GMG.

[Tenacity]

err rust needs oxygen..... its space, so no oxygen, no oxygen, no rust.
However I'm sure you've noticed the large amounts of Radiation in that system, the long term exposure to the radiation would most likely have caused the metals that make up the ship to decay. Oh and they would probably kill or sterilize any one who attempted to fix it.

well technically we dont know what effects h-fuel have on exposed metal for prolonged periods of time. The radiation is also a factor, as you mentioned - as is the presence of explosive pockets of gas that could damage the ships even further during salvaging operations.

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