SLS Upper Stage Dilemma

[fredinno]

So I read something interesting today.

http://www.nasaspaceflight.com/2015/06/nasa-resolve-sls-upper-stage-dilemma/

Apparently, NASA is being told to make a decision on whether to or to not to "human-rate" the Block I SLS, and it's upper stage, the ICPS. The Block I, and it's ICPS is planned for use in Europa Clipper, EM-1, and ARM.

However, NASA's advisory group is recommending that the decision be made not to human-rate the Block I, and use a IB for ARM, as Block I is only planned to be used for humans once, in ARM, before being succeeded by more powerful blocks for crew (human-rating Block I would also cost an extra $150 million). They believe that this money is a waste, and would be better used to hurry the development of the Block IB, NASA's planned "powerhouse" for the future. Additionally, SLS employees themselves would like to have the money and time spent on Block IB, as it would open up further missions beyond EM-1 and EM-2, which is a current concern.

The Block I is not being cancelled, it's ability to be able to hold humans, however, is. The SLS Block I is already beginning it's production for EM-1, meaning that total cancellation will be an extremely hard sell at this point.

Another thing I found interesting is that the Block I/IB will sport advanced SRBs once the current supply of Shuttle boosters are flown out. (Block II will probably have bigger versions of these advanced boosters). It's also been suggested that the Block II SLS be cancelled entirely, leaving only the I/IB, as this would save money, since SLS Block I/IB could provide all the upmass capability needed, and it is much further away to completion (2030) than the other 2 variants (2018-2021)

TL;DR:

SLS Block I will most likely not be human-rated. Block I/IB will continue to be used beyond the Shuttle SRB supply.

[G'th]

Thats....actually fairly reasonable outside of cancelling Block II. (though I can understand why if they're willing to just use the IB)

If we're going to cut costs when it comes to NASA, this is the way to do it I think. Kill a redundant component of the rocket (The man rating) and bam, money saved and we can still space today.

[Kibble]

I support this!

[clivman]

This is a great idea. Congress probably won't support it though and relocate money from CCDev to man-rate the block 1 just to spite NASA

[maccollo]

Thats....actually fairly reasonable outside of cancelling Block II.

But Block 1B with advanced solids IS block 2, or at least that's the impression I got. What else could it be? There will be no J2X upper stage, no 5 SSME core, and no booster competition.

Anyway getting the EUS up and running quickly does mean that the 2021 launch will have to be unmanned, so EM2 will be delayed until 22-23. I don't mind. it's not like SLS has anything else waiting for it, and the article says NASA may use block 2 funding to develop payloads. Ok, so does that mean payload development will begin after 2020? SLS is gonna need all the lead time it could possibly get! If they end up launcing the Europa probe around 2025, they might have until 26-27 to come up with something else to go on this thing. I still have a sliver of hope that it might just work out...

[Kryten]

But Block 1B with advanced solids IS block 2, or at least that's the impression I got. What else could it be? There will be no J2X upper stage, no 5 SSME core, and no booster competition.

The blocks are more to do with performance targets than the actual modifications; Dark Knight doesn't hit the block II performance target (130MT), but does allow enhancement to block I/Ib. That's also why you get the '70 ton' figure being bandied about for block I; that's the mandated performance target, the actual performance should be significantly higher.

[Rune]

Putting the Delta stage on top of that monster of a rocket always seemed quite foolish to me. I mean, put the EUS or something similarly big, and then the ICPS can go on top for, say, a extremely quick Kuiper belt mission.

As to developing the EUS , I'm ok with it, with some reservations. We need deep-space transit stages! But I'm afraid the EUS as it is thought out now is not quite what I have in mind for a really useful new upper stage... it's endurance in space must be low on account of the hydrogen boiling off, and modifying it to be able to be docked with and refueled is probably completely out of the cards at this stage.

But you know, in the crazy climate in NASA these days, it makes a short of twisted sense. If they have to develop the SLS, and use it for something, it's best to shoot for a configuration that makes some limited sense. The problem is that for SLS to make real sense you have to launch it often (a couple of times a year at least), and where is the money for payloads... 150 million saved is a drop in the SLS budget ocean.

What I would really like to see is a storable, dockable and stackable stage capable of being refueled, that can be launched empty on an EELV. That would be revolutionary.

Rune. It would also make a really good case as to why the SLS is a costly diversion on the road out of LEO.

[fredinno]

Putting the Delta stage on top of that monster of a rocket always seemed quite foolish to me. I mean, put the EUS or something similarly big, and then the ICPS can go on top for, say, a extremely quick Kuiper belt mission.

As to developing the EUS , I'm ok with it, with some reservations. We need deep-space transit stages! But I'm afraid the EUS as it is thought out now is not quite what I have in mind for a really useful new upper stage... it's endurance in space must be low on account of the hydrogen boiling off, and modifying it to be able to be docked with and refueled is probably completely out of the cards at this stage.

But you know, in the crazy climate in NASA these days, it makes a short of twisted sense. If they have to develop the SLS, and use it for something, it's best to shoot for a configuration that makes some limited sense. The problem is that for SLS to make real sense you have to launch it often (a couple of times a year at least), and where is the money for payloads... 150 million saved is a drop in the SLS budget ocean.

What I would really like to see is a storable, dockable and stackable stage capable of being refueled, that can be launched empty on an EELV. That would be revolutionary.

Rune. It would also make a really good case as to why the SLS is a costly diversion on the road out of LEO.

Which would also probably require massive amounts of research and infrastructure... costing more money. Even if the SLS was cancelled so that this could occur, I find it difficult to believe we would (in the short term of the next few decades) be going any farther than we would by simply developing a ultra-HLV. Yes, refueling stations are necessary, but I can only see them for satellites in GEO at this point, where replacements are going to be difficult to launch, and space junk lingers for much longer periods of time.

[fredinno]

But Block 1B with advanced solids IS block 2, or at least that's the impression I got. What else could it be? There will be no J2X upper stage, no 5 SSME core, and no booster competition.

Anyway getting the EUS up and running quickly does mean that the 2021 launch will have to be unmanned, so EM2 will be delayed until 22-23. I don't mind. it's not like SLS has anything else waiting for it, and the article says NASA may use block 2 funding to develop payloads. Ok, so does that mean payload development will begin after 2020? SLS is gonna need all the lead time it could possibly get! If they end up launcing the Europa probe around 2025, they might have until 26-27 to come up with something else to go on this thing. I still have a sliver of hope that it might just work out...

The advanced solids are probably smaller to make up for performance targets, since NASA plans to use SLS Block IB so much, and Shuttle Boosters will run out.