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The Lunacy of Artemis

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Re: The Lunacy of Artemis

#381

Post by Zigurd »

imiric wrote: post #176
bayindirh wrote: post #158

Earlier quoted context omitted.

From my understanding, nobody is telling that "We should use Apollo as-is", but "why don't we use the same spirit when we were building these back then?". Everything made/designed in Apollo are no short of marvels. Today we can do much better with lighter, smaller electronics, and should be able to do weight savings or at least cost savings where it matters. Instead Artemis feels like "let's dig the parts pile and pu…

> From my understanding, nobody is telling that "We should use Apollo as-is", but "why don't we use the same spirit when we were building these back then?". The political climate in the 1960s was far more tense than it is today, which fueled the space race in ways that forced both sides to give their absolute best efforts to move space exploration forward. While arguably today there are comparable tensions, countries…

There is a space race now, between the US and China. It is tempered by China being only a non-NATO regional security threat, especially in the form of forcibly uniting Taiwan with the PRC. The modern space race is one branch of a many-faceted technological rivalry. So it doesn't have to make business sense or scientific sense in any strict way. But it also can't consume a large fraction of the GDP, or blow up a crew if that can be avoided.

Re: The Lunacy of Artemis

#382

Post by Qworg »

exe34 wrote: post #373
imglorp wrote: post #371

Earlier quoted context omitted.

Yeah, a 9 meter diameter one, which adds mass and volume and complexity and detracts from the payload. Instead what they do is use thrust to accelerate the whole vehicle a little, which presses all the liquid into one end of its tank where it can be pumped out. Instead of carrying special settling thrusters, they originally planned to use ullage gas for this but it's not clear that can work. deeper discussion with ma…

plastic balloon?

Something much like this is used for wells - both simple and effective. I wonder why it wouldn't work here (or if just hasn't been tried).

Re: The Lunacy of Artemis

#383

Post by tyjo99 »

exe34 wrote: post #373
imglorp wrote: post #371

Earlier quoted context omitted.

Yeah, a 9 meter diameter one, which adds mass and volume and complexity and detracts from the payload. Instead what they do is use thrust to accelerate the whole vehicle a little, which presses all the liquid into one end of its tank where it can be pumped out. Instead of carrying special settling thrusters, they originally planned to use ullage gas for this but it's not clear that can work. deeper discussion with ma…

plastic balloon?

Most plastics are very brittle at the cryogenic temperatures. Also if you are using that method for a liquid oxygen tank, you need to make sure that the plastic you choose doesn't spontaneously combust on contact with LOX.

Re: The Lunacy of Artemis

#384

Post by dotancohen »

iamthirsty wrote: post #302
idlewords wrote: post #105

Earlier quoted context omitted.

It's true for the post-Challenger Shuttle, which really didn't have a credible job to perform except for ISS assembly.

Again, the Challenger disaster was 12 years prior to the launch of the first ISS module. ISS missions only flew 37 times, out of 135 total missions for the Shuttle. The Shuttle had many other uses outside the ISS.

I first heard the saying I think sometime around the loss of Colombia. Maybe before, maybe after. By the return to flight, it was most certainly more true than false. By that time the shuttles performed very few non-ISS flights. I think that Atlantis flew a service mission to Hubble, other than that I can't think of any other shuttle flights that didn't go to the space station.

Columbia was heavier than the other orbiters, so she was flying the non-ISS missions from about '98 until her demise. After that US satellites were launched on disposable, unmanned rockets like the Deltas and Atlas.

Re: The Lunacy of Artemis

#385

Post by imglorp »

exe34 wrote: post #373
imglorp wrote: post #371

Earlier quoted context omitted.

Yeah, a 9 meter diameter one, which adds mass and volume and complexity and detracts from the payload. Instead what they do is use thrust to accelerate the whole vehicle a little, which presses all the liquid into one end of its tank where it can be pumped out. Instead of carrying special settling thrusters, they originally planned to use ullage gas for this but it's not clear that can work. deeper discussion with ma…

plastic balloon?

Yes and they would be called bladders, but then you need to carry a gas to compress the bladder.

Re: The Lunacy of Artemis

#386

Post by pfdietz »

usrbinbash wrote: post #322
pfdietz wrote: post #318

Earlier quoted context omitted.

> It doesn't matter how cheap a launch becomes. I have to support an astronaut with food. So, if it were to be as cheap to go into space as to go to St. Louis, sending a person would make no sense because of... food? This makes no sense. Obviously there is some breakpoint at which it would make sense. You can't just handwave and say that universally without doing arithmetic.

> So, if it were to be as cheap to go into space as to go to St. Louis Obviously there is a breakpoint at which the cost differential would no longer matter, I agree. It's just as obvious however, that this breakpoint won't be reached in the near future, or even the forseeable future. It would require a radically new propulsion technology, which, and this is the sad truth, we don't have. The way we launch rockets tod…

Why is it obvious? Starship, if it succeeds, could reduce launch costs per mass by two orders of magnitude over Falcon 9. For the cost of one SLS launch, Starship, if it meets its cost targets, could launch the mass of a nuclear supercarrier into low earth orbit. The cost to LEO would become similar to the cost of transport to the South Pole.

You will notice we are not using robots at the South Pole.

Re: The Lunacy of Artemis

#387

Post by mcswell »

wffurr wrote: post #301
throwawayffffas wrote: post #213

> Conversely, if SpaceX and Blue Origin can’t make cryogenic refueling work, then NASA has no plan B for landing on the moon. If SpaceX and Blue Origin can't. Then Nasa will find someone who can. Cryogenic refueling is the projects real engineering target. Landing on the moon in the twenty twenties just isn't that impressive anymore. The Artemis program is nominally about going to the moon, but it really isn't. It's…

The advanced technologies you're describing are part of Artemis. The other part is a huge pork barrel jobs project for the SLS workforce across the country, in as many states as possible.

It's not called the Senate Launch System (SL) for nothing!

Re: The Lunacy of Artemis

#388

Post by tyjo99 »

Qworg wrote: post #382
exe34 wrote: post #373

Earlier quoted context omitted.

plastic balloon?

Something much like this is used for wells - both simple and effective. I wonder why it wouldn't work here (or if just hasn't been tried).

Cryogenic temperatures make most materials more brittle, hard to get a material that works at a wide enough range of temperatures to make a balloon to work correctly.

If you go for a narrower range of temperatures (ie. not structurally stable above 0C), it would need to be manufactured, transported, stored, tested and installed at seriously low temps which probably negates the possible advantage with the added technical complexity.

Re: The Lunacy of Artemis

#389

Post by jjk166 »

> Articles about Artemis often give the program’s tangled backstory. But I want to talk about Artemis as a technical design, because there’s just so much to drink in.

You can't separate one from the other. Artemis seems like a hodgepodge of mismatched and poorly thought out subprojects cobbled together by people who neither know how to make a rocket fly nor really care if it does because that's exactly what it is.

All the design decisions make perfect sense if you stop looking at the mission as "design the best moon rocket" and start seeing it as "turn these things into a moon rocket," and frankly that NASA engineers could take all the absurd requirements that congress and top level leadership had placed upon them and still found a way to salvage a technically viable system is a testament to their skill.

Re: The Lunacy of Artemis

#390

Post by [deleted] »

throwawayffffas wrote: post #213

> Conversely, if SpaceX and Blue Origin can’t make cryogenic refueling work, then NASA has no plan B for landing on the moon. If SpaceX and Blue Origin can't. Then Nasa will find someone who can. Cryogenic refueling is the projects real engineering target. Landing on the moon in the twenty twenties just isn't that impressive anymore. The Artemis program is nominally about going to the moon, but it really isn't. It's…

[deleted]
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