First-Hand:Testing the Apollo Guidance and Navigation System

TESTING THE APOLLO COMMAND MODULE GUIDANCE AND NAVIGATION SYSTEM AT KENNEDY SPACE CENTER BY JAMES C. MURPHY

From February 1967 through December 1970, I was employed by AC Electronics which later became part of Delco Electronics. During the first year, I was at AC's plant in Milwaukee, WI involved in the vibration testing of the inertial measurement unit. In February of 1968, I was given the opportunity to transfer to AC's Apollo Field Operations at Kennedy Space Center (KSC). I agreed to the transfer as this was a chance to be part of the Apollo Program at the launch site which had been a dream I had had for years during high school and college, never really thinking it would come true. Prior to the transfer, a group of us who had agreed to join the field operations went through a twelve week instruction class on the Apollo Guidance and Navigation System (G&N). AC Electronics was the prime contractor for that system for both the Command Module (CM) and the Lunar Module (LM). As such, trainees for both the CM and LM went through the same classes. Not everyone was assigned to KSC as some went to the CM and LM manufacturing sites at Downey, CA and Bethpage, NY respectively. The G&N system was comprised of three main subsystems, Inertial Measurement Unit manufactured by AC Electronics, Guidance Computer manufactured by Raytheon and the Optical Instruments manufactured by Kollsman Instruments.

At KSC, I was on a test team of three personnel who conducted testing of the CM G&N system in the Apollo Checkout Equipment (ACE) control rooms from the time it arrived to when it cleared the launch tower. There were two test teams for each Apollo mission, one on day shift and one on night shift. When testing the spacecraft, it was a 24-7 operation until that phase of testing had been completed. I was assigned to the even numbered Apollo missions, i.e., 8, 10, 12 and 14. I also participated on the odd numbered missions to help out when they were short on personnel. Similarly, the LM had two test teams working 24-7 during each testing phase.

The first tests consisted of an altitude chamber test, both unmanned and then manned by the astronauts with the CM in the Manned Spacecraft Operations Building (MSOB). The next major test was complete end to end testing of the Saturn V fully assembled in the Vehicle Assembly Building (VAB). This was the most comprehensive and time consuming of the tests. Upon successful completion of the testing in the VAB, the whole Saturn V was transported out to the launch pad, LC-39A for all the Saturn V Apollo launches except for Apollo 10, which was launched from LC-39B. At the pad, the next major testing was an abbreviated end-to-end test of the Saturn V similar to what was done at the VAB. Next came the Count Down Demonstration Test (CDDT) which was conducted first without the astronauts on board the CM and then with them on board. These CDDT's were conducted as if the vehicle would be launched as the rocket stages and the CM would be fueled up, just no actual launch. The next phase was the countdown launch for real. Throughout all of the above testing, the G&N System was put through specific tests to determine its readiness for launch.

One of the most memorable launches I experienced, aside from watching Apollo 11 from the VAB area, was the launch of Apollo 12. The countdown was within two hours of launching and the astronauts, Pete Conrad, Dick Gordon and Alan Bean, were on board the spacecraft going through their final switch positions and systems checklists. The weather was not good as rain and thunderstorms were in the area. Dick Gordon suddenly came over communications net stating he had just seen the numerals on the Display and Keyboard, DSKY, flash all eights. During this time of the countdown, the G&N System was in a gyro-compassing mode which meant it was just maintaining a stable platform after it had been aligned earlier in the countdown. The DSKY, which is the interface display and keyboard with the guidance computer, would be displaying the angles of each of the three axis of the inertial measurement unit or some other information depending on what program had been called up. In any event, having it display all eights was not normal. As the countdown was proceeding, this anomaly which occurred more than once, set in motion a very focused and pressure laden investigation by my supervisor and people he had available for just such a situation. One thought was that with all of the lightning in the area, the system was responding to electromagnetic interference. The disposition of the problem came from the Massachusetts Institute of Technology, MIT, who had designed the G&N system and said they had seen this before in their labs. It was attributed to a contaminant in the DSKY display causing it to momentarily turn on all of the segments in the display. Once that had occurred, the contaminant should disintegrate and not be a problem. That was the explanation provided to me which I relayed to the crew in the spacecraft. By this time it was very close to launch.

The launch came off on time but soon became very exciting. Shortly after launch, less than a minute, we could hear the crew exclaim they lost the platform which meant the G&N system was now unusable. My first thoughts were that now we had launched and not solved the "all eights" anomaly correctly and now jeopardized the whole mission. The information we were receiving in the control room showed a complete loss of the inertial unit and many alarms showing up on the event recorder. I thought I had given a "GO" for launch when it should not have been given. As it turned out, the vehicle had been struck by lightning twice caused by the ionized air from the heat of the flames from the Saturn first stage engines. This was not known immediately so there was a very concerning length of time until that was determined. I don't recall exactly how long but it seemed like a very long time.

Fortunately, the mission went on as planned and the Instrument Unit performed its job. It was the guidance system for the launch vehicle. The G&N served as a back-up system during launch. Once they got in orbit, they were able to reconfigure all the systems in the spacecraft that were affected by the loss of power caused by the lightning strikes. The guidance computer was uploaded and verified to be configured properly. The platform was realigned and no damage had been done to the inertial instruments. The mission continued with a successful lunar landing and return to earth. For me, it was a very pressure packed experience and until we found out what had actually happened, I was very concerned we had launched with a guidance system that had failed.

I had other experiences both in the control room and at the launch pad that I have not documented here but the Apollo 12 countdown and launch is one I will not forget. At the time I was working at KSC, I knew this was a special time and experience. A s the years have gone by, I have become more aware of how lucky and fortunate I was to be able to work there and make a small contribution to one of the most significant and historical adventures ever undertaken. I am forever grateful for that opportunity.