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41

If mining water on the Moon for H2 becomes a thing, or prop depots with LH2 become a thing, then it would behoove SpaceX to learn how to handle and truck LH2, regardless of whether they ever choose to burn it. As to how long it would take them to develop the capability, I would be very surprised if they haven't already done a certain amount of experimentation. And as to difficulty, according to Dick Mulready, LH2 is not that difficult to handle and burns very nicely, and Pratt spent little time modifying an old jet engine to burn LH2 in the 1950's.

But I was really hoping someone might be able to address my question, and this particular point isn't topical.  :)

Getting off track but it probably would be possible to make Merlin or Raptor run on LH2 as Aerojet did something very similar with the LR-87.
42
One thing you could do is dock at the center, perpendicular to the rotation plane then swing the dumbbell and shuttle assembly 90 degrees around the x axis so the shuttle goes into the main rotation plane.  So a controlled roll.  I think it would have to be a reaction powered roll, with a counter thrust at the correct position.  Would this then be stable?  Seems it would take much less energy than stopping the whole dumbbell.

43
Commercial Space Flight General / Re: Firefly Aerospace
« Last post by Patchouli on Today at 12:00 am »
No reason to believe it can't be done in 3 years. Delta IV first flew in 2002, Delta IV Heavy first flew in 2004, just 2 years later.

SpaceX may have underestimated the difficulty of getting Falcon Heavy flying once Falcon 9 was proven, but part of the reason for the delay is they improved Falcon 9 SO much that Falcon Heavy really wasn't necessary for the vast majority of the flights any more. Falcon 9 now (22800kg to LEO, 8300kg to GTO) has *almost* as much performance (to LEO and GTO) as the original Falcon 9 Heavy concept (24750kg LEO, 9650kg GTO): https://en.wikipedia.org/w/index.php?title=Falcon_9&oldid=133599282 .

Another reason F9 went though four major design changes before FH flew while the Delta IV the initial design was always intended to use parallel staging.

F9 V1.1 was almost a completely different rocket than V1.0.
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Not nessesarally at a point furthest from the axis of rotation, merely in line with the axis of rotation.

(>-------+-------<)
............^

With the station above spinning flat on the screen, (quarter rottion would have arms vertical) docking at the carrot has a much smaller rotational arm, but doesnt destabilize the rotation at all. If the station was rotating perpendicular to the screen (quarter rotation has arms hidden behind one another) then it would be unstable.

While I applaud your use of graphics, unfortunately the problem to be solved exists in the 3D world, and your 2D drawing can't describe the problems and solutions adequately.

For instance, if the station you drew was rotating clockwise or counter-clockwise, and the ^ was a cargo pod trying to dock, then the station would ram into the cargo pod as it rotated.

If our viewpoint was on the plane of rotation, where the ends of the station were coming towards us and receding from us, then the cargo pod could dock at the center of rotation. However, the mass that docks would want to twist into the plane of rotation, making the docking procedure unstable - especially when it comes time to undock.

Make the station a large "X" and you won't get the twisting motion, because that plane has far more mass than the cargo pod can impart.

Does that make sense?
45
Any good drone just flies back home if comms are disrupted unless you also jam GPS, which would probably be illegal. New ones also have collision avoidance sensors.

Exactly.. leading Security directly to the culprit in question only to be caught red-handed, so to speak.  That's the beauty of this system - the guy gets dobbed in by his own drone and there's nothing he can do to stop it happening. "It was him, officer! He made me do it!!" :)

After all, there's no point destroying it or damaging its guidance in some way - you only open yourself up to lawsuits for destruction of property (the culprit's, or someone else's if it crashes).
 
46
Regarding the number of crew on a Commercial Crew flight, we know that the max on the ISS today is limited by them having two 3-seat Soyuz docked at the ISS.

With Commercial Crew, both Dragon 2 and Starliner, I have always heard that NASA wanted to fly in a 4-seat configuration, with 4 crew, with the intent being that they would be able to increase the ISS science output due to having that 7th crew person being able to focus on science and not station upkeep. Those 7 crew would be supported by the 3-seat Soyuz and 4-seat Dragon 2 or Starliner.

I do agree that no one has seriously mentioned flying NASA missions to the ISS with more than 4 crew, but both Dragon 2 and Starliner have the capability to hold up to 7 passengers and crew.

So do we have evidence that NASA no longer plans to fly 4 crew on the Commercial Crew flights? Or we good?  :o
47
 Matt, I think in reality the SLS is dead. Like a beached whale, the death throes will be horrible and sad to watch, at least for those who wanted to see it succeed. They just want to wait until SpaceX and ULA and maybe Blue Origins are a little further along - if those programs don't pan-out quite the right way it would look bad to have prematurely cancel SLS. Hope I'm wrong; I firmly believe all rockets are good, unless they have a warhead on them! On another thread I used the phrase "Stake-in-the heart" for SLS when EUS was cancelled. That action shows we are not serious about this thing any longer...To quote the ending of a great Star Trek episode, it would have been Glorious!
 BTW, I finally got to see the "Brady Bunch" UFO episode with Gemini 4 and Apollo 9 Commander Jim McDivitt that my wife accidentally erased years ago, now that was exciting!  8)
48
Because you're wrong, and they will be using four seats?  They've gone on and on about how this will allow them to expand ISS science by adding a 7th crew member to the station since forever.  They've also talked about how there are two astros assigned to the first crewed flight, with two international partner astros to be named later.

It's almost like you can't read between the lines.

Apparently I can't read between the lines either.  Could you be more explicit?
49
Is the only hope for some kind of decent upper stage for SLS now the Vulcan's Centaur V or ACES? I imagine the Centaur V's capability would result in something halfway between the modified Delta IV-H stage and the full-spec EUS(?)
50
People don't immigrate to Antarctica not because its too inhospitable, they don't do it for they same reason they don't move into a National Park. It's illegal cause it's basically a giant nature reserve so they can't build anything there or work there in any way other than as a scientist.

Sort of true I guess, two nations claim civilian settlements but of course besides community services the core occupation is research.

[ https://en.wikipedia.org/wiki/Esperanza_Base , https://en.wikipedia.org/wiki/Villa_Las_Estrellas ]

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