Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The Lunacy of Artemis

idlewords.com

Post reply on HN
Print view View original

491–500 of 539 posts

Re: The Lunacy of Artemis

#491

Post by geertj »

objclxt wrote: post #249
geertj wrote: post #239

Earlier quoted context omitted.

Why is cryogenic propellant transfer any more difficult than other difficult things SpaceX have already done (eg landing a rocket, and building a full flow staged combustion engine)? They do this on earth every time they fuel the rocket. I understand it will be more difficult in space, but I don’t see why specifically this problem is the real engineering target over say, reuse.

> They do this on earth every time they fuel the rocket. I understand it will be more difficult in space, but I don’t see why specifically this problem is the real engineering target over say, reuse. The article goes into this in some detail. In particular: * You have to get the propellant into space. This is going to take a large number of flights (~15) at a pace that has not been done before for a vehicle of that s…

Yes, the article lists a few reasons, none of them convincing. Specifically:

> You have to get the propellant into space. This is going to take a large number of flights (~15) at a pace that has not been done before for a vehicle of that size (a launch every six days)

SpaceX has done 2 Falcon 9 launches in 1 day, and they would have done 3 if the third one had not have been scrubbed [1]. I really don't think that launching Starship is going to be any different, especially as it was specifically designed for reuse, unlike Falcon 9.

> You need to launch at pace because otherwise the propellant will boil off, which is another issue - you need to shade or insulate the propellant for a much longer period of time in much harsher conditions

First part is same argument as above. Second part (shading) - again, I don't see why it is harder than other hard things. Just add more insulation. Possibly do some passive or active cooling.

> There is no gravity: whereas on earth the propellant separates relatively cleanly into liquid and gas this isn't the case in space

Very similar problem to how you feed liquid propellant into a rocket engine when it relights in zero gravity. You use a small ullage thruster for this.

[1] https://news.satnews.com/2024/03/31/spacex-enjoys-two-out-of...

Re: The Lunacy of Artemis

#492

Post by geertj »

K0balt wrote: post #244
geertj wrote: post #239

Earlier quoted context omitted.

Why is cryogenic propellant transfer any more difficult than other difficult things SpaceX have already done (eg landing a rocket, and building a full flow staged combustion engine)? They do this on earth every time they fuel the rocket. I understand it will be more difficult in space, but I don’t see why specifically this problem is the real engineering target over say, reuse.

I wouldn’t go so far as to say it is the “real” engineering target, but it is a foundational capability that underpins the ability for humans to explore beyond the earth-moon system, and it is fraught with difficulty and uncertainty. Fuel transfer and storage in orbit is problematic in many respects.

Very hard and foundational capability need not be correlated though. I think the more likely explanation that orbital refueling hasn't been done yet is not that's it's exceptionally hard, but that there hasn't been a need for it. Orbital refueling needs rapid reuse, and that has only been possible recently (with Falcon 9, and soon Starship).

Re: The Lunacy of Artemis

#493

Post by zajio1am »

fastball wrote: post #475
Dalewyn wrote: post #454

Earlier quoted context omitted.

SpaceX is a space exploitation business, Starlink being the foremost example but also commercial and governmental launches of Falcon 9 and eventually Starship. Even going to Mars is ultimately a mission of exploitation, not exploration. Space exploration is the duty of governmental space agencies such as NASA, who (assuming sufficient budgeting) can all literally afford to run red ink for entire projects and not have…

I think space expansion business might be more appropriate verbiage. "Exploitation" has connotations of man-vs-man colonialism, which I don't think apply in the case of outer space.

'Exploration' / 'exploitation' are established terms for this kind of trade-off, see

https://en.wikipedia.org/wiki/Exploration-exploitation_dilem...

Re: The Lunacy of Artemis

#494

Post by PaulHoule »

ryandrake wrote: post #329
kqr wrote: post #296

Earlier quoted context omitted.

> The moon is not so far away in terms of distance but it is very far away in terms of Δv because, not least, you have to land propulsively because there is no atmosphere to slow you down. Not least, but certainly the requirement to brake before you land must be on the small order compared to achieving escape velocity from the much bigger rock I'm on?

Everything is on the small order of magnitude when compared with getting into Earth orbit. As the quote goes, "Once you get to earth orbit, you're halfway to anywhere in the solar system."

That might be Heinlein's most annoying quote ever and boy does it have competition.

It is very expensive to change orbits. If you had two space stations like the ISS with ascending nodes 180 degrees from each other it would be about as expensive to transit between them as it is to launch a rocket from the Earth to begin with. See

https://caseyhandmer.wordpress.com/2019/10/02/there-are-no-g...

You've got the advantage in space that you can use electric rockets with a high specific impulse. Back in the 1950s folks like von Braun imagined that manned space flight might use electric rockets but after they discovered the Van Allen belts they discovered this is much too slow to make it through the magnetosphere.

Re: The Lunacy of Artemis

#495

Post by lucianbr »

thaumasiotes wrote: post #128
dotancohen wrote: post #49

Earlier quoted context omitted.

Even the title is a creative jest, as Lunacy literally means "Looking at the moon" (via "Lunatic" which is someone who looks at the moon - Luna).

> as Lunacy literally means "Looking at the moon" (via "Lunatic" which is someone who looks at the moon Literally? There is no "looking" element in the word. You'd need something like "lunavident". In the most literal terms, lunacy is the noun form of "lunate", which is a shape. ("C" is the "lunate sigma", the sigma in the shape of a moon.) Outside of the shape meaning, "lunacy" is just a relationship to the moon; th…

So "moonness"?

Re: The Lunacy of Artemis

#496

Post by dotnet00 »

alexey-salmin wrote: post #476
tekla wrote: post #429

Earlier quoted context omitted.

Apollo 6 was a partial failure due to engine failure of the 2nd stage. Also they blew up tons of F1 engines during testing. They never got the POGO issues fixed. I really don't understand why people make these arguments. SpaceX is explicitly saying they dont want to spend money proving everything works the first time.

Because in the end the statement that started this whole discussion is still true: we're not there yet, the starship keeps exploding. I have deep respect for SpaceX but what they "explicitly say" doesn't change facts. We may get there eventually, perhaps even with starship, but the fact remains that in 60 years after Apollo we don't have a comparable heavy rocket.

Way to shift the goalposts

Re: The Lunacy of Artemis

#497

Post by alexey-salmin »

dotnet00 wrote: post #496
alexey-salmin wrote: post #476

Earlier quoted context omitted.

Because in the end the statement that started this whole discussion is still true: we're not there yet, the starship keeps exploding. I have deep respect for SpaceX but what they "explicitly say" doesn't change facts. We may get there eventually, perhaps even with starship, but the fact remains that in 60 years after Apollo we don't have a comparable heavy rocket.

Way to shift the goalposts

I don't see how this is the case. We still have neither an F-1 capable engine not a Saturn V capable ticket, both statements are correct.

Re: The Lunacy of Artemis

#498

Post by georgeecollins »

GartzenDeHaes wrote: post #464
twothreeone wrote: post #424

Earlier quoted context omitted.

That's not on congress though. If a budget for the agency only comes with those kinds of political strings attached, the right thing for the agency would be to say "please keep your money, the US won't be going to Moon or Mars".

Congress dictates what executive branch agencies do, not the other way around.

I think what you mean to say is congress approves the appointment of officials nominated by the executive branch and approves the budget for agencies. Agencies have no control over congress. The executive branch can dictate what an agency can do, within the boundaries of a law originally passed by the congress (though almost never a recent congress).

Re: The Lunacy of Artemis

#499

Post by gnarbarian »

rbanffy wrote: post #485
gnarbarian wrote: post #483

Earlier quoted context omitted.

we have the opposite problem in government

Government isn’t meant to be efficient. It’s meant to be strategic and to do both the fundamentals everyone needs access to and the things private enterprise won’t do because they are not profitable yet.

come work here for 20 years and tell me how you feel about it after.

Re: The Lunacy of Artemis

#500

Post by pfdietz »

thisaccount546 wrote: post #418
pfdietz wrote: post #412

Earlier quoted context omitted.

For human spaceflight to be ruled out, automation has to be superior for every worthwhile application of human labor in space, not just some of them. Here on Earth, automation is predicted to increase, but few are predicting it makes human labor useless. I think greatly advanced automation would improve the argument for humans in space, not refute it, by making it easier to support humans in space.

For all of the things we want to do, automation outperforms humans in space. I pointed this out in my earlier post - this wasn’t the case in the 50’s and early 60’s, so these satellites were planned to be manned (and actually were in the USSR’s case). But automation made much more sense, so the plans changed to unmanned satellites. Perhaps this could change in the future. But at least in the present, unmanned makes m…

Really? Automation outperforms astronauts for (say) Hubble Telescope Repair? Or for that matter for doing maintenace on robots?

Your assertion only makes sense if the set of activities we do in space is sharply circumscribed. It's a mindset that comes from the "space is extremely expensive" environment.

Post reply on HN