Comment by tsimionescu
2 days ago
I agree that SLS is not an efficient project by any stretch of the imagination, and they have their own problems. I don't really see a reason to believe that Starship will ever achieve the goals that were declared for it. In particular, their plan for how to achieve the Moon mission, requiring an unclear number of missions to fuel a single flight in orbit.
Starship is irrelevant. SLS was dumb already in 2011 when Starship doesn't exist. Its a dumb system and was never the right system. NASA own analysis showed that.
People who defend SLS on the bases that Starship isn't good don't get it. It doesn't matter if Starship exists. SLS should have been canceled even if you assume the state of the rocket industry in 2015.
Anybody with half a brain and 3h time to do analysis on the topic could figure this out.
It's a total jobs program. I don't know what Starship will be, but at least Starship is trying to do something new and potentially very valuable. Maybe it is too ambitious but SLS is not that ambitious and not that successful :(
The only reason NOT to cancel SLS outright is "we can't get anything better". "Sure, it's pretty dumb, but it can be built, and good luck getting anything better built."
Starship is important because the closer Starship gets to coming online the more obviously wrong that line of thought is.
As is, Starship, with its first stage being online and reusable already says "we could have done something like SLS much cheaper if we were smart about it". When the second stage comes fully online, the argument for SLS will diminish further.
This not actually a good reason. First of all, of course you can't get anything better if you never ask for anything better or consider alternatives or put any money into anything better.
If you never invested in anything else, then the M4 Sherman tank would still be the best tank. And then you could say 'we can't get anything better' and continue to use it while refusing to ever even put 1$ into developing anything else.
And actually there are plenty of ways, even without Starship to do these things differently.
I remember when SLS fans in 2016 told me that SLS is real and Falcon Heavy is fake. Even when Falcon Heavy and now New Gleen can do most things SLS can.
One NASA Administer was almost fired for exploring if Orion could launch on Falcon Heavy.
The thing is NASA is not looking for alternatives, and it doesn't matter if Starship is fully proven and operational. People will still say its not the same, because Starship will need refuel and isn't direct.
You can always find a reason to justify one solution if you only ever consider that solution and refuse to even look at any other possibility.
> I don't really see a reason to believe that Starship will ever achieve the goals that were declared for it.
If you consider declared goals for Starship to be too hard (I assume not impossible), what aspect makes them that hard?
And since we talk about the Moon here, not stated goals of using Starships for Mars flights - what part of the Starship design makes it hard to believe that Starships may in next few years be regularly used for flights to the Moon?
I'm curious what it is which makes it so hard to believe.
For me its the commodities.
I grant that SpaceX engineers are smart people and can figure out how to make Starship and Superheavy reliable and reusable.
But if they have to launch 10-14 times in order to get the propellant to the LEO depot in order to fuel the Lunar Starship, can we actually deliver that many launches worth of LOX and LNG to the launch pads in the timeframe needed to prevent it all from boiling off once in orbit before Lunar Starship can get there, get refueled and head to the moon? I don't know the answer to that, and to me that seems like the hard problem.
When Korolyov worked on N-1 rocket in 1960-s, some plans included building a hydrogen upper stage. http://astronautix.com/n/n1blocksr.html Hydrogen is rather hard to keep cold, but that stage was designed to work for over 11 days.
Falcon-9 flies almost every other day, about 3 times per week. Methane is way more storable than hydrogen. Of course we'd like to compare numbers, but, given that Starship is way bigger than than N-1 stage - about 15 times, and there is the law of squares-cubes, which for our case says the bigger the tank the less percent of boiloff per unit of time, and it's methane, and we can afford to lose a little and top off with another tanker...
Now, how many tanker flights we'll need? That's a favorite riddle in Musk's plans :) . Korolyov, again, had some early ideas for 5 tankers - https://graphicsnickstevens.substack.com/p/sever-the-bridge-... ... For Starship - if you have 1500 tons of fuel in the Starship, and 150 tons of payload in a tanker, you need 10 flights. You can probably optimize, or be disadvantaged by some obstacles - so, 8-12 flights? That many can fly in less than a month. We can also use additional measures to reduce boiloff - better protection from the Sun, active cooling, maybe more permanent orbital refueling depot - but still, with our today's Falcon-9 flight rate we may consider one Starship per month refueled on LEO. Even if some refueling flights won't be successful, the replacements could be sent.
I personally suspect Starship will fly much more often than Falcon-9. We're so much better in rendezvous and docking these day than we were during Apollo flights, the reliability is so much higher - just take a look how many Falcon-9 flights in a row are successful - so I don't think operationally LEO refuelling will present a significant problem. And I'm sure we need maybe a couple of years to see first examples of that.
Space is hard, yes. But we're getting better, for sure.
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SpaceX is the undisputed king of launch cadence. Falcon 9 just flies every other day nowadays.
If anyone can take "we need 14 launches per mission" and make it work, it's SpaceX.
Boil off isn't somehow unsolvable. We know cryogenics can work in space, and SpaceX's approach is actually less aggressive than Blue Origin's requirement of zero boil off on LH2.
> But if they have to launch 10-14 times in order to get the propellant to the LEO depot in order to fuel the Lunar Starship, can we actually deliver that many launches worth of LOX and LNG to the launch pads in the timeframe needed
If only Starbase was located somewhere near abundant gas pipelines, within spitting distance of of the Texas Shale Oil boom…
All of SapaceX rockets waste close to half their payload capacity on extra fuel for landing, extra equipment for landing, and they still have a 100% failure rate on every super-heavy launch they've ever attempted. SpaceX has blown up more rockets in the last year than NASA has in its entire history. NASA's super heavy rockets have been working successfully since 1967. NASA did build the first single-stage-to-orbit rockets that also successfully landed, but it immediately realized that was a huge waste of resources. Instead, they put parachutes on rockets and then refurbished them instead. So NASA gets double the payload capacity for free. The boosters currently strapped to the SLS that's about to go to the Moon are the same ones that previously took space shuttles to orbit in the 90s. NASA has been to the Moon and Mars; SpaceX has never made it to either, and just last week Elon said they've officially given up on going to Mars, and they're hoping to make it to Moon in another decade instead. NASA is going next month. SpaceX is just vaporware being run by a drug addict whose only goal is to sell it to the public markets before the house of cards comes down.
It would be great to have some actual numbers. How did reuse work out for Falcon 9? How much does the reused boosters for SLS cost? What's the cost and performance of an expendable Starship vs SLS?
> SpaceX has blown up more rockets in the last year than NASA has in its entire history.
SpaceX's number of successful launches last year exceeded the total number of launches by all other U.S. agencies over the past decade.
They’ve already caught and reused a Super Heavy and had multiple successful soft landings in water with Starship.
Going to Mars takes about the same delta-v as the moon.
SpaceX launches 80% of the world's mass to orbit, they probably know what they're doing.
Starship is an extremely hard problem, and their aim is to reduce cost of getting mass to orbit by another 10x after Falcon 9 did the same.
Falcon 9 needs about 4% of fuel to land on a ship, 14% to return to launchpad
Why would you say they've had 100% failure rate? What did you think the reason was to launch and how did it fail?
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Even if Starship completely fails, SLS is a pointless and ludicrously expensive dead end. Terminating it is the only logical thing to do.
The whole moon thing is a pointless and ludicrously expensive dead end. But if one wants to do it, one should choose between the working approaches.
Orion is actually pointless, I don't understand why the mission goals are valuable. Partial success would be meaningless. Success is meaningless.
Starship in contrast has a variety of meaningful objectives. Even if Starship only achieves proving that cryogenic fuel transfer in LEO is possible that's a valuable mission goal in and of itself.
If you really think "the whole moon thing is pointless" NASA is pointless.
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Might as well get some ROI out of it though.
IMO the Blue Origin hate was overhyped. They're clearly the only ones who know what they're doing. NASA and SpaceX both are way in over their heads.
The Blue Origin skepticism is based in how many decades they spent in making buildings instead of rockets and how long it has taken them to get anything to orbit.
The Blue Origin hate is mostly how opaque the program is compared to SpaceX.
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Is it clear how many SLS launches would be needed to subsume Starship's part of the mission?
It doesn’t matter because SLS can’t launch but once a year if lucky. And so far they have never even approached that.
You don't have long to wait to see an obvious reason, the first v3 starship is in preflight testing right now.
And do you think the this next launch will deploy actual satellites in orbit around the Moon? If not, I still don't see why you'd compare it to SLS's current success. Or do you think this will deploy 100 tons to orbit for less than $10/ton, or fly to Mars, since these are the stated goals for Starship?
Do you think perhaps you should give SpaceX as much time as NASA has had for SLS to fail at its goals before complaining that SpaceX’s system in testing isn’t accomplishing all of its goals?
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