Recent comments in /f/askscience

CountingMyDick t1_j5x2tjs wrote

Reply to comment by fishling 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

To be slightly annoyingly pedantic, the actual return trajectory is most likely nowhere near the ISS, but if they were planning to dock with the ISS, they would presumably cheaply adjust their incoming trajectory to be as close to the ISS orbit as possible while still far away. If they were rather good at it, presumably they could get pretty close to only that 4km/s of total DeltaV to match orbits.

Of course that's still a hell of a lot of DeltaV versus aerobraking.

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CoreMemory_ t1_j5x2o5y wrote

Reply to comment by radioactive_dude in How hot is the steam coming out of nuclear power plants? by ivy-claw

The only notable exception in commercial operation is probably the British AGR (Advanced Gas-cooled Reactor) fleet which uses carbon dioxide as the coolant, circulating at approx 640 °C (1184 °F) which goes through a heat exchanger that’s really more like a traditional power station boiler in many respects. It raises super heated steam, much more like the temperature profile seen in a conventional gas, coal or oil burning plant.

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Hokulewa t1_j5x1h2j wrote

Reply to comment by 17934658793495046509 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

You could really improve your payload mass margin by using aerobraking to match velocity with the Earth, but you would need a shielding device of some kind to protect you from the heat. That would weigh a lot less than the propellant you'd need to use, otherwise.

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LordOverThis t1_j5wz0uy wrote

Reply to comment by sinspawn1024 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

It’d be pretty unlikely to collide with the ISS, since it’s already like trying to shoot a bullet with a smaller bullet on a completely different trajectory. Just guesstimating that it’s probably a margin of error of like a milliarcsecond between “intercepted successfully” and “it flew by so far away it couldn’t be seen”, which would put the difference between “intercepted successfully” and “everyone aboard was killed” at even smaller.

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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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