element affecting the performance of the second element, as occurred in the case of Apollo 13. Of course, in such a study we recognize fully that pressure vessels must not fail, because of their serious impact. Reviews will result in a report and presentation on each subsystem, a screening process, a further review indepth on selected subsystems, and a final presentation given to an Office of Manned Space Flight here in Washington. Throughout the review and presentation process, we will evaluate the adequacy of our engineering team at the centers, at the prime contractors, and at the subcontractor level. A report on actions taken and those remaining on recommendation 9, as well as our actions on recommendations 6 and 7 will be presented to the Administrator by August 25. I believe that such a review will be extremely valuable in refining and developing a new level of understanding for Apollo and for our future programs. I would now like to call on Dr. Petrone, Director of the Apollo program for the Office of Manned Space Flight, to describe the actions to be taken by him relative to the recommendations 1 through 6, which deal specifically with the Apollo program. STATEMENT BY DR. PETRONE Dr. PETRONE. Thank you, Mr. Chairman. May I have chart 1 (fig. 21), please? This shows recommendation No. 1 of the Apollo 13 Review Board. It addresses itself to removing from contact with oxygen all wiring and the unsealed motors which can potentially short circuit, and ignite adjacent materials or otherwise insure against a catastrophic electrically induced fire in the tank. APOLLO 13 REVIEW BOARD THE CRYOGENIC OXYGEN STORAGE SYSTEM IN THE SERVICE MODULE (a) REMOVE FROM CONTACT WITH THE OXYGEN ALL WIRING, AND (b) MINIMIZE THE USE OF TEFLON, ALUMINUM, AND OTHER POTENTIALLY COMBUSTIBLE MATERIALS IN THE PRESENCE OF THE OXYGEN AND POTENTIAL IGNITION SOURCES. CHART #1 FIGURE 21 The second part of that recommendation was to minimize the use of Teflon, aluminum, and other potentially combustible materials in the presence of the oxygen and potential ignition sources. Chart 2 (fig. 22), please. On this chart we show our redesign approach to the oxygen system. Our objective is first to minimize flammable materials and ignition sources, and second, to retain our operational capability. Now, specifically the modifications we will make are in the heater assembly-quantity probe. We will eliminate the unsealed fan motors. We will replace the Teflon-coated wires with steel-sheathed wires. We will change the quantity gage from aluminum to stainless steel. We will eliminate heater thermal switches. To give us an understanding, however, of the temperature on the heater elements, we will add a temperature sensor on that heater element. To improve redundancy in the tank once we take out the unsealed fan motor we will add a third heater element. We also will modify the tank cap to simplify the basic assembly. We must also add a third oxygen tank to the service module to allow us to operate in the low-density regime, once we remove the unsealed fans. This design was already in work as a requirement for the Apollo 16 and subsequent missions. Now, we can take that third tank, modify it as noted above, and introduce that into the service module. This will meet our requirements for Apollo 14 and 15 in the low-density regime. However, for Apollo 16 and subsequent missions where we have REDESIGN APPROACH OXYGEN SYSTEM OBJECTIVE MINIMIZE FLAMMABLE MATERIALS AND IGNITION SOURCES RETAIN OPERATIONAL CAPABILITY SPECIFIC HEATER ASSEMBLY/QUANTITY PROBE ELIMINATE FAN MOTORS REPLACE TEFLON-COATED WIRES WITH STEEL SHEATHED WIRES • CHANGE QUANTITY GAUGE FROM ALUMINUM TO STAINLESS STEEL ELIMINATE HEATER THERMAL SWITCHES ADD TEMPERATURE SENSOR ON HEATER SURFACE ADD THIRD HEATER ELEMENT • MODIFY TANK CAP TO SIMPLIFY ASSEMBLY ADD THIRD OXYGEN TANK OXYGEN DISTRIBUTION SYSTEM ISOLATE TEFLON-COATED WIRES IN SHUT OFF VALVE CHART #2 FIGURE 22 higher oxygen requirements, we will have to review our oxygen subsystem to insure we can meet those requirements. Mr. GEHRIG. Dr. Petrone, will you eliminate the fans altogether or will you just take them out of the tank? Dr. PETRONE. In the module we are discussing for Apollo 14 and 15 we will eliminate them entirely. Mr. GEHRIG. There will be no fans? Dr. PETRONE. None on Apollo 14 and 15. Mr. GEHRIG. How will you keep the how will you get rid of the bubble in the tank formed by the heater? Dr. PETRONE. We have operated down to the regime of 35 percent and have operated for periods of approximately 50 hours without the fan. This is a specific regime we have experienced. But since we have not operated below 35 percent and since we could have the difficulty you are referring to, we put in a third tank to keep us out of the regime in which we do not have experience. However, on this flight we would expect to get that experience which requires zero "g" for a prolonged period of time. The only way we are going to get that experience is through flight testing. But I do note that for Apollo 16, where our demands are even higher than Apollo 14 and 15, we will have to review the need for circulation and it may be necessary to introduce some other elements. However, we will not use unsealed fan motors. Senator GOLDWATER. Dr. Petrone, I notice on your next chart you call for unsealed fan motors, yet you do not show them. Dr. PETRONE. Those are to be removed. I have those as notes to myself. The basic chart would eliminate the unsealed fan motor. In the oxygen distribution system, we will isolate the Teflon-coated wires in the shutoff valve. Here we found Teflon also in the high oxygen pressure area. On chart 3 (fig. 23), I show a basic drawing of what the tank would look like schematically with our modifications. The items on the left are notes which would say, one, we are going to remove the unsealed fan motors. We will use sheathed wires. The quantity probe, which we have to retain will be changed from aluminum to stainless steel. The thermal switches will have been removed. The temperature sensor, the second one will have been added. As I mentioned, we will add a third heater element for redundancy. The tank cap will be modified to simplify the basic installation of the heater probe assembly. Senator GOLDWATER. How can you keep this oxygen in a supercritical stage without some circulation? Dr. PETRONE. Sir, we will do that by the heater. We will keep our pressure up to the 900-pounds-per-square-inch regime and in the high density areas, high density being the regime down to approximately 35 percent, we feel we will get enough heat transfer due to conduction. There will be no convection because you are in zero "g." and we feel that will give us proper distribution. It is in a regime below 35 percent that we have concern, that we have no experience, and for that reason we are adding a third tank for Apollo 14. 47-476 0-70- 5 Senator GOLDWATER. What happens in minus "g." conditions with the supercritical oxygen? It used to be circulated by fans but now you are depending on heat and you are not going to get it-you do not want too much heat in it. How are you going to keep it moving? Dr. PETRONE. Sir, the concern comes in zero "g.", in other words, the forces, negative or positive "g." forces, are in your interest. They will help circulation. However, for zero gravity, the heat transfer due to conduction at the higher density regime will give us a distribution of heat and we can remove the fan as long as we are willing to add a third tank, to avoid the low-density regime. This is an area of the unknown. There are studies which would indicate to us we could go without that. However, we do not feel we want to take just theoretical studies. We want to see the performance of that at least in the Apollo 14 flight. APOLLO 13 REVIEW BOARD THE MODIFIED CRYOGENIC OXYGEN STORAGE SYSTEM SHOULD BE RESPONSE REQUALIFICATION WILL BE ACCOMPLISHED TO: •VERIFY ADEQUACY OF DESIGN CHANGES •VERIFY REDUNDANCY DEMONSTRATE OPERATIONAL MODES CHART #4 FIGURE 24 Chart 4 (fig. 24), please. This refers to recommendation 2 of the Apollo 13 Review Board, that the modified tank should be subjected to a rigorous requalification program. I might state that in the Apollo program we have a specific set of ground rules that we must meet on the ground, in our requalification. We will requalify to verify adequacy of design changes, verify we do have adequate redundancy and demonstrate operational modes, working over many parts of the regime. |