ROCKET PROPULSION - THE APOLLO MISSION Don Harvey My smartest career move was leaving North American Aviation to join the Space Technology Laboratories (STL), which later became TRW. STL was gearing up to challenge one of the major US Rocket Engine producers in a competition for the Apollo Lunar Module Descent Engine (LMDE). I wanted a part of that action. There was much excitement about space travel, and I was determined not to be left out. My first assignment was the design and development of the thrust control system for the Lunar Module Descent Engine (LMDE) for the Apollo Project. This included the bi-propellant flow control valves, the throttle actuator and the mixture ratio control system. The beauty of this assignment was I had to match my thrust control system with the rest of the engine. In other words, I had to understand the injector and thrust chamber characteristics to properly configure the valves. That ultimately lead to my inheriting the entire engine several months before launch. Mission support at Houston was my ultimate goal. A handful of STL engineers was assembled to propose a design for the LMDE. None of us had any fancy titles, just “Members of the Technical Staff”, commonly referred to as MTS’s. Our competition was Rocketdyne, then the leading US company for Rocket Engine design and development. It was a “David & Goliath situation”. However, none of us had any doubts that we could beat them. I believe that our extreme confidence and hard work played a big part in winning the contract. Getting started was the most difficult phase of this project. It required an immense amount of teamwork between the chemical kineticists (rocket chemists) and the hardware designers. The liquid propellants and their mixture ratio were specified. My problem was to size the valves and configure the control surfaces such that the proper flow rates and mixture ratio could be maintained within the supply pressure and throttling ranges specified. I had to work with the injector designer and the thrust chamber designer to match my valves to their flow parameters. Since their parameters kept changing, I had to revise my design numerous times to compensate for their changes. It seemed that we would never settle on a design. Eventually we did and it proved very efficient. Our early test configurations were designed at an engine thrust level of 5,000 pounds, about one half the LMDE maximum thrust. Our LMDE was a throttling engine with a thrust range of 1,000 to 10,000 pounds compared to the Saturn Launch Vehicle that had a thrust of 7,500,000 pounds at lift-off. It’s like comparing a pea shooter to a large cannon. The booster was the workhorse. The LMDE delivered the payload. Early tests were conducted at our Rocket Test Facility in Inglewood, CA, where commercial, industrial and residential properties surrounded the facility. Our rocket firings were noisy and stinky, but no one seemed to complain. One morning at about eight o’clock we had a major leak from a 20,000 gallon tank loaded with oxidizer propellant. The oxidizer was a very toxic, volatile, reactive propellant that emitted a large reddish-brown cloud, commonly referred to as a “big brown fart”. Our technicians donned protective clothing and approached the tank with a liquid nitrogen supply to freeze the propellant in the leaking component. After doing this successfully, the tank was emptied into another tank. This event expedited our move to a new test facility a few miles inland of San Clemente, CA. The rocket test site construction started in November, 1963 and was completed five months later in March, 1964. We then moved what equipment we could use to the new site called the Capistrano Test Site (CTS) and abandoned the Inglewood site. I’m sure the Inglewood residents were happy to see us go. The CTS facility is located on 2,780 acres of cattle grazing land with beautiful ridges and canyons. The canyons are lined with oak and sycamore trees over 100 years old. In the springtime numerous wildflowers appear, my favorite being owls clover. One time while walking from the office to the test area I counted over twenty different wildflowers. And there are other features that enhance the test site - namely the birds and wild animals. While running the canyons and ridges during noon hour I encountered reptiles, bobcats, cougars, opossums, coyotes, rabbits, and deer. Also many species of birds were present including red shouldered hawks, red tail hawks, kestrels, kites, cactus wrens, vultures, towhees, doves, quail and the elusive California gnatcatcher. It was a pleasure to work there. After several design iterations we built our first 10,000-pound thrust engine and delivered it to CTS. Ed, accompanied me to CTS where we had the responsibility as development engineers to supervise the installation and test the engine. Ed wrote the test procedures and I adjusted the valves and mixture ratio control. He had the paper. I had the hardware. On our first visit, I picked up Ed at his house and he asked me if it was OK if he brought his Doberman Pinscher with him. I told him it was fine with me, so he did. On the way into the site, while on a Rancho Mission Viejo road, I passed a huge snake on the side of the road. I said to Ed, “Did you see that?”. “See what?”, he asked “That snake by the side of the road”. “No, let’s go back and look at it”. So I stopped and backed up to the spot. Before I could say anything Ed hopped out of the car and walked up to the snake. It was basking in the sun and didn’t move, so Ed edged it with his foot. The snake reeled back and hissed like angry snakes are prone to do. Ed turned white as frightened men are prone to do. I thought he was going to pass out. It was a large gopher snake furious that it was disturbed. We then continued on to the test site and the snake remained unharmed. I think both Ed and the snake learned something that day. After checking in with Security, I parked the car and went into the office leaving the dog in my car with the windows partially down. When I came out to the car to get my briefcase the dog wouldn’t let me in. The dog was trying to push his head with several four inch teeth through the window opening. I had to get Ed to get his dog under control. We then proceeded to the test stand to check the engine installation and adjust the valves and linkage for the proper flow rates and mixture ratio. This initial adjustment was an educated guess to obtain test data for the next run. The engine combustion stability was surprisingly smooth giving us confidence we could trim the engine for better performance. While the test data were being processed, Ed and I collared his dog and we walked the boundary of the 2,780-acre site. On return Ed released the dog. It got too close to the cooling water reservoir and slid in. The sides were sloped and slippery so we had a tough time pulling him out. We then looked at the processed test data, and I reset the engine valves for better performance. The next test was performed at night, and the mixture ratio and flows were on target. I stood outside the blockhouse about 1,000 feet from the test stand and watched as the engine ignited and shot its flame vertically downward into the water-cooled stand. It was a rocketeer’s moment. The test results were beyond expectations. We knew we were on our way. It was near midnight when we concluded the data reduction from the second test, so we decided to check in at the motel in San Juan Capistrano. There was a big sign “NO DOGS” posted at the reception desk. Ed looked at me and winked. He sneaked his dog into his room and all was fine until about six the next morning when some farm workers decided to pick some oranges from the trees on the motel grounds. Ed thought his dog was going to tear the door down. We had to find a different motel the next night. Ed and I teamed up on numerous engine tests including tests at Arnold Engineering Development Center in Tennessee. If tests ran over two shifts we could spell each other. This routine worked out very well. One morning I drove from home in Westchester near LAX to continue engine testing. This time we were going to throttle the engine through its full range, which was a real test of the design of the valves and the mixture ratio linkage. The engine ran smoothly but did not stay on its nominal mixture ratio, requiring adjustment of the linkage. It took several tries to get an acceptable mixture ratio result. Soon it was sunrise and I was on my second wind. I was feeling good so I grabbed the test data and hopped into my car to drive to the office in Redondo Beach. I was proud of our success and wanted to show the team the test data. As I got a few miles north of San Juan Capistrano I started to feel spongy. The long day had caught up with me, so I turned off at the next off ramp and headed for the nearest motel. There were many more times that we tested through the night to optimize the engine performance. After the previous experience of driving while spongy I always made sure I got some heavy duty sleep. As time progressed I was promoted to Section Head, the first line of Engineering Management. I had twenty engineers, two secretaries and a computress. All LMDE component and system engineers were assigned to my section. I now had complete engine responsibility, which was my goal. My Department and Laboratory Managers were superb - Joe and Pete. The Program Manager, Arnie, was the best PM in the Division. Everything was going my way. They trusted me and I respected them. Joe and Pete were both brilliant men. Both were younger than I. During the final assembly and acceptance testing phases, work became very intense. My Department Manager decided that my section, which was spread all over the building, should be consolidated in one area. So one weekend our office furniture was moved into two large office bays. Two senior engineers in my Propulsion Section, who incidentally had larger salaries than I, had a problem. Both had major responsibilities, Frank in charge of the thrust chamber and Harvey W. in charge of the main shutoff valves. Both were prima donnas, and unfortunately, neither knew the other very well. Their furniture was moved into a large two-man office on a Saturday morning. Harvey W. came in and set up his furniture the way he wanted it. Unbeknownst of Harvey W’s visit, Frank came in later and arranged the furniture the way he wanted it. When Harvey W. showed up at the office he was incensed at Frank. A few nasty words were uttered which led to distrust of each other. They were like two male dogs - each thinking the other was a fire hydrant. Days went by and finally Frank told me of their situation. I was very busy and didn’t have a lot of time to dig into it, so I called Harvey W. into my office along with Frank. I told Harvey W. what Frank had told me and me said, “That’s pretty accurate”. I then told them, “Go down to the Bay Nineties Bar and have a beer. Then come back and tell me how you solved the problem”. They were gone most of the afternoon and came back the best of friends. When I sent them out I had no idea how it was going to turn out. I later learned that Harvey W. passed away January 10th, 2003. I lost track of Frank. A much more difficult personnel problem developed between the two secretaries and the computress. They were at each other like politicians debating. Neither listened to the other. One by one they filed into my office crying. I had no idea how to handle their problem because I never understood it. Nowhere in any of my engineering books or training was there a hint of an approach to a solution. I just let them cry it out and hoped they settled down. The next day all was cool. Often personnel problems were much more difficult to understand than the technical ones. The contract with NASA required that we test our engine in a high altitude chamber at Arnold Engineering Development Center (AEDC) in Tullahoma, Tennessee. Ed and I had our engine shipped there in the summer of 1965 for a series of high altitude tests. It was a challenging job for us because of the work ethic of the AEDC test crew and their management. The rules of the game were we were billed several thousand dollars a day while we occupied their test chamber, whether we tested or not. If their test system failed and we were shut down, we were still billed. They were marvelous at dragging their feet. A problem developed during the first attempt to test our engine. Unfortunately it set the tone of our working relationship with the test personnel. During the ten second countdown their control system failed. Numerous attempts yielded the same result. It was evident that their controls engineer could not solve the problem. No one at AEDC was motivated to solve the problem. Ed and I discussed the issue and decided that we needed to take over. We called our division’s Instrumentation and Control (I&C) Manager and suggested that he or his best engineer come immediately to help us out. Parnell, the I&C manager, decided to come. It was a difficult decision for him because the Watts Riots had just begun, and his home was on the edge of the riot zone. By the time he arrived we had the schematics laid out and had acquainted ourselves with the system. Parnell was an excellent troubleshooter and put his finger on the problem in a few hours. What disturbed the Southern test crew was that the person who bailed them out was Afro American. They didn’t appreciate taking instructions from him. On one occasion after a botched test we discovered that their propellant tanks were grossly contaminated with rust and metallic particles. They claimed it would take four months to empty, clean and refill their tanks. I told them, “Lets discuss this with the Director of Engineering.” They brought the Director in and as expected, he backed up his test personnel. He had no motive to do otherwise. I told the Engineering Director, “Look, we built our entire test facility, the roads, blockhouse, test stand, offices, propellant feed systems and instrumentation and control systems in five months. Surely you can do better than four months to clean your system.” I also said, “This test is on the critical path and if your system delays the test, the launch is delayed. Do you want to explain that to the NASA Director?” They were embarrassed, and had us back in operation in ten days. During one test the crew allowed a shock wave to collapse the fragile columbium nozzle extension. To cover it up they sent in a mechanic to straighten it out using tools similar to what one would use in straightening out a dented fender. The extension was only a few mils thick and covered with a protective coating. It looked like someone had pelted it with sharp angled rocks. We had to replace it with another unit. It was a very expensive mistake. Despite these problems, we completed several significant tests in record time. We had many interesting experiences in Tennessee. However, when the time came we were ready to head home. A standing joke with Ed and me was “If the waitresses start looking good or we start eating grits, it is time to go home”. Back at CTS we were gearing up for more development and off nominal testing in our high altitude facility. The engine design had been frozen and a series of characterization tests was planned. For the most part testing went as planned, however, I remember one test where a stand propellant valve stayed open and the engine was operated in a mode for which it was not designed. Because of our conservative design the engine survived with no damage and surprisingly the combustion stability was nominal. This turned out to be a very important test condition. It was later studied when we were called to use our engine to rescue Apollo 13. This test closely duplicated the thrust profile required to return the astronauts back to earth. More about that later. I spent many night hours witnessing engine tests and marveled at the noise and flame generated in the atmospheric tests. Beautiful shock diamond patterns were formed that only rocket scientists and engineers really appreciated. One weekend I brought my entire family down to the Vertical Engine Test Stand where the Descent Engine was tested just to see where I worked. Someday I hope this test site will be considered a National Monument. Decades ago a monument was erected adjacent to the test site on the Mission Viejo Ranch, recognizing the important Rocket Engine development conducted there. It is in the wrong place. Back in Redondo Beach we began conducting Qualification Tests and later Acceptance Tests for the flight Engines. When all the deliverable flight Engines were placed in the final assembly area I brought my family, Joyce, David, Anne, Jon and Steven to the plant. We entered the final assembly area, and I had each of them touch each engine so that someday they could say, “I have had my hands on something that is now resting on the moon.” After all engine acceptance tests were completed, I was directed to reduce my staff by one third. I had to lay off seven engineers, and the outside employment environment was not very encouraging. Many engineers and scientists working on other phases of the project in and outside of TRW were also laid off. One of the engineers in my section was angry and was very difficult to deal with. I lost a lot of sleep during that period. Eventually I was able to get all but one hired outside TRW. The only astronauts I met personally were Jim McDivitt and Charlie Duke. Jim McDivitt was Apollo 9 Commander and later Apollo Program Spacecraft Director. Charlie Duke was at Mission Control supporting Commander Neil Armstrong during the Apollo 11 mission. Later Duke was the Apollo 16 Lunar Module Pilot. I met Jim McDivitt in a meeting that he chaired at the Manned Spacecraft Center in Houston. Another Rocket Engine supplier was having combustion problems and was running out of ideas. Several propulsion engineers and scientists were invited from across the country to participate in the discussions. The topic was Rocket Engine combustion instability. Here we were, all competitors in the Rocket Engine business, pitching in to help another engine competitor solve it’s problem. We were all motivated to help resolve the problem because failure of one unit could result in failure of the mission. No one wanted that to happen. I was impressed with McDivitt’s detailed knowledge about the combustion stability tests we had conducted at our test site. Each of us summarized the test program and results pertinent to the problem at hand. There were many questions and clarifications and then the meeting was adjourned. Months later I learned that the problem had been resolved and credit given to the information learned at this meeting. My meeting with Charlie Duke occurred during the Apollo 11 Mission. I met him during a change of shift briefing. Whenever possible, I went to these briefings to get the latest information and pick up lunar photographs, maps and transcripts of voice communications with the astronauts. When I was introduced to him he asked what my interest was and I told him, “I am the TRW engineering representative for the Lunar Module Descent Engine.” He replied, “I’m happy to have you with us. We may need you.” I liked Charlie because he was interested in the people who have contributed to the Apollo Project, and he made an effort to meet them. Apollo 5 was launched on January 22nd, 1968 to test the Lunar Module in earth orbit. This test was important because it would be the first test in space. The LMDE engine was started at ten percent thrust, and before the chamber pressure could reach its nominal value the engine was shut down by an abort command. The abort was triggered by insufficient change in velocity of the spacecraft. The mission planners had miscalculated and had not taken into account the fact that propellant feed pressures to the engine were intentionally set at about half the nominal value. This resulted in lower propellant flow rates to the engine, hence lower thrust. It was clear to NASA that if TRW propulsion engineers had been aware of these conditions, the problem would likely have been detected in advance, and measures taken to prevent the inadvertent shutdown. I followed the mission progress from my office in Redondo Beach, and was angry that this important test was cut short because of poor planning. I’m sure NASA was angry as well because from then on we were directed to provide support at the Grumman Co. and Houston on all future missions. I supported the Apollo 9 and 10 Missions at Grumman in Bethpage, NY and Apollo 11 through 17 at the Manned Spacecraft Center in Houston, TX. Below are photos of typical access badges for mission support. GRUMMAN BADGE APOLLO 13 BADGE The first mission support task I was assigned to was the Apollo 9 earth orbital mission. It was the only major piece of Apollo hardware not tested in space, therefore it was a significant milestone. I was directed to report to the Mission Evaluation Room at Grumman in Bethpage, NY where several months earlier our engine was installed in the Lunar Module Descent Stage. My boss reported to the Manned Spacecraft Center in Houston where we kept in constant communications. If any anomaly occurred, we would be able to react swiftly. While at Mission Support I was asked and performed “what if” calculations to determine the effects of off balance propellant feed pressures on engine performance. At that time in my career I was still using a slide rule for on the spot calculations, as there were no hand calculators available. Apollo 9 was launched on March 3rd, 1969, to perform earth orbital tests of the Command Module and the Lunar Module. The astronauts named the Lunar Module “Spider” and the Command Module “Gumdrop”. The Descent Engine on Spider was fired for six minutes at full thrust while in the docked configuration, simulating a major part of the powered descent burn that would be required to land the Descent Stage on the moon. The crew manually controlled the engine thrust by actuating my bipropellant valves. Performance was on target. On this mission, several orbits later, James McDivitt and Russell Schweickart entered the Lunar Module and were given an OK for separation from the Command Module. After separating and maneuvering Spider about three miles from Gumdrop, McDivitt restarted the Descent Engine. He ramped from ten percent to twenty percent thrust and then stepped to forty percent thrust. I was proud of the engine performance and the reliability of my valves. The astronauts then ejected the Descent Stage and fired the Rocketdyne Ascent Engine to rendezvous with David Scott in Gumdrop. This test series was highly successful and gave the team confidence that they could proceed to the Apollo 10 lunar test series. Apollo 10 promised to be more exciting. On May 15th, 1969, I reported to the Grumman plant in Bethpage, NY. Our engine would be fired in this test series to execute the first lunar orbit and low pass maneuver over the lunar surface. The Lunar Module was named “Snoopy” and the Command Module “Charlie Brown”. Apollo 10 was launched May 18th, 1969 and was put into lunar orbit a few days later. After orbiting the moon, the two spaceships separated to begin the lunar maneuvers. John Young was in Charlie Brown and Gene Cernan and Tom Stafford in Snoopy. In my opinion this was the riskiest manned space flight tests for the Apollo astronauts because it involved firing sequentially the Descent and Ascent Rocket Engines. A simulated moon landing had never been performed and neither had a simulated ascent from the moon to command module. There was a lot of tension in the Propulsion room during those operations. My primary interest was the operation of the bipropellant cavitating venturi valves which controlled the thrust of the Descent Engine. I had spent an enormous amount of time designing and developing the valves to ensure reliability and performance requirements were met or exceeded. Any valve anomaly could upset the mixture ratio and cause rough combustion and off nominal thrust. I was greatly relieved when the data revealed that engine performance was nominal and that the valves performed perfectly. I felt that now we were ready for the first manned lunar landing. Apollo 11 was next in line for that event. I have often heard the expression, “Being at the right place at the right time.” This time it clearly applied to me. I was directed to report to the Johnson Spacecraft Center in Houston, TX on July 18th, 1969 for the first attempt to soft land a manned spacecraft on the surface of the moon. Neil Armstrong was the Apollo 11 Commander, Michael Collins the Command Module Pilot and Buzz Aldrin Jr. the Lunar Module Pilot. The Command Module was named “Columbia” and the Descent Stage named “Eagle”. The three astronauts were all born in 1930, weighed165 pounds and were within an inch of the same height, five feet, eleven inches. For comparison, I am one year younger, weigh 165 pounds and am one inch shorter. Apollo 11 was the fifth Apollo manned flight, and was built on the knowledge and successes of the four previous missions. The objective of each previous flight was to advance as far as possible the testing of the complex Apollo systems. The fewer unknowns from the previous flights improved the chances of success for the next flight. Apollo 11 was the climax. The major untested events were the powered descent and landing and the powered ascent and rendezvous with Columbia. Everything had to work. Apollo 11 was launched on July 16th with the lunar orbit insertion and the powered descent scheduled for July 20th. This was what I had worked and waited for. The years I spent in design, development, testing and re-testing had paid off. I packed my technical support documents, slide rule, pencils and erasers and flew to Houston. I reported to the Mission Evaluation Room and was assigned a spot with a computer monitor and earphones for listening to the Astronauts and the capsule communicators (CAPCOM). Around the room were several Grumman and NASA propulsion engineers monitoring the propellant feed and pressurization systems. All in all there were about twenty of us including support personnel for reducing and plotting data. The computer monitor displayed a schematic of the propulsion system showing thrust, temperatures, pressures, propellant flow rates, mixture ratio and propellant remaining. Also the Descent Stage forward velocity, descent rate and attitude were displayed. Everything I needed to know to evaluate our Descent Rocket Engine performance was at my fingertips. After I arrived at the Mission Evaluation Room, the spacecraft was being prepared for lunar orbit insertion. All systems were “go”. Then Eagle was separated from Columbia in preparation for the lunar landing. My eyes were focused on the computer monitor screen and my ears tuned to the voice communications. The Mission Evaluation Room Manager commanded silence as we prepared for the critical descent to the moon. I sat excited as the powered descent was initiated. On command the descent Engine was fired for about 26 seconds at ten percent thrust and then ramped up to full thrust to execute the braking phase. At about 400 seconds into the burn, the thrust was reduced to about 55%, an important thrust level where below this level, my cavitating venturi valves operate in the cavitating mode. From then on, no matter how much the downstream pressure changed due to injector position or throat erosion, the valves were unaffected. That important feature of our engine design was greatly appreciated by the astronauts because it guaranteed precise propellant flow rates and mixture ratios when the engine was throttled. That translated in smooth combustion stability, maximum specific impulse and efficient propellant consumption. Near the landing site Armstrong took over the controls and manually controlled the Descent Engine thrust until the Eagle had landed. During the final lunar landing phase we could hear Aldrin reading to Armstrong the rate of descent and altitude. I remember hearing someone in CAPCOM saying that Neil Armstrong’s pulse rate had soared to over 150 beats per minute. That direct medical channel was not available to me, but since my heart beat rate increased also, that seemed reasonable to me. When we heard “Contact Light. Okay, engine stop” everyone in the room cheered. We pulled it off. What an accomplishment! The amount of useable rocket propellant remaining after landing was 698 pounds, equivalent to 43 seconds of firing time remaining. The flight propellant mixture ratio error was less than one eighth of one percent, very close to perfection. These data speak well for the design and calibration of the cavitating venturi valves, which were important factors in the Rocket Engine performance. On June 15th, 1970, I presented a technical paper to the American Institute of Aeronautics and Astronautics at the annual meeting in San Diego, CA. The title of the paper (No. 70-703) is “Throttling Venturi Valves For Liquid Rocket Engines”. I proudly described in detail the design and development of cavitating venturi valves to a group of 100 aerospace engineers. On July 20th, 1999, thirty years after the first manned moon landing, a reporter for CSPAN TV interviewed a panel of Apollo Astronauts and asked them what each thought was the most important development achieved during the Apollo Project? Neil Armstrong’s reply was the development of the cavitating venturi valves. I knew why he said that. When he was making the final critical landing maneuver he was moving the pintles in my cavitating venturi valves ever so slightly to control the descent velocity. The precision built into the valves ensured that the fuel and oxidizer propellants would be expended at the proper rate, not allowing one propellant to deplete before the other. Armstrong knew that. I never had a chance to meet him. Unless he read my AIAA Paper, I doubt that he knows who designed the valves. After all work on the moon was completed, Neil and Buzz prepared Eagle for departure from the moon. The Ascent Engine was fired and Eagle departed, leaving the Descent Stage on the surface. Neil and Buzz docked Eagle with Columbia and joined Michael Collins in Columbia. Eagle was then separated and put into an orbit that eventually led to a planned lunar collision. The remaining journey and landing were successful as the three astronauts were safely returned to earth. My turn finally came to observe an Apollo launch at Cape Canaveral. On November 13th, 1969 I flew to Orlando, FL to witness the launch of Apollo 12. The following morning I drove to the Cape and proceeded to the viewing stand a few miles from the launch pad. In the distance I could see Apollo 12 attached to the launch tower waiting for the countdown. Even though rain was threatening, the stands were full and the crowd excited about the impending launch. When the countdown started the crowd silenced. Then I felt the roar of the three enormous Saturn booster engines as the earth rumbled beneath, reminiscent of standing next to a fast moving freight train. As Apollo 12 lifted off the pad and headed skyward, I saw a brilliant lightning bolt emerge from the sky and flow down the sides of the spacecraft through the exhaust plume to the earth below. My immediate thought was catastrophic damage to the spacecraft. The ensuing thunderclap was nearly masked by the loud roar from the booster rockets. Apollo 12 challenged Mother Nature and continued it’s space flight as if to say, “You can’t stop me”. Inside the Command Module Pete Conrad, Alan Bean and Dick Gordon saw bright flashes and then sudden darkness as the main circuit breakers tripped. Backup systems took over, breakers were reset and the flight continued as if nothing happened. I couldn’t imagine being in their place during that frightening event. It was a miracle that there was no damage to the spacecraft. After the viewing crowd dispersed I drove to the Orlando Airport and flew to Houston to support the lunar landing. I arrived a day before the lunar descent and checked in at the Mission Evaluation room. The familiar computer monitor was patiently waiting for me. The NASA and Grumman propulsion engineers met with me, and we discussed any concerns we had. Soon Conrad and Bean transferred from Yankee Clipper to Intrepid to initiate the lunar descent. They executed the powered descent which they later described as a flight of “incredible accuracy and control”. I followed the flight parameters on my monitor as the Descent Engine softly landed Intrepid on the moon’s surface. Again, I felt proud of its reliability and performance. Post landing, my calculations revealed an average propellant consumption mixture ratio error of less than one-half of one percent, well within the design range. The “incredible accuracy and control” can be attributed to the precision of the cavitating venturi valves that controlled the propellant flow rates to the injector. The remaining propellant was 1,036 pounds (5.7%) equivalent to a little over one-minute flight time. We chalked up another huge success. Apollo 13 was on its way to the moon on April 13th, 1970 when an explosion occurred that seriously damaged the Service Module. I was attending an evening class at USC at that time, and was notified by an officer from the Campus Security that I had an important phone call. It was a call from Joyce. She told me that Joe, my boss, had called and wanted me to report to the Manned Spacecraft Center in Houston, Texas as soon as possible. I phoned Joe and he briefed me on the state of the spacecraft. It did not sound good. I then phoned my contact at NASA and learned that the damage to the Service Module was so severe that it was believed that the lives of the astronauts were in jeopardy. The entire aerospace community was stirred by this life threatening emergency. I had never seen so much effort focused in one direction - the safe return of Jim Lovell. Frank Borman and Fred Haise was on the top of everyone’s minds. I never met these astronauts, however, I considered them as brothers, and everything in my power was brought to bear to bring them home safely. I’m sure all those on the Apollo Program felt that way. Engineers and flight equipment were overtaxed, but that was trivial compared to what the three astronauts went through. It was our responsibility to get them back safely, and that’s what we were going to do. We all had a personal stake in their rescue because it was our equipment that they trusted. The TRW Lunar Module Descent Engine (LMDE) was the only propulsion system available for returning the astronauts safely to earth. It was not designed to push the connected Service, Command and Lunar Modules through space in the configuration shown. The TRW rocket expansion nozzle is barely noticeable poking out the very right end of the Descent Stage. That task had never been defined, least of all evaluated. The rocket was large enough and there was sufficient propellant to provide the total impulse required bringing them back safely. The issue that concerned me was restarting the engine after a long burn. The risk was excessive charring from the long burn that could weaken the ablative thrust chamber liner. Failure of the liner could result in a catastrophic burn through of the thrust chamber leading to loss of lives. I had many parameters to consider in evaluating the viability of the various rescue scenarios. However, I did have help. At the main office I had specialists on call

APOLLO 13 RESCUE CONFIGURATION for special analyses. But in the back of my mind was the fact that the burden was on me. Decisions I made had an enormous effect on the lives of the astronauts and the US space program. A wrong decision or an error in analysis could lead to disaster. I thought about my responsibility as I prepared to fly out the next morning. Before leaving I met with Mike, the TRW thermal analysis specialist, and arranged to have him on call to perform parametric analyses. His thermal model could accurately predict ablative liner char depth resulting from any rocket firing profile I gave him. I relied on Mike for rapid response and precise calculations. I’m sure he felt the same pressure as I did. I made sure he did. At that time computer analyses were performed with an IBM computer which occupied the greater portion of a very large office building. Cards had to be punched and then fed into the card reader of the computer to enter data. Occasionally the card readers ate the cards for no reason at all. We prayed that it would not happen to us. Because of the emergency Mike was able to have a priority for immediate access to the computer. Today a personal computer could perform those same analyses in seconds. When I arrived at the Mission Evaluation Building I was informed that the building was in lock down. No one was to leave until the crisis was over. I thought to myself, “Who would even consider leaving when the astronauts were stranded in space?” When I talked with my colleagues from NASA and Grumman, their attitude was clear. We were going to bring them back to earth safely. There was absolutely no doubt about that. By the time I arrived in Houston, a 32 second firing of our rocket had occurred to place the spaceship in a free return trajectory. This was performed about five and one half hours after the Service Module explosion. My primary concern with our Rocket Engine was the integrity of the ablative chamber liner. The big question was, “What future rocket firings would be required to bring the astronauts back safely?” A 32 second burn of our rocket was of no consequence to the integrity of the ablative chamber because there would be no appreciable charring of the chamber liner. All delivered engines were acceptance tested at that level without any appreciable charring. A long burn could char the ablative liner, and that could present a problem on a rocket restart. In a normal lunar landing there was no requirement for a restart after a long burn because the mission was complete. My job was to evaluate the proposed burns to verify that the LMDE could withstand the duty cycles being considered. I had two sources of data to evaluate charring conditions, namely LMDE test results and thermal model analysis. Both were very reliable sources. The proposed second firing was a long burn of 260 seconds consisting of 7 seconds at 10% thrust, 23 seconds at 40% thrust and 230 seconds at full thrust. I concluded, based on the review of LMDE test data, that the chamber would not char through, and that a restart for midcourse correction would be safe. I felt very confident about this because we ran a rocket test at our Capistrano Test Facility where we had a failure of the test support system. This test was a similar profile as that proposed for Apollo 13. In this test, the liner did not char through. To be thoroughly convinced I asked Mike in Redondo Beach to input that profile in his thermal model and determine the char depth. His computations confirmed the test results. I was absolutely sure that we could safely proceed and NASA concurred. Eighteen hours later, the second burn occurred to place the Apollo 13 in a trajectory for a landing 1,100 miles northeast of New Zealand. Since the next firing of our Rocket Engine was scheduled for the following day, I was permitted to get a few hours sleep in one of the adjacent rooms. I needed that badly, as I had been working over 24 hour straight. Working long hours was common because it was easy to lose track of time. The clock I followed was the Ground Elapsed Time (GET) clock which was started when Apollo 13 was launched. Also, I was in a closed room with no windows, so sunrise and sunset occurred without my knowledge. About 26 hours after the second burn a third burn of 13 seconds at 12% thrust occurred. This midcourse correction was performed to accurately place Apollo 13 in the entry corridor at the proper angle. This burn was critical because if the Command Module entered the earth’s atmosphere at too steep an angle it would burn up. If at too shallow an angle, it would skip off into space. Everything worked perfectly and Jim Lovell, Frank Borman and Fred Haise were returned safely. The rescue team in our room cheered like someone scored the winning touchdown in the last seconds of a football game. I saw that the NASA secretary had tears in her eyes as she came around to congratulate each of us. After chatting a few hours I checked out with the NASA engineers, picked up my documents and quietly left. Behind me were engineers who would need to delve into the cause and corrective action associated with the Service Module explosion. That would take a lot of time and would delay the next flights. We all understood that and were prepared to help in any way we could. I wanted to stay but work back at TRW was waiting for me. On my way to the airport I thought over what had transpired over the last few days. It was like a dream. On board the airplane I wrote a summary report of what occurred. It was a good feeling that our Rocket Engine performed perfectly each time it was fired. I was proud of that. What happened to the discarded “lifeboat”? One hour and twenty four minutes before splashdown, Aquarius, the “lifeboat” was jettisoned. It was destined to free fall through the Earth’s atmosphere. What was meant to soft land on the Moon crashed instead into the Pacific Ocean. On July 27th, 1970 I flew to Cape Canaveral to resolve two small leakage problems on LM-9, which was yet to be assigned to an Apollo spacecraft. Leaks were discovered during helium leak testing of the propulsion system during final acceptance. The following morning I met with the NASA and Grumman engineers to understand the problems and define a fix. After working out a plan they led me to the assembly building. Before entering the enormous high bay area, I had to don a bunny suit, a snood and booties to ensure a clean environment. The laughable part of this was after passing through an air lock into the integration and test area I observed a pigeon soaring above the Lunar Module. At the end of the room were huge floor to ceiling double doors which are opened when moving spacecraft in or out of the building. Apparently the pigeon took the opportunity to inspect the Lunar Module before the door was closed. We fixed the problems by cleaning up an O-ring groove in one case and retorquing the flange bolts in the other. I don’t believe LM-9 was ever assigned to a flight vehicle. Apollos 18 - 20 were canceled, and it may have been meant for one of those vehicles. This trip was my second and last trip to Cape Canaveral on the Apollo Program. I felt fortunate to have had those two experiences at the Cape. Meanwhile the cause of the Apollo 13 Service Module explosion was determined and the corrective action applied to all subsequent flight hardware. Based on the thorough failure analysis conducted and the corrective action specified, the space community felt confident that we could continue lunar exploration. On January 31st, 1971 Apollo 14 was launched, just eight and one half months after the safe return of Apollo 13 astronauts. I felt that finding and fixing the problems with the service module in such a short time was an unusual accomplishment. The site selected for Apollo 14 was the Frau Mauro region, the area previously designated for the ill fated Apollo 13. The scientists selected this region hoping that the astronauts could find samples of deep seated materials which could yield information of the composition of the lunar interior. I arrived at the Mission Evaluation Room the morning of February 4th, 1971, one day before the scheduled lunar touchdown. I checked with my NASA and Grumman counterparts and parked myself at my usual station to listen to CAPCOM and the Astronauts, Alan Shepard, Stuart Roosa and Ed Mitchell. It was important for me to know where they were in the time line and how the mission was progressing. It was no surprise that after experiencing the difficulties with Apollo 13, I was a little on edge. Having the near disastrous failure in the previous flight, we realized that with the millions of parts that make up the Apollo vehicles, the failure of one critical part or component could ruin our day. On February 5th, 1971, the command and lunar modules were placed in a 12 by 67 mile lunar orbit. Shepard and Mitchell then entered Antares, the Lunar Module, while Roosa remained in Kitty Hawk, the Command Module. After separation, Roosa moved the Command Module to a sixty mile circular orbit and Shepard and Mitchell prepared for the lunar descent. I listened over the headphones as the pair orbited over the lunar surface acquainting themselves with and discussing the craters of the Frau Mauro region. At a precise time Shepard commanded the powered descent and our engine built up to full thrust. Combustion stability was very smooth as he throttled up and held full thrust for several seconds. As landmarks were recognized and altitude diminished the engine was throttled down. Soon Cone Crater, a point of interest, was seen and the landing site located. Antares landed softly and the engine was shut down. I recorded the burn time of 12 minutes and 47 seconds with my stopwatch. I walked over to the Xerox machine and photocopied the face of the stopwatch for pasting in my notebook. There was about four percent propellant remaining and the computed mixture ratio was approximately 1.59, well within acceptable limits. Of course, any successful soft landing would be considered acceptable regardless of the propellant remaining or the value of the mixture ratio of consumed propellant. Again I was proud of the fact that our engine had performed flawlessly. With three successful lunar landings under my belt I prepared for the Apollo 15 mission. Apollo 15 was launched July 26th, 1971 for a planned lunar landing at Hadley Rille region on July 30th, 1971. The powered descent was flawless as usual. The engine combustion stability was smooth, the mixture ratio of consumed propellants value was 1.59 and the remaining propellant was five percent. The last two moon landings performed by the Lunar Modules of the Apollo 16 and 17 spacecraft were as flawless as the previous four flights. I was very fortunate to be present at the Mission Evaluation Room for all six moon landings, and very proud of the flawless performance of our TRW Lunar Module Descent Engines. It was a rare opportunity to have the responsibility I had for those missions, and I am eternally grateful for that. Of the seven engines destined to land on the moon, six are on the moon’s surface and one (Apollo 13) rests at the bottom of the Pacific Ocean. I have kept many of the Apollo documents such as the lunar and earth tracking maps, Flight Plans and the LMDE Engine Characteristics Report. Someday someone will deem them priceless. * * *