Could a new F-1x Engine open the door for an 8.4m kerolox core for SLS?

[Prober]

Two of them together weigh less than one RS-27A, but make nearly 300,000 pounds of sea-level thrust, half-again as much as RS-27A. 

Sure but your comparing a Fast Track derivative vs a 1950’s derivative.     I agree with Downix that the RS-27A holds up well for its design.    That’s the point, the customers NASA, USAF never ordered up an upgrade so they made them as requested.  Sad story is that NASA wasted the funds over a billion on the X-33 and for that amount of funds we could have gotten a much better F-1A going.

Or consider an equal thrust comparison, roughly, of three RS-27A type engines versus four Merlin 1D engines.  The Merlin cluster would weigh less than 2/3rds as much as the RS-27 cluster, saving over a tonne of dry mass.

Jim: unproven, we have yet to see 9 engines fly.

The wisdom of smaller engines becomes clearer to me over time.  Smaller engines can have bigger expansion ratios, for better specific impulse, for example.  They take up less vertical space, saving structural mass.  And so on.  Russia has efficient engines created by clustering smaller, but more efficient, chambers. 

 - Ed Kyle

Like the 1950’s designs used on the Soyuz we are paying an arm and leg for?

[Downix]

Two of them together weigh less than one RS-27A, but make nearly 300,000 pounds of sea-level thrust, half-again as much as RS-27A. 

Sure but your comparing a Fast Track derivative vs a 1950’s derivative.     I agree with Downix that the RS-27A holds up well for its design.    That’s the point, the customers NASA, USAF never ordered up an upgrade so they made them as requested.  Sad story is that NASA wasted the funds over a billion on the X-33 and for that amount of funds we could have gotten a much better F-1A going.

I still feel that the Rockwell X-33 was a far better project, using the SSME instead of an all-new engine. If you're pushing the envelope, you retain as much proven systems to eliminate the potential failure points.

Or consider an equal thrust comparison, roughly, of three RS-27A type engines versus four Merlin 1D engines.  The Merlin cluster would weigh less than 2/3rds as much as the RS-27 cluster, saving over a tonne of dry mass.

Jim: unproven, we have yet to see 9 engines fly.

We have seen 8 RS-27A's fly in a cluster before, or rather, 8 H-1's.

The wisdom of smaller engines becomes clearer to me over time.  Smaller engines can have bigger expansion ratios, for better specific impulse, for example.  They take up less vertical space, saving structural mass.  And so on.  Russia has efficient engines created by clustering smaller, but more efficient, chambers. 

 - Ed Kyle

Like the 1950’s designs used on the Soyuz we are paying an arm and leg for?

Soyuz uses a clustered combustion chamber design for its engines, so you both have made your points.

[WulfTheSaxon]

We have seen 8 RS-27A's fly in a cluster before, or rather, 8 H-1's.

I was wondering how long it would take before H-1s got mentioned. 

[Downix]

Because you used two of them.

Two of them together weigh less than one RS-27A, but make nearly 300,000 pounds of sea-level thrust, half-again as much as RS-27A. 

I double checked your claim here.

The RS-27 weighs in at 881kg, while reports put the Merlin 1D at around 450 kg. This means that no, two of them together do not weigh less. The difference between the two setups is less pronounced than I'd previously thought.  I'm actually rather impressed with the antique, honestly.

In any case, they have the know how for producing an RP-1 engine. This ability does not just go away the moment the orders care filled. Otherwise how do they fill the next order when that comes in? Does Ford fire its entire staff and burn down the factory at the end of a model year? Of courses not. Neither would PWR or else they would have been out of business decades ago.

[edkyle99]

Because you used two of them.

Two of them together weigh less than one RS-27A, but make nearly 300,000 pounds of sea-level thrust, half-again as much as RS-27A. 

I double checked your claim here.

The RS-27 weighs in at 881kg, while reports put the Merlin 1D at around 450 kg.

PWR's own web page says that RS-27A weighs 1,147.6 kg.
http://www.pw.utc.com/products/pwr/propulsion_solutions/rs-27a.asp

 - Ed Kyle

[Downix]

Because you used two of them.

Two of them together weigh less than one RS-27A, but make nearly 300,000 pounds of sea-level thrust, half-again as much as RS-27A. 

I double checked your claim here.

The RS-27 weighs in at 881kg, while reports put the Merlin 1D at around 450 kg.

PWR's own web page says that RS-27A weighs 1,147.6 kg.
http://www.pw.utc.com/products/pwr/propulsion_solutions/rs-27a.asp

 - Ed Kyle

Wet or dry, Ed? Compared to wet or dry Merlin 1D?

[Robotbeat]

Hey, guys, is anyone else wondering if a new F-1x Engine could open the door for an 8.4m kerolox core for SLS?

But seriously, PWR is not in the same class as SpaceX when it comes to kerolox development and manufacturing right now. Even IF PWR were making RS-27As right now (they aren't and won't), the volume is FAR less than SpaceX's volume of Merlins (by at least an order of magnitude right now). And PWR's experience developing new kerolox engines all the way through to completion is even further behind SpaceX's.

Of course, PWR is JUST as far ahead of SpaceX when it comes to hydrolox... (more, actually)

Jim and Ed are right, though. SpaceX is the US's king of kerolox right now. Undisputed until perhaps Aerojet starts producing AJ-26-500s (if that ever happens).

[Downix]

Hey, guys, is anyone else wondering if a new F-1x Engine could open the door for an 8.4m kerolox core for SLS?

But seriously, PWR is not in the same class as SpaceX when it comes to kerolox development and manufacturing right now. Even IF PWR were making RS-27As right now (they aren't and won't), the volume is FAR less than SpaceX's volume of Merlins (by at least an order of magnitude right now). And PWR's experience developing new kerolox engines all the way through to completion is even further behind SpaceX's.

Of course, PWR is JUST as far ahead of SpaceX when it comes to hydrolox... (more, actually)

Jim and Ed are right, though. SpaceX is the US's king of kerolox right now. Undisputed until perhaps Aerojet starts producing AJ-26-500s (if that ever happens).

See, this is more accurate. SpaceX is indeed the top dog of kerolox in the US right now.  Not the only contender, but they do produce more engines at this time than anyone. Their design is far more modern than the other kerolox engine available for order at this time which is built in the US, the RS-27A. When Aerojet starts cranking out their own engine, then we will need to re-assess.

[baldusi]

Who would be top dog if AMROSS starts producing in the US? Let's remember that an Energomash presentation had the RD-175 asigned to Energia-K/SLS.

[Prober]

Who would be top dog if AMROSS starts producing in the US? Let's remember that an Energomash presentation had the RD-175 asigned to Energia-K/SLS.

Just wait until the F-1 comes back 

[Lars_J]

See, this is more accurate. SpaceX is indeed the top dog of kerolox in the US right now.

I guess there was a misunderstanding then - which explains why you brought up the F-1. All we were arguing was about *now*, not historically.

[Downix]

See, this is more accurate. SpaceX is indeed the top dog of kerolox in the US right now.

I guess there was a misunderstanding then - which explains why you brought up the F-1. All we were arguing was about *now*, not historically.

I was more pointing out that PWR still has the capability to produce a kerolox engine, as the RS-27A demonstrates. To dismiss that capability seems dis-ingenuous to me. The points about noone having ordered one in years displayed more a lack of understanding of how PWR's customers operate than anything.  They purchase engines in bulk, 100 at a time, and PWR builds them in bulk, 100 at a time. Then the customers use up the supply until they are all used up, and order more once finished. Just because their customers have not needed to order any more since '07 does not mean that the RS-27A is gone any more than it does the SSME, RS-68 or RL-10 are gone in between their purchase. If I went to PWR and ordered 50 RS-27A's today, they'd begin churning them out. That to me says that they are in production, that if I ordered one today they would be able to start production just about immediately. That differentiates it from engines like the F-1, which they would need to take a year and a half to get back into production according to the reports.

The flip side is that their kerolox design on the books is based on a 1950's engine program.  While updated, it still is clearly an older design. SpaceX has a better engine in every category but one (thrust). SpaceX also uses a different paradigm of production, being vertically integrated, so the same rules which apply to SpaceX do not work right for PWR.

[Lobo]

Hey, guys, is anyone else wondering if a new F-1x Engine could open the door for an 8.4m kerolox core for SLS?

But seriously, PWR is not in the same class as SpaceX when it comes to kerolox development and manufacturing right now. Even IF PWR were making RS-27As right now (they aren't and won't), the volume is FAR less than SpaceX's volume of Merlins (by at least an order of magnitude right now). And PWR's experience developing new kerolox engines all the way through to completion is even further behind SpaceX's.

Of course, PWR is JUST as far ahead of SpaceX when it comes to hydrolox... (more, actually)

Jim and Ed are right, though. SpaceX is the US's king of kerolox right now. Undisputed until perhaps Aerojet starts producing AJ-26-500s (if that ever happens).

Yea!  It seems my thread has gotten a bit off topic in a PER vs SpaceX pissing match...

However, I think the point  of my thread has been answered, and a new F-1x does. NOT open the door for an 8.4m kerolox core.

[vulture4]

The principle rationale for the Shuttle to have SRBs was the lower development cost vs the original flyback booster concept, but the Shuttle SRBs have proven expensive and hazardous to process. For an ELV with a known payload requirement (particularly with kerosene, which reduces tank volume and engine size vs hydrogen) it would be safer and less expensive to emulate the Saturn V and eliminate the SRBs entirely.

[Downix]

The principle rationale for the Shuttle to have SRBs was the lower development cost vs the original flyback booster concept, but the Shuttle SRBs have proven expensive and hazardous to process. For an ELV with a known payload requirement (particularly with kerosene, which reduces tank volume and engine size vs hydrogen) it would be safer and less expensive to emulate the Saturn V and eliminate the SRBs entirely.

But take longer, the time to develop is what axed this idea (which scored highly otherwise). As it is now, the SLS is still technically taking longer than necessary.