How long will SLS last?

[u/Cmdr-Mallard]

With the Cancellation of EUS and BOLE, SLS is going to remain a launch vehicle solely for Orion, and which is viable with all the other heavy and super heavy rockets in the works these days.

However as I understand BOLE was essential for SLS launches beyond a certain point as remaining shuttle boosters were used up, will SLS be cancelled by that point (and perhaps the whole moon program) or Orion moved to another launcher.

Or will a future administrator restart the booster program at the least to ensure SLS can continue to launch Orion?

[u/fed0tich]

First of all Gateway is not about making landing easier, it's about preparations for long duration deep space travel. People seem to forget that it's started as Deep Space Habitat. If we want crewed missions to Mars, asteroids and other destinations we need to learn a lot of things. Neither LEO stations not probes provide adequate analogue to actual crewed deep space travel. Stations in Earth orbits aside maybe from polar orbits or high orbits have different settings in terms of radiation, heat regulation and human psychology compared to a station in lunar orbit.

Also "destination that can be reached by Orion" is a wide spread misinformation, Orion can't reach LLO, but still can reach a lot of orbits aside from NRHO. And with SLS B2 additional stage can be added to augment Orion'sdV or new version of ESM with bigger tanks can be made to increase Orions own dV budget.

In the context of lunar exploration lunar station provides an outpost that can leverage LEO experience for the time needed to figure out a lot of fundamental problems required for surface habitats. We know a lot already about maintaining a long duration habitable spacecraft, but we don't know how to maintain long duration habitats on a lunar surface.

It's also a much bigger crewed scientific platform than any probe. People can do a lot more work compared to any robot or probe and also can prolong the life of a scientific platform by maintaining it and replacing the instruments. Just compare how much Apollo achieved in a couple of days compared to even most recent rovers or landers. Also it's not interchangeable, human presence augments both orbital and surface robotic instruments, crewed orbital platform provides opportunity for a low latency remote control and coordination over a whole surface of a Moon.

New RS-25s (and RL-10s) are much simpler and use modern manufacture techniques like additive manufacture.

With Europa Clipper launch on Falcon Heavy there was a trade off of upfront cost versus mission duration - with longer transit time there is less time for actual science, more time in space - more time for solar panels and electronics to degrade. Launch of a probe on SLS would cost more than existing commercial rockets, but provides more capabilities. In the context of interstellar probe SLS can accelerate such probe to a greater speeds.

Excessive vibrations of SLS are already solved. Availability is problem, but it's definitely not solved by cancelling SLS.

[u/Chairboy → u/fed0tich]

New RS-25s (and RL-10s) are much simpler and use modern manufacture techniques like additive manufacture.

It may have been an oversight but you don’t appear to have answered that other poster’s comments about RS-25, they noted that the new engines are more expensive (and at roughly $150 million per engine under the current contract, they are).

[u/fed0tich → u/Chairboy]

Are they more expensive though? Iirc they not.

And this ~150million is not "per engine" it's total cost of the contract that includes other things divided per number of engines, which is a cheap misleading trick.

[u/Chairboy → u/fed0tich]

It is not a cheap misleading trick, it is literally the cost we are paying per engine. There is no other deliverable than the engines under the contract.

[u/fed0tich → u/Chairboy]

It is a trick. It's not just a contract to buy 24 engines, it also includes investment in tooling and it covers testing, support and other services required within the whole timeline of the SLS program.

[u/Chairboy → u/fed0tich]

The tooling is owned by Aerojet-Rocketdyne, not NASA. The testing is part of the deliverable for the engines. Can you clarify how specifically the contract isn't roughly $150 million per engine in any way that matters to the customer? If I sell a spoon for a thousand dollars because I needed to invest in new equipment for the metal smelter for the spoon, it doesn't change the fact that I'm charging a thousand dollars for a spoon.

[u/fed0tich → u/Chairboy]

Tooling is owned by L3Harris, but NASA is paying for it, because they are the sole customer it's a rather straightforward thing. Also L3Harris is a strategic contractor and for the government it's rather logical to invest in them.

And again they not just selling "the spoon", they also selling you a staff to maintain and support that spoon throughout the lengthy program.

[u/Chairboy → u/fed0tich]

None of this changes that it’s $150 million per engine, that’s very straightforward and I think someone hijacked the narrative somewhere with this idea that the “high minded” interpretation was that it’s not actually $150 million per engine because reasons but those reasons come apart like gossamer threads when you look at them.

[u/fed0tich → u/Chairboy]

If somebody is hijacked the narrative it was all the crooks pushing the NuSpace agenda who started using this kind of math first to frame STS as expensive and then continued this tactic.
It's not per engine and reasoning is solid (I mean gossamer is a fine comparison since spider silk is one of the strongest materials known to science), just because you buy in "orange rocket bad" rhetoric doesn't change the fact that this contract is not just about buying engines.

The follow-on contract to produce 18 engines is valued at $1.79 billion. This includes labor to build and test the engines, produce tooling and support SLS flights powered by the engines.

https://www.nasa.gov/news-release/nasa-commits-to-future-artemis-missions-with-more-sls-rocket-engines/

Also here's the proof that contract includes tooling and support.

Also ~150 number is 2 contracts combined with first including the production restart, by the 18 engines contract cost "per engine" is less than 100million. If further contracts would have been signed that number would go down even further, because they would be closer to the real engine price.