Moon Lander: How We Developed the Apollo Lunar Module (Smithsonian History of Aviation and Spaceflight)

by Kelly, Thomas J.

  The crew repressurized the LM, doffed their backpacks, and stowed the lunar sample containers, cameras, and other equipment. When the cabin was shipshape, they depressurized it and opened the forward hatch for the last time in order to throw out their backpacks and other items no longer needed. Repressurizing once more, they then removed their helmets and gloves, settling down for about six hours of eating and sleeping before preparation for liftoff. This time they really slept, and so did I back in the motel. But I kept waking up and worrying about a micrometeorite strike or window failure causing a sudden depressurization, leaving the crew gasping for breath in an airless cabin. I knew the odds were overwhelmingly against this, but that did not stop my worrying.

  Although the descent and landing was a greater challenge to piloting skills and involved the unknowns of the lunar surface, I thought the liftoff from the Moon was the most daring event in the LM-active portion of the mission. The challenge of performing launch operations with only two men, a quarter of a million miles away from Earth, seemed impossible when compared with the eight thousand people and weeks of preparation required to perform the same function from Cape Kennedy. It was a measure of how successful we had been in keeping the LM simple in design and operation, and of the competence of the astronauts and the thoroughness of their training, that lunar surface launch was not only possible but even seemed a natural part of the mission.

  The liftoff did not allow for introspection or corrective action—either it worked or it did not. At the same instant as the ascent rocket engine’s valves opened and ignition occurred, a string of explosive charges shattered the bolts and the nuts holding the ascent and descent stages together, a guillotine cut a four-inch-diameter umbilical wire and tubing bundle connecting the stages, and a deadface connector removed power from the severed wires in the bundle. If the engine did not ignite or the stages failed to separate, the crew would be doomed to remain on the Moon, dying before the watching world, a fate too horrible for me to contemplate.

  For the next seven minutes the crew stood a foot in front of the ascent rocket engine as it fired with only a thin aluminum can between them and the combustion chamber. On Earth, rocket firings were conducted from the safety of a sandbagged and partially buried blockhouse behind thick walls of reinforced concrete. The astronauts were courageous, yet confident in the integrity of their spacecraft and all who designed and built them. It was a trust that weighed upon me heavily.

  Tension mounted in Mission Control as the crew went through the prelaunch countdown, and then bang! it happened, just as it was supposed to. Liftoff was smooth—from the windows the pilots could see a shower of torn insulation and Aldrin glimpsed the American flag being blown down. There was little feeling of acceleration, but when the ascent stage pitched over to its climbing trajectory the windows faced the surface and they could see that they were going faster and faster. The crew called out some landmarks they recognized on the way up. It was like a high-speed elevator ride, with little noise and vibration despite the proximity of the rocket engine and no sensation of speed if you did not look out the window.3 The engine shut down on schedule, placing them in a nearly perfect orbit for rendezvous.

  I was much less worried about the rendezvous and docking maneuvers. These operations had been practiced many times on Earth in high-fidelity simulators and verified in flight on Apollos 9 and 10. Moreover, it was a non-time critical “slow motion” operation with several backup paths using independent equipment. Collins in Columbia had a checklist of eighteen different procedures to use if the primary method failed.4 The probe-and-drogue docking mechanism, with its capture latches firmly holding the two spacecraft together, was the only element for which there was no direct backup, but it was a relatively simple, rugged design with broad dimensional tolerances.

  On Apollo 11 the rendezvous maneuvers were skillfully executed as planned. The reunion was accomplished with the primary method using the rendezvous radar, right in the center of the tolerance band. The hard docking was a bit more sporty—Collins had to manually counter a sudden yaw disturbance just before the latches snapped closed. He readily removed the probe and drogue for the lunar explorers to rejoin him, relieving his recurring worry that the drogue would stick in place, blocking access from the LM.5 Everything worked, and the three were joyously reunited, none more relieved than Collins, who had agonized during his stay in lunar orbit over how he would deal with returning alone to Earth if Eagle and her crew did not make it back.6 They transferred equipment, cameras, and the lunar samples into Columbia, leaving the probe and drogue, their functions completed, in Eagle for disposal.

  With the crew safely aboard Columbia, Eagle was jettisoned, moving away proudly with her attitude control thrusters firing, into a low orbit that would eventually crash on the Moon. Howard Wright and I took off our headsets and looked at Eagle’s data on the screen for the last time. Our part of the mission was completed; there was nothing more that Grumman could do to help Apollo 11. We packed up our reference books and papers, accepted congratulations from our NASA and North American colleagues in the SPAN Room on the LM’s sterling performance, and headed for the airport and home.

  Of course there was no celebration until the crew was safely aboard the aircraft carrier USS Hornet. Two and a half days after Eagle was jettisoned, I watched the orange-and-white-striped parachutes lazily floating down toward the blue Pacific, surrounded by my Grumman friends and associates in the Mission Support Center in Bethpage. We broke into a roar of triumph as the TV showed the conical command module splashing into the water and the parachutes deflating and gently settling down beside it. From the screen we saw American flags and cigars broken out by the flight controllers in Mission Control in Houston—we made do with arm waving and cheers. It was a moment of elation, of heart-pounding thrills usually reserved for athletes or warriors, for a successful team effort, a group victory achieved against long odds. In reaching the Moon and safely returning, the hundreds of thousands of ordinary Americans who had labored for most of a decade on the Apollo program briefly shared this privileged feeling.

  16

  Great Balls of Fire!

  Apollo 12

  Pete Conrad was unlike most of the other astronauts. Voluble, excitable, enthusiastic, and totally approachable, he had none of the “right stuff” reserve displayed by some of NASA’s superstars. Nor, like many of his colleagues, did his appearance suggest that Hollywood’s central casting had chosen him for the role of spaceflight hero. Short, balding, and with widely spaced upper front teeth, he looked more like a jockey than an astronaut, but he was a seasoned navy carrier and test pilot, and a proven veteran of the Gemini program. He was Gordon Cooper’s copilot on Gemini 5, an eight-day endurance test in Earth orbit, and he commanded Gemini 11, which made the first one-orbit rendezvous with an Agena target vehicle (to which copilot Dick Gordon made a risky spacewalk to attach an experimental tether). Beneath his easygoing attitude and wisecracking lay competence, experience, and sound judgment.

  I met Conrad early in the LM program, at our first mockup review, and worked with him for the next several months as he helped us develop the LM flight stations and lunar surface access provisions. He was fun to work with—his antics as he swung suspended in our awkward Peter Pan rig were slapstick comedy at its best. But he also convinced us that a platform and ladder were needed on the LM’s forward landing gear strut, instead of the block-and-tackle arrangement we had proposed. He was helpful in improving the flight station arrangements and the controls and displays, and in gaining acceptance of the other astronauts for the evolving design. Among other LM design details Conrad helped develop were the rectangular forward hatch, the overhead docking window and electroluminescent lighting for the displays and instruments. He was so enthusiastic about the virtues of electroluminescent lighting that he sold it to Joe Shea and Bob Gilruth for the command module as well.

  After our M-5 mockup review Conrad went off on the Gemini program and I did not see much of him until he a
nd Alan Bean began coming to Bethpage for some of the LM-3 tests, in their role as backup crew for Apollo 9. He greeted me and my colleagues like long-lost buddies, and we picked up our friendship immediately, despite almost three years’ absence. Pete Conrad and Al Bean were not only dedicated and diligent in performing tests whenever our around-the-clock schedule required but also good-humored about it.

  When Conrad, Al Bean, and Dick Gordon were assigned as prime crew for Apollo 12, Conrad and Bean were often in Bethpage testing LM-6, to which they gave the mission call-name Intrepid. Bean, LM pilot, was serious and studious and delved deeply into detail until he thoroughly understood how all the LM systems worked and what could go wrong with them. He would spend all night following up on one of Conrad’s offhand comments during a test until he had a complete explanation that Pete would buy. I thought they made a great team, and I sought their suggestions on how we could improve LM design and procedures. After LM-6 was delivered to KSC, I did not see them again until the flight readiness review, where they said they were satisfied that Intrepid was in good shape and ready to fly. They, who would be risking their lives in my spacecraft, urged me, who would be watching safely from the ground, not to worry; everything with LM would be just fine. They surely were not lacking in confidence!

  Thus it really got my attention when Pete Conrad coolly called out to Houston a few minutes after the Saturn 5 lifted Apollo 12 into low clouds at KSC, “Okay, we just lost the platform, gang. I don’t know what happened here; we had everything in the world drop out.”

  A look at the SPAN video monitors confirmed what the crew and the flight controllers were seeing: command module Yankee Clipper showed a master alarm, its platform was tumbling, and all instrumentation readouts showed gibberish. The crew saw all lights lit on the caution and warning panel, something that had never been served up in the most imaginative ground simulation. Al Bean was puzzled, because although the readouts indicated the entire electrical system was out, current meters on the panel showed the spacecraft was still drawing power, but at a lower than normal rate. Conrad calmly read the long list of warning lights to Houston and waited for advice. Meanwhile, the Saturn continued its ascent unperturbed, under the control of its inertial measurement unit, which was independent of the CM’s guidance platform.

  Flight Controller John Aaron looked at the meaningless pattern of numbers coming from the CM’s instrumentation and remembered seeing it before, when he was watching a KSC launch preparation test a year earlier. He advised Flight Director Gerry Griffin to ask the crew to switch the signal conditioning equipment to the auxiliary position. Neither CapCom Jerry Carr nor Pete Conrad recognized the obscure command, but Al Bean found the proper switch and moved it, and instrumentation readouts were instantly restored. With live data to study, the crew and ground controllers saw no residual damage, except that the fuel cells had disconnected from the electrical buses, leaving the spacecraft without its primary power source,1 and the guidance platform had tumbled. Immediately following first-stage separation and S-2 stage ignition, Bean recycled the electrical bus circuit breakers and the fuel cells came back on line. The platform could be realigned when they were safely in orbit, which is where they were headed.

  “I’m not sure we didn’t get hit by lightning,” Conrad told Houston. He was right; later analysis of data and automatic cameras at the launch pad showed that two lightning bolts had struck Apollo 12, at thirty-six and fifty-two seconds after liftoff. The electrical surge from the first strike caused the CM systems to shut down, and the second knocked out the guidance platform. The long column of ionized gases from the Saturn rocket exhaust had acted like a giant lightning rod, providing an attractive path to ground from the dark clouds overhead.2

  When Apollo 12 was in Earth orbit, NASA and North American had an hour and a half to determine whether it was safe to fly to the Moon. As Dick Gordon was taking star sightings to realign the platform, Mission Control determined that all CM system data looked good except for a few instrumentation sensors, which had apparently been burned out. How could they quickly determine whether Yankee Clipper’s systems were all right? Again flight controller John Aaron made a key contribution, proposing that they perform the lunar orbit injection (LOI) checklist, the most demanding flight checkout the CM would have to pass, and if it passed that it was okay to fly. Flight Operations Director Chris Kraft told them to proceed with the checklist, but reserved judgment on whether this would clear Apollo 12 for flight until he consulted with other senior NASA managers. Gilruth, Low, McDivitt,3 and Petrone approved; their one reservation, that the lightning might have knocked out the pyrotechnic systems on the recovery parachutes, was rendered moot because going to the Moon would not change the crew’s final predicament if that were the case. The flight crew and ground controllers successfully performed the LOI checklist, and Apollo 12 was cleared to go to the Moon.4

  Through all this turmoil the LM Intrepid was snugly nestled inside the protective conical structure of the spacecraft/LM adapter, where it was when the lightning had struck. Inactive and inert, I did not think the LM had sustained any damage, since the major lightning current would travel through the outer skin of the SLA. However, within sensitive electronic microcircuits there was always the possibility of inducing damaging secondary currents in the tiny etched conductors and components, whenever a strong current surge and changing magnetic field was nearby. While LM was inaccessible, there was not much we could do except worry. I asked our section heads to review all electrical and electronic components with their suppliers, to identify those most susceptible to lightning-induced damage. If we could verify the integrity of some of the most susceptible items, we would gain confidence in the LM’s overall status.

  Half way to the Moon, the crew entered the LM and performed housekeeping and communications checks. Everything seemed all right, but little had been tested. Not until they were in lunar orbit, only six and a half hours before planned touchdown, did Conrad and Bean enter the LM fully suited, activate all systems, and put Intrepid through the extensive powered descent initiation (PDI) checklist. With all eyes in Houston and Bethpage on the monitors, no discrepancies were seen. Our spindly, fragile-looking Intrepid had survived the great balls of fire. I felt greatly relieved, even though I had expected this outcome and confidently predicted it to my associates.

  Apollo 11 had landed four miles from its targeted landing point, and for the first few hours Houston and the astronauts were trying to determine exactly where on the Moon they were. Exasperated, Gen. Sam Phillips, Apollo program director, demanded a pinpoint landing for the next mission. To make the requirement clearly visible, NASA decided that the next mission, to the Ocean of Storms, would include a walk to the unmanned Surveyor 3 spacecraft; that had landed there in April 1967. To achieve pinpoint landing capability would require inventing new guidance techniques beyond those available for Apollo 11. Highly accurate landings were essential to efficient lunar exploration because they allowed scientists and geologists to plan and discuss with the astronauts, in detail and in advance, the exact route, objectives, and techniques to be used during each excursion onto the lunar surface. Without knowing their exact surface position, much valuable time on the Moon would be wasted in ad hoc revision of the geological exploration traverses and in orienting the explorers to alternate landmarks.

  A young NASA mathematician named Emil Schiesser made the crucial breakthrough. He devised an elegantly simple scheme that used the Doppler shift pattern of radio frequency communications from the LM.5 By comparing the predicted Doppler pattern with the actual observations, ground control’s computers could calculate the deviation in the LM’s real trajectory from the targeted preprogrammed flight path. NASA flight controllers had already been using this technique to analyze translunar flight trajectories. In meetings of Bill Tindall’s mission planning analysis group, a brilliant technique was devised to get the flight path correction information into the LM’s computer. The computer would be told the target landing point had
moved by the amount necessary to cancel out the deviation between the real and the predicted trajectories. This required the pilot to enter only a single number into the LM’s data entry keyboard.

  LM-powered descent on Apollo 12 went beautifully. The computer overload problem that had produced heart-stopping program alarms for Armstrong and Aldrin had been corrected simply by changing software instructions to no longer require the computer to keep updating and storing rendezvous radar data with the CSM’s position when the landing radar was operating during powered descent. When Intrepid pitched forward for the final descent at seven thousand feet, Conrad anxiously scanned the lunar landscape below, then gave an exultant war whoop: “Hey, there it is. There it is! Son of a gun, right down the middle of the road!”

  He recognized the Snowman crater, on whose rim Surveyor 3 rested, far ahead in a sea of other craters. At an altitude of four hundred feet he took control manually and skillfully landed Intrepid close to Snowman’s rim, about six hundred feet from Surveyor 3. He performed the final one hundred feet of descent primarily on instruments, since his view of the surface was largely obscured by dust kicked up by the descent engine’s exhaust.6 When the blue lunar surface contact light went on, Conrad shut the engine down and Intrepid thumped firmly onto the ground.7 They had achieved a perfect pinpoint landing. There was no postlanding excitement as on Apollo 11, since a simple procedural change had solved the fuel-line pressure buildup problem. (We delayed venting the descent propellant tanks after landing, giving the descent engine time to cool off.)

  Conrad and Bean were on the Moon for thirty-two hours and performed two moonwalks totaling seven and three-quarter hours. They made the first deployment of the Apollo lunar surface experiments package (ALSEP), an expanded array of scientific instruments that included a seismometer, a magnetometer, an atmospheric particle sensor and a central transmitting station to relay ALSEP’s data to Earth. ALSEP was designed to gather and transmit data for five years, and the instruments were so sensitive that the seismometer detected the astronauts’ footsteps as soon as it was turned on. We had modified LM-6’s scientific equipment bay to accommodate ALSEP and made special external mounting provisions for the radioactive thermoelectric generator (RTG). It used a radioisotope that would provide power to the ALSEP even during lunar night. Because of safety concerns in event of a launch failure, the power source was encased in ablative insulation capable of reentering the Earth’s atmosphere.