Getting lt All Together

By GEORGE E. MUELLER

The Apollo 9 and 10 missions were the learning phase of the program, coming as they did between the first tests of the command module in deep space on Apollo 8 and the lunar landing of Apollo 11.

Apollo 9 and 10 were missions designed to rehearse all the steps and reproduce all the events of the Apollo 11 mission with the single exception of the lunar touchdown, stay, and liftoff. The command and service modules and the lunar module were used in flight procedures identical to those that would later take similar vehicles to the Moon and a landing. The flight mechanics, the mission support systems, the communications, the recording of data - all these techniques and components were tested in a final round of verification.

We learned from those two missions how to develop our flight procedures. They are complex, at best, and for future missions we wanted to know exactly what alternatives we would have under a wide variety of circumstances to assure the safety of the astronauts and the success of the missions, in that order. Fortunately we had very few problems on both missions. Three reasons for that good fortune were the extensive ground tests, the simulation exercises which provided the crews with high-fidelity training for every phase of the flight, and the critical design review procedures.

The crews rehearsed and re-rehearsed their movements in ground simulators and in conditions of inflight weightlessness produced by parabolic flights in a converted Air Force KC-135 tanker and by neutral buoyancy simulations. They had started this kind of training as a crew months before the flight, gradually working toward proficiency and a degree of automatic response to the checklists, the pilots’ shorthand notes that were developed simultaneously. By the time they were ready for their actual missions, they had run through all the normal routines many times, and had thoroughly rehearsed emergency procedures for every imaginable trouble or failure.

The critical design reviews were fundamental to the testing and simulation programs. What we actually did was to go over every single part of the spacecraft to make sure that we understood how it worked, how it might go wrong, and what alternative procedure or backup system we had in case it did go wrong. The overriding consideration was, of course, crew safety; there always had to be at least one way back from orbit or from the Moon if something went wrong. These design reviews were done by a number of task groups, because there were too many spacecraft systems for any single group to consider, let alone understand to the required degree.

One of my areas of special interest lay in what we called software - the computer programs that provided the intelligence and control functions onboard the spacecraft and at the ground stations. General Phillips asked me to form a special software review group that met for several months and initiated some disciplines which, I believe, finally made it possible for the Apollo 11 lunar landing to take place when it did.

An interesting point about the Apollo 10 flight is that it did fail to do one of the steps that was later done on the Apollo 11 and which caused some brief moments of tension just before the lunar landing. On Apollo 10, the landing radar and the rendezvous radar never were operated at the same time. They are used for two different procedures, and at two different altitudes, so that there didn’t seem to be any need for simultaneous operation of the pair. But on Apollo 11, they wanted to check the operation of the high-altitude gate radar as they approached the surface of the Moon, and so it was left on. That radar and the landing radar were feeding information directly into the onboard computer in the Apollo 11 lunar module. Although the data from the altitude radar was not being used, it nevertheless was driving the input registers of the computer and thus forcing the central processor to decide at each cycle that the radar data were not germane.

THOSE COMPUTER ALARMS

Fortunately, in our software review we had insisted on one point: We had to have at least a 10-percent spare capacity in the memory of the onboard computer. We did that to provide for unforeseen contingencies, and that contingency occurred on the Apollo 11 lunar landing. On that mission we used up the 10 percent with those extraneous messages from the high-altitude radar, and in spite of the spare capacity, we nearly overloaded the landing computer. It set off alarms that caused a few seconds of fast thinking, but it was quickly put right and the landing went on to a safe touchdown.

All this critical design review was then followed by a review of all the things that happened during the dry runs before the final countdown, checking to make sure that there were no anomalies that hadn’t been identified and traced back to their origins. That was done in the last couple of days before the flight. What we were basically doing was making sure that everybody had done everything that could be done to assure the safety of the mission.

But you can only do so much in ground simulation and analysis, and then you’ve got to test the articles in actual flight. One example of this was with the docking mechanism, which presented no particular problems in ground tests and in simulation. But the first time it was tried in space, they had considerable difficulty getting the mechanism into place. That led to a very rapid redesign of the mechanism between flights, which was just one of the things accomplished in the very short time between flights. Looking back on it, it seems amazing that we were able to do a number of things on those two-month centers that would have been considered flatly impossible only a few months earlier. The key to that ability, though, was getting ourselves organized and then finding the will to do things. That made all the difference in the world on the Apollo program; there was the highest motivation, and it produced results, time and time again.

Of course, after the flights we had a thorough debriefing and evaluation of the mission, and of the behavior of the spacecraft and other systems, checking the actual results against our predicted performance, analyzing actual anomalies against ones that we had expected and planned for. The rigid discipline of postflight analysis and the preflight reviews were among the most important inputs of Apollo management to the success of the program.

FIRST MANNED FLIGHT OF THE LM

The Apollo 9 mission was to be the first manned flight in the lunar module, and the whole purpose of the mission was to qualify, in flight, that portion of the overall spacecraft system. Further, we wanted to show that the lunar module, in combination with the command and service modules, could perform its assigned tasks in weightless flight. It wasn’t necessary to go to the Moon for this work, so the Apollo 9 mission took place in Earth orbit. The conditions were the same, insofar as those qualifying tests were concerned, and we had the further advantage of a more comfortable situation in case any problems developed.

It was planned to fly a ten-day mission, approximating in time a complete trip to the Moon, a lunar landing, stay and ascent, and then return to the Earth. We had developed a mission profile that would put astronauts into the lunar module on three separate occasions during the flight, first of all to check a lot of procedures and other items, and second to do multiple activations and deactivations of the lunar module. This mission was the only one in which the LM was powered up and down more than once; it was done here with the intent of discovering anything that might go wrong, and to refine the procedures worked out in simulations.

The lunar module might well be called the first true spacecraft, since it was designed for flight only in the environment of space. Folded and stowed as it was in the nose of the Saturn V, its frail body caused some concern about its ability to stand up to the stress of a Saturn launch. Some of the earlier Saturn launches had shown what was called a pogo oscillation, named after the pogo-stick phenomenon. We wanted to make certain that the LM would be able to take that longitudinal acceleration and shock. We also wanted to make sure the mechanisms for extending its landing legs and pads would not be jammed by unusual loads in flight, and that the adapter between the LM and the rest of the spacecraft could take those loads.

Other objectives of the mission included checking propulsion system operation in both the docked and undocked conditions, to complete a rendezvous between the LM and the command module, with the LM being the active partner during the maneuver, and to demonstrate extravehicular activity from both spacecraft in order to evaluate the case or difficulty of that kind of task, and to check out the handholds, handrails, and localized illumination that had been developed for EVA.

The crew for Apollo 9 was commanded by James A. McDivitt. David R. Scott was the command pilot and Russell L. Schweickart was lunar module pilot. There was an initial three-day delay, not because of any equipment failure but because one of the crew had a cold. Liftoff occurred on March 3, 1969, at 11 AM The normal launch phase followed, and then the S-IVB stage was ignited to place the spacecraft in a nearly circular Earth orbit of about 102 by 104 nautical miles. That orbit was the arena for what was to follow. In a routine manner, the combined command and service modules were separated from the rest of the spacecraft, turned in space, and docked with the lunar module. About one hour later, the docked spacecraft were ejected from the S-IVB, using the ejection mechanism for the first time. From this point on, many of the events were done for the first time.

About two hours after the ejection, the crew fired the service propulsion system for the first time on that mission, in a burst that lasted five seconds. It was the first of several such firings planned to check the service module propulsion system and the resulting maneuvering capability of the docked and undocked spacecraft. That task also completed the list of work for the first day in orbit. It may seem as if there was very little for the astronauts to do on that first day, but it must be realized that much time is spent checking and rechecking onboard systems, the communications and telemetering links to the ground stations, the receipt of data, and all the myriad tasks that confront astronauts in space.

On the second day in Earth orbit, the crew of Apollo 9 also spent much time in systems checks. They fired the service propulsion system three times, each time with about a two-hour interval between firings. Two of the firings were long, lasting almost two and almost five minutes; the third was a shorter burst of less than a half-minute.

DESCENT ENGINE FIRED

McDivitt and Schweickart entered the lunar module on the third day in orbit and powered it up to check out its systems and to fire the descent engine while in the docked condition. The engine burn lasted more than six minutes, during which time the crew controlled the engine manually, and also demonstrated digital-autopilot attitude control. After returning to the command module, the full crew made the fifth of the docked maneuvers, using the service propulsion system.

Early on the fourth day, Schweickart and Scott began their extravehicular activity, that spectacular and exhilarating solo performance outside the spacecraft. Unfortunately, Schweickart had been affected by a form of motion sickness during the previous days, a difficulty that later led to a regime of zero-G flights for all crews during the last days before launch. But this time it affected the planned time line for the EVA, and it was decided to reduce the activities outside the spacecraft.

Schweickart went into the lunar module, which was depressurized, and left it by way of the exit hatch that would later be used by the astronauts who landed on the Moon. He stayed around the platform - the “front porch” as the astronauts called it - by that hatch for about three-quarters of an hour, checking the handholds and the lights that had been trained on specific portions of the spacecraft. Scott, meantime, had opened the command module hatch and clambered partially outside, still hooked to the spacecraft through a life-support umbilical system.

Schweickart was using a portable life-support system in his EVA, checking it for the first time outside. Both men detailed their experiences, took some photographs, and retrieved some thermal samples, testing the maneuverability of the space suits and the accessibility of the sample locations on the spacecraft. We had planned to have Schweickart move externally from the LM to the command module, to verify a way of getting from one spacecraft to the other if the tunnel were not available. This step was not completed beyond evaluating the specific handholds that would have been necessary to such a transfer.

THE LM ON ITS OWN

The fifth day of the Apollo 9 mission was the crucial test for the LM. Schweickart and McDivitt entered the LM, powered it up, and prepared to separate from the command module. They released the craft, and the astronauts were flying free in the LM. They backed away and rotated the module so that Scott, in the command module, could see that all the legs were down and extended, and that there were no physical failures in the craft itself. Then they fired the descent engine just enough to move the LM into a parallel orbit about three miles away from the command module. The mechanics of the orbit were such that the LM was on its own, but twice during each swing around the Earth? the two spacecraft were close enough so that Scott could initiate rescue operations should anything have happened to the EM.

For nearly six hours the two astronauts in the LM rehearsed the possible phases of the lunar approach and departure. They exercised the reaction control systems, fired the descent engine again, then jettisoned the descent stage, and then fired the ascent engine for the first time in space. From their adjusted position about 10 miles below and 80 miles behind the command module, they began their approach to a rendezvous and docking, much the same as the actual event to take place later on Apollo 11. The first phase of their rendezvous terminated temporarily with about a 100 foot separation, so that both spacecraft could be photographed. Then they docked, a solid and clean joining that verified the crews’ training and the performance of the docking and locking mechanisms. They jettisoned the ascent stage, and remotely fired its engine to insert it into a highly elliptical orbit around the Earth.

From here on, the rest of the mission was almost an anticlimax, because the performance of the spacecraft left no doubt as to its ability to make the lunar trip, complete with landing and departure. But there was still work to be done, and so for the remaining five days in orbit, the crew again and again exercised the service propulsion system, once to lower the perigee of their Earth orbit, once to test the propellant staging system, and once to head home to Earth. On the last four days, they also did a series of landmark tracking experiments, using visual sightings of Earth features which were observed and photographed. They also made a number of photographs with a multiple-camera assembly using different film emulsions to obtain pictures in different portions of the photographic spectrum. These were further augmented by pictures taken almost simultaneously with hand-held cameras, using conventional films.

Once out of orbit, following the eighth successive firing of the service propulsion system, the reentry was normal. They landed right on their target in the Atlantic, 241 hours after takeoff, and were recovered quickly by Navy helicopters.

Apollo 10 was different, because it did go to the Moon- or at least within 47,000 feet of it- in its rehearsal of the Apollo 11 mission. There had been some speculation about whether or not the crew might have landed, having gotten so close. They might have wanted to, but it was impossible for that lunar module to land. It was an early design that was too heavy for a lunar landing, or, to be more precise, too heavy to be able to complete the ascent back to the command module. It was a test module, for the dress rehearsal only, and that was the way it was used. Besides, the discipline on the Apollo program was such that no crew would have made such a decision on its own in any event.

Thomas P. Stafford was the Apollo 10 mission commander, with command module pilot John W. Young and lunar module pilot Eugene A. Cernan. They were launched on schedule at 11:49 AM, on May 18, 1969, about two and one-half months after Apollo 9 had set out on its successful test flight.

THE DRESS REHEARSAL

Launching was routine, as was the establishment of the Earth parking orbit that followed. After systems checks, and approval from Mission Control, the crew fired the S-IVB stage engine to leave the parking orbit and enter the translunar trajectory. Then they separated the command and service modules from the S-IVB, and turned to dock with the lunar module. Ejection of the docked spacecraft followed, as the crew performed a separation maneuver to increase the distance between the docked spacecraft and the S-IVB stage. Then they eased the S-IVB into a solar orbit by propulsive venting of its excess propellants.

The translunar trajectory had been established so precisely that it was not necessary to make the first midcourse correction, generally a routine step during the early phases of the flight toward the Moon. Finally, after a little more than a day in flight, a single translunar midcourse correction was done to make the flight path of Apollo 10 coincide with the trajectory planned for the Apollo 11 mission. Three days and four hours away from the launch pad, the crew fired the service propulsion system for almost six minutes, inserting the spacecraft into a lunar orbit. Apollo 10 now was orbiting the Moon in a circular flight path about 60 miles above its surface.

Stafford and Cernan entered the lunar module about six hours later to check the systems. They transferred some needed equipment, and moved back into the command module for a normal sleep period. They then recentered the lunar module to go through a complete systems check to prepare for the lunar-orbit rendezvous, the final check of the flight mechanics of the Apollo mission.

Just after two hours into the fourth day, the two spacecraft were undocked and separated. The crew performed its routine communications and radar checks, and then Stafford and Cernan began their descent toward the lunar surface by firing the descent stage engine. They let down to an altitude of about eight miles above the surface, the closest they were to go in that mission. Over one of the selected landing sites, they checked the landing radar, which worked successfully. After this descent, Stafford and Cernan maneuvered the LM into an elliptical orbit. 11 by 190 miles, to establish the conditions for their rendezvous with Young in the command module. They completed one swing around the Moon? and then staged the lunar module, firing its ascent engine in a simulation of a return from the lunar surface.

These words read rapidly, as if the performance they describe were done swiftly. But it must be appreciated that this rehearsal, which was planned to follow the schedule for the Apollo 11 as closely as possible, actually took more than six and one-half hours from the beginning of the descent toward the Moon until both spacecraft had docked for the second time for crew transfer back to the CSM.

FLAWLESS RENDEZVOUS

The rendezvous was flawless. It began with the usual maneuvering by the LM, using its reaction control system. Young, in the command module, nominally had nothing to do except to wait passively for the docking; the lunar module was expected to be the active seeker and mover in the rendezvous. But in fact he had to be prepared to take over the rendezvous if anything failed on the LM. So he checked the rendezvous every step of the way with sextant observations and ranging with very-high-frequency radio, working out the things he would have to do in the event of a lunar module system failure. The terminal phase of the docking began an hour later, and the lunar module nudged its way into the locking mechanism of the command module. The jubilant crews met back in the command module.

For the final day in lunar orbit, Stafford, Young, and Cernan spent their time in a series of experiments that would add to the general fund of Apollo knowledge. They tracked landmarks. worked on alignment exercises for the inertial platform, and took a series of stereo-pair and sequence photographs of the lunar surface, singling out features that would guide future landing-site selections. And then it was time for the return to Earth.

They fired the service module engine once again to move out of the lunar orbit and back onto a trajectory toward the Earth, using a fast-return flight path that would bring them back again in 54 hours. The flight path again was established with great precision; the only midcourse correction needed was done just about three hours before the reentry, and it changed the velocity by slightly more than two feet per second, or about one part in 20,000.

Fifteen minutes before reentry, they separated the command module from the service module. The command module bearing the crew streaked through the atmosphere; the parachutes deployed and let the spacecraft down on their target coordinates. The astronauts always made much of the accuracy of their landings, with a pool going to the crew landing closest to the target. (In fact, the navigation and guidance accuracy was such that the spacecraft computers pinpointed the target location better than the recovery ships were able to. Later, ships used inertial navigation that was as accurate as that in the spacecraft, but their captains stood off by a mile or two from the landing point to avoid any possibility of a collision.) Navy helicopters swung over their rafts, lifted the crew and took them back to the recovery carrier, the USS Princeton, within 39 minutes after the craft had hit the water. About an hour later, the spacecraft itself was hoisted. charred and dripping, onto the deck of the Princeton.

These two flights had been successful; more, they had been nearly trouble-free. The confidence they gave to the planned Apollo 11 mission was almost tangible, erasing any doubts about the pace and the direction of the program before Apollo 9 and 10. The thoroughness of the approach, the critical design reviews, and the extensive test and simulation work on the ground had successfully demonstrated the readiness of equipment and crews for the next step.

Everything had been done that would later be done by the crew of Apollo 11, except for the actual touching down on the Moon’s surface, the stay there, and the liftoff. Apollo 9 and 10 had done all they could to prepare the entire team- astronauts, flight controllers, ground-support personnel, and management - for the great adventure.