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SLS / Orion / Beyond-LEO HSF - Constellation => Heavy Lift Launch Vehicle (HLV/SLS) => Topic started by: Chris Bergin on 01/05/2016 02:19 PM

Title: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chris Bergin on 01/05/2016 02:19 PM
Something for everyone in this....from massive SLS/RS-25 fans, to those who want to boo the cosy arrangement with SLS contractors :)

http://www.nasaspaceflight.com/2016/01/nasa-defends-restart-rs-25-production/
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: baldusi on 01/05/2016 03:42 PM
Is the justification document available on the Internet or L2?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Heinrich on 01/05/2016 03:53 PM
Nice article!

I'm wondering though, it is written that 4 engines are used for a fifth engine set, and 2 engines are basically spare. Based on the currently known differences between (formerly) RS-25D and RS-25E, can the two spare engines be a drop-in replacement for the RS-25Ds as well?? Or can they only be spare for the fifth (new) set?


That small company who has not produced/developped engines so far, andy guess who that would be?  BE?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: PahTo on 01/05/2016 03:54 PM

Thanks for the article!
Please clarify:  is the total cost to ramp up production capabilities and fabricate six engines 2.66 $$billion (1.16 $billion ramp up and 1.5 $billion for fabrication), or is it 1.16 $billion plus .34 $billion for a total of 1.5 $$billion for all?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: PahTo on 01/05/2016 04:02 PM

Thanks for the article!
Please clarify:  is the total cost to ramp up production capabilities and fabricate six engines 2.66 $$billion (1.16 $billion ramp up and 1.5 $billion for fabrication), or is it 1.16 $billion plus .34 $billion for a total of 1.5 $$billion for all?

Whups--you answered my question later in the article...sounds like the total is 1.5 $billion:

“A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.”
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: gospacex on 01/05/2016 04:33 PM
> “It is not a new engine development effort,” the document stressed.

Looking at the price, several companies built entire new LVs (with test facilities, pads, etc) from scratch for less.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Hog on 01/05/2016 04:33 PM
Is the justification document available on the Internet or L2?
Available on L2 in this L2 thread, post #30.

http://forum.nasaspaceflight.com/index.php?topic=34671.20
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: M_Puckett on 01/05/2016 04:40 PM
> “It is not a new engine development effort,” the document stressed.

Looking at the price, several companies built entire new LVs (with test facilities, pads, etc) from scratch for less.

I bet SpaceX will build the whole frikkin' BFR for less.

That said, are there going to be any 3D printed parts in these?  Channel-wall nozzles?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 01/05/2016 04:54 PM

Thanks for the article!
Please clarify:  is the total cost to ramp up production capabilities and fabricate six engines 2.66 $$billion (1.16 $billion ramp up and 1.5 $billion for fabrication), or is it 1.16 $billion plus .34 $billion for a total of 1.5 $$billion for all?

Whups--you answered my question later in the article...sounds like the total is 1.5 $billion:

“A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.”

I interpret it as $2.23B for redesign and certification, then $1.5B more for production of the first 6 engines.

Edit: My confusion came from what equivalent implied. I was inferring that it meant RS-25E in place of RS-25D. Oli is correct below.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Tev on 01/05/2016 05:05 PM
Quote
The proposed action follows directly in line with the strategy for cost minimization by continuing with the use of the same core-stage engine design, with minimal modifications, and with the restart of a historically proven (though currently dormant) production line
Quote
strategy for cost minimization
Quote
$1.16 billion
Quote
$1.5 billion
Six engines . . .

I don't get it.

Is there no way to get any other engine for cheaper? Is it really necessary to spend over 400M$ per ENGINE? I mean, Delta IV heavy is looking so cheap right now.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: gospacex on 01/05/2016 05:22 PM
Quote
$1.16 billion
Quote
$1.5 billion
Six engines . . .

I don't get it.

Is there no way to get any other engine for cheaper?

Stop your capitalist nonsense right now. ;)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: butters on 01/05/2016 05:31 PM
The large solids + sustainer core configuration pretty much demands a regeneratively-cooled high-pressure staged-combustion hydrolox engine like the RS-25. As seen with the RS-68 powered "Ares VII" debacle, even a relatively small departure from the RS-25 design concept creates serious problems for the launch vehicle.

Congress and NASA have consistently extolled the economic virtues of "Shuttle-derived" technology. Now we just have to live with the consequences.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Oli on 01/05/2016 05:32 PM
Read the article, how hard can it be?

It's $1.5bn in total, of which $1.16bn for the production restart.

So $340m for 6 engines, or $57m per engine.

Still not exactly cheap.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Dante80 on 01/05/2016 05:40 PM
That would put a price-tag of $228M for the engine set for one mission. The engines also go down the drink in the end.

I really hope that subsequent orders would put that cost down...its pretty big.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: clongton on 01/05/2016 05:50 PM
Thanks for the write-up. Nicely done and informative.
I echo the question about 3d-printing. Other companies have demonstrated the viability of the additive manufacturing process. What is Aerojet's capabilities in this regard and do they plan to implement them for the RS-25 effort?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Finn on 01/05/2016 06:12 PM
Great article!

A small glitch: The "SLS Forum Section" link actually points to the SpaceX forum section.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 01/05/2016 06:19 PM
Great article!

A small glitch: The "SLS Forum Section" link actually points to the SpaceX forum section.

Maybe he figures that since SpaceX discussions appear everywhere, we might as well move all discussions to the SpaceX forum.  ;D
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Hog on 01/05/2016 06:24 PM
Nice article!

I'm wondering though, it is written that 4 engines are used for a fifth engine set, and 2 engines are basically spare. Based on the currently known differences between (formerly) RS-25D and RS-25E, can the two spare engines be a drop-in replacement for the RS-25Ds as well?? Or can they only be spare for the fifth (new) set?

The two extra engines can be spares for either the newly certified engines and the residual engines.  They will also be used for risk mitigation of the 5th set of RS25 engines.(so long as only 2 RS25's out of the cluster of 4 have issues)

Source is the RS-25 Justification for Other Than Full and Open Competition (JOFOC) document.

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 01/05/2016 06:28 PM
$1.5bn in total, of which $1.16bn for the production restart. So $340m for 6 engines, or $57m per engine. Still not exactly cheap.

That would put a price-tag of $228M for the engine set for one mission. The engines also go down the drink in the end.

I really hope that subsequent orders would put that cost down...its pretty big.

Yea, these are the correct numbers.

It will be interesting to see how soon BFR comes on line, what its costs are, and whether Musk offers flight services to NASA for whatever NASA wants to do.

I personally think SLS will be canceled and NASA directed to work collaboratively with SpaceX via Space Act Agreement. It would be silly to continue pursuing this thing if something cheaper and more robust comes on line.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/05/2016 06:41 PM
So we have a $ amount for one portion of the manufacturing cost of SLS per flight $57Mx4= $228M. The original $300M marginal/incremental cost for manufacture of the complete SLS is looking a little low.

The other item is it is going to take 11 years to produce 6 engines. 2016 to 2027. There must be a lot of subcontractor parts suppliers requiring a long time to restart. And some suppliers that went out of business!
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AnalogMan on 01/05/2016 07:09 PM
Is the justification document available on the Internet or L2?
Available on L2 in this L2 thread, post #30.

http://forum.nasaspaceflight.com/index.php?topic=34671.20

Public version can be found here (not OCR'd like the L2 version):
http://prod.nais.nasa.gov/eps/eps_data/168372-JA-001-001.pdf
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 01/05/2016 07:21 PM
The other item is it is going to take 11 years to produce 6 engines. 2016 to 2027. There must be a lot of subcontractor parts suppliers requiring a long time to restart. And some suppliers that went out of business!

Even ignoring that, producing only 6 engines over *11* years... Madness. But that is AR's standard operating procedure these days - hand building a handful of engines every year.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: montyrmanley on 01/05/2016 07:39 PM
11 years to produce 6 engines. Holy smokes! For comparison: it took about four years to build the Golden Gate Bridge. The Empire State Building was erected in just a bit over a year. The Hoover Dam was completed in about five years. During World War II, the United States built an aircraft carrier in about a year (and as a publicity stunt, built a liberty ship in five days). Now, I will grant that a rocket engine is a complex piece of machinery, but this is just outlandish. What are they doing that takes so blessedly long? Carving the entire engine out of a block of solid metal with a dental pick?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Dante80 on 01/05/2016 08:12 PM
To be fair here...the reason that ARJ is building 6 engines in 11 years is twofold.

1. Thats when NASA is going to need them.
2. They also have to work on 16 existing engines.

This is one of the reasons why the cost per engine gets so high btw. If NASA ordered 3 dozens, then the cost per engine would be a fraction of what is quoted now. I don't believe for a second that they need 11 years to produce them.

I personally think SLS will be canceled and NASA directed to work collaboratively with SpaceX via Space Act Agreement. It would be silly to continue pursuing this thing if something cheaper and more robust comes on line.

This is off topic. Lets concentrate on the subject at hand... :)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Zed_Noir on 01/05/2016 08:46 PM
It will be interesting if AR can do this without going over-budget and on schedule.

The recent RS-68A upgrade program should gave some insight.

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/05/2016 09:24 PM
Holy smokes .. 1.5 Billion for six engines .. !! or about 11 Falcon9+Dragon ISS resupply missions... Even for NASA this is crazy.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/05/2016 09:33 PM
It will be interesting if AR can do this without going over-budget and on schedule.

The recent RS-68A upgrade program should gave some insight.

If they cant re-build their own engine on an extremly generous budget like this and over an 11 year time line within budget and schedule then AR is utterly useless and deserve to be killed off, and forgotten in all enternity.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chris Bergin on 01/05/2016 10:08 PM
Great article!

A small glitch: The "SLS Forum Section" link actually points to the SpaceX forum section.

Thanks! Heck, even the news site CMS can't avoid SpaceX distractions! ;D Corrected.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chris Bergin on 01/05/2016 10:09 PM
PS There will be a follow up article with quotes we've got from Aerojet on how they will be reducing the costs per moving from RS-25D to RS-25E.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: montyrmanley on 01/05/2016 10:09 PM
It will be interesting if AR can do this without going over-budget and on schedule.

The recent RS-68A upgrade program should gave some insight.

If they cant re-build their own engine on an extremly generous budget like this and over an 11 year time line within budget and schedule then AR is utterly useless and deserve to be killed off, and forgotten in all enternity.

Actually, this seems mostly to be a NASA life-preserver for AR to keep them afloat so they can provide engines for the SLS. I think the award is so outrageous because it's meant to keep AR healthy enough to survive over the next decade. The per-engine and tooling costs are probably incidental to that larger goal. With ULA phasing out the Delta IV and Atlas V, AR isn't exactly looking at a deep roster of customers. This is speculation, obviously, but if NASA truly thinks that bringing a new vendor up to snuff on the RS-25 would be even more expensive, then this makes a certain amount of sense.

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: shooter6947 on 01/05/2016 10:23 PM
Or they could, you know, put it up for bids in an open competition as to who could design such an engine instead of shoveling out more corporate welfare.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Dante80 on 01/05/2016 10:35 PM
Or they could, you know, put it up for bids in an open competition as to who could design such an engine instead of shoveling out more corporate welfare.

As per NASA, this would introduce a lot of risk to the program. The only other interested entity in such a large hydrolox engine...was a random company that never made a rocket engine.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Zed_Noir on 01/05/2016 10:38 PM
Or they could, you know, put it up for bids in an open competition as to who could design such an engine instead of shoveling out more corporate welfare.

Problem is that the other current active US large liquid engine manufacturers is not interested in large HydeoLox engines. So basically asking AR how much they want.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 01/05/2016 10:58 PM
Or they could, you know, put it up for bids in an open competition as to who could design such an engine instead of shoveling out more corporate welfare.

Problem is that the other current active US large liquid engine manufacturers is not interested in large HydeoLox engines. So basically asking AR how much they want.

That is the risk you take when you design the vehicle around specific contractors instead of buying a capability.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Dante80 on 01/05/2016 11:14 PM
Well they wanted to keep the industrial complex (jobs) involved with the STS, so a clean sheet design was off the table for SLS.

I'm really curious btw on why did they choose to get rid of the RS-25E designation for the improved/expendable SLS variant. It seems like they want to call it simply RS-25 from now on.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 01/05/2016 11:44 PM
Well they wanted to keep the industrial complex (jobs) involved with the STS, so a clean sheet design was off the table for SLS.

I'm really curious btw on why did they choose to get rid of the RS-25E designation for the improved/expendable SLS variant. It seems like they want to call it simply RS-25 from now on.

Maybe they want to de-emphasize that they are actually redesigning a reusable engine to make it more expendable -- as stated in the recent glowing presser.  Maybe it will even be bio-degradable...

Good news is that Technology Development cannot go any lower. 
Welcome to the bottom AR and NASA.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: deltaV on 01/06/2016 02:16 AM
Creating the SLS program ~5 years ago was a big mistake. Even now with much of the development already paid for it may be a good idea to cancel SLS. However if you insist on building SLS, sole-sourcing the core engines (i.e. SSME) from AJR is probably the right call. In other words SLS with AJR SSMEs is bad but SLS with competed core engines would be worse.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: zodiacchris on 01/06/2016 02:31 AM
What I find disturbing is that the fifth set of engines are only required in 2027, so there will only be four SLS flying in the next 11 years?  :o
I was under the impression that they'd be aiming at a somewhat higher launch cadence.  :-\
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Todd Martin on 01/06/2016 02:44 AM
On the positive side, once the US Government pays to restart production of the RS25 as well as updating the design for modern fabrication methods and a fewer part count, it will be another option on the shelf for future launch vehicle designs.  A lot of people have said the RS25 is an amazing engine, it is just expensive.  Well, these investments will eventually make RS25 a lot cheaper to some future user if they step forward.

Also, consider the lonely fate of the J2X engine.  An updated RS25 makes a great 1st stage choice to accompany the J2X as a 2nd stage engine.

Right now, we have very few domestic competitors for launch vehicles.  If AR stops being an engine supplier for ULA, they may very well partner with a new company using these engines or get into the launch vehicle business themselves.

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: sdsds on 01/06/2016 04:33 AM
PS There will be a follow up article with quotes we've got from Aerojet on how they will be reducing the costs per moving from RS-25D to RS-25E.
It's $1.5bn in total, of which $1.16bn for the production restart.

So $340m for 6 engines, or $57m per engine.

As the Shuttle program was winding down and alternatives like DIRECT were being discussed there was an estimate that about $750m was needed to modernize RS25 production. At the time the idea was that additional RS-25D engines would cost ~$72m each, but that could be cut to ~$39m each once modernization of production was complete. So without modernization a purchase in 2015 to take delivery of six engines in 2017 would have been $432; after modernization it would have been $234m. That was without production restart costs as the contract would have been let before the line was truly shuttered.

Apparently what AJR now proposes is ~$410m for restart; $750m in modernization; price drop to $57m per unit for small batches. The $39m per engine estimate mentioned above was for approximately 8 to 12 engines per year... which might have been affordable with DIRECT or AJAX. Apparently the need for those quantities isn't (yet) in the picture for SLS....
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: RocketGoBoom on 01/06/2016 05:14 AM
What I find disturbing is that the fifth set of engines are only required in 2027, so there will only be four SLS flying in the next 11 years?  :o
I was under the impression that they'd be aiming at a somewhat higher launch cadence.  :-\

I will be shocked if they even need 4 sets of engines for the entire program life.
My bet is 2 sets and done.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Dante80 on 01/06/2016 08:56 AM
The baseline is a production rate of 2 engines per year.
Here is the project breakdown according to the JOFOC.

Its unclear how much the per engine cost would be after certification, assuming that a production rate like that holds.

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 01/06/2016 12:07 PM
Will the new production line be able to produce 8 engines per year instead of 0.75 per year?
Is that another billion dollar effort?

Did anyone ever produce 8 RS-25s in a year?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/06/2016 12:33 PM
Will the new production line be able to produce 8 engines per year instead of 0.75 per year?
Is that another billion dollar effort?

Did anyone ever produce 8 RS-25s in a year?

I dont know about ever. I think it is highly unlikely that 8 RS-25s will be produced in a year at any point in time.

Quote from: Page 6 in the Justifacation document
Engine production rate shown is set at two engines per year, which is the SLS Program baseline steady state need and therefore establishes the manufacturing infrastructure and labor force size.

So if production need to be higher, more money is needed. But it dosent since steady state is 2 per year. Which also says something about expected long term flight rate i guess.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Dante80 on 01/06/2016 12:43 PM
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.

So, the factory can hold 10/12 engines inside, in various stages of production/delivery.

I might have this wrong.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: gospacex on 01/06/2016 01:12 PM
On the positive side, once the US Government pays to restart production of the RS25 as well as updating the design for modern fabrication methods and a fewer part count, it will be another option on the shelf for future launch vehicle designs.  A lot of people have said the RS25 is an amazing engine, it is just expensive.  Well, these investments will eventually make RS25 a lot cheaper to some future user if they step forward.

This "it will be cheaper" thing tends to, you know, fail to happen.

A semi-random example: ULA was supposedly created to make launches cheaper. After which they become more expensive.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/06/2016 02:04 PM
On the positive side, once the US Government pays to restart production of the RS25 as well as updating the design for modern fabrication methods and a fewer part count, it will be another option on the shelf for future launch vehicle designs.  A lot of people have said the RS25 is an amazing engine, it is just expensive.  Well, these investments will eventually make RS25 a lot cheaper to some future user if they step forward.

This "it will be cheaper" thing tends to, you know, fail to happen.

A semi-random example: ULA was supposedly created to make launches cheaper. After which they become more expensive.

Theres that, but also it seems like bad business acumen to invest 0.7-1 Billion to save maybe 20 million per engine on six engines. They have to build 35-50 engines for it to make sense (break even).
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: notsorandom on 01/06/2016 03:20 PM
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.

So, the factory can hold 10/12 engines inside, in various stages of production/delivery.

I might have this wrong.
A rate of 2 a year is a head scratcher. It literally doesn't add up. One SLS needs 4 engines, they want to get into a launch cadence of at least once a year. A rate of two engines a year means a launch every two years. If the contract really does call for two engines a year then eventually they will have to ramp up capability or reduce the flight rate.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/06/2016 03:34 PM
Thanks for the article great Chris. :) I find it ironic that NASA has to justify or explain anything about SLS or the RS-25. It doesn't matter, Congress ordered it to be built end of story.... Did we forget how hard Charlie tried to slow walk it in the first place? Flight rate really? NASA will just continue to splice in an Orion/SLS to Mars video promo each time a Commercial Cargo and upcoming Commercial Crew flight to ISS and no one will be the wiser... ;)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Dante80 on 01/06/2016 03:58 PM
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.

So, the factory can hold 10/12 engines inside, in various stages of production/delivery.

I might have this wrong.
A rate of 2 a year is a head scratcher. It literally doesn't add up. One SLS needs 4 engines, they want to get into a launch cadence of at least once a year. A rate of two engines a year means a launch every two years. If the contract really does call for two engines a year then eventually they will have to ramp up capability or reduce the flight rate.

It will be some time before launches catch up though.

The contract seems to be for 6 engines, the first two of which will be delivered for integration in 2022. By the time they are used all (2027), a new contract placed before 2022 would have another 10 engines ready by then (I don't count 2 engines that will remain for spares).

If we assume 1 SLS launch per year (from 2028 onwards), then launches will catch up with production in..2032 (EM-10 or EM-11).
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/06/2016 04:00 PM
If SLS operates for as long as STS (30 years) and after 2027 launches at a rate of 2 per year, that is only an additional 20 years and 40 SLS launches (first year is 2017-2018+30 is 2047).

4 engines per launch is only 160 engines total produced over 20 years. At a price of ~$50M per engine that is a total of $8B in engines or $400M per year in contract spending to AJR.

$1.5B over 11 years is only a $136M per year. This is something but not nearly enough to keep AJR afloat all by itself. It helps but without other work AJR could still fold. AJR has been loosing business lately. This is the troubling item not the price or the duration but AJR's health as a business.

Current engine lines of AJR:
RS25 restarting 2/yr at $57M per engine
RS68A ~9/yr dropping to only 3/yr in 2018-2019 at ~$20M per engine
RL-10 ~10/yr increasing by 2/yr for EUS in 2017 and then possibly dropping to only 2 in 2022 if ULA decides to use a different engine for ACES at $10M per engine

Current LV engine revenue = $416M
In 2027 LV engine revenue = $194-294M (depends on ULA's decision on the engine used in ACES, $40M for 4 RL-10s vs $10M for a single BE-3)

This is not encouraging for AJR health in the business of engine manufacture for LVs.

LV engine revenue as a percentage of all AJR business is shrinking.
This could mean that overheads rise making the 2/yr manufacture of RS-25 rise in costs sharply by 2022 when additional engine contracts are made.

Edit: I included RS-68's in 2027. With Vucan/ACES operating the complete DeltaIV line even for DIVH would stop flying in 2025. So the revenue in 2027 for LV engines could be solely from SLS use of 4 RS-25 and 4 RL-10s per flight at $134M /yr for 2 RS-25 and 2 RL-10s. No other US launch vehicle would be using AJF engines. Also the build rate is set at 2/yr because that was the tooling and rates needed to supply STS with new engines for their flight rate of 3 STS per year using 9 engines per year (reuse rate of 5 flights per engine require a build rate of 2 /yr).
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 01/06/2016 04:15 PM
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.

5 years to build an engine!?!?!
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Dante80 on 01/06/2016 04:20 PM
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.

5 years to build an engine!?!?!

From the JOFOC.

(http://i.imgur.com/nG4pWAP.png)

ARJ hand builds their engines (at least, that's what I knew they did in the past).
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: bad_astra on 01/06/2016 04:25 PM
We could be building F1's if we were going to go resurrecting hardware.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 01/06/2016 04:34 PM
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.

5 years to build an engine!?!?!

From the JOFOC.

(http://i.imgur.com/nG4pWAP.png)

ARJ hand builds their engines (at least, that's what I knew they did in the past).

 :o This is the production process I imagine for a 5 year build: (see image) It's no wonder the surviving RS-25's are treated like precious commodities.

(Meanwhile, another domestic liquid engine producer builds over 100 engines per year)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/06/2016 05:24 PM
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.

5 years to build an engine!?!?!

From the JOFOC.

(http://i.imgur.com/nG4pWAP.png)

ARJ hand builds their engines (at least, that's what I knew they did in the past).

 :o This is the production process I imagine for a 5 year build process: (see image) It's no wonder the surviving RS-25's are treated like precious commodities.

(Meanwhile, another domestic liquid engine produces over 100 engines per year)
In an article several years ago (I could not find it) the wood form used to bend the tubing for the engine bell for RL10 was shown. The RL-10 is still manufactured in almost the same way its was done in the 1960's the RS-25 manufacturing tech is the 1970's. 2015 manufacturing tech is a lot different which includes 3D printing of very complex parts in a highly repeatable level of quality manufacturing. I wonder how many parts (especially those no longer having a supplier) will be manufactured using 3D printing?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: shooter6947 on 01/06/2016 05:26 PM

 :o This is the production process I imagine for a 5 year build: (see image) It's no wonder the surviving RS-25's are treated like precious commodities.


Except that they're not.  5 years hand-building an engine might have even come close to making sense when those engines were being reused and reflown on multiple missions.  Now those precious jewels are going to be dropped into the Atlantic like the Heart of the Ocean from Titanic (spoiler alert).
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TrueBlueWitt on 01/06/2016 05:42 PM
I'm thinking block 2 should have 3 RS25 and a pair of RTLS FH for boosters.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: notsorandom on 01/06/2016 05:43 PM
It will be some time before launches catch up though.

The contract seems to be for 6 engines, the first two of which will be delivered for integration in 2022. By the time they are used all (2027), a new contract placed before 2022 would have another 10 engines ready by then (I don't count 2 engines that will remain for spares).

If we assume 1 SLS launch per year (from 2028 onwards), then launches will catch up with production in..2032 (EM-10 or EM-11).
There is a mismatch in when SLS is expected to begin a 1+ launch a year cadence. Most preliminary manifests I've seen have the start of that happening in 2021-2024. There are currently enough engines to support 3 SLS flights (with a set of 4 backups). At 2 engines a year starting in 2022 and using a 2023 start date for that launch rate it might looks something like:
2018 SLS-1 (12 engines left)
2022 14 engines
2023 SLS-2 (12 engines left)
2024 SLS-3 (10 engines left)
2025 SLS-4 (8 engines left)
One can see where this is heading. In a short time the surplus of engines dwindles and the launch rate either needs to go down or engine production increased. Starting the 1 launch a year cadence in 2027 only delays this. Furthermore by the end of the 2020s NASA wants to be surge launching at a grater than a once a year average for its Mars plans.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: rcoppola on 01/06/2016 06:17 PM
These engines are highly complex for a number of reasons. Certainly reuse was one requirement that drove the design but  so was the fact that this engine's operational envelope occupied sea-level all the way through to orbital. This alone drove a number of requirements wrt two separate, independently controlled pre burners, closed-loop among others. (As far as I can tell from reading up on it)

Interestingly, the RS-25 was a jump off from the original J2. And they spent Millions updating that to the J2X. (now mothballed, but I do understand the thrust Vs isp of that decision)  I am a bit concerned that the SLS has been designed around a complex, very expensive sustainer engine. I understand why they did it but always believed that in the background, they would create new requirements to allow the RS25 to be simplified both design and manufacturing wise.

Seeing as now these engines are part of a 2 stage expendable configuration, did the SLS Program Office provide a new set of requirements for the RS-25? (i'm sure they did but to what extent?)

Would it not have been more efficient in the long run to use the RS-25 as a bases to create a less complex and easier to manufacturing engine using today's techniques? Taking a few extra years to re-certify but coming out with a much less complex and easier engine to reproduce would have been worth it IMO.

I could be way off base here but it seems to me that NASA asks what it will cost to do X and then expends the funds accordingly. Did they push back and say something to the effect that AJR needs to spend some time and come up with a proposal that gets them to say...30Million an engine with production taking no longer then 2.5 years per? Or is this program so locked in now, with so much funding that this just gets lost as a rounding error over so many years. I'm an SLS supporter but this just doesn't seem to be the way to initiate a program that is expected to last for 3 decades...

So that's my issue. I'm ok with AJR being sole sourced  since the entire core is built around their engine but did anyone at NASA push back against their response? Is there absolutely no leverage in the system to allow for this outside of opening it up for competition? Or is this really our only option for many, many legacy reasons.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 01/06/2016 08:48 PM
....this engine's operational envelope occupied sea-level all the way through to orbital....the SLS has been designed around a complex, very expensive sustainer engine....now these engines are part of a 2 stage expendable configuration...

I think this is pretty much still a sustainer from launch to disposal orbit. The Block II with LUS would have used both stages to reach LEO with a massive payload. The Block IB and Block IIB are designed for the core to reach disposal orbit and the EUS to serve as an EDS. So that operational envelope you mention is still a requisite factor.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: rayleighscatter on 01/06/2016 09:21 PM
The first four RS-25's ordered started production in October 1976 and NASA completed their acceptance testing of all four in early 1979 so we know delivery took less than 2.5 years.

NASA wants engines in five years, they'll get them in five years. Contractors will take as much time as they're provided with.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: deltaV on 01/06/2016 11:16 PM
Theres that, but also it seems like bad business acumen to invest 0.7-1 Billion to save maybe 20 million per engine on six engines. They have to build 35-50 engines for it to make sense (break even).

I would guess that even if they didn't modernize the design and didn't produce any new engines they'd still have to spend hundreds of millions of dollars to keep the SSME program alive. Engineers and technicians don't take kindly to being laid off and told to come back in a decade, and even if they cooperated their memories would have faded. The alternative plan you're comparing NASA's plan to has higher costs than the zero you implied.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: A_M_Swallow on 01/07/2016 12:05 AM
How good is the RS-25E as a vacuum engine?
Could we use it to power a large LEO to lunar orbit reusable transfer vehicle?
Also LEO to Mars orbit return?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: robertross on 01/07/2016 12:10 AM
Original Aerojet Rocketdyne release:

http://ir.aerojetrocketdyne.com/releasedetail.cfm?ReleaseID=944137

 "The RS-25 engines designed under this new contract will be expendable with significant affordability improvements over previous versions," added Jim Paulsen, vice president, Program Execution, Advanced Space & Launch Programs at Aerojet Rocketdyne. "This is due to the incorporation of new technologies, such as the introduction of simplified designs; 3-D printing technology called additive manufacturing; and streamlined manufacturing in a modern, state-of-the-art fabrication facility."

'The new engines will incorporate simplified, yet highly reliable, designs to reduce manufacturing time and cost. For example, the overall engine is expected to simplify key components with dramatically reduced part count and number of welds. At the same time, the engine is being certified to a higher operational thrust level.'
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/07/2016 12:43 AM
Original Aerojet Rocketdyne release:

http://ir.aerojetrocketdyne.com/releasedetail.cfm?ReleaseID=944137

 "The RS-25 engines designed under this new contract will be expendable with significant affordability improvements over previous versions," added Jim Paulsen, vice president, Program Execution, Advanced Space & Launch Programs at Aerojet Rocketdyne. "This is due to the incorporation of new technologies, such as the introduction of simplified designs; 3-D printing technology called additive manufacturing; and streamlined manufacturing in a modern, state-of-the-art fabrication facility."

'The new engines will incorporate simplified, yet highly reliable, designs to reduce manufacturing time and cost. For example, the overall engine is expected to simplify key components with dramatically reduced part count and number of welds. At the same time, the engine is being certified to a higher operational thrust level.'
That answers my 3D printing question. But it only covers up the: some of our old suppliers won't talk to us or are out of business so we will find new ones or build the parts in-house using 3D printing since we don't have the tooling or any idea how to or where to get the tooling originally used to manufacture the part.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Zed_Noir on 01/07/2016 01:37 AM
So AR is basically developing a new engine that is also call RS-25.

Think it is like the J-2X to J-2 relationship. So the new engine should be call the RS-25X.  :P
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: robertross on 01/07/2016 02:01 AM
Original Aerojet Rocketdyne release:

http://ir.aerojetrocketdyne.com/releasedetail.cfm?ReleaseID=944137

 "The RS-25 engines designed under this new contract will be expendable with significant affordability improvements over previous versions," added Jim Paulsen, vice president, Program Execution, Advanced Space & Launch Programs at Aerojet Rocketdyne. "This is due to the incorporation of new technologies, such as the introduction of simplified designs; 3-D printing technology called additive manufacturing; and streamlined manufacturing in a modern, state-of-the-art fabrication facility."

'The new engines will incorporate simplified, yet highly reliable, designs to reduce manufacturing time and cost. For example, the overall engine is expected to simplify key components with dramatically reduced part count and number of welds. At the same time, the engine is being certified to a higher operational thrust level.'
That answers my 3D printing question. But it only covers up the: some of our old suppliers won't talk to us or are out of business so we will find new ones or build the parts in-house using 3D printing since we don't have the tooling or any idea how to or where to get the tooling originally used to manufacture the part.

I know one thing for sure: the SLS rocket is becoming grossly expensive. I'm know many questioned its costs from day one, but being justified by its large lift capability & volume. However with decreasing budgets for NASA & a questionable economic position for the USA & the world as a whole, it might soon be facing some critical questions as to sustainability. That perhaps is why the ideas are still being debated as to where this rocket should take people (or science missions): the moon, Mars, asteroid, or other destinations.

I love this engine & what it has done & could one day offer, but there comes a point where you have to scratch your head and wonder if this is all going too far for the (economic) realities of today. I guess we'll have to wait and see, but I'm getting nervous.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: QuantumG on 01/07/2016 02:02 AM
However with decreasing budgets for NASA

It isn't.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Endeavour_01 on 01/07/2016 02:19 AM
Lets not forget everyone that this is the initial engine contract. The main purpose of this contract is to restart production and get the production level to a sustainable point. Note that sustainable is not the amount of engines the SLS program will need AJR to produce to fly indefinitely. It is what is required to sustain the knowledge base and equipment needed to make RS-25s. Once we get into the 2020s more contracts will be issued to fulfill future engine needs. Production can be increased if needed.

In terms of cost the first 4 engine sets for SLS are already bought and paid for. For the next SLS flight that will use the engines discussed here it will add a total of $300 Million to flight costs (I am putting the $1.15 Billion to restart production under DDT&E). Presumably the cost will drop to somewhere around $200 Million for the next flight set. That is about 1/10th of the current budget for SLS.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: sdsds on 01/07/2016 04:36 AM
So AR is basically developing a new engine that is also call RS-25.

Think it is like the J-2X to J-2 relationship. So the new engine should be call the RS-25X.  :P

No, it isn't.

How good is the RS-25E as a vacuum engine?

Hmm. I wonder what the size of a "fully" expanded RS-25-Vac nozzle would be? Fun to think about, but CxP discovered there would be trouble trying to restart an RS-25 in space.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Khadgars on 01/07/2016 04:39 AM
Lets not forget everyone that this is the initial engine contract. The main purpose of this contract is to restart production and get the production level to a sustainable point. Note that sustainable is not the amount of engines the SLS program will need AJR to produce to fly indefinitely. It is what is required to sustain the knowledge base and equipment needed to make RS-25s. Once we get into the 2020s more contracts will be issued to fulfill future engine needs. Production can be increased if needed.

In terms of cost the first 4 engine sets for SLS are already bought and paid for. For the next SLS flight that will use the engines discussed here it will add a total of $300 Million to flight costs (I am putting the $1.15 Billion to restart production under DDT&E). Presumably the cost will drop to somewhere around $200 Million for the next flight set. That is about 1/10th of the current budget for SLS.

Completely agree.  I think a lot of people did not read the article correctly and jumped to misinformed conclusions.

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/07/2016 04:54 AM
The other item is that there are not just 6 engines but actually 8. 6 flight and 2 test articles for qualification testing. The 2 test articles are part of the $1.15B restart costs.

The fact that there will be new parts manufacturing (different sources and newer manufacturing methods) is a good thing even if the actual design does not change in any appreciable difference. The key is to maintain the design such that the old and new engines are interchangeable without even a software change required on the rocket side. Otherwise there would be a lot of redone engineering for the "new" engine also making it very difficult to mix on same rocket.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Oli on 01/07/2016 07:12 AM
What I find disturbing is that the fifth set of engines are only required in 2027, so there will only be four SLS flying in the next 11 years?  :o
I was under the impression that they'd be aiming at a somewhat higher launch cadence.  :-\

Yeah, they seem to be pretty confident they don't need the engines before 2027.

Looks like not much will be happening in the 2020s... :(
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 01/07/2016 07:23 AM
Lets not forget everyone that this is the initial engine contract. The main purpose of this contract is to restart production and get the production level to a sustainable point. Note that sustainable is not the amount of engines the SLS program will need AJR to produce to fly indefinitely. It is what is required to sustain the knowledge base and equipment needed to make RS-25s. Once we get into the 2020s more contracts will be issued to fulfill future engine needs. Production can be increased if needed.

And this is a prime example where 'sustaining the knowledge base' is overrated, and we are anchored down to old technology and old manufacturing methods. Don't treat AR and its engine know-how as a resource that once lost can not be recovered. It can. And it can be done better.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/07/2016 11:49 AM
Theres that, but also it seems like bad business acumen to invest 0.7-1 Billion to save maybe 20 million per engine on six engines. They have to build 35-50 engines for it to make sense (break even).

I would guess that even if they didn't modernize the design and didn't produce any new engines they'd still have to spend hundreds of millions of dollars to keep the SSME program alive. Engineers and technicians don't take kindly to being laid off and told to come back in a decade, and even if they cooperated their memories would have faded. The alternative plan you're comparing NASA's plan to has higher costs than the zero you implied.

Why would you keep the program alive if you didnt want to produce more engines?

The alternative plan im comparing to, is AJR just producing replicas of the current engines and not doing any further development and updating.

As per stated earlier in this thread that would mean a production price of around 20 million more per engine.

Now the contract is for 1.5 Billion. So a large amount of that is for updating. Earlier in the thread 750 Million was mentioned as the cost of delevopment .. Since it is unknown i used an interval.

I did not imply zero cost for the alternative.


As the Shuttle program was winding down and alternatives like DIRECT were being discussed there was an estimate that about $750m was needed to modernize RS25 production. At the time the idea was that additional RS-25D engines would cost ~$72m each, but that could be cut to ~$39m each once modernization of production was complete. So without modernization a purchase in 2015 to take delivery of six engines in 2017 would have been $432; after modernization it would have been $234m. That was without production restart costs as the contract would have been let before the line was truly shuttered.

Apparently what AJR now proposes is ~$410m for restart; $750m in modernization; price drop to $57m per unit for small batches. The $39m per engine estimate mentioned above was for approximately 8 to 12 engines per year... which might have been affordable with DIRECT or AJAX. Apparently the need for those quantities isn't (yet) in the picture for SLS....
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/07/2016 12:06 PM
Lets not forget everyone that this is the initial engine contract. The main purpose of this contract is to restart production and get the production level to a sustainable point. Note that sustainable is not the amount of engines the SLS program will need AJR to produce to fly indefinitely. It is what is required to sustain the knowledge base and equipment needed to make RS-25s. Once we get into the 2020s more contracts will be issued to fulfill future engine needs. Production can be increased if needed.

In terms of cost the first 4 engine sets for SLS are already bought and paid for. For the next SLS flight that will use the engines discussed here it will add a total of $300 Million to flight costs (I am putting the $1.15 Billion to restart production under DDT&E). Presumably the cost will drop to somewhere around $200 Million for the next flight set. That is about 1/10th of the current budget for SLS.

You cant just wave away what you think is DDT&E of 1.15 Billion. That cost is still there and very much part of the cost of the SLS. Only it is not part of the marginal cost.

These six engines, from which the 2 first "MTBF" engines will be used for components for the fourth SLS flight (Using the last of the 16 engines avaliable now) have an average cost of 250M. Even if marginal cost of the last engine in this batch and the first in a possible follow on is about 60 mill. 
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/07/2016 12:19 PM
The other item is that there are not just 6 engines but actually 8. 6 flight and 2 test articles for qualification testing. The 2 test articles are part of the $1.15B restart costs.

The fact that there will be new parts manufacturing (different sources and newer manufacturing methods) is a good thing even if the actual design does not change in any appreciable difference. The key is to maintain the design such that the old and new engines are interchangeable without even a software change required on the rocket side. Otherwise there would be a lot of redone engineering for the "new" engine also making it very difficult to mix on same rocket.

This is wrong. At least from what ive read in the document.

Quote from: Page 3 justification document
The number of new flight engines to be included as part of the contract is six (6). This amount of flight hardware is necessay to fulfill the needs of one SLS launch (four engines are used per launch) and two complete sets of engine hardware (i.e., the equivalent of two engines) necessary for risk mitigation in the form of spare hardware for both newly certified engines and residual RS-25 engines.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/07/2016 12:30 PM
What I find disturbing is that the fifth set of engines are only required in 2027, so there will only be four SLS flying in the next 11 years?  :o
I was under the impression that they'd be aiming at a somewhat higher launch cadence.  :-\

Yeah, they seem to be pretty confident they don't need the engines before 2027.

Looks like not much will be happening in the 2020s... :(

Something like one every 2 years, after initial gap. 2018,2021,2023,2025 and then the new engines in 2027.

Looks right to me.

Also at a launch rate of 1 SLS per 2 years, that match what is Baseline steady state production of 2 engines per year.

I know this contradicts what has been said to be minimum safe launch rate.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Endeavour_01 on 01/07/2016 03:49 PM
After going through the document I noticed that it is more than a year old (dates back to 2014). I am wondering if the 2027 number for SLS-5 is the result of the earlier once every 2 year flight rate (like Chalmer said). That anticipated flight rate seems to have changed in the last year.


You cant just wave away what you think is DDT&E of 1.15 Billion. That cost is still there and very much part of the cost of the SLS. Only it is not part of the marginal cost.

I wasn't "waving the cost away." My point was that the cost of new RS-25 engines will not break the bank for flight costs like a number of people have said.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Prettz on 01/07/2016 04:42 PM
Original Aerojet Rocketdyne release:

http://ir.aerojetrocketdyne.com/releasedetail.cfm?ReleaseID=944137

 "The RS-25 engines designed under this new contract will be expendable with significant affordability improvements over previous versions," added Jim Paulsen, vice president, Program Execution, Advanced Space & Launch Programs at Aerojet Rocketdyne. "This is due to the incorporation of new technologies, such as the introduction of simplified designs; 3-D printing technology called additive manufacturing; and streamlined manufacturing in a modern, state-of-the-art fabrication facility."

'The new engines will incorporate simplified, yet highly reliable, designs to reduce manufacturing time and cost. For example, the overall engine is expected to simplify key components with dramatically reduced part count and number of welds. At the same time, the engine is being certified to a higher operational thrust level.'
It is so weird to make each of those statements when the total cost and timeline for all of this was included as part of the same release. Why should we care about simplified components and reduced welds when it's still the most expensive and complex engine in the world?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Hog on 01/07/2016 06:45 PM
The other item is that there are not just 6 engines but actually 8. 6 flight and 2 test articles for qualification testing. The 2 test articles are part of the $1.15B restart costs.

The fact that there will be new parts manufacturing (different sources and newer manufacturing methods) is a good thing even if the actual design does not change in any appreciable difference. The key is to maintain the design such that the old and new engines are interchangeable without even a software change required on the rocket side. Otherwise there would be a lot of redone engineering for the "new" engine also making it very difficult to mix on same rocket.
There are 6 new engines to be built, 4 of them will be used as flight engines, and 2 of them used for risk mitigation on the 5th SLS flight. After SLS-5, this would leave 2 flight worthy engines for SLS-6 if no other RS-25s are manufactured. Note the following bolded phrase states that new build hardware will be in the form of spare components that will support both newly certified AND residual RS-25 engines.

"The number of new flight engines to be included as part of this action is six (6). This amount of flight hardware is necessary to fulfill the needs of one SLS launch (four engines are used per launch) and two complete sets of engine hardware (i.e., the equivalent of two engines) necessary for risk mitigation in the form of spare hardware for both newly certified engines and residual RS-25 engines. This engine hardware will also serve as risk mitigation when the last four of the existing RS-25 inventory are used in support of the fourth SLS flight."

The 2 test articles you speak of are the existing Qualification Engines: QE-0525 and QE-0528 ("certification of newly produced hardware will be accomplished through the engine system hot-fire testing of select components on an existing, retrofitted RS-25 development engine.")

 Newly manufactured parts will be retrofitted on these two non-flight Qualification engines ("i.e., non-flight hardware, separate from the sixteen flight assets.") and then hot-fired.
Then once the first new stock flight engine is completed (1 of the 6 new engines), the new engine will be used for Certification of the new build RS-25s. ("Assessments of the hot-fire test data and post-test inspections will verify that the restarted production lines are consistent with historical RS-25 production and that the new engine meet the SL8 Program requirements.")

Italicized quotes are from the JUSTIFICATION FOR OTHER THAN FULL AND OPEN COMPETITION document.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/07/2016 07:56 PM
The other item is that there are not just 6 engines but actually 8. 6 flight and 2 test articles for qualification testing. The 2 test articles are part of the $1.15B restart costs.

The fact that there will be new parts manufacturing (different sources and newer manufacturing methods) is a good thing even if the actual design does not change in any appreciable difference. The key is to maintain the design such that the old and new engines are interchangeable without even a software change required on the rocket side. Otherwise there would be a lot of redone engineering for the "new" engine also making it very difficult to mix on same rocket.
There are 6 new engines to be built, 4 of them will be used as flight engines, and 2 of them used for risk mitigation on the 5th SLS flight. After SLS-5, this would leave 2 flight worthy engines for SLS-6 if no other RS-25s are manufactured. Note the following bolded phrase states that new build hardware will be in the form of spare components that will support both newly certified AND residual RS-25 engines.

"The number of new flight engines to be included as part of this action is six (6). This amount of flight hardware is necessary to fulfill the needs of one SLS launch (four engines are used per launch) and two complete sets of engine hardware (i.e., the equivalent of two engines) necessary for risk mitigation in the form of spare hardware for both newly certified engines and residual RS-25 engines. This engine hardware will also serve as risk mitigation when the last four of the existing RS-25 inventory are used in support of the fourth SLS flight."

The 2 test articles you speak of are the existing Qualification Engines: QE-0525 and QE-0528 ("certification of newly produced hardware will be accomplished through the engine system hot-fire testing of select components on an existing, retrofitted RS-25 development engine.")

 Newly manufactured parts will be retrofitted on these two non-flight Qualification engines ("i.e., non-flight hardware, separate from the sixteen flight assets.") and then hot-fired.
Then once the first new stock flight engine is completed (1 of the 6 new engines), the new engine will be used for Certification of the new build RS-25s. ("Assessments of the hot-fire test data and post-test inspections will verify that the restarted production lines are consistent with historical RS-25 production and that the new engine meet the SL8 Program requirements.")

Italicized quotes are from the JUSTIFICATION FOR OTHER THAN FULL AND OPEN COMPETITION document.
Thanks for the detailed clarification.
8 sets of new designed/new manufacturing methods parts but not 8 complete sets of engines.

Reduced parts count and increased thrust are good things moving in the right direction just not far enough for SLS's critics.

Edit: Question: How much more thrust?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 01/07/2016 08:35 PM
There weren't too many "alternatives." Here is one from long ago:

http://www.astronautix.com/engines/m1.htm
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Hog on 01/07/2016 09:46 PM
The other item is that there are not just 6 engines but actually 8. 6 flight and 2 test articles for qualification testing. The 2 test articles are part of the $1.15B restart costs.

The fact that there will be new parts manufacturing (different sources and newer manufacturing methods) is a good thing even if the actual design does not change in any appreciable difference. The key is to maintain the design such that the old and new engines are interchangeable without even a software change required on the rocket side. Otherwise there would be a lot of redone engineering for the "new" engine also making it very difficult to mix on same rocket.
There are 6 new engines to be built, 4 of them will be used as flight engines, and 2 of them used for risk mitigation on the 5th SLS flight. After SLS-5, this would leave 2 flight worthy engines for SLS-6 if no other RS-25s are manufactured. Note the following bolded phrase states that new build hardware will be in the form of spare components that will support both newly certified AND residual RS-25 engines.

"The number of new flight engines to be included as part of this action is six (6). This amount of flight hardware is necessary to fulfill the needs of one SLS launch (four engines are used per launch) and two complete sets of engine hardware (i.e., the equivalent of two engines) necessary for risk mitigation in the form of spare hardware for both newly certified engines and residual RS-25 engines. This engine hardware will also serve as risk mitigation when the last four of the existing RS-25 inventory are used in support of the fourth SLS flight."

The 2 test articles you speak of are the existing Qualification Engines: QE-0525 and QE-0528 ("certification of newly produced hardware will be accomplished through the engine system hot-fire testing of select components on an existing, retrofitted RS-25 development engine.")

 Newly manufactured parts will be retrofitted on these two non-flight Qualification engines ("i.e., non-flight hardware, separate from the sixteen flight assets.") and then hot-fired.
Then once the first new stock flight engine is completed (1 of the 6 new engines), the new engine will be used for Certification of the new build RS-25s. ("Assessments of the hot-fire test data and post-test inspections will verify that the restarted production lines are consistent with historical RS-25 production and that the new engine meet the SL8 Program requirements.")

Italicized quotes are from the JUSTIFICATION FOR OTHER THAN FULL AND OPEN COMPETITION document.
Thanks for the detailed clarification.
8 sets of new designed/new manufacturing methods parts but not 8 complete sets of engines.

Reduced parts count and increased thrust are good things moving in the right direction just not far enough for SLS's critics.

Edit: Question: How much more thrust?
No, just 6 new build engines.  I was trying to illustrate that there are six (6) RS-25's To Be Built, and that these new parts will be "back compatible" with the sixteen (16) residual/legacy/RS25-D/SSME.

There are 16 flight engines right now, these will be used on SLS-1 through SL-4.  The new contract orders 6 new build engines which will be used on SLS-5 with 2 flight engines left over in case of issues with the SLS-5s engines.(aka: risk mitigation)


The two Development engines(0525 and 0528) are already in existence and have been used for testing at Stennis for years.

Here is a list of ALL RS-25 engines currently in running condition.

Block II/RS25D Engines with flight experience (listed with last mission flown)
1)  2044  STS-133
2)  2045  STS-135
3)  2047  STS-135
4)  2048  STS-133
5)  2050  STS-120
6)  2051  STS-132
7)  2052  STS-132
8)  2054  STS-131
9)  2056  STS-121
10) 2057 STS-134
11) 2058 STS-133
12) 2059 STS-134
13) 2060 STS-135
14) 2061 STS-134

Unflown Block II/RS25D engines
15) 2062 (circa 2010 build)
16) 2063 (2015 build)

Development Engines Block II/RS25D (will not be flown-used for testing at Stennis)
17) 0525
18) 0528

These are the new build RS-25s (we will know them as RS-25e's)
19) TBB(To Be Built)
20) TBB
21) TBB
22) TBB
23) TBB
24) TBB



xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Existing RS-25's will be run at 109% RPL and the new build RS-25's will be run at 111%.  Check out the supplied diagram for thrust numbers.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/07/2016 10:12 PM
The new contract orders 6 new build engines which will be used on SLS-5 with 2 flight engines left over in case of issues with the SLS-5s engines.(aka: risk mitigation)

The part i have bolded is not exactly correct according to the document. As i wrote earlier with quotes, the two first engines (of the six) are not flight engines but what they call MTBF engines or "mean time between failure".

They will be used as parts (among other things) to secure robustness for the SLS-4 engines which were put together themselves (at least two of them) from spare parts. And also to secure robustness of the newly build engines since most existing spareparts were used,as i read it, for the last of the 16 current engines.

So there wont be 2 engines from this batch "left over" after SLS-5. Not according to plan at least.

So for an SLS-6 they would need to order 4 new engines.


Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lee Jay on 01/08/2016 12:23 AM
This is a bit unbelievable to me.  This is an already-designed, already-proven engine with a pedigree of production.  Assuming people have a total cost of $150k a year, $1.16B is the work of 1,100 people for 7 years.  How the heck could it possibly take that much work to restart production, even including a bunch of value engineering?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: SLC17A5 on 01/08/2016 12:39 AM
"The longest suicide note in history" is overused as a phrase, but...
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Khadgars on 01/08/2016 03:02 AM
This is a bit unbelievable to me.  This is an already-designed, already-proven engine with a pedigree of production.  Assuming people have a total cost of $150k a year, $1.16B is the work of 1,100 people for 7 years.  How the heck could it possibly take that much work to restart production, even including a bunch of value engineering?

Why is it that when every SLS article is written we get ridiculous comments like this all day.  >:(
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: QuantumG on 01/08/2016 03:06 AM
Seems like a reasonable question.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: sdsds on 01/08/2016 04:19 AM
Is there, by any reasonable measure of complexity, a rocket engine more complex than RS-25?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Steven Pietrobon on 01/08/2016 04:47 AM
The other item is that there are not just 6 engines but actually 8. 6 flight and 2 test articles for qualification testing. The 2 test articles are part of the $1.15B restart costs.

The bar chart only shows six engines, two mean time between failure (MTBF) and four Flight.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 01/08/2016 12:39 PM
The new contract orders 6 new build engines which will be used on SLS-5 with 2 flight engines left over in case of issues with the SLS-5s engines.(aka: risk mitigation)

The part i have bolded is not exactly correct according to the document. As i wrote earlier with quotes, the two first engines (of the six) are not flight engines but what they call MTBF engines or "mean time between failure".

They will be used as parts (among other things) to secure robustness for the SLS-4 engines which were put together themselves (at least two of them) from spare parts. And also to secure robustness of the newly build engines since most existing spareparts were used,as i read it, for the last of the 16 current engines.

So there wont be 2 engines from this batch "left over" after SLS-5. Not according to plan at least.

So for an SLS-6 they would need to order 4 new engines.

How is this possible if the RS-25E is being redesigned to reduce part count?  Seems to me, if you wanted to cover the existing inventory, you'd restart RS-25D production.

Edit: Could be that the 'spare parts' are entire engines -- something fails on one of the sixteen, and a new $57M 'spare part' is substituted...
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 01/08/2016 12:45 PM
This is a bit unbelievable to me.  This is an already-designed, already-proven engine with a pedigree of production.  Assuming people have a total cost of $150k a year, $1.16B is the work of 1,100 people for 7 years.  How the heck could it possibly take that much work to restart production, even including a bunch of value engineering?

Why is it that when every SLS article is written we get ridiculous comments like this all day.  >:(

When you start a discussion with a false premise (in this case, that there is a logical reason that we are building the current SLS design), then you are expected to reach all sorts of false conclusions (in this case, that there is justification for NASA to apply cutting edge technology to one of the world's best engines to make it more expendable).

If we simply discuss the current design of SLS as a jobs program, the latest decision is totally justifiable.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/08/2016 01:12 PM
Government program logic: "We have to invest more money so that we are able to throw it away each time we use it"... :o
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AS-503 on 01/08/2016 01:13 PM
The Space Shuttle Main Engine (also known as SSME and RS-25) is an amazing piece of engineering.
That said, I don't believe the current program of record with NASA and SLS is the optimal path.

I have attached the complete "Space Shuttle Main Engine - The First Ten Years" to this post.
It's a fascinating insight into design and manufacturing decisions as well as difficulties with engine timings and controls.

Its still troubling to think that all of those historic STS engines taken from the now retired orbiters are scheduled to be dumped into the Atlantic Ocean after pushing SLS uphill.

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/08/2016 01:20 PM
The Space Shuttle Main Engine (also known as SSME and RS-25) is an amazing piece of engineering.
That said, I don't believe the current program of record with NASA and SLS is the optimal path.

I have attached the complete "Space Shuttle Main Engine - The First Ten Years" to this post.
It's a fascinating insight into design and manufacturing decisions as well as difficulties with engine timings and controls.

Its still troubling to think that all of those historic STS engines taken from the now retired orbiters are scheduled to be dumped into the Atlantic Ocean after pushing SLS uphill.
Nice, Thanks! :)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: notsorandom on 01/08/2016 01:49 PM
There is the accusation that NASA is paying for new technologies to just to make the engine expendable. However many of the upgrades may not have anything to do with making the engine expendable, just simpler to manufacture. For example I remember the tube they 3D printed on the J-2X engine. It was just a curved U shape metal tube but the old way of making it involved many separate metal pieces and required a skilled welder to join them all. That's likely a change that would be made to any engine if one were looking at how it were manufactured. There is going to be a major reduction in parts count so I suspect many of the things they will change during the RS-25 restart are like that. If expendable or reusable, those types of upgrades to manufacturing would likely still be there.  Had the Shuttles kept flying and we saw blocks III and IV of the SSME I bet many of the currently proposed upgrades would still be done for the reusable version.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/08/2016 01:56 PM
There is the accusation that NASA is paying for new technologies to just to make the engine expendable. However many of the upgrades may not have anything to do with making the engine expendable, just simpler to manufacture. For example I remember the tube they 3D printed on the J-2X engine. It was just a curved U shape metal tube but the old way of making it involved many separate metal pieces and required a skilled welder to join them all. That's likely a change that would be made to any engine if one were looking at how it were manufactured. There is going to be a major reduction in parts count so I suspect many of the things they will change during the RS-25 restart are like that. If expendable or reusable, those types of upgrades to manufacturing would likely still be there.  Had the Shuttles kept flying and we saw blocks III and IV of the SSME I bet many of the currently proposed upgrades would still be done for the reusable version.
You may have a point, but the Shuttle had a assigned mission, SLS doesn't...
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AS-503 on 01/08/2016 02:31 PM
There is the accusation that NASA is paying for new technologies to just to make the engine expendable. However many of the upgrades may not have anything to do with making the engine expendable, just simpler to manufacture. For example I remember the tube they 3D printed on the J-2X engine. It was just a curved U shape metal tube but the old way of making it involved many separate metal pieces and required a skilled welder to join them all. That's likely a change that would be made to any engine if one were looking at how it were manufactured. There is going to be a major reduction in parts count so I suspect many of the things they will change during the RS-25 restart are like that. If expendable or reusable, those types of upgrades to manufacturing would likely still be there.  Had the Shuttles kept flying and we saw blocks III and IV of the SSME I bet many of the currently proposed upgrades would still be done for the reusable version.

Some of the 60s era welding on those engines (and stages) is amazing. Modern manufacturing would surely eliminate most of the welds from those older designs.

I have attached various photos that show the extensive welds on the J-2 from the rocket garden at KSC circa 2005. Of interest is the gas generator exhaust/duct manifold. The F1 also had a high part/weld count in the same area. 
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: notsorandom on 01/08/2016 03:03 PM
Some of the 60s era welding on those engines (and stages) is amazing. Modern manufacturing would surely eliminate most of the welds from those older designs.

I have attached various photos that show the extensive welds on the J-2 from the rocket garden at KSC circa 2005. Of interest is the gas generator exhaust/duct manifold. The F1 also had a high part/weld count in the same area.
Here is the link to the J-2X blog post about 3d printing I was talking about. https://blogs.nasa.gov/J2X/2011/02/16/post_1297869180794/
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TrueBlueWitt on 01/08/2016 04:17 PM
For RS-25 and SLS in general. Are the high costs a result of decision to go shuttle based being made 5 years too late? Or is this more attributable to Griffin's scorched earth policy when he kicked off constellation?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/08/2016 05:10 PM
For RS-25 and SLS in general. Are the high costs a result of decision to go shuttle based being made 5 years too late? Or is this more attributable to Griffin's scorched earth policy when he kicked off constellation?
No it is that this design and also that of CXP is not a clean sheet design with cost of operations being the number one design to factor. The last time NASA did a clean sheet design attempting to design to cost was Shuttle in the 1970's. NASA just doesn't have a clue as to how to do a clean sheet design, and Congress has the notion that if you use old hardware designs you can save money (maybe a little on design and development but definitely not for operations).

One of the underlying problems is NASA also as part of quality specifies how the parts are to be manufactured (using existing tooling (1980's tech) where it is available and only allowing really modern tooling if there is no other alternative). This greatly increases cost of manufacture because the contractors are not allowed to choose the cheapest and probably better quality manufacturing methods for parts and systems. All of this comes from using all those nice standards that are the legacy from STS, instead of writing new ones.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Dante80 on 01/08/2016 06:23 PM
Quote
The last time NASA did a clean sheet design attempting to design to cost was Shuttle in the 1970's. NASA just doesn't have a clue as to how to do a clean sheet design, and Congress has the notion that if you use old hardware designs you can save money (maybe a little on design and development but definitely not for operations).

NASA didn't have a mandate to do a clean sheet design with SLS. NASA certainly has the capability to do so.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/08/2016 06:44 PM
Does anyone else recall a clean sheet design proposal that didn't use shuttle hardware post STS? I can't think of anything of the top of my head. The only post STS proposal the made any sense was the strict adherence to DIRECT.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: PahTo on 01/08/2016 06:52 PM
Does anyone else recall a clean sheet design proposal that didn't use shuttle hardware post STS? I can't think of anything of the top of my head. The only post STS the made any sense was the strict adherence to DIRECT.

If anything, the mandate was to use as much STS technology/hardware as possible.  And note if it had been a strict adherence to DIRECT, we'd see 4-seg SRBs in use with a non-stretched core (notionally even flying now).  The 5-segment "requirement" came along as a result of ATK if I understand things correctly.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/08/2016 08:04 PM
We are wandering of topic.

The RS-25 comes with a large set of standards including how to make the parts. Its in those cases where the tooling is no longer available and the methods and manner in the standards can no longer be performed that new standards will have to be written for new parts and new manufacturing methods for those parts. Its the paperwork (designs, methods, QC, testing procedures, etc) that is the true legacy and also the lead weight when it comes to innovation and cost reduction.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/08/2016 08:05 PM
Does anyone else recall a clean sheet design proposal that didn't use shuttle hardware post STS? I can't think of anything of the top of my head. The only post STS the made any sense was the strict adherence to DIRECT.

If anything, the mandate was to use as much STS technology/hardware as possible.  And note if it had been a strict adherence to DIRECT, we'd see 4-seg SRBs in use with a non-stretched core (notionally even flying now).  The 5-segment "requirement" came along as a result of ATK if I understand things correctly.
Yes, but there were no new proposals using KerLox for example...
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: notsorandom on 01/08/2016 08:53 PM
We are wandering of topic.

The RS-25 comes with a large set of standards including how to make the parts. Its in those cases where the tooling is no longer available and the methods and manner in the standards can no longer be performed that new standards will have to be written for new parts and new manufacturing methods for those parts. Its the paperwork (designs, methods, QC, testing procedures, etc) that is the true legacy and also the lead weight when it comes to innovation and cost reduction.
The inclusion of new manufacturing techniques will not be limited to just those parts which cannot be made anymore. From the Aerojet Rocketdyne press release (https://www.rocket.com/article/nasa-and-aerojet-rocketdyne-sign-contract-restart-production-rs-25-engine-space-launch):
Quote
"The RS-25 engines designed under this new contract will be expendable with significant affordability improvements over previous versions," added Jim Paulsen, vice president, Program Execution, Advanced Space & Launch Programs at Aerojet Rocketdyne. "This is due to the incorporation of new technologies, such as the introduction of simplified designs; 3-D printing technology called additive manufacturing; and streamlined manufacturing in a modern, state-of-the-art fabrication facility."

The new engines will incorporate simplified, yet highly reliable, designs to reduce manufacturing time and cost. For example, the overall engine is expected to simplify key components with dramatically reduced part count and number of welds. At the same time, the engine is being certified to a higher operational thrust level.

In addition to the design simplification, ongoing Value Stream Mapping (VSM) analyses have identified significant cost and schedule benefits by eliminating inefficiencies, redundancies or waste in the production process flow. VSMs were proven effective during the shuttle program and those lessons learned are being applied to the RS-25 restart.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: iamlucky13 on 01/08/2016 11:57 PM
Does anyone else recall a clean sheet design proposal that didn't use shuttle hardware post STS? I can't think of anything of the top of my head. The only post STS the made any sense was the strict adherence to DIRECT.

If anything, the mandate was to use as much STS technology/hardware as possible.  And note if it had been a strict adherence to DIRECT, we'd see 4-seg SRBs in use with a non-stretched core (notionally even flying now).  The 5-segment "requirement" came along as a result of ATK if I understand things correctly.
Yes, but there were no new proposals using KerLox for example...

When we talk about post-STS, my train of thought starts with the Exploration Systems Architecture Study.

ESAS primarily focused on several shuttle-derived and several EELV-derived launchers.

I was thinking they also threw a new, F-1 class Kero-LOx option in there for consideration, but looking back through the ESAS executive summary, it appears I was mistaken.

I don't recall any mandates that drove this focus, but there never seemed to be anybody within NASA make a strong argument for a new design, either officially or independently like the DIRECT team worked.

The executive summary reminded me, however, that cost was not the only part of the analysis. Estimated risk was given quite a bit of weight. I don't remember the detailed discussion on that, but I assume the demonstrated reliability of the RS-25, the well-attested resolution of the SRB O-ring issue, and the move away from side-stacking with an exposed TPS all were arguments in favor of shuttle-derived hardware.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/09/2016 12:38 AM
New engine controller, then a new nozzle so what's next a new combustion chamber? Throw in a couple of turbopumps and valves and we're done!
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Zed_Noir on 01/09/2016 01:21 AM
New engine controller, then a new nozzle so what's next a new combustion chamber? Throw in a couple of turbopumps and valves and we're done!

Unless they manufacture the new RS-25 more or less like the old SSME, than you are basically developing a new engine.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/09/2016 11:19 AM
The new contract orders 6 new build engines which will be used on SLS-5 with 2 flight engines left over in case of issues with the SLS-5s engines.(aka: risk mitigation)

The part i have bolded is not exactly correct according to the document. As i wrote earlier with quotes, the two first engines (of the six) are not flight engines but what they call MTBF engines or "mean time between failure".

They will be used as parts (among other things) to secure robustness for the SLS-4 engines which were put together themselves (at least two of them) from spare parts. And also to secure robustness of the newly build engines since most existing spareparts were used,as i read it, for the last of the 16 current engines.

So there wont be 2 engines from this batch "left over" after SLS-5. Not according to plan at least.

So for an SLS-6 they would need to order 4 new engines.

How is this possible if the RS-25E is being redesigned to reduce part count?  Seems to me, if you wanted to cover the existing inventory, you'd restart RS-25D production.

Edit: Could be that the 'spare parts' are entire engines -- something fails on one of the sixteen, and a new $57M 'spare part' is substituted...

The documents specifically says that "components" from the MTBF engines will be used for SLS-4. So it is not that entire engines are spares.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chalmer on 01/09/2016 12:15 PM
Question:

Who has the intellectual property rights to the RS-25 and the associated documentation? Does NASA or AJR?

Do NASA keep IPs for tech developed and produced under FAR?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Oli on 01/09/2016 01:38 PM
Does anyone else recall a clean sheet design proposal that didn't use shuttle hardware post STS? I can't think of anything of the top of my head. The only post STS proposal the made any sense was the strict adherence to DIRECT.

There's the HLLV study from 2010 which looked at a variety of configurations and their costs. There wasn't a clear winner really. The RP-1 first stage + LH2 second stage configuration had the same $/lb to TLI as SLS (though lower $/lb to LEO) and higher reliability, but also higher development cost.

Ultimately any huge rocket that launches only once every 2 years and whose development is drawn out over 20 years is going to be expensive.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/09/2016 02:18 PM
Does anyone else recall a clean sheet design proposal that didn't use shuttle hardware post STS? I can't think of anything of the top of my head. The only post STS proposal the made any sense was the strict adherence to DIRECT.

There's the HLLV study from 2010 which looked at a variety of configurations and their costs. There wasn't a clear winner really. The RP-1 first stage + LH2 second stage configuration had the same $/lb to TLI as SLS (though lower $/lb to LEO) and higher reliability, but also higher development cost.

Ultimately any huge rocket that launches only once every 2 years and whose development is drawn out over 20 years is going to be expensive.
Sort of what we got now.... ;)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: robertross on 01/09/2016 03:19 PM
Question:

Who has the intellectual property rights to the RS-25 and the associated documentation? Does NASA or AJR?

Do NASA keep IPs for tech developed and produced under FAR?

As I recall from a previous poster many years ago, AJR does
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: robertross on 01/09/2016 03:44 PM
(some background): I think my biggest objection to portions of this 'program' now, is that it was being promoted as one of the lowest cost options. The SLS leveraged existing infrastructure and components from the shuttle program to allow for many synergies to reduce cost & keep the 'industrial base' going. That was what the Senate was trying accomplish (hence the continued reference to the 'Senate Launch System' for SLS).

However, as we continue on the path of building the SLS, things seem to be diverging, especially with regards to cost (which I guess is no surprise). I think it started with the transition from 4-segment SRBs to 5-segment SRBs, complicated with obsolete components and a move to safer non-asbestos containing items (which affected the segment castings). So far that seems on schedule, albeit a much narrower level of margin remaining.

We also had a baselined J-2X engine, which then got mothballed for various reasons. This also sucked up valuable resources (monies) diverted to Stennis for their new test stand & upgrades to the original ones for upper level/vacuum rating of engines. The one good thing to come of it though was some techniques in new manufacturing, and of the engine controller - both of which will benefit this RS-25 re-design.

The objection many have for these 'justifications' is that a good case will likely be possible at the end of the day (when SLS finally flies) is that a comparable system was likely possible using either existing capabilities (either commercial) or with a kerolox-based system (with a new engine that had the potential be used on existing and/or future commercial rockets). I know a select few who have & would argue the existing commercial rocket market, but we have certainly seen those markets look to alternatives in the wake of growing tensions with Russia, and the changing commercial market. There was also the possibility of restarting the F-1 engine program (which would have been awesome), but perhaps a big step backwards in the grand scheme of things.

See, at the end of the day: it's all political. I suppose none had a chance of making anything come of something like the the Direct proposal, as it came against its greatest opposition in the halls of power, as the machine of big business had/has too much control on their districts.

I just hope those politicians haven't doomed the program because of political decisions, as opposed to sound economic decisions. Because the money is getting tighter, and NASA budgets, even if kept steady, is actually a decrease in funds with the continued increases in salaries and other costs.

I want NASA to thrive, and since the decision was made to go with SLS, we need to ensure it survives (but not on life support). The longer this all takes, the more costly it becomes to sustain that industrial base, putting square in the cross-hairs of budgetary reviews by those who take office in the upcoming elections, and those to come.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 01/09/2016 03:53 PM
NASA just doesn't have a clue as to how to do a clean sheet design, and Congress has the notion that if you use old hardware designs you can save money

Disagree on both counts.

I would think that engineers capable of designing SLS are also capable of designing a clean sheet rocket.

Congress isn't interested in saving money by using old hardware; it wants to spend money on the same old hardware in the same states and districts as pork.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Oli on 01/09/2016 04:15 PM
The situation has changed in the past 5 years.

SEP reduces the mass you have to put into orbit. Look at NASA's Evolvable Mars Campaign. You can do it with 2 SLS launches per year. And that's without using SEP for the LEO-L2 transfer!!

Then we'll have Falcon Heavy and Vulcan 56x who can put 35-45mt into LEO without upgrades. And SpaceX has made launch cheaper.

Bottom line: Heavy lift is not really needed anymore. In my opinion.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Patchouli on 01/09/2016 04:24 PM
We could be building F1's if we were going to go resurrecting hardware.
Maybe using a kerolox first stage and building something similar to the old Saturn V might actually be more cost effective since it reduces the requirements on the sustainer stage.




 :o This is the production process I imagine for a 5 year build: (see image) It's no wonder the surviving RS-25's are treated like precious commodities.

(Meanwhile, another domestic liquid engine producer builds over 100 engines per year)

Keep in mind the Merlin is a much smaller and simpler engine then the  SSME.
It's is like comparing a LS engine out of a Camaro or truck to a Bugatti Veron W16.
If you stuck a SSME in a stretched S-IVB you would have a Delta II class SSTO.
Still I expected a switch to channel wall construction to have made production a lot easier and cheaper.

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: robertross on 01/09/2016 05:22 PM
The situation has changed in the past 5 years.

SEP reduces the mass you have to put into orbit. Look at NASA's Evolvable Mars Campaign. You can do it with 2 SLS launches per year. And that's without using SEP for the LEO-L2 transfer!!

Then we'll have Falcon Heavy and Vulcan 56x who can put 35-45mt into LEO without upgrades. And SpaceX has made launch cheaper.

Bottom line: Heavy lift is not really needed anymore. In my opinion.

It's not really about heavy lift, it's the diameter & volume constraints of the fairing that the elements are encapsulated in.
But that's off-topic to the debate at hand: the engines. Why a now disposable engine needs all this added re-engineering cost (and was it the best choice to begin with). Flight rate plays a huge role in this, which is ultimately up to the role SLS will play in future exploration missions (of which none have been actually agreed to), hence the continuing 'mission to nowhere' swipe.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: beb on 01/09/2016 05:53 PM
While everyone is in love with the RS-25 I've often wondered whether the J-2X would have been a better choice for the SLS sustainer engine.  I assume it would be cheaper than the 4 RS-25 and it's production line hasn't been discontinued for decades.

But then I'm not  a rocket scientist.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: rcoppola on 01/09/2016 06:06 PM
While everyone is in love with the RS-25 I've often wondered whether the J-2X would have been a better choice for the SLS sustainer engine.  I assume it would be cheaper than the 4 RS-25 and it's production line hasn't been discontinued for decades.

But then I'm not  a rocket scientist.
There are many reasons why you wouldn't use J2-X for the SLS core stage but the simplest one is that it's just not powerful enough.

https://blogs.nasa.gov/J2X/2013/08/06/inside-the-leo-doghouse-rs-25-vs-j-2x/
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Patchouli on 01/09/2016 06:14 PM
While everyone is in love with the RS-25 I've often wondered whether the J-2X would have been a better choice for the SLS sustainer engine.  I assume it would be cheaper than the 4 RS-25 and it's production line hasn't been discontinued for decades.

But then I'm not  a rocket scientist.
There are many reasons why you wouldn't use J2-X for the SLS core stage but the simplest one is that it's just not powerful enough.

https://blogs.nasa.gov/J2X/2013/08/06/inside-the-leo-doghouse-rs-25-vs-j-2x/

Actually a J2-X first stage might be workable if you're willing to accept a smaller payload.
The Saturn V INT-18 used a S-II with four Titian URMs.
http://www.astronautix.com/lvs/satint18.htm

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: edkyle99 on 01/09/2016 06:30 PM
While everyone is in love with the RS-25 I've often wondered whether the J-2X would have been a better choice for the SLS sustainer engine.  I assume it would be cheaper than the 4 RS-25 and it's production line hasn't been discontinued for decades.

But then I'm not  a rocket scientist.
That alternative was considered during the ESAS and Constellation years.  It comes with a big cost in performance.  J-2X was not designed to be at all efficient at sea-level.  The core would want to be air-started at SRB shutdown, requiring a smaller rocket.  There would need to be a half-dozen or more J-2X engines on the core, forcing use of smaller nozzle extensions at a loss of specific impulse.  Etc.

SSME production hasn't been shut down for "decades".  It ended probably about 10 or fewer years ago and was quickly replaced by J-2X R&D work, an effort that created the engine controller for the SLS RS-25.

 - Ed Kyle
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: sdsds on 01/09/2016 06:31 PM
I'm having trouble understanding the context of this new contract:

In 2006 MSFC awarded PWR contract NNM06AB13C with an value of $1.153b covering execution through the end of 2012; later changed to $1.556b covering execution through September 2014. In November 2011 this was modified by NNM06AB13C-SLS, adding execution through 2024. See: https://prod.nais.nasa.gov/eps/eps_data/148635-JA-001-001.pdf

Yet the new justification says the existing contract extends only to 2016. What's up with that?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Patchouli on 01/09/2016 06:37 PM
While everyone is in love with the RS-25 I've often wondered whether the J-2X would have been a better choice for the SLS sustainer engine.  I assume it would be cheaper than the 4 RS-25 and it's production line hasn't been discontinued for decades.

But then I'm not  a rocket scientist.
That alternative was considered during the ESAS and Constellation years.  It comes with a big cost in performance.  J-2X was not designed to be at all efficient at sea-level.  The core would want to be air-started at SRB shutdown, requiring a smaller rocket.  There would need to be a half-dozen or more J-2X engines on the core, forcing use of smaller nozzle extensions at a loss of specific impulse.  Etc.

SSME production hasn't been shut down for "decades".  It ended probably about 10 or fewer years ago and was quickly replaced by J-2X R&D work, an effort that created the engine controller for the SLS RS-25.

 - Ed Kyle

The INT-18 gives some insight into the performance which was around 80tons with a J-2 upper stage.
A J-2X SLS may be closer to 90 to 100 tons as the advanced solids are much better then the UA1207 and the tanks should be more mass efficient.
But it will fall short of the 150 ton mark set by congress.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Oli on 01/09/2016 07:28 PM
While everyone is in love with the RS-25 I've often wondered whether the J-2X would have been a better choice for the SLS sustainer engine.  I assume it would be cheaper than the 4 RS-25 and it's production line hasn't been discontinued for decades.

But then I'm not  a rocket scientist.
That alternative was considered during the ESAS and Constellation years.  It comes with a big cost in performance.  J-2X was not designed to be at all efficient at sea-level.  The core would want to be air-started at SRB shutdown, requiring a smaller rocket.  There would need to be a half-dozen or more J-2X engines on the core, forcing use of smaller nozzle extensions at a loss of specific impulse.  Etc.

SSME production hasn't been shut down for "decades".  It ended probably about 10 or fewer years ago and was quickly replaced by J-2X R&D work, an effort that created the engine controller for the SLS RS-25.

 - Ed Kyle

The Saturn V first stage was staging at ~2.7km/s, which seems to be within reasonable range of what modern solid boosters can do.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: sdsds on 01/10/2016 01:50 AM
Current engine lines of AJR:
RS25 restarting 2/yr at $57M per engine
RS68A ~9/yr dropping to only 3/yr in 2018-2019 at ~$20M per engine
RL-10 ~10/yr increasing by 2/yr for EUS in 2017 and then possibly dropping to only 2 in 2022 if ULA decides to use a different engine for ACES at $10M per engine

AJR also has the USAF "hydrocarbon boost" work. My understanding is that the technology demonstrator engine for that will, like RS-25, have both dual slow-speed boost pumps and dual high-speed main pumps, driven by an oxygen-rich pre-burner and turbine.

Either the engine that comes out of that program, or almost equivalently Raptor, will change the landscape for SLS lift-off propulsion. Personally I don't see solid boost phase propulsion surviving the inevitable downselect. But RS-25 could survive in its sustainer role.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/10/2016 03:41 PM
While everyone is in love with the RS-25 I've often wondered whether the J-2X would have been a better choice for the SLS sustainer engine.  I assume it would be cheaper than the 4 RS-25 and it's production line hasn't been discontinued for decades.

But then I'm not  a rocket scientist.
That alternative was considered during the ESAS and Constellation years.  It comes with a big cost in performance.  J-2X was not designed to be at all efficient at sea-level.  The core would want to be air-started at SRB shutdown, requiring a smaller rocket.  There would need to be a half-dozen or more J-2X engines on the core, forcing use of smaller nozzle extensions at a loss of specific impulse.  Etc.

SSME production hasn't been shut down for "decades".  It ended probably about 10 or fewer years ago and was quickly replaced by J-2X R&D work, an effort that created the engine controller for the SLS RS-25.

 - Ed Kyle

The Saturn V first stage was staging at ~2.7km/s, which seems to be within reasonable range of what modern solid boosters can do.
My mind wonders about a Saturn V first stage and Shuttle tank 2nd stage RS-25 powered. If we only didn't discard previously designed hardware fixtures and tooling...
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: kch on 01/10/2016 04:07 PM
While everyone is in love with the RS-25 I've often wondered whether the J-2X would have been a better choice for the SLS sustainer engine.  I assume it would be cheaper than the 4 RS-25 and it's production line hasn't been discontinued for decades.

But then I'm not  a rocket scientist.
That alternative was considered during the ESAS and Constellation years.  It comes with a big cost in performance.  J-2X was not designed to be at all efficient at sea-level.  The core would want to be air-started at SRB shutdown, requiring a smaller rocket.  There would need to be a half-dozen or more J-2X engines on the core, forcing use of smaller nozzle extensions at a loss of specific impulse.  Etc.

SSME production hasn't been shut down for "decades".  It ended probably about 10 or fewer years ago and was quickly replaced by J-2X R&D work, an effort that created the engine controller for the SLS RS-25.

 - Ed Kyle

The INT-18 gives some insight into the performance which was around 80tons with a J-2 upper stage.
A J-2X SLS may be closer to 90 to 100 tons as the advanced solids are much better then the UA1207 and the tanks should be more mass efficient.
But it will fall short of the 150 ton mark set by congress.

150 tons?  Hardly.  Try 130 (and then NASA mangled that into tonnes -- bet they're regretting that cutesy little trick about now).
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 01/10/2016 10:19 PM
My mind wonders about a Saturn V first stage and Shuttle tank 2nd stage RS-25 powered. If we only didn't discard previously designed hardware fixtures and tooling...

Hasn't CxP and SLS taught us enough about the dangers of clinging to old tooling?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AS-503 on 01/10/2016 10:28 PM
My mind wonders about a Saturn V first stage and Shuttle tank 2nd stage RS-25 powered. If we only didn't discard previously designed hardware fixtures and tooling...

Hasn't CxP and SLS taught us enough about the dangers of clinging to old tooling?

Yep, and let's not forget the "dangers" of new tooling!  :o
As in Michoud's vertical weld tool for SLS tanks screw-up.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/11/2016 12:05 AM
My mind wonders about a Saturn V first stage and Shuttle tank 2nd stage RS-25 powered. If we only didn't discard previously designed hardware fixtures and tooling...

Hasn't CxP and SLS taught us enough about the dangers of clinging to old tooling?
(Let's set aside the current commercial success for a moment, see I did't even have to say the name...) ;D I see the situation as a lack of foresight and implementation from the 70's on... It's more of a policy problem than an engineering problem. The Russians with all their woes managed a unbroken launch effort and space presence.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: robertross on 01/11/2016 01:17 AM
My mind wonders about a Saturn V first stage and Shuttle tank 2nd stage RS-25 powered. If we only didn't discard previously designed hardware fixtures and tooling...

Hasn't CxP and SLS taught us enough about the dangers of clinging to old tooling?
(Let's set aside the current commercial success for a moment, see I did't even have to say the name...) ;D I see the situation as a lack of foresight and implementation from the 70's on... It's more of a policy problem than an engineering problem. The Russians with all their woes managed a unbroken launch effort and space presence.

(that has also stagnated, unfortunately)

I think innovation is extremely important. What I still believe the key issues are:

1) Political ambitions getting in the way of a true space 'program'
2) Lack of direction
3) Lack of proper oversight
4) Insufficient funding to deliver on the politically-requested goals, compromised by the aforementioned issues
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/11/2016 01:37 AM
My mind wonders about a Saturn V first stage and Shuttle tank 2nd stage RS-25 powered. If we only didn't discard previously designed hardware fixtures and tooling...

Hasn't CxP and SLS taught us enough about the dangers of clinging to old tooling?
(Let's set aside the current commercial success for a moment, see I did't even have to say the name...) ;D I see the situation as a lack of foresight and implementation from the 70's on... It's more of a policy problem than an engineering problem. The Russians with all their woes managed a unbroken launch effort and space presence.

(that has also stagnated, unfortunately)

I think innovation is extremely important. What I still believe the key issues are:

1) Political ambitions getting in the way of a true space 'program'
2) Lack of direction
3) Lack of proper oversight
4) Insufficient funding to deliver on the politically-requested goals, compromised by the aforementioned issues

3) Lack of proper oversight
Is that too little or is that too much?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 01/11/2016 05:13 AM
My mind wonders about a Saturn V first stage and Shuttle tank 2nd stage RS-25 powered. If we only didn't discard previously designed hardware fixtures and tooling...

Hasn't CxP and SLS taught us enough about the dangers of clinging to old tooling?
(Let's set aside the current commercial success for a moment, see I did't even have to say the name...) ;D

Would you care to clarify your comment? What current commercial success held on to tooling that had been unused for a long time?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Rocket Science on 01/11/2016 02:09 PM
My mind wonders about a Saturn V first stage and Shuttle tank 2nd stage RS-25 powered. If we only didn't discard previously designed hardware fixtures and tooling...

Hasn't CxP and SLS taught us enough about the dangers of clinging to old tooling?
(Let's set aside the current commercial success for a moment, see I did't even have to say the name...) ;D

Would you care to clarify your comment? What current commercial success held on to tooling that had been unused for a long time?
I was meaning "the not to be over uttered name SpaceX" in every thread on NSF... ;D (As in before they existed, taking them out of the equation. Nothing to do with tooling use. Sorry for the lack of clarity.)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 01/11/2016 03:25 PM
We could be building F1's if we were going to go resurrecting hardware.
Maybe using a kerolox first stage and building something similar to the old Saturn V might actually be more cost effective since it reduces the requirements on the sustainer stage.




 :o This is the production process I imagine for a 5 year build: (see image) It's no wonder the surviving RS-25's are treated like precious commodities.

(Meanwhile, another domestic liquid engine producer builds over 100 engines per year)

Keep in mind the Merlin is a much smaller and simpler engine then the  SSME.
It's is like comparing a LS engine out of a Camaro or truck to a Bugatti Veron W16.
If you stuck a SSME in a stretched S-IVB you would have a Delta II class SSTO.
Still I expected a switch to channel wall construction to have made production a lot easier and cheaper.

Are you arguing against throwing four Bugatti Veron W16s away per launch is preferable?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 01/11/2016 04:11 PM
Comparing the cost of a kerolox system to a hydrolox system you must adjust for the difference in ISP.

So a M1D+ based system would need an extra engine to lift the 43% more prop needed or a total of 4 engines to equal 1 SSME to lift the same weight to the same delta V. But 4 MIDs cost at most $8M total to the SSME cost of $57M. Somewhere the build to cost that was supposed to happen has only been given lip service in favor of build to appease congressmen.

Edit added: BTW in comparison of build to cost designs, if a kerolox side boosters had been used (basiclly something like 4 F9 1st stages, 2 on each side) the 4 RS-25 could have been replaced in the design with 4 RS-68A's to still achieve the same payload capability (must adjust for differences in ISP so more thrust is needed by the RS-68A to get to the same payload 700klbf vs 500klbf). The key here is that the costs all around is this LV would have been very low cost compared to the SLS as designed. There were options to achieve the payload goal for significantly cheaper prices but politically they were not options allowed to be chosen. This also is what killed the CXP because of shoehorning systems (SRB's) into something they were not made to do.

Further we know that there are many engines out there which could have been used in a design that would have resulted in a cheaper system but that was not the goal of this design :'(
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Mark S on 01/11/2016 05:24 PM
Simple solution: Keep the RS-25s as they are, (reusable), and fly the SLS core back to the pad. You know, like those other guys.

Of course, you would want the core to use up it's prop before it got to orbit, so you would probably need to add that 5th engine. And some hefty landing legs. And therefore the EUS as currently envisioned would be too small, so it would have to be redesigned. And its four RL-10s would be too weak, so change them back to two J2Xs. Then you would need a separate EDS for TLI, so go back to the original CPS plan. And you would need a big flat space for the returning SLS core stage to aim at. And the logistics to get it back to the VAB after it landed.      And VOILA, problem solved!

Okay, maybe not so simple. :)

Mark S.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: DaveS on 01/11/2016 05:41 PM
Simple solution: Keep the RS-25s as they are, (reusable), and fly the SLS core back to the pad. You know, like those other guys.

Of course, you would want the core to use up it's prop before it got to orbit, so you would probably need to add that 5th engine. And some hefty landing legs. And therefore the EUS as currently envisioned would be too small, so it would have to be redesigned. And its four RL-10s would be too weak, so change them back to two J2Xs. Then you would need a separate EDS for TLI, so go back to the original CPS plan. And you would need a big flat space for the returning SLS core stage to aim at. And the logistics to get it back to the VAB after it landed.      And VOILA, problem solved!

Okay, maybe not so simple. :)

Mark S.

The problem is that the RS-25's are not restartable. They have a very tight start box and rely on GSE to get the pressures/temperatures inside the start box. This is why the original Crew Launch Vehicle (before it got named Ares 1) upper stage switched to J2X, the SSME just isn't restartable and they wanted engine commonality with the Cargo Launch Vehicle (Ares V). Original design for the CLV was 4 segment SRM first stage and SSME upper stage.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: notsorandom on 01/11/2016 05:43 PM
Or just do what has been proposed for a SD-HLV many times in the last 4 decades and put the engines in a recoverable pod and snatch them up in the Indian Ocean. During the proposal to the Augustine committee of the Not Shuttle-C concept John Shannon did say that the cost to reuse the RS-25 was basically the same as the cost to build a new one. If that still holds true then building new ones seems like less of a hassle than trying to make SLS's engine recoverable.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Patchouli on 01/12/2016 01:51 AM
Or just do what has been proposed for a SD-HLV many times in the last 4 decades and put the engines in a recoverable pod and snatch them up in the Indian Ocean. During the proposal to the Augustine committee of the Not Shuttle-C concept John Shannon did say that the cost to reuse the RS-25 was basically the same as the cost to build a new one. If that still holds true then building new ones seems like less of a hassle than trying to make SLS's engine recoverable.

If the build time for the engine is five years then reusing them might be the best option to get a reasonable flight rate.
Instead of the Indian Ocean maybe try to bring them down in Australia.
This might be doable by enclosing the engines in a small lifting body type vehicle.
The other option ARJ needs to figure out have to speed up the process such as moving finial assembly to another building allowing more room for engines to be in various stages of assembly.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: pippin on 01/12/2016 02:08 AM
Why should they speed up anything? Takes them five years, engines are needed in 7 at earliest, so what's the problem?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MKremer on 01/12/2016 04:56 AM
Or just do what has been proposed for a SD-HLV many times in the last 4 decades and put the engines in a recoverable pod and snatch them up in the Indian Ocean. During the proposal to the Augustine committee of the Not Shuttle-C concept John Shannon did say that the cost to reuse the RS-25 was basically the same as the cost to build a new one. If that still holds true then building new ones seems like less of a hassle than trying to make SLS's engine recoverable.
There's no tests or studies on what immersion in salt water does to the RS-25 materials and components (both external and internal). How much time and how many millions of dollars are you willing to expend for comprehensive tests/studies, and then additional time (and more millions of dollars) to R&D the necessary changes and rebuilding to make immersion (splashdown) recovery feasible?

That time and money can be better spent just building more cost-effective expendable engines for one or maybe two flights a year.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: sdsds on 01/12/2016 06:33 AM
There's essentially zero chance the SLS program will ever attempt recovery of RS-25 engines. In the face of the coming hydrocarbon boost engines the only thing that could keep RS-25 in production would be if AJR somehow managed substantial cost reductions, and at the same time some mysterious finger on the scale kept alive the "requirement" of solid rocket boosters.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Oli on 01/12/2016 11:57 AM
There's essentially zero chance the SLS program will ever attempt recovery of RS-25 engines. In the face of the coming hydrocarbon boost engines the only thing that could keep RS-25 in production would be if AJR somehow managed substantial cost reductions, and at the same time some mysterious finger on the scale kept alive the "requirement" of solid rocket boosters.

SLS is designed for the RS-25, you can't just switch engines. According to some knowledgable people here the solids are pretty much a given as well, for reasons I cannot remember (I think it has something to do with infrastructure).

There's also the question whether NASA would want ~16 staged combustion engines on its vehicle (assuming 6 BE-4 class engines for each booster).
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 01/12/2016 12:34 PM
There's essentially zero chance the SLS program will ever attempt recovery of RS-25 engines. In the face of the coming hydrocarbon boost engines the only thing that could keep RS-25 in production would be if AJR somehow managed substantial cost reductions, and at the same time some mysterious finger on the scale kept alive the "requirement" of solid rocket boosters.

We all realize that this is a fact of life with SLS, so we'll have to deal with it as long as SLS exists... so let me suggest a different approach.

Let's take the existing 16 RS-25Ds to appropriate museums around the country -- where they belong for the fine technology that they are, and take Boeing, LM, ATK, AJR, and their lobbyists/in-pocket Legislators and dump them in the Atlantic. 

Then NASA can get back to the business for which they are uniquely qualified.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: notsorandom on 01/12/2016 02:15 PM
Or just do what has been proposed for a SD-HLV many times in the last 4 decades and put the engines in a recoverable pod and snatch them up in the Indian Ocean. During the proposal to the Augustine committee of the Not Shuttle-C concept John Shannon did say that the cost to reuse the RS-25 was basically the same as the cost to build a new one. If that still holds true then building new ones seems like less of a hassle than trying to make SLS's engine recoverable.
There's no tests or studies on what immersion in salt water does to the RS-25 materials and components (both external and internal). How much time and how many millions of dollars are you willing to expend for comprehensive tests/studies, and then additional time (and more millions of dollars) to R&D the necessary changes and rebuilding to make immersion (splashdown) recovery feasible?
No need to dunk them. Grab them out of the air like ULA plans with their SMART reuse plan. The engines may need to be split in to pairs to lower mass for the recovery aircraft but its a technologically doable solution. If it is worth doing is another question.
Quote
That time and money can be better spent just building more cost-effective expendable engines for one or maybe two flights a year.
That was the point I was trying to make in a round about way. The engines can be recovered. However they are not going to do so because it make more sense to just build new ones.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Hauerg on 03/01/2017 05:01 AM
Any current information about production start for NEW RS25?

(Not that I thought it would really happen.)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 03/01/2017 11:10 PM
Simple solution: Keep the RS-25s as they are, (reusable), and fly the SLS core back to the pad. You know, like those other guys.

The problem is that the RS-25's are not restartable.

There are also the problems of T/W being too high and not having a center engine. Sure, you could do two engines diagonally, but then you have even more thrust. When F9 lands, it is running 1 of 9 engines at deep throttle. Even then, T > W. Hover slams with 3 engines running at deep throttle stress the airframe. Grasshopper had to carry significant ballast to equalize T/W. SLS just isn't designed for this. With F9 it was an afterthought, but fortuitously, it worked. ITS, with 42 engines, will be well suited for landing.

With reusability now a proven possibility, all disposable S1s will soon be obsolete. SLS is simply an exercise in throwing good money after bad. It's time to embrace the new paradigm of reusability. This notion of legacy/heritage hardware was just as foolish as admirals who wanted to keep building battleships rather than carriers after Pearl Harbor. It's time to embrace progress.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Patchouli on 03/02/2017 12:23 AM
One solution is put the SSMEs in a recoverable pod.
Another bring back the TR-106 it's lower ISP than the SSME but higher thrust so things should mostly even out.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Zed_Noir on 03/02/2017 01:22 AM
Simple solution: Keep the RS-25s as they are, (reusable), and fly the SLS core back to the pad. You know, like those other guys.

The problem is that the RS-25's are not restartable.

There are also the problems of T/W being too high and not having a center engine. Sure, you could do two engines diagonally, but then you have even more thrust. When F9 lands, it is running 1 of 9 engines at deep throttle. Even then, T > W. Hover slams with 3 engines running at deep throttle stress the airframe. Grasshopper had to carry significant ballast to equalize T/W. SLS just isn't designed for this. With F9 it was an afterthought, but fortuitously, it worked. ITS, with 42 engines, will be well suited for landing.
.....

The solution seem simple in theory. Add a lower impulse restartable HydroLox engine to the SLS core in the center position. Of course you will have to add some sort of landing gears.

IIRC the low impulse engine goes by the name of BE-3. And it have a decent test program already.  ;)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/02/2017 01:59 AM
SLS core goes far too close to orbit to get back. Need a much bigger second stage for this to work at all.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Mark S on 03/02/2017 02:16 AM
Edit 2: LOL! Never mind, I just realized that I'm repeating myself from a little over a year ago, just a few posts up. Add 5th engine, recover SLS core. Carry on.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 03/02/2017 03:28 AM
SLS core goes far too close to orbit to get back. Need a much bigger second stage for this to work at all.

True. As a sustainer stage, it would burn up. The heavier S2 then requires adding more engines to the core to offset gravity losses. The thing simply does not lend itself to recovery. That needs to be part of the design requirements from the beginning. It doesn't at all work as an afterthought with this LV.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: quanthasaquality on 03/02/2017 06:15 AM
SLS core goes far too close to orbit to get back. Need a much bigger second stage for this to work at all.

yep, those hydrogen first stages with big SRBs tend to get close to orbit. Especially the Ariane 5. The Falcon 9 has a big fat second stage. If you want reuse, it is easier to reuse liquid boosters.... which is what Zenit might have become for the Soviet Energia. The Zenit would be a good candidate to try reuse.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: quanthasaquality on 03/02/2017 07:06 AM
So AR is basically developing a new engine that is also call RS-25.

Think it is like the J-2X to J-2 relationship. So the new engine should be call the RS-25X.  :P

Heh heh heh, AJR is trying to make rocket engines compatible with the rs-25, and rd-180. Sounds like something a Chinese company would be better at.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: quanthasaquality on 03/02/2017 07:30 AM
The situation has changed in the past 5 years.

SEP reduces the mass you have to put into orbit. Look at NASA's Evolvable Mars Campaign. You can do it with 2 SLS launches per year. And that's without using SEP for the LEO-L2 transfer!!

Then we'll have Falcon Heavy and Vulcan 56x who can put 35-45mt into LEO without upgrades. And SpaceX has made launch cheaper.

Bottom line: Heavy lift is not really needed anymore. In my opinion.

The RAC analysis showed that it would be difficult to have commonality with EELV sized rockets and the 130 ton 'monster rocket' Bill Nelson wanted. new or 'rebooted' rocket engines are almost a requirement for the monster rocket, unless you used 9 rd-180s, or LE-7As.

An Atlas V phase 2 heavy would have been easier.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Ben the Space Brit on 03/02/2017 09:57 AM
At the risk of thread derailment, I still think that Atlas-V Phase 2/3A should have been a lot more closely considered, even though it required buying a very, very large front-end load of RD-170s or -180s at least until AJR could be whipped into building their kerolox monster engine rather than just sticking their hand out for money. Everything about it just seemed so perfect to me!

The lesson? I suspect that some kind of large engine development and production commitment was going to be the price the USG had to pay to get legacy aerospace's cooperation for the new launcher contract. FWIW, RS-84 and RL-60 should have satisfied that but then there was ATK to satisfy, wasn't there?

Ah... politics! ::)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: bob the martian on 03/02/2017 03:00 PM
One solution is put the SSMEs in a recoverable pod.

Which would require throwing away the current booster design and starting over from scratch (or nearly so), which would basically kill the program dead (not that there's anything wrong with that).  That's not something you can just cut and weld into place.   

SLS core stage is never going to recoverable - at its proposed flight rate, it's not worth making recoverable. Assuming the program makes it past EM-1, we're going to splash the existing stockpile of SSMEs and hope that AJR can build new ones, hopefully a little more cheaply. 
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/02/2017 03:33 PM
The situation has changed in the past 5 years.

SEP reduces the mass you have to put into orbit. Look at NASA's Evolvable Mars Campaign. You can do it with 2 SLS launches per year. And that's without using SEP for the LEO-L2 transfer!!

Then we'll have Falcon Heavy and Vulcan 56x who can put 35-45mt into LEO without upgrades. And SpaceX has made launch cheaper.

Bottom line: Heavy lift is not really needed anymore. In my opinion.

The RAC analysis showed that it would be difficult to have commonality with EELV sized rockets and the 130 ton 'monster rocket' Bill Nelson wanted. new or 'rebooted' rocket engines are almost a requirement for the monster rocket, unless you used 9 rd-180s, or LE-7As.

An Atlas V phase 2 heavy would have been easier.

9 reuse-qualified engines on a booster! Who would have though of that? :)

I still don't understand why the RAC kerolox boosters got such lousy estimated performance. 6 RD-180s should put like 130t IMLEO with state of the art mass fractions and 2 J-2X.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Proponent on 03/02/2017 04:40 PM
The thing I really don't understand about the RAC study is why it was done in the first place: Congress had already passed a law that NASA build an HLV using Shuttle components to the maximum "practicable" extent.  It would have been illegal for NASA to build any of the RAC-2 or -3 vehicles barring something that made RAC-1 designs impracticable.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Ben the Space Brit on 03/02/2017 04:57 PM
It was basically written to create a technical justification for the already-set-in-stone political decision not to use EELV heritage or new-build kerolox. This is why some of the assumptions and ideas are a bit loopy: it wasn't a serious study as much as political spin masquerading as a study.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/02/2017 06:54 PM
The thing I really don't understand about the RAC study is why it was done in the first place: Congress had already passed a law that NASA build an HLV using Shuttle components to the maximum "practicable" extent.  It would have been illegal for NASA to build any of the RAC-2 or -3 vehicles barring something that made RAC-1 designs impracticable.

So why are they allowed to ditch the SRBs in order to get to the mandated 130 tons? When a 8.4m kerolox booster with large high-thrust hydrolox upper stage would have exactly the same amount of STS heritage, but be faster, cheaper, and safer?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Zed_Noir on 03/03/2017 01:15 AM
Simple solution: Keep the RS-25s as they are, (reusable), and fly the SLS core back to the pad. You know, like those other guys.

The problem is that the RS-25's are not restartable.

There are also the problems of T/W being too high and not having a center engine. Sure, you could do two engines diagonally, but then you have even more thrust. When F9 lands, it is running 1 of 9 engines at deep throttle. Even then, T > W. Hover slams with 3 engines running at deep throttle stress the airframe. Grasshopper had to carry significant ballast to equalize T/W. SLS just isn't designed for this. With F9 it was an afterthought, but fortuitously, it worked. ITS, with 42 engines, will be well suited for landing.
.....

The solution seem simple in theory. Add a lower impulse restartable HydroLox engine to the SLS core in the center position. Of course you will have to add some sort of landing gears.

IIRC the low impulse engine goes by the name of BE-3. And it have a decent test program already.  ;)

SLS core goes far too close to orbit to get back. Need a much bigger second stage for this to work at all.

Well maybe a somewhat bigger second stage. But was thinking of down range recovery of the core with a converted VLCC (aka supertanker), not return to launch site.

:) There is even a California company that does this somewhat routinely. :)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/03/2017 02:18 AM
SLS core stages at around 7.5 km/s, not 1.8 km/s. Gonna get mighty toasty on the way down.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Mark S on 03/03/2017 02:39 AM
Simple solution: Keep the RS-25s as they are, (reusable), and fly the SLS core back to the pad. You know, like those other guys.

The problem is that the RS-25's are not restartable.

There are also the problems of T/W being too high and not having a center engine. Sure, you could do two engines diagonally, but then you have even more thrust. When F9 lands, it is running 1 of 9 engines at deep throttle. Even then, T > W. Hover slams with 3 engines running at deep throttle stress the airframe. Grasshopper had to carry significant ballast to equalize T/W. SLS just isn't designed for this. With F9 it was an afterthought, but fortuitously, it worked. ITS, with 42 engines, will be well suited for landing.
.....

The solution seem simple in theory. Add a lower impulse restartable HydroLox engine to the SLS core in the center position. Of course you will have to add some sort of landing gears.

IIRC the low impulse engine goes by the name of BE-3. And it have a decent test program already.  ;)

SLS core goes far too close to orbit to get back. Need a much bigger second stage for this to work at all.

Well maybe a somewhat bigger second stage. But was thinking of down range recovery of the core with a converted VLCC (aka supertanker), not return to launch site.

:) There is even a California company that does this somewhat routinely. :)

Right. The fifth engine will increase prop consumption rate by 25% or so. The weight of the landing gear and the heavier LUS will make for slower acceleration before core staging. And a non-trivial amount of propellant will need to be retained for the boost-back and landing. These factors would combine to cause the core stage to burn out lower, slower, and closer, making recovery slightly less impossible.

For the landing and recovery, I would look into using a converted oil platform. It would be much more stable than any ship, and they are even mobile, given enough lead time.

According to this NSF thread (https://forum.nasaspaceflight.com/index.php?topic=38069.msg1406530#msg1406530) by Steven Pietrobon, a six-engine SLS Block-2 core would stage at about 4.75 km/s (~10,600mph) at an altitude of about 155km (95mi). Much slower than the 7.5 km/s that envy887 is quoting. Steven's SLS Block-2 design and analysis was geared toward enabling a single-launch SLS lunar landing mission, not towards enabling a recoverable SLS core. So it doesn't include landing legs or boost-back propellants. But it does give a general idea of how such a modified core would behave.

Regarding the use of the BE-3 instead of a center-mounted restartable RS-25, you would need to use two of them running flat-out just to get to a 1:1 T/W for the dry core mass. You would need maybe a cluster of four of them wedged in between the RS-25's, so that seems like a non-starter. A single RS-25 could throttle down to just greater than a 1:1 T/W ratio, and at max thrust (109%) would have a T/W ratio of almost 2:1. So it seems like a better fit, assuming a restartable engine.

Finally, a recovered SLS core would be pristine compared to a recovered Falcon core, due to the Falcon's sooty kerolox engines. The Falcon cores that have been recovered so far are heavily coated with soot, which may or may not impact their re-usability. A recovered SLS core would not have that problem, if it is a problem.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MATTBLAK on 03/03/2017 03:00 AM
I still think the regenerative nozzle RS-68R would have been a better idea than making more RS-25 engines. Yes, the RS-68 in any form would be heavier than the RS-25 and with about 5% percent less specific impulse. But it would have had 60% percent more thrust and after the expensive nozzle redevelopment (more than actually restarting and upgrading RS-25?!) should have had a lower unit cost through volume and simplified construction.

Weight of RS-25E x4 = 38,000 lbs
Total sea level thrust x4 = 1.67 million lbs thrust
Sea Level Isp =  366 seconds, climbing to 455 seconds in vacuum.

Weight of RS-68R x4 (approx.) = 52,000 lbs
Total sea level thrust (approx.) = 3 million lbs
Sea level Isp (approx.) = 365 seconds, climbing to 435 seconds in vacuum.

I know the RS-58R was a hypothetical engine, but it would have been a decent lower atmosphere booster engine that turned almost into a decent 'sustainer' engine at altitude, albeit one that would burn through the propellants more quickly. This higher thrust and lower altitude staging should reduce gravity losses, though this would probably require a higher propellant load upper stage powered by a pair of J-2X engines or 6x RL-10 engines instead of the 4x RL-10s currently envisaged, or 4x MB-60s. And the higher inert mass of the RS-68R engines over the RS-25s could be mostly offset by switching the Core Stage construction to Aluminum/Lithium, as per the Space Shuttle 'super lightweight' E.T.

I'm only talking about this because the SLS discussions keep on being controversial and I'm only approaching this from the viewpoint of maximizing the capability of an awesomely powerful launcher that is going to be throwing away a lot of hardware, with a sadly low flight rate envisaged. 4x RS-68R (can't use standard RS-68A because of proximity nozzle overheating, as revealed during Constellation) the envisaged 'Dark Knights' brutally powerful solid boosters and an upper stage powered by either J-2X or 6x RL-10s impresses me with the idea of getting more than 140 metric tons into Low Earth Orbit. Not shabby at all. Only 105 tons with 4x RS-25s, standard EUS and standard 5-segment boosters as we now understand it with Block 1B SLS.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/03/2017 03:00 AM
Only Mach 14, that's better but still mighty toasty. Anyone care to model the stagnation temp and heating rate on that?

Restarting RS-25 is not easy at all, even compared to adding landing engines. That's why J-2X was developed.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Mark S on 03/03/2017 03:24 AM
Only Mach 14, that's better but still mighty toasty. Anyone care to model the stagnation temp and heating rate on that?

Restarting RS-25 is not easy at all, even compared to adding landing engines. That's why J-2X was developed.

I guess J2X would make more sense as a boost-back/landing engine than BE-3. What is the level of throttling that it will support? All I can find is vacuum thrust and Isp, but not throttling percentage. At 294,000 lbf, it would have a T/W ratio of about 1.5:1 with the dry SLS core. Would that be too much for a controlled "hover-slam" landing?

And wouldn't the boost-back burn slow the core down quite a bit before re-entry? That's kind of the whole point of doing one, after all.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: sdsds on 03/03/2017 03:58 AM
An SLS-like core with 4 RS-25 and 1 J2-X. What a fascinating idea! Just imagine SLS cores returning and landing. But ... in what warehouse would NASA then leave them to rust?

;-)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 03/03/2017 04:18 AM
And wouldn't the boost-back burn slow the core down quite a bit before re-entry? That's kind of the whole point of doing one, after all.

Assuming RTLS instead of an oil platform landing, aren't three burns required: boost back, deceleration, and landing. The second burn's ΔV requirements are dependent on altitude after staging and subsequent V prior to hitting denser atmosphere. F9 stages lower and thus ΔV from gravitational acceleration is less, the deceleration burn requirements are less.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 03/03/2017 04:31 AM
Well, since they haven't actually started on EUS or tower changes yet, EUS design could still be slightly enlarged to balance the extra thrust of a J-2X placed in the middle of the core. With that extra engine and Dark Knight boosters, maybe the thing would even get the 130 mt to LEO that its supposed to do (perhaps not if retaining prop for other burns). Being able to recover the core would possibly make it less of the albatross that it currently is. Maybe Steven Pietrobon would run calcs on such an LV????

And if you build two reusable cores, then you have 8 spare reusable engines and could wait a long time before needing to build new RS-25s.

Maybe the core needs a pentagon of RS-25s, a J-2X in the center, and an even larger EUS? The mass of the extra 2 engines might balance out the J-2X's landing thrust. Build two of these and have 6 spare RS-25s.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: sdsds on 03/03/2017 08:37 AM
Despite my somewhat tongue-in-cheek reply earlier I really enjoy reading these ideas! I can't help but play devil's advocate just a bit though. So....

The secret sauce in the success of SpaceX first stage recovery was the re-entry burn. Theory kind of predicted that would work and they had the guts (and opportunities) to give it a try. No one has done that yet with a hydrolox engine, though. And there are no opportunities to give it a try. (Well, maybe with an EELV upper stage?) Note it isn't just a deceleration burn: the exhaust out in front is presumably protecting the stage from destruction.

Given what it takes to design and build an SLS-like first stage, how exactly do we first figure out if the secret-sauce hypersonic retropropulsion would work for these propellants and/or engines?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Zed_Noir on 03/03/2017 08:56 AM
@TomH

Once you decide to attempt recovering the mod SLS core in some way. That means you don't need the 130 tonnes lift. Figure how much mass can get to LEO with 4 RS-25 with the supplemental center engine plus the EUS. Then assemble your deep space stack with components around that mass figure. Since you can re-fly the mod SLS core several times a year. Maybe more frequently then the STS if there is handful of mod SLS cores in service.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Zed_Noir on 03/03/2017 09:06 AM
.....
Given what it takes to design and build an SLS-like first stage, how exactly do we first figure out if the secret-sauce hypersonic retropropulsion would work for these propellants and/or engines?

Well just build a Delta IV Heavy and replace the center core engine with a J-2X. Then do a test flight to repeat what SpaceX did with the center core minus the landing. Of course someone have to come up with the funding for such an experiment.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Ben the Space Brit on 03/03/2017 09:33 AM
The thing I really don't understand about the RAC study is why it was done in the first place: Congress had already passed a law that NASA build an HLV using Shuttle components to the maximum "practicable" extent.  It would have been illegal for NASA to build any of the RAC-2 or -3 vehicles barring something that made RAC-1 designs impracticable.

So why are they allowed to ditch the SRBs in order to get to the mandated 130 tons? When a 8.4m kerolox booster with large high-thrust hydrolox upper stage would have exactly the same amount of STS heritage, but be faster, cheaper, and safer?

The liquid boosters were put off indefinitely and I doubt that they will ever now be funded. They were just a thought experiment presented as a future path probably, once again, with the intention of convincing the advocates of liquid-fuelled boosters that these were being considered and even included when, in fact, ATK's five-segment SRBs were the only game in town.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/03/2017 11:12 AM
J-2X only has 2 throttle settings: 100% and 84%. And it would need a shorter nozzle to run at sea level. Not ideal for a landing engine.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 03/03/2017 11:21 AM
@TomH

Once you decide to attempt recovering the mod SLS core in some way. That means you don't need the 130 tonnes lift. Figure how much mass can get to LEO with 4 RS-25 with the supplemental center engine plus the EUS. Then assemble your deep space stack with components around that mass figure. Since you can re-fly the mod SLS core several times a year. Maybe more frequently then the STS if there is handful of mod SLS cores in service.

You mean, like Falcon Heavy, except using massively expensive engines?
(The poor mass fraction and high deceleration burn propellant requirement will put this beast somewhere in the FH payload range.)

Hint: If you want a reusable launcher, start with a blank sheet of paper.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 03/03/2017 01:35 PM

Hint: If you want a reusable launcher, start with a blank sheet of paper.

That excludes Spacex.  They took an expendable launcher and are trying to make it reusable.  Blue is designing theirs for reuse from day one.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Mark S on 03/03/2017 02:46 PM
@TomH

Once you decide to attempt recovering the mod SLS core in some way. That means you don't need the 130 tonnes lift. Figure how much mass can get to LEO with 4 RS-25 with the supplemental center engine plus the EUS. Then assemble your deep space stack with components around that mass figure. Since you can re-fly the mod SLS core several times a year. Maybe more frequently then the STS if there is handful of mod SLS cores in service.

You mean, like Falcon Heavy, except using massively expensive engines?
(The poor mass fraction and high deceleration burn propellant requirement will put this beast somewhere in the FH payload range.)

Hint: If you want a reusable launcher, start with a blank sheet of paper.

Well, we already know that the current SLS core is under-powered with only four RS-25 engines, thanks to Steven Pietrobon's "Fly me to the Moon" paper. Adding a fifth RS-25 and a J2X would correct that, and enable SLS to meet its 130-ton mandate easily (in conjunction with a Large Upper Stage instead of EUS).

Recoverability would be the icing on the cake, if it could be made to work. And it would show that NASA is concerned with costs, perhaps earning some good will from the Administration's budget cutters.

This has been a fun thought exercise. Cheers!
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 03/03/2017 03:09 PM

Hint: If you want a reusable launcher, start with a blank sheet of paper.

That excludes Spacex.  They took an expendable launcher and are trying to make it reusable.  Blue is designing theirs for reuse from day one.

And it excludes NASA and its industry partners.

It does for Falcon and variants as you intended to say...  it has taken a dozen or more flights to shake-out the hardware needed to achieve reusability(the landing portion, so far) -- more will probably be needed before they are done.  A dozen or more flights with SLS/RS-25s would be a bit pricey, even knowing what they know now courtesy of SpaceX's technology demonstrations.  Even then, the usable SLS payload will be so small (or negative) that it will be a dead end.

But no, it doesn't exclude SpaceX. 
They've started with a blank sheet on BFR/ITS and it will be born reusable.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Proponent on 03/03/2017 03:27 PM
So why are they allowed to ditch the SRBs in order to get to the mandated 130 tons? When a 8.4m kerolox booster with large high-thrust hydrolox upper stage would have exactly the same amount of STS heritage, but be faster, cheaper, and safer?

Sorry, I don't understand.  Do you mean "why are the not allowed to ditch the SRBs...?"  I was not aware that any 8.4-m kerolox design without SRBs could loft 130 tonnes.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Mark S on 03/03/2017 04:37 PM

Hint: If you want a reusable launcher, start with a blank sheet of paper.

That excludes Spacex.  They took an expendable launcher and are trying to make it reusable.  Blue is designing theirs for reuse from day one.
A dozen or more flights with SLS/RS-25s would be a bit pricey, even knowing what they know now courtesy of SpaceX's technology demonstrations.  Even then, the usable SLS payload will be so small (or negative) that it will be a dead end.

I'm not sure how you came to that conclusion. If Steven's six-engine SLS Block-2 design can put 140 tonnes in LEO, surely a similar core with enhancements for recovery could put more than a "small (or negative)" payload to the same orbit. It would definitely be less than 140 t, but even if it was just 95 or 100 tonnes, it would still be nearly twice that of FH.

The recovery of the core would make the reduced payload worthwhile in almost all cases. If there was an extreme need to put 140 tonnes up in one launch, then the core recovery could be skipped, allowing the full payload capacity to be utilized. You know, just like those other guys.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 03/03/2017 04:57 PM

And it excludes NASA and its industry partners.


No.  Blue Origin is among  NASA and its industry partners, just as Spacex is.

Just back off, and quit lumping all of NASA with SLS

And still after everything settles, we could still be in the same place as we were in the 90's. (stuck in LEO)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: landlubber on 03/03/2017 04:57 PM
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.

5 years to build an engine!?!?!

Imagine how many underpants you could steal in 5 years.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Space Ghost 1962 on 03/03/2017 05:23 PM
And still after everything settles, we could still be in the same place as we were in the 90's. (stuck in LEO)
... and with RIFs and no budget to do anything. Too likely. A cold time.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: notsorandom on 03/03/2017 05:38 PM
Propulsive reentry of the SLS core, if workable, is not likely to be the best way to get reusability of SLS components. As others have stated the entry velocity of the core is ~7.5 km/s which is significantly faster and hotter than Falcon 9's slow 1.5km/s. The SMART reuse concept may be the best way to get parts of the core back. There is a long history of SDHLVs that use recoverable engine pods. A HAID type inflatable heat shield might be a good improvement to that pod idea.

Any ideas on what percentage of the total cost the SRBs are? If Falcon and New Glenn show a liquid booster can be reused cheaply then replacing the SLS boosters with that sort of technology may be the best bang for the buck in terms of implementing reusability in SLS.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/03/2017 06:15 PM
So why are they allowed to ditch the SRBs in order to get to the mandated 130 tons? When a 8.4m kerolox booster with large high-thrust hydrolox upper stage would have exactly the same amount of STS heritage, but be faster, cheaper, and safer?

Sorry, I don't understand.  Do you mean "why are the not allowed to ditch the SRBs...?"  I was not aware that any 8.4-m kerolox design without SRBs could loft 130 tonnes.

SLS Block 2 nominally replaces the SRBs with advanced LRBs which have no Shuttle heritage. Or Dark Knights, which also have no Shuttle heritage.

The biggest issue with 8.4m cores is height. Replacing EUS with a 400t upper stage (roughly S-II sized) would allow SLS Block 1B to easily loft 130 tonnes, but that stack is too tall for the VAB because of the large hydrolox core. A kerolox core allows a 400t upper stage by fitting the entire core stage under the SRB thrust beam, where the LH2 tank is now.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Space Ghost 1962 on 03/03/2017 06:48 PM
Have problems with all of this w/o clarity of where to go/do better.

Congress has painted things into a real narrow, tight corner. Now you want to improve things but make them more effective? Too much needs to change to quickly on too many fronts, and possibly with less funds.

To me you're either looking at a cancellation or rescoping. Unfortunately nothing new unless to modularly rebid components such that follow on is cheaper/does more/is more reliable/has more uses.

One good thing is that these engines were from a reusable history, and they were getting to a point where costs could come down.

However, there's more than a little competition for the role, and the threshold is high.

Also, from my experience with AJR they are the most resistant to change of any here. Boeing and Lockheed will grouse about it, but in the end you can twist their arms and you'll get something.

SLS itself is the problem. By Congresses design, it vaguely inched expensively and narrowly towards flight, the fewest options for the most cost taking the longest time. So even if you accept the engines, all of the rest snaps together in the same way, and you're back on the same road as before.

So it becomes "self canceling". Which then brings on the RIFs. Which takes the budget. Which ends things.

So perhaps this NASA decision is just the recognition of a doomed program that because Congress "did it", Congress must "fix it", or Congress should let it die.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Space Ghost 1962 on 03/03/2017 07:18 PM

Hint: If you want a reusable launcher, start with a blank sheet of paper.

That excludes Spacex.  They took an expendable launcher and are trying to make it reusable.  Blue is designing theirs for reuse from day one.
Strongly disagree.

Better put was as they learned orbital launch, they agile - developed a increasingly recoverable LV and continued the process heading into reuse. And ITS is a reuse from the ground up.

Blue Origin learned engines and vehicles for reuse in waterfall. Then they began to apply it to the suborbital business with follow on to orbital business, and recently announced lunar surface cargo business.

Also look at vehicle strategy - SX keeps stretching a small vehicle larger (tank stretches, uprated engines, parallel staging,...), while BO increments up the vehicle size/scope more granularly.

Also with ITS we're talking about a single vehicle architecture with high reuse/interdependence and a very narrow CONOPS yielding a broad range into a landed/return on other bodies.

Long ranged with BO is a very different story. And with Bezos recent comments, it's beginning to sound like he wants to "deliver the pickaxes and shovels for the gold rush", not "convey the miners, pans, and rations".

So either of these can decrease NASA's dependence on "doing it all".  And neither of these really fit into NASA "hand in glove". Which would help NASA if that somehow were to work.

Finally, RS-25 engines, or even a core stage booster that uses RS-25's ... does not seem to aid in this progression.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 03/03/2017 08:06 PM

Hint: If you want a reusable launcher, start with a blank sheet of paper.

That excludes Spacex.  They took an expendable launcher and are trying to make it reusable.  Blue is designing theirs for reuse from day one.
Strongly disagree.

Better put was as they learned orbital launch, they agile - developed a increasingly recoverable LV and continued the process heading into reuse. And ITS is a reuse from the ground up.

Blue Origin learned engines and vehicles for reuse in waterfall. Then they began to apply it to the suborbital business with follow on to orbital business, and recently announced lunar surface cargo business.

Also look at vehicle strategy - SX keeps stretching a small vehicle larger (tank stretches, uprated engines, parallel staging,...), while BO increments up the vehicle size/scope more granularly.

Also with ITS we're talking about a single vehicle architecture with high reuse/interdependence and a very narrow CONOPS yielding a broad range into a landed/return on other bodies.

Long ranged with BO is a very different story. And with Bezos recent comments, it's beginning to sound like he wants to "deliver the pickaxes and shovels for the gold rush", not "convey the miners, pans, and rations".

So either of these can decrease NASA's dependence on "doing it all".  And neither of these really fit into NASA "hand in glove". Which would help NASA if that somehow were to work.

Finally, RS-25 engines, or even a core stage booster that uses RS-25's ... does not seem to aid in this progression.

There is nothing to disagree with in my statement.  I was just posting facts.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 03/03/2017 08:16 PM

Hint: If you want a reusable launcher, start with a blank sheet of paper.

That excludes Spacex.  They took an expendable launcher and are trying to make it reusable.  Blue is designing theirs for reuse from day one.

Yes, but you were also at the time fond of pointing out that F9 v1.1 (block II) was pretty much a clean sheet redesign of the F9 - (tank diameter was the only similarity) with the clear intent of vertical landing, so the truth and facts are somewhere in between.

So they changed an expandable launcher into a reusable one. But they also rebuilt it from almost scratch to do it.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: bob the martian on 03/03/2017 08:33 PM

Hint: If you want a reusable launcher, start with a blank sheet of paper.

That excludes Spacex.  They took an expendable launcher and are trying to make it reusable.  Blue is designing theirs for reuse from day one.

Yes, but you were also at the time fond of pointing out that F9 v1.1 (block II) was pretty much a clean sheet redesign of the F9 - (tank diameter was the only similarity) with the clear intent of vertical landing, so the truth and facts are somewhere in between.

So they changed an expandable launcher into a reusable one. But they also rebuilt it from almost scratch to do it.

IIRC, SpaceX has always had reusability as a goal - what changed was the method of recovery.  They were initially going to try parachute recovery of the booster, but the first few attempts showed it to not be viable, so powered landings it was.

Or did I hallucinate all of that? 
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Space Ghost 1962 on 03/03/2017 08:53 PM

Hint: If you want a reusable launcher, start with a blank sheet of paper.

That excludes Spacex.  They took an expendable launcher and are trying to make it reusable.  Blue is designing theirs for reuse from day one.
Strongly disagree.

Better put was as they learned orbital launch, they agile - developed a increasingly recoverable LV and continued the process heading into reuse. And ITS is a reuse from the ground up.

Blue Origin learned engines and vehicles for reuse in waterfall. Then they began to apply it to the suborbital business with follow on to orbital business, and recently announced lunar surface cargo business.

Also look at vehicle strategy - SX keeps stretching a small vehicle larger (tank stretches, uprated engines, parallel staging,...), while BO increments up the vehicle size/scope more granularly.

Also with ITS we're talking about a single vehicle architecture with high reuse/interdependence and a very narrow CONOPS yielding a broad range into a landed/return on other bodies.

Long ranged with BO is a very different story. And with Bezos recent comments, it's beginning to sound like he wants to "deliver the pickaxes and shovels for the gold rush", not "convey the miners, pans, and rations".

So either of these can decrease NASA's dependence on "doing it all".  And neither of these really fit into NASA "hand in glove". Which would help NASA if that somehow were to work.

Finally, RS-25 engines, or even a core stage booster that uses RS-25's ... does not seem to aid in this progression.

There is nothing to disagree with in my statement.  I was just posting facts.
You usually do. These look more like undefended opinions. You'll agree we've to much of that. Defend yours.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: rayleighscatter on 03/03/2017 09:03 PM
I'm not even sure Pepperidge Farm remembers when this thread was still about RS-25 production.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Mark S on 03/03/2017 09:19 PM
Propulsive reentry of the SLS core, if workable, is not likely to be the best way to get reusability of SLS components. As others have stated the entry velocity of the core is ~7.5 km/s which is significantly faster and hotter than Falcon 9's slow 1.5km/s.

And as I pointed out up-thread, and Steven Pietrobon showed in his paper, an SLS core with six engines and a large upper stage will use up its propellants long before it reaches 7.5 km/s. From Steven's charts, I came up with about 4.5 km/s. I'm sure Steven could provide his exact calculations. While 4.5 km/s is much faster than the Falcon core at its staging event, it's still not orbital speed. And the retro/boost-back burn would cancel most of that. A lofted trajectory would also help reduce downrange speed and distance at core staging.

Quote
The SMART reuse concept may be the best way to get parts of the core back. There is a long history of SDHLV [proposal]s that use discussed recoverable engine pods.

I don't think there have been any actual SDHLVs with recoverable engine pods flown. But I could be mistaken. :)

Finally, the solids could be recovered just like they used to be with Shuttle. If nothing else, that would delay the need to begin fabrication of new steel segment casings. Or worse, the need to develop an all-new booster (Dark Knight or LRB).

The point of all this recoverability talk is to 1) stretch out supplies of engines, 2) show the Administration that NASA is not all about throwing expensive hardware in the Atlantic, and 3) enable more SLS missions with a decimated budget, which is sure to be the case in the very near future. :(

I'm not even sure Pepperidge Farm remembers when this thread was still about RS-25 production.

Pepperidge Farm memory is notoriously unreliable in the harsh environment of space. Extreme temps, cosmic rays, etc. :)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: quanthasaquality on 03/04/2017 11:40 AM
I just keep seeing this position again, from the looks of Russia, and now SpaceX, it seems like it is important to be good at manufacturing, and pumping out large numbers of rocket engines. I guess it might also help to have a low wage workforce. The Proton, Zenit, and Angara rockets all use high performance, oxidizer rich staged combustion engines. Russia has been pumping those rocket engines out now for decades.

Presumably, kerosene oxygen oxidizer rich staged combustion engines are more difficult to manufacture than hydrogen oxygen fuel rich staged combustion engines. Russia's rd-170,180,190 series also has a higher chamber pressure than the SSME. Yet, Russia is able to manufacture the rd-180 at a reasonable price.

In the mid 90s, Marshall Space Flight Center had the idea of a low cost rocket engine, FASTRAC https://www.nasa.gov/centers/marshall/news/background/facts/fastrac.html (https://www.nasa.gov/centers/marshall/news/background/facts/fastrac.html) Ideas like a low pressure, machine manufactured turbopump, ablative nozzle, and pintle injector. The rs-68 used some of those ideas, and it was cheaper, but the Atlas V ended being the cheaper rocket. We don't know how much an American rd-180 would have ended up costing. The rs-27 was the simplified rocket engine of the 60s, with heritage from the V-2, but users of it, the Atlas and Delta rockets of the 90s, were not cheap rockets. For all the hype the Saturn V gets, it was an expensive rocket. The F-1 required a lot of skilled human labor.

Maybe the rs-25 just needs some expendable, machine, big factory love.... and a Congress willing to pay for jobs for the rs-25.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/04/2017 12:22 PM
Maybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: PahTo on 03/04/2017 03:26 PM
Maybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.

I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/04/2017 04:34 PM
Maybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.

I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".

Like Saturn 1/1b with it's 8 H-1s and perfect launch record? Or Saturn V with multiple engine failures but also a perfect launch record? Falcon 9 also hasn't had any propulsion issues leading to LOM, despite having a Merlin blow up on one flight.


Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: WulfTheSaxon on 03/04/2017 06:09 PM
Maybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.

I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".

Like Saturn 1/1b with it's 8 H-1s and perfect launch record? Or Saturn V with multiple engine failures but also a perfect launch record? Falcon 9 also hasn't had any propulsion issues leading to LOM, despite having a Merlin blow up on one flight.

Could you define “perfect launch record”? I can sort of see exempting it because it was a test flight, but Apollo 6 was a partial failure, and would have resulted in LOM had it been a crewed lunar flight…
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Flying Beaver on 03/04/2017 06:24 PM
Maybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.

I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".

Like Saturn 1/1b with it's 8 H-1s and perfect launch record? Or Saturn V with multiple engine failures but also a perfect launch record? Falcon 9 also hasn't had any propulsion issues leading to LOM, despite having a Merlin blow up on one flight.

Could you define “perfect launch record”? I can sort of see exempting it because it was a test flight, but Apollo 6 was a partial failure, and would have resulted in LOM had it been a crewed lunar flight…

Not loss of mission but at least an abort from low earth orbit. The crew would of been safe.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 03/04/2017 06:34 PM
Maybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.

I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".

Like Saturn 1/1b with it's 8 H-1s and perfect launch record? Or Saturn V with multiple engine failures but also a perfect launch record? Falcon 9 also hasn't had any propulsion issues leading to LOM, despite having a Merlin blow up on one flight.

Could you define “perfect launch record”? I can sort of see exempting it because it was a test flight, but Apollo 6 was a partial failure, and would have resulted in LOM had it been a crewed lunar flight…

Primary payload was injected in a useful orbit. It may not have reached orbit at all if the S-II used fewer engines. And it probably would have reached TLI if the S-IVB used multiple redundant engines.

The pogo on Saturn V wasn't due to engine count, and modern simulation methods are substantially better at predicting resonant modes which makes it a lot easier to design around that particular issue.

I'm really curious what "practical experience" NASA has had with many engines that leads them to think it causes more issues than it solves.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: WulfTheSaxon on 03/04/2017 06:54 PM
Maybe NASA needs to get over their irrational aversion to having many small engines on a booster, so that automated highly tooled production is worthwhile.

I don't know that it is irrational--there is some practical experience that many engines complicate things to the point the odds are there will be an "issue".

Like Saturn 1/1b with it's 8 H-1s and perfect launch record? Or Saturn V with multiple engine failures but also a perfect launch record? Falcon 9 also hasn't had any propulsion issues leading to LOM, despite having a Merlin blow up on one flight.

Could you define “perfect launch record”? I can sort of see exempting it because it was a test flight, but Apollo 6 was a partial failure, and would have resulted in LOM had it been a crewed lunar flight…

Not loss of mission but at least an abort from low earth orbit. The crew would of been safe.

How would an abort from LEO not be LOM? I didn’t say anything about LOC.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: sdsds on 03/04/2017 09:51 PM
I agree with those who feel the approach to booster design which uses a large number of engines has now been proven. It works for the booster in flight; it works for the manufacturing processes, and it works for the business model. Nine makes a particularly good number for what can be called similar redundancy!

Granted, RS-25 isn't going to be flown like that. Point taken.

That isn't sufficient to make the claim that RS-25 should be abandoned, though. It still works in flight. The manufacturing is expensive but known. The business (or at least funding) model has an extraordinary track record.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 03/05/2017 04:03 AM
How would an abort from LEO not be LOM? I didn’t say anything about LOC.

Abort from LEO would be loss of mission. He is just confusing loss of mission with loss of crew. He may be old like me; I spent 5 minutes this evening trying to put the parking garage ticket into the credit card slot.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Steven Pietrobon on 03/05/2017 04:20 AM
And as I pointed out up-thread, and Steven Pietrobon showed in his paper, an SLS core with six engines and a large upper stage will use up its propellants long before it reaches 7.5 km/s. From Steven's charts, I came up with about 4.5 km/s. I'm sure Steven could provide his exact calculations.

Core stage burn out was at 4771 m/s inertial speed.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 03/05/2017 04:36 AM
Core stage burn out was at 4771 m/s inertial speed.

Any chance you're willing to run calcs on core with 5 RS-25s and a center J-2X, two Dark Knights, and a larger US optimized to match, staging with enough prop for the core to land downrange on the (modified deep throttleable) J-2X (or RTLS on lofted trajectory)? I know, lots of unknowns, but ballpark would be nice to know.

I know this is very unlikely to actually happen, just interested in performance numbers as a hypothetical.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Steven Pietrobon on 03/05/2017 05:16 AM
Any chance you're willing to run calcs on core with 5 RS-25s and a center J-2X, two Dark Knights, and a larger US optimized to match, staging with enough prop for the core to land downrange on the (modified deep throttleable) J-2X (or RTLS on lofted trajectory)? I know, lots of unknowns, but ballpark would be nice to know.

If you're willing to pay me my consulting fee of US$100 an hour, I'll be glad to do that for you. :-)

I have simulated 5xRS-25s, Dark Knights and 2xJ-2X upper stage. That gets 144.1 t to LEO. Core stage burnout speed is 4774 m/s.
Title: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 03/05/2017 05:40 AM
I just keep seeing this position again, from the looks of Russia, and now SpaceX, it seems like it is important to be good at manufacturing, and pumping out large numbers of rocket engines.
...
In the mid 90s, Marshall Space Flight Center had the idea of a low cost rocket engine, FASTRAC https://www.nasa.gov/centers/marshall/news/background/facts/fastrac.html (https://www.nasa.gov/centers/marshall/news/background/facts/fastrac.html) Ideas like a low pressure, machine manufactured turbopump, ablative nozzle, and pintle injector. The rs-68 used some of those ideas, and it was cheaper, but the Atlas V ended being the cheaper rocket. We don't know how much an American rd-180 would have ended up costing. The rs-27 was the simplified rocket engine of the 60s, with heritage from the V-2, but users of it, the Atlas and Delta rockets of the 90s, were not cheap rockets. For all the hype the Saturn V gets, it was an expensive rocket. The F-1 required a lot of skilled human labor.

Well the spiritual (& technology) successor of FASTRAC *is* in use now - SpaceX's Merlin. It has IMO validated the thesis of the benefits of a mass produced smaller engine.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: robert_d on 03/05/2017 02:24 PM

Core stage burn out was at 4771 m/s inertial speed.

Steve,
Did you ever model a 7 RS-25 core? If so could you point to it?
I was thinking NASA could focus on Hydrogen powered vehicles, building an optimized core for 7 engines if that could be made reusable by following the flight profile of the Falcon 9 first stage. They could work on a restartable RS-25 second stage or maybe do the J2-X if that was cheaper.

I find it criminal that just as NASA had made impressive upgrades the the RS-25, they want to dump its most impressive feature, the fact that it was designed to be reusable.

Edit: I am not asking about an SLS direct replacement/upgrade. I am asking about a single core reusable booster powered by RS-25. One that would only run for about 2:30 just like the falcon 9 1st stage so it could be recovered and re-used.   
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: spacenut on 03/05/2017 03:00 PM
This has been modeled before somewhere on here.  A five core was the optimum with Dark Knights or two 5.5m core kerolox side boosters and SLS could get 150 tons to LEO or more.  This size rocket as the 70 ton version was a 3-RS-15 core and two 4 seg solids from the shuttle stack, was the lowest cost quickest version to field.  It was called Jupiter Direct.  It could have stretched tanks and 5 RS-25 core with a J2-x second stage with the two 4 seg solids and get 130 tons to LEO.  This is where the 70-130 ton Congressional mandate came from.  Instead, NASA chose to develop longer larger solids and a 4 engine core compromise to get about the current 105 ton expensive beast.  They did develop the J2-x and shut down production afterwards.  Why??, the larger solid development cost a fortune. 

Anyways a 12-15 RD-180 clean sheet booster with a two engine J2-x upper, from what I can remember got 150 tons or more to LEO.  Of course, we how have the "Russian problem" and we never developed our own manufacturing capabilities for the RD-180's. 

Seven RS-25 core would require a huge core, and probably not fit in the VAB, and be too wide for the side booster attachments.  Hydrogen takes huge tankage for boosters. 
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: robert_d on 03/05/2017 04:29 PM
So thinking a bit more: My question above asked about a 7 engine core because 1) they would fit comfortably under the 8.4 meter core and 2) there needs to be residual fuel for boostback & landing. Didn't do any math.

But I see a really rough calc. shows 9 engines might work, although there would have to be a skirt of some sort (falcon v1.0 anyone?)
calc: 3 ssme x 8.5 minutes = 25.5 engine/minutes
        9 ssme x 2.5 minutes = 22.5 engine/minutes, leaving 3.0 engine minutes for recovery.
        So a SMALLER core than SLS could work (?)
Gives 9 x 400k lbs. thrust = 3,600k lbs. at liftoff. If a second stage SSME vacuum version is too big, there are alternatives in production such as the Ariane's Vulcain or the Japanese H2, if they could be made restartable.

Mount crane on new mobile launch structure. Landing pad at approximate location of where pad 39c would have been with crawler way. Lift booster back on MLP and roll back to VAB for 1-2 month refurb.
Dump solids once and for all.
Between this far cheaper vehicle, F9 Heavy, New Glenn and Vulcan, we should have plenty of launch capacity.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 03/05/2017 04:41 PM
Core stage burn out was at 4771 m/s inertial speed.

Any chance you're willing to run calcs on core with 5 RS-25s and a center J-2X, two Dark Knights, and a larger US optimized to match, staging with enough prop for the core to land downrange on the (modified deep throttleable) J-2X (or RTLS on lofted trajectory)? I know, lots of unknowns, but ballpark would be nice to know.

I know this is very unlikely to actually happen, just interested in performance numbers as a hypothetical.

This would be interesting. 

The core would be traveling 3x the velocity (4,771 vs. ~1,500m/s) and carrying 6x the mass (dry mass at 119.9 vs. ~20tonnes without considering the mass of residual fuel, landing legs, reaction system to flip the stage, thermal insulation/shields, and grid fins or equivalent to guide the descent) of the other stage that lands downrange.  To land, we are looking > 20x the energy that has to be dissipated.  Propellant required to be carried along for recovery would be proportionately large -- both impacting velocity at staging and mass that has to be decelerated.  Upper stage delta-v also has to be used to make up the shortfall of lower staging velocity.

According to Steve's spreadsheet, this 5 RS-25/2 J2-X version achieves around 2.5% payload mass fraction.  A large proportion of that pmf (half?) would be lost to down range recovery.  There might be none of it left (negative pmf) if RTLS was used.

Also, reusability triggers other expenses:
Five RS-25s per core would reduce inventory available to three flights from four.
The RS-25E development effort would have to be shifted from making the engine more expendable, to making it more reusable (which probably would take longer)
Dark Nights would have to be developed (now, instead of in 2030)
A deep throttleable J2-X would have to be developed and go into production
A 2 engine oversized upper stage would need to be developed
Landing legs, and other hardware listed above would need to be developed
Core stage would need to be modified to accommodate these changes
A BFB (big friggin barge) would have to be developed and deployed way down range

Oh, and practice, practice, practice... to perfect that landing.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: jgoldader on 03/05/2017 05:15 PM
Am I correct in recalling from threads years ago, that a 5-engine first stage would be a major redesign because the thrust structure is very different?  And would there be cooling issues with the extra SSME, or does the RS-25's hydrogen cooling more or less make that a moot point?

If money and time were not issues, adding in a fifth engine or some sort of recoverability for the engines or entire stage might be reasonable, but given the history of the current iteration of SLS, you'd need 10+ years and many billions just for the design work, plus changes to construction hardware and maybe even GSE, etc.  I don't know that the investment is sensible.

SLS is what it is.  If you're going to use it for more than 4 (5?) flights, you need new RS-25's.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chris Bergin on 03/05/2017 10:27 PM
Post that followed had nothing to do with RS-25. If you wish to discuss other engines, please use the appropriate threads - which ain't this one if it's not RS-25.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Steven Pietrobon on 03/07/2017 07:59 AM
Did you ever model a 7 RS-25 core? If so could you point to it?

Never did seven engines. There are diminishing returns with more than six engines. You can find all my simulations at

http://www.sworld.com.au/steven/space/sls/
Title: Re: NASA defends decision to restart RS-25 production
Post by: robert_d on 03/07/2017 11:02 AM
Just reading up on the RS-25, formerly known also as the SSME. This machine is so remarkable as to almost defy belief. The complex plumbing, hydraulic system and helium system all had to come together to work flawlessly over immense temperature ranges. Also to be able to handle the phase change from liquid to gas at the appropriate places and times.

So it amazes me even more that NASA would decide that this highly complex and expensive machine could be thrown away. After the various upgrades to the block II version, it seems they were near to the goal of 60 full duration (shuttle 8.5 minutes) firings before major overhaul.

I could not find a simple description of the start-up sequence, although there were some graphs that seemed to apply. I do remember that early in Constellation they dropped the idea of making it restartable in favor of the J-2X (I think). I guess the complexity of the engine would make that expensive-to-near- impossible. Yet I will still hold out hope.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MATTBLAK on 03/07/2017 11:32 AM
Since higher thrust, regenerative nozzle RS-68s are presumably out of the question; how feasible/plausible is it that a further iteration of RS-25 could be developed that would notably upgrade the engine in thrust, whilst losing the minimal amount of specific impulse or reliability? Is running them at 115%, 120 or even 130% percent of original design thrust a realistic goal? I think I read in old Shuttle literature that original Block-1 engines were tested to destruction at close to 120% percent throttle settings?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: WulfTheSaxon on 03/07/2017 07:30 PM
Since higher thrust, regenerative nozzle RS-68s are presumably out of the question; how feasible/plausible is it that a further iteration of RS-25 could be developed that would notably upgrade the engine in thrust, whilst losing the minimal amount of specific impulse or reliability? Is running them at 115%, 120 or even 130% percent of original design thrust a realistic goal? I think I read in old Shuttle literature that original Block-1 engines were tested to destruction at close to 120% percent throttle settings?

I don’t think it’s been tested past 115% (as shown in figure 7 here (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120001440.pdf)), but I could certainly by wrong. There was once supposed to be 120% contingency capability in Block III (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000112952.pdf).
Title: Re: NASA defends decision to restart RS-25 production
Post by: Lars-J on 03/07/2017 10:30 PM
Just reading up on the RS-25, formerly known also as the SSME. This machine is so remarkable as to almost defy belief. The complex plumbing, hydraulic system and helium system all had to come together to work flawlessly over immense temperature ranges. Also to be able to handle the phase change from liquid to gas at the appropriate places and times.

So it amazes me even more that NASA would decide that this highly complex and expensive machine could be thrown away. After the various upgrades to the block II version, it seems they were near to the goal of 60 full duration (shuttle 8.5 minutes) firings before major overhaul.

Two points.
1. Just because it is an amazing technical achievement does not mean that it is good fit going forward. SLS is really a custom design around it - it makes no sense on any other existing or near future launch vehicle. The liquid propulsion market appears to be shifting towards more affordable and reusable (restart-able) engines.

2. Sunk cost fallacy. What is spent on a project is spent. If another choice makes more sense going forward, then it makes sense to put the RS-25 to pasture. (as sad as it sounds)
Title: Re: NASA defends decision to restart RS-25 production
Post by: TomH on 03/08/2017 12:06 AM
Just reading up on the RS-25, formerly known also as the SSME.

Always known as RS-25. Latest model is RS-25D. SSME is a categorization of all models. Proposed disposable replacement is designated RS-25E.

I do remember that early in Constellation they dropped the idea of making it restartable in favor of the J-2X (I think). I guess the complexity of the engine would make that expensive-to-near- impossible. Yet I will still hold out hope.
Very complex, very expensive. Not at all worth it.
Title: Re: NASA defends decision to restart RS-25 production
Post by: brickmack on 03/08/2017 01:48 PM
Always known as RS-25. Latest model is RS-25D. SSME is a categorization of all models. Proposed disposable replacement is designated RS-25E.

RS-25 was the Rocketdyne designation, SSME was what NASA called it. For SLS, NASA calls it RS-25, but no distinction is made between RS-25D and E (just remaining inventory and new production units)
Title: Re: NASA defends decision to restart RS-25 production
Post by: robert_d on 03/08/2017 03:33 PM
Very complex, very expensive. Not at all worth it.
Tom,
That's the part I am trying to pin down a bit more. What exactly is required for restart? There didn't seem to be any indications of (say) massive amounts of helium required to spin up the turbo pumps. But if spin-up is an issue, could electric spin-up be an option? If they can get a Tesla to go from 0 to 60 in 2.5 seconds, I would think it might not be inconceivable to carry enough power for 4 engine restarts in batteries. (trying to think outside the box). The main tanks would already be pressurized, so that shouldn't be an issue.

Thinking about it a bit more -
Could the COPV's required for the helium system (9 engines) be mounted inside the Hydrogen propellant tank? Helium could be loaded as cold as practical so as dense as possible. Otherwise there should be room outside, above the structural thrust structure.
Title: Re: NASA defends decision to restart RS-25 production
Post by: robert_d on 03/08/2017 04:21 PM


Two points.
1. Just because it is an amazing technical achievement does not mean that it is good fit going forward. SLS is really a custom design around it - it makes no sense on any other existing or near future launch vehicle. The liquid propulsion market appears to be shifting towards more affordable and reusable (restart-able) engines.

2. Sunk cost fallacy. What is spent on a project is spent. If another choice makes more sense going forward, then it makes sense to put the RS-25 to pasture. (as sad as it sounds)

Point 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.

Point 2 - But the RS-25 actually exists and the production line will exist, so we are NOT talking about past costs. And I am just asking if the reusability feature available can be applied to a smaller vehicle, one that would possibly be more likely to be used. This all assumes the 60 flight before overhaul became reality.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 03/08/2017 04:52 PM

That's the part I am trying to pin down a bit more. What exactly is required for restart?

The SSME was a head start engine.  As long as the temp and pressures were within the start box, it would start.  Creating the start box conditions two to three minutes after launch (and disconnect from chill down supplies) and during free fall (after staging) are a "challenge". 

. But if spin-up is an issue, could electric spin-up be an option? If they can get a Tesla to go from 0 to 60 in 2.5 seconds, I would think it might not be inconceivable to carry enough power for 4 engine restarts in batteries. (trying to think outside the box).

No, not for any real engine.  The mass of the electric motor rotor would be a drag on the engine.  And don't go into anything about clutches and gears.  Direct drive single shaft turbo pumps are the design points.  Gas spinup only requires tanks and a valve on the engine.


The J-2 carried GH2 and LO2 start tanks that would be replenished during engine operation.  But it was a gas generator engine and not staged combustion.
Title: Re: NASA defends decision to restart RS-25 production
Post by: Lars-J on 03/08/2017 04:53 PM


Two points.
1. Just because it is an amazing technical achievement does not mean that it is good fit going forward. SLS is really a custom design around it - it makes no sense on any other existing or near future launch vehicle. The liquid propulsion market appears to be shifting towards more affordable and reusable (restart-able) engines.

2. Sunk cost fallacy. What is spent on a project is spent. If another choice makes more sense going forward, then it makes sense to put the RS-25 to pasture. (as sad as it sounds)

Point 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.

Yes, it is. RS-25 was designed as a sustainer engine that burns to almost orbit. It's use in SLS is the same. Most other engines are designed to be either first or upper stage engines - and virtually no engine would do the job as well for SLS.

Point 2 - But the RS-25 actually exists and the production line will exist, so we are NOT talking about past costs. And I am just asking if the reusability feature available can be applied to a smaller vehicle, one that would possibly be more likely to be used. This all assumes the 60 flight before overhaul became reality.

Just the RS-25 existing (and its production line) does not mean that it is free, or will be a lower cost than an alternative from this point on. (the point of the sunk cost fallacy) RS-25 is saved by being such a good fit for SLS (see point 1 above) - if SLS goes away, RS-25 will as well.
Title: Re: NASA defends decision to restart RS-25 production
Post by: TomH on 03/08/2017 06:47 PM
Always known as RS-25. Latest model is RS-25D. SSME is a categorization of all models. Proposed disposable replacement is designated RS-25E.

RS-25 was the Rocketdyne designation, SSME was what NASA called it. For SLS, NASA calls it RS-25, but no distinction is made between RS-25D and E (just remaining inventory and new production units)

They call it minimal change, but it is not identical in every way, and they are not going to worry about it being able to fly 30+ times. RS-25F is simplified to be disposable and less expensive.
Title: Re: NASA defends decision to restart RS-25 production
Post by: TomH on 03/09/2017 09:08 AM


Two points.
1. Just because it is an amazing technical achievement does not mean that it is good fit going forward. SLS is really a custom design around it - it makes no sense on any other existing or near future launch vehicle. The liquid propulsion market appears to be shifting towards more affordable and reusable (restart-able) engines.

2. Sunk cost fallacy. What is spent on a project is spent. If another choice makes more sense going forward, then it makes sense to put the RS-25 to pasture. (as sad as it sounds)

Point 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.

Yes, it is. RS-25 was designed as a sustainer engine that burns to almost orbit. It's use in SLS is the same. Most other engines are designed to be either first or upper stage engines - and virtually no engine would do the job as well for SLS.

Point 2 - But the RS-25 actually exists and the production line will exist, so we are NOT talking about past costs. And I am just asking if the reusability feature available can be applied to a smaller vehicle, one that would possibly be more likely to be used. This all assumes the 60 flight before overhaul became reality.

Just the RS-25 existing (and its production line) does not mean that it is free, or will be a lower cost than an alternative from this point on. (the point of the sunk cost fallacy) RS-25 is saved by being such a good fit for SLS (see point 1 above) - if SLS goes away, RS-25 will as well.

Robert D, SLS absolutely IS designed around the RS-25, not because it is reusable, but because it is a high ISP sustainer that does not suffer proximity heating issues. SLS is devolved from Ares V which initially was to use RS-25. The designers tried to substitute RS-68 to save cost. Lower ISP and heating issues forced them to expand from 8.6m dia. to 10.0m. Endless problems cascaded and in the end they were back to RS-25 and 8.6m. SLS is a scaled down version of Ares V. There are endless threads in the archives where you can read yourself sick about the whole mess if you care to. The early RS-25 A, B, and C engines did not have the lower maintenance endurance of RS-25D. It took years upon years of continued R&D refinement to get to that engine. It is a very sophisticated engine, is labor intensive to build, and its cost reflects those facts.

You will not see RS-25D, E, or F used in another LV. You will see reusability return in Raptor and BE-4.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: ZachF on 03/12/2017 06:31 PM
What I find disturbing is that the fifth set of engines are only required in 2027, so there will only be four SLS flying in the next 11 years?  :o
I was under the impression that they'd be aiming at a somewhat higher launch cadence.  :-\

Yep, and each of those launches will come in at a nice $5 billion a pop when all is said and done...

 :o
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: ZachF on 03/12/2017 06:35 PM
To be more precise. One engine takes about 5 years to make. The factory has the capacity to start working on two new engines per year. This means that after 5 years (and assuming that each year you add two new engines to production), 2 engines are delivered for integration. And two for every year after that.

5 years to build an engine!?!?!

From the JOFOC.

(http://i.imgur.com/nG4pWAP.png)

ARJ hand builds their engines (at least, that's what I knew they did in the past).

 :o This is the production process I imagine for a 5 year build: (see image) It's no wonder the surviving RS-25's are treated like precious commodities.

(Meanwhile, another domestic liquid engine producer builds over 100 engines per year)

Remember, many of these contractors are paid in time + materials.... There is literally 0 reason whatsoever for them to increase productivity.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: robert_d on 05/08/2017 03:18 PM
So what about this,
A six RS-25D, three BE-3 booster, firing for about 2.33 minutes so that it can return. Restart on 3 BE-4's for boostback/re-entry, then one or two BE-3's for landing. Use a new BE-3 vacuum optimized engine as the upper stage engine.

Current inventory is 16 rs-25's. Enough for 2 boosters and 4 spare engines. Proposal would be to build 16 more to get potential total of 4 boosters with 8 spare engines. No modifications except for production efficiencies. Buy 18 BE-4's from B.O. for boosters and spares. Contract for 12 vacuum optimized versions for the upper stage expendable, but put out a contract for a long term second stage/depot development that anyone could bid on that would give good performance to lunar regions using the BE-3 powered second stage. That way nothing is wasted, and a returnable second stage is not required.

Since the BE-3 will be used for human suborbital, I would think the entire system could be human rated.
So could this system lift a fully fueled Orion to LEO? Could a hydrolox propellant depot be developed?

Would be ironic if the supposedly BLEO Orion stayed in LEO while a descendant of the originally intended suborbital BE-3 went on to be part of a reusable cis-lunar transfer system.

Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: envy887 on 05/08/2017 04:48 PM
So what about this,
A six RS-25D, three BE-3 booster, firing for about 2.33 minutes so that it can return. Restart on 3 BE-4's for boostback/re-entry, then one or two BE-3's for landing. Use a new BE-3 vacuum optimized engine as the upper stage engine.

Current inventory is 16 rs-25's. Enough for 2 boosters and 4 spare engines. Proposal would be to build 16 more to get potential total of 4 boosters with 8 spare engines. No modifications except for production efficiencies. Buy 18 BE-4's from B.O. for boosters and spares. Contract for 12 vacuum optimized versions for the upper stage expendable, but put out a contract for a long term second stage/depot development that anyone could bid on that would give good performance to lunar regions using the BE-3 powered second stage. That way nothing is wasted, and a returnable second stage is not required.

Since the BE-3 will be used for human suborbital, I would think the entire system could be human rated.
So could this system lift a fully fueled Orion to LEO? Could a hydrolox propellant depot be developed?

Would be ironic if the supposedly BLEO Orion stayed in LEO while a descendant of the originally intended suborbital BE-3 went on to be part of a reusable cis-lunar transfer system.

Reserving 10% of core stage fuel for RTLS (enough for 3500 m/s dv) and using a dual BE-3U EUS, this reusable booster would be pretty similar to SLS Block 1 performance. I get about 90t to LEO and 30t to TLI, even with fairly conservative assumptions about the extra dry mass needed for engines, legs, etc. The extra thrust in the core stage and EUS helps performance a lot.

Matching Block 1B would take upgraded boosters or a upper stage redesign; both together could get close to Block 2. Of course, designing the EUS to accept refueling (e.g. like ACES) would obviate the need for that kind of performance to LEO.
Title: Re: NASA defends decision to restart RS-25 production
Post by: Hog on 05/11/2017 06:01 PM


Quote
Point 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.

Yes, it is. RS-25 was designed as a sustainer engine that burns to almost orbit. It's use in SLS is the same. Most other engines are designed to be either first or upper stage engines - and virtually no engine would do the job as well for SLS.


[/quote]

They lit the 3 SSMEs at 100%RPL, then lit the 2 SRBs, up to 104.5% at "tower clear", then both liquids and solids decrease thrust, "in the bucket" for Max.Q, then liquids back to 104.5 and solids increase their thrust, then staging at approx. MET-122seconds with Booster Sep, approx. 5 minutes at 104.5%RPL with some OMS firing during OMS-1(depending on mission), then 3 g throttling, then the seats snap forward at MECO.

Yes, the RS-25 is a sustainer engine, and it burns during every second of that 0-17,500mph drag race, but as soon as the 25's shutdown at MECO, assuming OMS-2 wasn't required and aside from some minor orbital corrections, is the Orbiter on fully on-orbit?

Just clarifying the "RS-25 burns almost to orbit" wording.

Millions of engine-seconds during development, certification and flight qualification ending up with an engine that performed well under flight conditions.  It's demonstrated flight record of the actual hot parts/turbomachinery was backed with 100% mission success.  There were a couple sensor issues, and a maintenance issue(STS-51F and STS-93), but with so much historical data and 14 flight tested engines and 2 new un-fired engines already in the engine stands, hopefully NASA didn't have to defend its decision to restart production too hard. 

SLS- go for launch!
Title: Re: NASA defends decision to restart RS-25 production
Post by: ennisj on 05/11/2017 07:30 PM
Quote


Quote
Point 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.

Yes, it is. RS-25 was designed as a sustainer engine that burns to almost orbit. It's use in SLS is the same. Most other engines are designed to be either first or upper stage engines - and virtually no engine would do the job as well for SLS.



They lit the 3 SSMEs at 100%RPL, then lit the 2 SRBs, up to 104.5% at "tower clear", then both liquids and solids decrease thrust, "in the bucket" for Max.Q, then liquids back to 104.5 and solids increase their thrust, then staging at approx. MET-122seconds with Booster Sep, approx. 5 minutes at 104.5%RPL with some OMS firing during OMS-1(depending on mission), then 3 g throttling, then the seats snap forward at MECO.

Yes, the RS-25 is a sustainer engine, and it burns during every second of that 0-17,500mph drag race, but as soon as the 25's shutdown at MECO, assuming OMS-2 wasn't required and aside from some minor orbital corrections, is the Orbiter on fully on-orbit?

Just clarifying the "RS-25 burns almost to orbit" wording.

SLS- go for launch!

Can I ask for a point of clarification? It was my (possibly incorrect) understanding that at MECO, the shuttle was still suborbital, so that the ET would reenter upon separation, and that the OMS was used to give the orbiter that extra kick into orbit. 

"Almost to orbit" is more of a mission constraint rather than performance constraint if my understanding is correct. The various "wet workshop" reuse ideas would have the ET go to orbit with the orbiter, in which case the RS-25s could continue burning provided there was still LH/LOX in the tank.
Title: Re: NASA defends decision to restart RS-25 production
Post by: Hog on 05/15/2017 11:25 AM
Quote


Quote
Point 1 - SLS is NOT a "design around it" because the RS-25 engine includes reusability which the (horrendously short-sighted) SLS design ignores.

Yes, it is. RS-25 was designed as a sustainer engine that burns to almost orbit. It's use in SLS is the same. Most other engines are designed to be either first or upper stage engines - and virtually no engine would do the job as well for SLS.



They lit the 3 SSMEs at 100%RPL, then lit the 2 SRBs, up to 104.5% at "tower clear", then both liquids and solids decrease thrust, "in the bucket" for Max.Q, then liquids back to 104.5 and solids increase their thrust, then staging at approx. MET-122seconds with Booster Sep, approx. 5 minutes at 104.5%RPL with some OMS firing during OMS-1(depending on mission), then 3 g throttling, then the seats snap forward at MECO.

Yes, the RS-25 is a sustainer engine, and it burns during every second of that 0-17,500mph drag race, but as soon as the 25's shutdown at MECO, assuming OMS-2 wasn't required and aside from some minor orbital corrections, is the Orbiter on fully on-orbit?

Just clarifying the "RS-25 burns almost to orbit" wording.

SLS- go for launch!

Can I ask for a point of clarification? It was my (possibly incorrect) understanding that at MECO, the shuttle was still suborbital, so that the ET would reenter upon separation, and that the OMS was used to give the orbiter that extra kick into orbit. 

"Almost to orbit" is more of a mission constraint rather than performance constraint if my understanding is correct. The various "wet workshop" reuse ideas would have the ET go to orbit with the orbiter, in which case the RS-25s could continue burning provided there was still LH/LOX in the tank.
You cold be correct, I was asking for clarification myself.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 07/08/2017 03:59 AM
NASA defends decision to restart RS-25 production, rejects alternatives
Re: Is it fair to question the decisions of NASA/Congress? May we reject their decisions and offer superior alternatives? Is it likely NASA would/did agree with said alternatives, but chose to build a Congressional rocket while cowardly keeping silent as to this mistake?

A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.
Re: That's $2.23 billion down the drain by selecting the RS-25 over RS-68. Additionally, the RS-25 is a brand new engine with zero flight record, both increasing risk of LOM/LOC and requiring EOC. It's lower-performance, less safe, considerably more expensive (both development and operation) and possibly the worst design decision in SHLV's history. Thank you Congress, Augustine and Obama.

Since higher thrust, regenerative nozzle RS-68s are presumably out of the question...
Re: Regen is not only out of the question, it's unnecessary and always has been unless the core is designed specifically to make regen necessary. For example; Too many RS-68s together heat each other, and the core's base. Spread them apart and they're too close to the SRBs. No argument to the studies that professed such. So use less RS-68s with a bit of thermal mitigation and suddenly they don't heat up, each other, the base or roast by SRBs. You can mail me the $2.23 billion check now.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MATTBLAK on 07/08/2017 04:07 AM
Don't tell me; tell the guys in charge of Constellation! Oh; that's right...
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MATTBLAK on 07/08/2017 04:23 AM
...Besides: 3x RS68A engines, although having about the same thrust as 4x RS-25 engines, mass about 16,000 pounds more than 4x RS-25s! That, and their approximately 10% lower specific impulse would appear to make their use a bit pointless in any other context than Delta IV-Heavy. If SLS used 3x RS68A's in a wide-spaced manner like that suggested by the 'Direct' launcher guys, the thermal crosstalk issues with the SRBs could be mitigated somewhat. Couple that with shifting most of the main corestage structures to aluminum/lithium and composites, and the heavy engine penalty of the RS68s could be offset some.

And I don't suppose that changing the RS68 main nozzle to a regenerative cooling structure would save a great deal of mass, would it? And would the 5-to-10% specific impulse improvement of regenerative be deemed worth it?

Somehow; I feel a sense of deja-vu coming on; writing and reading this stuff...
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Hog on 07/08/2017 10:36 AM
NASA defends decision to restart RS-25 production, rejects alternatives
Re: Is it fair to question the decisions of NASA/Congress? May we reject their decisions and offer superior alternatives? Is it likely NASA would/did agree with said alternatives, but chose to build a Congressional rocket while cowardly keeping silent as to this mistake?

A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.
Re: That's $2.23 billion down the drain by selecting the RS-25 over RS-68. Additionally, the RS-25 is a brand new engine with zero flight record, both increasing risk of LOM/LOC and requiring EOC. It's lower-performance, less safe, considerably more expensive (both development and operation) and possibly the worst design decision in SHLV's history. Thank you Congress, Augustine and Obama.

$2.23 billion would be required to create and certify and RS-25 equivalent engine. Since the decision is to stay with RS25, that $2.23billion isn't required therefore not "money down the drain".

Not sure your assertion that the RS-25 is a new engine without any flight record males sense, 14 of the current inventory have actual flight experience, actually 3-4 flights on some of them.  Surely the risk of LC/LV risk would be markedly lower with RS-25, than with a new RS-25'equivalent engine?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 07/08/2017 03:24 PM
My main concern over the proposed build rate and the limitations of AJR's infrastructure to only be able to manufacture 2 engines per year is what that does to SLS flight rate and ultimately its per flight costs. With the first set of new engines available for assembly onto the flight frame in Q4 2025 which would support a flight in 2027 the next flight SLS FLT#6 would be NET Q4 2029!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

This is not good.

This makes this LV cost $$2B+ per flight for just an equivelent 100mt of LEO payload. That is a cost evaluation of $/kg for comparison to other LV's costs of $20,000/kg. Compare that to FH at $2,000/kg for all new boosters EXPD flight costs/price. NASA could purchase 16 FH flights for the money spent on just 1 SLS.

This just does not make sense. What is the justification for this immense expenditure?

Added: This cost problem is mainly due to low flight rate and not the basic costs of manufacture. At 2 flights per year the $/kg drops <$8,000/kg which is almost the same as that of other current medium and Heavy LVs. So it is the infrastructure limitations in build rate that has been built into a very short shighted build up of infrastructure due to limiting capital equipment costs expenditures that will make the SLS program unaffordable to operate.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Khadgars on 07/08/2017 08:44 PM
NASA defends decision to restart RS-25 production, rejects alternatives
Re: Is it fair to question the decisions of NASA/Congress? May we reject their decisions and offer superior alternatives? Is it likely NASA would/did agree with said alternatives, but chose to build a Congressional rocket while cowardly keeping silent as to this mistake?

A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.
Re: That's $2.23 billion down the drain by selecting the RS-25 over RS-68. Additionally, the RS-25 is a brand new engine with zero flight record, both increasing risk of LOM/LOC and requiring EOC. It's lower-performance, less safe, considerably more expensive (both development and operation) and possibly the worst design decision in SHLV's history. Thank you Congress, Augustine and Obama.

Since higher thrust, regenerative nozzle RS-68s are presumably out of the question...
Re: Regen is not only out of the question, it's unnecessary and always has been unless the core is designed specifically to make regen necessary. For example; Too many RS-68s together heat each other, and the core's base. Spread them apart and they're too close to the SRBs. No argument to the studies that professed such. So use less RS-68s with a bit of thermal mitigation and suddenly they don't heat up, each other, the base or roast by SRBs. You can mail me the $2.23 billion check now.

Complete non-sense.  RS-25 is one of the most flight proven engines of all time, most of the current stock has flown multiple missions with 100% reliability.  The $2.23 billion was for the design of an equivalent engine to the RS-25, not the RS-25 its self.  NASA spent about $1 Billion re-starting RS-25 production including 6 additional production engines.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 07/09/2017 08:08 PM
NASA defends decision to restart RS-25 production, rejects alternatives
Re: Is it fair to question the decisions of NASA/Congress? May we reject their decisions and offer superior alternatives? Is it likely NASA would/did agree with said alternatives, but chose to build a Congressional rocket while cowardly keeping silent as to this mistake?

A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.
Re: That's $2.23 billion down the drain by selecting the RS-25 over RS-68. Additionally, the RS-25 is a brand new engine with zero flight record, both increasing risk of LOM/LOC and requiring EOC. It's lower-performance, less safe, considerably more expensive (both development and operation) and possibly the worst design decision in SHLV's history. Thank you Congress, Augustine and Obama.

Since higher thrust, regenerative nozzle RS-68s are presumably out of the question...
Re: Regen is not only out of the question, it's unnecessary and always has been unless the core is designed specifically to make regen necessary. For example; Too many RS-68s together heat each other, and the core's base. Spread them apart and they're too close to the SRBs. No argument to the studies that professed such. So use less RS-68s with a bit of thermal mitigation and suddenly they don't heat up, each other, the base or roast by SRBs. You can mail me the $2.23 billion check now.

Complete non-sense.  RS-25 is one of the most flight proven engines of all time, most of the current stock has flown multiple missions with 100% reliability.  The $2.23 billion was for the design of an equivalent engine to the RS-25, not the RS-25 its self.  NASA spent about $1 Billion re-starting RS-25 production including 6 additional production engines.
Actually those 6 engines are only 4 flight, one qual/development engine, and one production/qual/pathfinder. The contract also sets the price per engine and options for additional engines in sets of 4. Options contract duration from execution would be 6 years. The optimal time for the execution of engine option contract would be 1 year after the last set of 2 engines start (5 years before those 2's delivery) or around 2021.

There is also a possibility of a separate contract to AJR for additional infrastructure to increase engine production rate for 2/yr to as many as 8/yr. This would be needed to have engine production match the rest of the vehicle manufacture rates. If NASA does this this contract would probably happen about 2020. After the first flight of EM-1. It would be confirmation by the PTBs that SLS is here to stay and that its use in the later half of the 2020's will be 2 flights/yr. Also going to a production rate of 8/yr from 2/yr is liable to reduce unit costs of engines by as much as 50%. If SLS will be used in the late 2020's and into the 2030's then this would be a prudent investment to lower those out year costs making the per flight costs of SLS at 2 per year as low as $600M. That is in 4/kg to LEO equivalent comparison costs of $6,000/kg. Still expensive but not outrageous.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Tomness on 07/09/2017 11:34 PM
Are these engines going to be RS-25D or RS-25E?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MATTBLAK on 07/10/2017 12:01 AM
new ones are likely to be 'RS-25E'.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Khadgars on 07/10/2017 09:46 PM
NASA defends decision to restart RS-25 production, rejects alternatives
Re: Is it fair to question the decisions of NASA/Congress? May we reject their decisions and offer superior alternatives? Is it likely NASA would/did agree with said alternatives, but chose to build a Congressional rocket while cowardly keeping silent as to this mistake?

A recent, parametric estimate performed by NASA suggests that just the design cost for creating and certifying an RS-25 equivalent engine would be approximately $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.
Re: That's $2.23 billion down the drain by selecting the RS-25 over RS-68. Additionally, the RS-25 is a brand new engine with zero flight record, both increasing risk of LOM/LOC and requiring EOC. It's lower-performance, less safe, considerably more expensive (both development and operation) and possibly the worst design decision in SHLV's history. Thank you Congress, Augustine and Obama.

Since higher thrust, regenerative nozzle RS-68s are presumably out of the question...
Re: Regen is not only out of the question, it's unnecessary and always has been unless the core is designed specifically to make regen necessary. For example; Too many RS-68s together heat each other, and the core's base. Spread them apart and they're too close to the SRBs. No argument to the studies that professed such. So use less RS-68s with a bit of thermal mitigation and suddenly they don't heat up, each other, the base or roast by SRBs. You can mail me the $2.23 billion check now.

Complete non-sense.  RS-25 is one of the most flight proven engines of all time, most of the current stock has flown multiple missions with 100% reliability.  The $2.23 billion was for the design of an equivalent engine to the RS-25, not the RS-25 its self.  NASA spent about $1 Billion re-starting RS-25 production including 6 additional production engines.
Actually those 6 engines are only 4 flight, one qual/development engine, and one production/qual/pathfinder. The contract also sets the price per engine and options for additional engines in sets of 4. Options contract duration from execution would be 6 years. The optimal time for the execution of engine option contract would be 1 year after the last set of 2 engines start (5 years before those 2's delivery) or around 2021.

There is also a possibility of a separate contract to AJR for additional infrastructure to increase engine production rate for 2/yr to as many as 8/yr. This would be needed to have engine production match the rest of the vehicle manufacture rates. If NASA does this this contract would probably happen about 2020. After the first flight of EM-1. It would be confirmation by the PTBs that SLS is here to stay and that its use in the later half of the 2020's will be 2 flights/yr. Also going to a production rate of 8/yr from 2/yr is liable to reduce unit costs of engines by as much as 50%. If SLS will be used in the late 2020's and into the 2030's then this would be a prudent investment to lower those out year costs making the per flight costs of SLS at 2 per year as low as $600M. That is in 4/kg to LEO equivalent comparison costs of $6,000/kg. Still expensive but not outrageous.

Thank you for that, good analysis.  I agree, we're likely to see a follow-on contract with AJR to support 2 SLS flights per year, but like you stated we won't see such a contract until end of this decade.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 07/11/2017 02:26 AM
... Somehow; I feel a sense of deja-vu coming on; writing and reading this stuff...
I'm not going to wax poetic about butterflies, but decisions often determine the next set of decisions and weight the following choices. In every type of engineering, key junctions exist that must be robust or the entire system/structure can collapse. Well, selection of the RS-68 vs the RS-25 is one of those defining decisions that dictates the rest of the rocket, program and its viability.
With the RS-25, the SLS can only be a money pit, time waster and ultimately a dead end.

Some might say money's been spent, so we can't reconsider. Yet we spent $1.4 billion developing, building and testing multiple J-2Xs for flight. Some may say the PoR is set in stone, but that didn't preserve Ares and Nov 8th threw all kinds of presumptions out the door.
It's time to readdress our SHLV - correcting terrible choices, designing a viable program, expediting progress and breath life into human exploration that was taken to the pawn shop in 2008-2010 for "walking around money". For starters; the $1.6 billion already devoted to RS-25s was a waste and it's time for a better, cheaper engine.

... The $2.23 billion was for the design of an equivalent engine to the RS-25, not the RS-25 its self.  NASA spent about $1 Billion re-starting RS-25 production including 6 additional production engines.
Actually those 6 engines are only 4 flight, one qual/development engine, and one production/qual/pathfinder. The contract also sets the price per engine and options for additional engines in sets of 4. ...
(Great info Atlas)

That's $1.18 billion to get 16 RS-25D out of storage and ready for SLS #1-4, or a cool $74mil per engine, plus
“... restarts [Aerojet Rocketdyne’s] production capability, including furnishing the necessary management, labor, facilities, tools, equipment and materials required for this effort”, as well as “implementing modern fabrication processes and affordability improvements and producing hardware required for development and certification testing”.
http://www.americaspace.com/2015/11/24/nasa-contracts-with-aerojet-rocketdyne-to-restart-rs-25-engine-production-for-sls/
That doesn't actually build new engines, just gets ready to. The six new engines cost an additional $413 million, or a cool $69mil per engine (with only four flying) - based on the "... $2.23 billion, which is 40 percent greater than the total estimated cost of this procurement action to acquire six RS-25 flight-ready engines.”
https://www.nasaspaceflight.com/2016/01/nasa-defends-restart-rs-25-production/

Hmmmmmmmm.
Old RS-25Ds cost $74mil each times four per flight, while RS-68s cost ~$20mil each times three. So the SLS costs $236mil more initially per flight with RS-25Ds. Once the completely redesigned RS-25Es with zero flight history arrive, that drops to $216mil more per flight with RS-25Es (though testing is likely to drive this cost up). Yep, the RS-25 should be cancelled and replaced with RS-68s immediately. Even better if the build-up and production contract can be repurposed for an engine that's actually needed - like restarting J-2X production.

(the following belongs in another thread, but is left here to close and emphasize decision chains)
Switching to RS-68s leaves money on the table for J-2X production; which allows cancellation of the Advanced Booster program as RS-68 and J-2X loft +130mT to LEO and +40mT to the Moon; and no AB-program frees cash for actual missions - with components! The timeline for launching infrastructure toward a manned, lunar program suddenly jumps from the 30's to whenever the first J-2X launches. Maybe the DSG on EM-3?
There's that butterfly!
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MATTBLAK on 07/11/2017 02:49 AM
There are some truths and interesting 'repacked' summarizing of the SLS engine choices you discuss... Trouble is - we thrashed out all this stuff during the pre-SLS 'Direct vs Constellation' discussions the better portion of a decade ago. This ship has sailed! The SLS; if it flies at all, will fly with RS-25's and RL-10. It doesn't matter if I and some other folk think regenerative RS68, J2X, MB60 or BE3's would be better choices. They don't care what we think. The die has been cast and the pork must flow...
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Endeavour_01 on 07/11/2017 03:45 AM

I'm not going to wax poetic about butterflies, but decisions often determine the next set of decisions and weight the following choices. In every type of engineering, key junctions exist that must be robust or the entire system/structure can collapse.

I agree, which is why your plan would cause the entire SLS/Orion program to collapse. As MATTBLAK said the ship has sailed on what engines to use on SLS. The junction was passed 6 years ago. To change engines now would require a complete redesign of the SLS core and upper stages and would add years plus untold costs to the PoR.

Even then its not like RS-68 and J-2X are a panacea. There are tradeoffs with whatever engine you use. From what I recall J-2X is an excellent 2nd stage engine when you want to go to LEO, but SLS's main purpose is for BLEO flight. For that the RL-10 is superior. As MATTBLAK said RS-68 is much heavier than RS-25 and there are heating issues with more than 3 RS-68s on the core.

Quote
The timeline for launching infrastructure toward a manned, lunar program suddenly jumps from the 30's to whenever the first J-2X launches.

Actually, this plan would push a manned lunar program past the 2030s. Rockets are not Legos. The core stage is already being fabricated. To go back now means we have to throw away all the design work and tooling that took 6 years to make.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 07/11/2017 12:51 PM
...
There is also a possibility of a separate contract to AJR for additional infrastructure to increase engine production rate for 2/yr to as many as 8/yr. This would be needed to have engine production match the rest of the vehicle manufacture rates.
...
With infrastructure for two engines/yr, AR is well positioned to transition that manufacturing capacity and contract from RS-25Es to J-2X, which only need two/flight. With RS-68s powering the core the RS-25Ds could go back into storage as emergency engines to avoid stand down if a future problem occurs with RS-68s.
If intransigence prevails we could delay RS-68s until EM-3, but that reduces the emergency stockpile of RS-25s while paying to fly a rocket there's no intention to use (like Ares-1X). It'd be better to delay EM-1 until the new thrust structure and RS-68 configuration, which shouldn't affect EM-2's timeline. It has its own issues.

...
To change engines now would require a complete redesign of the SLS core and upper stages and would add years plus untold costs to the PoR. ... The core stage is already being fabricated. To go back now means we have to throw away all the design work and tooling that took 6 years to make.
Changing the core isn't a bad idea, as long as the tooling and techniques remain the same. The structural limits are knows and needn't change much, even with new main engines. Fortunately, that's all that's been accomplished so far; knowledge and manufacturing capability - not actual production. Nothing gets "thrown away" other than SLS's poor design and all the time/money wasted on it to date.

For example; The LH tank has a humongous and heavy thrust structure to position the main engines low enough for use and far enough away from the LH for safety. That tank could go from five 22ft barrel sections to six (without changing the jig or raising the roof) with an internally-buttressed common bulkhead. That becomes around 1.9mil lbs propellant with main engines and abbreviated thrust structure flush to the LOX tank. A whole lot of weight and cost just got shaved with payloads (single-stage) or US sitting atop the solid's crossbeam.

For example; If AR produces J-2X instead of RS-25E we don't need specific tooling for the upper stage. The existing 8.4m LOX jig (no longer in use) can produce an upper stage holding around 420,ooo lbs propellant with a single 22ft barrel section and common bulkhead - both shared with the aforementioned first stage. The budgeting for the Exploration Upper Stage, like the Advanced Booster program, can now go towards these redesigns and/or missions.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Khadgars on 07/11/2017 09:34 PM
...
There is also a possibility of a separate contract to AJR for additional infrastructure to increase engine production rate for 2/yr to as many as 8/yr. This would be needed to have engine production match the rest of the vehicle manufacture rates.
...
With infrastructure for two engines/yr, AR is well positioned to transition that manufacturing capacity and contract from RS-25Es to J-2X, which only need two/flight. With RS-68s powering the core the RS-25Ds could go back into storage as emergency engines to avoid stand down if a future problem occurs with RS-68s.
If intransigence prevails we could delay RS-68s until EM-3, but that reduces the emergency stockpile of RS-25s while paying to fly a rocket there's no intention to use (like Ares-1X). It'd be better to delay EM-1 until the new thrust structure and RS-68 configuration, which shouldn't affect EM-2's timeline. It has its own issues.

...
To change engines now would require a complete redesign of the SLS core and upper stages and would add years plus untold costs to the PoR. ... The core stage is already being fabricated. To go back now means we have to throw away all the design work and tooling that took 6 years to make.
Changing the core isn't a bad idea, as long as the tooling and techniques remain the same. The structural limits are knows and needn't change much, even with new main engines. Fortunately, that's all that's been accomplished so far; knowledge and manufacturing capability - not actual production. Nothing gets "thrown away" other than SLS's poor design and all the time/money wasted on it to date.

For example; The LH tank has a humongous and heavy thrust structure to position the main engines low enough for use and far enough away from the LH for safety. That tank could go from five 22ft barrel sections to six (without changing the jig or raising the roof) with an internally-buttressed common bulkhead. That becomes around 1.9mil lbs propellant with main engines and abbreviated thrust structure flush to the LOX tank. A whole lot of weight and cost just got shaved with payloads (single-stage) or US sitting atop the solid's crossbeam.

For example; If AR produces J-2X instead of RS-25E we don't need specific tooling for the upper stage. The existing 8.4m LOX jig (no longer in use) can produce an upper stage holding around 420,ooo lbs propellant with a single 22ft barrel section and common bulkhead - both shared with the aforementioned first stage. The budgeting for the Exploration Upper Stage, like the Advanced Booster program, can now go towards these redesigns and/or missions.

As already stated up-thread, this ship has sailed, so no, RS-25 will not be replaced on SLS.  RS-25 is perfectly suited for SLS needs.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MATTBLAK on 07/11/2017 10:32 PM
Yes. The above is interesting stuff, but old news and more accurately - things that simply are not going to happen. SLS will either fly basically as-is, or will be cancelled. The outcome is binary. There is no third choice.

*If it does fly and gets as far as the Block II configuration operational, the only improvements notionally possible after that would be RS-25E upgrades and changing the huge propellant tankage to lighter alloys. In other words; spending a lot more money to tweak an already very expensive booster.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 07/12/2017 05:02 PM
Yes. The above is interesting stuff, but old news and more accurately - things that simply are not going to happen. SLS will either fly basically as-is, or will be cancelled. The outcome is binary. There is no third choice.

*If it does fly and gets as far as the Block II configuration operational, the only improvements notionally possible after that would be RS-25E upgrades and changing the huge propellant tankage to lighter alloys. In other words; spending a lot more money to tweak an already very expensive booster.
Yes even to tweak the infrastructure to be able to build 2 SLS/yr from the current infrastructure level of just 1 SLS/ every 2 years would require more funding (Probably several $Bs) and time. NASA management, in order to appease Congress, went down the rabbit hole from which there is no exit in regards to engine choices. But at the time they had no time and little choice of available engines RS25 or RS68. RS68 had too many insurmountable problems without a lot of funding and engine development time (make the RS68 regeneratively cooled). So that only left RS25 because of the timeline for first launch. Now they are stuck with the engine. With an available time period of what will be 5 years prior to final assembly of the flight SLS from program start vs the initial timeline of only 2/3 years they could have fixed the RS68 problems.

The complete problem was that management created a 100% success task schedule to get to a 2017 launch of EM-1. When they should have told Congress it was not going to happen NET 2019 just due to all those statistically historical task failures and delays in the execution of a major LV development program under a flat budget with no contingency funding to handle task failures.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Khadgars on 07/13/2017 12:53 AM
Yes. The above is interesting stuff, but old news and more accurately - things that simply are not going to happen. SLS will either fly basically as-is, or will be cancelled. The outcome is binary. There is no third choice.

*If it does fly and gets as far as the Block II configuration operational, the only improvements notionally possible after that would be RS-25E upgrades and changing the huge propellant tankage to lighter alloys. In other words; spending a lot more money to tweak an already very expensive booster.
Yes even to tweak the infrastructure to be able to build 2 SLS/yr from the current infrastructure level of just 1 SLS/ every 2 years would require more funding (Probably several $Bs) and time. NASA management, in order to appease Congress, went down the rabbit hole from which there is no exit in regards to engine choices. But at the time they had no time and little choice of available engines RS25 or RS68. RS68 had too many insurmountable problems without a lot of funding and engine development time (make the RS68 regeneratively cooled). So that only left RS25 because of the timeline for first launch. Now they are stuck with the engine. With an available time period of what will be 5 years prior to final assembly of the flight SLS from program start vs the initial timeline of only 2/3 years they could have fixed the RS68 problems.

I'm not sure if that is accurate (1 SLS every 2 years).  Everything I'v read shows current infrastructure supports 2 per year with little to no changes, unless you are referring to the RS-25 contract with AJR?  I think we all understand a follow-on contract will be executed probably around 2020.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MATTBLAK on 07/13/2017 01:07 AM
Correct - two produced per year, with a 'surge' of three per year with funding ramped-up. But for a Mars Mission buildup of the needed mass, I could see that 4x Block II would be needed, at minimum. It may turn out that the other needed mass would have to go up on Commercial vehicles, such as New Glenn, Falcon Heavy or Vulcan.

3x Block II SLS and 1x each of those other boosters would represent a significant amount of tonnage placed into LEO over a few months or one year.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: TomH on 07/13/2017 03:21 AM
It is true that all of this has been hashed out many times over the last decade. What has changed, and is being completely ignored in this thread, are the mammoth elephants currently in the womb. All of this will become moot when they are birthed.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Proponent on 07/13/2017 08:39 AM
Correct - two produced per year, with a 'surge' of three per year with funding ramped-up.

I believe that the 3-per-year surge applies to the launch rate (ie, a 120-day turn-around time for LC-39B) rather than to the production rate.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: MATTBLAK on 07/13/2017 12:22 PM
Yes - both factors are true. 3x complete vehicles per year would be the limit; both for a funding and the 'launch surge' logistics. With the right funding and probably a second launch pad; I could not imagine more than 4x per annum in any case.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Khadgars on 07/13/2017 08:13 PM
Correct - two produced per year, with a 'surge' of three per year with funding ramped-up.

I believe that the 3-per-year surge applies to the launch rate (ie, a 120-day turn-around time for LC-39B) rather than to the production rate.

Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Proponent on 07/13/2017 08:20 PM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

Source?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: ennisj on 07/13/2017 08:49 PM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

Source?

According to a former Boeing SLS Program Manager: "Boeing has Michoud set up to stamp out enough stages for one SLS a year — two at most with the factory’s current manufacturing capabilities, and then only if NASA pours more money and personnel into the facility."

MAF SLS core production rates have been hashed out in this thread: https://forum.nasaspaceflight.com/index.php?topic=37060.0 (https://forum.nasaspaceflight.com/index.php?topic=37060.0) (including the source for the above quote.)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 07/13/2017 09:00 PM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

Source?

According to a former Boeing SLS Program Manager: "Boeing has Michoud set up to stamp out enough stages for one SLS a year — two at most with the factory’s current manufacturing capabilities, and then only if NASA pours more money and personnel into the facility."

MAF SLS core production rates have been hashed out in this thread: https://forum.nasaspaceflight.com/index.php?topic=37060.0 (https://forum.nasaspaceflight.com/index.php?topic=37060.0) (including the source for the above quote.)
So to get to 1 per year just requires extra infrastructure at AJR to be able to build 4 engines /yr. But in order to get to 2 per year where it should be at, requires more personnel and equipment all around.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 07/13/2017 09:06 PM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

That is hilarious. They peaked with ~10 Shuttles per year off a single pad during the Shuttle program. But can only do 3 now?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: eric z on 07/13/2017 09:10 PM
 Am I the only one getting very confused? Yikes! :-[
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 07/13/2017 09:26 PM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

That is hilarious. They peaked with ~10 Shuttles per year off a single pad during the Shuttle program. But can only do 3 now?
They only have 1 MLP for SLS. To do more launches more often multiple (as many as 4 like Shuttle and Apollo had at one point). So with 1 MLP you can do up to 3 in 1 year. If you had 4 you could do up to 12!!!

After launch the MLP must be refurbished. Then it moves back to the VAB where stacking starts. So with 1 MLP all tasks are serial and any delays from the previous launch delays all launches following. There is no scheduling padding capability or contingency capabilities if the MLP becomes severely damaged. It would take several years and $100sM to upgrade another MLP to be able to launch an SLS. So until the manufacturing side is upgraded the launch side only needs the 1 MLP.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 07/13/2017 09:29 PM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

That is hilarious. They peaked with ~10 Shuttles per year off a single pad during the Shuttle program. But can only do 3 now?
They only have 1 MLP for SLS. To do more launches more often multiple (as many as 4 like Shuttle and Apollo had at one point). So with 1 MLP you can do up to 3 in 1 year. If you had 4 you could do up to 12!!!

After launch the MLP must be refurbished. Then it moves back to the VAB where stacking starts. So with 1 MLP all tasks are serial and any delays from the previous launch delays all launches following. There is no scheduling padding capability or contingency capabilities if the MLP becomes severely damaged. It would take several years and $100sM to upgrade another MLP to be able to launch an SLS. So until the manufacturing side is upgraded the launch side only needs the 1 MLP.

Ok, thanks, that makes a certain amount of sense. But it also dooms the program to never get anything useful done, if launches have to be spaced 3-4 months. (The exception being missions that can done done in a single launch like Europa Clipper)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 07/13/2017 10:40 PM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

That is hilarious. They peaked with ~10 Shuttles per year off a single pad during the Shuttle program. But can only do 3 now?
They only have 1 MLP for SLS. To do more launches more often multiple (as many as 4 like Shuttle and Apollo had at one point). So with 1 MLP you can do up to 3 in 1 year. If you had 4 you could do up to 12!!!

After launch the MLP must be refurbished. Then it moves back to the VAB where stacking starts. So with 1 MLP all tasks are serial and any delays from the previous launch delays all launches following. There is no scheduling padding capability or contingency capabilities if the MLP becomes severely damaged. It would take several years and $100sM to upgrade another MLP to be able to launch an SLS. So until the manufacturing side is upgraded the launch side only needs the 1 MLP.

Ok, thanks, that makes a certain amount of sense. But it also dooms the program to never get anything useful done, if launches have to be spaced 3-4 months. (The exception being missions that can done done in a single launch like Europa Clipper)
The SLS program like many gov space programs is in the English saying "Penny wise but Pound foolish". Not spending enough now means you pay a lot more later.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: edkyle99 on 07/14/2017 03:01 AM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

That is hilarious. They peaked with ~10 Shuttles per year off a single pad during the Shuttle program. But can only do 3 now?
Three Block 1B SLS launches would be able to put 27 Space Shuttle mission's worth of payload into solar orbit.  Hilarious, huh?

 - Ed Kyle
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 07/14/2017 04:53 AM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

That is hilarious. They peaked with ~10 Shuttles per year off a single pad during the Shuttle program. But can only do 3 now?
Three Block 1B SLS launches would be able to put 27 Space Shuttle mission's worth of payload into solar orbit.  Hilarious, huh?

 - Ed Kyle

An interesting metric, but not very useful other then pointing out that the Shuttle system was not that efficient at putting payloads into orbit.  :)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: ZachF on 07/14/2017 02:07 PM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

That is hilarious. They peaked with ~10 Shuttles per year off a single pad during the Shuttle program. But can only do 3 now?
Three Block 1B SLS launches would be able to put 27 Space Shuttle mission's worth of payload into solar orbit.  Hilarious, huh?

 - Ed Kyle


...and for the cost we're spending just on development for SLS and Orion we could put up over 1,000 tonnes to LEO per year with SpaceX and soon BO with money to spare.

Every year we spend more on SLS+Orion, a system that has a lot of hand-me-downs from Shuttle, that will be obsolete before it ever launches than it took a certain company from Hawthorne to develop a world-beating launch vehicle, make it reusable, and design a space ship for it.

Every year we shovel away a Juno and Curiosity worth of funds (combined) into the hole that is SLS.

It's time to put SLS to pasture.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 07/14/2017 03:44 PM
We have wandered away from the RS-25 issues. Specifically the new build.

In the latest CJS appropriation bill there is no reduction in spending for SLS but neither is their a significant increase to increase infrastructure to increse build rates. Most of the increses are to get EM-1 completed and to fund the new development work on the US.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: jtrame on 07/14/2017 06:50 PM
Production can support 2 per year now, with some funding required to reach 3 per year.  I think max launch rate is 3 per year from 39B.

That is hilarious. They peaked with ~10 Shuttles per year off a single pad during the Shuttle program. But can only do 3 now?
Three Block 1B SLS launches would be able to put 27 Space Shuttle mission's worth of payload into solar orbit.  Hilarious, huh?

 - Ed Kyle

It's an interesting metric because to actually mount a manned Mars mission it's going to take assembly of a huge interplanetary ship.  SLS could very well supply at least part of this muscle, theoretically of course. Pipe dreams won't get it done. 

The restart of engine production is another step in that direction.  But SLS for or against shouldn't be part of this topic.  There are more appropriate threads for that discussion.

Right now SLS is part of the 2018 budget.  To those that want to see it cancelled, you will have to work through that process. 
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 07/14/2017 07:40 PM
We have wandered away from the RS-25 issues. Specifically the new build.
 -Thanks for calling that out, Atlas. Though it shouldn't be necessary.
In the latest CJS appropriation bill there is no reduction in spending for SLS but neither is their a significant increase to increase infrastructure to increse build rates. Most of the increses are to get EM-1 completed and to fund the new development work on the US.
No change in RS-25 infrastructure spending, but increases in EM-1 and US budgets is the perfect time to put RS-25 back into storage. The production infrastructure and buildup AR was paid to do for RS-25 gets converted to J-2X ; EM-1 is delayed and funded while it converts to a 3x RS-68 base ; The EUS is designed around 2x J-2X for an EM-3 cargo mission debut ; and Advanced Booster program cancelled.

EM-1: Pushed back a bit, but still an unmanned testflight with 3x RS-68, a Delta US and EuroSM
EM-2: No change in schedule as a manned testflight with the same 68/DUS/ESM layout
EM-3: DSG cargo mission with new J-2X US and possibly the related 6-barrel core tankage
EM-4: Manned flight of the finalized 68/J-2X rocket and SM delta-v increase to 2,000m/s

All this is not only possible, but begins with putting RS-25 back in a shed where it should have stayed.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AnimatorRob on 07/14/2017 08:13 PM
Am I the only one getting very confused? Yikes! :-[

Confused? No. Sad? Yes.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 07/29/2017 02:42 PM
The SLS program like many gov space programs is in the English saying "Penny wise but Pound foolish". Not spending enough now means you pay a lot more later.
I'm not sure if SLS (and its engine choices specifically) really was about saving money "now", but about politicians and administrators thinking they were saving money. The RS-25 is a $70mil engine, both to get existing ones out of storage and new builds, while the claim was "we already have these engines". Similarly "we already have RL10s", even though that requires preparing DUS for EM-1&2 nowhere missions followed by another underpowered upper stage of all-new manufacturing plus all-new boosters. The alternative is fewer $20mil 68's per launch and a production-ready J-2X stage based on core tooling.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 07/29/2017 03:24 PM

The alternative is fewer $20mil 68's per launch and a production-ready J-2X stage based on core tooling.

There is no such alternative, if it includes RS-68.  RS-68 and SRB are not viable, much like air start SSME. 

Also, there is no need for J-2, when RL 10 is available
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Space Ghost 1962 on 07/29/2017 09:48 PM
If you had to have an alternative (ignoring political necessities):

The first that comes to mind with SLS is to start with it's RSRBV boosters - not so much anything as that they limit the payload growth of the SLS core for various reasons (GTOW, core mass fraction to name a few).

If you accept as a given that SX can get to the reliability and economics of recoverable boosters, you reformulate SLS as like the EELV's/FH from the bottom to accept two pairs of two recoverable (or not) F9 cores. Block 5 cores should allow a significant advantage here (including with base heating, meaning more engine options for the core).

Either add RS-25's (continuing production) or substitute RS68A's (still flying them on DIVH) and restructure the flight profile to accept higher acceleration than HSF. You could exceed 250+t this way, and have a vehicle that could be flying for more than a decade. Marshall definitely could do this.

So your missions to build the DSG would be fewer/faster, and your mission architecture would be to logistically support lunar/Mars missions from DSG assembled vehicles, mission modules, and consumables.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: spacenut on 07/30/2017 12:07 AM
How much would it cost to replace the 4 RS-25 engines with about 16 BE-3's that are used on the New Shepard?  Also, don't know if it would work, but with a second stage, the core might could return and land to save it. 
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Space Ghost 1962 on 07/30/2017 02:00 AM
If you could stage significantly higher/faster with kerolox boosters/less GTOW/better core mass fraction, and if the expansion ratio of the nozzles were greater, 18 BE-3U's (if they fit/thermal issues too) might get you to 140-150t out performing the 4 RS 25s hands down. A lot harder to compete with the 5-6 RS-25's.

But no one at Marshall would feel comfortable suggesting so many engines. Although it's an excellent suggestion, especially for budget.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: spacenut on 07/30/2017 02:31 AM
Even the proposed new Raptors and switching to metholox on the core with an upper stage would get more to LEO and probably cheaper.  Would only take 8 of the sub scale ones.  NASA launched Saturn IB with 8. 
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chris Bergin on 07/31/2017 10:40 AM
Even the proposed new Raptors and switching to metholox on the core with an upper stage would get more to LEO and probably cheaper.  Would only take 8 of the sub scale ones.  NASA launched Saturn IB with 8. 

Problem is, let's be you for a moment, turning up at NASA HQ with your suggestion. I think it'll help add some humorous context to many other "But SpaceX?" posts we see on here. ;)

"Hey NASA. So that SLS *cough* PORK *cough*, sorry, I've got a cold. Anyway, yes, that rocket using proven reliable and hardware of the ET and RS-25. Have any of you considered using an engine that's not actually real yet (there's a demonstrator at McGregor, so that counts, right?) I know RS-25 has 30 years of experience and only one issue in its lifetime, but Raptor....it's SpaceX!! You know, the cool guys!

"PS You'll also need to completely change the core as it's not LH2/LOX and it'll cost you billions to change it all, but the engine itself will be cheaper. #Economics

"Anyway, you can thank me later! Oh, but there's another person outside with his own suggestion of taking 16 of those engines uses on a suborbital test flight instead. Shall I let him in? PS Why are you all laughing?"

SLS has had - and is still having - its schedule and development issues, but if anyone thinks SpaceX and so on aren't, check out Falcon Heavy and watch how fast lawmakers would pull the plug on a NASA purchased SpaceX SHLV if Elon said "it'll be a result if we don't blow up and wreck the pad".

PS If they cancelled SLS today, don't think it'll be a check to SpaceX tomorrow. If and only if lawmakers opted to redirect SLS money (which I also doubt, it'd likely just be removed from the NASA budget), it would only be after years of paying off the contract cancellations at Boeing and co.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 07/31/2017 03:56 PM
Hey Chris, I thought this was a discussion about the RS25 new build. Although I do appreciate the realistic perspective being expresses, because as actually working on the government side (AF actually) on STS inertia and other things makes it impossible for programs to switch horse late in the rac unless there is no alternativ.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Hog on 07/31/2017 05:03 PM
Hey Chris, I thought this was a discussion about the RS25 new build. Although I do appreciate the realistic perspective being expresses, because as actually working on the government side (AF actually) on STS inertia and other things makes it impossible for programs to switch horse late in the rac unless there is no alternativ.

Are you implying that the 30 years of operational experience, and over 40 years including over 1 million seconds of test stand hotfire experience is NOT applicable to an RS25 engine that has had some of its internals that were designed for reusability substituted for parts that are designed for "single use disposability"/lower cost?


xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I am really starting to become annoyed with AR(Aerojet Rocketdyne)/NASAs decision to drop the RS25-A, RS25-B, RS-25-C, RS25-D, RS25-E designations, even if these designations weren't in actual internal usage.  Even Phase 1, Phase 2, Block 1, Block 1-A, Block II-A and Block II(RS25-D-final flown configuration of SSME) descriptors of RS25 are far easier to manage than the new "crop" of RS25 designators such as: "old build" "new build", "re-useable" "non-reusable", "legacy", "older more expensive units", newer "less expensive" units.  I'm sure there was some financial, corporate or political reason for referring to an RS25 engine as an RS25 engine regardless of its exact makeup.  I guess this annoyance will clear itself up after EM-4 after the last RS-25D drops into the saline abyss.  Thus we are left with only SLSME type RS-25s in the lineup.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chris Bergin on 07/31/2017 06:05 PM
Hey Chris, I thought this was a discussion about the RS25 new build. Although I do appreciate the realistic perspective being expresses, because as actually working on the government side (AF actually) on STS inertia and other things makes it impossible for programs to switch horse late in the rac unless there is no alternativ.

New build is even better. RS-25D to RS-25E means it's far cheaper, but all with that lovely reliability.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Space Ghost 1962 on 07/31/2017 09:04 PM
Hey Chris, I thought this was a discussion about the RS25 new build. Although I do appreciate the realistic perspective being expresses, because as actually working on the government side (AF actually) on STS inertia and other things makes it impossible for programs to switch horse late in the rac unless there is no alternativ.

Are you implying that the 30 years of operational experience, and over 40 years including over 1 million seconds of test stand hotfire experience is NOT applicable to an RS25 engine that has had some of its internals that were designed for reusability substituted for parts that are designed for "single use disposability"/lower cost?


Shuttle reused them frequently. SLS one time use only. Applying RLV flight history to ELV engine development "informs" but does not "assure" on refinement.

Now, what specific target are we shooting for? SSME is a very complex beast. You just can't wave a wand and magically make it cheaper. What performance levels are required? Uprating? Greater margins for HSF than prior Shuttle ones, because we want to lower our LOC/LOM numbers too?

How much are we allowed to change the engine's physical geometry/size (much of the issues were in making a compact, ground start engine for a spaceplane application). How about the feed lines, can we change them too? Can we use electrical instead of hydraulic in certain places? Can we use new materials that will last 1-2 times instead of 30+?

Can we eliminate whole portions of the design that might sacrifice 2-15 sec-1 of iSP?

Now, we take all of that and run it on the test stand and compare numbers? Can we prove we've met requirements and retained acceptable reliability? Tall order.

Quote
I am really starting to become annoyed with AR(Aerojet Rocketdyne)/NASAs decision to drop the RS25-A, RS25-B, RS-25-C, RS25-D, RS25-E ... Thus we are left with only SLSME type RS-25s in the lineup.
I take it you weren't a fan of "New Coca Cola" either  ;D

Many at AR also are similarly annoyed. Yes, it's a great, historic engine. Yes, it taught us all a lot.

Is it (or J-2X even) the right place to start from? Shuttle derived meant to carry the "development momentum" and the "industry base" into CxP/SLS, which seemed possible for a "quick" program post Shuttle.

Now that is less clear. But we seem to be committed. It is unclear what we are committed too though.

Hey Chris, I thought this was a discussion about the RS25 new build. Although I do appreciate the realistic perspective being expresses, because as actually working on the government side (AF actually) on STS inertia and other things makes it impossible for programs to switch horse late in the rac unless there is no alternativ.

New build is even better. RS-25D to RS-25E means it's far cheaper, but all with that lovely reliability.

Both are in doubt. It's been too long. Don't count your chickens ...

add:
Oh, and I forgot about the engine controller changes to optimize 4/5/6 engine clusters over the current "3".
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 08/01/2017 06:44 AM
New build is even better. RS-25D to RS-25E means it's far cheaper, but all with that lovely reliability.
To pull 25D out of the shed and build up 25E production capacity costed around $70mil/engine ($1.18bil / 16engines) and the new 25E will also cost about the same ($413mil / 6engines, 4flying) compared to RS-68 at around $20mil/engine and fewer per core compared to 25s.

There is no such alternative, if it includes RS-68.  RS-68 and SRB are not viable, much like air start SSME.
Jim, You're very knowledgeable, but mistaken here. RS-68 and SRB is an engineering challenge, not an impossibility. NASA's conclusion was regen at around $150mil in development and doubling the unit cost. I disagree with messing up an inexpensive, robust and impeccably-reliable engine and instead previously outlined a boattail that puts existing 68s in a more benign environment then they have under Delta IV. I'm sure there's other options, possibly some better, to address this engineering problem. -- Boattail post;
https://forum.nasaspaceflight.com/index.php?topic=38069.msg1706197#msg1706197
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Chris Bergin on 08/01/2017 01:02 PM
Ironically, Ares V switched back to RS-25s after they conducted a study on RS-68s with Ares V and showed it struggled. They went as far as six RS-68s and two 5.5 SRBs for Ares V after five RS-68s and two five seg SRBs couldn't lift Altair on Lunar missions.

Wrote an article in 2008 on it. Article is several CMS's ago so looks messy, best to just copy and paste it:

Quote
The previous Ares V baseline was a 10 meter core, powered by 5 RS-68 engines from the Delta IV vehicle – flanked by two 5.0 segment Solid Rocket Boosters as to be used on the Ares I’s First Stage. The J-2X powered Upper Stage had already changed from 8.4 meters in diameter to a 10 meter stage, flush with the Core Stage.

However, the earlier Ares-V configuration has been suffering from an inability to close the performance requirements for being able to heavy lift the four-man Altair Lunar Lander being planned. With Ares I lifting the Orion spacecraft, the Ares-V needs to push 75.1 mT of payload through Trans-Lunar Injection (TLI) but was only able to push 64.6 mT.

This new more powerful configuration, identified as the ‘LV 51.00.48’ is now able to put 71.1 mT through TLI. While this configuration still can not reach its targets, this is a clear improvement towards closing the performance requirements NASA has for the Lunar architecture.

Each new reusable 5.5 segment SRB, will contain over 1.5 million pounds of propellant which will produce a peak of 3,774,000 million lbs of thrust and will have a vacuum Isp of 275.5 seconds. The 38 percent larger SRB’s will burn for 116 seconds – a full 8 seconds shorter burn time than Space Shuttle – before being jettisoned.

They feature a new ‘333-07 Trace’ PBAN solid propellant mix derived from that currently used by the Shuttle, although there is still the option to go to a new HTPB mix if the trade studies are favorable.

To accommodate the new lengthened boosters, the Liquid Hydrogen Tank on the Core Stage has been stretched by 190.3”. Together with a proportional stretch to the Liquid Oxygen Tank this growth puts the new baseline vehicle at 381.1 ft tall – nearly 20 feet taller than the old baseline.

To save weight, this version of Ares V assumes all non-pressurized structures on the Core Stage will be built out of new IM7 composite materials instead of more traditional Aluminum-Lithium alloy.

The 6 RS-68 engines powering the Core will fly at 108 percent power levels (6 percent higher than used on Delta-IV currently) and will each produce 702,055 lbs of thrust and have an Isp of 365 seconds at sea level and will have 797,000 lb of thrust and will have an Isp of 414 seconds in a vacuum.

Total expected burn time for the Core will be 303 seconds and the 6 main engines will produce a maximum of 4.17G during the launch. The EDS will likewise be constructed out of mostly composite materials.

The J-2X engine will burn at the 100 percent power level for the orbital insertion burn, but will burn at the 81 percent power level for TLI. The reduced thrust optimizes the Isp for the mass-critical TLI burn. The insertion altitude has been raised from 120 nmi to 131.5 nmi circular.

Total roll out weight with the crawler and the MLP (Mobile Launch Platform) will be approximately 18 million lbs, which exceeds the capability of the existing crawlerway rated for 16.8 million lbs. The ability for Ares V to remain within its budget targets is now considered a 4×4 risk on the standard 5×5 risk matrix.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 08/01/2017 01:31 PM
New build is even better. RS-25D to RS-25E means it's far cheaper, but all with that lovely reliability.
To pull 25D out of the shed and build up 25E production capacity costed around $70mil/engine ($1.18bil / 16engines) and the new 25E will also cost about the same ($413mil / 6engines, 4flying) compared to RS-68 at around $20mil/engine and fewer per core compared to 25s.

There is no such alternative, if it includes RS-68.  RS-68 and SRB are not viable, much like air start SSME.
Jim, You're very knowledgeable, but mistaken here. RS-68 and SRB is an engineering challenge, not an impossibility. NASA's conclusion was regen at around $150mil in development and doubling the unit cost. I disagree with messing up an inexpensive, robust and impeccably-reliable engine and instead previously outlined a boattail that puts existing 68s in a more benign environment then they have under Delta IV. I'm sure there's other options, possibly some better, to address this engineering problem. -- Boattail post;
https://forum.nasaspaceflight.com/index.php?topic=38069.msg1706197#msg1706197

Still didnt address three main problem.  Radiant heating of the nozzles from the SRM plume.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 08/01/2017 04:41 PM
... Wrote an article in 2008 on it. Article is several CMS's ago so looks messy, best to just copy and paste it:
Quote
... the Ares-V needs to push 75.1 mT of payload through Trans-Lunar Injection (TLI) but was only able to push 64.6 mT. ... This new more powerful configuration, identified as the ‘LV 51.00.48’ is now able to put 71.1 mT through TLI.
...
Total expected burn time for the Core will be 303 seconds and the 6 main engines will produce a maximum of 4.17G during the launch.
...
Total roll out weight with the crawler and the MLP (Mobile Launch Platform) will be approximately 18 million lbs, which exceeds the capability of the existing crawlerway rated for 16.8 million lbs. ...
That's extraordinary. Refreshing memory and it's still jaw-dropping how absurd Constellation was.

Still didnt address three main problem.  Radiant heating of the nozzles from the SRM plume.
Without bending light, the only possible radiant heating in that boattail design would be through the 68's own exhaust and against their bell's inner walls.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 08/02/2017 05:01 PM
... Wrote an article in 2008 on it. Article is several CMS's ago so looks messy, best to just copy and paste it:
Quote
... the Ares-V needs to push 75.1 mT of payload through Trans-Lunar Injection (TLI) but was only able to push 64.6 mT. ... This new more powerful configuration, identified as the ‘LV 51.00.48’ is now able to put 71.1 mT through TLI.
...
Total expected burn time for the Core will be 303 seconds and the 6 main engines will produce a maximum of 4.17G during the launch.
...
Total roll out weight with the crawler and the MLP (Mobile Launch Platform) will be approximately 18 million lbs, which exceeds the capability of the existing crawlerway rated for 16.8 million lbs. ...
That's extraordinary. Refreshing memory and it's still jaw-dropping how absurd Constellation was.

Still didnt address three main problem.  Radiant heating of the nozzles from the SRM plume.
Without bending light, the only possible radiant heating in that boattail design would be through the 68's own exhaust and against their bell's inner walls.

Wrong again.  The plume is radiant for almost 100 feet.  The nozzles will always be in direct view of them. 

The boat tail design is also non viable
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: john smith 19 on 08/02/2017 05:40 PM

Now, what specific target are we shooting for? SSME is a very complex beast. You just can't wave a wand and magically make it cheaper. What performance levels are required? Uprating? Greater margins for HSF than prior Shuttle ones, because we want to lower our LOC/LOM numbers too?

How much are we allowed to change the engine's physical geometry/size (much of the issues were in making a compact, ground start engine for a spaceplane application). How about the feed lines, can we change them too? Can we use electrical instead of hydraulic in certain places? Can we use new materials that will last 1-2 times instead of 30+?

Can we eliminate whole portions of the design that might sacrifice 2-15 sec-1 of iSP?

Now, we take all of that and run it on the test stand and compare numbers? Can we prove we've met requirements and retained acceptable reliability? Tall order.
Indeed.

The age old myth of the "small change."

So if it's that small (that it does not need full qualification testing) how will it give any significant improvements?

If it's so big to need full qualification testing how can you afford it in terms of cost or schedule delay?
Title: Hydrogen burning Raptor
Post by: Robert Willis on 08/02/2017 06:13 PM
Engines designed to burn LH2 such as RD-0120 & RD-0146 have been test fired burning liquid methane with very little modification. Seeing as Raptor was originally designed to run on Hydrogen, how difficult would it be to produce an LH2 burning version of Raptor having a high component commonality with the currently planned CH4 production model? I would guess that such an engine would have lower thrust, but higher ISP. Can anyone out there do rough calculations/estimate?

Considering that NASA is paying Aerojet-Rocketdyne an obscene 1.6 billion dollars for just six new RS-25s, would it not make sense to replace these with LH2 Raptors for SLS?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 08/02/2017 06:26 PM
Wrong again.  The plume is radiant for almost 100 feet.  The nozzles will always be in direct view of them. 
The boat tail design is also non viable

If an SRB plume is an infinite 180 degrees, it still won't effect the 68's if using a boattail. They're still shielded (other than the absolute lip viewed from directly below, and I mentioned an extra ablative ring here may be necessary, but unlikely), they have constant airflow, no radiant effect on each other, no GG recirculation and purge line rerouted - that's kinda the whole point of building a boattail. If you don't know that, how can understand the design well enough to then call it non viable? FYI: It is, much cheaper and faster to develop than alternatives, uses existing knowledge-bases and infrastructure, weight is minimal, drag is reduced and it looks goooood (something engineers often forget is important).
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Space Ghost 1962 on 08/02/2017 07:08 PM

Now, what specific target are we shooting for? SSME is a very complex beast. You just can't wave a wand and magically make it cheaper. What performance levels are required? Uprating? Greater margins for HSF than prior Shuttle ones, because we want to lower our LOC/LOM numbers too?

How much are we allowed to change the engine's physical geometry/size (much of the issues were in making a compact, ground start engine for a spaceplane application). How about the feed lines, can we change them too? Can we use electrical instead of hydraulic in certain places? Can we use new materials that will last 1-2 times instead of 30+?

Can we eliminate whole portions of the design that might sacrifice 2-15 sec-1 of iSP?

Now, we take all of that and run it on the test stand and compare numbers? Can we prove we've met requirements and retained acceptable reliability? Tall order.
Indeed.

The age old myth of the "small change."

So if it's that small (that it does not need full qualification testing) how will it give any significant improvements?

If it's so big to need full qualification testing how can you afford it in terms of cost or schedule delay?
Correct.

Was J2-X worth the time/money over J2-S? If they had kept with J2-S mostly, it might have been used. J2-X likely won't be used.

We've been down the J2/SSME/STBE/RS68/RS68A "improvement" path many, many times before.

IMHO, the problem here is not the "possible". The problem is different. Clarity of a definite, long term need to fill, with a commitment to meet the cost/performance needs is more likely.

The RS68 program was a mix of good (first commercial engine development, timely, high thrust hydrolox w/o solids) and bad (missed performance targets, chose poorly on "cheap" components due to SSME decisions, too high threshold on frequency of use for cost knee in curve, ...).

And that was the prior attempt at "cheap" hydrolox.

Aerojet Rocketdyne does not find it easy to do cheap hydrolox.

Reminds of "Young Frankenstein": "... because we still have nightmares from five times before. (https://getyarn.io/yarn-clip/ff161f9a-f97a-4b5a-ac01-8567bbbc6f68)".
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: john smith 19 on 08/02/2017 10:28 PM
Was J2-X worth the time/money over J2-S? If they had kept with J2-S mostly, it might have been used. J2-X likely won't be used.
That would be the new J2-X.
The RS68 Combustion Chamber
The RS68 Gas Generator
The RS68 Nozzle
The RS68Injectors
The RL10 nozzle extension
Of which only the RL10 nozzle was a crew rated engine component
And
The J2 turbopump design.
Which (apparently) was all you needed to turn an RS68 into a crew rate engine.  :(

Finding information on the original J2-S and J2-X programmes was very difficult for me but the achievements of the original programme were remarkable.
Converting it to a large size gas tapoff cycle (the only option that can give potentially give the high chamber of staged combustion with the simplicity of an expander cycle).
Moving from pressurized start tanks to cartridge starts but more impressively moving to tank head pressure starting (when they realized it was the high back pressure from the CC cooling system that was preventing turbine spin up).
An pressure fed idle mode.
Pumps to allow start up with   50% vapour in the inlet at < 2 bar absolute. 
And planning for a plug nozzle version.

I found the modern programme quite underwhelming by comparison.  :(
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 08/08/2017 01:57 PM

If an SRB plume is an infinite 180 degrees, it still won't effect the 68's if using a boattail. They're still shielded (other than the absolute lip viewed from directly below, and I mentioned an extra ablative ring here may be necessary, but unlikely), they have constant airflow, no radiant effect on each other, no GG recirculation and purge line rerouted - that's kinda the whole point of building a boattail. If you don't know that, how can understand the design well enough to then call it non viable?

Still not viable.

A.  There is no changing the 68 just for SLS.  It negates the benefit of sharing the same production line and flight history.
b.  Obviously, you didn't know that the boat tail didn't work on Delta IV so how do you know it is viable for this kludge. 
c.  There still is  radiant effect from boat tail to nozzle
d.  The large mass this huge boat tail is another strike against the "benefits" of the RS.
e. and there is the fore mentioned ISP issue that makes the core tanks too big.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 08/08/2017 02:05 PM
FYI: It is, much cheaper and faster to develop than alternatives, uses existing knowledge-bases and infrastructure, weight is minimal, drag is reduced and it looks goooood (something engineers often forget is important).


not one of those is true.   And it certainly does not looks good. 
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 08/08/2017 05:43 PM
FYI: It is, much cheaper and faster to develop than alternatives, uses existing knowledge-bases and infrastructure, weight is minimal, drag is reduced and it looks goooood (something engineers often forget is important).


not one of those is true.   And it certainly does not looks good.

I guess I never noticed that boat tail before... This looks like a M+ (5,4) core - but this RS-68 protection doesn't seem to be used for all launches of that configuration. Was this just used for one of the early flights?
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: mike robel on 08/08/2017 06:50 PM
I know it doesn't appear on the Delta IV and it don't think it flies with a Delta without any SRMs, so only the M+,
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 08/08/2017 06:59 PM
I know it doesn't appear on the Delta IV and it don't think it flies with a Delta without any SRMs, so only the M+,

But it doesn't appear on most M+ launches, it seems (see image with 4 SRBs), so that's why I'm wondering if it is a something that was only used for the first few launches.

(The only launch images that show the skirt/boattail appear to be from the GOES-N launch, although it could be present in some others - difficult to see in the glare of the SRBs)
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 08/10/2017 02:55 AM
Boattail description post; https://forum.nasaspaceflight.com/index.php?topic=38069.msg1706197#msg1706197
A.  There is no changing the 68 just for SLS.  It negates the benefit of sharing the same production line and flight history.
b.  Obviously, you didn't know that the boat tail didn't work on Delta IV so how do you know it is viable for this kludge. 
c.  There still is  radiant effect from boat tail to nozzle
d.  The large mass this huge boat tail is another strike against the "benefits" of the RS.
e. and there is the fore mentioned ISP issue that makes the core tanks too big.
a- No significant changes to 68's and certainly not any to effect their immaculate record. As mentioned the primary alterations are lengthening the GG exhaust and piping the purge lines to outside the boattail - so it doesn't explode upon ignition. A possibility is to remove, rather than simply disable roll control, and added ablative on the bottom few inches of the nozzle just in case.
b- DIV never shielded the nozzle and never introduced airflow inside the boattail as I've done. As mentioned the boattail extends below the nozzle with enough room for articulation. The space between the boattail and nozzle immediately develops a vacuum which is filled by the inlets beside the thrust structure, creating airflow.
c- Yep, the boattail will absorb (not reflect) and re-radiate heat including the thermal panels separating the engines. But this heat flux is much less than 68's get from GG exhaust recirulation, now eliminated by airflow, and what remains once out of the atmosphere is still insignificant.
d- Define "large". It's more than zero and adds to an already heavy engine, but that's irrelevant when compared to alternatives (PoR) it actually increases performance of the rocket, its safety, reliability, while reducing cost and development. Forest from the trees.
e- Love the pic and your experience actually building rockets, but a designer you're not. Reducing the core mass, propellant load and increasing the thrust increases the payload to orbit. Specific impulse is insignificant compared to a properly-design rocket with adequate thrust. I'd appreciate your input on Michoud's minor modifications necessary to build an actually functional SHLV.
6barrel core+68s+J-2X https://forum.nasaspaceflight.com/index.php?topic=38069.msg1705330#msg1705330
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 08/10/2017 06:36 AM
a- No significant changes to 68's and certainly not any to effect their immaculate record. As mentioned the primary alterations are lengthening the GG exhaust and piping the purge lines to outside the boattail - so it doesn't explode upon ignition. A possibility is to remove, rather than simply disable roll control, and added ablative on the bottom few inches of the nozzle just in case.
b- DIV never shielded the nozzle and never introduced airflow inside the boattail as I've done. As mentioned the boattail extends below the nozzle with enough room for articulation. The space between the boattail and nozzle immediately develops a vacuum which is filled by the inlets beside the thrust structure, creating airflow.

d- Define "large". It's more than zero and adds to an already heavy engine, but that's irrelevant when compared to alternatives (PoR) it actually increases performance of the rocket, its safety, reliability, while reducing cost and development. Forest from the trees.
e- Love the pic and your experience actually building rockets, but a designer you're not.
F.  Reducing the core mass, 
G.I'd appreciate your input on Michoud's minor modifications necessary to build an
H. actually functional SHLV.
i. 6barrel core+68s+J-2X

a.  Those are enough changes to affect the RS-68 and separate it from the Delta IV version.
b.  You haven't done any.  Much less produce a working design
d.  Exactly, Forest from the trees. This design is irrelevant.  POR is what it is. 
e.  You are neither.
f.  You are increasing it.
g.  I have nothing to do with Michoud or SLS design/production
h.  That would be SLS.  There isn't going to be anything else related.
i. There isn't going to be another vehicle that uses RS-68's or J-2X.  Both engine programs are dead or dead ends.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 08/10/2017 04:58 PM
I have nothing to do with Michoud or SLS design/production
Pity, as I only have images to derive dimensions of their facility. Notably the upper gantry crane appears high enough for a 6barrel core, but the lower crane isn't. After manufacturing is complete the core is given a shower, but the tub's lip is too high for a 6barrel to step over without hitting its head. I've a wet saw and spare time if they need a hand  ;D

Exactly, Forest from the trees. This design is irrelevant.  POR is what it is.
The program of record - SLS with it's design and mission decisions - is the tree. Human exploration is the forest that needs to be addressed. If the PoR, or RS-25, or administrators, or specific specs on mass and isp become the defining arguments, we've all lost site of the forest. The PoR and RS-25 "is what it is", which means they're sidenotes easily replace toward the goal of human exploration. If something better comes along, whether it's proposals I've made or others, do it. Forest from the trees.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 08/10/2017 05:11 PM
The program of record - SLS with it's design and mission decisions - is the tree.

no, RS-68's, J-2s or SRB's are trees.

If something better comes along,

There will be nothing that is better that will/can come along with those components. 
Actually, "nothing" is better wrt those components.
Human exploration can be addressed without them

Forest from the trees.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Khadgars on 08/10/2017 07:35 PM
Propylox, I would appreciate it if you would stop beating a dead horse.  There is no need to hash this out any further.

It is as Jim states, RS-25 or bust for SLS and RL-10 for US.  If you want to discuss this further, please create a dedicated thread for that hypothetical as it has nothing to do with the POR.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: okan170 on 08/10/2017 09:16 PM
I know it doesn't appear on the Delta IV and it don't think it flies with a Delta without any SRMs, so only the M+,

But it doesn't appear on most M+ launches, it seems (see image with 4 SRBs), so that's why I'm wondering if it is a something that was only used for the first few launches.

(The only launch images that show the skirt/boattail appear to be from the GOES-N launch, although it could be present in some others - difficult to see in the glare of the SRBs)

I actually noticed this a bit ago while building the CG Delta IV, and asked Tory Bruno on twitter who referred me to ULA's official account.  Apparently it was an aero skirt that was only flown three times:

https://twitter.com/ulalaunch/status/811049041534603265

It'd be interesting to know more about this skirt and the reasons for its original inclusion and eventual deletion, but thats moving kind of off-topic for this thread.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 08/10/2017 09:20 PM

It'd be interesting to know more about this skirt and the reasons for its original inclusion and eventual deletion, but thats moving kind of off-topic for this thread.

Protect the RS-68 from SRM heating
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lars-J on 08/10/2017 10:20 PM
I know it doesn't appear on the Delta IV and it don't think it flies with a Delta without any SRMs, so only the M+,

But it doesn't appear on most M+ launches, it seems (see image with 4 SRBs), so that's why I'm wondering if it is a something that was only used for the first few launches.

(The only launch images that show the skirt/boattail appear to be from the GOES-N launch, although it could be present in some others - difficult to see in the glare of the SRBs)

I actually noticed this a bit ago while building the CG Delta IV, and asked Tory Bruno on twitter who referred me to ULA's official account.  Apparently it was an aero skirt that was only flown three times:

https://twitter.com/ulalaunch/status/811049041534603265

It'd be interesting to know more about this skirt and the reasons for its original inclusion and eventual deletion, but thats moving kind of off-topic for this thread.

Thanks! I guess either they changed the SRB exhaust angle or they realized that the RS-68 did not need the added protection.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Lar on 08/11/2017 02:36 AM
This thread is about the RS-25. It's not about Atlas, Delta, the RS-68, SpaceX, the Proton, or cheese. Or even LEGO elements!!! Yes some argument could be made that it's related but make sure it's clear in the posts how. Or we get people reporting...
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 08/12/2017 06:37 AM
Propylox, I would appreciate it if you would stop beating a dead horse.
It is as Jim states, RS-25 or bust for SLS and RL-10 for US.  If you want to discuss this further, please create a dedicated thread for that hypothetical as it has nothing to do with the POR.
NASA defends decision to restart RS-25 production, rejects alternatives
What thread is acceptable to reject NASA's decision to use RS-25 and propose superior alternatives that reduces the cost per rocket (at least $200million per core), of the entire program (eliminates Advanced Boosters, creates a single and less expensive US) while increasing the safety, reliability and performance of SHLV for immediate use and mission funding instead of decades of further development?

The only "dead horse" here is the assertion that the PoR is infallible, the best, set in stone, and unquestionable! without addressing why it's so bad, why better options aren't being pursued, what those better options are, and why asking these valid questions in the dedicated thread is riling feathers without providing valid answers.
(Plus the contrary, grumpy assertion that SLS and any alternative will be cancelled, so don't talk about them).

SLS Mythbuster - I reject your reality and substitute my own.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Endeavour_01 on 08/12/2017 07:43 AM
The only "dead horse" here is the assertion that the PoR is infallible, the best, set in stone, and unquestionable!

I don't think anyone here has argued any of those things. You presented your ideas and were then presented with facts about how those ideas are unrealistic to implement. RS-25 is the best engine for SLS, especially at this stage of development.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 08/12/2017 01:19 PM

The only "dead horse" here is the assertion that the PoR is infallible, the best, set in stone, and unquestionable! without addressing why it's so bad, why better options aren't being pursued, what those better options are, and why asking these valid questions in the dedicated thread is riling feathers without providing valid answers.
(Plus the contrary, grumpy assertion that SLS and any alternative will be cancelled, so don't talk about them).

Wrong on every count.
It is none of those things. There isn't going to be any money or desire to address any those things. There isn't a reason for SLS to exist in the first place.  So there is no reason to look for better options. It is SLS or nothing.
Govt managed launch vehicles are a dead end.  Especially, ones with no real mission. 

SLS is not going to be changed or upgraded.  There isn't going to be an SLS follow on.   NASA or the US govt has no need for such vehicles.  The RS-68 is at its end.  Production is almost finished.  EUS design is nearly finalized.  There is no champion for J-2X and hence it is dead.  Large segmented SRMs will be a thing of the past after SLS since Spacex, ULA, and Blue Origin don't need them

There isn't going to be any SLS alternative.  SLS is the POR and it is already on shaky ground.  There is no need, incentive or reason for an alternative.  Nor is there any drive to do so. 

Thinking otherwise means one has no concept of reality.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: oldAtlas_Eguy on 08/12/2017 05:22 PM
The basic premise put forth by Congress was NASA only had X number of years to produce a SHLV. That timeline was insufficient for an engine development program. And we are seeing that even then without an engine development program that they are still not able to meet the stipulated schedule. If NASA had said in 2012 that it would take 10 years (2022) to do a first launch of SLS, Congress might not have created the program and killed Orion as well. Remember this was in FY2012 where there was only the investigations into Commercial Crew and commercial SHLVs (50+mt) were only power points with very questionable capabilities and very questionable schedules if they even came to exist. NASA could not say no they could not do it. Many other programs could have been hurt or even cancelled that NASA wanted very much.

So there was only the one choice for engine of the core and that was the RS-25. For the US there was options but the US program was unfunded and the design delayed until only recently. In order for the SLS with an US to hit the targets they needed a high ISP and light weight engine which the J-2X was not leaving the RL-10 as the only choice. What we have now is the result of a cascade of forced decisions a certain way all due to schedule pressure.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: M_Puckett on 08/12/2017 07:00 PM
"There isn't going to be any SLS alternative."

I disagree, depending on your definition of alternative.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Jim on 08/12/2017 07:08 PM
"There isn't going to be any SLS alternative."

I disagree, depending on your definition of alternative.

A vehicle using shuttle based SRBs and MAF built tanks
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: M_Puckett on 08/12/2017 09:15 PM
I'll buy that Jim.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Space Ghost 1962 on 08/14/2017 07:13 PM
Thinking otherwise means one has no concept of reality.
Yes, ... Congress. Never stops/stopped them.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: Propylox on 09/13/2017 04:49 AM
Thinking otherwise means one has no concept of reality.
Yes, ... Congress. Never stops/stopped them.
Especially if/once they're informed a switch from RS-25 to RS-68 saves at least $200million per core, plus at least $20million savings on the upper stage, plus eliminates almost all the funding requirements allocated to the Advanced Booster and EUS programs.
Every Congressperson's eyes grow wide at that while NASA administrators and lobbyists begin wondering what new hardware and programs all those savings can be re-allocated to. That payload, performance, development and construction time are all reduced is just icing.

-- All by correcting original and terminal mistake of choosing RS-25s. If only there was a new Prez and Space Council to readdress past blunders.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: woods170 on 09/13/2017 06:32 AM
Thinking otherwise means one has no concept of reality.
Yes, ... Congress. Never stops/stopped them.
Especially if/once they're informed a switch from RS-25 to RS-68 saves at least $200million per core, plus at least $20million savings on the upper stage, plus eliminates almost all the funding requirements allocated to the Advanced Booster and EUS programs.
Every Congressperson's eyes grow wide at that while NASA administrators and lobbyists begin wondering what new hardware and programs all those savings can be re-allocated to. That payload, performance, development and construction time are all reduced is just icing.

-- All by correcting original and terminal mistake of choosing RS-25s. If only there was a new Prez and Space Council to readdress past blunders.
As long as US Congress holds the purse-strings no new president, let alone a Space Council, will be able to change anything.
https://arstechnica.com/science/2017/07/elon-musk-knows-whats-ailing-nasa-costly-contracting/

Just look at history. When Shuttle went away it was replaced with CxP, with all of it's mistakes. And when that went away it was replaced by SLS/Orion with all of it's mistakes. All of them were/are bloated programs.

But I digress.
Title: Re: NASA defends decision to restart RS-25 production, rejects alternatives
Post by: AncientU on 09/13/2017 04:55 PM
And that is why space is so expensive...

Wait, wrong thread.