Recent comments in /f/askscience

Nemisis_the_2nd t1_j5y7nt7 wrote

Reply to comment by oz6702 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

> Still, slowing down to match orbit with the ISS is something that's gonna cost you a ton of fuel either way

Aerobraking, as you suggest, is the answer. It's how we used to do it for a long time before more effective technology and better understanding of orbital trajectories came along.

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Nemisis_the_2nd t1_j5y7igp 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

That's really not a big problem. Coming back fro somewhere like Mars, you'd need to alter the tragectory by a fraction of a degree to flip the reentry trajectory 180^0.

From there, you could bleed off speed like in early space missions with rounds of aerobraking.

The original commenter makes a good point about fuel weight, but its also got less to go wrong if you just slam the vehicle into the atmosphere one time.

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Alblaka t1_j5y6ikr wrote

Reply to comment by dWintermut3 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

I'd suggest that performing a precise aerobrake in reality might be slightly more difficult than in an abstracted simulation, i.e. due to the simulation always being 100% accurate, whilst any modelling of our actual atmosphere might be less precise.

It's easy to do a full aerobrake, and it's relatively easy to avoid aerobraking. But treading that fine line between might be a bit unfeasible in an unsimulated environment.

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abs-licker-69 t1_j5y4gg5 wrote

Reply to What determines whether we can create a vaccine for an illness or not? by ShelfordPrefect

Making a vaccine is for achievement of introduction of the agent to the body. Body reacts to new, vaccine, agent primarily... which is mild. The subsequent attacks are handled vigorously. As body acts specifically for specific agents, you need to keep in mind how you making the vaccine will affect the receivers. Basically, briefly speaking... vaccine is nothing but part/whole of the disease agent, modified to not make receiver ill but good enough to introduce nd initiate a host defence mechanism. HIV directly targets the immune cells, and turns them into a factory of new infected cells, so to find a safe way to introduce it into a human with controllable outcomes, it'll be a complex process... moreover, HIV is an RNA virus, which means the mutation rate among HIV offsprings is frequent, that mean one vaccine made for a type of virus may/may not be effective against the mutated virus now... Okay this is the simplest i could make it😮‍💨

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Westerdutch t1_j5xzuyk wrote

Reply to 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

tl;dr because falling down even if you have to carry something bulky to survive the fall is still a lot easier than trying to exactly meet up with the fastest moving manned structure in existence. Not only does the latter take a LOT of speed but the precision required is also absolutely non-trivial (and if it goes wrong youll still fall down so you would still need the bulky fall protection).

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