sinspawn1024

sinspawn1024 t1_j6kpdgy wrote

Reply to comment by WeDrinkSquirrels in Why do sample return missions such as OSIRIS-REx use their own reentry vehicles instead of just going to the space station for pickup and return with ISS equipment? by PromptCritical725

Resupply missions are moving up earth's gravity well. If an engine malfunctions, the craft will lose velocity and altitude due to Earth's gravity. Return missions are falling into Earth's gravity well, so engine malfunction results in continued acceleration. Also, retropropulsion is fundamentally unstable (the force balance is the same as balancing a ruler vertically on your finger), which means that if a system loses attitude control, the craft will much more likely enter a tumbling condition, which if not arrested, will dramatically widen the cone of possible collision.

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sinspawn1024 t1_j5wyzal wrote

Reply to comment by notjordansime in Why do sample return missions such as OSIRIS-REx use their own reentry vehicles instead of just going to the space station for pickup and return with ISS equipment? by PromptCritical725

Even if the probability of collision was very low, do you think Congress will fund a NASA mission where there was a small chance the craft might smash the International Space Station, all its active experiments, and the astronauts of multiple countries into the Pacific Ocean for all the world to see?

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