4.3.1 Pre-launch sterilisation

As you have already learned, bioburden reduction is considered from the beginning of a mission. Spacecraft are built in cleanrooms and bioburden is constantly monitored. However, other steps are taken to actively reduce bioburden, which can include applying the following methods to cleanroom equipment, spacecraft hardware or tools being used during assembly:

• Dry heat microbial reduction: exposing items to heat for up to 180 °C for over 1 hour to destroy microbial contamination
• Isopropyl/ethyl alcohol: Cleaning with clean wipes and alcohol to physically remove contamination and disinfect surfaces
• Radiation: Applying gamma, beta, or UV radiation to destroy viable cells and organic molecules
• Wet heat microbial reduction: exposing hardware to temperatures up to 134 °C for 20–30 min to destroy microbial contamination.
• Plasma sterilisation: exposing hardware to a low temperature plasma (ionised gas) to destroy microbes.

Not all of these approaches are suitable for all parts of a spacecraft, for example some electronic equipment may be unable to withstand high temperatures. This means that in some cases, there may be a need for other techniques that can reduce bioburden.