@PearsonArtPhoto - but this is a good start. Humanity will run out of certain metals on Earth by the end of the century. Asteroid Mining is the only option. They cannot mine Earth's core.
What seems better to me is to use the asteroids to make a larger space station. One can do the manufacturing on orbit and return stuff that is worth returning.
@ErinAnne I LOVE IT! @AndersSandber has great answers in many SE's including Space, but this is the first time I've seen an SE to arXiv migration path for answer!
It demonstrates to me that Physics SE is too big! and so much good stuff falls through the cracks and good people get discouraged and leave.
@PearsonArtPhoto sounds like the basis of a new question post; very roughly: "Which 'engine dumping' is a greater loss of time and money, an SLS test or Starship test" or something like that.
My gut falls on the side that the RS-25 engines are the bigger money/time sink, either way. 4x RS-25 vs 39x Raptor … seems like 10x is indeed the inflection point
anything you have to precisely engineer, then build a factory for, then also manufacture to tight tolerances, then document obsessively is going to cost a lot. It won't help if that's only spread over 50-60 units over...gosh, basically as many years isn't it
> The United States, Japan, Canada, and the participating countries of ESA (European Space Agency) have confirmed they will support continued space station operations through 2030 and Russia has confirmed it will support continued station operations through 2028.
@ErinAnne while I've always eschewed social media (SE is my only online "hangout" and I still mostly avoid chat rooms) mastadon might finally pique me enough to look further. Now I may need to find a "How to Mastadon" video for non-social-savvy folks...
@uhoh I am personally very pro-Mastodon, despite many faults that it has. If you want to talk about it at all feel free to fire up a side chat with me, but fedi.tips is a very good start
you might also be interested to know that Mathstodon.xyz has LaTeX support in its web interface. here i will end what could otherwise easily be a wall of text from me
@TheMatrixEquation-balance including re-starting the production lines; $100m per engine not counting that (if they were to continue flying SLS, that's what the engines would average out to), which I think more accurately compares to the per-Raptor production cost
@ErinAnne Worth mentioning that a Raptor is expected to be in the single digit millions cost or lower. The latest order for SSME's is basically 100+ million an engine. So 33 million vs 400 million thrown away also adds perspective.
@PearsonArtPhoto To be fair, that is start up production costs, and spit out 8 engines, divided by 8 costs... In THEORY engine 9-16 should be less costly. But this is NASA, so maybe not...
@geoffc right now I’d go with about $78m vs $400m to be conservative (have heard $2m/Raptor and $100m/RS-25 not counting startup costs). So in terms of engine costs, can do at least 5 all-in Starship launches per SLS (assuming they don’t manage to drop the cost of Raptor production)
@fyrepenguin - There is a big difference. With Raptor engine development, you are paying for innovation and promise for the future. With RS-25, you don't really know what you are paying for.
@fyrepenguin And since they have so far built close to 200 Raptors in the current produiction line and RS-25E's have not been built in 20-30 years? And currently turning out engines in low number of days per engine, so I expect that cost to drop.
To be a little fair to the RS-25, LOX/Hydrogen is seemingly a gigantic pain in the ass
we may have been blinded by ISP
but the 80s kid in me is still thinking ohhhhhhh could things have been different if we hadn't stopped building Shuttles? Especially if we'd gotten on to some of the proposed modifications
hopefully that's pretty much what we get with Starship though
It is not easy to overcome the inertia of entrenched traditional thinking and bring forward some new engineering concepts. But Matrix sent us a remarkable bulldozer, Elon Musk, to do the job.
@ErinAnne having read Ignition! ….. yeah, probably. ISP > safety/ease of use. Which I guess makes sense for bespoke, high-performance systems, less so for proliferating commercial space flight
"As of March 2023, no methane-fueled rocket has reached orbit" - why didn't they think about Methane earlier? Did liquid methane/LOX engines require new inventions in rocket engine engineering?
When it was the first time the liquid methane was used in a rocket engine? I mean for space launches, but it would be interesting to also know about first uses in experimental [rocket] engines, in military, sounding and maybe aircraft.
And why it wasn't used before that?
John D. Clark's famous book Ignition! (1972) - "he main reason why methane has been mostly neglected as a rocket fuel after these early experiments is simply that, with its low boiling point, it's harder to store and handle than more traditional kerosene-based fuels."
@ErinAnne they did a re-print and I picked up a copy. Originals go for wayyyy too much - I think I saw one for $5k or so
@ErinAnne was just gonna say that; prior to going for rapid reusability, it didn’t quite matter as long as it didn’t clog while in operation
No point in dealing with a more annoying fuel for marginal gain, until you suddenly want your engines to still be relatively clean after multiple burns
@ErinAnne I haven’t, but it sounds interesting. I’ve got Sled Driver, which I’d imagine is related as the SR-71 was built by them. Is it available online?
@ErinAnne true, but the STS & SLS programs would probably give some of the mentioned people there conniptions with how much hydrogen they were dealing with (though obviously the state of the art has progressed since the time they were dealing with it)
What’s also fun is that I’ve given a couple people I know a copy of Igintion! and neither are particularly versed or interested in rocketry, but they are organic chemists and recognized a lot of the compounds/chemistry going on in the book
I appreciate that it’s accessible to people of varying knowledge bases
The detailed chemistry was something I somewhat glazed over but for people who know chemistry it’s an interesting part
@TheMatrixEquation-balance Ron also talks about the mass/thrust ratio which is basically the same as that of a Merlin engine, a keralox engine. And sure it’s more thrust to weight than a RS-25 but that engine also has significantly higher ISP. That plus other points in existing answers mean that they don’t seem to have added anything (plus as Erin said, didn’t cite any sources)
@ErinAnne me neither. Apparently an organic chemistry background is useful, from what I’ve seen, though others would also be useful
As in, I’d bet that a site getting a lot of bad questions at some time will be a bit more quick with the downvotes/close votes than when they’re mostly getting good questions
but I think at least 1/3 of those are "Welcome to Space SE! Your question/answer sucks and is getting downvoted to hell currently. Maybe check the help center or look at some of the high-voted stuff, lol"
yeah I think some of the more-traveled people have noted we're at least nicer than some of the other SEs, which I believe
According to NASASpaceFlight:
The Falcon Heavy for this mission — consisting of core B1068, booster B1052, and booster B1053 — will be expended due to the need for all available performance. This results from needing to insert the ViaSat-3 Americas satellite directly into geostationary orbit.
T...
Like, I literally typed in half the question title into google and had the answer
I'm still low-key mad that the balloon question from a month or two ago got no attention
that wasn't hard to answer exactly but it was satisfying to actually get a source document about how something was built and point to it
and I think I got like +3
compared to something like 1500-2000 rep for answering a couple Starship questions this week with what amounted to half-assed dismissals of people's ideas about how things should've been
That probably shouldn't be as frustrating to me as it is--a good technical answer has limited interest, and upvotes usually means a lot of attention which means attention from the front page from people who don't have the same technical background
it's still worth some pride for folks without that background to think "ah, yes, this was helpful/interesting to me, I'll click the arrow"
but I think everybody I've talked to about it gets frustrated the same way
When it was the first time the liquid methane was used in a rocket engine? I mean for space launches, but it would be interesting to also know about first uses in experimental [rocket] engines, in military, sounding and maybe aircraft.
And why it wasn't used before that?
