Author Topic: RS-68 CLV First Stage  (Read 79656 times)

Offline publiusr

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Re: RS-68 CLV First Stage
« Reply #100 on: 10/26/2007 05:56 pm »
But that would be a fresh start now. If it had used two RD-180's from the beginning...

Offline rsp1202

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Re: RS-68 CLV First Stage
« Reply #101 on: 10/26/2007 06:05 pm »
There's a lot to be said for having a common core for both CLV and CaLV, whether that be Direct or Atlas Phase whatever.

With lack of an American-made kero-lox engine, it's fortunate there was a -68 to turn to.

Offline Propforce

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Re: RS-68 CLV First Stage
« Reply #102 on: 10/26/2007 07:59 pm »
Quote
Jim - 26/10/2007  10:40 AM

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publiusr - 26/10/2007  1:17 PM

 Had Atlas V used RD-170 and not RD-180--it would have been a great contenter for CLV. An Americanized Zenit with smaller strap-ons would look rather like a scaled up Delta II.

That has no bearing.  2 RD-180's could be used

RD-170 is much simpler integration.

Offline Propforce

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Re: RS-68 CLV First Stage
« Reply #103 on: 10/26/2007 08:05 pm »
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kraisee - 26/10/2007  10:55 AM

LM actually did an analysis on that a while back - for their Phase 2 vehicle - and found that there were better engine-out options if two RD-180's were used instead of a single RD-171 (BTW, needs to be the 171 variant because 170 hasn't got full-range gimbal control).

Ross.


Let's just entertain this scenario a bit.  At lift off, most LV has a T/W ratio between 1.1 to 1.4.  All of sudden you have an "engine out scenario" with ONE of the RD-180.  Now you have a T/W ratio of 0.5 to 0.7.  No matter how you cut it, you do not have enough lift to keep that vehicle IN the air and OFF the ground.  Also, the other RD-180's thrust is now off-center thereby tilting the vehicle over and heading directly INTO the ground with its FULL POWER!!  Now how does that help mission reliability?

Offline kraisee

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Re: RS-68 CLV First Stage
« Reply #104 on: 10/26/2007 08:29 pm »
The engine out was available later in the first stage flight, not at liftoff.   I forget precisely where it became a possibility, but probably somewhere about half way to tow-thirds of the way through the first stage burn.

I'm not sure there has ever been a successful rocket designed to be able to cope with an engine out around T+1s.   N-1 might have been, but it was never successful.

Ross.
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Offline edkyle99

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Re: RS-68 CLV First Stage
« Reply #105 on: 10/26/2007 09:56 pm »
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kraisee - 26/10/2007  3:29 PM

I'm not sure there has ever been a successful rocket designed to be able to cope with an engine out around T+1s.  

I think that Space Shuttle can suffer an SSME failure, assuming that it shuts down nice, right off the pad and make an RTLS abort.  

 - Ed Kyle

Offline kraisee

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Re: RS-68 CLV First Stage
« Reply #106 on: 10/26/2007 10:10 pm »
Good point, but I was really talking about a mission which still proceeds to successful orbital insertion.

Ross.
"The meek shall inherit the Earth -- the rest of us will go to the stars"
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Offline Propforce

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Re: RS-68 CLV First Stage
« Reply #107 on: 10/26/2007 11:57 pm »
Quote
edkyle99 - 26/10/2007  2:56 PM

Quote
kraisee - 26/10/2007  3:29 PM

I'm not sure there has ever been a successful rocket designed to be able to cope with an engine out around T+1s.  

I think that Space Shuttle can suffer an SSME failure, assuming that it shuts down nice, right off the pad and make an RTLS abort.  

 - Ed Kyle


That's because it still has that 2 MILLION pound thrust going full blast during the initial ascent.  After that, then it can still ascent with only 2 engines.  



Offline Propforce

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Re: RS-68 CLV First Stage
« Reply #108 on: 10/27/2007 12:12 am »
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kraisee - 26/10/2007  1:29 PM

The engine out was available later in the first stage flight, not at liftoff.   I forget precisely where it became a possibility, but probably somewhere about half way to tow-thirds of the way through the first stage burn.

Ross.

That's a valid point.  However; history has shown that when liquid rocket engines fail, they fail in the first few second of start (thus the hold-down bolts, etc.).  I don't think using the last 1/3 of boost phase as "engine-out" justification for multiple engines is a good one.  If they admit that they can only buy the RD-180 engines, then perhap that's a more reasonable explanation.





Offline tnphysics

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Re: RS-68 CLV First Stage
« Reply #109 on: 10/27/2007 05:23 pm »
Quote
kraisee - 26/10/2007  4:29 PM

The engine out was available later in the first stage flight, not at liftoff.   I forget precisely where it became a possibility, but probably somewhere about half way to tow-thirds of the way through the first stage burn.

I'm not sure there has ever been a successful rocket designed to be able to cope with an engine out around T+1s.   N-1 might have been, but it was never successful.

Ross.

Falcon 9. But it has never flown.

Offline JIS

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Re: RS-68 CLV First Stage
« Reply #110 on: 10/31/2007 08:33 am »
Are there any news about humanrating RS-68? How long would it take? How much is the estimated cost? The original development took 4 and half year and cost about $500mil.
I think that the specs of new engine is pretty nailed down by AF and NASA requirements. I expect that it will be again certified for up to 350s burn. As the certification for human rating is very expensive proces I would expect the develpment cost and time to be very similar to the orginal $500mil and 4 and half year. I suppose that the real development will start only after STS retirement.
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Offline TrueGrit

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Re: RS-68 CLV First Stage
« Reply #111 on: 10/31/2007 08:05 pm »
Lets just say your $500mil is off base...  Boeing wrote off nearly $2bil on Delta IV development losses and government only kicked in $500mil...

Offline Jim

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Re: RS-68 CLV First Stage
« Reply #112 on: 10/31/2007 08:45 pm »
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TrueGrit - 31/10/2007  5:05 PM

Lets just say your $500mil is off base...  Boeing wrote off nearly $2bil on Delta IV development losses and government only kicked in $500mil...

Offbase high.  He was only talking RS-68 and not the whole Delta IV development

Offline kraisee

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Re: RS-68 CLV First Stage
« Reply #113 on: 10/31/2007 09:06 pm »
RS-68 remained on-budget AFAIK.

Rocketdyne's own documentation claims the entire development program cost ~$500m through to first flight.

Ross.
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Offline TrueGrit

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Re: RS-68 CLV First Stage
« Reply #114 on: 10/31/2007 09:06 pm »
Understood...  Yet I remember quite a few engien testing incidences and a particular redesign activity that would dispute the "on cost" claim.

As for manrating...  Total Delta IV manrating was priced around $500mil during the OSP days, and only a portion was engine related.  NASA will likely be able to develop the RS-68B for Ares V for less than half what the Delta IV manrating would have been.

Offline Jim

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Re: RS-68 CLV First Stage
« Reply #115 on: 10/31/2007 09:20 pm »
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TrueGrit - 31/10/2007  6:06 PM

As for manrating...  Total Delta IV manrating was priced around $500mil during the OSP days, and only a portion was engine related.  NASA will likely be able to develop the RS-68B for Ares V for less than half what the Delta IV manrating would have been.

It was much less than $500mil.  A new crew access tower was $500mil

Offline Propforce

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Re: RS-68 CLV First Stage
« Reply #116 on: 10/31/2007 09:31 pm »
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kraisee - 31/10/2007  3:06 PM

RS-68 remained on-budget AFAIK.

Rocketdyne's own documentation claims the entire development program cost ~$500m through to first flight.

Ross.

Since this was an internally funded program, nobody really knows what it cost.


Offline TrueGrit

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Re: RS-68 CLV First Stage
« Reply #117 on: 10/31/2007 10:41 pm »
As for "manrating"...  The real question comes to what needds to be changed?  And then how many engines need to be tested to establish confidence?  The number of engines is the biggest factor in the costs.  In general the minimum amount of engines is 3 (1 development and 2 certification), for a significant engine upgrade.  A component certification, valves or controller, might be accomplished with only 1 engine test series.  And in general you test each engine ~2x life, which is normaly ~4x flight time.  So your talking about ~8x flight time.  It really depends on the change.

Offline Antares

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Re: RS-68 CLV First Stage
« Reply #118 on: 11/01/2007 02:30 am »
It's not as much the amount of test time as it is the design standards.  Go through all of the standards that SSME meets or is supposed to but waives.  Check if -68 meets 'em.  Fracture control and trey-redundant controller come to mind.
If I like something on NSF, it's probably because I know it to be accurate.  Every once in a while, it's just something I agree with.  Facts generally receive the former.

Offline TrueGrit

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Re: RS-68 CLV First Stage
« Reply #119 on: 11/01/2007 04:55 pm »
RS-68 was designed the same PWR and military standards that were used on SSME...  The big difference in SSME and RS-68 development is the number of engines tested prior to first flight, not the design standards.  The exceptions are in the controller design which lacks triple redundancy, no in-flight redline shutdown capability, and the main valves which lacked the SSME pneumatic backup.

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