Apollo 16 Flight Summary

By Tim Brandt

INTRODUCTION

At its inception, the Apollo programme was intended to provide the technological basis for a wide ranging exploration of space, including the possibility of supporting a lunar landing. After President Kennedy's decision to land an American on the Moon by the end of the 1960s, Apollo was focussed towards that goal and other missions were put on hold. As the decade progressed, the basic Apollo goal of "landing a man on the Moon and returning him safely to the Earth" was extended to include a modicum of scientific exploration. A series of missions were designed, designated by the letters A to J. Unmanned tests and early missions made up those designated A to F. G designated the basic ability to land on the Moon and to carry out a limited range of experiments. Apollo 11 was the only G mission, and was to be followed by H missions of longer duration, intended to be followed by I missions mapping the Moon from lunar orbit, and J missions providing for longer stays on the surface and more scientific content. Missions up to Apollo 20 and beyond were envisaged. However, cuts in NASA's budget required sweeping changes. After Apollo 11, three H missions were flown, including Apollo 13. The I missions were cancelled. Also cancelled were Apollos 18 to 20, so that the remaining Saturn V launch vehicles could support the Skylab space station. In the event, further budget cuts caused only one Skylab to be launched; the last two Saturn Vs became museum pieces. But the last three missions, Apollos 15 to 17, were redesignated as J missions and were to fly many of the scientific experiments that had originally been planned for the later missions. Uprated Saturn Vs permitted the weight of the Lunar Modules (LMs) to be increased, providing supplies for a longer stay on the surface, and permitting the carriage of a battery-powered Lunar Rover vehicle. The Command and Service Modules (CSM) were also modified to contain the extra consumables needed for longer missions. Most significantly, an unused bay of the Service Module was filled with the Scientific Instrumenation Module (SIM). The SIM bay comprised an extensive set of remote sensing equipment, designed to record the surface, sub-surface and orbital environment of the Moon.

The first J mission was Apollo 15, launched on 26 July 1971. This was a triumphant success, clearly demonstrating the level of science that could be carried out by a trained crew and an appropriately equipped spacecraft. Apollo 15 returned to Earth on 7 August 1972, with preparations already well underway for the next mission. Apollo 16 was due to launch on 17 March 1972. The spacecraft for Apollo 16 were almost identical to those used on Apollo 15. Indeed, in many respects, the mission was intended as a re-run of Apollo 15, using the same experiments and tools to explore a different part of the moon. However, it was to prove a significantly more more challenging mission and was to experience more technical problems than almost any other mission. The final success of Apollo 16 was due almost entirely to the skills, knowledge, and experience of both the flight crew and of the many people who supported it from the ground. In the history of manned spaceflight, Apollo 16 comes only narrowly behind Apollo 13 and Skylab 2 as an example of how a manned space mission can successfully overcome adversity. Right until the end of the Apollo programme, the spacecraft was capable of demonstrating new faults and problems, and required a huge level of support. It was an experimental vehicle, and in fulfilling almost all of the mission objectives despite numerous technical challenges, Apollo 16 demonstrated the maturity and confidence of the whole NASA team.

THE CREW

The crew of Apollo 16 had been selected over a year in advance, on 3 March 1971. The Mission Commander was to be John W. Young, by then the most experienced of the astronauts still flying. His experience would balance that of the other 2 crew members, who were both rookies. John Young was born on September 24, 1930, in San Francisco, California. He received a B.S. degree in aeronautical engineering from the Georgia Institute of Technology in 1952 and, after a career flying with the US Navy, was selected for the second group of astronauts in 1962. He was pilot of Gemini 3, backup pilot for Gemini 6, command pilot on Gemini 10, backup command module pilot for Apollo 7, command module pilot for Apollo 10, and backup commander for Apollo 13. As a member of the Apollo 16 crew, he became the ninth man to walk on the Moon. Following this mission, he was backup commander for Apollo 17 and flew the Space Shuttle on STS-1 and STS-9.

The Command Module Pilot  was Thomas (Ken) Mattingly II. Ken Mattingly was born on March 17, 1936, in Chicago, Illinois. He received a B.S. degree in aeronautical engineering from Auburn University in 1958, and after flying with the US Air Force, he was chosen with the fifth group of astronauts in 1966. Scheduled to be command module pilot on Apollo 13, he was replaced by his backup becuse he had been exposed to measles. After flying on Apollo 16, he served as backup commander for Space Shuttle flights STS-2 and STS-3 and was the commander for STS-4 and STS 51-C.

The Lunar Module pilot was to be Charles Duke. Charlie Duke was was born on October 3, 1935, in Charlotte, North Carolina. He received a B.S. degree from the U.S. Naval Academy in 1957, and an M.S. degree in aeronautics and astronautics from the Massachusetts Institute of Technology in 1964. Like Ken Mattingley, he was chosen with the fifth group of astronauts in 1966. He was backup lunar module pilot on Apollo 13 and Apollo 17 and was the tenth man to walk on the Moon. After Apollo 16 he retired from NASA.

THE LANDING SITE

The landing site had also been selected; the Descartes region in the lunar highlands. The landing site was closer to the lunar equator than that of Apollo 15, requiring an orbital inclination of only 9º compared to the 26º of the previous mission. The aim was to study the material of the Moon's highlands, which was thought to be much older than  that of its "seas". Pictures of the Descartes region taken from Earth and from lunar orbit also showed features that were thought to indicate possible volcanoic activity in the past.

THE MISSION PATCH

The mission patch was selected, as tradition decreed, by the crew members themselves. According to Charlie Duke, "Each crew selected their own special flight patch. John, Ken and I had several basic ideas we wished to incorporate to commemorate our mission: patriotism, teamwork, and the moon. We wanted these ideas, plus the mission number and the names of the crew, to be displayed on our patch, and talked with a NASA graphic artist who designed exactly what we wanted. Basically, the design was a brown and white eagle with wings outstretched, perched atop a red, white, and blue American seal, over a gray lunar surface background. To show teamwork, the yellow NASA wishbone symbol of flight was placed on top of the seal, and then across the seal were written the words 'Apollo 16'. Circling a blue and gold border were our names - Young, Mattingly and Duke - and sixteen white stars to emphasize outer space and the number of our flight. We were very proud of this patch, which to us symbolized Apollo 16." Only one other Apollo mission had used a shield motif, and that had been Apollo 10 on which John Young was also a crew member. The "wishbone" element was actually a stylised wing, taken from the official NASA seal designed in 1959. According to a NASA description of the insignia, "the red chevron is a wing representing aeronautics (the latest design in hypersonic wings at the time the logo was developed)."

LAUNCH  AND FLIGHT TO THE MOON

Apollo 16 was launched from the Kennedy Space Centre at 12:54 pm Eastern Standard Time on 16 April 1972. The launch went smoothly with the crew experiencing vibration levels similar to those of previous missions. Both the first and second stages of the Saturn V performed as expected and the spacecraft entered orbit less than 12 minutes after lift-off. Once in orbit, the crew acclimatised to zero-gravity, and readied the spacecraft for Trans-Lunar Injection. Despite a busy timetable, Young, Mattingly and Duke had the time to enjoy the view and observe thunderstorms and fires in Africa. A number of minor problems were noted during the time in orbit; within minutes the crew had to check the settings on the CSM's Environment Control System as telemetry indicated a potential leak in the primary coolant loop. While the spacecraft was over Australia on its first orbit, other problems developed with the S-IVB stage's attitude control modules. First, the Number 2 Module experienced a failure of the helium regulator causing gas to vent overboard continuously. Then another helium leak was detected in the Number 1 Module. In a further fault the Instrument Unit between the Spacecraft Launcher Adaptor (SLA) and S-IVB stage leaked gaseous nitrogen from a bottle supporting a temperature control system. As a result of these failures, the crew were tasked to prepare to use the Apollo spacecraft Reaction Control System to maintain attitude control of the S-IVB if required.

After two orbits of the Earth, the S-IVB was fired a second time, to perform the Trans Lunar Injection burn which placed Apollo 16 on course to the Moon. During this firing, the S-IVB exhibited a similar high-frequency vibration to that which had been noted during the climb to Earth orbit. The vibration levels increased as the burn progressed, causing concern that the S-IVB might have to be shut down prematurely. However, the vibration levels remained within limits, and 5 minutes and 24 seconds after the start of the burn, Apollo 16 was travelling at 10.8 kilometres per second towards where the Moon would be in three days' time. Six minutes later, the crew separated the CSM from the SLA, moved away 15 metres, turned round, and headed back to dock with the LM. The docking went extremely smoothly and the crew were able to see the effect of the CSM thrusters on the thin skin of LM. After docking, the crew noted particles appearing to vent from a number of  points on on the LM; these later these turned out to be flakes of the paint which have been applied to reduce the temperature of the propellant. Although the flaking paint caused no direct problem, the particles made it harder to use the spacecraft's optical navigation system as the particles looked like stars when seen through the optical sight. Once the LM had been withdrawn from the S-IVB, the stage carried out an evasive maneuver to prevent any risk of collision with the spacecraft. Its work finished, the S-IVB was placed on-course for an impact with the Moon which would provide a valuable seismic data. A minor problem during the the evasive manoeuvre was the failure of the monitor of the crew's television camera, but a good picture was still transmitted to Earth.

As a result of concern over the particles coming from the LM, the crew's first internal inspection was brought forward to just over eight hours after launch, rather than at the 55-hour point as originally planned. This visit was short and confirmed that all of the LM systems were in good condition with none of the feared leakage of propellant. The crew paid two further visits to the LM during the flight to the Moon, finding few problems apart from some small items of build debris that had become dislodged in zero gravity.

During the trans-lunar flight, Young, Mattingley and Duke carried out a number of scientific experiments. These included experiments to confirm whether the light flashes seem by astronauts on previous missions were due to cosmic rays. The crew also tested a lunar sample originally collected on Apollo 12 which was being returned the Moon to test the effects of changes in magnetism. Thirty hours and 39 minutes into the flight, the crew carried out a 2-second burn of the spacecraft's main engine, the Service Propulsion System (SPS), to adjust their trajectory in order to achieve the target lunar orbit. A second planned burn was not required. While Apollo 16 was still 211,000 kilometres above the Moon the SIM bay door was jettisoned to uncover the suite of scientific instruments. A significant sound and shock was felt by the crew and a considerable amount of debris was produced as the SIM bay door tumbled away at a considerable speed . Just before Apollo 16 entered lunar orbit, the crew could see almost half the Moon illuminated by Earthshine; there was sufficient light for details of craters and other major features to be visible.

AT THE MOON

At 74 hours and 17 minutes into the mission, on Wednesday 19th April, Apollo 16 went behind the Moon, losing contact with Houston. Eleven minutes later the crew fired the SPS engine for six and a quarter minutes to slow down to orbital velocity. Once in orbit, the crew admired the view, with John Young pointing out the features he had seen on his previous lunar flight. At the end of the second orbit, the crew again fired the SPS engine to move spacecraft into an orbit of 20 by 108 kilometres, to minimise the propellant the LM would have to use to desend to the surface. In a change from the flight path used on Apollo 15, it was intended that the LM's descent engine would be ignited one orbit early, to allow a 6-hour longer stay on the surface.

After a good night's rest the crew were up and busy, shortly before passing behind the Moon on their 9th orbit. At this point they experienced problems with the boom that extended the mass spectrometer out from the SIM bay; this stuck in a partially deployed position. As a result, Mission Control decided that Young and Duke would visually check the boom's deployment after the LM had undocked. Young and Duke then proceeded to power up the LM in preparation for thedescent. Because of difficulties that Duke had experienced with his spacesuit during earlier tests, both Young and Duke entered the LM approximately forty minutes earlier than scheduled. In the event, Duke's spacesuit did not cause any problems, but Young's did, leading to a delay of approximately ten minutes. The crew found the activation and checkout phase to be busy and were finally ready only ten minutes early. During the checkout the LM's steerable antenna jammed in the yaw axis. This could be not be corrected and, as a result, Mission Control was unable to automatically update the LM's computer through the radio up-link; the computer had to be manually updated by the crew using data read to them from the ground. Other anomalies included excessive pressure in one of the LM's two RCSs. After these two problems and had been corrected, Young and Duke undocked the LM from the CSM to a cry of "we're sailing free". At this point, the two spacecraft assumed more personal call-signs; the CSM was "Casper", after the friendly ghost in a popular TV series, while the LM was "Orion", after the constellation. For the rest of the pass over the front side of the Moon, Mattingly prepared to move Casper into a circular orbit, while Young and Duke prepared Orion for the descent starting 26 minutes after they next came into view around the moon.

At this point, Apollo 16 suffered its most significant problem. When both spacecraft came back into view from Houston, Ken Mattingly reported a fault with the gimbals that allowed control over the direction in which the SPS was pointing. When one of the two parallel systems was used to control the engine, its electric motors appeared to oscillate. Although one of the control systems was functioning perfectly, there was no back-up available. Correct operation of the SPS would be critical if the LM could not rendezvous with the CSM. If this happened, Ken Mattingly would have to use the SPS to rendezvous with the LM. Moreover, before a landing attempt, the LM descent engine provided an alternative means of return to Earth but if the SPS failed to function later, all three astronauts could be stranded in lunar orbit. Under the mission rules, such a fault meant that a lunar landing could not be attempted. While Mission Control reviewed the results of tests of the SPS gimbal motors, Young and Duke waited, somewhat impatiently. Mattingly also moved Casper back into close formation with Orion by a "brute force" rendezvous. At the end of this, the two spacecraft were approximately 150 metres apart again. By this time, other problems had occurred. The LM's leaking helium regulator had now pressurised the propellant tanks to a dangerously high level again. It had been expected that the descent would consume propellant in the tanks, making room for the excessive gas. To reduce the pressure, the crew fired the LM's thrusters, even though this was a waste of precious propellant. Before the two spacecraft passed behind the Moon again, Houston told the crew that the final decision on landing would be made during the next orbit. After extensive discussions in Houston and at the Rockwell plant in California where the CSM had been built, Mission Control decided that the system was serviceable enough for the landing attempt to go ahead. All three crew were very much relieved.

Powered descent was now planned to start 5 hours 42 minutes later than planned, on Orbit 16. However the delays meant that descent would now begin from a greater height than any previous mission, 20.1 kilometres, and 4.8 kilometres south of the planned ground track. There would be less propellant available for hovering near the surface as the LM would have to move north during the main breaking phase, consuming extra fuel and oxidiser. Meanwhile Mattingly carried out one more SPS burn, to bring the Command Module into a circular orbit. Young and Duke were given a Go for descent about one and a half orbits ahead of time. Because of the failure of its steerable antenna, and in order to improve communications with Mission Control, the LM was yawed 20 degrees to the right to point its omni-directional antenna towards the Earth. This then gave sufficient signal strength for Mission Control to update the LM's computer automatically.

The descent of Orion towards the lunar surface went smoothly, although the fuel level indication was about two percent lower than the oxidiser indication throughout. The landing radar lock-on to the surface occurred at an altitude of approximately 15,000 metres. At 6,000 metres John Young was able to crane his head to see features adjacent to the landing site, while by 4,000 metres he could see the entire landing site. The descent propulsion system throttle down occurred on time, and at 2200 metres the LM pitched forward into its landing attitude. At this point it became clear that Orion would land approximately 600 metres north and 400 metres west of its target, unless corrective action was taken. Using the guidance computer, John Young redesignated the landing target, effectively telling the landing computer to offset where it was guiding the spacecraft to land. Despite this, it became clear that Orion was going to end up slightly north-west of its intended location. At about 140 metres above the Moon, Charlie Duke saw the shadow of the Lunar Module appear on the surface. As Orion descended below 60 metres, John Young yawed the spacecraft right, allowing him to see the shadow also. This then allowed both the crew to estimate their altitude above the surface and their descent rate. John Young flew the LM slowly forward as the lunar module descent rate reduced from eleven to five feet per second. As a LM descended below 25 metres, small traces of dust were blown across the surface by the engine. This increased as the LM descended to surface but John Young was still able to see craters and small boulders on the surface despite this. Orion landed at ( time), only 270 metres north and 60 metres west of its original target. Charlie Duke greeted their success with an exuberant "Wow! Wild man! Look at that!". John Young was more laconic - "Well, we don't have to walk far to pick up rocks, Houston. We're among them!"

Immediately after touch-down, Young and Duke powered-down the LM to conserve its batteries. They then configured the LM for their stay on the lunar surface. Once this was complete, the crew removed their suits, and ate their first meal on the Moon. Afterwards, they set up the cabin for sleep, as the delays in orbit had required significant changes to their plans for exploration. Since there would be few reserves left if the mission continued for its originally-planned 12 days, Mission Control decided that Apollo 16 would spend one day less in orbit around the Moon after the surface exploration had been completed. This would give some contingency time should further problems arise. It was also agreed that the SPS should not be fired more than necessary until the critical burn to return the crew to Earth. Because of this, a planned burn to change the orbital plane of the Command Module was cancelled, although this meant that the mission would no longer be able to complete the planned surveys of the surface from orbit. It also decided to cut the duration of the third Extra Vehicular Activity (EVA) from seven hours to five, to improve the crew's rest schedule.

On the morning of February 21st April 1972, John Young stepped down from Orion's ladder onto the surface of the Moon, making him the ninth person to do so. The crew were about 144 minutes ahead of the revised schedule as they began their first EVA. Charlie Duke and John Young's first task was to deploy the Lunar Rover, and put up the US flag. After a photocall, with John Young smartly saluting while jumping in the low gravity, they then positioned an ultraviolet camera a short distance from the Lunar Module. They then had to place the Apollo Lunar Surface Experiment Package (ALSEP) equipment on the lunar surface. Unfortunately, while the crew were deploying the heat transfer experiment , John Young tripped over some of the wiring that was had been laid out previously. This pulled the cable free from the experiment, preventing it from functioning. After investigating, the chagrined astronauts concluded that nothing could be done to recover the experiment, and continued to lay out the other experiments. After about four hours on the lunar surface the two astronauts climbed aboard the Lunar Rover and drove approximately 1.4 kilometres to a crater planned as the first site for their geological investigations. They then drove back the Lunar Module, stopping at another crater en-route. Back at the landing site, John Young took the Lunar Rover on a "Grand-Prix" test drive to check its handling and performance, while Charlie Duke fimed the event. After seven hours lunar surface, the tired crew re-entered Orion, and, after a and prepared to sleep at the end of their first day on the Moon.

Meanwhile, while John Young and Charlie Duke were exploring the surface the Moon, Ken Mattingly remained in orbit in the Command Module. He had an extensive set of experiments and observations to carry out using the equipment in the SIM bay, as well as hand-held cameras. He had also been trained to sketch subtle features on the surface that might not be obvious from photographs alone. In assessing what he was required to do it must be remembered that at an average orbital height of approximately 110 kilometeres and a speed of almost 6000 kilometres per hour, his average viewing time for any particular target was only just over one minute. There was also a significant conflict between the best spacecraft attitude for visual observation of the Moon's surface, and the required orientation for the some of the SIM bay instruments to carry out their work. Therefore Ken Mattingly had to keep pointing the Command Module in different directions to match a complex and busy observation schedule. The scientific instruments also posed their own challenges, reflecting both their complexity and the rapidity with which the complex suite of equipment had been developed. The first time the Panoramic Camera was turned on, it caused an indicated under-voltage reading on one of the CSM's electrical systems, and initiated the spacecraft Master Alarm - an adrenalin inducing event at any time but especially during solo operations in lunar orbit. The camera was immediately deactivated, although subsequent analysis suggested the problem was caused by the spacecraft's heaters coming on simultaneously with the camera, leading to an excessive power drain. The Mass Spectrometer boom did not properly retract following its first extension. Although the Mass Spectrometer was able to operate effectively, it stuck near its fully deployed position later in the mission and had to be jettisoned. The Mapping Camera also did not function quite as planned and was later found to have problems with its glare shield. The Laser-Altimiter, designed to accurately measure the spacecraft altitude, operated at a reduced efficiency and finally failed just before its last scheduled operating period. All of this made for a very busy schedule, while Ken Mattingly continued to monitor the progress of his colleagues in exploring Descartes.

On the second day on the lunar surface, John Young and Charlie Duke again prepared to explore the surface. Less than 4 hours after waking up, they were back outside Orion and ready to start another seven-hour EVA. This time they were to head south towards Stone Mountain, a peak several kilometers away. After three-quarters of an hour loading the Rover and checking its systems, they set off. Over the next seven hours 23 minutes, John Young and Charlie Duke carried out an intensive geological investigation of nine different sites while covering brackets kilometres). By the time they returned to the Lunar Module, they were covered in the fine moon-dust. Although they did their best to clean themselves off, the amount of dust that was on their equipment and that ended up in the cabin was a major concern. A considerable amount of dust ended up on their suits around the helmet neck ring, the emergency oxygen system and on their portable life-support system backpacks. Most of this dust then ended up on the floor of the lunar module. The dusty floors were cleaned by wetting a rag, caking the dust into mud, and picking it up with the rag. However, there was no way to remove the dust from the Velcro on the floor. The crew's liquid-cooled under garments, which they wore inside their spacesuits, also became covered in dust. By the time they had removed their spacesuits, the astronauts hands were filthy and they were covered in dust up to the elbows. In the event, they could not clean their hands effectively until they returned to orbit. The amount of dust gave John Young and Charlie Duke significant concern in case it got into equipment and caused either the Lunar Module or their suits to fail. To add to their problems, they also experienced significant problems with the orange juice drinks bags that were fitted into the spacesuits. These leaked copiously. Charlie Duke ended up with orange juice all over his face and the neck ring of his helmet, making it almost impossible to remove his helmet . The crew also experienced significant problems when preparing for EVA as the tool harnesses and antennae on their suits kept catching on the fittings in the cabin.

After a third night's sleep on the surface, the two astronauts started their third and last EVA. Their first stop was four-and-a-half kilometres north, at a point on the rim of North ray crater, a large formation nearly one kilometre across. This journey took them thirty five minutes. On the edge of North crater they found the largest boulder the Apollo astronauts had been able to investigate so far. This was a size of a house, and it soon became known as "House Rock". Further driving and exploration eventually brought to crew back to the vicinity of Orion, where they parked the Rover, and re-entered the Lunar Module with those experiments which would be returned to the Earth. Although their time on a lunar surface had been less than planned, John Young and Charlie Duke had broken records for the time spent there, and for the weight of the samples that they were bringing back. The crew then prepared to return to orbit. The ascent stage engine fired as planned and Young and Duke rode the Ascent Stage to orbit. Orion's radar locked onto Casper at a range exceeding 150 miles, and a near perfect rendezvous was achieved. At this point both spacecraft again passed out of sight from Houston around the Moon. When they next rounded the Moon, the two spacecraft were less than six kilometres apart, but a planned TV broadcast of the docking operation proved impossible because of the faulty high gain antenna on the Lunar Module. Young and Duke then inspected Casper's SIM Bay to see if they could determine why some of the experiment were not functioning as planned. Ken Mattingly carried out a similar examination of Orion, noticing that the outer thermal blankets on the rear of the Lunar Module were badly damaged, and hanging off the spacecraft. These had been torn loose at engine ignition on the surface the Moon, but the thermal blankets underneath appeared to be intact.

AND RETURN

After a successful docking with Casper, John Young and Charlie Duke then cleaned Orion's interior as well as they could, to minimise the amount of dust that would be transferred into the other spacecraft. This was not fully effective, and the transfer of equipment and lunar samples ended up with a large amount of dust floating around the Command Module cabin. Attempts to clean this up with the Command Module vacuum cleaner had to be abandoned after this failed - somewhat incongruously given that here was ample vacuum outside! In a change to the planned schedule, Mission Control now required the crew to sleep before the Lunar Module was jettisoned. In the event, the hand-written amendments that this required to the Flight Plan and to the crew's checklists ended up with these becoming very messy. This may have been partly responsible for the likely failure to leave one of the switches in Orion in the been correct position when the crew carried out their final checks. Consequently, when Orion was jettisoned from Casper, it began tumbling and did not fire its RCS thrusters in preparation for the engine burn to remove it from orbit. It was nearly a year later that Orion finally crashed into the lunar surface. An hour later the crew released a small sub-satellite carried in the SIM Bay. This had been intended to go into a long-term orbit round the Moon so that it could be tracked from the Earth. But because of the earlier problems with the SPS engine, the planned burn to put the CSM into the correct orbit had been cancelled the sub-satellite could not be placed into the correct orbit. In the event, the sub-satellite lasted less half its anticipated life in orbit. Less than five hours later, at the beginning of its 65^th orbit round the Moon, Ken Mattingly fired the SPS engine on Casper to leave lunar orbit and return to Earth. The SPS performed perfectly, despite the earlier concerns.

During the long coast back to Earth, the crew rested from their exertions, and continued to perform a range of scientific experiments. Ken Mattingly also had his opportunity to leave the spacecraft, albeit only briefly, to retrieve the film cassettes from the SIM Bay experiments. While Charlie Duke watched from the Command Module hatch, Ken Mattingly used the opportunity to report on the condition of the SIM Bay equipment and of the Service Module in general. During his EVA, the crew also carried out an experiment exposing earthly microbes to direct sunlight in the vacuum. The rest of the Trans-Earth coast was relatively routine, albeit with its own ration of technical problems for the crew and Mission Control to solve.

On 27 April, and with only the 2.7 metre-tall Command Module remaining of the 111 metre vehicle launched just eleven days before, Apollo 16 re-entered the Earth's atmosphere at eleven kilometers per second. Less than 14 minutes later, the spacecraft splashed down to the waiting US Navy recovery fleet, 350 kilometres south-east of Christmas Island. Thirty-seven minutes after that, John Young, Charlie Duke and Ken Mattingly were on the deck of the carrier USS Ticonderoga. Apollo 16 was over as a flight, although the analysis of its results would continue for years.

Apollo 16 was a further success in the Apollo project, and added very significantly to scientific understanding of the Moon. It also demonstrated the ability of highly trained astronauts to overcome a series of problems, many of which could have caused the mission to fail. Perhaps the last word should be left to John Young. "I think that we calculated once that we worked on about 99 things during the mission that we either solved in real time or that the ground had to solve. It was the most of anybody, I think. But we had been trained to do that. That was what our line of work is."

References:

Apollo 16 Mission Report. MSC07230. NASA, 1972.
Apollo By The Numbers: Richard W. Orloff. NASA, 1996.
The History of Manned Spaceflight: David Baker. Crown, 1981.
On The Moon With Apollo 16: A Guidebook to the Descartes Region. Gene Simmons. EP-95. NASA, 1972.
Apollo 16: The NASA Mission Reports Volume1. Robert Godwin. Apogee Books, 2002.
Moonwalker. Charlie and Dotty Duke. Thomas Nelson, 1990.
Apollo Lunar Surface Journal: Apollo 16. Eric M. Jones. NASA, 2002.

© 2003 Tim Brandt. All rights reserved.

Last updated: 2019-01-19

Last updated: 2016-06-21