Category Paving the Way for Apollo 11

AS-205 lifted off from Pad 34 at 15:02:45 GMT on 11 October 1968 to fly the ‘C’ mission. Flown by Wally Schirra, Donn Eisele and Walt Cunningham, Apollo 7 was

to be open-ended up to 11 days and its purpose was to assess the performance of the Block II spacecraft.

The ascent phase was nominal and the S-IVB achieved a 123 x 152-nautical mile orbit. Prior to separating from the spent stage, the crew temporarily took command of the Instrument Unit and manually manoeuvred the combined vehicle in pitch, roll, and yaw, then they returned control to the launch vehicle. By the time the spacecraft separated at 002:55:02.40, venting of S-IVB propellants had raised the orbit to 123 x 170 nautical miles. The spacecraft moved clear, flipped and moved back in as if to retrieve the LM (which was absent). Since one of the four panels of the SLA had not fully deployed, it was decided that in future the panels would be jettisoned. One of the primary objectives was to demonstrate Apollo’s rendezvous capability using the spent stage as the target. At Schirra’s insistence, one man was awake at all times to monitor the spacecraft’s systems, even though the ongoing work made sleeping difficult. The rendezvous rehearsal was successfully achieved on the second day.

Although this was the first US spacecraft to have sufficient habitable volume for a man to leave his couch and move around, the crew suffered no disorientation in the weightless state, despite efforts to induce motion sickness. However, all three men developed head colds early on, making them grumpy, and in-flight TV, which was a secondary objective, provided a focus for their frustration. When the monochrome camera was finally switched on, however, it delivered excellent results and the crew played up to their audience. But it was a long and tedious flight of monitoring the systems to evaluate their performance, always prepared to intervene in the event of a problem. In fact, it was an exercise in would later be derided as “boring holes in the sky’’.

At 11:11:48 GMT on 22 October the command module splashed in the Atlantic 1.9 nautical miles from the target point. It initially assumed an apex-down attitude, but was soon turned apex-up by the inflatable bags on its nose. The astronauts were retrieved by helicopter and arrived on USS Essex an hour later.

The Apollo 7 mission was successful in every respect, with the service propulsion system firing perfectly eight times. Indeed, afterwards Schirra described the flight as a “101 per cent success’’. In combination with previous missions and ground tests, it certified the CSM for use in Earth orbit and for tests in the cislunar and lunar orbital environments.

On 7 November 1968 George Mueller declared that AS-503 was fit for a mission to the Moon. On 11 November Sam Phillips recommended to the Manned Space Flight Management Council that Apollo 8 enter lunar orbit. Later that day, Mueller told Thomas Paine that he had discussed the mission with the Science and Technology Advisory Committee and with the President’s Science Advisory Committee, both of which had endorsed the proposal, and he recommended that it should be undertaken. After speaking to Frank Borman by telephone, who confirmed his willingness to fly the mission, Paine gave the formal go ahead and told Phillips to make the necessary arrangements. The next day, NASA announced that Apollo 8 would be launched on 21 December and attempt a lunar orbital mission. Earlier in the year, Michael Collins had withdrawn from the crew to undergo a surgical procedure, and had been replaced by his backup, James Lovell.

Tom Stafford, John Young and Gene Cernan were announced on 13 November as the prime crew of Apollo 10, backed up by Gordon Cooper, Donn Eisele and Edgar Mitchell. This established the precedent for a crew backing up one mission, skipping two, and becoming the prime crew of the mission after that. It had yet to be decided, however, whether Apollo 10 would fly the ‘F’ or the ‘G’ mission.[51]

On 9 October 1968 AS-503, complete with CSM-103 and LTA-B, was rolled out to Pad 39A. The countdown demonstration test was completed on 11 December, and the actual countdown began at 00:00 GMT on 16 December. The launch window ran from 20 to 27 December, and it had been decided to try for 21 December to enable the astronauts to inspect the ALS-1 landing site in eastern Mare Tranquillitatis soon after local sunrise.

Frank Borman, James Lovell and Bill Anders entered the spacecraft with a little under 3 hours on the clock. There were no unplanned holds, and Apollo 8 lifted off at 12:51:00 GMT on 21 December for the ‘C-prime’ mission.

The ascent was nominal and the deviations from the trajectory when the S-IVB cut off at T+ 684.98 seconds were + 1.44 ft/sec in velocity and -0.01 nautical mile in altitude, which was almost perfect. At 002:27:22, after the S-IVB and spacecraft had been thoroughly checked, Collins, serving as the CapCom in Mission Control, made the momentous call, ‘‘Apollo 8, you are ‘Go’ for TLI.’’

The 317.7-second translunar injection was started at 002:50:37.8 and produced a velocity of 35,505.4 ft/sec. The spacecraft separated 30 minutes later and the four SLA panels were jettisoned. After turning around, the spacecraft’s ability at station­keeping with the spent stage was assessed. A 1.1-ft/sec manoeuvre was performed at 003:40:01 using the reaction control system of the service module to move clear of the stage, and a 7.7-ft/sec manoeuvre at 004:45:01 increased the separation rate.

At 004:55:56.0 the S-IVB opened its hydrogen vent valve and at 005:07:55.8 it passed oxygen through the engine. At 005:25:55.8 the auxiliary propulsion system was ignited and burned to depletion. The accumulated velocity increment placed the stage on course to fly by the trailing limb of the Moon at an altitude of 681 nautical miles and pass into solar orbit. The spacecraft’s service propulsion system executed a 2.4-second, 20.4-ft/sec midcourse manoeuvre at 010:59:59.2. A 24.8-ft/sec change had been planned, but the engine delivered less thrust than expected and a correction was made at 060:59:55.9 to refine the trajectory. These burns served to calibrate the service propulsion system in advance of calculating the orbit insertion manoeuvre.

In contrast to Apollo 7, this time all three crewmen experienced nausea as a result of rapid body movement, with the symptoms lasting up to 24 hours. The first of six TV transmissions started at 031:10:36 and ran for 23 minutes 37 seconds. The wide – angle lens gave an excellent view of the inside of the spacecraft, where Lovell was preparing a meal, but the telephoto lens passed too much light and pictures of Earth were poor. After a procedure was devised to tape a filter of the still camera onto the TV camera, it produced improved pictures of Earth during a transmission starting at 055:02:45. At 055:38:40 the astronauts were alerted that they had become the first people to enter a region where the gravitational attraction of another body exceeded that of Earth. The spacecraft had been slowing as it climbed up from Earth, but now it began to accelerate as it was drawn in by the Moon. However, they were not yet committed. If a reason developed not to brake into lunar orbit, then Apollo 8 would simply continue on its ‘free return’ trajectory around the back of the Moon and be ‘slingshot’ back to Earth. Although everything was going well, the translunar coast was frustrating in the sense that at no time were the crew able to see their objective owing to the spacecraft’s trajectory in relation to the positions of the Moon and the Sun.

The lunar orbit insertion manoeuvre began at 069:08:20.4 at an altitude of 75.6 nautical miles above the far-side of the Moon, and the 246.9-second burn produced an orbit ranging between 60.0 and 168.5 nautical miles with its high point above the near-side. After the post-burn checklist had been attended to, and while still passing over the far-side, the astronauts had their first opportunity to inspect the surface of the Moon up close. At 071:40:52 they gave a 12-minute TV transmission showing the passing terrain. In contrast to geologists, the astronauts described the surface in terms of ‘‘a battlefield’’, ‘‘a sandbox torn up by children’’, ‘‘a volleyball game played on a dirty beach’’, ‘‘plaster of Paris’’, or (vaguely scientifically) as ‘‘pumice’’. Bright ray craters appeared just as if they had been made by a ‘‘pickaxe striking concrete’’. The colour was varied, sometimes appearing to be black and white, yet other times displaying a distinctly brownish tan. In terms of mood, the surface was ‘‘desolate’’, ‘‘bleak’’ and ‘‘forbidding’’. A 9.6-second burn at 073:35:06.6 circularised the orbit at 60 nautical miles.

As this was the first opportunity for humans to directly observe the Moon at close range, James Sasser of the Apollo Spacecraft Project Office in Houston had served as the ‘project scientist’ for the mission. He formed an advisory team and this drew up a program of photography and visual observations for the crew to perform using a Maurer 16-mm movie camera and a Hasselblad with a 250-mm lens. In particular, the Manned Spacecraft Center wanted views of the eastern limb to assist in selecting landmarks for a lander’s navigational checks prior to the powered descent. Some of this documentation was to be overlapping vertical and oblique pictures which would enable stereoscopic analysis to determine the geographical position and elevation of each feature, but the movie camera was also to be fitted to the spacecraft’s sextant to depict the landmarks in context. In addition, some ‘scientific’ targets were marked on the flight charts as ‘targets of opportunity’ which were to be inspected if time and circumstances allowed. These were to provide either detailed coverage of specific features or broad coverage of areas which had not been adequately imaged by the Lunar Orbiters. And, of course, the ALS-1 landing site was to be inspected. Most of the scientific observing and photography was assigned to Anders, the LMP without a lunar module. Jack Schmitt, a professional geologist who was hired as an astronaut in 1965, served as the main interface between Sasser’s team and the Apollo 8 crew in training, but some briefings were provided by US Geological Survey staff. At the suggestion of Wilmot N. Hess, Director of the Science and Applications Directorate at the Manned Spacecraft Center, SasseTr’s team had set up a ‘science support’ room in Mission Control to listen to the astronauts’ commentaries and watch the TV of the lunar landscape passing below the spacecraft.

The astronauts could recognise surface features in shadows lit by Earthshine, and could see detail on sunward-facing slopes which had been ‘washed out’ in the Lunar Orbiter pictures. In fact, they could perceive detail to within 5 degrees of the ‘zero phase’ point, which is the line of sight with the Sun directly behind the observer. In planning the lunar landing the lower limit for Sun angle had been set at 6 degrees, but the astronauts could see surface detail at angles as low as 2 degrees. They were able to confirm that the upper limit of 16 degrees provided excellent definition, and their observations suggested that it might be possible to raise the limit to 20 degrees – but no higher than this. This enabled the lighting constraints for the lunar landing to be relaxed.

Of the two candidate landing sites in Mare Tranquillitatis, ALS-1 in the east was brighter; so much so, in fact, that it was debatable whether it was truly mare material or a flatfish portion of the adjacent terra. Observing it visually from an altitude of 60 nautical miles, Lovell said it reminded him of an aerial view of Pinacate in Mexico, a volcanic field which he had been shown in training.

Owing to crew fatigue, Frank Borman took the decision at 084:30 to cancel all secondary activities during the final two revolutions, to allow the crew to rest. The only tasks during this period were an alignment of the inertial guidance system and the preparations for transearth injection. But at 085:43:03 they provided the planned 27-minute TV transmission showing the Moon and Earth, and to mark the fact that it was Christmas Eve they recited the first ten verses of the Book of Genesis from the Bible prior to signing off with, ‘‘Good night, good luck, a Merry Christmas, and God bless all of you – all of you on the good Earth.’’

Radio tracking indicated that by the time Apollo 8 was ready to head for home the mascons had perturbed its initially circular orbit into one of 58.6 x 63.6 nautical miles. At 089:19:16.6, after ten revolutions of the Moon, the 203.7-second transearth injection was made on the far-side of the Moon at an altitude of 60.2 nautical miles, which was just about perfect. After returning to the Earth’s gravitational influence, the spacecraft progressively accelerated. Only one small midcourse correction was required. It was made at 104:00:00, and the 15.0-second burn by the service module reaction control system imparted a change of 4.8 ft/sec.

On shedding the service module, the command module adopted its entry attitude and at 146:46:12.8 hit the entry interface travelling at 36,221.1 ft/sec. It pursued an automatically guided profile. The ionisation bathed the interior of the cabin in a cold

An oblique view by Apollo 8 looking northwest across the eastern part of Mare Tranquillitatis. The crater in the foreground is Taruntius-F, and one of the Cauchy clefts crosses the upper part of the picture. The ALS-1 site is out of frame to the south.

blue light as bright as daylight. At 180,000 feet, as expected, the lift vector deflected the vehicle to 210,000 feet, then it resumed its downward course. It splashed into the Pacific 1.4 nautical miles from the target at 15:51:42 on 27 December. It adopted an apex-down position, but promptly righted itself. The astronauts were soon recovered and flown by helicopter to USS Yorktown.

This audacious mission, described as the “greatest voyage since Columbus”, took NASA a giant step towards achieving Kennedy’s challenge.

On 6 January 1969 Deke Slayton called Neil Armstrong, Michael Collins and Buzz Aldrin to his office at the Manned Spacecraft Center and told them that they would fly Apollo 11 and should assume their mission would involve a lunar landing.

On 10 January 1969 John Stevenson, Director of Mission Operations at the Office of Manned Space Flight, circulated a revised version of the tentative schedule for the year that was issued early in 1968. This called for launching the delayed ‘D’ mission on 28 February. As the ‘E’ mission had been rendered irrelevant by Apollo 8, this meant that if the ‘F’ mission flew in May and was satisfactory, it should be possible to attempt the lunar landing in July. The rationale for the ‘F’ mission was to obtain experience of operating in deep space, but after Apollo 8 the issue became whether another test in lunar orbit was required. The decision was postponed until LM-3 had been put through its paces.

Apollo 9 was to be the ‘D’ mission – a lunar module manned flight demonstration in Earth orbit. The payload for the AS-504 launch vehicle was CSM-104 and LM-3. As they were to operate independently, the spacecraft were given radio call-signs. The blue wrapping of the command module for its shipment to the Cape had given it the appearance of a sweet, so it was named ‘Gumdrop’. The arachnid-like configuration of the lunar module prompted the name ‘Spider’.

The launch was scheduled for 28 February 1969 and the countdown was begun at 03:00:00 GMT on 27 February with 28 hours on the clock, but 30 minutes into the planned 3-hour hold at T-16 hours the clock was recycled to T-42 hours in order to enable the crew of James McDivitt, David Scott and Rusty Schweickart to recover from a mild respiratory infection. The count picked up at 07:30:00 on 1 March and the vehicle lifted off from Pad 39A on time at 16:00:00 GMT on 3 March.

The ascent was nominal and at S-IVB cutoff at T+664.66 seconds the deviations were +2.86 ft/sec in velocity and -0.17 nautical mile in altitude, with the result that the initial orbit was almost perfect at 100 nautical miles. At 002:41:16.0 the S-IVB released the CSM, which moved clear, turned end over end to aim its apex at the top of the LM and moved back in. At 003:01:59.3 it docked at the first attempt, marking the first use of this apparatus. Once the tunnel between the two spacecraft had been pressurised, the crew opened the apex hatch of the command module to confirm that all the latches on the docking ring had engaged, and after lines had been connected to supply power to the dormant LM the hatch was reinstalled. On a command issued by the CSM at 004:08:09 the S-IVB released the docked combination.

After the spacecraft was clear, the S-IVB reignited its engine at 004:45:55.5 to raise an apogee of 1,672 nautical miles. Then, after a period of coasting to allow the engine to cool down, it initiated a final burn at 006:07:19.3 to achieve a velocity of 31,620 ft/sec which would send it into solar orbit.

Meanwhile, at 005:59:01.1 a 5.2-second burn by the service propulsion system raised the spacecraft’s orbit to 111 x 128 nautical miles. Three further manoeuvres on the second day in space measured the oscillatory response of the docked vehicles to obtain data designed to improve the autopilot’s response in this configuration, and also burned off the CSM’s propellant to increase the fidelity of manoeuvres which it would later perform in Earth orbit to rehearse what a mission would do in lunar orbit.

On the third day in space, Schweickart entered the LM to check out its systems. McDivitt joined him 50 minutes later. At about 045:52, shortly after the landing gear was deployed, McDivitt advised Mission Control that Schweickart had twice been sick – this illness would have an impact on the EVA planned for later in the mission. At 046:28 the astronauts made a 5-minute TV transmission from inside the LM. The descent engine was ignited at 049:41:34.5 for a 371.5-second burn in which the autopilot controlled the attitude of the docked vehicles and the astronauts manually throttled the engine to full thrust. The LM was deactivated at 051:00. Several hours later, a service propulsion system burn achieved an almost circular orbit of 125.9 x 131.0 nautical miles in preparation for the rendezvous sequence.

The EVA plan had called for Schweickart to exit the LM’s forward hatch, transfer to the command module hatch, and then return. But owing to his bouts of nausea the spacewalk was cut back from 2 hours 15 minutes to just 39 minutes, to be made on a single daylight pass. The LM was depressurised at 072:45, and the hatch opened at 072:46. Schweickart initiated his egress at 72:59:02, feet first and face up, and was completely out by 073:07. He was wearing the Extravehicular Mobility Unit suit and Portable Life Support System backpack which astronauts were to wear on the lunar surface. A 25-foot nylon safety tether precluded him drifting away. For stability, he inserted his feet into a pair of ‘golden slippers’ on the ‘porch’ of the descent stage. Meanwhile, at 073:02:00 Scott opened the side hatch of the command module and poked his head and shoulders out to monitor Schweickart. Although the transfer to the command module hatch had been cancelled, Schweickart was able to make an abbreviated study of translation and body-attitude-control using handrails affixed to the upper part of the LM. Before ingressing, Schweickart shot 16-mm movie footage of Scott’s activities, and 70-mm Hasselblad pictures of the exterior of both vehicles. Although the EVA was brief and did not involve a period of orbital darkness, it was sufficient to certify the suit and backpack for use on the lunar surface. The LM was repressurised at 073:53, and the CSM several minutes later. After a TV transmission from the LM that started at 074:58:03 and lasted 15 minutes, it was deactivated and McDivitt and Schweickart rejoined Scott.

On the fifth flight day McDivitt and Schweickart were back in the LM by 088:55 in order to prepare that ship for a period of free flight and an active rendezvous. At 092:22 the CSM oriented the pair into the attitude required for undocking. This was attempted at 092:38, but the latches did not fully release until 092:39:36. This was to be the first time that astronauts flew a spacecraft that was incapable of returning to Earth if an emergency were to arise – they relied on Scott to rescue them. Once free, the LM pirouetted while Scott made a visual inspection. At 093:02:54 the CSM used the thrusters of its reaction control system to make a separation manoeuvre. Over the next 6.3 hours, the LM undertook a series of manoeuvres which set up and executed a rendezvous. In the process, the descent propulsion system was fired under different control regimes and with the throttle being varied, after which the descent stage was jettisoned and the rendezvous was performed by the ascent stage. Terminal phase braking began at 098:30:03, and was followed by a period of station-keeping, then formation flying to facilitate mutual photography prior to docking at 099:02:26. McDivitt and Schweickart then transferred back to the CSM. The ascent stage was jettisoned at 101:22:45.0, and half an hour later ignited its main engine and fired it to depletion to enter a 126.6 x 3,760.9-nautical mile orbit.

The remainder of the mission was less hectic, being devoted mainly to conducting multispectral photography to prepare for the Skylab space station. At 169:30:00.4 the service propulsion system was fired in a 24.9-second burn which established the conditions for a nominal de-orbit. Unfavorable weather in the planned recovery area prompted a postponement of the de-orbit by one revolution, and it was performed at 240:31:14.8. The service module was jettisoned a few minutes later. The command module flew the entry profile under the control of its primary guidance system, and splashed into the Atlantic at 17:00:54 on 13 March about 2.7 nautical miles from the target. It settled in the ideal apex-up flotation attitude, and within an hour the crew were onboard USS Guadalcanal.

With Apollo 9 having successfully tested the LM in Earth orbit, the next issue was whether to fly the ‘F’ mission or to push on and attempt the lunar landing. In fact, it would be impossible for LM-4 to attempt the ‘G’ mission, as the software to conduct the powered descent was still under development. Furthermore, owing to propellant restrictions in the ascent stage of this somewhat overweight LM it would be unable to lift off and rendezvous. Tom Stafford, the Apollo 10 commander, argued against his crew waiting for LM-5 to become available. ‘‘There are too many ‘unknowns’ up there,’’ he noted. ‘‘We can’t get rid of the risk element for the men who will land on the Moon but we can minimise it; our job is to find out everything we can in order that only a small amount of ‘unknown’ is left.’’

On 24 March 1969 NASA stated that Apollo 10 would fly the ‘F’ mission. The original idea had called for the LM merely to undock, enter a slightly different orbit, rendezvous and redock, but in December 1968 the Mission Planning and Analysis Division at the Manned Spacecraft Center had urged putting the descent propulsion system through a high-fidelity rehearsal in which the LM would lower its perilune sufficiently to test the ability of the landing radar to detect and lock onto the surface. Howard Tindall also proposed that the LM should initiate the powered descent and then execute an early abort by ‘fire in the hole’ staging, but his colleagues convinced him that this would be too adventurous. One aspect of the decision to go ahead with the ‘F’ mission was to evaluate the tracking and communications of two vehicles in lunar orbit. In essence, it had been decided to exploit the fortuitous relaxation in schedule pressure and improve on Apollo 8 by performing a rehearsal to the point at which a later LM would initiate its powered descent.

The finally agreed plan called for the LM to separate from the CSM in the circular lunar parking orbit, enter an elliptical orbit having a perilune of about 50,000 feet located just east of the prime landing site, execute a low pass and then jettison the descent stage to make the rendezvous.

In April 1969 the site selectors met to decide the prime target for the first Apollo landing. The photographs of ALS-1 taken by Apollo 8 indicated the presence of a smooth blanket of light-toned material that softened or masked the landscape, and a study of the craters showed that the regolith was quite thick, which in turn implied a considerable age. The fact that the site was atypical of the maria made it unattractive for dating the maria, so it was rejected. This left ALS-2 in the southwestern part of Mare Tranquillitatis as the prime target. In early May, Jack Schmitt put it to Tom Stafford that the launch of Apollo 10 be slipped 24 hours from the proposed date so that the low-perilune pass over ALS-2 could be made in illumination matching that of a mission attempting to land there. This would enable high-resolution pictures to be taken of the site and the landmarks on the approach route. Stafford was receptive. Schmitt approached George Low, who asked Chris Kraft, who sought the advice of the flight control specialists – there were issues in favour and against. When the case was put to Sam Phillips he rescheduled the launch.

AS-505 had been installed on Pad 39B on 11 March, and Apollo 10 lifted off on schedule at 16:49:00 GMT on 18 May 1969 with Tom Stafford, John Young and Gene Cernan.

When the S-IVB cutoff at T + 703.76 seconds, the deviations were -0.23 ft/sec in velocity and -0.08 nautical miles in altitude. After translunar injection, CSM-106 ‘Charlie Brown’ separated, turned around and docked with LM-4 ‘Snoopy’, then the pair were released by the stage. The S-IVB then used propulsive venting to adopt a path that would fly past the Moon and enter solar orbit. At 026:32:56.8 the service propulsion system made a 49.2-ft/sec burn to match a July lunar landing trajectory. At 075:55:54.0 the spacecraft entered an initial lunar orbit of 60.2 x 170.0 nautical miles. Two revolutions later, this was refined to 59.2 x 61.0 nautical miles. During a 30-minute colour TV transmission the astronauts showed off the lunar surface. They reported the colour of the surface to be less grey than was described by Apollo 8. In particular, Mare Serenitatis appeared ‘‘tan’’, whereas Mare Tranquillitatis appeared ‘‘dark brown’’.

After undocking at 098:29:20, the vehicles took up station 30 feet apart while Young inspected the LM, and then the CSM moved off. A 27.4-second burn by the descent propulsion system at 099:46:01.6 placed the LM into a descent orbit with its perilune 15 degrees east of ALS-2. The landing radar was tested while passing over that site at an altitude of 47,400 feet an hour later. The pictures taken were of greater resolution than those transmitted by the Lunar Orbiters. Unfortunately, the 16-mm

This oblique view looking northwest across the crater Maskelyne was taken by the Apollo 10 Lunar Module ‘Snoopy’ as it flew low over Mare Tranquillitatis towards the ALS-2 target.

movie camera failed. A descent propulsion system burn at 100:58:25.9 put the LM into an orbit of 12.1 x 190.1 nautical miles to arrange a ‘lead angle’ equivalent to that which would occur at cutoff of an ascent from the lunar surface. At 102:44:49, during preparations to start the rendezvous with the CSM, the LM started to wallow off slowly in yaw and then stopped, and several seconds later it initiated a rapid roll accompanied by small pitch and yaw rates. Subsequent analysis revealed that this anomalous motion was due to human error. The control mode of the abort guidance system had inadvertently been returned to AUTO instead of the Attitude HOLD mode for staging. In AUTO, the abort guidance system steered the LM to enable the rendezvous radar to acquire the CSM, which at this point was not in accordance with the plan. The required attitude was re-established by the commander taking manual control. The descent stage was jettisoned at 102:45:16.9, and 10 minutes later an ascent propulsion system burn achieved an orbit of 11.0×46.5 nautical miles. This matched the insertion orbit for a mission returning from the surface. The LM had the active role in the rendezvous, and docked at 106:22:02. Two hours later the ascent stage was jettisoned, and during the next revolution the ascent propulsion system was fired to depletion in order to place the vehicle into solar orbit.

At 137:39:13.7, after 31 lunar revolutions, the CSM made the transearth injection. The aim was so accurate that it required only a 2.2-ft/sec refinement 3 hours prior to shedding the service module to centre the trajectory in the ‘corridor’ for atmospheric entry. The capsule splashed into the Pacific 1.3 nautical miles off target at 16:52:23 on 26 May and adopted the apex-up flotation attitude. The astronauts were aboard USS Princeton within the hour.

While Apollo 10 was in transit to the Moon, AS-506 was rolled out to Pad 39A in preparation for the Apollo 11 mission. After the pictures taken during the low pass over ALS-2 were examined, it was confirmed as the prime site for Apollo 11. ALS-3 in Sinus Medii was 2 day’s terminator travel westward and would be the backup. If the launch had to be delayed beyond the date for ALS-3, then the target would be ALS-5 in Oceanus Procellarum. In the post-flight debriefing, Tom Stafford pointed out that although the ALS-2 aim point was acceptable, the western end of the ellipse was much rougher. He advised Neil Armstrong that if he were to find himself at the far end of the ellipse and did not have the hover time to manoeuvre among the small craters and boulders to select a spot on which to land, then he would have to ‘‘shove off” – by which Stafford meant abort.

A week before Apollo 11 was due to launch, people began to congregate at the Cape communities of Titusville, Cocoa Beach, Satellite Beach and Melbourne. They came from all around the world in order to be able to tell their grandchildren they were present when men set off to try to land on the Moon. By 15 July hotels and motels allowed late-comers to install camp beds in lounges and lobbies, but most people spent the night on the beaches and by the roadside, generating the worst congestion

in Florida’s history. With the notable exception of alarm clocks, which rapidly sold out, shops were able to supply the hoards. As it was to be a dawn launch, the parties ran through the night.

When AS-506 lifted off at 09:32:00 local time on 16 July on a mission to accept President Kennedy’s challenge of landing a man on the Moon before the decade was out, it was estimated that there were about a million people present and 1,000 times as many watching on ‘live’ television.

No-one could be certain that the objective would be achieved, but the way had certainly been well paved.

[1] He did not infer from the absence of detail in the shadows that the Moon was airless, nor did he suggest the presence of open water.

[2] In fact, one of the few names introduced by van Langren to have survived is Langrenus, by which he honoured his own family.

[3] Selene was the Greek moon-goddess.

[4] Like Herschel and Schroter, von Gruithuisen believed the Moon to be inhabited, and after using a small telescope he reported in 1824 his discovery of a city in the equatorial zone near the meridian; but this was later shown to be merely a group of shallow ridges that were visible only when the Sun was low on the local horizon.

[5] For over half a century, geologists had argued about how the Coon Butte crater formed – and this was for a structure that was accessible to in-situ examination. Could there be any hope of resolving the issue of the lunar craters, which could only be peered at from afar!?

[6] On transfer to NASA, the Langley Aeronautical Laboratory became the Langley Research Center, the Ames Aeronautical Laboratory became the Ames Research Center, the Lewis Flight Propulsion Laboratory became the Lewis Research Center and the High-Speed Flight Station became the Flight Research Center.

[7] On 3 December 1958 Eisenhower ordered that JPL be transferred to NASA. This took effect on 1 January 1959, although only under contract, since the facility was owned by Caltech, which NASA paid. In September 1959 the Pentagon voluntarily yielded the Army Ballistic Missile Agency since the military had decided it did not require the Saturn launch vehicle; it would develop the Titan III instead. On 21 October 1959 NASA announced that it was to gain von Braun’s rocket team. On 1 July 1960 the Army Ballistic Missile Agency became the Marshall Space Flight Center.

[8] Physicists James van Allen, Homer Newell, Charles Sonett and Lloyd Berkner were notable early members of the ‘sky science’ community.

[9] Colloquia were held quarterly at different venues on the West Coast through to May 1963.

[10] As would later be realised, Mare Moscoviense fills the floor of a 300-km-diameter crater and Tsiolkovsky covers a portion of the floor of a crater which has a prominent central peak.

[11] The name Ranger set a trend for lunar projects with the names Surveyor and Prospector; in contrast to Mariner for planetary missions – that is ‘land’ names as against ‘sea’ names.

[12] Later, launch operations would be made a separate field centre.

[13] In early 1962 the entire NASA launch organisation was restructured.

[14] The Soviet spacecraft fell silent on 27 February 1961, at a distance of 2З million km from Earth. A launch on 4 February had stranded a similar spacecraft in parking orbit, but its role was disguised by naming it Sputnik 7.

[15] Surface science was only one of the objectives; there were the investigations to be made during the terminal approach, and achieving these would mark an acceptable compromise on the first mission.

[16] They were Lieutenant Commander Alan Bartlett Shepard Jr, Lieutenant Malcolm Scott Carpenter and Lieutenant Commander Walter Marty Schirra Jr from the Navy; Lieutenant Colonel John Herschel Glenn Jr from the Marines; and Captain Virgil Ivan ‘Gus’ Grissom, Captain Donald Kent ‘Deke’ Slayton and Captain Leroy Gordon Cooper Jr from the Air Force.

[17] This reasoning would resurface when John F. Kennedy asked for a worthy challenge.

[18] In a reorganisation on 8 December 1959, the Office of Space Flight Development had become the Office of Space Flight Programs.

[19] In fact, NASA could have launched Shepard several weeks ahead of Gagarin’s flight. If this had been done, Kennedy may well not have issued the challenge of landing a man on the Moon before the decade was out. The fact that Shepard’s flight had been only suborbital whereas Gagarin’s was orbital, would probably not have mattered, since the world’s first ‘spaceman’ would have been an American. The fact that America ‘lost’ both the first satellite and the first man into space could be said to be directly responsible for the race to the Moon. It serves to illustrate that history is not an irresistible tide, it can be extremely sensitive to the outcome of singular events.

[20] Earth imparts a gravitational acceleration of 32.2 ft/sec2.

[21] Newell also wished to maximise the amount of science on manned flights in Earth orbit.

[22] Despite Gold’s assertion that the dust would react only slowly upon being loaded, reporters would remain fascinated by the possibility that a lander would rapidly become submerged by it!

[23] The crater made by Ranger 8 was photographed by Lunar Orbiter 2, and found to be about 13.5 metres in diameter with a mound at its centre.

[24] The converter was installed at JPL, not at Goldstone.

[25] The crater made by Ranger 9 was photographed by Apollo 16 in 1972. At 14 metres in diameter, it was similar to that of its predecessor.

[26] The delay in the Centaur stage was in part due to problems with the configuration of its propellant tanks, but also because the Marshall Space Flight Center was busy with the Saturn launch vehicles. In early 1962, therefore, the Centaur had been transferred to the Lewis Research Center.

[27] In the case of Lunar Orbiter, the wide-angle images would be referred to as medium (M) frames and the narrow-angle images as high-resolution (H) frames.

[28] In fact, Bimat was similar to the Polaroid process.

[29] In particularly, the Planetology Subcommittee called for the Lunar Orbiter Block II to undertake selenodesy, gamma-ray, X-ray, magnetometry, microwave and non-imaging radar studies from orbit.

[30] This was because on a direct ascent the translunar injection point was necessarily near the latitude of the launch site, and for a launch from Florida this was north of the equatorial plane on a southerly heading, which meant that by the time the spacecraft reached lunar distance it would be south of the equatorial plane.

[31] The Manned Space Flight Network was operated under the direction of the Goddard Space Flight Center in support of the Manned Spacecraft Center.

[32] In fact, stereoscopic analysis of the Lunar Orbiter pictures proved difficult due to the manner in which they were scanned in narrow strips for transmission, as this gave the impression of the surface as being corrugated.

[33] Whereas in summer the Moon reaches its ‘full’ phase south of the equator, in winter it does so north of the equator, and since for the early Surveyors the landing sites were well to the west of the lunar meridian with arrival soon after local sunrise in winter months the translunar injection had to be made from south of the Earth’s equator. The restartable Centaur facilitated this by using its first burn to achieve a parking orbit and, once south of the equator, using its second burn to head for the Moon.

[34] During a solar eclipse, when the Moon occults the Sun to terrestrial observers, the irregular profile of the lunar limb often allows light from small sections of the solar disk to be viewed during totality, giving rise to a phenomenon known as Baily’s Beads after the British astronomer Francis Baily who first noted them during an annular eclipse on 15 May 1836.

[35] The term ‘psia’ means pounds of force per square inch on an ‘absolute’ scale measured relative to zero. If a pressure gauge is calibrated to read zero in space, then at sea level on Earth it would read 14.7 psi, which is sea-level atmospheric pressure. A value specified in psia is therefore relative to vacuum, rather than a differential relative to the pressure at sea level on Earth. For large numbers, the difference is insignificant.

[36] The pictures taken by Lunar Orbiter 1 showing Earth against the lunar limb were in black – and-white.

[37] Both Apollo 15 and Apollo 17 were sent to sites imaged by Lunar Orbiter 5; although in the case of Apollo 17 the observations by Apollo 15 also contributed to the selection.

[38] In the late 1950s J. J. Gilvarry argued that the maria were once water oceans, and hosted life. He said the now-dry plains were sedimentary rock, and dark owing to the presence of organic material. He claimed the elemental abundance data from the alpha-scattering instrument matched mudstone even better than it did basalt.

[39] Although NASA was unaware of it, a gamma-ray spectrometer operated in lunar orbit by Luna 10 in 1966 had provided a rudimentary analysis of the composition of the lunar surface across a wide range of latitudes, and the results showed there to be no significant exposures of acidic rock in the highlands.

[40] The term ‘facies’ was introduced to geology in 1838 by the Swiss stratigrapher Amanz Gressly to specify a body of rock having given characteristics.

[41] They were: Lieutenant Charles ‘Pete’ Conrad Jr, Lieutenant Commander James Arthur Lovell Jr, and Lieutenant Commander John Watts Young from the Navy; Major Frank Frederick Borman II, Captain James Alton McDivitt, Captain Thomas Patten Stafford, and Captain Edward Higgins White II from the Air Force; Neil Alden Armstrong, a former naval aviator, now a civilian test pilot for NASA; and Elliot McKay See Jr, a civilian test pilot for the General Electric Company.

[42] Slayton had been grounded in 1962 owing to a heart irregularity while training for a Mercury mission.

[43] They were: Major Edwin Eugene ‘Buzz’ Aldrin Jr, Captain William Alison Anders, Captain Charles Arthur Bassett II, Captain Michael Collins, Captain Donn Fulton Eisele, Captain Theodore Cordy Freeman, and Captain David Randolph Scott from the Air Force; Lieutenant Alan LaVern Bean, Lieutenant Eugene Andrew Cernan, Lieutenant Roger Bruce Chaffee, and Lieutenant Commander Richard Francis Gordon Jr from the Navy; Captain Clifton Curtis Williams from the Marines; Ronnie Walter Cunningham, a research scientists at the RAND Corporation; and Russell Louis ‘Rusty’ Schweickart, a research scientist at the Massachusetts Institute of Technology.

[44] This name change officially took effect on 20 December 1963.

[45] On 26 October 1962 a nomenclature was introduced by which the pad abort tests were to run in sequence from PA-1; the Little Joe II flights were to start at A-001; missions using the Saturn I were to start at A-101; missions using the Saturn IB were to start at A-201; and missions using the Saturn V were to start at A-501, with the ‘A’ standing for ‘Apollo’. The ‘SA’ prefix was employed by the Marshall Space Flight Center (giving precedence to the launch vehicle) and the ‘AS’ prefix was used by the Manned Spacecraft Center (giving precedence to the spacecraft). In addition, the term ‘space vehicle’ was introduced to describe the integrated ‘launch vehicle’ and ‘spacecraft’, with the latter comprising the CSM, the LM (if present) and the SLA structure.

[46] NASA’s Flight Research Center at Edwards Air Force Base was renamed in Dryden’s honour.

[47] On 30 March 1967 George Low suggested that the AS-201 and AS-202 test flights be assigned the designations Apollo 2 and Apollo 3 retrospectively in order to fill in the gap, but this was rejected by Mueller on 24 April. AS-203 was not included because it did not carry a spacecraft.

[48] The last two categories represented the lunar part of the Apollo Applications Program which was being promoted by George Mueller, and when this fell by the wayside the reconnaissance surveys were deleted and the main program was expanded to include ‘enhanced capability’ landings.

[49] Times in this hhh:mm:ss format are with reference to the time of launch.

[50] It is worth noting that the guidance system in the IU performed this magnificent recovery entirely on its own.

[51] CSM-101 had flown on Apollo 7, CSM-102 had been retained by North American Aviation for ground testing, CSM-103 had been assigned to the Apollo 8 ‘C-prime’ mission, CSM-104 was to fly the Apollo 9 ‘D’ mission, CSM-105 was for ground testing, and CSM-106, which was delivered to the Cape on 25 November 1968, was assigned to Apollo 10.

Grove Karl Gilbert was born in Rochester, New York, in 1843. After conducting a number of surveys as a field geologist, he was made Senior Geologist when the US Geological Survey was founded in 1879. Over 18 nights during August, September and October 1892, Gilbert used the 26-inch refractor of the US Naval Observatory in Washington DC to study the Moon. Pointing out that lunar craters have floors lying generally below rather than above the level of the adjacent terrain, he rejected the

volcanic interpretation and argued that craters must be the result of impacts. He further proposed that the arcuate chains of mountains at the periphery of the ‘circular maria’ are the walls of craters produced by vast impacts. As evidence, Gilbert cited what he called ‘sculpture’ as the fall of ejecta thrown out during the formation of Imbrium. He announced his results in The Moon’s Face: A Study of its Origin and its Surface Features, a paper presented orally to the Philosophical Society of Washington on 10 December to mark his retirement as its president. The paper was published in the Bulletin in 1893, but as this was not a publication on the reading list of astronomers his remarkable intrusion into their bailiwick passed unnoticed.

In 1946 Harvard geologist R. A. Daly rejected the endogenic origin of craters and, argued in favour of impact, citing Gilbert’s paper. Also in 1946, geologist R. S. Dietz expanded on the subject, listing several criteria that showed how lunar craters differ from terrestrial volcanic craters.

The American geologist J. E. Spurr began to study the Moon in 1937, having been inspired by the photographs taken by Francis Pease using the 100-inch telescope on Mount Wilson. He presumed that the Moon could be described in terrestrial terms, and between 1944 and 1949 wrote up his systematic analysis in four volumes under the general title Geology Applied to Selenology, offering volcanic explanations for a wide variety of lunar features. In particular, he said that early in lunar history large calderas left cavities which were later flooded by lava to make the ‘irregular maria’, and subsequently the better preserved ‘circular maria’. Critics of the impact origin of craters pointed out that whilst there were many examples of small craters on the rims of larger ones, there were no cases of large craters overlapping smaller ones. Spurr said craters were volcanic, and were produced with progressively smaller diameters. He interpreted faults and ridges as evidence of lines of weakness in the crust. Since he mapped these up the meridian and around the limb regions, he said they were due to stresses imparted as the Moon’s rotation synchronised with its orbital period. He

claimed this ‘lunar grid system’ had significantly controlled the formation of craters. This thesis was eagerly accepted by those who believed volcanism played the main role in shaping the lunar surface. In particular, it was claimed that lines of weakness had prompted eruptions that produced ‘chains’ of large craters whose members were isolated from one other by significant distances. But critics argued that the lines of weakness were illusory, since relief highlighted by the sunrise or sunset terminator will favour north-south trends and not east-west trends. And, of course, any pair of craters can be said to be related if an observer is so inclined.

It was not until Ralph B. Baldwin made an analysis of bomb craters in the Second World War that the impact origin of lunar craters began to make real headway. As a businessman trained in physics, he developed an interest in the Moon in 1941 during a visit to a planetarium when, in viewing the pictures on display, he independently noticed Imbrium sculpture. On later reading up and finding no explanation (since he did not happen across Gilbert’s paper) Baldwin decided to conduct his own study. In an article published in the magazine Popular Astronomy in 1942 he argued that the ridges and grooves were “caused by material ejected radially from the point of explosion’’ by the impact which formed Imbrium – although, like everyone else, he presumed that the impact formed the mare itself. In a follow-up in 1943 he reasoned that the projectile had been “flattened” by the shock and had excavated the cavity in a lateral manner, which was why the nearest sculpture consisted of grooves rather than chains of craters made by plunging debris – the latter occurred further out. He published in a popular outlet because his work was rejected by professional journals – evidently the Moon was not an object for worthwhile study. In his book The Face of the Moon, published in 1949 by the University of Chicago, Baldwin reported his observations, experiments and analyses, and included a review of the literature (by now he knew of Gilbert). His own contribution as a physicist drew upon an analysis of bomb craters in which he showed that the greater the deceleration on impact, the greater the energy released. He reasoned that although the weak lunar gravity would enable an explosion to throw ejecta to a greater distance, it would not actually make the crater larger. He logarithmically plotted the relationship between the diameters and depths of explosive craters on Earth, the craters on Earth accepted to have been made by cosmic impacts, and ‘fresh-looking’ lunar craters (those which had not yet slumped and distorted the ratio that he utilised). He compiled 300 measurements of lunar craters from the literature, and measured several dozen others himself. There was a clear trend.

Significantly, Baldwin realised that although most sculpture could be attributed to Imbrium, there was some which seemed to be associated with other ‘circular maria’, from which he concluded that they resulted from individual impacts. Furthermore, the mountains peripheral to Serenitatis must have formed prior to the impact that etched the Haemus with Imbrium sculpture, yet before lava flooded the Serenitatis cavity. This established that Mare Serenitatis formed a significant interval after the impact had excavated the cavity in which it resides. Baldwin (as had Gilbert) believed all the maria to have been formed at the same time and to be associated with Imbrium, which at that time was presumed to have been the greatest impact in lunar history. However, whereas Gilbert envisaged the Imbrium impact splashing out liquid ejecta which pooled in low-lying areas to form the various maria, Baldwin saw there had been a significant interval between the formation of the Imbrium cavity and its being filled in. He proposed that the impact raised a vast dome which remained inflated for long enough to be cratered (for example by Archimedes), then collapsed (forming a system of peripheral arcuate faults) and released a pulse of extremely low viscosity lava that not only filled in the cavity but also burst through the containing walls to spread across the surface and fill in other cavities to create the maria. Irrespective of whether the maria were liquid ejecta or erupted lava, it was evident that the large circular cavities were made by individual impacts over a period of time and that there was a significant interval before the formation of the maria.

Astronomers were not impressed by Baldwin’s arguments, however, and for many years continued to associate the maria with the cavities they occupied.

After reading Baldwin’s book, Harold C. Urey developed an interest in the Moon. But Urey was not particularly interested in the surface features – as a chemist at the University of Chicago who gained the 1934 Nobel Prize for chemistry, he was more interested in the Moon’s composition. He accepted that the craters were impacts and the maria were the by-product of a giant impact, but rejected Baldwin’s inference of a significant interval between the Imbrium impact and the formation of the maria. Urey agreed with Gilbert that the maria were splashes of impact melt, and said that because they were molten they could not have preserved sculpture. He also made the remarkable suggestion that the semicircular Sinus Iridum on the northern margin of Mare Imbrium marked the ‘entry hole’ of the asteroidal body whose impact created the Imbrium cavity.

In 1943 Gerard P. Kuiper began to exploit recent technical developments to make observations of bodies in the solar system. He essentially had the field to himself, at least in professional circles, and was able to make a series of discoveries. In 1953 he turned his attention to the Moon. Although photography was the norm, he mounted a binocular eye-piece on the 82-inch reflector of the McDonald Observatory in Texas to exploit moments of exceptional ‘seeing’ to discern details of the lunar surface that

would have been blurred in photographs. In his first paper on the subject, in 1954, he argued that in the case of a body of the Moon’s size, radiogenic heating would have caused sufficient melting for dense minerals to sink to create a core and lightweight minerals to rise to form a crust. This thermal differentiation would become known as the ‘hot Moon’ hypothesis. As volcanism is a means of enabling heat to escape from the interior, Kuiper argued that the maria were formed by lava upwelling at various times from deep fractures in the floors of the cavities excavated by major impacts.

In 1891, while studying the desert between Flagstaff and Winslow in Arizona in which the Canyon Diablo meteorites had been recovered, G. K. Gilbert inspected the circular hole known as Coon Butte. It was 1.2 km in diameter, had a rim which rose 45 metres above its surroundings, and a floor lying 200 metres below the rim. If it marked the site of an impact, then, he reasoned, there might be a large iron meteorite beneath its floor. A buried iron mass should be detectable by its magnetic signature, but there was no such indication. He concluded that the hole was a marr, made some 50,000 years ago when magma caused underground ice to flash to steam and blast a hole in the overlying rock. Nevertheless, in 1903 mining engineer D. M. Barringer began to drill in search of the meteorite, to no effect. In 1916 E. J. Opik realised that a cosmic impact was such a violent event that the projectile would be vaporised, but he published in an Estonian journal and his insight passed unnoticed. In 1924 A. C.

Gifford independently came to the same conclusion and published in a New Zealand journal that had a broader readership. Opik and Gifford both realised that high­speed impacts always create circular craters because whilst momentum is a vector, energy is not, and as the projectile hits the surface it essentially explodes, liberating energy in a symmetric manner and forming a circular crater. Furthermore, they realised, the crater is always much larger than the projectile. If Coon Butte was an impact crater, then the only relic of the projectile was the field of Canyon Diablo meteorites which littered the surrounding desert.

When Eugene M. Shoemaker joined the US Geological Survey in 1948 he already had an interest in the Moon. In 1949 he made a review of the literature and turned up both Gilbert’s paper and Baldwin’s recently released book, both of which advocated the impact hypothesis. In 1955 he studied two craters about 100 metres in diameter created by underground nuclear tests at the Nevada Test Site to investigate how such explosions shocked and dispersed rock. He was impressed by their resemblance to lunar craters. In 1957, with Gilbert’s analysis in mind, he began a study of Coon Butte. He had already done the field work for his PhD thesis on salt structures, but had never gotten around to writing it up. After hearing Shoemaker give a seminar on his study of Coon Butte, his advisor at Princeton, Harry Hess, suggested that he use that as the basis of his thesis. Shoemaker put in some more field work, wrote it up, and, despite it being rather on the short side for the purpose, submitted it in 1959. The fact that the crater was recent and in a desert environment made the manner in which it was excavated readily evident. In particular, the strike had not just penetrated the surface and pushed the rock aside, as Gilbert imagined; the process, as Opik and Gifford had inferred, was explosive. Significantly, Shoemaker found that two shock waves were involved: one vaporised the projectile, and the other propagated into the ‘target rock’, compressing it so thoroughly that the rock reacted just as if an explosion had occurred beneath it. In his field work Shoemaker methodically traced how the rim and the ejecta blanket formed by the stratigraphy being flipped into an inverted sequence around a circular ‘hinge’, in the process making a hole much wider than the projectile.[5]

Early in 1960 L. R. Stieff of the US Geological Survey in Washington DC set out to obtain NASA funding for an investigation of lunar geology. NASA deliberated. In 1953 Loring Coes had produced a new very dense mineral using a hydraulic press to squeeze quartz. This ‘shocked quartz’ was named coesite. In 1956 H. H. Nininger had suggested searching for coesite at Coon Butte, but this was not done. In 1960 Stieff obtained samples of rock taken from Coon Butte which were in the archive of the Smithsonian Institution in Washington DC to enable him to say to NASA that the Survey was already at work on craters. Ed Chao identified coesite using X-ray diffraction, which proved Coon Butte to be an impact crater. A press statement was released to this effect on 20 June. When Chao wrote the scientific paper, the Survey

added Shoemaker and his assistant Beth Madsen as co-authors to imply that it had a team of specialists at work. When the paper was published in Science in July I960, Shoemaker was on his way to present a paper about Coon Butte to the Geological Congress in Copenhagen. The Rieskessel in Bavaria is a 24-km-diameter structure with the town of Nordlingen at its centre. Although widely believed to be volcanic, a study in 1904 had suggested that the circular structure might mark an impact, and its characteristics had led Baldwin to classify it as such. Shoemaker examined samples of quartz from a quarry. To his trained eye, using no more than a hand-lens, the rock showed evidence of shock. The next day he airmailed samples to Chao, who called straight back to confirm that coesite was present. In giving his paper in Copenhagen about Coon Butte, Shoemaker announced the Rieskessel finding.

With the two structures having been shown to be impacts, NASA finally released the funding to enable the Survey to undertake its lunar studies, and on 25 August the Astrogeologic Studies Group was established at the Menlo Park office, south of San Francisco, with Shoemaker in charge. A year later, in 1961, it became the Branch of Astrogeology. In March 1962 Shoemaker decided to move his team to Flagstaff. The move began in December, but some people refused to relocate and were allowed to remain at Menlo Park.

STRANDED

After Ranger 1 passed its qualification tests at JPL in May 1961, Oran Nicks, Chief of Lunar Flight Systems at NASA headquarters, authorised its transportation to Cape Canaveral, where the Air Force had assigned Hangar AE to the project. The launch window ran from 26 July to 2 August. In late June the Atlas was erected on Pad 12, the Agena added, and the spacecraft in its aerodynamic shroud installed to complete the stack. The combined systems tests of the fully assembled space vehicle were concluded on 13 July.

The countdown was delayed three days by a variety of problems, and was unable to start until the evening of 28 July with the intention of launching at dawn the next day, but a problem with the Cape’s electrical power supply meant that the clock had to be halted with 28 minutes remaining. After two other counts were frustrated, the attempt to launch on 2 August was abandoned when, as high voltage was applied to the spacecraft’s scientific instruments for calibration purposes, an electrical failure caused the explosive bolts to fire to deploy the solar panels inside the shroud. The spacecraft had to be retrieved and returned to the hangar. It was concluded that there had been an electrical arc to the spacecraft’s frame, but the precise source was not evident. The damaged parts were replaced. The launch was rescheduled for the start of the window for the next lunation.

The countdown began on the evening of 22 August and ran smoothly to liftoff at 10:04:10 GMT the next morning. With Ranger 1 on its way, James Burke became Mission Director at the Hangar AE command post.

The Atlas ignited its sustainer, the two side-mounted boosters and the two vernier control engines, and was held on the pad until verified to be running satisfactorily. For the first 2 seconds the vehicle rose vertically, and then it rolled for 13 seconds to swing its guidance system onto the flight azimuth. After 15 seconds the autopilot pitched the vehicle in that direction so as to arc out over the Atlantic. When a sensor detected that the acceleration had reached 5.7 times that of

Earth gravity,[20] about 142 seconds into the flight, the Atlas shut off its boosters, and 3 seconds later jettisoned its tail to shed 6,000 pounds of ‘dead weight’. The sustainer engine continued to fire. In the boost phase, the vehicle had been tracked by a radar at the Cape to enable the Air Force to calculate its initial trajectory, and as the sustainer flew on it acted upon steering commands radioed by the ground. When the sustainer shut down, the two verniers on the side of the Atlas fired as appropriate to refine the final velocity. As it did not have the power to insert the Agena directly into orbit, the upper stage was to be released on a high ballistic arc. Once free, the Agena, now above the dense lower atmosphere, jettisoned the aerodynamic shroud to shed dead weight, and ignited its engine. ft then achieved the desired circular parking orbit at an altitude of 160 km. Meanwhile, the Air Force’s computer processed the tracking provided by the radars of the downrange stations of the Eastern Test Range in order to calculate the length of time the Agena should spend in parking orbit and the parameters required for its second manoeuvre. This information was transmitted to the vehicle.

The plan for this test flight was for the Agena В to use its second burn to enter an elliptical orbit with an apogee of 1 million km, far beyond the orbit of the Moon, and for simplicity the orbit would be oriented not to venture near the Moon. The primary objective was to evaluate the spacecraft’s systems in the deep-space environment, in particular its 3-axis stabilisation using Earth, Sun and star sensors, the pointing of its high-gain antenna, and the performance of the solar panels. Each Block f Ranger was expected to have an operating life of several months, and to provide worthwhile data for the sky scientists.

After its second burn, the Agena was to fire explosive bolts in order to release the spacecraft, which would be pushed away by springs. Then the spent stage was to use its thrusters to make its trajectory diverge. Radio interference prevented the tracking site at Ascension fsland in the South Atlantic from monitoring the reignition. When Johannesburg reported detecting the spacecraft several minutes ahead of schedule, it became evident that the second burn had failed and the spacecraft was still in a low orbit. When Goldstone picked it up, the orbit was calculated to have a perigee of 168 km and an apogee of 500 km. Although the Agena had reignited, it had shut down prematurely and then released the spacecraft. ft was encouraging that the spacecraft had deployed its solar panels, locked onto the Sun, rolled to acquire Earth and then deployed its antenna, but because it was ‘stranded’ in a low orbit it soon entered the Earth’s shadow and lost both power and attitude lock. On re-emerging into sunlight it fired its thrusters to restabilise itself. This occurred on every shadow passage, with the result that after only one day the nitrogen was exhausted and, unable to stabilise itself to face its solar panels to the Sun, the battery, intended only for launch and the brief midcourse manoeuvre, expired. The inert spacecraft re-entered the atmosphere on 30 August.

A study of the telemetry tapes confirmed that the Agena reignition sequence had started at the proper time, but almost immediately the flow of oxidiser had ceased. The small amount of oxidiser which had entered the engine gave the 70-m/s velocity

increment that slightly raised the apogee. The premature cutoff was classified as a one-off failure.

Although Ranger 1 flew in an environment different to that intended, its designers were encouraged that it had correctly deployed its appendages and (repeatedly) been able to adopt cruise attitude. But the sky scientists received nothing of value from the mission.

On 5 October, as a result of lessons learned from Ranger 1 when various lines of authority had penetrated the Space Flight Operations Center, Marshall Johnson was appointed Chief of the Space Flight Operations Section and, with it, sole authority to direct the control team while a mission was underway.

The launch window for Ranger 2 was 20-28 October 1961. The tests on the fully assembled space vehicle on Pad 12 were completed on 11 October. The countdown began on time in the evening of 19 October, but was scrubbed with 40 minutes on the clock owing to a fault with the Atlas. Although this was readily repaired, the fact that another Atlas was due to leave from another pad the next day meant Ranger 2 had to wait. The countdown on 23 October was abandoned because of another issue with the Atlas. At this point, a Thor-Agena B launched from Vandenberg Air Force Base in California was lost as a result of the failure of the hydraulics of the Agena’s engine, and NASA decided to await the outcome of that investigation. The problem was diagnosed and fixed in time for the next window, and Ranger 2 lifted off on the first attempt at 08:12 GMT on 18 November. As before, the spacecraft rose above the horizon at Johannesburg early, indicating that the second burn had failed – this time without even producing a modest apogee. Ranger 2 performed perfectly, but it was doomed and re-entered the atmosphere on 19 November.

An Air Force analysis of the telemetry indicated that the roll gyroscope of the Agena B’s guidance system had been inoperative at liftoff, most probably due to a faulty relay in its power supply. The attitude control system had compensated for the roll control failure by using its thrusters, and in so doing had exhausted the supply of gas. As a result, the Agena had tumbled in parking orbit. This caused the propellants to slosh in their tanks, which in turn prevented them from flowing into the engine when it tried to reignite. On 4 December 1961 the Air Force informed NASA of its findings, and Lockheed promised to report within a month on how it would fix the fault. When NASA decided in December 1959 to use the Agena B, it had presumed the Air Force would have worked the bugs out of the vehicle by the time it was needed, but only one had been launched prior to Ranger 1 and, in effect, NASA was testing it for the Air Force!

Although some aspects of the Block I tests had not been achieved, the engineers at JPL were encouraged that on both occasions the spacecraft had worked as well as could be expected in the circumstances. If the Agena was fixed as soon as Lockheed hoped, then it should be possible to proceed with Ranger 3 as planned.

Since Surveyor 2 was essentially complete at the time of the first mission, it was identical to its predecessor. Upon the surprising success of Surveyor 1, NASA opted not to postpone the second mission to install scientific instruments. It duly lifted off from Pad 36A at 12:32:00 GMT on 20 September 1966 on a direct-ascent trajectory with the objective of landing in Sinus Medii.5 In general, this was much rougher – looking than the area in Oceanus Procellarum assigned to Surveyor 1. This time, it was intended to operate the downward-looking TV camera during the approach in order to gain a sense of perspective of the landing site.

The translunar injection trajectory would intercept the Moon just northeast of the crater Mosting on the western margin of Sinus Medii, 142 km from the centre of the 60-km target circle. The sequence for the 31.5-ft/sec midcourse manoeuvre began at T+15h 42m with an interrogation to verify the readiness of the vehicle’s systems. At 16h 12m the spacecraft initiated a roll of +75.3 degrees, followed 5 minutes later by a yaw of +11.5 degrees. This successfully oriented the vehicle for the burn. The burn was started on command at 16h 28m but vernier no. 3 failed to ignite. After the specified duration of 9.8 seconds, the system shut down. The asymmetric thrust had left the vehicle spinning about one axis at 1.22 revolutions per second, with this axis precessing in 12 seconds. This saturated the gyros in the minus pitch, plus yaw and minus roll directions. The flight control system set about regaining stability utilising the attitude control thrusters. After 7 minutes the precession had been cancelled. But after 14 minutes, with a residual spin around the main axis of 0.85 revolutions per second and with the jets having consumed half of the nitrogen supply, a command was sent from Earth to inhibit the system and save the remaining gas for use in the event that the problem involving vernier no. 3 could be overcome, at which time the verniers would be used to stabilise the vehicle.

In fact, this was site I-P-5 on Lunar Orbiter 1’s target list.

Deep Space Instrumentation Facility automatic gain control variations served to document the initial tumbling of the Surveyor 2 spacecraft.

SOLENOID-OPERATED PROPELLANT VALVE

OXIDIZER TANKS

HELIUM TANK

RELIEF VALVE

FUEL TANKS

A simplified depiction of the Surveyor spacecraft’s vernier propulsion system.

Detail of an engine of the Surveyor spacecraft’s vernier propulsion system.

The solar panel was unable to provide power while the vehicle was tumbling, so time was of the essence. It was apparent that verniers no. 1 and 2 had delivered the specified thrust during the manoeuvre, but no. 3 had delivered no thrust at all. It was decided to command a 2-second firing in an effort to clear vernier no. 3. This was done at 18h 56m and again at 19h 18m, but without success. In case the fault was a stuck flow regulator valve, the system was commanded to pulse five times for a duration of 0.2 seconds at 5 minute intervals starting at 31h 12m and then attempt another 2-second firing – again in vain. This sequence was repeated at 26h 28m, 37h 29m, 38h 45m and 39h 45m – each time with no effect. At 41h 11m an attempt was made to fire the engine at a ‘harder’ start and a higher thrust for 2 seconds. Because the other two verniers were participating in these tests, by this point the spin rate had increased to 1.54 revolutions per second. At 43h 13m a new sequence was initiated in which the engines were pulsed five times for 0.2 second with 1 minute between firings, as a preliminary to a 20-second firing. Although this time the temperature of vernier no. 3 increased somewhat, the engine did not respond properly.

Although the spacecraft was tumbling out of control, it was decided to undertake a series of tests to obtain engineering data on its subsystems, concluding at 45h 02m with a command to trigger the retro sequence. Contact was lost 30 seconds into the retro-rocket’s burn. The inert vehicle would have struck the Moon several hundred kilometres southeast of Copernicus.

The post-flight investigation by propulsion engineers of JPL, NASA, Hughes and Thiokol decided that there had been no combustion in vernier no. 3 at the attempted midcourse manoeuvre, and that although fuel had flowed into the engine the oxidiser had not. As it was not possible to determine the root cause of the failure, a number of revisions were introduced for Surveyor 3 designed to provide better diagnostics of the vernier propulsion system, both during pre-flight testing and in flight.

MOON ROCKET

On 19 January 1959 NASA took over the Air Force’s contract with Rocketdyne for the development of the F-1 kerosene-burning engine. The prototype was test fired on

10 February 1961. By sustaining 1.55 million pounds of thrust for several seconds, it broke the record for a single-chamber engine by a considerable margin. On 9 April 1961 it was announced that the engine had achieved 1.64 million pounds of thrust. On 26 May 1962 the engine was fired at full power for its intended operating time of 150 seconds. Meanwhile, Rocketdyne began the development of the 200,000-pound- thrust hydrogen-burning J-2 engine that was to power the upper stages of the Saturn launch vehicle. The first full-duration test of this engine was on 27 November 1963. The Douglas Aircraft Corporation fired an S-IVB stage utilising a single J-2 engine at full power for 10 seconds on a static rig at its Sacramento facility on 4 December 1964. But it was a ‘battleship’ variant (equivalent to a ‘boilerplate’ for a spacecraft) having tankage made of thick stainless steel instead of the lightweight aluminium of the operational vehicle. On 7 December 1964 the first S-IVB mockup – which was accurate in terms of mass, centre of gravity and structural stiffness, but with models of the engine and other systems – was delivered to the Marshall Space Flight Center for stress testing. On 16 April 1965 the first S-IC stage utilising five F-1 engines was test fired for several seconds at NASA’s Mississippi Test Facility. On 24 April the S-

11 stage utilising five J-2 engines was test fired at Rocketdyne’s facility at Santa Susana in California. On 5 August the S-IC made a full-duration test during which it responded to steering commands provided by the blockhouse. On 9 August the S-II made its first full-duration firing. That same day the first production version of the S-IVB was tested, and on 20 August it was fired for 3 minutes, shut down for half an hour and reignited for almost 6 minutes in a simulation of its role on a lunar mission.

Unfortunately, by early 1966 the development of the S-II had slipped. In an effort to recover, North American Aviation hired a new manager, Robert E. Greer, who took a team of engineers to the Mississippi Test Facility. On 23 April 1966 the S-II was successfully fired for 15 seconds, but faulty instrumentation caused premature

cutoffs on 10, 11 and 16 May. It fired for 150 and 350 seconds in tests on 17 and 20 May. But fires broke out in two places on the vehicle in a test on 25 May, and as the stage was being removed from the stand three days later its hydrogen tank exploded, damaging the facility and injuring five people. George Mueller in Washington began to send weekly progress reports on the S-II to company president Leland Atwood, at one point advising him that the S-II had an excellent chance of replacing the LM as the ‘pacing item’ in the program.

But then the fire that killed the Apollo 1 crew during a supposedly routine test of the spacecraft on 27 January 1967 halted the program in its tracks. Nevertheless, the time taken to redesign the CSM provided the opportunity for the development of the Saturn V and the LM to catch up.

On 17 April 1967 the Manned Spacecraft Center proposed a minimum of three manned Saturn V missions involving both the CSM and the LM prior to attempting the lunar landing. When George Mueller advocated landing on the third mission, Chris Kraft warned George Low that a landing should not be tried ‘‘on the first flight which leaves the Earth’s gravitational field’’ because flying to the Moon was such a great step forward in terms of operational capability that this should be demonstrated separately, to enable the landing crew to focus on activities associated with landing. Accepting Kraft’s argument, on 20 September Low led a delegation to Washington. Owen E. Maynard, Chief of the Systems Engineering Division in Houston, outlined a step-by-step sequence: (A) Saturn V and unmanned CSM development; (B) Saturn IB and unmanned LM development; (C) Saturn IB and manned CSM evaluation; (D) Saturn V and manned CSM/LM joint development; (E) CSM/LM trials in an Earth orbit involving a ‘high’ apogee; (F) CSM/LM trials in lunar orbit; (G) the first lunar landing; (H) further ‘minimalist’ landings; (I) reconnaissance surveys in lunar orbit; and (J) ‘enhanced capability’ landings.[48] This alphabetically labelled series was not a list of flights, as several flights might be required to achieve one mission. Two Saturn V development flights were already scheduled as Apollo 4 and Apollo 6, and the LM-1 flight as Apollo 5. Sam Phillips asked whether a second Saturn V test was really necessary, and Wernher von Braun said the second would serve to confirm the data from the first. If the Saturn V development were to prove to be protracted, then the ‘D’ mission would be done by reinstating the plan in which the CSM and LM would be launched individually by Saturn IBs and rendezvous in orbit. Most of the discussion was devoted to the proposal for a lunar orbital flight ‘‘to evaluate the deep space environment and to develop procedures for the entire lunar landing mission short of LM descent, ascent and surface operations’’. When Mueller argued ‘‘Apollo should not go to the Moon to develop procedures’’, Low said that developing crew operations would not be the

main reason for the mission; there was actually still a lot to be learned about navigation, thermal control and communications in deep space. Although the meeting left this matter undecided, the alphabetic labels soon became common shorthand.

Sam Phillips confirmed on 2 October 1967 that LM-2 should be configured for an unmanned test flight, and directed that LM-3 be paired with CSM-103 for the first manned mission of the complete Apollo configuration.2 Grumman’s latest schedule called for LM-2 to be delivered in February 1968, LM-3 in April and LM-4 in June. On 4 November George Mueller issued the schedule for 1968: AS-204 with LM-1; then AS-502 as the second unmanned test; AS-503 as the third unmanned test, if this proved necessary; AS-206 with LM-2, if required; AS-205 with CSM-101, manned; and AS-504 with CSM-103 and LM-3, manned. On 15 November George Low said that in the event of AS-503 being unmanned, the payload should be the ‘boilerplate’ spacecraft BP-30 and lunar module test article LTA-B.

In April 1957 the National Academy of Sciences awarded Kuiper the funding to start work on a new lunar atlas, and supplementary money was provided later in the year by the Air Force. The resulting Photographic Lunar Atlas was published in I960. The best available photographs were printed on a scale at which the lunar disk spanned 2.5 metres. It formed a striking contrast to the similarly sized map based on visual observations that was published in 1959 by H. P. Wilkins of the Lunar Section of the British Astronomical Association. Although very different in presentation, the two maps were comparable near the centre of the Moon’s disk but even in the best pictures the limb regions were marred by ‘seeing’, and it was in these areas that the visual observers had the advantage. However, the pictures were able to be projected onto a white globe and rephotographed to eliminate foreshortening and thereby gain a new perspective of the limb regions. This Rectified Lunar Atlas was issued in 1963 as a supplement to the 1960 atlas.

In 1959 the Air Force Chart and Information Center in St Louis, Missouri, began to use airbrushing to represent topography on a scale of 1:1,000,000 for a series of Lunar Astronautical Charts. Meanwhile, the Army Map Service issued ‘photomaps’. The US Geological Survey wished to map the Moon geologically. The first step was to identify the various distinct geological units in terms of their textures, delineate their outlines on a ‘base map’, and use the principle of superposition (as defined by Nicolas Steno in 1669) to determine the order of their deposition. The objective was to obtain insight into the history of the lunar surface. In 1960 Robert Hackman of the Photogeology Branch of the Survey in Washington DC demonstrated that it was possible to apply stratigraphic analysis to the Moon. When issued in 1961, his map of what he referred to as pre-maria, maria and post-maria units marked a significant departure from the astronomers’ means of mapping. The superposition relationships suggested to Hackman that the maria were volcanic, not splashes of impact melt. He drew attention to a patch of light-toned material between the Apennine mountains and the crater Archimedes. There was ejecta from Archimedes on this patch, and the dark mare had encroached upon the ejecta. The sequence was clear: the light-toned material was the floor of the cavity created by the Imbrium impact, this had been hit by Archimedes some time later, and the mare had appeared after that. Since the light patch was sufficiently elevated not to be overrun, he named it the Apennine Bench. A factor of two difference in the cratering densities of the bench and the adjacent mare was evidence that a significant interval had elapsed between the Imbrium impact and the appearance of the mare within the cavity.

Meanwhile, Gene Shoemaker had independently made a stratigraphic study of a section of the Moon to demonstrate the technique. Visiting a bookstore shortly after being shown the prototype Lunar Astronautical Chart of the Copernicus area, he had happened across a picture of this area taken by Francis Pease in 1919 while testing the 100-inch telescope at Mount Wilson. It was of sufficient clarity to show craters down to 1 km in diameter, so Shoemaker had it enlarged and set to work. Whereas Hackman had used only pre-maria, maria and post-maria units, Shoemaker mapped seven units, which he named the pre-Imbrian, Imbrian, Procellarian, Eratosthenian

Stratigraphic mapping 29

and Copernican systems. In essence the Eratosthenian and Copernican corresponded to Hackman’s post-maria, but Shoemaker distinguished the Eratosthenian from the Copernican because rays from Copernicus were superimposed on the Eratosthenes ejecta – in effect, the difference was whether a post-mare crater’s rays were fresh, or faded. On 17 March I960 Shoemaker presented a paper showing that whereas much of the material excavated by Copernicus had been ‘hinged’ to produce the rim and adjacent blanket of ejecta, some of the material was hurled ballistically and fell further out, where its impact made distinctive chains of small secondary craters. The secondary craters were less energetic because, to have fallen back at all, the ejecta could not have exceeded the escape velocity – which is an order of magnitude lower than the typical cosmic velocity of material arriving from space. This study not only established Copernicus to be an impact crater, it also refuted the assertion by the advocates of the volcanic origin of craters that the chains of small craters marked eruptions along fractures in the crust.

At the International Astronomical Union Symposium in December 1960, which was a major event for astronomers, Shoemaker and Hackman presented a joint paper entitled Stratigraphic Basis for a Lunar Time Scale. This laid the foundation for how geological units could be recognised on an extraterrestrial surface and placed into a stratigraphic sequence. In the case of Earth the units were identified by studies in the field, but for the Moon they would have to be inferred from overhead imagery – at least until expeditions were made to the lunar surface.

Having established that the maria were formed after the Imbrium impact, it was expected that all maria would be able to be assigned to the Procellarian system, but in late 1963, when patches of mare were found to be stratigraphically younger than craters attributed to the Eratosthenian system, the Procellarian system was dismissed and each mare unit was assigned to the system implied by its particular stratigraphy.

Also in late 1963, the scheme was refined by the introduction of formation names for the geological units. The reason for the change was that a formation name was objective, and did not imply a specific physical process. Also, because a formation defined a terrain type by its texture, it did not require to be contiguous. This was the case for the hummocky material peripheral to Imbrium. It had just been mapped by Richard Eggleton, who had transferred to Shoemaker’s team from the Engineering Geology Branch. It was labelled the Fra Mauro Formation, after a prominent crater within it. Although there was little doubt that it was Imbrium ejecta, to have labelled it as such would have been subjective and would have set a poor precedent.

In September 1961 Gerard Kuiper convinced the Air Force Chart and Information Center to exploit visual observations in compiling the Funar Astronautical Charts, since in moments of good ‘seeing’ the eye can resolve finer detail than is able to be recorded during a photographic exposure. The pictures were to provide the basis for mapping and the visual observations would provide the detail. On joining the team, each ‘astrogeologist’ was assigned a quadrangle to map geologically, in addition to his principal task. As one of the first such recruits, Eggleton provided training for those who followed. Observing time was allotted when the terminator was near the assigned area, to emphasise subtle topography. Those in Arizona used the 24-inch refractor of the Fowell Observatory in Flagstaff,

and those in Menlo Park used the 36-inch refractor of the Lick Observatory on Mount Hamilton near San Jose.

In February I960 the University of Arizona in Tucson established the Lunar and Planetary Laboratory, and made Gerard Kuiper its head. When William Hartmann joined in mid-1961, he assisted the team which was producing the Rectified Lunar Atlas. A major finding was the existence of systems of concentric rings. These had not been recognised from Earth owing to foreshortening, but when viewed from an ‘overhead’ perspective they stood out clearly. The most spectacular case surrounded a small dark patch which was itself only glimpsed at times of favourable libration and had been named Mare Orientale for the reason that it was on the eastern limb – a rationale rendered obsolete by the decision of the International Astronomical Union in August 1961 to switch the east and west limbs! On realising that the multiple-ring structures were a distinct class of geological feature, Hartmann introduced the term ‘basin’. He wrote up the discovery with Kuiper and published in-house on 20 June 1962 in the paper Concentric Structures Surrounding Lunar Basins. Soon, similar patterns were identified in degraded states around a dozen ‘circular maria’. This insight revealed the true violence of a basin-forming impact. Namely, a vast impact excavated a cavity, forming one or more concentric rings of mountains composed of individually faulted blocks with their steep ‘fronts’ facing inwards, whilst also piling up material in blankets immediately beyond and etching sculpture as ballistic ejecta fell further out – all of which occurred literally in an instant. Some time later, and perhaps after a considerable interval, lava rose through deep fractures in the cavity of the basin to flood it, often to a depth sufficient to submerge the inner rings. As a result, a basin consisted not only of the cavity, but also the concentric rings, the inner blankets of ejecta and the outer sculpture. The clear fact that a basin was distinct from the mare that formed later was highlighted by the discovery of concentric rings around large craters which had not been fill with mare. Since multiple-ring structures were not of volcanic origin, this lent support to the case for smaller craters also being of impact origin. In fact, although it was recognised early on that sculpture was gouged by the fall of material thrown out on shallow-angle trajectories, it was a while before it was realised that a lot of basin ejecta must have struck at a high angle and, consequently, many well-known sizeable craters are probably not primary impacts but secondaries from basin-forming events. By 1963, photogeologists were working to determine the order in which the dozen or so recognised basins were formed.

In just a few years, therefore, an examination of the Moon by geologists applying standard mapping methods had provided insights into the history of the lunar surface which had eluded astronomers for centuries.