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Comment by ginkgotree | Hacker News Reader

I live on the Space Coast (also work in the industry, and thus, have access to well - rumors). The SLS (Senate Launch System as we call it here) was pretty cool to watch in person for the uncrewed mission. Nevertheless, as Destin pointed out, it has some massive challenges and headwinds NASA and contractors are cemented in and must accept the SLS is the selected system we are going with. Rumor (please take it for what that is worth - rumors) are, many here are very suspect of even a 2025 crewed flight.

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At what point do we seriously consider the idea that Starship will lap SLS in capabilities and timing, and cancel SLS altogether? I feel like everyone's thinking this, but there's too much pork pressure and sunk cost fallacy to finally just ditch what's turning out to be a misguided approach, nearly 20 years in.

It's a platform built of new stock but very old SSMEs, still using hydrogen and all the problems that brings with it, on a non-reusable basis, with apparently varying quality even amongst identically specced but different vendored mission critical parts. The litany of issues they're outlining here are all varying stages of terrifying, and things that shouldn't be getting caught in this validation phase of a rocket that's actually already had a successful-ish launch demonstration.

Meanwhile, Starship keeps iterating like crazy, the way SpaceX does, and with significantly reduced relative complexity, on a vertically integrated platform that they have much more control over. I'm no Elon fanboy, but Starship is going to win this race, right?

SLS can't even beat F9/FH, never mind Starship. It has already lost.

The SLS delivered a crew capable Space Vehicle to Lunar orbit, and the space vehicle returned a crew capable capsule back the Earth. The lift capacity of FH is not capable of that. This is all about SWaP: Size, Weight, and Power.

The idea that all the components have to go up on a single launcher is nonsense used to justify SLS. It's political engineering, not rational mission design.

I don't think a Falcon Heavy would retain enough fuel once getting itself in orbit with 0 payload to give enough delta-V to the entire Artemis Space vehicle. That burn has to (generally) happen in a single TLI burn. So there is actually a minimum quanta of delta-V for the mission I don't think FH could meet. You're welcome to run this in Orbital STK if you like.

Propellant transfer. There's a reason Senator Shelby was so adamant NASA not work on it -- it greatly reduces any need for a launch vehicle as large as SLS.

Specifically it completely eliminates the need for a non-reusable launch vehicle as large as SLS.

Granted that this is true, FH right now does not have these capabilities and SLS has already done it. For all the amazing success of FH it's completely the wrong vehicle for a mission like this, which is why Starship exists and IMHO is the future.

The point is the mission was designed to prop up SLS, not designed to actually be worth doing. A base on the moon could be supported with FH, and much more cheaply than one supported by SLS.

Starship is _required_ as part of the TLI trjaectory to refuel SLS with cryos. NASA will keep flying SLS however, to demonstrate to the public and congress that it was not setting a pile of tax dollars on fire. LH2 as a fuel was a mistake, high ISP, but well, the turbopumps, plumbing, valves, etc, not to mention REFUELING LH2 ON ORBIT to replenish evap. Starship imho will lapse SLS in the next year or two. From a perspective of demonstrated spaceflight capabilities per unit cost, it will lapse it the first time Starship makes an uncrewed flight around the moon and re-enters a capsule that is recoverable with a human survivable water or land landing. Key qualifier there is per unit cost. Point is, Starship lapses SLS once it matches demonstrated spacelfight capabilities on sheer demoninator of cost.

I'm pretty sure you mean "Starship will lap SLS" and not "lapse", which would inverse the meaning of what you wrote.

Yep, I do

The problem is convincing Congress to pull the plug on SLS. Even if Starship is able to unambiguously surpass SLS technically, lobbying Congress to cancel a program that spreads manufacturing work across most of the US and that involves multiple big defense contractors [1] is going to be a tough sell.

[1] Boeing for the core stage and integration, Lockheed Martin for Orion, Northrop Grumman for the SRBs, and Aerojet Rocketdyne for the SSMEs.

> lobbying Congress to cancel a program that spreads manufacturing

It's not lobbying to cancel a program, it's lobbying to replace a program with another. That other program may bring jobs in the same places; it's actually quite convenient to do so, since there are not that many people around with expertise in rocket manufacturing.

Given SpaceX's heavy use of vertical integration, I highly doubt that it'll spread as many jobs around as SLS currently does.

It’s not going to be 100% replacement, but it could be 50%. And Musk’s lobby machine could find some more extra sweateners here and there. Or you think only Boeing and Lockheed have lobbyists?

The way this often happens with government programs is that one program has to demonstrably deliver the goods before their competitors lose funding. SLS thus far has done better at this than starship. They do this with a lot of military and military-adjacent contracting - they have multiple companies develop a capability, and then theoretically get some choice about which one to buy from as well as having some strategic redundancy.

In many ways, NASA and others have de-risked their heavy lift capabilities by putting together at least two sources. Artemis has sole-source contracts to both SLS and Starship for separate things, but the program is creating two separate heavy-lift vehicles.

Starship has to innovate its way into orbit first (the most recent flight got the altitude for LEO, but not the velocity) and then around the moon to catch up to where the SLS program is today. As far as I can tell, many space folks outside of SpaceX actually have more concerns about whether Starship can deliver on its promises than whether SLS can.

"First rule of government spending: why buy one when you can buy two for twice the price" - Fictional billionaire R.L. Hadden, in Carl Sagan's "Contact"

> the most recent flight got the altitude for LEO, but not the velocity

Starhship could easily have reached true orbit, they deliberately stopped just before it for safety reasons (don't want massive chunk of space junk if something goes wrong during deorbit)

Is that their line? Musk companies have used that excuse a lot when they actually can't do something (see Tesla FSD). During the test flight, they called that orbital insertion was complete after they ran out of fuel (long before reaching orbital velocity), so I'm not buying it.

Also, at that altitude, there's enough drag that you can de-orbit a big metal can pretty easily by simply pointing it in a high-drag orientation. Most LEO satellites do this when their missions are over, and it takes a couple weeks.

Are we talking about the same test flight? They did not "run out of fuel" on IFT 3, maybe you are confusing with IFT 2 from last November?

Yes. "Starship engine cutoff" was called at 26,600 kph at 155 km altitude, when the fuel gauges for both LOX and CH4 on the stream were at 0. That altitude needs 28,000 kph for orbital velocity.

A sister comment mentioned "venting excess fuel," which I don't believe was in the flight plan, but I would believe that the craft was leaking fuel given the clouds of gas around the thing on all the camera views (and the excess rotation in flight). That would explain how starship failed to make orbital velocity and still ran out of fuel.

Presumably, if there was a leak and they fixed it, there wouldn't be any problems getting to orbit. But the fact of the matter is that they didn't reach orbit despite trying (getting into LEO was in the published plan), and the fuel gauges got to 0 before they got there.

It's very possible that the valve between the tanks for the in-flight fuel transfer test (which didn't seem to happen successfully) was broken, so it's not actually a problem with starship at all, but a problem with the experimental setup.

They were venting excess fuel for some time after final trajectory insertion. There's no real question they could have achieved orbit handily.

The only goods SLS has actually delivered are dollars to Boing execs and inefficient jobs across the country.

Most of the satellites the first launch carried did not work, it can't launch often enough to be a viable general use heavy lift launcher, it costs too much to launch, it's such a rough ride that scientific probes would rather take a few years longer to reach their destination on a smoother ride like Falcon Heavy. It can launch Orion but that's meaningless since Orion can't do anything on its own, and as mentioned earlier, it can't launch often enough to lift a second vehicle for Orion to work with.

It depends how you look at it. The mission calls for both systems. Making success reliant on two completely different heavy lift vehicles simultaneously, in which the mission fails if either fails, is arguably not de-risking.

Yes if only one succeeds the US will still have one heavy lift system, but that would require massive re-vamping of NASA's planned mission goals.

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