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Stock SLS Parts Overpowered?


MAFman
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The "main engine" for the SLS in KSP has a sea level thrust of 3,746.03 kN

The real SLS uses 4 RS-25 engines, which each have a thrust of ~1.86 MN.   1.86 x 4 = 7.44, or roughly twice that of the KSP part.

There's also a massive ISP difference.  The KSP engine's ISP is abysmal compared to the real thing, likely for balance reasons as a result of KSP using single fuel for all engines, the wet/dry mass ratio of fuel tanks being horrible, and Kerbin being smaller than the actual moon.

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50 minutes ago, MAFman said:

the entire SLS stack

.. doesn't 'make sense' in the context of the stock KSP system. Just like 'the entire Apollo stack' doesn't make sense in stock.

It's not Earth, it's Kerbin; it's not NASA parts, it's whatever Jeb banged together in his scrapyard or found lying beside the road. The fine print warns us not to expect similar results.

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Have you tried building Saturn V with 5m parts? It took us earthlings to the Moon, in KSP you could easily go interplanetary with it. Crewed Mun capable craft start at 2.5m diameter, which are equivalent of Ariane 5-sized rockets.

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No, they're not overpowered. SLS can lift 95t to LEO. If you build something that looks about the same in configuration and relative dimensions (everything in KSP is smaller of course, the S3 parts are only 3.75m in diameter) it will be able to lift about 95t to LKO.

Example:

2x S3-14400 + 1x S3-7200 + Mammoth engine block + 2x Clydesdale (which are larger than SLS SRBs in relative dimensions) with a 95t payload on top will net you 3298 m/s ASL (I added a RC-L01 probe core and 3.75m protective shell, but didn't build the fairing). If you use SRBs that are more similar in relative dimensions to the SLS, you won't even make it to orbit.

Of course they're not close replicas, it's a planet the size of our moon with little green men the size of a bedside cupboard, a replica real world engine would instantly black out your Kerbals from excessive G forces and send them out of the solar system. They're "functional equivalents", not technical replicas.

 

Edited by Beamer
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3 hours ago, Beamer said:

If you build something that looks about the same in configuration and relative dimensions (everything in KSP is smaller of course, the S3 parts are only 3.75m in diameter) it will be able to lift about 95t to LKO.

Ohhhh, so my payloads are just way too small. I was only trying to lift a 15-ton Orion spacecraft thing.

Edited by MAFman
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I just rebuilt one with the Rhino engine as the second stage and two Pollux boosters, and it does make it into orbit theoretically, barely, with a 90 ton payload.

6 minutes ago, MAFman said:

I just rebuilt one with the Rhino engine as the second stage and two Pollux boosters, and it does make it into orbit theoretically, barely, with a 90 ton payload.

...or not

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1 hour ago, MAFman said:

Ohhhh, so my payloads are just way too small. I was only trying to lift a 15-ton Orion spacecraft thing.

For a 15 ton payload you don't need an SLS-sized rocket. For that sort of weight you can go much lighter, even if you want to get that 15t to Mun orbit.

Example:

Stage 1: Twin Boar + Jumbo 64 + FL-A215 adapter

Stage 2: FL-TX1800 + Bobcat

Stage 3: FL-TX1800 + Cheetah + 15t payload

Needs some utility stuff, fairings etc, depending on how much you add you can add 2 SRBs or disposable tanks to the 1st stage and that should get you to Mun orbit quite comfortably. (Note: Bobcat is not a very good engine, but it has the right form factor and thrust for this particular configuration).

The thing about KSP scaling is that although all the rocket parts (tanks & engines) are scaled down in size, the payloads are not. The KSP equivalent of an SLS or Atlas will carry the same weight to LKO as their real world equivalents carry to LEO, even though the rocket itself is some 6 times smaller. That's why KSP rockets tend to look very top heavy and you frequently see people launch stuff in fairings that are larger than the rocket itself. If you build a Kerbin system rocket in stock KSP that is wider at the bottom than at the top, you probably seriously overspecced your rocket.

 

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  • 2 weeks later...
On 9/4/2022 at 3:28 PM, The Aziz said:

Have you tried building Saturn V with 5m parts? It took us earthlings to the Moon, in KSP you could easily go interplanetary with it. Crewed Mun capable craft start at 2.5m diameter, which are equivalent of Ariane 5-sized rockets.

I always land on the Mun the first time with 1.25 meter parts but that is ugly rockets. 

But yes Kerbin orbital velocity is very low. To give 3 examples, an SR-71 fly at roughly half the orbital velocity, the X-15 rocket plane was about able to reach orbit and an Falcon 9 could put second stage and probably an payload into orbit then do an deorbit burn and land. 
KSP parts are heavier and tend to preform worse, but you can put much more into orbit than on earth and the SLS part and more so making history are OP compared the old engines. 

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