Now, Mr. Chairman, with your permission, I would like to ask Dr. Petrone to describe to you what we know today about the events leading to the accident.

The CHAIRMAN. Thank you.

Dr. Petrone?

STATEMENT OF DR. ROCCO A. PETRONE, APOLLO PROGRAM

DIRECTOR

Dr. PETRONE. Mr. Chairman and members of the committee, the Apollo 13 mission, planned to perform a lunar landing at Fra Mauro, was launched at 1413 e.s.t. on 11 April 1970. Lift-off and initial powered flight were nominal. Midway into the second stage burn, an unexpected high level thrust oscillation of the center engine caused that engine to cut off about 2 minutes and 12 seconds early. The remaining four engines burned about 34 seconds longer than planned, to make up part of the deficit. To make up the remainder of the required velocity, the launch vehicle computer extended the third stage orbital insertion burn approximately 9 seconds longer than planned. With the third stage propellant remaining, we still had a capability to perform the translunar injection burn with a performance margin twice that which we normally require. This burn was initiated on schedule and end conditions were nominal for translunar coast. Subsequent docking and extraction of the lunar module from the launch vehicle third stage were performed without difficulty.

PROBLEMS NOTED 54 HOURS INTO MISSION

About 31 hours into the mission, a premission planned trajectory shift was performed. This shift took the spacecraft from a trajectory which would fly around the moon and back to earth, to a trajectory which would require a subsequent maneuver to perform a lunar flyby and return to earth. The purpose of the transfer was to optimize the conditions of time, velocity, and height above the lunar surface upon arrival at the moon. At about 54%1⁄2 hours into the mission, the Commander and lunar module pilot moved into the lunar module to perform a planned transfer of equipment from the command module and preliminary examination of the lunar module. Shortly thereafter, while the crewmen were closing out the lunar module, Astronaut Lovell called mission control to report "We've got a problem here." Initial indications of the anomaly were a warning light indicating an undervoltage on one of the command module spacecraft electrical buses and indication of loss of all pressure in one of the two liquid oxygen storage vessels, followed shortly thereafter by a loss of two of the three fuel cells.

Until this particular problem occurred, the mission had been proceeding in nearly a trouble-free manner. Insofar as we have been able to determine thus far, there were no early indications that the oxygen system was other than normal except for the quantity indicator going off scale high approximately 9 hours before the incident. Following the indications that we had a problem, the immediate requirement was to stabilize the situation to allow time to plan subsequent courses of action. Mr. Glynn Lunney will discuss these actions in more detail later.

In accordance with our general practice, a large number of contractor systems personnel were providing direct support to the mission

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at all times. In order to bring all available resources to bear, we immediately requested the major spacecraft contractors, their subcontractors and vendors, to augment this around-the-clock support. The response of our industrial and university team working with the Government team during this very demanding time was most helpful and gratifying.

With regard to the incident itself and its cause, our immediate analytical efforts during the mission were concentrated only on the analysis necessary to determine effects or delayed effects on other systems. Our prime objective was to ensure that all necessary action was being taken to bring the astronauts back to earth as quickly as possible with the least imposed additional risk.

INTENSIVE INVESTIGATION

Upon completion of the successful recovery of the astronauts, the Apollo program immediately initiated an intensive investigation of the cause of the incident and possible remedial measures. Since last Friday afternoon, a team of Government, industry, and university personnel have assembled at the Manned Spacecraft Center and are reviewing and analyzing all data.

Although it is too early at this time to provide you with conclusive results, the preliminary assessment of the problem and systems involved has caused us to focus our attention on No. 2 oxygen tank and its associated hardware.

If I might have viewgraph No. 1, I will attempt to orient it here. This is the overall view of the command and service module. The area right in here-and I will have another viewgraph on that-is the bay of the section we are interested in. You will see fuel cells on the top, you see oxygen tanks in the center, and hydrogen tanks at the base. (See fig. 1.)

In the next viewgraph this model is a blown up scale of that same sector. Here we see two of the three fuel cells, the third one behind these two. We see oxygen tank No. 2 and No. 1. No. 2 is the one which had our anomalous condition. Then here we see the hydrogen tanks. (See fig. 2.)

SERVICE MODULE (SECTOR IV)

The next viewgraph is the cutaway of the oxygen tank itself. It is 25 inches in diameter. It has the capacity of 330 pounds of oxygen. We have two of these aboard. We normally operate at a pressure of 870 to 930 pounds per square inch. It is made of steel, vacuum jacketed. has an inner and outer liner of very high quality steel. Within the tank. we have an element here called a heating element and two fan motors. The purpose of the heating element is to introduce energy to continue causing the oxygen to remain at the pressure we need in order to feed that to the fuel cells. The fan motors are turned on on command to give a proper mix of the oxygen within the tank. This quantity sensor is the one I referred to, that did go off scale high approximately 9 hours prior to the incident, and there is a temperature sensor here. This is a very simplified diagram, showing the tank basically, the heating element and the sensors, and I will discuss those with the anomalous situation and our telemetry system. (See fig. 3.)

We have a tremendous amount of information on the ground that we did receive. All that can be now analyzed with very accurate time correlation. The preliminary data now shows time correlation of events. I have extracted just a few here to show the indication that we now have of where our problem occurred.

At 55 hours and 53 minutes ground elapsed time, or 10:06 eastern standard time, April 13, we see that the oxygen tank fans are turned on. At 55:53:22, we have a high current spike, fuel cell No. 3. This

fuel cell is responding to a demand for current from somewhere. The demand is improper or an anomaly. We see that 14 seconds later, there is a rise in the pressure of oxygen tank 2; some 2 seconds later, we see another current or rather, an electrical disturbance. This was an 11.3-volt drop on our alternating current bus No. 2. What is significant about No. 2 is it is feeding the power on fan and intake No. 2. There we see a correlation of a voltage drop, a current spike, and a pressure rise.

From there, we have another high current spike on the same fuel cell 3 seconds later.

Four seconds later, we saw a temperature rise; we have been left with an anomaly of about 190° Fahrenheit. This continued to rise from there.

At this time, 55:54:45, we have the maximum recorded pressure. The maximum recorded pressure was not sufficient itself to burst the tank. However, it is recording pressure just prior to release.

At 55:54:53 seconds we have measurable spacecraft motion. This was measured by the guidance system. It is at that time we believe that the tank ruptured, exactly there. The tank pressure read zero 3 seconds later.

And at 55:55:20 plotted Astronaut Lovell reported "I believe we have a problem here." (See fig. 4.)

The next slide, please.

This picture which is very difficult to make out-it has been blown up-is one of the photographs the astronauts did bring back. This area right up here is the area of interest. This is the same bay we were looking at earlier. There are two fuel cells here, the hydrogen tanks here. Right about in here is where oxygen tank 2 had been. We are going through the technique of enhancing these photographs and feel we can learn much from them. Our primary reliance will have to be on telemetry data. (See fig. 5.)