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NASA Astronauts Return Home in SpaceX's Crew Dragon Spacecraft [video]

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Re: NASA Astronauts Return Home in SpaceX's Crew Dragon Spacecraft [video]

#101

Earlier quoted context omitted.

You're not wrong, but I think it's cool how much safer the generic capsule design is than something like the Shuttle. Really the Shuttle got a whole lot wrong—heat-intolerant aluminum structure and critical, sensitive machinery directly beneath a layer of tiles so fragile you can crush them in your hands (IIRC). SpaceX's Starship will probably be a lot more tolerant to defects in the heat shield because of the relati…

This is at the stage where you cant really make assumptions about what may happen because you don't know what could go wrong. (A.K.A you don't know what you don't know).

All you need to bring a traditional capsule design down to ~sea level terminal velocity safely is a blunt body with offset CG and the kind of circular ablative heat shield that's been shown over decades to be simple, safe and reliable. You don't even need active control unless you want more precision for hitting your landing target. The biggest risk, assuming your position and velocity were correct at interface, is the parachutes–which is why SpaceX took so much time testing and refining them.

Things can always go wrong, but we know enough about both classes of vehicle to be able to say that the Shuttle's design was in general terms both more complex and more risky.

This is slightly off topic, but the Shuttle was horribly unsafe on the way up as well as on the way down. Using solid rocket boosters with no means to get the crew safely off the stack until they stop burning is, for lack of a better word, demented. The Crew Dragon/Falcon 9 stack offers realistic abort modes from the moment fueling begins until the vehicle reaches its intended orbit.

Re: NASA Astronauts Return Home in SpaceX's Crew Dragon Spacecraft [video]

#102

Earlier quoted context omitted.

Further reply, this question was just asked and answered on the new live-stream. Official response from SpaceX: Superdraco thrusters are completely inhibited once the launch is sucessful. So, no, not even as a backup. Also, one other thing I remembered - the draco and superdraco thrusters require different pressurisation levels for their fuel systems. Before launch, the system is put into a high pressure mode, to ena…

Repressurisation hardware has to exist anyway to have restartability (it takes 15 minutes to switch to high pressure feed, 15 seconds to low pressure feed). Do you know which component has inhibition affected? SW only? Blown fuse? Something different? Certainly not a jettisoned part, because this vehicle is planned to be reused after minor refurbishment. PS re repressurisation failures: If it becomes absolutely neces…

> Do you know which component has inhibition affected? SW only? Blown fuse? Something different? Certainly not a jettisoned part, because this vehicle is planned to be reused after minor refurbishment.

They didn't elaborate, it was a 30 second response.

Re: NASA Astronauts Return Home in SpaceX's Crew Dragon Spacecraft [video]

#103
post #79

Earlier quoted context omitted.

If they’d used those features it wouldn’t be public knowledge

Yes it would. There's no such thing as a secret satellite, it's impossible to hide them. General astronomy would notice that their's one less satellite.

https://en.wikipedia.org/wiki/Misty_(satellite)

Re: NASA Astronauts Return Home in SpaceX's Crew Dragon Spacecraft [video]

#104

Earlier quoted context omitted.

Even without self-destruct, a satellite not programmed to be captured could simply fire some thrusters if it detects an orbit change, and that would likely make some big dammage inside the capturing shuttle.

That's typically ion thrusters, isn't it? That's very low mass at very high speed, and would probably take hours to even leave scorch mark. It would feel like a slow breeze. Of course, military use could do something different, but that's more along the lines of "pack a kilogram of explosives in a pipe bomb".

Hydrazine thrusters more likely. Ion thrusters are novel.
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