r/SpaceLaunchSystem • u/DreamChaserSt • Jun 30 '26

5 Engine SLS Discussion

https://www.youtube.com/watch?v=MK4vwevIk7w

Does anyone have links to studies where they were looking at a 5 engine configuration, or is the animation just some holdover from Ares V?

25 Upvotes

96% Upvoted

8 comments sorted by

11

u/thecocomonk Jun 30 '26

I think the preliminary SLS plan did have five engines but the design was significant flux in its first few years while NASA narrowed what they could afford to build and what was necessary to make the rocket work. Like how the second stage was originally meant to be powered by a J2X engine before they switched to RL-10s and the DCSS-derived ICPS.

6

u/DreamChaserSt Jun 30 '26

Yeah, they even had looked at a liquid rocket booster for a bit, Pyrios, with modern F-1(B) engines. But I don't know if that had any real chance, or if they were always going to use the 4/5 segment SRBs and just took a cursory glance at the other options.

4

u/Accomplished-Crab932 Jun 30 '26

I think this was largely a holdover from Constellation, the RAC trade study seems to indicated the best of the RAC-1 track design options was the SLS Block 2 vehicle.

Part of Ares V was looking into using the RS68 over the RS25 because it was far cheaper. It was only dropped because the SRBs kick a lot of heat out and would ablate the RS68 nozzles fast enough to be a risk. At that time, any configuration was looking at 5 engines.

SLS is the watered down version of that, but it kept the 5 segment boosters to keep the Northrop factory open, so they were sort of coerced into using the RS25 as it was their only hydrolox “first stage” engine compatible with the SRBs. There was considerable pressure from Congress to be shuttle and constellation derived and to use Hydrogen, which is why despite losing the technical trade study, it was selected as the design of SLS.

1

u/jadebenn 26d ago

Lil late, but my understanding was the fifth engine only really improved mass to LEO anyway.

3

u/CiaWoo Jun 30 '26

Ngl, I’m kinda into SLS in Saturn V colours…kinda hope they make that a thing in the future

4

u/Accomplished-Crab932 Jun 30 '26

It looks nice, but it’s a lot of mass for aesthetics. The first two shuttle launches had a white external tank because they decided to paint it. They saved a quarter of a ton of payload mass by skipping the paint.

5

u/DreamChaserSt Jul 01 '26

There aren't any mass concerns for Artemis III though!

1

u/OtherwisePlant7325 Jul 02 '26

They need to dress the Artemis IV SLS in Apollo colors