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|  | | | | | | | | A typical sterilisation process for a lander, in this case Beagle 2 | |
Dry heat sterilisation process to high temperatures
This activity was approved by the Aurora Board of Participants within the Work Plan 2006-2009 as part of the core programme 2006-2009 and should be initiated by the end of 2006.
Dry heat sterilization is an approved method to reduce the bioburden on flight hardware prior to launch. However, the NASA standard dry heat sterilization specification exists only for the range of 104ºC to 125ºC, with strict humidity control. The only approved high temperature limit to confer sterilization is 500ºC for at least half a second. Flight hardware manufacturing processes as well as entry heating during atmospheric entry occur at a wide range of temperatures, mostly at levels above 125ºC but below 500ºC and without controlled humidity levels.
Extending the temperature region from 125ºC to about 300ºC and at the same time investigate the impact of humidity on the inactivation of biological challenges will potentially offer flight projects the following advantages:
- Full credit for high temperature exposure of hardware during manufacturing process, even if temperature is below 500ºC;
- Full credit for the entry heating sterilizing effect on the heat shield and back-shell, even if temperature is below 500ºC;
- No specific validation of non-humidity controlled dry heat sterilization process used on spacecraft systems (e.g., parachute, air bags);
- No need for using a pressure chamber for the dry heat sterilization process on sub-system or system level.
All these effects will make it easier for flight projects to implement required planetary protection standards by avoiding additional tests and flight representative hardware development for these tests. At the same time the revised bioburden allocation will reduce the sterilization requirements for other parts of the spacecraft.
The steps to verify inactivation rate constants at temperatures beyond the standard NASA dry heat sterilization temperatures and outside a controlled humidity environment are:
- Definition of a biological challenge that can be used to verify the process based on isolated strains from the spacecraft environments and compare it to the standard biological challenge used in the health care industry;
- Definition of experiment design and process parameters for use at temperatures beyond 125ºC;
- Determination of inactivation rate constant of the selected biological challenge depending on humidity level;
- Determining of inactivation rate constant of the selected biological challenge depending on the temperature.
| Start | Expected
or actual duration | Status | Prime contractor | | TBD | 8 months | Being defined | TBD |
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Last update: 22 May 2006 | |
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