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Aviation History
1963
1963 - 1747.PDF
554 FLIGHT International, 26 September l%i Missiles and Spaceflight KEEPING SPACECRAFT CLEAN New procedures have been announced by NASA for the sterilization of planetary and lunar spacecraft. These are designed to ensure the prevention of the biological contamination of the planets by NASA spacecraft "until sufficient information has been obtained from unmanned missions to assure that biological studies will not be jeopardized." For spacecraft designed to land on other planets, NASA intends to achieve terminal sterilization of the complete capsule by heat. Components will be assembled under clean-room conditions and the complete spacecraft will be subjected to dry heat using a temperature-time cycle that has been proven to render it sterile. The assembly will then be encased in a gas-tight enclosure. "Recognizing that many of the state-of-the-art components used in today's spacecraft would be degraded by heat requirements," NASA states, "a programme is under way to develop components that will be able to withstand the high temperatures required. If, after exhaustive development to obtain heat-resistant components, some critical sub-assemblies still cannot tolerate the heat steriliz ation, it may be necessary to sterilize them by other methods and then incorporate them into the already sterilized spacecraft by sterile assembly techniques." For lunar-landing spacecraft such as Rangers and Surveyors, "decontamination procedures call for clean-room assembly, use of sporicidal agents to reduce the number of microbes on exposed surfaces, and handling methods to minimize contamination prior to launch. "These procedures are less rigorous than those for the planetary landers and reflect the thesis generally agreed to by the scientific community that the Moon possesses an environment hostile to Earth organisms so they could not propagate on the lunar surface." In NASA's Office of Space Sciences, methods of testing for ster ility are being improved, and staff are ensuring that engineering, fabrication and launch techniques will meet the sterilization requirements. The immediate objective is to have "sterilizable" components for the capsules to be launched to Mars during 1966, and efforts are also being initiated to develop a full complement of "sterilizable" parts which can withstand the high temperatures and will be needed for later missions. Past procedures adopted for Ranger spacecraft required that the majority of components and assemblies be sealed and heated to Model of an Apollo astronaut's space suit made by International Latex Corporation for NASA. The back pack is a life-support system which includes a four-hour supply of gases and oxygen, and a power supply for fans to circulate the air in the suit and to operate a communications system. The unit would be recharge able aboard a spacecraft for addi tional four-hour periods 125°C for 24hr prior to their incorporation into the spacecraft. Thii was deemed sufficient to produce sterile units. For certain element! not amenable to heat sterilization, other techniques were applied These included aseptic assembly, the use of special sterilants, am environmental control designed to minimize the numbers of micro organisms. After final assembly and checkout, just after installation aboarc the launch vehicles, the spacecraft was soaked in an atmosphere o sterilizing gas of 12 per cent ethylene oxide and 88 per cent freoi for a minimum of llhr to produce the final surface sterilization During and after this period the spacecraft remained in its sealed gas-tight cavity within the nose fairing of the launch vehicle ant separated by a diaphragm from the other parts of the launcl vehicle. This sealed container was not opened until fairings wen jettisoned during the launch ascent, after leaving the Earth' atmosphere. Although the above procedure was generally used for Range spacecraft, NASA scientists have pointed out that "prior to thi launch of each lunar impacting spacecraft, waivers were approve* for certain elements which were not compatible with interna sterilization procedures. Typical examples of these, taken fron the actual Ranger 4 list, are: six wafer-type batteries, five germaniun transistors, three acceleration switches, retro-motor main propellant igniter and squib. The degree of internal contamination of thes items is unknown, but it is relatively certain that the resultan contamination levels of the Ranger spacecraft were low," Among the successful results of Ranger experience quoted b Oran W. Nicks and Orr E. Reynolds of NASA's Office of Spac sciences are:— (1) Many parts and components used in spacecraft are amenabl to heat and other effective sterilization treatments. (2) Many sterilization techniques and equipment for decor tamination were developed, proved, and can be applied to the futui planetary programme directly. (3) Personnel gained considerable insight into the problems an methods associated with sterilization and decontamination. Some of the "discouraging results" listed by the two scientis include "the realization that the problem of achieving technologic reliability after subjecting certain materials and components to tl sterilization treatment is far more formidable than had been anti ipated. For example, it was found that television tubes, soli propellant for rocket motors, and certain crystals in timers, instn ments, and radios are more vulnerable to heat than had be< suspected. It became very clear during the Ranger experience th treating an entire spacecraft composed of electronics and mai different materials, parts, and sub-assemblies is a significant different task from the problem of sterilizing a surgeon's instf ments or canned foods. All of this experience results in a f greater respect for the sterilization of spacecraft than had earli been the case. "The decontamination and sterilization requirements applied the Ranger were put into effect after the Ranger had already reach an advanced state of development. It is now clearly understoo however, that it is essential to consider the rigours of sterilizatu throughout all phases of design and that considerable empha must be placed early in the design effort on the selection of pai and components which are compatible with the requirements decontamination. "The sterilization procedures employed on the Ranger P# cularly the heat cycle, was suspected of degrading performs and perhaps contributing directly to Ranger failures." Berenice-launched Satellite Press reports from Paris clai"1J: the French Army is working on a small satellite, named An* which it is hoped will be launched next year by the fm*'L Berenice vehicle developed by ONERA with the assistance of» and Sud-Aviation. It is said that the satellite would weigh and carry some instrumentation and telemetry. Estimated co the project is given as £3,570,000.
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