Eight minute test was aborted after ~1 minute.

https://arstechnica.com/science/2021/01 ... 7-seconds/

Yeah, gimbaling problem. Rockets aren’t easy. Fix and re-test. I’m sure they’ll get it on the next run. These are proven engines, shouldn’t be a big deal.

The whole point about SLS was that it was parts bin rocket, reusing known parts such as engines and boosters based on the shuttle program.

For something that should have been easy and quick, it sure seems difficult and taking a long time.

$18.6B in development so far, will cost more than $2B per launch, entirely disposable. It has been in development 10 years so far.

Mike C.

The whole point about SLS was that it was parts bin rocket, reusing known parts such as engines and boosters based on the shuttle program.

For something that should have been easy and quick, it sure seems difficult and taking a long time.

$18.6B in development so far, will cost more than $2B per launch, entirely disposable. It has been in development 10 years so far.

Part of the program is to develop a cheaper variant of the engine for use when they run out of the existing stock (RS-25E and RS-25F).

My question is if the development of the cheaper version will ever pay back the cost of development versus just keep making the existing engine as designed.

Rocketdyne just got a contract to build 18 RS-25 engines at a cost of $1.8B, that's $100M per engine, $400M per SLS system. It wasn't clear exactly what version that contract is for.

Mike C.

$100M each, it's the IO-720 of rockets

I’ll tell you what will make them less expensive: Don’t throw them away after every flight. This vehicle is at least an order of magnitude more expensive on a per-flight basis than Starship. It’s an incredible waste, and from a cost perspective, it cannot hope to continue long term, which puts the lunar program at risk.

Redneck engineering solution:

Cutting charge on the bottom bulkhead, shear it off from the tank and parachute it back. Tank is relatively cheap vs engines.

Yeah, except the whole shebang would go swimming. I don’t think those motors like salt water.

Won't work. The solid boosters drop off after ~2 minutes, but the core burns for several minutes more, around 6-7 minutes. By that time, the altitude and speed are such that the engine module won't survive reentry without burning up. It would need a heat shield, and that is extra weight.

SpaceX gets around this by having a reentry burn which slows down the booster just before it starts to hit serious amounts of atmosphere. To do that, you need the fuel, which means you need the tank. You have to design in that sort of feature from the start.

SpaceX is optimistic about when the Starship will be ready for use, but I think they will achieve their functional goals. The Starship and Super Heavy booster can't quite lift as much into orbit as the SLS, but it is close, and sending two trips of Starship will be FAR cheaper than one SLS.

Tomorrow at 8:45 ET, SpaceX is scheduled to launch another batch of Starlink satellites. This will be the 8th use of that particular booster on this flight, with a record short turn around time (booster last flew Dec 13th, so just over a month time to get it back on the pad).

Mike C.

yeah the SLS seems to be providing about the expected amount of value for taxpayer money we can expect from government

this should have been simple. tender to the public, lowest bid to lift X KG to the moon

I can’t help but wonder to what degree is this due to ineptitude or a work ethic that doesn’t measure up to last century. Our elite institutions of higher learning don’t seem to be willing to sustain as rigorous a standard in hard science as in the past. Is this curmudgeon syndrome setting in? Maybe.

Hi William,

I don't see that effect in any of the private space companies, only government. And to be fair, that government inefficiency was probably there all through the cold war space race as well, they just threw more and more money at it until the job got done regardless of cost.

That may well be, but they also had a focus, a common goal, and a clean design sheet. SLS is more of a politically motivated congressional debacle used to placate the space crowd while feeding age-old contractors like Boeing for as long as possible. Getting to the moon is just a marketing gimmick that may or may not be sidelined by congress at the turn of whatever administration is coming up that cycle. Their culture and mindset is that of a contractor, not an explorer. They don't, or maybe can't, think outside of their little box the way SpaceX does because their culture is incapable of doing so. The entire SLS is based on the same concept that Von Braun developed in the late 1950s because at that time they didn't have any other way to get into space. In 2011 nobody within that clique ever considered anything different, and even if they had they wouldn't have been allowed to because congress mandated that they use shuttle components in the design.

SLS is the last gasping breath of 20th century spaceflight. Better, and much less expensive designs, based on new innovative thinking have already made it obsolete. We will likely see it fly, but it will inevitably be replaced, probably by Starship, fairly quickly as those alternatives become available.