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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]

#91

Post by rsynnott »

one2know wrote: post #24
caconym_ wrote: post #15

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…

The Shuttle was built to bring down soviet spy satellites and spacecraft, so in that regard, it was the best design made.

This is a bit of a partial myth. This idea was probably used when negotiating for funding in some quarters, but it was never a particularly plausible use of it, for at least two reasons. First, of course, the shuttle can only access extremely restricted orbits which most targets of interest would not be in. And second, countermeasures would be trivial if the Soviets believed such a threat to actually exist; just incorporate a few kilos of explosives into each device.

I'm reasonably sure this story was always more of a case of "how do we sell this thing" than "this is something that we can actually realistically do".

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

#92

Post by rsynnott »

elil17 wrote: post #79
adamjb wrote: post #29

Earlier quoted context omitted.

Including features that are never used is bad design even if they don't compromise every other aspect of the design. What mainly doomed the shuttle was the DoD requirement that the shuttle be able to pluck a satellite from a polar orbit in one orbit, making it necessary to include the massive wings so that it wouldn't be forced to land in the Pacific as the world rotated underneath it.

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

You absolutely could not conceal a polar shuttle launch. No such thing ever happened.

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

#93

Post by yencabulator »

gregoriol wrote: post #64
marvin wrote: post #63

Earlier quoted context omitted.

Don't see why you're downvoted for posting this. Certainly, satellites designed before the Space Shuttle would have to be very paranoidly designed to include a self-destruct mechanism, but it only takes a couple kilograms of explosives to strongly disincentivize kidnapping it. If I was a military satellite designer, heaven forbid, I'd definitely include that in a world that included the possibility of stealing satell…

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".

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

#94

Post by ufmace »

sebazzz wrote: post #62
paranoidrobot wrote: post #34

Earlier quoted context omitted.

There are four parachutes. It's designed to support at least a single-chute failure, I don't know about multiple chute outages. As for propulsive landing - the latest I can see[1] is that while the craft is technically capable of propulsive landing, it's not approved by NASA, even for emergencies. So it's likely that these options are not even available for the crew, and they wouldn't have trained on how to use it/ac…

Not even for emergencies? Does that mean that it is officially not there, but in the unlikely unlikely event it can be used, or that it really isn't there anymore and the capsule would just drop dead on the ground?

We're not talking about the kind of system where you just turn on the rockets and it'll probably work okay here. Propulsive landing based on running 8 rockets is gonna take a ton of highly tested hardware and software, including speed and orientation sensors etc and all the software to balance things out perfectly.

No way they're adding in a big pile of extra untested software and hardware for an unlikely event. NASA would never approve, and correctly so, as that would be a massive number of extra things to potentially go wrong.

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

#95

Post by interestica »

madeofpalk wrote: post #68
m0xte wrote: post #61

Earlier quoted context omitted.

Think it’s Electron. Doesn’t surprise me. I wouldn’t want to take slack into space with me.

I'm fairly certain there's no Electron on iPad (can't take Chrome to iPad). I also don't think that a native wrapper app that loads (local) html files would display a "Safari" error message. It was probably just a cached/saved website saved to the home screen. I'm not a rocket scientist, but as a web developer, I would rely upon that for anything earth-bound, let alone in Space.

> I'm not a rocket scientist, but as a web developer, I would rely upon that for anything earth-bound, let alone in Space.

...would?

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

#96

Post by anticensor »

paranoidrobot wrote: post #90
sebazzz wrote: post #62

Earlier quoted context omitted.

Not even for emergencies? Does that mean that it is officially not there, but in the unlikely unlikely event it can be used, or that it really isn't there anymore and the capsule would just drop dead on the ground?

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 necessary, a procedure could well be devised to operate the larger thrusters at a lower flow rate, albeit with a diminished efficiency and thrust.

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

#97

Post by ChuckMcM »

drran wrote: post #55
ChuckMcM wrote: post #48

Earlier quoted context omitted.

The idea that you could capture a satellite and return it was part of the mission requirements for the original shuttle design. If it was a 'friendly' or 'unfriendly' satellite was left unspecified. It was also limited by the Shuttle's OMS in terms of delta-v so the orbits from which a satellite could be retrieved was constrained.

Unfriendly satellite can blow up or cause fire inside of shuttle, so it's bad idea to capture enemy satellites. It's like sending billion-worth mine capturer behind enemy lines, which can be destroyed with AK.

I agree with you that hostile satellite recovery would be fraught with challenges. That said, I expect there are people who 'war game' these scenarios all day and probably have various counters or techniques to prevent damage to the shuttle or its bay.

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

#98

Post by madeofpalk »

interestica wrote: post #95
madeofpalk wrote: post #68

Earlier quoted context omitted.

I'm fairly certain there's no Electron on iPad (can't take Chrome to iPad). I also don't think that a native wrapper app that loads (local) html files would display a "Safari" error message. It was probably just a cached/saved website saved to the home screen. I'm not a rocket scientist, but as a web developer, I would rely upon that for anything earth-bound, let alone in Space.

> I'm not a rocket scientist, but as a web developer, I would rely upon that for anything earth-bound, let alone in Space. ...would?

would NOT. Yikes.

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

#99

Post by michaelt »

patmorgan23 wrote: post #85
elil17 wrote: 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.

> There's no such thing as a secret satellite

No known secret satellites :)

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

#100

Post by skissane »

CydeWeys wrote: post #83
kelnos wrote: post #40

Earlier quoted context omitted.

I feel like it's not at all weird to say that something is arriving somewhere in that somewhere's local time zone.

More importantly, that's the timezone Mission Control is in. There are no timezones in low Earth orbit because you're orbiting every 90 minutes, so the only timezone that's relevant to anyone involved in the Mission is the one that all the hundreds of ground personnel are using (in Mission Control and to a smaller extent on the recovery ship).

From my understanding, mission control usually doesn't use their own local time. The choice of time depends on the mission, but common choices are UTC or Mission Elapsed Time. The ISS missions use UTC, since the ISS is jointly controlled by Russia and the US, and neither would agree on using the other's local timezone(s), so they use UTC.

Stuff published to the public is not coming directly from mission control, it is being filtered through NASA PR and SpaceX PR. And PR often tries to simplify things for their audience, like converting UTC (which the average person isn't very familiar with) to local timezone. (And sometimes NASA PR also likes to turn metric into US customary, although SpaceX PR does that less.)

The primary target of NASA and SpaceX's PR is American voters, because it is American taxpayer money that pays for all this. Putting things in terms which makes it easier for an American to understand, but harder for a non-American, makes sense in that context.

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