prime crew, but all the backup astronauts were veterans. In fact, Deke Slayton had given Schirra and Borman these assignments in March, on their return from an international ‘goodwill tour’ after the rendezvous of Gemini 6/7. Stafford and Collins had been assigned following Gemini 9 in June and Gemini 10 in July, respectively. Slayton had actually earmarked the rookies Eisele and Chaffee to Grissom’s crew, but in late 1965 Eisele had injured his shoulder in weightlessness training in a KC-135 aircraft and dropped out of training, prompting Slayton to swap Eisele with Ed White, whom Slayton had earmarked for Schirra’s crew. This Apollo 2 mission was to be a straightforward rerun of Apollo 1 to further evaluate the spacecraft’s systems.

In early December 1966, accepting that Apollo 1 would not fly that year, George Mueller postponed it to February 1967 and also deleted the Block f reflight in order to prevent the slippage of CSM-012 from impacting the Block II missions scheduled for later in 1967. Schirra had hoped to put his crew first in line for the dual mission, but Slayton imposed a rule that the man who would operate the CSM alone while his colleagues flew the LM must be experienced in rendezvous, since if the LM were to become crippled he would have to perform a rescue. Eisele was a rookie but Scott had performed a rendezvous on Gemini 8, so Slayton exchanged Schirra’s crew with McDivitt’s crew. Schirra was not pleased at being given the backup role, but Slayton had always intended to assign McDivitt the dual mission.

On the new schedule, AS-206 would launch LM-1 for an unmanned test as soon as possible after Apollo 1, and if this was satisfactory McDivitt’s crew would fly the dual mission (which was now AS-205/208 because deleting CSM-014 had released AS-205) as the revised Apollo 2 in August. This revision was publicly announced on 22 December, together with the assignment of Tom Stafford, John Young and Gene Cernan to backup McDivitt’s crew. Also, if two unmanned tests proved sufficient to ‘man rate’ the Saturn V, the intention was to launch AS-503 with a CSM and LM. The crew for this mission would be Frank Borman, Michael Collins and Bill Anders, backed up by Pete Conrad, Dick Gordon and Clifton Williams. These assignments had been made after Young flew Gemini 10 in July, Conrad and Gordon flew Gemini 11 in September, and Cernan backed up Gemini 12 in November.

The Gemini missions had demonstrated that for an astronaut on a spacewalk to be able to work effectively he must be provided with mobility and stability aids. On 6 December 1966 Slayton warned Joseph Shea that without handholds and tethering points, a transfer from the forward hatch of the LM to the CSM’s hatch would not be feasible. On 26 December Slayton recommended that a spacewalk be scheduled 100 hours into AS-503, after the two firings of the LM’s descent propulsion system but prior to the descent stage being jettisoned. One of the two astronauts would egress from the forward hatch and stand on the ‘front porch’ to assess the environmental control system in the LM during depressurisation, using the hatch, the performance of the life-support backpack, and the egress procedure for the emergency transfer. In addition, whilst outside, the spacewalker was to photograph the exterior of the LM to verify that it had not been damaged during its retrieval from the S-IVB. He would then re-enter the LM and the cabin repressurisation system would be tested, simulating the end of a moonwalk.

On 26 January 1967 Schirra’s crew made a ‘full up’ systems test of CSM-012 on its AS-204 launch vehicle. But the spacecraft drew its power from the pad, and the capsule was not pressurised with pure oxygen. It had not been a very productive day. ‘‘Frankly, Gus,’’ Schirra said in the debriefing with Grissom and Shea, ‘‘I don’t like it. You’re going to be in there with full oxygen tomorrow, and if you have the same feeling I do, I suggest you get out.’’ But there was a determination to catch up on the several-times-delayed schedule.

The next day, Friday, 27 January, Grissom’s crew attempted the ‘plugs out’ test in which the spacecraft would be on internal power and pressurised with pure oxygen at 16 psi (i. e. slightly above ambient) for an integrity check. If successful, this would clear the spacecraft for flight. After a simulated countdown, they were to end the day with an emergency egress drill.

In Houston, Flight Director John Hodge was monitoring progress, but the action was at the Cape. Slayton was in the Pad 34 blockhouse talking to Director of Launch Operations, Rocco Petrone. Also present was Stu Roosa, a rookie astronaut serving as the primary communications link with the crew. The Spacecraft Test Conductor, Clarence ‘Skip’ Chauvin, was in the Automated Checkout Equipment facility of the Manned Spacecraft Operations Building.

‘‘Fire!!’’ yelled Grissom at 18:31 local time, in a hold at T-10 minutes. ‘‘We’ve got a fire in the cockpit.’’

In all, there were 25 technicians on Level A8 of Pad 34’s service structure, and five more either on the access arm or in the White Room. Henry Rogers, NASA’s Inspector of Quality Control, was in the elevator, ascending the service structure. Systems technician L. D. Reece was waiting for the ‘Go’ to disconnect the spacecraft for the ‘plugs out’ test, which had been delayed by problems with communications, most notably the whistle from an ‘open’ microphone that could not be located.

‘‘Get them out of there!’’ commanded Donald Babbitt, North American Aviation’s Pad Leader, on hearing Grissom’s call. Mechanical technician James Gleaves was closest, but a spout of flame burst from the capsule before he could react, and he was beaten back by the flame and smoke.

Gary Propst, a technician of the Radio Corporation of America, was on the first level of the pad monitoring a TV camera located in the White Room pointing at the window in the spacecraft’s hatch. On hearing Grissom’s call, he looked up and saw a brilliant light in the window and gloved hands moving about within.

As soon as Slayton realised what had happened, he sent medics Fred Kelly and Alan Harter to the pad. ‘‘You know what I’ll find,’’ Kelly observed pointedly. The best that they would be able to do would be to supervise the retrieval of the bodies. On reflection, Slayton decided to accompany them. ‘‘We were the first guys from the blockhouse to reach the pad,’’ he later pointed out. Despite the intensity of the fire, Grissom, White and Chaffee had died by asphyxiation as a result of the toxic fumes created by the incomplete combustion of the synthetic materials in the cabin. They had received second and third degree burns, but these in themselves would not have been fatal. After several minutes Slayton left the White Room to call Houston, to report the situation. Shea had just arrived back in Houston and was briefing George Low when the news came through.

The Astronaut Office in Houston was very quiet. All the ‘old hands’ were absent. With Slayton away, Don Gregory, his assistant, ran the routine Friday staffmeeting. The meeting had only just convened when the red phone on Slayton’s desk rang. Gregory answered, then reported, ‘‘There has been a fire in the spacecraft.’’ Michael Collins was the senior astronaut present. He arranged for Al Bean to track down the wives. In each case, the news had to be broken by an astronaut who was also a close friend of the family. Charles Berry and Marge Slayton went to see Betty Grissom. Pete Conrad was sent to track down Pat White. Gene Cernan would have been ideal for Martha Chaffee because they lived next door, but he was in Downey with Tom Stafford and John Young, so Collins went to give her the bad news himself.

Al Shepard was in Dallas, Texas, about to deliver a speech at a dinner. He was taken aside and told of the fire. Wally Schirra, Donn Eisele and Walt Cunningham
were flying home from the Cape, and were told upon touching down at Ellington Air Force Base. Schirra immediately called Slayton at the Cape, who filled him in on the details. James Webb, Robert Seamans, Robert Gilruth, George Mueller, Kurt Debus, Sam Phillips and Wernher von Braun were at the International Club in Washington with corporate officials, including Leland Atwood of North American Aviation, to mark the transition from Gemini to Apollo. Webb immediately ordered Seamans and Phillips to the Cape to investigate. As Webb observed to newsmen shortly thereafter, “Although everyone realised that some day space pilots would die, who would have thought the first tragedy would be on the ground?”

The Board of Inquiry was chaired by Floyd L. Thompson, Director of the Langley Research Center, with Frank Borman as the Astronaut Office’s representative. The origin of the fire was near the foot of Grissom’s couch, where components of the environmental control system had repeatedly been removed and replaced in testing. Although the investigation did not identify the specific ignition source, it did find physical indications of electrical arcing in a wiring harness. ft was concluded that at some time during either manufacturing or testing an unnoticed incidental contact had scraped the insulation from a wire and thereby created the opportunity for a spark. This had ignited nearby flammable material, and in the super-pressurised pure-oxygen situation the result had been a brief but intense ‘flash’ fire. fn fact, there had been some 32 kg of nylon netting, polyurethane foam and velcro – all of it flammable in such conditions. fn retrospect, the worst flaw was the inward-opening hatch, which even under ideal conditions took several minutes to open, and would have been impossible to open with the internal pressure above ambient. Because neither the launch vehicle nor the spacecraft had been loaded with propellants, the ‘plugs out’ test had not been judged hazardous. Nevertheless, the launch escape system was directly above the spacecraft, and if the heat from the fire had ignited the solid propellant of this rocket the White Room crew would almost certainly have been killed as well.

fn an Associated Press interview in December 1966 Grissom had told Howard Benedict: ‘‘ff we die, we want people to accept it. We are in a risky business and we hope that if anything happens to us it won’t delay the program. The conquest of space is worth the risk of life.’’

fn an effort to reduce the risk of a fire during ground testing, it was decided to use an atmosphere comprising 65 per cent oxygen and 35 per cent nitrogen. After liftoff, the nitrogen would be purged and the pressure reduced to the originally planned 100 per cent oxygen at about 5 psi.

Although the investigation into the fire would take months, on 31 January NASA headquarters directed the Manned Spacecraft Center, Marshall Space Flight Center and Kennedy Space Center to proceed as planned with preparations for AS-501 with CSM-017 and LTA-10R, except that the command module was not to be pressurised with oxygen without specific authorisation.9 On 2 February CSM-014 was delivered

LTA-10R was a refurbished LM test article serving as a mass-model.

The exterior of the fire-damaged Apollo 1 command module in which Grissom, White and Chaffee died (top left); a view through the hatch; the crew positions, with the hatch above the center couch; the vicinity of the environmental control unit, where the ignition source is believed to have been; and its disassembled outer structures. Glenn, Cooper and Young escort Grissom’s coffin.

to the Cape to assist in training the technicians who were to disassemble CM-012 for the investigation. On 3 February George Mueller announced that although manned flights were grounded indefinitely, the unmanned AS-206, AS-501 and AS-502 were to proceed as soon as delivery of the hardware allowed. While the investigation into the fire was underway, Mueller suggested that when the Block II spacecraft became available the CSM-only flight should be deleted and the effort switched to combined testing with the LM, but Robert Gilruth warned that it would not be wise to test two new vehicles at once. In March it was decided to fly an 11-day CSM-only mission, in effect to perform Grissom’s mission with the upgraded model, and Slayton tipped off Schirra that his crew would fly it, backed up by Stafford’s crew. On 21 February, the day that Apollo 1 had been scheduled to launch, Floyd Thompson gave Mueller a preliminary briefing on the investigation’s findings, and several days later Robert Seamans sent a memo to James Webb listing Thompson’s early recommendations.10

On 15 March Deke Slayton proposed that a rendezvous with the S-IVB stage be a primary objective of Schirra’s flight, and said that this should occur “after the third period of orbital darkness’’. On 5 April Sam Phillips told the Manned Spacecraft Center, Marshall Space Flight Center and Kennedy Space Center that the profile for the first manned flight would be based on that developed for Grissom’s flight, dated November 1966. As the complexity of the mission was not to exceed that previously planned, and as no rendezvous had been planned, the rendezvous exercise should be assessed in terms of how it would complicate the mission rather than how it would advance the program. As the flight was to focus on evaluating the spacecraft’s systems, Chris Kraft pointed out on 18 April that if a problem were to develop that would require the cancellation of the rendezvous, then any manoeuvres which had already been made would complicate the nominal contingency de-orbit procedures. The rendezvous should not be initiated until “after a minimum of one day of orbital flight’’ and should be “limited to a simple equi-period exercise with a target carried into orbit by the spacecraft’’. On 2 June Phillips agreed with George Low that there should be a rendezvous but insisted that this should not be listed as a primary objective. The double-hatch of the Block I had been replaced on the Block II by a single ‘unified hatch’ on a hinge that swung outward. It had a manual release for either internal or external use, could be opened in 60 seconds irrespective of the differential in pressure, and was capable of being opened in order to conduct a spacewalk. But Phillips directed that there ‘‘be no additions that require major new commitments such as opening the command module hatch in space or exercising the docking subsystem’’.

NASA announced on 20 March 1967 that the unmanned LM-1 flight would be transferred from AS-206 to AS-204, which had become available. The rationale for the AS-205/208 dual mission with CSM-101 and LM-2 had been to ensure that testing of the LM would not be held up by the Saturn V development problems. The AS-501 and AS-502 development flights were to carry refurbished LM test articles, but unless

The final report of the Apollo 204 Review Board was submitted on 5 April 1967.

the pace of LM development dramatically picked up, the heavy launcher would become available ahead of the LM, thus rendering the ad hoc dual mission redundant. It was therefore decided that if the LM-1 test flight proved unsatisfactory, AS-206 would launch LM-2 unmanned to address the remaining test objectives. On 25 March George Mueller directed that missions be numbered in the order of their launch, regardless of whether they employed the Saturn IB or Saturn V and whether they were manned or unmanned – previously only the manned missions were to be counted. On the 1966 plan, Apollo 2 was to be CSM-014 (Schirra) and Apollo 3 was to be CSM-101 (McDivitt) flying the dual mission. The cancellation of the Block I reflight advanced CSM-101 to Apollo 2. After the fire, the desire not to reassign the name Apollo 1 had resulted in CSM-101 (Schirra) being seen as Apollo 2. But with paperwork in circulation for a variety of mission plans numbered up to Apollo 3, Mueller precluded the possibility of administrative confusion by directing that the first scheduled mission, AS-501, be named Apollo 4.[47]

On 7 April 1967 Joseph Shea was transferred to Washington as Deputy Associate Administrator for Manned Space Flight, and Low succeeded him as ASPO Manager at the Manned Spacecraft Center. Several days later, Everett Christensen resigned as Director of Mission Operations at headquarters.

A joint meeting of the Manned Spacecraft Center’s Flight Operations Directorate and Mission Operations Division announced on 17 April that: (1) successful firings by the descent and ascent stages of an unmanned LM, including a ‘fire in the hole’ separation of the two stages, should be prerequisites to a manned LM being allotted these functions; (2) a demonstration of EVA transfer should not be a prerequisite to manned independent flight of the LM; (3) the Saturn V should be ‘man rated’ as rapidly as possible; (4) three manned Earth orbit flights involving both the CSM and the LM should be the minimum requirement prior to attempting a lunar landing; and (5) although a lunar orbit mission should not be a formal step in the program, this should be planned as a contingency in the event of the CSM achieving lunar-mission capability ahead of the LM.

ASPO sent the Block II Redefinition Task Team, led by Frank Borman, to North American Aviation on 27 April. Having the authority to make on-the-spot decisions which previously would have required referral to the Configuration Control Board, it was to oversee the ‘redefinition’ of the Block II spacecraft, responding promptly to questions regarding detail design, quality and reliability, test and checkout, baseline specifications, configuration control, and scheduling. Meanwhile, the company had hired William D. Bergen from the Martin Company to supersede Harrison A. Storms as Apollo Project Manager. Bergen brought with him John P. Healy to manage the production of the first Block II at Downey, and Bastian Hello to run the company’s operations at the Cape.

On 8 May 1967 George Low reaffirmed that AS-205 would launch CSM-101 on an open-ended mission of up to 11 days to evaluate its systems. The next day, James Webb told a Senate committee that this mission would be flown by Wally Schirra, Donn Eisele and Walt Cunningham. When Webb canvassed suggestions for how to impress upon Congress that the Apollo program was recovering from the setback of the fire, George Mueller urged that the Saturn V be flown as soon as possible.

Astronomers’ Moon

CLASSICAL PHILOSOPHERS

Greek astronomy began with Thales, who was born shortly before 600 BC and lived in Miletus, a city of Ionia, which was a state on the western coast of what is now Turkey. As a philosopher he is regarded as one of the Seven Sages of Greece, and is considered to be the ‘father of science’. He set the seasons of the year and divided the year into 365 days. He also predicted a solar eclipse that occurred in 585 BC. It had been believed that the Moon was self-luminous, but he suggested that it shone by reflecting sunlight. Anaximander, a student of Thales, went to Italy in 518 BC. He opined that Earth floated in space – the prevailing view was that it was in some way supported on pillars through with the Sun passed during the night.

Pythagoras was born about 575 BC on Samos, an island off the coast of Ionia that was a crossroads between Asia, Africa and Europe. In his youth he reputedly visited Thales. Pythagoras considered the Moon to mark a fundamental boundary, in that it and everything ‘above’ was ‘perfect’, while Earth was subject to change and thus to decay. When critics argued that the markings on the face of the Moon indicated that it, too, was imperfect, it was suggested that the Moon was a mirror and the markings it displayed were really on Earth.

Around 450 BC Anaxagoras of Athens decided that Thales was correct in saying the Moon shone by reflecting sunlight. He realised that the Moon was spherical, and used this to explain its monthly cycle of ‘phases’. A generation later, Democritus, who travelled widely in ancient Greece, reasoned that the Moon was a world in its own right with a rugged surface, and he speculated that it might be an abode of life.

In the early fourth century BC, Plato, a student of Socrates, founded the Academy in Athens as the first institution of higher learning. Eudoxus briefly studied under Plato. After learning astronomy, he devised an explanation for the manner in which the constellations on view change with the seasons. He imagined the stars to be on a sphere that was centred on Earth, and the Sun to be on a slightly smaller concentric sphere made of transparent crystal which allowed the stars to be seen through it. The solar sphere turned around Earth on a daily basis, as did that with

the stars, but there was a slight differential in their rates that took a year to complete. Aristotle, another student of Plato, seized on this idea of ‘crystal spheres’ by proposing that there was one for each object that had an independent motion in the sky, and that their rotation was due to the action of angels. Although Eudoxus had envisaged crystal spheres only as a means of exposition, Aristotle believed them to be real and his views would come to dominate natural philosophy.

The points of light in the sky which move against the background of stars were called ‘planets’, meaning ‘wanderers’. In the third century BC Aristarchus of Samos suggested that the Sun might be located at the centre of the ‘planetary system’, with Earth being a sphere, rotating daily on its axis, and travelling around the Sun on an annual basis; but the idea attracted little support and was soon forgotten. Aristarchus also reasoned that because the Moon occults the Sun at a solar eclipse, the Sun must be further away – in fact, much further away. He also inferred that the stars must be considerably further away than the Sun, because they show no parallax when viewed from opposite sides of Earth’s path around the Sun. However, his reasoning on these matters was ignored. He interpreted a lunar eclipse as the Moon’s passage through the shadow cast by Earth, and made a fair estimate of the distance between the Moon and Earth in relation to the diameter of Earth. His contemporary, Eratosthenes of Cyrene, made the first realistic estimate of the Earth’s true diameter, thereby providing a scale to Aristarchus’s calculations.

At the end of the third century BC, Apollonius of Perga on the southern coast of modern Turkey was a Greek geometer with an interest in conic sections, and it was he who introduced the names to the ellipse, parabola and hyperbola. Although it was inconceivable that celestial objects should be less than perfect, detailed observations had shown their motions to be anomalous. Apollonius devised a geometrical scheme in which a celestial body would trace a small circle whose central point travelled in a circle around Earth; the small circle was termed the ‘epicycle’, and its centre was the ‘deferent’. This allowed the Moon to appear at times to lead and at other times to trail its perfect position. Furthermore, this accounted for why the size of the Moon appeared to vary in a cyclical manner. And of course, because the scheme involved only circles it restored purity.

Hipparchus, a Greek living in Alexandria, Egypt, in the second century BC, was the greatest of the classical Greek astronomers. His legacy was a star catalogue, but he also used a solar eclipse to estimate the relative distances of the Sun and Moon to a greater accuracy than had Aristarchus. He reasoned that although the Moon must orbit the Earth’s centre, the location of observers on the Earth’s surface provided the basis for parallax. On scrutinising records of eclipses that had been observed from both Alexandria and Nicaea, which lie on the same meridian but are some distance apart, he used the extents to which the Moon had masked the Sun’s disk to calculate the distance to the Moon relative to the Earth’s diameter. In fact, he calculated the distance of the Moon to within a few thousand kilometres and its diameter to within several hundred kilometres – although obviously he didn’t use kilometres as a unit of measure. Hipparchus also used measurements of the Moon’s orbit to assess Apollonius’s suggestion of deferents and epicycles, found it satisfactory, and provided measurements of the sizes of the epicycles.

In 80 AD the Greek historian Plutarch, who became a citizen of Rome, wrote the philosophical treatise Faces in Orbe Lunare in which he discussed the motion of the Moon across the sky, and how it maintained one face towards Earth as it turned on its axis. He thought that it was a world similar to Earth, and suggested it might be inhabited. A generation later, this latter point led the Greek storyteller Lucien of Samosata to write Vera Historia describing how a whirlwind lifted a ship from the sea and deposited it onto the Moon, where there was a battle in progress between the local inhabitants and invaders from the Sun. The story was a satire on the wars raged by the Greeks.

Claudius Ptolemaeus was born around 85 AD, probably in Alexandria, which was at that time under Hellenistic control. The Royal Library of Alexandria was founded at the start of the third century BC. Over the centuries it had built up an unrivalled catalogue, because whenever a ship docked in the harbour the authorities ordered copies made of any books that were on board. Ptolemy (as he is known in English) used his own observations of the stars and the resources of the library to refine the work of Hipparchus, and wrote up his findings in a book of his own. The library was sacked several times and eventually destroyed, but when this occurred is disputed. Although Ptolemy’s book was lost, an Arabic translation survived as the Almagest. He accepted Earth to be centrally located, celestial objects to be travelling in circles, Aristotle’s belief in the reality of concentric celestial spheres, and also Hipparchus’s endorsement of the deferents and epicycles as the reason for the anomalous motions. The Church of Rome accepted Aristotle’s philosophy, and so, despite its contrived nature, the ‘Ptolemaic system’ – as it became known, even although Ptolemy had not invented it – survived for over 1,000 years.