Category Paving the Way for Apollo 11

Soviet activity

THE SECOND GENERATION

After the success of Luna 3, the Soviets developed a new spacecraft designed to deliver a capsule to the lunar surface using the rough landing technique. Luna 4 was launched at 08:16 GMT on 2 April 1962, and after cruising in parking orbit it set off for the Moon. After an ineffective midcourse manoeuvre, the 1,422-kg vehicle made a flyby at 13:25 on 5 April at a range of 8,500 km and passed into solar orbit. After several further failures, the Soviet Union conducted a deliberate flyby mission.

FILLING THE GAP

Zond 3 lifted off at 14:38 GMT on 18 July 1965. After parking orbit, it was sent on a trajectory to pass by the illuminated leading limb of the Moon. Imaging began at 01:24 on 20 July at an altitude of 11,570 km and ended at 02:32 at 9,960 km, with the closest point of approach at 9,220 km. It had been intended to launch this probe in 1964 as a companion to Zond 2 on a mission to Mars, but it was held back. The pictures were not transmitted until the narrow-beam of the high-gain antenna was able to lock onto Earth, which occurred on 29 July at a range of 2.2 million km. The objective of this flight was to test deep-space communications for an interplanetary mission, and the Moon was merely a convenient photographic target. It transmitted two dozen pictures of Oceanus Procellarum and around onto the far-side to view the area which had not been visible to Luna 3.

The results indicated that although there were few maria on the far-side, and those were small, there were multiple-ring structures which for some reason had not been flooded by lava. The Orientale basin was seen in its entirety for the first time, since even at the most favourable libration barely half of it was observable in reprojected telescopic pictures. In addition to the concentric rings, there were radial patterns in evidence. There was a small patch of mare material inside the central ring, and small patches between the rings, but otherwise the entire structure was ‘on display’ in its

magnificence. It boggled the mind that Earth must once have been disfigured by such structures!

AMERICA TRIES FOR THE MOON

Explorer 1 restored national honour, but the Department of Defense was deeply concerned that the Soviet launch vehicle was so much more powerful than its own. On 7 February 1958 President Eisenhower created the Advanced Research Projects Agency headed by Roy W. Johnson, who would report directly to the Secretary of Defense. Its was to develop national goals and coordinate, but not itself conduct, the necessary research.

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The Explorer 1 satellite, installed atop the drum-like second stage of the Juno I launch vehicle.

 

After the successful launch of Explorer 1, W. H. Pickering (farthest away), James van Allen and Wernher von Braun hold aloft a full-scale model of the spacecraft.

 

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Wernher von Braun poses beside the framed Huntsville Times announcing the successful launch of America’s first satellite.

 

On 21 October 1957, three weeks after the launch of Sputnik, W. H. Pickering, since 1954 Director of the Jet Propulsion Laboratory (JPL) in Pasadena, California, had proposed that a spin-stabilised probe be launched towards the Moon, possibly as soon as June 1958.2 The purpose of this Project Red Socks would be to produce “a significant technological advance over the Soviet Union” that would enable America to “regain its stature in the eyes of the world”. The Pentagon sent the proposal to Roy Johnson, who was eager “to surpass the Soviet Union in any way possible”. The fact that the Soviets had not yet announced a lunar flight prompted him to accept the challenge of America being the first to do so. Neil H. McElroy, who had superseded Charles Wilson as Secretary of Defense just a few days before the Soviets launched Sputnik, announced on 27 March 1958 the US decision to “determine our capability of exploring space in the vicinity of the Moon, to obtain useful data concerning the Moon, and provide a close look at the Moon”. It would be undertaken as part of America’s contribution to the International Geophysical Year.

The project was named Pioneer. To pre-empt calls for it to be assigned to one or other of the services, the Air Force and Army were to work in parallel on their own contributions. The Air Force would modify its Thor missile to use the upper stages made for Vanguard. Meanwhile, the Army, just as it had used the Jupiter-C variant of the Redstone in a configuration named Juno I to launch Explorer 1, would fit its Jupiter missile with upper stages by clustering solid rockets to create the Juno II. As conceived, there would be five flight opportunities: three for the Air Force and two for the Army.

The Air Force assigned the technical direction of its part of the project, including the provision of the payload, to the Space Technology Laboratories of Redondo Beach, California. This company served as the contract manager for the Air Force’s ballistic missile program. The plan was for the launch vehicle to undertake a ‘direct ascent’ from Earth and release the probe on a trajectory that would enable it to enter orbit around the Moon. The design of the probe was finished in June 1958, just three months after the project was given the go-ahead. It comprised a pair of squat cones with their bases on a short cylindrical section. The body was 74 cm in diameter and 46 cm tall. It was to be spun at 200 rpm for stability. The mass of 38 kg included the solid-fuelled retro-rocket to brake into lunar orbit and 18 kg of scientific payload. The Advanced Research Projects Agency stipulated that the probe have an imaging system, but the scientists considered the primary payload to be their instruments to follow up the discovery by Explorer 1 of charged-particle radiation near Earth, and in this case the ‘particles and fields’ instruments were a magnetometer to measure magnetic fields in cislunar space and a micrometeoroid impact counter.

At 12:18 GMT on 17 August 1958 the Thor-Able lifted off from Pad 17A at Cape Canaveral, but the seizure of a turbopump bearing 77 seconds later brought the

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A model of the Pioneer 1 satellite.

flight to a premature end. Intended to be named Pioneer 1, this inauspicious start entered the history books as Pioneer 0.

Meanwhile, Lyndon Johnson began to argue for a new government agency to run a major space program – it featured in a speech he gave in January 1958 in which he ‘signalled’ his intention to seek the party’s nomination to run for the presidency in I960.

As Eisenhower’s Special Assistant for Science and Technology, James R. Killian chaired the President’s Science Advisory Committee. This reported ‘‘space’’ to be ‘‘inevitable’’, citing as reasons: (1) defence implications, (2) national prestige, and (3) opportunities for scientific research. The Committee warned that if the Pentagon was allowed to run a ‘national’ program, grandiose proposals would jeopardise the scientific work. It would be better to organise the scientific program independently of the military. The Committee recommended assigning it to a body modelled on the National Advisory Council for Aeronautics, which had been established in 1915 to coordinate aeronautical research. On 2 April 1958 Eisenhower signed an executive order calling for the National Advisory Council for Aeronautics to be subsumed into the National Aeronautics and Space Administration (NASA) in order to manage the national civilian space program. He also created the National Aeronautics and Space Board to advise on policy. The National Aeronautics and Space Act was passed by Congress on 16 July, and signed into law on 29 July. The new agency inherited all of its predecessor’s facilities: the Langley Aeronautical Laboratory at Langley Field, which had been established in Hampton, Virginia, in 1917, together with its Pilotless Aircraft Research Station at Wallops Island; the Ames Aeronautical Laboratory at Moffett Field, established in 1939 in Mountain View, California; the Lewis Flight Propulsion Laboratory, which was established in 1941 in Cleveland, Ohio; and the High-Speed Flight Station, established in 1949 at Muroc Field in the high desert of California and renamed Edwards Air Force Base in 1950.[6] Although NASA’s remit

was much broader than that of its predecessor, it did not immediately gain control of the rocketry expertise at either JPL or the Army Ballistic Missile Agency.[7]

On 8 August Thomas Keith Glennan, for the last decade President of the Case Institute of Technology in Cleveland, Ohio, was nominated as NASA Adminis­trator. Hugh Latimer Dryden, Director of the National Advisory Council for Aeronautics since 1947, was to provide continuity by serving as his deputy. Congress confirmed the appointments within days. When NASA became operational on 1 October 1958, it inherited the Pioneer project from the Advanced Research Projects Agency.

The Air Force’s second probe rose from Pad 17A at 08:32 GMT on 11 October. The Thor performed flawlessly, but a guidance error caused the second stage to shut down prematurely. The third stage took over, but was incapable of making up the 250-m/s shortfall in velocity. Pioneer 1 was successfully released, but upon attaining an altitude of 115,350 km, about one-third of the way to the Moon, it fell back and burned up in the atmosphere on 13 October. The trajectory precluded the electronic TV imager from viewing the Moon. The scientists welcomed the data provided by the magnetometer and micrometeoroid detector. This flight also had an ion chamber supplied by James van Allen, but it developed a leak and the data was difficult to interpret.

The scientists augmented the third probe with a proportional counter supplied by the University of Chicago. The Thor-Able lifted off at 07:30 GMT on 8 November 1958. The first two stages worked, but the engine of the third stage failed to ignite. The trajectory of Pioneer 2 peaked at an altitude of only 1,550 km and it fell back into the atmosphere 6.8 hours after launch, having returned no significant data.

The Army’s probe was developed by JPL, which had supplied Explorer 1. It was a cone mated at its base to a cylindrical section, stood 51 cm tall and had a maximum diameter of 24 cm. Whereas the Air Force had used an optical-electronic sensor that scanned as the probe rotated, JPL designed a camera whose film would be wet – developed, scanned optically and transmitted to Earth for reproduction by facsimile methods. The image was to be taken from a lunar altitude of 24,000 km, with the shutter being triggered when a photocell noted the presence of the Moon in its field of view. The first flight was to test this sensor. Its successor would carry the entire camera and loop around the back of the Moon to take a picture of the mysterious far-side at a resolution of 32 km. However, when studies by Explorers 3 and 4 revealed that the charged-particle radiation in the Earth’s vicinity would ‘fog’ the film of the Moon-bound probe, the Army cancelled the film camera in August 1958

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The Thor-Able launch vehicle with Pioneer 1 being prepared for launch on 11 October 1958.

 

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Technicians prepare the Pioneer 3 satellite.

in favour of the development of a lightweight slow-scan TV camera and a magnetic tape recorder to store the image for transmission.

A Juno II launched Pioneer 3 from Pad 5 at 05:45 GMT on 6 December 1958. The probe was intended to make a direct ascent, fly close to the Moon and pass into solar orbit. But the Jupiter first stage shut down prematurely, and the upper stages were unable to make up the 286-m/s shortfall in velocity. The 6-kg probe peaked at an altitude of 102,300 km, fell back and burned up 38 hours 6 minutes after launch. Nevertheless, it produced useful data. In place of the camera, it had a pair of Geiger – Mueller tubes supplied by James van Allen to measure radiation in cislunar space, and these revealed the existence of a second zone of radiation some distance above the one already identified: the intensity peaked at 5,000 km and again at 16,000 km, then diminished to the probe’s peak altitude. At van Allen’s suggestion, the imaging system was deleted from the second probe to enable his instrument to fly again. In addition, lead shielding was installed on one of the Geiger-Mueller tubes to screen out the low-energy charged particles. With the imaging cancelled, the trajectory was revised from a loop around the back of the Moon to a flyby into solar orbit – as had been intended for the first probe. After lifting off at 05:45 GMT on 3 March 1959, Pioneer 4 successfully flew by the Moon at 22:25 on 4 March. Unfortunately, the range of 60,500 km was twice that planned, with the result that the photocell test

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The Juno II launch vehicle with Pioneer 4 is prepared for launch on 3 March 1959

failed – but as there was no follow-up probe available to carry the camera this was of little consequence. The Geiger-Mueller results provided further support for the hypothesis that the Earth’s magnetic field traps charged particles that originate from the Sun.5

The idea of streams of particles flowing outward from the Sun was first suggested by British astronomer Richard C. Carrington. In 1859 he made the first observation of what would later be named a solar flare. The occurrence of a geomagnetic storm the following day prompted him to suspect a connection. In the 1950s the German scientist Ludwig Biermann cited the fact that the tail of a comet always points away from the Sun irrespective of the comet’s direction of travel, as evidence that the Sun emits particles. In 1958 Eugene Parker in America postulated a supersonic flow of high-energy charged particles, primarily protons and electrons, streaming from the corona in the form of a ‘solar wind’. The presence of charged particles circulating in the Earth’s magnetic field strongly supported this hypothesis.

Orbiters for science

GLOBAL MAPPING

In March 1967 the Surveyor/Orbiter Utilisation Committee agreed that since the first three Lunar Orbiter missions had achieved that project’s commitment in support of Apollo, the next should “perform a broad systematic photographic survey of lunar surface features in order to increase scientific knowledge of their nature, origin and processes, and to serve as a basis for selecting sites for more detailed scientific study by subsequent orbital and landing missions’’. This plan had been conceived at the Summer Study on Lunar Exploration and Science held in Falmouth, Massachusetts, between 19 and 31 July 1965, in the hope that the opportunity to undertake it would arise. The primary objective was to obtain contiguous coverage of at least 80 per cent of the near-side of the Moon at a resolution better than 100 metres. In fact, if the project’s priority had not been to reconnoitre specific areas in support of Apollo, the scientists would have started by mapping on a global basis.

To map in this way, the spacecraft would require to fly in a near-polar orbit with a perilune altitude fifty times greater than its predecessors, and as it would spend most of its time in sunlight the heat-rejection capacity of its protective base was enhanced by the installation of several hundred small quartz mirrors.

Lunar Orbiter 4 lifted off at 22:25:01 GMT on 4 May 1967. A midcourse burn of 60.8 m/s was required to deflect the trajectory away from the equatorial zone for a polar trajectory. This 53-second manoeuvre was made at 16:45 on 5 May. A further refinement was cancelled.

At 15:09 on 8 May the engine was reignited for 502 seconds to slow by 660 m/s and enter an orbit of 2,706 x 6,114 km with a period of 12 hours. The orbital plane was inclined at 85.5 degrees to the lunar equator, and oriented to enable the ground track to follow the migrating terminator to highlight topographic relief. The phase of the Moon was ‘new’ on 9 May; ‘first quarter’ would occur on 17 May and ‘full’ on 23 May. The photographic mission began at 15:46 on 11 May, while passing south to north on the eastern limb, and viewed Mare Australe and Mare Smythii. Given the

The Lunar Orbiter 4 imaging sequence was designed to provide comprehensive overlap in the high-resolution coverage.

processor. It would also risk moisture in the hermetically sealed compartment condensing on the lenses. It soon became evident that the longer the exposed film spent in the loopers before being processed, the greater was the light pollution. Tests by Boeing indicated that it should be safe to repeatedly partially close and fully open the door. When this was done, the light leakage was reduced to an acceptable level. To overcome the loss of image contrast arising from dew on the lenses, the vehicle was briefly oriented at the start of each orbit to let the heat of the Sun clear the condensation. By the time that the difficulties were completely overcome, the plane of the orbit had migrated about 60 degrees in longitude. However, it proved possible to rephotograph much of this area again from apolune later in the mission.

On 20 May the drive mechanism of the film scanner began to misbehave. Clifford Nelson, the Project Manager at Langley, debated the irrevocable step of cutting the Bimat strip immediately versus continuing in the hope that all would be well. Jack McCauley argued for extending the contiguous coverage beyond the western limb to document the Orientale basin. Nelson agreed. When the scanner problem worsened on 25 May, it was decided to cut the Bimat. Although the photography had reached 100°W, the readout was at only 70°W and the challenge was to coax the remaining

Lunar Orbiter 4 frame M-187 documented the Orientale basin in unprecedented detail.

processed exposures through the scanner in a manner which fooled the faulty logic unit. This task was successfully completed on 1 June.

The resolution of the mapping varied with altitude, but at perilune it was as fine as 60 metres, which was considerably better than was attainable from Earth. The results revealed hitherto unknown geological detail of the near-side polar and limb regions, and also increased to about 80 per cent the project’s coverage of the far-side. Frame M-187, taken from an altitude of 2,723 km, showed the Orientale basin in startling detail. Secondary exposures included westward-looking oblique pictures of Apollo sites. The micrometeoroid experiment had reported two hits. Manoeuvres on 5 and 8 June lowered the orbit to 77 x 3,943 km to approximate that intended for Lunar Orbiter 5 and to obtain selenodesy to assist in the planning of that mission. (Meanwhile, tracking of Lunar Orbiters 2 and 3 was showing that a low perilune would decay unless maintained by engine firings.) Contact with Lunar Orbiter 4 was lost on 17 July, and calculations indicated that its diminishing perilune would have caused it to crash at the end of October 1967. There was no ‘screening’ after this mission, as the images were for scientific research rather than Apollo landing site certification.

Ranger struggles

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

Stranded 91

 

Preparing the Ranger 1 spacecraft.

 

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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.

Apollo picks up the pace

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.

THE RENAISSANCE IN ASTRONOMY

In 1330 AD the Italian scholar Francesco Petrarca coined the term ‘dark ages’ for the centuries of cultural decline in Europe after the fall of Rome in the fifth century. Intellectual development did not resume until the start of the Italian Renaissance in the fourteenth century. During this interregnum, the works of classical Greece and Rome were available only in Arabic translation. On being ‘rediscovered’, they were translated from Arabic into Latin.

In 1505 Leonardo da Vinci, who had exceptional eyesight, drew an impression of the face of the Moon. He interpreted the brighter part to be water, the dark areas as land, and believed that there were clouds. He was the first to explain the old-Moon-in-the-new-Moon’s-arms effect that occurs when the Moon is a narrow crescent. At such times the majority of the Earth’s disk in the lunar sky must be illuminated, and the dark part of the remainder of the lunar disk is dimly lit by sunlight reflecting off Earth. Late in the 13th century, it had been realised that light was bent by passing through a glass lens. The term ‘refraction’ was not invented until some time later. In 1490 da Vinci had speculated upon whether lenses could be used in combination to make an enlarged view of a distant object. In 1504 he conducted experiments, and by 1510 had the optical principle of the telescope.

After further experiments, three years later he described how a concave mirror could produce a magnified image.

As the Renaissance progressed, some of the ancient beliefs were questioned. By the Ptolemaic system, all celestial bodies travelled around Earth on a daily basis, but Nicolaus Copernicus, a Polish canon, realised that this was not entirely true. In his book De Revolutionibus Orbium Coelestium he revived the heliocentric system of Aristarchus of Samos. Copernicus said only the Moon travels around Earth, but he retained circular orbits, deferents and epicycles. The planets, including Earth, are in orbit of the Sun. But knowing that the Church of Rome would construe this to be heresy, he kept silent, and his book was not released until after he died in 1543. His caution was justified, as in 1600 Giordano Bruno was burned at the stake in Rome for arguing in favour of the heliocentric hypothesis.

Johann Kepler was born near Stuttgart in Germany in 1571. He went to Prague in 1600 to assist the Danish astronomer Tycho Brahe, who held the title of Imperial Mathematician to the Holy Roman Emperor Rudolph II. Over a period of 20 years Brahe had compiled a highly accurate catalogue of planetary motions. When Brahe died in 1601, Kepler inherited the title of Imperial Mathematician, together with the archive of observations, which he set about analysing – something that Brahe had never attempted. Brahe was convinced of the view that Earth was central, but Kepler found otherwise. In his book Astronomica Nova, published in 1609, he announced that a planet pursues an ellipse with the Sun at one focus and the other focus vacant. The same applies to the Moon, but with Earth at one of the foci instead of the Sun. Whilst this rendered obsolete the Ptolemaic system with its circular orbits, deferents and epicycles, the Church was reluctant to concede the point.

In fact, Kepler also realised that the speed of a body in its orbit is proportional to its distance from its primary. In the case of the Moon, with Earth at one focus of its orbit, it travels more rapidly at perigee than at apogee. As a result, whilst the rate at which the Moon turns on its axis is fixed and is synchronised with its orbital period, the Moon is sometimes leading and sometimes trailing the mean position of its orbit, at which times we can see a portion of the otherwise hidden hemisphere around first one equatorial limb and then the other. Similarly since the Moon’s orbit is inclined to the Earth’s equator, when the Moon is in the southern sky we can observe slightly beyond its north pole at a time when that is illuminated, and when the Moon is in the northern sky we can see beyond its south pole when that is illuminated. This effect is known as libration. As for the Moon as a body, Kepler introduced the terms ‘terrae’ and ‘maria’ to describe the light and dark areas respectively.

ON THE SURFACE

The Soviet effort to deliver a capsule to the lunar surface using the rough landing technique finally succeeded with Luna 9. This was launched at 11:42 GMT on 31 January 1966. Its mass was 1,538 kg, including the surface capsule. The midcourse manoeuvre was made at 19:29 on 1 February. As with the Block II Ranger, the inability to deal with a lateral velocity component in the descent limited targets to longitudes of about 64°W and fairly near the equator. In this case, the target was in Oceanus Procellarum, near Hevelius. At an altitude of 8,300 km, with about half an hour to go, the spacecraft aligned its main axis to local vertical. The radar altimeter initiated the retro manoeuvre at 18:44:42 on 3 February, at an altitude of 75 km. At 18:45:30, after slowing by 2.6 km/sec, the engine was cut off when a 5-metre-long probe made contact with the surface, and simultaneously the payload was ejected upward and to the side. The bus hit the ground at 6 m/s and its transmission ceased.

The 250-foot-diameter radio dish at Jodrell Bank in England was the largest fully steerable antenna in the world, and it was monitoring the transmission. When the signal ceased, Bernard Lovell, the head of the facility, wrote it off as another failed landing. But the shock-proof 58-cm-diameter spheroidal capsule rolled to a halt and, some 250 seconds after being released, initiated its own transmission. Four petals opened to right and stabilise the capsule and to expose its contents, which comprised a radiation detector and a line-scan TV camera that pointed upward and viewed the landscape using a nodding mirror that could rotate in azimuth.

Between 01:50 and 03:37 on 4 February a panoramic picture was built up line by line and the data transmitted in real-time. Jodrell Bank recorded the transmission. On a hunch, Bernard Lovell asked the local office of the Daily Express to provide a commercial wire-facsimile machine, and the signal was fed into it. Even before the Soviets announced their probe had transmitted a picture, the ‘scoop’ was published in Britain with the headline: From Luna 9 to Manchester – The Express Catches the Moon. Unfortunately, not knowing how to extract the aspect ratio of the image from the telemetry, they had guessed, and caused the horizontal scale to be compressed by a factor of 2.5, and since it was consistent with the popular expectation of the lunar surface, the resulting jagged landscape seemed ‘right’. The ruggedness was further emphasised by the fact that the Sun was just 7 degrees above the horizon and cast very long, very dark shadows. The surface looked like glassy scoriaceous lava that would be very treacherous for an astronaut to walk on – much like the ‘aa’ lava in Hawaii, so named because a person walking on it tends to cry that sound!

When the official version was issued later using the true aspect ratio, the jagged ‘spikes’ were seen to be just rocks resting on the surface, and the scene was rather less dramatic. The capsule had come to rest oriented 16.5 degrees off vertical. The field of view spanned 11 degrees above and 18 degrees below the perpendicular to the capsule’s axis, with a series of 6,000 vertical lines spanning a full 360 degrees of

image66

A model of the Luna 9 spacecraft showing the spheroidal surface capsule attached to the bus, and (right) the capsule in its deployed configuration. The camera is the cylindrical unit on the axis.

image67

Two sections of a panoramic image transmitted by Luna 9. (Courtesy of Philip J. Stooke, adapted from International Atlas of Lunar Exploration, 2007)

azimuth. As the mirror was only 60 cm off the ground, the perspective was very low, with objects in the foreground appearing larger than they were, and the horizon was very close as a result of the capsule having landed in a shallow 25-metre-diameter crater. There was no sign of the bus.

Gerard Kuiper claimed that there were vesicles in the rocks, which supported his idea that the maria were volcanic. As meteors were particles of dust that penetrated

the Earth’s atmosphere, it seemed only reasonable that the airless Moon would have accumulated a blanket of such material, but this did not seem to be the case. Thomas Gold responded to the evident absence of dust (on this patch of mare, where it could reasonably have been expected to be very thick) by suggesting that the ‘rocks’ were not fragments of lava but fine powder which had adhered to form clods. The surface clearly had sufficient bearing strength to support the capsule’s 100-kg mass – but in the weak lunar gravity its weight was one sixth of this value. To the Apollo planners, this was the most significant result of the mission. Gold argued that the capsule was spreading this load across the four deployed panels, and in time it would sink from sight. The geologists of the Branch of Astrogeology inferred that the surface was (to use Harold Urey’s term) gardened by impacts. The site was on a dark geological unit that Jack McCauley, in making the Lunar Astronautical Chart for this area, had interpreted as a pyroclastic blanket with lava flows. Although there was nothing in the image to suggest pyroclastic, it did indeed look like a lava flow, and judging by the sharpness of the rocks and the absence of dust it was relatively young in terms of lunar history.

A second panorama was taken between 14:00 and 16:54 on 4 February, and this showed that the capsule had increased its tilt to an angle of 22.5 degrees, altering the angle of the horizon. Gold claimed this was evidence of the capsule sinking into the dust. The offset had the benefit of facilitating limited stereoscopic analysis. Before the battery expired on 6 February, further partial pans were made to observe how the illumination changed as the elevation of the Sun in the lunar sky increased, thereby demonstrating the value of repeatedly imaging a scene from a fixed vantage point.

SOVIET LUNAR FLYBY

Although the Advanced Research Projects Agency had hoped to beat the Soviets to the vicinity of the Moon, by the time Pioneer 4 became the first American probe to do so this particular race had been won by the Soviets. Luna 1 lifted off at 16:41 GMT on 2 January 1959 on a direct ascent trajectory, and on 4 January flew by the Moon at a range of 5,500 km and passed into solar orbit. In fact, the objective was to hit the Moon, but the Soviets gave the impression that the plan had been to make a flyby. The 1.2-metre-diameter 361-kg spherical probe was not stabilised in flight. Its particles and fields instruments included a magnetometer on a 1-metre-long boom. The transmissions continued for 62 hours, by which time it was 600,000 km from Earth. It detected plasma in interplanetary space, further supporting the existence of the solar wind, but no evidence that the Moon possessed a magnetic field.

NASA EMBRACES LUNAR SCIENCE

The term ‘sky science’ was coined by JPL historian Cargill Hall to encompass the study of the Earth’s upper atmosphere and ionosphere, particles and fields in space and micrometeoroid particles. It included solar and cosmic rays, plasma dynamics and the interaction of the solar and terrestrial magnetic fields. By the late 1950s, sky scientists had a range of instruments with which to pursue their interests. These had been developed and refined initially by balloon-borne packages and, more recently, by sounding rockets. Its members were a cohesive group with impeccable academic pedigrees. By way of the National Academy of Sciences they had played key roles in

The charged particles trapped in the Earth’s magnetic field became known as the van Allen radiation belts.

selecting the experiments for the sounding rockets fired by the United States for the International Geophysical Year, and had dominated planning for the Vanguard and Explorer satellites and Pioneer space probes.[8] As a group, they were not interested in physical bodies such as the Moon other than as sources of magnetic fields, and they were certainly not interested in the geological history of the lunar surface.

In early 1958 ‘planetary scientists’ began a series of informal Lunar and Planetary Exploration Colloquia. The first meeting on 13 May 1958 was jointly sponsored by the RAND Corporation, the California Research Corporation and North American Aviation, and it was hosted by the latter in Downey, California. The three principal objectives were (1) to bring together people of common interest for the exchange of scientific and engineering information; (2) to define the scientific and engineering aspects of lunar and planetary exploration and to provide a means for their long­term appraisal; and (3) to make available, nationally, the collective opinions of a qualified group on this subject.[9]

In June 1958 the National Academy of Sciences, a private organisation chartered in 1863 to promote the advancement of science and, when requested, to advise the government on scientific matters, established the Space Science Board, chaired by Lloyd Berkner, to advise the not-yet-active NASA on space research priorities. By the end of 1958, both the President’s Science Advisory Committee and the Space Science Board had cited ‘lunar exploration’ as a worthwhile scientific objective for the new agency.

The only interest in the Moon as a body in its own right expressed by the Pioneer project started by the Advanced Research Projects Agency was to photograph its far-side. But this was not achieved by the Air Force probes, and the discoveries made by the first Army probe led to the deletion of the imaging system of the second probe in order to obtain further particles and fields observations. To be fair, this data was an important contribution to a rapidly developing field of the International Geophysical Year.

The first lunar project authorised by NASA was the Atlas-Able, which was an Air Force launch of a probe supplied by the Space Technology Laboratories. The initial idea had been to use the Atlas, which was much more powerful than the Thor, for a program that would make two launches to send probes towards Venus and then two to insert probes into lunar orbit, but Luna 1’s flyby of the Moon prompted NASA to order the planetary payloads to be replaced by lunar orbiters. The 170-kg probes were to have a spin-stabilised 1-metre-diameter spherical structure with four ‘paddle wheel’ solar arrays around the equator. They would use liquid-propellant engines to make a midcourse correction on the way to the Moon and later to enter orbit around that body. In addition to a suite of particles and fields instruments, they would carry the TV system made for the Thor-launched probes. The first probe was destroyed on 24 September 1959, when the Atlas exploded during a static test. The second lifted off at 07:26 GMT on 26 November from Pad 14 on a direct ascent trajectory, but the aerodynamic shroud protecting the probe failed 45 seconds into the flight. The third lifted off at 15:13 GMT on 25 September I960 from Pad 12, but the first of the two Able stages malfunctioned and fell into the atmosphere 17 minutes after launch. The final probe was launched at 08:40 GMT on 14 December 1960 from Pad 12 but the vehicle exploded 68 seconds later. Although in each case the plan was to enter lunar orbit, most of the 55-kg scientific payload was for particles and fields investigations; indeed, the TV system was deleted from the second pair of probes to accommodate additional radiation detectors. In fact, the Moon was to serve merely as an ‘anchor’ in space away from Earth. In no way could this series of probes be said to constitute ‘lunar exploration’. However, even as the Atlas-Able probes were being developed the situation was changing.

As Assistant Director of the Lewis Laboratory of the National Advisory Council for Aeronautics, in the summer of 1958 Abraham Silverstein played a leading role in the establishment of NASA. When the new agency set up the Office of Space Plight Development at its headquarters, Silverstein became its Director. He promptly hired Homer E. Newell as his assistant for Space Sciences. Newell had joined the Naval Research Laboratory in 1944, and the next year started to conduct research into the upper atmosphere using sounding rockets – in particular investigating the interaction between the magnetic fields of the Sun and Earth. He served as the Science Program Coordinator for the Vanguard project of the International Geophysical Year.

At NASA, Newell created a division staffed by members of the upper atmosphere research group of the Naval Research Laboratory, to organise the agency’s activities in that field. In November, he appointed Robert Jastrow to chair another division to address astronomy, cosmology and planetary sciences. As a sky scientist, Jastrow set out to learn about these topics by visiting the leading proponents.

On reaching the age of 65 in 1958, Harold Urey had retired from the University of Chicago and taken a research position at the University of California at San Diego. He was a member of the Space Science Board of the National Academy of Sciences, and in a paper entitled The Chemistry of the Moon given on 29 October 1958 at the third Lunar and Planetary Exploration Colloquia he had explained the significance of sending a probe to photograph the far-side of the Moon.

When Jastrow visited Urey in early January 1959, Urey emphasised the ‘‘unique importance’’ of the Moon for achieving an understanding of the origin of the planets. As Jastrow recalled of this meeting in his 1967 book Red Giants and White Dwarfs: ‘‘I was fascinated by [his] story, which had never been told to me before in 14 years of study and research in physics.’’ The following week, at Jastrow’s invitation, Urey gave a 2-day presentation at NASA headquarters in which he urged that probes be sent to the Moon. After deliberating, Newell concluded that NASA should initiate a program to study the Moon as an object in its own right. He formed an ad hoc Working Group on Lunar Exploration, with Jastrow in the chair and Urey as a member, to evaluate and recommend experiments which should be placed into orbit around the Moon or landed on its surface. This gave the lunar (and later planetary) scientists a presence at NASA headquarters to match that of the sky scientists.

At that time, JPL was drawing up a proposal for a program of a dozen deep-space missions, of which five would study the Moon. On 5 February 1959 Jastrow sent a contingent to JPL to pass the word that NASA was keen to undertake lunar exploration. The options were for probes to report results as they plunged to their destruction by smashing into the Moon, to enter lunar orbit, and to land instruments on the surface. JPL was authorised to initiate preliminary work. It formed a study group chaired by Albert R. Hibbs.

In fact, in 1959 JPL engineers and scientists were more interested in the challenge of sending probes to Venus and Mars than they were in studying the Moon. There were ‘windows’ for efficiently sending probes to Mars at 25-month intervals and to Venus at 18-month intervals. As the next windows were October I960 for Mars and January 1961 for Venus, the feeling was that the immediate effort should be devoted to these opportunities, rather than the Moon, which could be reached at almost any time. In 1958 JPL had proposed to NASA the development of a new upper stage for the Atlas. This Vega stage would be powered by the engine of the Viking ‘sounding rocket’, modified for ignition in the upper atmosphere. The Atlas-Vega was to be used to launch satellites. A third stage would dispatch deep-space probes. The Soviet lunar flyby in January 1959 spurred the US Congress to authorise the development of the Vega stage. On 30 April JPL sent NASA a 5-year plan of deep-space missions using the Atlas-Vega. The aim was to devote the early effort to flybys of Venus and Mars, and postpone lunar science until 1961. A rough lander would be followed up by an orbiter equipped to investigate the space environment near the Moon and to obtain high-resolution pictures to enable a site for a soft lander to be chosen. Jastrow recommended to Newell the development of a seismometer, communication system and power supply for the package that would be delivered to the lunar surface by the rough landing method. It was later decided to operate a magnetometer, gamma-ray spectrometer and X-ray fluorescence spectrometer during the approach phase. On 25 May 1959, Silverstein and Newell decided to follow the rough lander launched by the Atlas-Vega with two soft landers launched by the Atlas-Centaur, the latter using a powerful stage that was expected to enter service in 1962. In June 1959 Silverstein told JPL to cancel the Mars mission and reassign its launcher to a lunar orbiter.

On 23 July Keith Glennan, Hugh Dryden and Associate Administrator Richard E. Horner met George B. Kistiakowsky, who had succeeded James Killian as Eisenhower’s Special Assistant for Science of Technology, to discuss the objectives of the space program. Glennan warned that slippage in the development of the Vega stage made planetary flights in 1960-1961 impractical. Windows for the Moon were not only more frequent, the flight time was days rather than months. Glennan recommended that the agency focus on lunar missions in order to address the short­term objectives recently specified by the National Security Council’s policy paper, Preliminary US Policy on Outer Space? This was agreed. Several days later, Silverstein cancelled the Venus mission and directed JPL to prepare a new schedule which focused on the Moon. Meanwhile, Newell had established the Lunar and

Document NSC5814/1.

More Soviet successes 53

Planetary Programs Office and transformed Jastrow’s ad hoc Working Group on Lunar Exploration into a standing committee as the Lunar Science Group.

SCIENTIFIC TARGETS

On 7 March 1967, several days after Lunar Orbiter 3’s readout was curtailed, the project established a working group to develop the strategy for the final mission of the series. It was decided that if Lunar Orbiter 4 was successful in its mapping, then Lunar Orbiter 5 should undertake a scientific mission involving multiple targets. The photographic objectives were: (1) to obtain additional near-vertical, stereoscopic and westward-looking oblique frames of the eastern candidate sites for the early Apollo landings; (2) to accomplish broad survey coverage of those portions of the far-side which had been in darkness during previous missions; (3) to obtain pictures of sites of interest to the Surveyor project; (4) to reconnoitre potential targets for advanced Apollo landings – i. e. sites outside the equatorial zone; and (5) to take a close look at as many scientifically interesting sites as possible. The main criterion for a site being considered to be interesting was its perceived ‘freshness’. The pictures from Ranger and the Lunar Orbiters to date had revealed most lunar terrain to appear subdued, so it had been decided to seek terrains which had not been exposed for long enough to have been significantly weathered by the incessant rain of material from space.

The preliminary plan was put to Boeing on 21 March, and a meeting on 26 May designed an orbit that would enable the spacecraft to address the widely distributed targets without violating any of its operating constraints. It would have to fly in a near-polar orbit to gain the latitude coverage, on a track with the Sun at an elevation of between 8 and 24 degrees to highlight the topography, and the perilune at about 100 km to provide the requisite 2-metre resolution.

Lawrence Rowan had led the US Geological Survey’s participation in the Apollo site selection process, but he stood down after Lunar Orbiter 3. Donald E. Wilhelms took over this role for Lunar Orbiter 5, with its focus on advanced Apollo missions.

On 15 March Bellcomm had hired Farouk El-Baz, an Egyptian geologist with a PhD from the University of Missouri, and he undertook much of the organisational work. Whereas the sites short-listed for the early Apollo landings were on open plains with as few craters and rocks as possible, it was evident that advanced landings would be best made at sites where craters had excavated boulders. And, of course, there were mountains, rilles and features which appeared to be of volcanic origin. However, to be viable a target required a clear line of approach from the east, and this favoured interesting sites adjacent to smooth plains over which an Apollo lander could make its approach. Of course, if the landing site was several kilometres from the ‘feature’ that attracted the interest of the selectors, some form of surface transportation would require to be provided in order to enable the astronauts to reach their true objective.

On 14 June the Surveyor/Orbiter Utilisation Committee approved the overall plan. The initial target list was compiled largely from telescopic studies, but almost half of the items were revised following a review of the Lunar Orbiter 4 results. The agreed objectives were (1) to inspect 36 sites of scientific interest on the near-side, (2) to obtain additional views of five potential Apollo sites and a number of Surveyor sites, and (3) to map most of the far-side that had not previously been covered.

Lunar Orbiter 5 lifted off at 22:23:01 GMT on 1 August 1967. Its Canopus sensor had difficulty finding its target star, but locked on in time for the 26-second, 30-m/s midcourse manoeuvre at 06:00 on 3 August. A 508-second, 644-m/s insertion burn initiated at 16:48 on 5 August attained a 195 x 6,028-km orbit inclined at 85 degrees with a period of 8 hours 27 minutes. The phase of the Moon was ‘new’ on 6 August, and would be ‘full’ on 20 August. Most of the far-side pictures were to be taken in this initial orbit. The first picture was taken at 23:22 on 6 August, near apolune. An 11.4-second burn at 08:44 on 7 August lowered the perilune to 100 km. At 09:05 an impromptu picture was taken of Earth. A 153-second burn at 05:08 on 9 August lowered the apolune to 1,500 km and reduced the period to 3 hours 11 minutes. The Bimat was cut at 03:30 on 19 August, and the readout was concluded on 27 August.

The Apollo sites had been assigned 44 frame-pairs, which was about 20 per cent of the total. The sites of scientific interest on the near-side had included the rilles in Mare Serenitatis near the crater Littrow and near Sulpicius Gallus; some lava flow features in Mare Imbrium; the craters Copernicus, Dionysus, Alphonsus, Dawes and Fra Mauro; secondary craters associated with Copernicus; the Aristarchus plateau; and small domes near Gruithuisen, Tobias Mayer and Marius. All of these sites were regarded as possible targets for advanced Apollo missions.[37]

On 21 January 1968, during the extended mission, the 61-inch telescope of the University of Arizona successfully photographed the orbiter against the stars when it was at apolune. Ten days later, the spacecraft was deliberately crashed in Oceanus Procellarum.

Astronomers had inferred that either the Moon’s shape or its density distribution (or perhaps both) were irregular. The radio tracking of the Lunar Orbiters did not settle the question of the Moon’s shape, but did yield a major discovery. The early missions in near-equatorial orbits had revealed the Moon’s gravitational field on the near-side to be irregular – after allowing for the variation of velocity with altitude in an elliptical orbit, the vehicles kept speeding up and slowing down. The tracking of Lunar Orbiter 5 in its low polar orbit enabled a gravimetric map to be compiled with sufficient resolution for the ‘anomalies’ to be correlated with surface features. It was found that a vehicle was accelerated as it approached one of the ‘circular maria’ and decelerated afterwards.

Such sites included Imbrium, Crisium, Smythii, Serenitatis, Humorum, Nectaris, Humboldtianum, Orientale and Grimaldi. As the maria were low-lying rather than elevated landforms, it was apparent that they must be of a greater density than their surroundings. One early suggestion was that the ‘attractor’ was the buried body of the impactor which excavated the basin that was later filled in by mare material, but this hypothesis was rejected when it was realised that there were negative anomalies associated with basins that had not been filled in by maria. John O’Keefe argued that the attractor was the infill itself. That is, the anomalies were the due to magma from deep in the interior having erupted onto the surface – gravitational attraction falls off with the inverse square of range, and dense material on the surface would produce a significant local attraction. Negative anomalies included craters such as Copernicus, which had essentially excavated ‘holes’ in the maria. Since the positive anomalies represented concentrations of mass, they were dubbed ‘mascons’. The discovery was reported in a paper in Nature in August 1968 by Paul M. Muller and William L. Sjogren.

If the lunar crust had been able to adjust isostatically to the eruption of dense lava onto the surface there would be no anomalies today; the fact that this had not occurred was evidence that the crust was sufficiently rigid at the time the lava was erupted to support its weight. In 1968 Ralph Baldwin provided an explanation. A basin formed and was ‘dry’ for a while, during which its floor began to adjust isostatically to the removal of the crustal material. But before it could achieve equilibrium, fractures in the floor allowed lava to well up and fill in the low-lying areas. This process of infill occurred in many pulses over an extended time. Being dense, the mare pool tended to sink, thereby forming compression wrinkles in its centre and opening rilles at its periphery. When it was unable to achieve isostatic equilibrium the result was a local mascon. A further realisation (obvious in retrospect) was that the sudden removal of crustal material in the excavation of a basin would relieve the pressure on the mantle below and induce deep melting, which would in turn cause a plume to rise, lift and fracture the floor of the basin, and drive enormous volumes of low-viscosity magma to the surface. A question for further research was why most of the basins on the far-side were ‘dry’ – was the crust thicker on that side of the Moon?

WRAPPING UP

The five Lunar Orbiter missions were launched within a 12-month interval. They suffered various technical problems, but the primary objective of providing pictures in support of Apollo was achieved. Only 78 per cent of the frames were classified as ‘useful’, but a large batch of useless ones were the H frames from the first mission. Although solar flares occurred during missions, photography continued. The worst radiation dose was on 2 September 1966, but the flood of energetic protons did not fog Lunar Orbiter 2’s film. This confirmed the wisdom of using a very ‘slow’ film. The radiation detector data confirmed that the Apollo vehicles and spacesuits would protect astronauts from an average exposure to solar plasma, and indeed from short­term greater-than-average exposure. In all, the five Lunar Orbiters reported a total of 22 micrometeoroid strikes over their entire time in space. The hazard in lunar orbit proved to be about half of that in low Earth orbit. An additional benefit to Apollo from the extended missions of the Lunar Orbiters, was the experience gained by the Manned Space Flight Network in tracking vehicles in lunar orbit. If the existence of mascons had not been discovered prior to the first Apollo mission venturing out to the Moon, the astronauts would have found their orbit varying in an unpredictable (and alarming) manner. This was the value of making a thorough reconnaissance!

Boeing had sufficient parts to assemble a sixth spacecraft, and even before Lunar Orbiter 5 was launched the Office of Space Sciences and Applications considered an additional mission. On 5 July 1967 Lee Scherer explained that this could perform a survey of the far-side at a resolution similar to that provided by Lunar Orbiter 4 of the near-side. One suggestion was that it should carry the gamma-ray spectrometer built for Ranger, in order to make a preliminary map the composition of the surface. On 14 July Homer Newell wrote to Robert Seamans putting the case for launching a sixth mission in November. Seamans refused, in part because it would not directly contribute to Apollo – which was not capable of landing on the far-side.

The scientists had hoped to develop Lunar Orbiter Block II to conduct a series of missions utilising a variety of sensors. In late 1964 the Office of Space Sciences and Applications compiled an experiment list: a gamma-ray spectrometer to survey the abundances of radioactive isotopes on the lunar surface; and infrared experiment to map the surface temperatures; a photometry/colorimetry experiment to determine the variation in the photometric function and colour of the surface material; a radiometer to measure surface thermal gradients; an X-ray fluorescence spectro­meter to survey the relative abundances of nickel and iron on the surface; a solar plasma experiment to measure the spatial and temporal variation in flux and energy distribution of low-energy protons and electrons; a magnetometer to determine whether the Moon had a magnetic field; an instrument to test for a low-density ionospheric plasma; and using the transmitter for a bi-static radar experiment to study the roughness and dielectric properties of the surface. But without the leverage of the Office of Manned Space Flight this proposal failed to attract funding.

LUNAR FLYBY

In May 1961 Aeronutronic began to drop balsa encapsulated ‘survival capsules’
containing sterilised systems immersed in viscous fluid from aircraft flying over the Mojave Desert – with disappointing results: those that fell on rocky ground failed to operate. Further tests in October showed that even seismometers which survived the impact often suffered electronic issues. With the launch of Ranger 3 only months away, this was disconcerting. On 6 November 1961 Don B. Duncan replaced Frank Denison in charge of developing the capsule. NASA issued heat-treatment waivers for the most sensitive components of the radar altimeter, retro-rocket and capsule. In 1961 Albert Hibbs, Chief of the Space Sciences Division at JPL, appointed Harold W. Washburn as Ranger Project Scientist to liaise between the spacecraft engineers and the experimenters and coordinate their activities during a mission.2

Meanwhile, after the Ranger 3 bus was assembled at JPL in July 1961 it suffered much greater component failure rates than the case of the proof-test model, with the only difference between them being heat-sterilisation. NASA issued further waivers for the most sensitive components. ft was clear that the sterilisation process efficacy specified in 1960 was unattainable. On 15 November NASA formally accepted the repaired bus. ft was driven by truck in an environmentally regulated container, and arrived at the Cape on 20 November. On 6 December Oran Nicks opined to Edgar Cortright that one of the three Block ff flights would be successful, and one, perhaps two, of the four Block fff flights. This underscored the perceived technological risk of the venture. James Burke expected one of each to be a fully successful flight. On 2 January 1962 Clifford Cummings told Robert Seamans that it was “likely that the sterilization procedures have compromised spacecraft reliability”. However, when Lockheed announced that it had fixed the problem with the Agena B, NASA decided to try to launch Ranger 3 on schedule.

The major objectives for the mission were to perform the midcourse and terminal manoeuvres. Given the performance of its predecessors, it was fully expected that on being set free by the Agena, Ranger 3 would deploy its appendages and adopt cruise attitude. ff it flew to the Moon as planned, then Burke’s engineers would be content. ff the surface package functioned properly, this would constitute a bonus – if not, the package would have two more opportunities to achieve its scientific objectives.

Although it would be a considerable technical feat to reach the Moon at all, and in a sense anywhere would satisfy the mission, the trajectory was very limited. The fact that the retro-rocket of the surface package could not deal with a lateral velocity component meant the bus needed to make a vertical descent over the target. This, in turn, meant a site near the equator on the leading hemisphere. Prior to the space age, astronomers had defined lunar longitude in terms of how the Moon appeared in the terrestrial sky, with the leading limb (i. e. the one that faces the Moon’s direction of travel as it pursues its monthly orbit of Earth) being east. However, in August 1961 the fnternational Astronomical Union had redefined the system to match the point of view of an observer on the lunar surface, with east in the direction of sunrise; thus reversing the old scheme. For a Ranger Block ff the

Подпись: 2fn 1963 Thomas Vrebalovich would succeed Washburn as Ranger Project Scientist at JPL.

target would therefore have to be in the western hemisphere. In fact, a vehicle launched from Florida would expend less energy in approaching Oceanus Procellarum between 10 and 50 degrees west of the meridian and within 16 degrees of the equator than it would for any other region. Because the Moon maintains one hemisphere facing towards Earth, at any given site Earth remains in a more or less fixed position in the sky. The target could not be so far towards the limb that at unfavourable librations the signal from the surface would be too weak to be read. Another constraint was that the timing had to be such that the Moon was visible to Goldstone when the bus transmitted its scientific data. The phase of the Moon would be ‘full’ on 20 January 1962 and ‘last quarter’ on 28 January. The window was set for 22-26 January. If Ranger 3 managed to lift off on the first day, it would make its approach on 25 January.

After Ranger 3 completed its final systems checks in Hangar AE, it was driven to Pad 12 on 18 January and installed on its launch vehicle. When kerosene was loaded into the Atlas on 19 January, a leak was discovered in the bulkhead between the fuel tank and the liquid oxygen tank. Over the next few days the Air Force removed the centre engine and built a wooden frame up through the exposed aperture at the base of the fuel tank in order to allow technicians wearing masks and oxygen cylinders to replace the ruptured bulkhead. This round-the-clock effort made the vehicle ready in time to attempt to launch on the last day of the window. Meanwhile, as this was the first mission of the project intended to reach the Moon, the spacecraft was sealed in the aerodynamic shroud atop the Agena and bathed in gaseous ethylene oxide for 11 hours as the final stage of the sterilisation process, then the shroud was purged with dry nitrogen passed in through a sterile filter.

The countdown on 26 January proceeded smoothly, and Ranger 3 was launched at 20:30 GMT. The Air Force tracked its ascent and calculated the steering commands, but when these were transmitted to the Atlas it failed to act on them. The autopilot flew on, ignorant of deviations from the planned trajectory. In particular, it was not possible to command the moment of shutdown to optimise the final velocity, and when the autopilot ordered this using its programmed parameters it was both higher and faster than required. As a result of this discrepancy, the parking orbit attained by the Agena was slightly different to that planned. The limited ability of the spacecraft to correct its trajectory meant that in making the translunar injection the Agena had to pass through a ‘key hole’ in the sky that was only 16 km wide, and attain a speed which differed from the desired 40,000 km/hour by no more than 25 km/hour. In the event, Woomera’s tracking indicated that the spacecraft would cross the orbit of the Moon at a point 32,000 km ahead of that body – a discrepancy which exceeded the spacecraft’s 44-m/s midcourse manoeuvre cap­ability. Nevertheless, engineers were encouraged that Ranger 3 had deployed its solar panels, locked onto the Sun, rolled to acquire Earth and then deployed its high – gain antenna. The flight would provide an opportunity to evaluate the spacecraft’s performance in deep space, essentially as had been intended for the Block I.

James Burke flew from the Cape to JPL to operate the spacecraft from the Space Flight Operations Center. It was decided to exercise all of the functions, including the midcourse and terminal manoeuvres. It was not possible to test the retro-rocket

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Preparing the surface package subsystem of the Block II Ranger spacecraft.

of the surface package, since its separation from the bus could be triggered only by its own radar altimeter. On 27 January the sequence of commands was uplinked for a midcourse manoeuvre designed to reduce the flyby range. Ranger 3 executed the preliminary roll and pitch changes as specified, fired its engine, then resumed cruise attitude. However, tracking revealed that the burn was the opposite of that intended and had increased the miss distance to 36,750 km. The error was an inverted sign in the computer program used by JPL to calculate the burn. Regardless of the outcome, the engineers were delighted that the spacecraft had made a manoeuvre and resumed its cruise attitude. Shortly after this, the boom holding the gamma-ray experiment completed its deployment. It had hinged down after separation from the Agena, and now, as planned, a gas generator extended it in a telescopic manner. The instrument was able to calibrate the emissions by the spacecraft and then make the first direct measurement of the flux of gamma rays in space.

A plan had been devised to perform a terminal manoeuvre which would orient the spacecraft to enable it to photograph the Moon during the flyby – in much the same manner, in fact, as had been intended for some of the Pioneer probes. In this case, it would view the illuminated leading hemisphere, and reveal that portion of the far – side which was in darkness for Luna 3 in 1959. The unplanned trajectory meant that Ranger 3 drew close to the Moon on 28 January. The cover for the optics was commanded to open, and power was applied to warm up the TV system. Goldstone uplinked the commands for the terminal manoeuvre to turn the spacecraft in order to point the camera at the Moon. The inverted sign had been corrected prior to making the calculation. An hour later, the spacecraft was told to make the manoeuvre. It initiated the pitch change in the correct direction, but soon thereafter the downlink began to intermittently drop out – a computer/sequencer fault had denied the vehicle the use of its Earth and Sun sensors, the gyroscopes directing the turn did so in an uncontrolled manner and the spacecraft was left spinning. At the appointed time, the TV system took pictures. Some frames were received at a very weak signal strength, and the fact that it was possible to see the black reference marks on a pane of glass in front of the focal plane silhouetted against a soft glow of sunlight glinting off the structure of the spacecraft provided welcome confirmation to the engineers from the Radio Corporation of America that their system had worked. At 23:23 GMT, some 6 hours after the attempted manoeuvre, Ranger 3 crossed the orbit of the Moon and passed on into solar orbit.

On 8 February 1962 JPL informed Oran Nicks of the preliminary findings of its investigation into the loss of Ranger 3. It had been concluded that the malfunction of the computer/sequencer was a result of the heat treatment required for sterilisation. It would therefore be necessary to issue waivers for the components believed to have failed. Although the mission had not reached the Moon, it had nevertheless provided an opportunity for the flight control team to compute a deep-space trajectory and then uplink the commands for a midcourse manoeuvre, which the spacecraft – the most sophisticated American deep-space vehicle to date – had executed as directed. The engineers were therefore confident that the next mission would reach the Moon.

Meanwhile

Homer Newell’s Space Sciences Steering Committee decided on 1 December 1961 to consolidate the TV experiments of the Block II and Block III versions of Ranger. Previously, Gerard Kuiper, Gene Shoemaker and Harold Urey had been named to receive and interpret such pictures as were returned by the Block II flights – having played no part in the development of the camera. Now it was decided that they should form a team, together with Ray Heacock of the Space Sciences Division at JPL, and work with the Radio Corporation of America in the development of the high-resolution TV system for the Block III. In effect, Newell wished to integrate the engineers and scientists at the project level at JPL to match the recent integration at the program level in Washington, in the expectation that this would enhance the scientific results. Unfortunately for James Burke, in early 1962 Newell also sought to augment the Block III to recover some of the particles and fields research lost on the Block I flights. On 14 March 1962 the Steering Committee decided to add eight experiments to the Block III. Burke learned of this from Oran Nicks on 20 March. The solar panels of the Block I and Block II were triangular with truncated tips. It was necessary to fit larger rectangular panels to provide the power to operate all the additional Block III experiments.