Forum designs new rocket to replace the SLS

[tater]

Nothing about SLS has saved money in terms of dev costs. Direct was an idea to leverage existing Shuttle infrastructure, and could have substantially reduced dev cost vs SLS, I think.

The reason total cost matters (to me, anyway) is that there is no payload. If the plan is "build it and they will come," then fixed cost matters far more than for a program with a real goal that sort of internalizes those costs. Every X months without a launch when there is no plan is either wasted, or it ups the final cost of anything actually launched later.

[KAL 9000]

The SLS is an amazing rocket that has great potential. The problem: 

There is no frickin' payload for it!

 The only things lined up for it are EMs 1 and 2 and Europa Clipper.

[Kerbal01]

Constellation program, but with a liquid first stage for ares 1. They had good thinking with the Ares 5, not man rating the heavy lifter

[sevenperforce]

2 hours ago, KAL 9000 said:

The SLS is an amazing rocket that has great potential. The problem: 

There is no frickin' payload for it!

 The only things lined up for it are EMs 1 and 2 and Europa Clipper.

I would much rather spend the SLS money on helping to fund commercial lift vehicles and developing BLEO missions and stages.

2 hours ago, DarthVader said:

Constellation program, but with a liquid first stage for ares 1. They had good thinking with the Ares 5, not man rating the heavy lifter

I agree. Though honestly Ares 1 can be dropped altogether. Let the commercial crew program handle man-rating and stick to getting large payloads into orbit for actual missions.

[DerekL1963]

4 hours ago, Rakaydos said:

SLS is currently demonstrating one of the problems with that approach- namely that if your rocket construction rate is slower than your workforce turnover... every rocket is your first rocket, and you have to go through the learning process and dumb mistakes all over agai each time.

If your flight rate is slower than your turnover rate - every flight is a first flight whether the booster is expendable or reusable.

[_Augustus_]

3 hours ago, KAL 9000 said:

The SLS is an amazing rocket that has great potential. The problem: 

There is no frickin' payload for it!

 The only things lined up for it are EMs 1 and 2 and Europa Clipper.

Not true. The Deep Space Gateway and Deep Space Transport, along with more Orions, are also being proposed. But those could be launched on commercial LVs and then sent to cislunar space with SEP/ACES.

15 minutes ago, sevenperforce said:

I would much rather spend the SLS money on helping to fund commercial lift vehicles and developing BLEO missions and stages

Agreed.

[tater]

SLS is already funded this year, and there is zero talk of not funding it the next. The chances it doesn't fly are pretty much zero. As such a notional "replacement" makes little sense. Given their scheduling issues, EM-1 won't fly till perhaps mid-late 2019, and they now have no slop, any delay cannot be made up, so any missed days push back the launch. There is a good chance that by the time a crew mission occurs, there are other LVs that are starting to be in the same league (NG). Should ITS or New Armstrong ever be built, SLS will certainly look like folly I think. Until such a demonstration I think it continues to be funded, even if it doesn't have payloads.

[sevenperforce]

My preferred SLS replacement:

• Persistent Modular Propulsion System
  • Stretched ACES-derived hydrolox upper stage with a single powerplant derived from the RL10 and spark-based ignition system
  • Solar-based autogenous coolant system for propellant persistence
  • Hydrolox RCS thrusters for independent orbital maneuvering
  • Side-mounted docking system with magnetic structural linkage and propellant transfer capacity
  • Forward docking system for orbital payload coupling
• High Energy Upper Stage (similar to EUS)
  • Uses the same tank and engine as the Persistent Modular Propulsion System
  • No thrusters, coolant system, or docking system
  • Additional thrust structure that allows four engines rather than one
• Core Booster (same as current SLS)
  • Core tank and thrust structure assembled at Michoud
  • Four RS-25s
• Advanced Liquid Parallel Boosters
  • Pyrios-derived kerolox boosters
  • Two F-1B engines per booster

That's all.

Launches either send a full PMPS into orbit to couple with a BLEO payload, or they send very large BLEO payload components into orbit for assembly. Contract with commercial providers for smaller payload components and crew launches. Orion is fine, just launch it unmanned on a Delta IV Heavy or something.

[magnemoe]

4 hours ago, tater said:

Nothing about SLS has saved money in terms of dev costs. Direct was an idea to leverage existing Shuttle infrastructure, and could have substantially reduced dev cost vs SLS, I think.

The reason total cost matters (to me, anyway) is that there is no payload. If the plan is "build it and they will come," then fixed cost matters far more than for a program with a real goal that sort of internalizes those costs. Every X months without a launch when there is no plan is either wasted, or it ups the final cost of anything actually launched later.

Again agree, an commercial supplier can operate on the build it and they will come and gamble on larger satellites, he risk his own money after all. 
NASA and other should build after planned missions, 
And yes I can come up with lots of cool mission: sample return from lots of targets is one, I want to look for ice on Moon as an second but this don't require heavy lift. 
Why are they only building one web telescope, multiple linked would be better, with star-shades. You have done the development, how more would 4 more cost? 

[sevenperforce]

Ran some quick numbers. Replacing the SLS boosters with Pyrios boosters (2 x F-1B, 1,054 tonnes gross launch mass each) and using a 145-tonne second stage powered by four RL10s allows you to put 145 tonnes into a 185x185 km orbit matching the inclination of the ISS, launching from Kennedy. This means the "payload" can be the same size and weight as the second stage, so you have common manufacturing between the tank on the upper stage and the tank on the Persistent Modular Propulsion System.

The PMPS would then be able to notionally place up to 77 tonnes in lunar orbit, or it could send itself to lunar orbit to act as a propellant depot with 45 tonnes of propellant remaining. Multiple PMPSs would be able to dock to each other lengthwise for propellant transfer or for asparagus-staged transfer burns. With that kind of system, you can literally send ANYTHING to ANYWHERE.

Of course, you'd need to devote some funding to actual mission architectures. Establish a lunar base, retrieve an asteroid, head to Mars, that sort of thing.

[sevenperforce]

Was just thinking...

If NASA really is determined to throw their mothballed SSMEs into the Atlantic, there's a particularly efficient way to do it: Super-Atlas.

No parallel boosters. Redesign the four-engine thrust platform to make it open; put a fifth RS-25 at the center. All five engines fire at launch, but the thrust platform with the four RS-25s drops away part of the way through the first-stage burn, leaving the center sustainer engine to run through to MECO. An RS-25-based Super Atlas.

Then, repeat the exact same arrangement with the RL-10s on the upper stage.

This way, the upper stage finishes with just a single engine, meaning it can be its own payload if equipped with the previously-described persistent modular propulsion system components. Or it can fly without those components and merely be used to lift very heavy payloads. 

I'll run some numbers tomorrow but I think it would be pretty badass.    

EDIT: Of course, SRBs or Advanced Liquid Boosters could be used optionally. One really nice thing is that the sub-staging point (dropping the engine ring) can be varied based on payload and ascent profile, whereas traditional serial staging is pretty much noncustomizable. 

EDIT 2: Those familiar with the history of the Saturn program may note the similarity to the S-1D proposal.

EDIT 3 (because apparently I cannae stop editing): In theory, an entire launch family (like Atlas V) could be assembled around the same ET-derived hydrolox single-SSME core. You could have a near-SSTO with two auxiliary engines on the thrust ring (a la Atlas D Mercury), a 4+1 variant (a la Saturn S-1D) with or without a second stage, or various parallel-boosted configurations. 

Edited May 24, 2017 by sevenperforce

[sevenperforce]

Running some numbers to see what an Atlas-configured ET-and-SSME-derived launch family would be able to send to orbit.

Launch TWR is somewhat of an issue; the RS-25s provide 1,860 kN each at sea level, so five of them would have a max takeoff thrust of 948 tonnes thrust. However, the SLS core masses 967 tonnes not including engines. If the RS-25 had its vacuum thrust at launch, a super-Atlas configuration could put 36 tonnes into LEO.

If we up the ante and place six engines on the base (two at the center, four on the skirt), things get a little better. We have 1,138 tonnes thrust to play with, which gives us breathing room.

With four engines on the skirt and two on the core, dropping the skirt when just over 87% of the fuel is expended, you could put 39.6 tonnes into a 185x185 km orbit from the Cape. Launch TWR is 1.11:1.

Probably not possible to put a second stage on this, but parallel boosters would make it quite impressive.

[shynung]

@sevenperforce If launch TWR starts to be an issue, you can always slap a few solid rocket boosters on the side of the core. Or give the 4 skirt-mounted RS-25s their own tanks, mounting them as side boosters instead of main core engines.

[sevenperforce]

7 hours ago, shynung said:

@sevenperforce If launch TWR starts to be an issue, you can always slap a few solid rocket boosters on the side of the core. Or give the 4 skirt-mounted RS-25s their own tanks, mounting them as side boosters instead of main core engines.

Adding tanks for the skirt engines would make TWR worse, not better. But yeah, adding SRBs is one way to fix it.

I could envision four configurations: Core + Skirt, Core + Boosters, Core + Skirt + Boosters, and Core + Skirt + Boosters + Upper Stage.

SRBs are one option, but advanced liquid boosters powered by F-1As is preferable, I think.

[DDE]

On ‎23‎.‎05‎.‎2017 at 10:20 PM, sevenperforce said:

My preferred SLS replacement:

• Persistent Modular Propulsion System
  • Stretched ACES-derived hydrolox upper stage with a single powerplant derived from the RL10 and spark-based ignition system
  • Solar-based autogenous coolant system for propellant persistence
  • Hydrolox RCS thrusters for independent orbital maneuvering
  • Side-mounted docking system with magnetic structural linkage and propellant transfer capacity
  • Forward docking system for orbital payload coupling
• High Energy Upper Stage (similar to EUS)
  • Uses the same tank and engine as the Persistent Modular Propulsion System
  • No thrusters, coolant system, or docking system
  • Additional thrust structure that allows four engines rather than one
• Core Booster (same as current SLS)
  • Core tank and thrust structure assembled at Michoud
  • Four RS-25s
• Advanced Liquid Parallel Boosters
  • Pyrios-derived kerolox boosters
  • Two F-1B engines per booster

That's all.

Launches either send a full PMPS into orbit to couple with a BLEO payload, or they send very large BLEO payload components into orbit for assembly. Contract with commercial providers for smaller payload components and crew launches. Orion is fine, just launch it unmanned on a Delta IV Heavy or something.

...is hydrolox the right propellant combo to tie yourself to? Containing the stuff seems nightmarish compared to methane, it looks like no cooling is enough because the damned thing still diffuses through the holes between the atoms of the tank.

Also, I'll admit I find LEO propellant caches that are replenished by additional missions from Earth, especially with non-reusable tankers, quite dubious.

[tater]

Yeah, while I have no design in mind, I do know that any design I could think of  doesn't include hydrolox on the booster.  

[sevenperforce]

22 minutes ago, DDE said:

...is hydrolox the right propellant combo to tie yourself to? Containing the stuff seems nightmarish compared to methane, it looks like no cooling is enough because the damned thing still diffuses through the holes between the atoms of the tank.

Also, I'll admit I find LEO propellant caches that are replenished by additional missions from Earth, especially with non-reusable tankers, quite dubious.

Admittedly, I was thinking of spending the five billion dollars repurposing the SLS systems rather than coming up with something completely new.

And the goal is not an LEO propellant cache/depot, but a single-use LEO propulsion bus to enable BLEO missions. Want a moon mission? Design the lander and send it up on Falcon Heavy or New Glenn, launch a propulsion bus on SLS, and then send the crew up on Falcon 9. Want a Mars mission? Do the same thing, but use multiple propulsion buses in parallel (thus the need for RCS, propellant transfer tech, and side docking ports). This is the closest thing we can get to going kerbal. If propellant transfer is a nonstarter, that's fine; we'd still want side docking ports to enable parallel coupling for injection burns.

20 minutes ago, tater said:

Yeah, while I have no design in mind, I do know that any design I could think of  doesn't include hydrolox on the booster.  

The only thing hydrolox is really good for is high-energy upper stages for large BLEO missions. So if you are desperate to reuse mothballed SSMEs, it does make a bit of sense to use a modified SLS stack to send up propulsion buses.

59 minutes ago, sevenperforce said:

I could envision four configurations: Core + Skirt, Core + Boosters, Core + Skirt + Boosters, and Core + Skirt + Boosters + Upper Stage.

SRBs are one option, but advanced liquid boosters powered by F-1As is preferable, I think.

The Shuttle SRBs held 498.7 tonnes of propellant each, so the planned five-segment SRBs will hold around 623 tonnes, with a GLOW of 726 tonnes, a vacuum isp of 269 seconds, and an estimated vacuum thrust of 18,176 kN. With this in mind, here are the LEO payloads (185 km x 185 km, Cape launch) for the first three configurations:

• Skirt + Core (see above): 39.6 tonnes, skirt jettisoned at 87.5% fuel expenditure
• Core + SRBs: 88.3 tonnes
• Skirt + Core + SRBs: 100.5 tonnes, skirt jettisoned at 91.5% fuel expenditure

Just imagine what sorts of missions would be possible with the ability to drop a 100-tonne hydrolox propulsion bus into LEO.

Liftoff TWR for the skirt+core+SRB stack is 1.8, so we could add an upper stage easily enough. I'll see what numbers I can run up.

[RCgothic]

12 minutes ago, sevenperforce said:

Just imagine what sorts of missions would be possible with the ability to drop a 100-tonne hydrolox propulsion bus into LEO.

Very little unless it launches with the payload or can rendezvous with it very shortly thereafter. 

[sevenperforce]

Just now, RCgothic said:

18 minutes ago, sevenperforce said:

Just imagine what sorts of missions would be possible with the ability to drop a 100-tonne hydrolox propulsion bus into LEO.

Very little unless it launches with the payload or can rendezvous with it very shortly thereafter. 

Immediate rendezvous would be the plan, yes.

[sevenperforce]

Note that the use of the SSMEs and ET-derived common core tank as the orbital insertion vehicle is what was proposed by DIRECT for the Jupiter launch family, the "original" SLS that our buddies over at NSF lobbied for. Payload masses up to 70 tonnes would send the core tank all the way to orbit; payload masses over 70 tonnes would use an upper stage. As I've shown above, the use of 5-segment SRBs and a super-Atlas skirt configuration increases this capability to 100 tonnes, all without any upper stage:

Spoiler

DIRECT's Jupiter launch family was a far better idea than the current SLS system; adding the super-Atlas configuration makes it even better.

[shynung]

3 hours ago, sevenperforce said:

Adding tanks for the skirt engines would make TWR worse, not better.

I suppose not. But you can compensate by using a smaller core booster, a la Soyuz.

[sevenperforce]

49 minutes ago, shynung said:

I suppose not. But you can compensate by using a smaller core booster, a la Soyuz.

Soyuz is kerolox. Hydrolox strap-on liquid boosters are ridiculously inefficient; just look at Delta IV Heavy. A hydrolox core stage really only makes sense if you're sending it all the way (or almost all the way) to orbit, as with the Shuttle, the DIRECT's Jupiter family, and my proposal. Another advantage is that the SLS core stage size and the use of the SSMEs is already established and tested by the Shuttle program. If we wanted to do liquid boosters, it would be better to go with the Pyrios approach and use one or two F-1As on each kerolox booster. But then you have to plumb the pad for LOX, LH₂, and RP-1, which is unpleasant.

EDIT: Delta IV heavy uses an 82-tonne (dry mass) vehicle to place 29 tonnes into orbit; Falcon Heavy uses a 70.6-tonne vehicle to place more than twice as much mass into orbit. That's what I mean about low efficiency of hydrolox strap-on boosters.

Edited May 25, 2017 by sevenperforce

[DerekL1963]

4 hours ago, sevenperforce said:

Adding tanks for the skirt engines would make TWR worse, not better. But yeah, adding SRBs is one way to fix it.

I could envision four configurations: Core + Skirt, Core + Boosters, Core + Skirt + Boosters, and Core + Skirt + Boosters + Upper Stage.

SRBs are one option, but advanced liquid boosters powered by F-1As is preferable, I think.

Honestly, if you're adding complexity (and cost!) to solve basic design problems (launch TWR)...  That's pretty much a sign that you should ball up that design, throw it in the nearest receptacle, and start over fresh.

[sevenperforce]

19 minutes ago, DerekL1963 said:

Honestly, if you're adding complexity (and cost!) to solve basic design problems (launch TWR)...  That's pretty much a sign that you should ball up that design, throw it in the nearest receptacle, and start over fresh.

Shyung was proposing the addition of liquid boosters or SRBs, but the 4+2 Super Atlas configuration has sufficient TWR on its own. You could add SRBs as a way to increase payload or add an upper stage. 

[shynung]

3 hours ago, sevenperforce said:

Soyuz is kerolox. Hydrolox strap-on liquid boosters are ridiculously inefficient

Forgot. I agree that hydrolox boosters aren't really efficient for strap-on boosters. Much better off going the SRB route.

Though, I do question whether we can do away with a detachable skirt-mounted engines by substituting more SRBs. Basically, let the SRBs handle the launch TWR, and have the core be some sort of sustainer motor, much like how the old Space Shuttle stack was.

So the booster configurations would primarily be Core + Upper stage, adding SRBs as necessary.