Further Study Of Fire Problem In Spacecraft

Press, Volume CVI, Issue 31330, 29 March 1967, Page 11

Further Study Of Fire Problem In Spacecraft

(By NEAL STANFORD in the “Christian Science Monitor”) WASHINGTON. There were no fire extinguishers in Apollo 204 when fire broke out last January. The omission was intentional. At least four different methods of extinguishing fires in spacecraft have been experimented with. All four were discarded. They are, however, being restudied in the wake of the January 27 disaster.

Dr. George E. Mueller, associate administrator for manned space flight, of the National Aeronautics and Space Administration, recently told congressmen who asked about fire extinguishers: “The fact is, we don’t have a good way to put a flame out in a spacecraft.” He also reported: “Our tests with fire extinguishing methods are not encouraging.”

These comments raise two questions: what methods have been tried for extinguishing interior spacecraft fires and what is wrong with them? Four Principal Systems The principal methods being tested are: Use of chemical extinguishing agents; Dilution of the oxygen atmosphere with inert gases; Use of water sprays; Cabin depressurisation.

The primary concern, when these studies were made, centred on the possibility of a fire in the cabin when the astronauts were in space. The possibility of a cabin fire when on the pad was not ignored, but it. was largely discounted. The effectiveness of these four methods in putting out fires in a spacecraft, then, have to be examined both for on-pad and in-space situations in the light of the January 27 fire.

Chemical extinguishing agents have ben largely ineffective. They have actually drawn in enough oxygen from the spacecraft atmosphere to cause the fires to burn even more vigorously. This has been true even of bromotrifluoramethane (CF 3BN)—used effectively for aircraft fires. Inert Gases

Experiments with inert-gas extinguishers also have been ineffective. The gas streams from such extinguishers have drawn enough oxygen from the spacecraft atmosphere to make the fires burn even brighter. Tests using inert gases, such as nitrogen, as a diluent indicate that the turbulence resulting from introduction of this gas has caused even more intense burning.

Water sprays have so far proved the most effective way to douse a space-cabin fire. But there are drawbacks to the use of water.

Water can do damage to the electrical equipment A water spray system for the cabin interior would also be complicated. It would raise weight problems. The use of water sprays, then, has been frowned on as raising more problems than it would solve.

Shipping Telegrams

AUCKLAND, March 28. Arrived.—Athel Viscount (2.50 p.m.), Marsden Point. To arrive.—Straat Le Maire (8.30 p.m.), E. Africa. To sail.—Ceramic (7 p.m.), Lyttelton. __ NEW PLYMOUTH, March 28. Arrived.—Sea Search (7.15 a To'*sall.—Wafrangul (7.30 p.m.), Wellington. „ . „„ WELLINGTON, March 28. Arrived.—Ngatoro (1.5 a.m.), Geelong. Sailed.—Matipo (5.25 p.m.), Nelson. TIMAB u t March 28. Sailed.—Hanetia (6.45 a.m.), Marsden Point. _ „ DUNEDIN, March 28. To Arrive.—Poranui, Onehunga. To Sail.—Calm, Timaru,

Cabin depressurisation would be primarily useful when in space. If the oxygen in the cabin were let out there would be no oxygen inside to keep the fire burning. It go out However, the men would have to be suited—not in shirtsleeves environment. In a decompressed cabin astronauts would have to breathe through the environment control system of their suits.

Cabin depressurisation would not be an effective fire extinguishing method on the pad. While the oxygen pressure would be 16 p.s.i. (pounds per square inch) inside the cabin, it would only fall to 14.7 p.s.i. when depressurised. Oxygen would still be present to feed the fire, though at a somewhat slower rate.

Combustion Characteristics In these studies the combustion characteristics of the various materials used in the spacecraft have to be examined. It is important to know what these characteristics are not only when in zero gravity in space, but also on the pad, and at 7 to 12 G’s, which can be reached when the spacecraft is going into space and returning. Experiments have shown that, after ignition, flames in a spacecraft would disappear due to the lack of movement of air currents. But they would flare up again as oxygen reached the fire due to crew movements, fans, and the like. "Trade-offs”

Dr. Mueller, who in the matter of manned space flights speaks for the National

Aeronautics and Space Administration says the question of whether to install an extinguishing system in the Apollo spacecraft is a matter of “trade-offs.” A fire extinquishing system might offer some limited capability to put out a fire. But it could increase the toxic environment of the cabin. Previous studies of fire extinguishing equipment resulted in such equipment being excluded from manned spacecraft The whole matter has been reopened and is being reviewed. But for the moment Dr. Mueller does not see any method as an effective way to put out flames. It would be somewhat easier to use any of these methods in space than on the pad. Still both for on the pad and in space, the only sure protection is to prevent fires from breaking out.