NASA is investigating contamination on the International Space Station – and paint on a SpaceX capsule could be to blame.
Sensors onboard the ISS designed to measure ozone molecules and aerosols in Earth’s atmosphere have picked up worrying levels of chemicals.
The increases have been linked to the docking of SpaceX Dragon cargo capsules – and it is believed paint on them could be to blame.
The SAGE III sensor, which launched in February 2017, saw unexplained spikes in contamination when the next Dragons docked at the Space Station.
Molecules were being released by the capsule in a reaction known as outgassing, causing them to sticking to SAGE.
The phenomenon happens when molecules trapped inside material is released, and is the process behind the ‘new car smell’ in a vehicle.
In space, these can be extremely damaging, and on the ISS, they could imapct delicate measurements being taken.
They can also creates a greasy film, which could impact portholes on the station.
To stop the problem, most space hardware is built in clean rooms and even ‘baked’ to remove contaminants.
NASA was at first baffled by the rise.
‘An external payload is both a source and a receiver of contamination,’ a NASA report into contamination warned.
‘ISS Space Environments Team considers both roles during integration of the payload.
‘Thus, Space Environments must evaluate all external payloads as contamination sources, regardless of sensitivity to contamination.’
Experts now believe the ISS issue may be down to outgassing from the visiting Dragon capsule.
Antonius de Rooij, author of the Space Materials Database, told Wired he believes the capsule’s paint is the likely problem.
He said the size of the capsule, all of which is painted white, could be key to the problem.
The results are preliminary, according to Wired, but Dragon may have deposited, according to this presentation, up to 21 times the allowed amount of contamination on one sensor.
SpaceX says NASA pre-approved all the materials used in the Dragon, and said it is working with suppliers to develop a new variant of paint.
‘SpaceX has scrutinized all external material selections on Dragon and is working with suppliers to custom-develop low outgassing variants of qualified materials to help improve the molecular deposition rate,’ it said.
The white paint is made by Alion, and was specially developed for NASA and SpaceX.
‘For decades, Alion has produced coatings to protect against the rigors of space,’ said Michael Kenny, senior chemist with Alion, said when it was first used.
‘As space missions evolved, there was a growing need to dissipate electrical charges that build up on the exteriors of spacecraft, or there could be damage to the spacecraft’s electronics.
‘Alion’s research led us to develop materials that would meet this goal while also providing thermal controls. The outcome of this research was Alion’s proprietary Z-93C55 coating.’
However, if Alion Z-93 gets contaminated after curing, it’s prone to degradation when UV rays hit it, a phenomenon first documented in 1971.