Space Launch System: How to launch NASA’s new monster rocket

[clongton]

Reusability v.s Disposable: It really comes down to the flight rate. Unless a system is going to fly multiple times per year the scales tip in favor of disposable. Reusability comes into it's own only with heavy reuse.

There is a lot to be said for reusability and Shuttle showed us that it can work quite well. But Shuttle also showed us that the cost for that can be extremely high. Shuttle Program Manager John Shannon stated as much at one of the Augustine Commission hearings (in D.C. IIRC) that it would have been more cost effective to replace the SSME's with new ones every time rather than refurbish the flown engines and the same could be said for the SRB's. That was only because of the low flight rate however. Had Shuttle actually flown as often as she was designed to, reuse of the SRB's and SSME's would have been more cost effective than replacement.

When John made those statements at the hearings he didn't bring with him the reams of data that backs it all up. He did state that all the data at his disposal, which meant literally everything, lead to that conclusion. I've met John several times, enough to know that my gut tells me to trust his judgement. But there are others here on NSF that know him extremely well and have worked with him constantly for years, such as OV-106, and what I get from them is that his judgement is impeccable. He is one of the few management people at NASA that I trust without question.

So for really the expensive items like SSME's and SRB's it all comes down to flight rate. Applying that lesson-learned to SLS and this thread, we have down-selected to disposable v.s. reusable, based on program cost. At the projected flight rate for SLS it simply makes no sense to incur the very large cost that reusability exacts for that capability.

[edkyle99]

  What I was getting at was that Ares cost $10 or $11B, for one empty test rocket.  By the time SLS, built from "leagacy" pieces, launches for the first unmanned time, it will also have consumed about the same amount.  I wasn't even thinking about the total projected costs of Ares I and Ares V.

The Constellation expenditures did not merely buy one suborbital test flight.  They bought J-2X and a massive new vacuum test stand at Stennis.  They bought five segment booster, which will be used for SLS.  They bought tooling at Michoud, which will be used for SLS and Orion.  And Orion, of course, paid for by Constellation, built at Michoud and KSC in facilities paid for by Constellation, lowered on chutes and protected by LAS tested during Constellation.  They bought a new launch platform at KSC, which will be modified for SLS.  And so on.

Don't build a new cislunar economy, then you don't need to build enough rockets to launch enough so that the flight rates ever get high enough, so re-usable never becomes economically feasible.

Don't build it, and they won't come.  It's worked for forty years.  Unless something changes, SLS will continue the legacy.

We live in an economy that moves at breathtaking speed, exploiting every conceivable profit alternative.  If there was an economic reason for lunar exploration, it would already have happened.   

Regardless, SLS is not going to the Moon.

 - Ed Kyle

[clongton]

Regardless, SLS is not going to the Moon.

 - Ed Kyle

SLS isn't supposed to go to the moon. It only goes to LEO. 

[Warren Platts]

If there was an economic reason for lunar exploration, it would already have happened.

 - Ed Kyle

Which of course follows from the general principle:

∀x (If there is an economic reason for x, then x would already have happened.)

[ChileVerde]

They bought five segment booster, which will be used for SLS.  They bought tooling at Michoud, which will be used for SLS and Orion. 

Just to make another try at this, what production rate could that facility sustain without needing to be enlarged?

[Robotbeat]

FWIW, Lockheed thinks that partial reusability can make sense as low as 8 flights per year.

[edkyle99]

They bought five segment booster, which will be used for SLS.  They bought tooling at Michoud, which will be used for SLS and Orion. 

Just to make another try at this, what production rate could that facility sustain without needing to be enlarged?

The tooling was being set up to support two Ares V and two Ares I missions per year.  Ares I is obviously gone, with its space possibly being reassigned for future SLS upper stages, and the SLS launch rate is projected to be lower than the Ares V launch rate, so Michoud will clearly be able to handle SLS.  My guess is that the place could produce more than two cores in a year if needed.

RS-25E production rate may be more of a limiting factor than core structure fabrication and assembly. 

 - Ed Kyle

[ChileVerde]

The tooling was being set up to support two Ares V and two Ares I missions per year.  Ares I is obviously gone, with its space possibly being reassigned for future SLS upper stages, and the SLS launch rate is projected to be lower than the Ares V launch rate, so Michoud will clearly be able to handle SLS.  My guess is that the place could produce more than two cores in a year if needed.

RS-25E production rate may be more of a limiting factor than core structure fabrication and assembly. 

 - Ed Kyle

Thanks much. Those are the kinds of numbers we should have available when thinking about future SLS-supported missions and programs.

[veedriver22]

Reusability v.s Disposable: It really comes down to the flight rate. Unless a system is going to fly multiple times per year the scales tip in favor of disposable. Reusability comes into it's own only with heavy reuse.

There is a lot to be said for reusability and Shuttle showed us that it can work quite well. But Shuttle also showed us that the cost for that can be extremely high. Shuttle Program Manager John Shannon stated as much at one of the Augustine Commission hearings (in D.C. IIRC) that it would have been more cost effective to replace the SSME's with new ones every time rather than refurbish the flown engines and the same could be said for the SRB's. That was only because of the low flight rate however. Had Shuttle actually flown as often as she was designed to, reuse of the SRB's and SSME's would have been more cost effective than replacement.

When John made those statements at the hearings he didn't bring with him the reams of data that backs it all up. He did state that all the data at his disposal, which meant literally everything, lead to that conclusion. I've met John several times, enough to know that my gut tells me to trust his judgement. But there are others here on NSF that know him extremely well and have worked with him constantly for years, such as OV-106, and what I get from them is that his judgement is impeccable. He is one of the few management people at NASA that I trust without question.

So for really the expensive items like SSME's and SRB's it all comes down to flight rate. Applying that lesson-learned to SLS and this thread, we have down-selected to disposable v.s. reusable, based on program cost. At the projected flight rate for SLS it simply makes no sense to incur the very large cost that reusability exacts for that capability.

It occurs to me that there is a little more to reusability than flight rate.
A high flight rate is needed but the rebuild frequency also matters.
If you have to rebuild it every other launch I think it would still cost more.
Shuttle engines were rebuiilt each flight weren't they?

[baldusi]

It occurs to me that there is a little more to reusability than flight rate.
A high flight rate is needed but the rebuild frequency also matters.
If you have to rebuild it every other launch I think it would still cost more.
Shuttle engines were rebuiilt each flight weren't they?

SSME Block III was going to solve that. That work did include most of what is going to be the RS-25E. But that work was suspended after the decision to shutdown the Shuttle program. And as Ares V was going to use RS-68K, there was no point in keeping spending money