Apollo, The Intermediate Missions
Created | Updated Sep 10, 2013
Project Apollo: The Beginnings
| Mission Planning
| Landing Site Selection
| Earthbound Support Systems
Astronaut Selection and Training | The Saturn V | The Saturn 1B | The Apollo Spacecraft
Guidance and Navigation | Command and Service Modules | The Lunar Module
Assembling and Launching | Pathfinders | The Early Missions | Apollo 11, The First Landing
The Intermediate Missions | Apollo 15 Exploration | Apollo 16 Exploration | Apollo 17 Exploration
Skylab and Apollo-Soyuz | Conclusion
Apollo 11's landing site in the Sea of Tranquillity had been chosen primarily for its ease of access and because it provided a relatively broad and flat expanse to set down, where any landing within the designated zone would be acceptable without the need for pinpoint accuracy. With the completion of the Apollo 11 mission, which had landed some four miles past its designated site, President Kennedy's challenge had been met; but future missions would need to demonstrate a higher degree of accuracy to land in some of the more geologically productive sites. It would be of no use planning sophisticated missions to inaccessible spots if they were unable to put the spacecraft down accurately.
Post flight analysis of Apollo 11 had shown a number of reasons for the 'long' landing. The main factor was perturbations in the descent orbit caused by fluctuations in the lunar gravity field. Concentrations of Mass (Mascons) in the younger mare plains caused localized increases in the gravity field, which affected the spacecraft's line of flight. This had first been noticed in the Lunar Orbiter missions where the satellite's orbits had been affected. NASA's flight guidance team came up with an answer and were confident that they could place future spacecraft on their landing sites with much greater accuracy. By measuring the Doppler shift of the spacecraft's returned radio signal - which was already used to pinpoint its position - and comparing it to a predicted value, the difference could be used to adjust the guidance computer to compensate for the gravity effects. However, this would have to be demonstrated with an accurate, pinpoint landing before committing future missions to the more hazardous mountainous regions.
The missions following Apollo 11 were to be extended to allow a longer stay time on the surface with a rest period between two EVAs. Each moon walk would be for periods of up to three and a half hours, allowing the crew to extend their excursions away from the immediate vicinity of the LM; although, at this stage, they were still on foot. These extended missions were designated as 'H' class and four were planned to take place, Apollo's 12 to 15. Ultimately, only two would take place, one would not make it to the surface and another would be upgraded to 'J' class.
On the 14 November, 1969, Apollo 12 crewed by Commander Charles 'Pete' Conrad, Lunar Module Pilot Alan L Bean and Command Module Pilot Richard F Gordon took off from launch pad 39a and was struck by lightning 36 seconds after lift off. A second strike occurring 16 seconds later. On board, circuit breakers to the service module's power cells tripped out, lighting up almost all the warning lights on the CM's control panel. Moments later, as the second strike occurred, the navigation system lost its data platform and the master alarm came on. However, the Saturn's launch guidance system remained functional and Apollo 12 held on its planned trajectory. Electrical systems flight controller John Aaron recognised that all three of the service module's power cells had tripped out and advised the crew to switch the command module's power supply to its internal batteries, which restored the instrument telemetry between the spacecraft and mission control. Still without instruments inside the spacecraft, the crew held off resetting the main power circuits from the service module until the Saturn staged. As the first stage booster fell away, Bean reset the power source and brought the crews instrumentation back on line. Meanwhile the Saturn, which was controlled by the flight guidance system in the top of the third stage, continued unaffected and guided the craft into its earth parking orbit without mishap.
The craft remained in orbit while the damage was assessed and the CSM's guidance platform data was reset. After checking out the spacecraft some concern remained that the electrical circuit for the re-entry parachute pyrotechnics may have been effected and that the landing parachutes may fail to deploy after re-entry. As this could not be confirmed, it was decided to continue the mission; and the 'go' signal was given for the Trans Lunar Injection (TLI) burn. Post launch analysis found that the lightning discharge had been able to take place through the ionised gas trail left by the Saturn's exhaust which conducted the strikes back to the launch tower.
The target for this mission was to be the Oceanus Procellarum (Ocean of Storms), to the western end of the Apollo Landing Zone, near a pattern of craters known as 'Snowman', where a robot lander probe, Surveyor 3, had put down two years previously in the crater that formed the torso of the Snowman formation. One of the mission's tasks would be to retrieve parts of Surveyor to see how structural materials had been effected by long term exposure to heat, cold and radiation from space. If successful, the landing would also demonstrate the ability to achieve a pin point touch-down at a selected site, which would open the possibility for landings in more restricted locations.
Another feature of interest that clinched the site selection was an ejecta ray of material crossing the formation from the much later Copernicus Crater some 200 miles to the north and well outside the Apollo landing zone. Sampling the ray would provide the date of the Copernicus impact and give an insight into the ages of all the terrain that the ray crossed. Comparison of samples from another of the great maria with those taken at Tranquillity base by Apollo 11 would also establish whether all the maria had been formed at the same time and whether the lava differed in composition.
Apollo 12's lunar module named Intrepid was crewed by Conrad and Bean, while the command module, Yankee Clipper, was piloted by Gordon. The CM's name reflected the fact that all Apollo 12's crew were US Navy personnel. No further difficulties were experienced on the outbound journey, after the electrifying start, and Conrad began Intrepid's descent to the lunar surface four days later on 19 December, 1969. Passing through 7,000 feet, Intrepid pitched over allowing the crew to get their first good view of the landing site. At first Conrad could not make out Snowman's features; but as Bean began calling out the numbers, Conrad aligned the Landing Point Designator (LPD) and found the graticule cross hairs lined up directly on the centre of Surveyor's crater. Blipping his hand controller, he moved the LPD's aim to the rim of the crater and overflew the edge looking for a landing spot between Surveyor and Head Craters. Approaching the surface, the engine's efflux began kicking up large quantities of dust that completely obscured the surface. Flying blind he brought Intrepid in to a pinpoint landing at 3.04 degrees south, 23.42 degrees west, within 530 feet of its target.
The First EVA, ALSEP Deployment
Conrad exited Intrepid and on stepping out onto the surface said:
Whoopee... Man, that may have been a small one for Neil but that's a long one for me.
He was referring to the difference in height between himself and Armstrong. As one of the shorter astronauts at 5'6'' tall, stepping off the LM's ladder, which ended about three and a half feet above the surface, was no mean feat for him in a bulky space suit. He was joined on the surface by Bean a few minutes later. Conrad's first task was to deploy a High Gain 'S' Band Antenna , an umbrella-like aerial measuring five feet in diameter, mounted on a small tripod that unfurled and was to be pointed directly at earth to improve communication signals. Bean deployed a colour TV camera for coverage of the mission back to earth. As he did so, he inadvertently pointed it directly at the sun which almost immediately burnt out the camera's image tube, ending any possibility of TV transmissions from the surface.
While public and media interest in the lunar missions had reached an all time high with Apollo 11, interest was now declining as space flight was becoming regarded by the general public as almost routine. The landing of Apollo 12 was covered by the American television networks; but as soon as it was realised that no further pictures would be received from the moon, the television companies cancelled their remaining scheduled broadcasts.
During the first EVA, the crew deployed the first Apollo Lunar Surface Experiment Package (ALSEP), which consisted of a number of experimental devices to remain on the surface and transmit data back to earth after the astronauts departure. The ALSEP had been omitted from the Apollo 11 mission, mainly due to weight considerations and that the missions priority had been to establish a landing. The inclusion of the ALSEP now gave a greater emphasis to the scientific and exploration elements of the missions.
The ALSEP included another Passive Seismic Experiment, similar to that on Apollo 11, and (in addition),
- Lunar Surface Magnetometer to measure the moons magnetic field
- Cold Cathode Gauge Experiment to measure any residual atmosphere or gasses remaining on the surface
- Solar Wind Spectrometer to record the direction and density of the solar wind
- Suprathermal Ion Detector to detect the low energy ions of the solar wind
All these experiments were tied into a central station, which provided power and communicated data back to earth.
Power generation of the central station was from a Radioactive Thermal Generator (RTG), developed by the American Atomic Energy Commission for use in space and other remote locations. The generator, a SNAP-27 (Systems for Nuclear Auxiliary Power) used a core of plutonium as its power source. During the flight the plutonium element was housed separately in a protected flask on the exterior of the lunar module's descent stage, so that in the event of the craft being destroyed during take off or in the earth's atmosphere, the plutonium would remain intact. The element was to be removed from its flask and inserted into the RTG when the experiments were set up on the surface. However, Bean experienced difficulty removing the element from the flask when it jammed half way out. Conrad was called over to help, but the element remained stuck until the application of a couple of hard raps with the geological sample hammer released it. 'Never come to the moon without a hammer.' quipped Conrad.
On completion of the ALSEP deployment the crew found they still had some minutes of the EVA left and began some random sampling of the surrounding area. They ventured out some 75 yards to the edge of Middle Crescent Crater, a shallow crater 350 yards wide to sample and photograph before returning to Intrepid for a rest period
The Second EVA, Bench Crater and Surveyor
Conrad and Bean carried out two EVA's. The second was a circular traverse of over a mile, taking in the Snowman's Head crater; then south to Bench, Sharp, and Halo craters; and back to the Surveyor crater, where the robot craft rested on its inner, eastern slope. The crew carried out sampling stops at each of the craters. Bench crater was of particular interest to the geologists due to its terraced layering, showing a distinct bench, or ledge, in its wall and a small mound in the centre, from which it derived its name. Conrad was invited by the Earth-bound geologists to go into the crater to obtain a sample, but declined due to the steepness of the inner slope.
Due to the prevailing lighting conditions and the undulating surface, they had difficulty establishing the location of Sharp crater, the furthest point in the traverse from the LM. They returned past the southern side of Bench, where they again had difficulty locating Halo. Rather than fall behind on their schedule, they carried on to Surveyor. Observed from the LM on the first EVA, Surveyor crater had at first looked as if it would be too steep to enter; but on closer inspection, this proved to be an effect of the low angle of lighting; and the crew were able to walk around the craters rim and down the gently sloping inner face to where the lander was located.
They observed that Surveyor had bounced slightly on landing, leaving imprints in the surface dust and that it's framework was covered in a reddish-brown discoloration. After photographing the site, they cut off a piece of the lander's frame and electrical wiring, and removed its TV camera and scoop arm for return to earth. They further removed samples, including one particular rock that could be identified from Surveyors earlier television transmissions. This would give the geologists an opportunity to see how accurate the conclusions they had drawn from Surveyor's TV evidence had been.
The crew's lunar surface stay time had been extended considerably from that of Apollo 11's; and they remained on the surface for a total of 31.5 hours, including the two EVA's totalling 7.75 hours, before their take off and return to dock with the orbiting Yankee Clipper. On return to the LM, the crew found that more dust than had been expected had attached itself to their clothing, and despite vacuuming it off, quantities of it proved to be a problem as, after take-off, it became weightless and floated around inside the capsule making the return journey uncomfortable.
One of the experiments deployed on their first EVA was a seismograph for further study of moonquakes. Intrepid had one more useful function to perform after docking and transfer of the crew to the CSM: It was de-orbited to impact on the moon's surface some 50 miles from the landing site at a speed of over 3,500 mph to provide a shock wave for the seismograph, enabling technicians to calibrate the instrument from a known impact source. A totally unexpected result was that it recorded shock waves from the impact for three quarters of an hour afterwards, as they echoed around the moon's interior. It was described as '... though one had struck a bell in a belfry of a church a single blow and found that the reverberations from it continued for thirty minutes'.
The Trans Earth Injection (TEI) burn and return from the moon was largely routine for Apollo 12. The crew brought back 75 pounds of samples and after re-entry with the parachutes functioning without mishap, splashed down in the Pacific, east of Pago Pago on the 24 November, 1969, to be picked up by the recovery ship USS Hornet.
After the previous successful Apollo flights and the two landings, space flight was beginning to seem routine to the general public. Having achieved the Kennedy challenge, the costs of the manned space flight program and further space exploration, were coming under close scrutiny and of the original 20 planned missions one, Apollo 15, had already been cancelled to save a Saturn V launch vehicle for the Skylab space station missions. A further two lunar missions were also postponed until Skylab's completion. After cancellation of the Apollo 15 mission, its target, the Fra Mauro formation, was re-assigned to Apollo 13 as it was considered to be potentially one of the most important geological areas on the lunar surface, and liable to yield samples from the earliest formation of the moon. What was to happen on the next lunar mission provided six days of high drama and almost the loss of a crew.
Apollo 13 launched on 11 April, 1970, for a landing attempt in the Fra Mauro region of the Oceanus Procellarum (Ocean of Storms), with the crew of Commander James A Lovell, Lunar Module Pilot Fred W Haise and Command Module Pilot John L Swigert. The original CM Pilot Ken Mattingly had inadvertently been exposed to German measles a few days before lift off and had been replaced at short notice by Swigert from the back-up crew. During the launch, the only malfunction occurred when the second stage S-II centre engine shut down two minutes prematurely, which caused the outboard engines to have to run 34 seconds longer. The third stage S-IVB engine also had to burn for an additional nine seconds to make up the shortfall. The crew in the CSM Odyssey then carried out the TLI burn and completed the docking and withdrawal of the LM Aquarius.
Nearly 31 hours into the flight, the crew carried out a mid-course correction, which took them out of a 'free return' course and into a hybrid trajectory, which would put them into an orbit around the moon suitable for a landing in the Fra Mauro area. They then settled down to the usual trans lunar journey routine
'Houston, We Have a Problem'
On the 13 April, 1970, 55 hours into the flight and just after closing down a television broadcast, Swigert undertook a routine task to stir up the No 2 fuel cell's oxygen tank in the service module. Seconds later, an explosion blew out a side panel and damaged the lines to the No 1 oxygen tank, which resulted in the complete loss of oxygen for the two fuel cells. Consequently, water and electrical power supply to the command module was cut off; and, without electrical power, all control of the service module's main Service Propulsion System's (SPS) engine was also lost.
The seeds of the accident had been sown some five years earlier when design engineers decided to modify the internal 28 volt power supplies of the spacecraft to allow it to accept a higher 65 volt supply from the ground services, during its time on the launch pad. Two thermostatic switches, which safeguarded the heating circuits inside the fuel cell's oxygen tank, were overlooked in the modification program. In itself this may not have caused a problem, as the switches would not operate unless overheating occurred in the tank; and, as the heater was not normally functioning for more than a few seconds at a time, this was not likely in normal use. Indeed, all flights from Apollo 7 onwards had used tanks with unmodified switches without a problem arising.
The faulty tank in Apollo 13 had originally been due for use in Apollo 10 but had been dropped about two inches during installation, which had caused some external denting of its thin walled skin and possibly further damage to an internal filling line. Another tank was fitted to Apollo 10, and the damaged one sent for repair. Tests after the repair to the dented skin had showed no further faults; and it was not realised that the fill line inside the tank was still faulty. The tank was later installed in Apollo 13.
During the countdown to Apollo 13's launch, difficulty was experienced when draining the tank, probably due to the faulty fill line. The problem was not thought to be serious; and, rather than delay the launch for up to a month while the tank was replaced, it was thought acceptable to boil off the residual oxygen. This involved keeping the tank's internal heater running for extended periods, causing the unmodified switches to operate when the internal temperature increased beyond the safe limit. As the switches tripped, they arced and welded themselves shut, under the influence of the full 65 volts across their unmodified terminals. Now, without the protection afforded by the switches the internal temperature of the tank continued to rise and, at some point, built up to over 1,000 degrees Fahrenheit, damaging the insulation to the internal fan motor, so that it became a potential hazard when the tank was later refilled with oxygen.
On Apollo 13, operation of the fan switch caused a short circuit in the damaged fan wiring and the insulation to ignite. The fire spread along the electrical conduit in the tanks side wall, weakening it so that it ruptured under the internal pressure of 1,000 psi. The resulting explosion damaged the adjacent No 1 tank's feed lines, while blowing off the SM's bay cover panels.
In normal operation the fuel cells combined oxygen and hydrogen to produce water and electricity supplies for the command module; but with both tanks out of action and the remaining oxygen bleeding away through the damaged plumbing, the fuel cells were unable to operate, starving the command module of power and water. The service module on which the crew depended, was for all practical purposes dead; and, as the flight was now committed to the outward journey to the moon, there was no doubt that the crew of Apollo 13 were in serious trouble.
Swigert: 'Okay Houston, we've had a problem here...'
Mission Control (MCC): 'This is Houston, say again please...'
Lovell: 'Houston, we've had a problem.'
Abort and Return
Had the explosion occurred after the moon landing, the crew would have had no possibility of returning home. At GET 30:40, Apollo 13 had completed a mid-course correction, which had taken them out of the original safe 'free return' trajectory and into one which would put them into an orbit necessary for a landing in the western Fra Mauro area of the moon. They now needed a burn of the SM's engine to bring them back to the free return trajectory; but, without electrical power, they had no control of any of the service module's functions. They did, however, still have the fully functioning lunar module Aquarius attached to the CSM, which could be used as a lifeboat, and its descent engine, which could provide propulsion.
The lunar module was only designed to function for two days with two crew members on board, whereas the return journey was going to take four days; and the trans earth injection burn would take a significant amount of the LM's power. It was essential to conserve as much power as possible, so all non-essential circuits, heaters, and electronics were powered down. Oxygen was not a significant problem, as sufficient reserves in the LM, the CM, and the lunar suits were available; but without the CM's environmental system working, a build up of carbon dioxide would occur inside the craft as the LM's system became overloaded. The LM's system would have to be used to scrub carbon dioxide from the internal atmosphere; but its lithium hydroxide filters had been designed for about 45 hours use by two men rather than 4 days with three. Although the CM carried its own filters, they were not interchangeable with those in the LM; and a way had to be found to bring them into use.
Back at mission control, the back up crew had been called in to fly simulated missions to recalculate the flight parameters to work out the best options for a return, and to solve the various problems arising from the loss of the SM's power source. A team of engineers were given the task of solving the carbon dioxide problem with a brief to use only materials that could be found aboard Apollo. They succeeded using a combination of suit hoses, plastic bags, and duct tape to convert the CM's filters to the LM's environmental system; and the crew were able to cobble this fix together under instruction from mission control.
Another major problem was to keep the CM's internal batteries charged with enough power to control the capsule during re-entry, after the LM was jettisoned, when its batteries would be its only power source. Working in the simulators and using wiring diagrams, the ground engineers and back up crew found a convoluted way to pass a trickle of current from the LM to the CM through a sensor circuit normally used to monitor power usage in the LM. By configuring switches and power breakers they were able to convey enough power from the LM to the CM's batteries to keep them charged. Also without a water supply from the SM the crew were limited to about 200 ml of water a day as the majority of the LM's supply was required to keep the essential cooling systems of the electronic equipment going.
Two burns of Aquarius' descent engine were found to be necessary for the return journey. The first, carried out five hours after the explosion, was to put Apollo 13 back into a 'free return' trajectory, so that the craft would loop around the back of the moon and slingshot out on a heading towards earth. But this also produced some navigational problems. The LM was not equipped with the same navigational information as the CM, so the computer's data platform had to be transferred from the CM to the LM. They also had to confirm that the direction of the burn would be correct; but it was proving impossible to get a navigational star sighting to fix their position, due to debris from the explosion that was surrounding them twinkling in the sunlight and blanking out the stars on which they needed to take sightings. The debris field could be observed from earth extending more than twenty miles out from the spacecraft.
Transfer of the data between the two computers was accomplished by Haise punching the corrected figures into the LM's computer manually after Lovell recalculated them from the CM's data and verified by mission control. Lovell also had to stabilize the craft using the LM's thrusters, as the craft was tumbling slowly from the initial explosion and venting oxygen from the ruptured plumbing, inducing an uneven roll. He finally brought the craft under control and aligned in the correct direction after two hours. Eventually, with the craft stabilized and aligned, they were ready to fire the descent engine; and, after a thirty one second burn, they were back on the free return course.
The new free return course would put the craft into a re-entry corridor that would bring them to a splashdown in the Indian Ocean instead of the Pacific, where the recovery fleet was stationed. Haise had also calculated that they would barely have sufficient cooling water for the LM's electronic circuits; and the water supply would be exhausted about five hours before re-entry. He was aware, however, that when Apollo 11's LM, Eagle had been abandoned in lunar orbit its electronic systems had continued to function some eight hours after the water supply had been turned off. If Aquarius performed in the same way, they would have about a three hour margin.
Calculations at mission control showed that a second burn two hours after rounding the moon would speed up the return by about nine hours and place the re-entry over the Pacific with its recovery ships. But to make the second burn they still had to establish the crafts position and register it in Aquarius' computer. Mission control had devised a way to do this without taking a star sighting; and Capcom Charlie Duke passed up the procedure. Lovell manoeuvred the craft into an attitude dictated by a set of co-ordinates relayed up by Duke; which, if the craft was in the correct position, would show the sun's disc in the LM's navigation telescope. Taking sightings, Haise found it to be correct to within one degree. Two hours after rounding the moon, at an altitude of 137 miles, the second burn trimmed nine hours off the return journey and placed the re-entry corridor over the Pacific Ocean. Again the burn went according to plan and inserted the spacecraft into its new trajectory
Conserving power meant powering down Aquarius to only the basic functions, which included turning off the guidance computer and heating. With little else to do except wait it out, the crew remained in Aquarius for the majority of the return journey, each one taking turns to sleep in the cold of the unheated command module. The temperature inside the craft dropped to 38 degrees Fahrenheit and condensation formed on the cold inner surfaces of the walls, instruments, and controls, creating a potential hazard from circuits shorting out when power would be re-instated just prior to re-entry. The crew were unable to sleep adequately and a leaking water spigot had soaked Swigert's boots and feet, which took two days to dry out, making the return passage tiring and unpleasant.
A course correction burn of Aquarius' engine was found to be necessary just after passing the midway point; and it would have to be done without the computers help. This time Mission control instructed Lovell to align the craft so that the sun could be seen through the LM's overhead docking window and rotate the craft to get the horns of the earth's crescent shape on the cross hairs of the LM's navigation sextant, which would put the craft in the correct position for the burn. To make the burn Haise kept the pitch aligned, Swigert timed the burn, and Lovell fired the engine while controlling the crafts roll. After 14 seconds, they were dead on course.
Nine hours out from re-entry, the crew began to return power to the command module, Odyssey and make ready for a last course correction, which was made necessary by occasional venting of gasses from the damaged service module pushing the craft off course. This was a minor correction using the LM's thrusters for a short 20-second burn. With four hours to go, the crew jettisoned Odyssey's service module; and, as it drifted away from them, they could see and photograph the extent of the damage for the first time. A complete panel covering one of the six equipment bays was missing, exposing considerable internal damage to the oxygen tanks, plumbing, and surrounding equipment. Finally, with Odyssey powered up on its internal batteries, it was time to cast off Aquarius, which had served them so well, and as the pyrotechnics were fired to separate the two craft, Capcom Joe Kerwin said for all of them: 'Farewell Aquarius, and we thank you.'
One last unknown factor remained, about which nothing could be done. The question of whether or not Odyssey's heat shield had been damaged by the explosion, and if it would fail during re-entry. They turned the craft's heat shield towards the atmosphere and prepared for re-entry. On the 17 April, 1970, half the world waited with bated breath to hear the re-acquisition of signal as Apollo 13 came safely through re-entry and splashed down near Samoa in the Pacific Ocean, with its crew intact four miles from the recovery ship, USS Iwo Jima.
With the failure of Apollo 13 to complete its mission, Apollo 14, whose designated landing site had been the Littrow Crater region, a site on the mountain range bounding the Mare Serenitatis, was now rescheduled to take over the mission to Fra Mauro. The crew and engineers had time to reconfigure the flight, while the investigation into the accident and modifications were carried out to the craft. Modifications included re-siting a third oxygen tank to isolate it from the other two, in order to ensure a supply in the event of another failure of the primary tanks.
Another innovation with Apollo 14 was the partial isolation for two weeks before the mission of the primary and back up crews from all but the most necessary human contact. This precaution was to prevent the contraction of communicable diseases, which had hampered the crews of Apollo's 7, 8, 9, and 13. The Apollo crews were limited to contact with family and necessary ground personnel. Even then, these primary contacts were monitored by the medical teams; and the crews were restricted to certain areas within the Cape.
The Fra Mauro Formation, a highland area, in the Oceanus Procellarum (Ocean of Storms) and south of the Imbrium Basin, was considered to be of the highest scientific interest and a prime geological site. The highland formation was thought to have been formed from ejecta material displaced in the cataclysmic event that had formed the Imbrium Basin in the moon's early crust, and that it would supply samples and data from depths of up to 60 miles within the original crust of the moon from a period just after it had begun to solidify from a molten state. Dating the material would establish the date of the Imbrium event and, from that, the dates of everything that the Imbrium ejecta blanket touched could be established as either pre or post Imbrium event.
The landing target area was to be in a relatively flat spot near a later 350 yard diameter impact crater named Cone Crater, which had drilled its way through the Fra Mauro regolith and into the ejecta blanket, where it was hoped, the displaced Imbrium material, and perhaps even the underlying early crustal material, may have been exposed. The key to Fra Mauro lay in obtaining samples from the rim of Cone crater, where rock displaced from its deepest levels would have been deposited.
Landing at Fra Mauro
On 31 January, 1971, at T minus eight minutes, the mission launch director halted the countdown of Apollo 14 due to bad weather crossing the Cape. After a 40 minute delay, the countdown resumed and Apollo 14 lifted off from pad 39a into an evening sky, carrying its crew, Commander Alan B Shepard Jr, Command Module Pilot Stuart A Roosa, and Lunar Module Pilot Edgar D Mitchell. After a successful launch and TLI burn, Roosa separated the command module Kitty Hawk from the S-IVB and prepared to dock with the lunar module Antares, to withdraw it from the top of the third stage.
After five attempts Roosa had not been able to get the docking probe to latch into the LM's drogue. On the sixth attempt he latched on successfully, after firing the forward thrusters as the two craft came together to ram the docking probe home. After extraction of the LM from the S-IVB, examination of the docking probe and ring showed considerable scoring on the mating faces; but no other fault was apparent; and the probe was deemed serviceable to continue the mission.
Apollo 14 braked into lunar orbit; and, after one orbit, Kitty Hawk's engine was fired again to place it into an elliptical orbit with a low point of 50.000 feet from where Antares could begin its powered descent. This modification of the flight plan to use the CM's engine instead of that of the LM to achieve the lower descent orbit meant a saving of the LM's fuel, which would provide a longer hover time over the landing site.
Shepard and Mitchell separated Antares from Kitty Hawk; and, while Roosa boosted the CSM back up to a higher circular orbit, they checked out the lander for the descent. Almost immediately a problem with the LM's guidance computer was recognised by mission control at Houston. The computer's display was showing that the abort switch in the closed position when it was correctly selected open. Mission control requested Shepard to use an old fashioned remedy and give it a tap, which immediately cleared the fault, only for it to return a few minutes later. Normally the switch would be in the open position during the descent, which was controlled by the Primary Guidance and Navigation System's (pings) computer. If the secondary Abort Guidance System (aggs) recognised the switch as closed at any time during the descent, it would accept this as an abort signal, initiate separation of the descent stage, and fire the ascent stage engine to return the craft to orbit. Later, post flight analysis established that the fault was probably due to a loose piece of solder floating under the weightless conditions inside the switch, making and breaking contact intermittently.
It would be impossible to continue with the landing if any possibility of an inadvertent self-induced abort existed. Since it was only the switch that was suspect, the remedy was to modify the landing procedure programs in the guidance computer to by-pass the recognition of the abort switch procedure. This meant that Shepard and Mitchell had to manually feed in revised programs, devised by mission control immediately prior to the descent. The reprogramming was not completed as they disappeared behind the moon on the final orbit before initiating the LM's descent burn. Re-appearing on the other side, Mitchell only had minutes to copy the final programs and enter them in the correct order into the computer as the engine was started up for the powered descent by Shepard. Mitchell succeeded in installing the revised programs as they continued the powered descent.
Another problem cropped up as the descent proceeded through 32,000 feet. The ground ranging radar should have begun supplying height information at about 35,000 feet. At 30,000 feet, the radar had still not come on line; and the crew became anxious, as mission rules called for a mandatory abort of the landing at 10,000 feet if they were still without landing radar.
The radar operated in two modes, short, and long range. The long-range mode used at high altitude is switched to short range at 3500 feet. Resulting from the modifications to the landing program procedures for the abort switch problem, the logic circuit for the radar had been left in short range mode, unable to lock on above 3500 feet. At 20,000 feet, mission control instructed Mitchell to cycle the radar circuit breaker switch. He flipped the switch open and closed, which allowed the logic circuit to reset itself to long range, where it immediately began to supply the altitude and rate of descent information needed.
Antares descended towards undulating terrain with heavy cratering. On pitchover Shepard was easily able to identify Cone Crater and his prime landing area adjacent to it. He put Antares down within 175 feet of its target point on a sloping stretch of moonscape that gave the craft an eight degree list on touchdown. Their position was 3.65 degrees south, 17.48 degree west, approximately 350 miles west-southwest of the moons visible centre.
The First EVA, ALSEP Deployment
As Shepard descended the LM's ladder and stood on its footpad, Capcom Bruce McCandless remarked, 'Not bad for an old man.' Stepping onto the surface Shepard replied, 'Okay.. you're right. Alan's on the surface and it's been a long way, but we're here.' He was referring to the almost ten years since he had been the first American in space in the Mercury-Redstone capsule Freedom 7. His step onto the lunar surface also made him the only one of the original batch of seven 'Right Stuff' astronauts to walk on the moon.
Mitchell joined him on the surface and they took the contingency sample and set up a high gain, S-band antenna to improve communication links with earth. They also unloaded a new innovation, a Modular Equipment Transporter (MET). A two wheeled handcart like transporter, dubbed the 'rickshaw', to be used to carry tools and samples during the EVA's. Shepard also set up a colour television camera, this time equipped with a lens cap, pointing to a site some 500 feet northwest of the LM where they intended to set up the ALSEP package experiments.
Apollo 14's ALSEP now contained a greater array of scientific experiments than any previous missions. The experiments included:
- Active Seismometer
- Atmospheric Detector
- Charged Particle Detector
- Ionosphere Detector
- Laser Reflector (similar to that left by Apollo 11)
The active seismometer utilized a pair of geophones (laid out on the surface) and calibrated explosive charges (set off by the astronaut, using a hand held 'thumper) enabled the instrument to pick up the generated shock wave and measure the depth of the surface material. Several of the charges failed to go off, but a sufficient number worked to get the required data. Sampling and photography of the site took up the remainder of the four and a half hour excursion.
After close down of the first EVA Shepard and Mitchell spent an uncomfortable night trying to sleep, which was made more difficult by the sloping angle of the LM's floor. Both astronauts slept fitfully and the rest period was terminated an hour earlier than planned.
The Second EVA, Cone Crater
The second EVA included most of the missions geological sampling and the traverse to Cone Crater, which was nearly a mile away from the LM, to sample the material at its rim. They pulled the MET the first half of the walk over relatively flat ground, stopping at intervals to take samples and measurements of the moon's magnetic field with a portable magnetometer. The inclination of the crater's outer rim began to increase, until they were climbing a 10 per cent slope studded with boulders, making it necessary to take more frequent stops as their heart and breathing rates increased.
The lighting of the surface undulations, and the lack of recognisable objects to give perspective, was also making navigation difficult; and several times they had to stop to re-evaluate their position. The EVA's duration was extended by a half hour; and eventually it became obvious that they were not sure exactly how far they were from the craters rim. The decision was taken by Shepard, who was concerned that they were not leaving themselves enough time to complete the last sampling stop, to take their samples and return. In fact, they had reached within thirty feet of the rim of Cone; but, due to the far side crater wall being lower than the one they were climbing, they had been unable to recognise just how close they were to the rim.
>From the high ground with the sun behind them, they could now see Antares almost a mile away and make out the features that had eluded them on the uphill trek. Their return downhill was easier, during which the remaining samples were taken. Towards the end of the return trek tiredness was beginning to show; and it was becoming obvious that astronauts on future missions would require assistance to get about the moonscape, if greater areas were to be explored.
Golf on the Moon
Before closing out the EVA, Shepard had one last, unofficial task. From his suit pocket he produced a couple of golf balls. To the camera he said:
Houston... you might recognise what I have in my hand as the handle for the contingency sampler return; it just so happens to have a genuine six iron on the bottom of it. In my left hand I have a little white pellet that's familiar to millions of Americans. I'll drop it down. Unfortunately the suit is so stiff , I can't do this with two hands, but I'm going to try a little sand trap shot here.
With a one handed swing he moved the ball on the second try a couple of feet towards the camera. On his third swing he connected and the ball sailed out 'Miles and miles and miles.' Actually it landed in a nearby crater and the second ball joined it, followed by the golf club handle launched javelin style after the six iron head had been removed. The head returned to earth with Shepard and ended up on display in the US Golf Association, Hall of Fame in New Jersey.
Returning to the LM, and closing up the EVA, Shepard called back to Capcom Fred Haise, 'Okay Houston, the crew of Antares is leaving Fra Mauro Base.' Haise replied, perhaps a little wistfully, 'Roger Al.. You and Ed did a great job... I don't think I could have done better myself.'
After almost 36 hours on the lunar surface, Antares lifted off to rendezvous with Roosa in Kitty Hawk, using a new direct ascent trajectory to meet up at the highest point of its orbit, without having to make the major changes of orbit, as had previous missions. Transferring to Kitty Hawk, the crew sent Antares to crash back on the moon; and three hours later the service module's engine was fired up to send them back along the return path to earth. During the return flight, the crew demonstrated a number of experiments, including casting metals in zero gravity conditions. Some of these experiments were successful enough to warrant further investigation on later Skylab flights.
Splashdown in the early morning light of the 9 February, 1971, was just a half mile from its target area; and the crew were picked out of the Pacific by Sea King helicopters from the USS New Orleans and returned to quarantine for the following 15 days. They would be the last crew to be quarantined.
Apollo 14 concluded the intermediate 'H' type missions. The total sample collection of rocks weighed in at almost 95 pounds but the disadvantages of astronauts walking and navigating between sites was highlighted by the time expended in Shepard and Mitchell's climb to Cone's rim, which had curtailed the amount of useful work they were able to perform. The samples taken near the rim amounted to less than two pounds of individual rocks and one single rock of 20 pounds. Although they had reached their goal, they had not recognised it; and to the geology team it was a disappointing return from what was considered an important site. Nevertheless, the overall return of samples provided an insight into Fra Mauro's origins and indicated its age at 3.2 to 3.85 billion years. The portable magnetometer also found a surprisingly strong residual magnetic field in some of the surface rocks.