Author Topic: The fate of SLS after Falcon Heavy debut  (Read 33063 times)

Offline Robotbeat

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Re: The fate of SLS after Falcon Heavy debut
« Reply #200 on: 02/14/2018 03:43 PM »
FH can put 34 tonnes to TMI with one crewed launch, the same mass as SLS. It only requires one additional uncrewed launch, which adds basically no risk to the crew.
The assumption in all of these discussions seems to be that the cost of developing the capability for a LEO rendezvous mission, cryogenic orbital refueling etc., is free.  It certainly is not. 

For example, you forgot to include here the extra two or three or more launches needed to refuel the trans-Mars stage in low earth orbit - assuming all are expendable launches.  If the stages are recovered, count on six or more refueling launches. 

 - Ed Kyle
You're not wrong. However, any Mars mission will need either orbital refueling, orbital assembly/docking, or both.

The other option (vs cryogenic) is storable/hypergolic refueling, which has already been demonstrated.

But I don't think cryogenic refueling is that much harder than hypergolic refueling or orbital assembly that we should avoid its much greater performance and cost advantages just because you can tick a box on a TRL chart right now. SLS can't single-launch a human-class mission to Mars any more than Falcon Heavy.

tl;dr: Any human Mars mission will need in-orbit rendezvous over multiple launches to complete the mission.
« Last Edit: 02/14/2018 03:43 PM by Robotbeat »
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline envy887

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Re: The fate of SLS after Falcon Heavy debut
« Reply #201 on: 02/14/2018 04:31 PM »
None of these rockets can match the capabilities of the SLS. The SLS will go on to complete its crewed missions to Mars in the 2030s while private space companies are stuck at earth. Take it to the bank.

NASA has been saying this since the 1960s. So far they have half a rocket and even less of a cislunar capsule. The truth is they don't have the funding for it, unless they do most of the heavy lifting with commercial vehicles.

Offline TrevorMonty

Re: The fate of SLS after Falcon Heavy debut
« Reply #202 on: 02/14/2018 04:59 PM »
As pontential SLS replacement FH needs to be able to get crew to DSG and back. Havn't seen any detailed plans on how to do that from SLS critics.

I don't think Dragon comes close to Orion to support crew safely BLEO. There is also lack DV to get from TLI to DSG and return.

FH can't deliver Orion to DSG in single launch. Which leaves distributed launch. This requires totally new US which needs 2-4 weeks of operational life while waiting for crew launch. Drop tank which can hold cryogenic fuel for 2-4weeks, rendevous and fuel transfer.  Two FH launches 2-4 weeks apart, big ask for triple core LV.

There is reason NASA went down big LV path instead of DL. I think ULA DL is way to go but the technology hurdles to overcome are not simple by any means.

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