SpaceX (Vol. 2)
Discussion
CraigyMc said:
Timothy Bucktu said:
Not for the fanboys, but interesting take if you have an open mind...
https://youtu.be/nxG0WAwwrGk?si=5XSKp3KZNQdGZdCR
Destin's cool. It's hard not to like a guy who wanted to know what a supersonic baseball would do, so built one and tested it with super slow-mo video for Youtube.https://youtu.be/nxG0WAwwrGk?si=5XSKp3KZNQdGZdCR
He's got access to a lot of places you can only go with US security clearances (he was in R&D for the military) - for example on an active US nuclear submarine. His dad's been in several of the videos, he's a NASA staffer who does metronomy (weights and measurements) for a living, on things like the Webb telescope, which he's also got a video of.
The video you linked to is a 3rd party review of an older Destin video from last year or thereabouts where he was asked to give a talk at a NASA convention and more or less said "you're not being honest with each other", which is from my point of view completely accurate. It went down like a lead balloon.
His heart is in the right place, but his audience don't care about that -- it's their salaries on the line.
CraigyMc said:
Destin's cool. It's hard not to like a guy who wanted to know what a supersonic baseball would do, so built one and tested it with super slow-mo video for Youtube.
He's got access to a lot of places you can only go with US security clearances (he was in R&D for the military) - for example on an active US nuclear submarine. His dad's been in several of the videos, he's a NASA staffer who does metronomy (weights and measurements) for a living, on things like the Webb telescope, which he's also got a video of.
The video you linked to is a 3rd party review of an older Destin video from last year or thereabouts where he was asked to give a talk at a NASA convention and more or less said "you're not being honest with each other", which is from my point of view completely accurate. It went down like a lead balloon.
His heart is in the right place, but his audience don't care about that -- it's their salaries on the line.
It can't have been received that badly as they had him back recently in the Neutral Buoyancy Lab.He's got access to a lot of places you can only go with US security clearances (he was in R&D for the military) - for example on an active US nuclear submarine. His dad's been in several of the videos, he's a NASA staffer who does metronomy (weights and measurements) for a living, on things like the Webb telescope, which he's also got a video of.
The video you linked to is a 3rd party review of an older Destin video from last year or thereabouts where he was asked to give a talk at a NASA convention and more or less said "you're not being honest with each other", which is from my point of view completely accurate. It went down like a lead balloon.
His heart is in the right place, but his audience don't care about that -- it's their salaries on the line.
If anything, I think it was more him supporting what NASA are doing with Artemis.
They also need to action on their expectations of the current provider of the Human Landing System contract not fulfilling their obligation.
Many of them have known this since the start.
hidetheelephants said:
t doesn't bode well for Artemis, as he's described it it's both profligate and unlikely to work. Keep it simple, stupid.
Artemis is a pathfinder for later missions. Being able to land significant mass on the Moon, sustain life for longer, maintain an orbiting staging post, and so on are critical for a potential Mars mission.Of course it is possible to do an Apollo redux, but that doesn’t move the game on. That’s why the Starship approach is valid. If it pans out, it is a significant step toward the sort of missions depicted in the book & film “The Martian.” AIUI the Blue Origin approach can’t put anything like as much payload on the Moon; it is a single-purpose design that doesn’t move the game on anything like as far.
It's not valid if it doesn't work and this seems destined to fail; a moon shot that's reliant on getting a dozen launches to occur in a short enough time to conduct the refuelling without excess boil-off is insane and will fail. A couple would be ambitious, suggesting an upper lander weight of ~20t would be more likely to get there and back without failing and killing the meat puppets.
It could work with a high enough launch cadence to minimise boil off and schedule delays. And if there's one thing Spacex have proved it's the ability to deliver a step change in launch cadence. But it does seem like Starship is "too much ship" for the current Artemis mission requirements.
hidetheelephants said:
It's not valid if it doesn't work and this seems destined to fail; a moon shot that's reliant on getting a dozen launches to occur in a short enough time to conduct the refuelling without excess boil-off is insane and will fail. A couple would be ambitious, suggesting an upper lander weight of ~20t would be more likely to get there and back without failing and killing the meat puppets.
I must admit it’s all very ambitious and a bit unnecessary for a first shot. I do wonder why a smaller - but still massive by normal standards - lander couldn’t be made by having a Starship nosecone section as the lander. 
Eric Mc said:
I still think that a tougher and much more robust craft designed along similar lines to the Apollo Lunar Module is what is needed.
I may be due a whoosh parrot where, but wasn't the LM the least robust bit of Apollo?The structural walls were about the thickness of a soda can of the era.
Dog Star said:
hidetheelephants said:
It's not valid if it doesn't work and this seems destined to fail; a moon shot that's reliant on getting a dozen launches to occur in a short enough time to conduct the refuelling without excess boil-off is insane and will fail. A couple would be ambitious, suggesting an upper lander weight of ~20t would be more likely to get there and back without failing and killing the meat puppets.
I must admit it’s all very ambitious and a bit unnecessary for a first shot. I do wonder why a smaller - but still massive by normal standards - lander couldn’t be made by having a Starship nosecone section as the lander. CraigyMc said:
Eric Mc said:
I still think that a tougher and much more robust craft designed along similar lines to the Apollo Lunar Module is what is needed.
I may be due a whoosh parrot where, but wasn't the LM the least robust bit of Apollo?The structural walls were about the thickness of a soda can of the era.
RacerMike said:
CraigyMc said:
Eric Mc said:
I still think that a tougher and much more robust craft designed along similar lines to the Apollo Lunar Module is what is needed.
I may be due a whoosh parrot where, but wasn't the LM the least robust bit of Apollo?The structural walls were about the thickness of a soda can of the era.
I would envisage a similar styled machine docked permanently with the Lunar Gateway space station powered by storable hypergolic fuels. The storable propellants could be brought to the Gateway by a Starship type vehicle. We have extensive experience of transferring hypergolic fuels in space. The Russian Progress supply craft has used this technology for years.
I think the Blue Origin lander proposal was close to what I am describing -
hidetheelephants said:
It's not valid if it doesn't work and this seems destined to fail; a moon shot that's reliant on getting a dozen launches to occur in a short enough time to conduct the refuelling without excess boil-off is insane and will fail. A couple would be ambitious, suggesting an upper lander weight of ~20t would be more likely to get there and back without failing and killing the meat puppets.
Boil off isn't nearly so much of an issue for methalox as it is for hydrolox. Hydrogen tank boil off of 0.13% per day was achieved in one test - the LOX boiling off an order of magnitude slower. CH4 would imitate that latter more than the former.A sunshield could help, although in low earth orbit the Earth itself is actually going to be a big source of heat. Still, flip a starship upside down and it's already roughly right - shiny steel surface reflects incident radiation from Earth, black heat shield aids emission of heat into space. Either deploy a sunshield from the nose or omit the thermal tiles there and point that towards the sun.
Total radiated power from the heat shield with a target temperature of 90K:
Earth irradiation is about 230W/m2, so if it was perfectly black it would absorb 103 kW.
So we need a surface with an albedo of 0.99.
The whitest paint available has an albedo of 0.98.
So it is actually possible to get quite close.
Active cooling with refrigerant could make a substantial difference too.
Eric Mc said:
What's wrong with storable hypergolic fuels?
This all seems to be a consequence of adapting a vehicle i.e. Starship, which was designed originally with Mars as a target and is now being repurposed for lunar use.
Hypergolics are nasty to work with, and would need a new engine type fitted. The moon is categorically easier than Mars (bar the ISRU factor once you actually land).This all seems to be a consequence of adapting a vehicle i.e. Starship, which was designed originally with Mars as a target and is now being repurposed for lunar use.
Raptor as an engine design is very much jack of all trades.
Having one basic design with minor tweaks is much easier from an R&D and manufacturing standpoint than designing an entirely new vehicle, would seem to be SpaceX's view.
Economies of scale.
Edited by Solocle on Thursday 18th April 12:08
But non-fitness of purpose.
We know hypergolics are dangerous - but we've been using them (and still do) for many, many applications in spaceflight. They are well understood and, if handled correctly, are no more dangerous or tricky than using cryogenic fuels and propellants (which come with their own handling issues).
Don't forget that the proposal to use a cryogenic booster stage in the Space Shuttle programme (the Centaur) was dropped in favour of a hypergolic alternative ((the Inertial Upper Stage - IUS) on safety grounds.
Trying to have a "one size fits all" type of rocket may turn out to have been a very bad and impractical idea.
We know hypergolics are dangerous - but we've been using them (and still do) for many, many applications in spaceflight. They are well understood and, if handled correctly, are no more dangerous or tricky than using cryogenic fuels and propellants (which come with their own handling issues).
Don't forget that the proposal to use a cryogenic booster stage in the Space Shuttle programme (the Centaur) was dropped in favour of a hypergolic alternative ((the Inertial Upper Stage - IUS) on safety grounds.
Trying to have a "one size fits all" type of rocket may turn out to have been a very bad and impractical idea.
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