Shouldn't it put the 120+ tonnes into a low earth orbit, with a short burn by the ICPS to circularize the orbit?
So please help me understand this, because I can't find a straight answer anywhere on the internet.I have never understood how to shuttle could put so much mass into LEO, whereas SLS so little.The shuttle launched 122 tonnes on STS-93, the Chandra launch. I believe this was the heaviest shuttle launch ever.Excluding the OMS burn, the shuttle was nearly in LEO after SRB and main engine exhaustion. Just a little OMS burn was required to circularize the orbit. I understand that the shuttle took the 3 RS-25s to orbit with it. They are 3.5 tonnes each. Lets call it 15 tonnes of of total dead weight dragged to LEO. Plus about 5 tonnes of OMS fuel and deadweight. That means the shuttle put 102 tonnes(including the shuttle) into LEO. If there was no shuttle and just payload, that would be 102 tonnes payload with all the same engines.Now compare this with Block 1. Block 1 has 20% more SRB thrust and total impulse. It has 25% more LOX/LH2 and 25%(well slightly higher with RS-25 improvements) more main engine thrust. By that reasoning shouldn't it be able to put 20-25% more mass into LEO that the shuttle? Like 120+ tonnes?Shouldn't it put the 120+ tonnes into a low earth orbit, with a short burn by the ICPS to circularize the orbit?
Have you included the mass of the ICPS?
So please help me understand this, because I can't find a straight answer anywhere on the internet.I have never understood how to shuttle could put so much mass into LEO, whereas SLS so little.
Quote from: Jim on 02/12/2017 01:26 pmHave you included the mass of the ICPS?But SLS, as originally defined, in the NASA Authorization Act of 2010, SLS was supposed to be able to put 70 tonnes into orbit without any upper stage at all.
Quote from: Proponent on 02/12/2017 02:09 pmQuote from: Jim on 02/12/2017 01:26 pmHave you included the mass of the ICPS?But SLS, as originally defined, in the NASA Authorization Act of 2010, SLS was supposed to be able to put 70 tonnes into orbit without any upper stage at all.But then you carry the whole SLS core to orbit
This might be my brain playing me up but I thought that launch of outsize cargoes to LEO (8-10m diameter & >50t IMLEO) for assembly was always a key capability of the SLS. It's one of the reasons why it was funded.
But that's not entirely true, as others have pointed out.SLS has a much heavier core stage (compared to the ET) and that core stage provides a lot of the delta-V for LEO.With the upper stage it's much better optimized for high-energy missions but it's still good enough to throw 70t or so to LEO. So no problem with that configuration for anyone.But please keep the original question in mind because that's what I'm focusing on, not all the politics and mission and whether-it's-a-good-rocket-or-not stuff others have been discussing here.The original question was: why is the payload so LOW compared to STS if you take the orbiter into account and the answer is twofold: in a single-stage configuration you carry that heavy core stage to orbit and in a two-stage configuration especially with EUS it's optimized for more high-energy orbit than STS was which could barely reach LEO