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SpaceX Discussion Thread


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9 minutes ago, sh1pman said:

Elon is secretly building a giant revolver gun. That shoots cars into space.

The... Spaceman in Black fled across the void, and the... Carslinger followed? :confused:

 

22 minutes ago, tater said:

That 787 fuselage is just under 6m in diameter, BTW. Small, lol.

Relatively.:wink: But also an encouraging reminder that making great big carbon composite tubes is not new technology. It’s understood well enough to pass the rigorous margins and inspections of airliner regulation. Elon’s not reinventing the wheel here, he’s just making it... bigger. :cool:

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2 hours ago, CatastrophicFailure said:

The... Spaceman in Black fled across the void, and the... Carslinger followed? :confused:

I do not aim with my hand. He who aims with his hand has forgotten the face of his father. I aim with my inertial control unit hooked up to my TVC actuators with roll control provided by...

Yeah, never mind.

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1 hour ago, KSK said:

I do not aim with my hand. He who aims with his hand has forgotten the face of his father. I aim with my inertial control unit hooked up to my TVC actuators with roll control provided by...

Yeah, never mind.

I don't get reference. :(

 

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1 minute ago, Wjolcz said:

Is it me or are they actually trying to get everything done as fast as possible?

Given the typical SpaceX jokes about schedules that get tossed around, maybe they’re trying to show that they’re, ahem, “serious.” :rolleyes: If this is their big gamble for the next decade and beyond, the sooner it’s  “real,” the better. 

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1 hour ago, Wjolcz said:

Is it me or are they actually trying to get everything done as fast as possible?

They have 6 years to launch humans to Mars.  The clock is ticking.  

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I think I need to reiterate the importance of Starlink. 4,425 sats. It has the possibility to make vast quantities of money, as well.

Let’s assume Musk’s Mars goals are his real aim, and that it is achievable in some fashion. It will still take money, and lots of it. Contrary to fanboi myth, there is no possible economic driver for Mars. It’s a sinkhole for cash. If he wants to do it, he needs Starlink money. He’s bet the whole sat constellation on flying BFR soon enough to fly at least half of those in 6 years. BFR is the only way that ever happens.

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10 hours ago, CatastrophicFailure said:

But also an encouraging reminder that making great big carbon composite tubes is not new technology. It’s understood well enough to pass the rigorous margins and inspections of airliner regulation. Elon’s not reinventing the wheel here, he’s just making it... bigger.

787 fuseleages don't contain cryogenic fuels nor do they routinely experience the stresses that a rocket fuselage does.  Yes, he is reinventing the wheel.

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Electron, while substantially smaller, is carbon fiber. It also doesn't have an expectation of propellants in the tanks for, well, years, so clearly a different animal, but certainly analogous, at least for Earth orbital operations. They have done enough wet testing, plus a scrub such that it's at least known that their tank can recycle a few times without issues. SpaceX obviously needs a tank for reuse that can take many, many recycles (and a substantial temperature change in between) while remaining intact.

 

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15 minutes ago, DerekL1963 said:

787 fuseleages don't contain cryogenic fuels nor do they routinely experience the stresses that a rocket fuselage does.  Yes, he is reinventing the wheel.

RocketLab Electrons do. :wink: And the same kind of carbon fiber construction has been used for a while in much smaller pressure vessels, like propane tanks. They’ve been made big before, they’ve been made rockets before, and they’ve been made high-pressure cryogenic vessels before. What SpaceX is doing is combining it all into one. 

Remember, they have already made a full-diameter test tank, taken it to flight pressure/temperature, and then deliberately tested it to failure. They didn’t seem to have any insurmountable problems. 

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1 minute ago, CatastrophicFailure said:

RocketLab Electrons do. :wink: And the same kind of carbon fiber construction has been used for a while in much smaller pressure vessels, like propane tanks. They’ve been made big before, they’ve been made rockets before, and they’ve been made high-pressure cryogenic vessels before. What SpaceX is doing is combining it all into one. 

Remember, they have already made a full-diameter test tank, taken it to flight pressure/temperature, and then deliberately tested it to failure. They didn’t seem to have any insurmountable problems. 

So this is where I run out of likes...

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Boeing built a 5.5 m tank for NASA, actually, and the idea has been worked on at NASA for years now.

https://www.compositesworld.com/articles/nasaboeing-composite-launch-vehicle-fuel-tank-scores-firsts

https://www.compositesworld.com/articles/nasaboeing-composite-launch-vehicle-fuel-tank-scores-firsts

I'm not saying it's mature, I expect it to be... interesting when SpaceX tries to operate this thing.

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1 hour ago, tater said:

I'm not saying it's mature, I expect it to be... interesting when SpaceX tries to operate this thing

If there’s to be an “interesting” phase, I expect it to come long before the “operating” phase. 

SpaceX is confident enough in their data that the thing will work that they’re already building tooling and staging it at a factory that hasn't even broken ground yet.  

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4 minutes ago, CatastrophicFailure said:

If there’s to be an “interesting” phase, I expect it to come long before the “operating” phase. 

SpaceX is confident enough in their data that the thing will work that they’re already building tooling and staging it at a factory that hasn't even broken ground yet.  

I have no doubt it can work for some time period. I think the question is one of cycling, particularly once the heat loads on it become more substantial. The principle concern with composites is delamination as I understand it. Holding together for a few hours is one thing, months and years is another.

If nothing happens but a BFingRocket flying---that's interesting, too!

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14 minutes ago, tater said:

I have no doubt it can work for some time period. I think the question is one of cycling, particularly once the heat loads on it become more substantial. The principle concern with composites is delamination as I understand it. Holding together for a few hours is one thing, months and years is another.

If nothing happens but a BFingRocket flying---that's interesting, too!

True enough, and here I look to the 787 again as the archetype. You’ve got 650+ airframes in commercial service going through thousands of pressure cycles (its perhaps worth noting that the 787 operates at slightly higher cabin pressure than other airliners, the why escapes me ATM but it’s related to their use of composites), with some of them in the air for nine years now.

Granted, it’s not the same data points as a rocket, but’s it’s a lot of them, and a huge pool of information to extrapolate from even if SpaceX can only go off what’s publicly available. 

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