Author Topic: RS-68 CLV First Stage  (Read 79657 times)

Offline simonbp

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RS-68 CLV First Stage
« on: 07/13/2006 01:43 am »
I got thinking the other day (dangerous, I know), about how you could replace the (soild) first stage of the Ares I with a drop-in liquid replacement. Most of the criticism I've heard WRT the CLV pertains to the first, rather than the second stage (with the exception of RL-10s vs. J-2s, and there's 40+ years of trades on that). Considering the RS-68 is going to be "NASA-ized" for the Ares V, it seems like a reasonable engine to use. Likewise, the diameter of the CLV upper stage is 5.5 meters and the Delta IV core diameter is 5.1 meters, and so a vertical scaling of it seems logical.

With that all in mind, I started running the numbers for a scaled Delta IV with the same net delta V as the SRB stage. Accounting for fuel necessary and the volumes of LH2 and LOX, I found that the tank would need to be lengthened by about 6 meters (for a total length of 46 meters). In order to have a t/w greater than 1, two RS-68s were required (though the t/w is still 76% of the SRB); also, the lower thurst lengthens the burn time by 56%.

Advantages:
  • Half the liftoff gross mass

  • Easier TVC (would single-axis gimbals and throttle vectoring work?)

  • It's not a solid :)


Disadvantages:
  • Twice the amount of engines to fail

  • Integrating two engines on a Delta IV-ish core could be difficult

  • Not recoverable, so potentially higher operational costs (though that's rather nebulous either way)



So what did I do wrong? :)

Simon ;)

Offline hyper_snyper

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Re: RS-68 CLV First Stage
« Reply #1 on: 07/13/2006 01:48 am »
I think the SRBs were one of the main drivers to the architecture we have today.  Whether thats a good thing or bad thing I don't know.  If you're going to have a RS-68 first stage you might as well just mod a Delta IV to do the job, IMO.

Offline hop

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RE: RS-68 CLV First Stage
« Reply #2 on: 07/13/2006 02:27 am »
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simonbp - 12/7/2006  6:30 PM
Not recoverable, so potentially higher operational costs (though that's rather nebulous either way)
I thought they weren't going to recover the SRB from the CLV anyway ?

The other factor is that according to the ESAS study, a single stick SRM is vastly safer than any of the alternatives.  :o

Offline mike robel

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RE: RS-68 CLV First Stage
« Reply #3 on: 07/13/2006 02:37 am »
Instead of developing a two RS-68 version of the Delta IV, you could either (1) just the Delta IV Heavy or maybe (2) use the Delta IV Medium with 4 of its smaller SRBs.  I don't that my second suggestion would handle the load, but the Heavy version sure  would...

Offline zinfab

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RE: RS-68 CLV First Stage
« Reply #4 on: 07/13/2006 03:09 am »
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hop - 12/7/2006  10:14 PM
The other factor is that according to the ESAS study, a single stick SRM is vastly safer than any of the alternatives.  :o

Not if you listen to anyone on this forum.

I'm given to understand that the shuttle SRM's lack of emergency cut-out makes it more dangerous than a liquid engine. Does everyone still agree?

Offline yinzer

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Re: RS-68 CLV First Stage
« Reply #5 on: 07/13/2006 04:16 am »
The lack of graceful emergency thrust termination can give higher LOC numbers with very detailed modeling - it makes aborts much more dynamic events.  The numbers are small enough that it's hard to make any sort of statistical judgement, and the probabilistic risk assessments made to date for the shuttle have all been wildly optimistic.

In any case, according to NASA Watch, MSFC is considering going to the RD-180 for the CaLV core stage.  And as long as they're doing that, they might as well go to a 2 RD-180 core stage for the CLV.  If they call it Atlas Phase 2 there's already a bunch of paperwork and promotional material available.  NASA Watch also says that there's consideration of dumping the CLV for an EELV because the CLV is having trouble lifting the CEV and is costing way more than was expected.
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Offline hop

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RE: RS-68 CLV First Stage
« Reply #6 on: 07/13/2006 04:16 am »
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zinfab - 12/7/2006  7:56 PM
Not if you listen to anyone on this forum.

I'm given to understand that the shuttle SRM's lack of emergency cut-out makes it more dangerous than a liquid engine. Does everyone still agree?
I wasn't commenting on the merits of that claim one way or the other, just pointing out that it is part of NASAs justification for sticking with the stick :)

For a single SRB, not being able to shut down may make the escape system requirements harder to meet, but otherwise doesn't seem like a big deal.  As long as you can get a little ways away from it, range safty can shut it down.  It's a problem for the shuttle because it has two of the things (with any significant imbalance being fatal), and no escape system.

I suspect that the safety argument has some merit. All else being equal, simpler is better...  but the devil is in the details.

Offline bad_astra

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RE: RS-68 CLV First Stage
« Reply #7 on: 07/13/2006 02:35 pm »
Quote
Not if you listen to anyone on this forum.

I'm given to understand that the shuttle SRM's lack of emergency cut-out makes it more dangerous than a liquid engine. Does everyone still agree?

I don't know anyone who watches a Shuttle launch that doesn't breathe a huge sigh of release at SRB sep.
"Contact Light" -Buzz Aldrin

Offline gladiator1332

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Re: RS-68 CLV First Stage
« Reply #8 on: 07/13/2006 02:57 pm »
I like your idea for the CLV, and it reminds me a bit of the Titan-2. I jsut read the NASA Watch post and it does seem there is a distinct possibility we will be hearing about a switch soon. As much as I like the SDLVs it just appears that they will take the whole program down with them.

Since NASA Watch was about the RD-180 and an Atlas Derived CLV, could you run the same numbers on that and maybe make us a render. It would be ncie to see the current CLV, the Delta CLV and the Atlas CLV next to eachother.

And I know what you mean bad astra...watching the launch the other day, the firs thing that came to my mind at SRB sep was "are we really going to launch a crew on one of those things?"

Online edkyle99

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RE: RS-68 CLV First Stage
« Reply #9 on: 07/13/2006 03:17 pm »
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bad_astra - 13/7/2006  9:22 AM

Quote
Not if you listen to anyone on this forum.

I'm given to understand that the shuttle SRM's lack of emergency cut-out makes it more dangerous than a liquid engine. Does everyone still agree?

I don't know anyone who watches a Shuttle launch that doesn't breathe a huge sigh of release at SRB sep.


I don't breath until wheels stop on the runway.  Fair to mention, by the way, that liquid boosters fail more often than solids.  Just look at the recent GSLV failure from India, for one example.  GSLV has a powerful solid booster core with four strap-on liquid boosters.  The solid worked fine.  One of the liquids failed.  

There have been three launch failures this year so far, in 31 attempts.  All of the failures involved liquid propulsion systems.  Last year there were three failures in 55 attempts.  All of the failures were liquids.  Three of the four failures in 2004 were liquids.  The solid rocket failure (Shavit) involved a failed stage separation.  Etc.

 - Ed Kyle

Offline rumble

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Re: RS-68 CLV First Stage
« Reply #10 on: 07/13/2006 03:24 pm »
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yinzer - 12/7/2006  11:03 PM

In any case, according to NASA Watch, MSFC is considering going to the RD-180 for the CaLV core stage.  And as long as they're doing that, they might as well go to a 2 RD-180 core stage for the CLV.  If they call it Atlas Phase 2 there's already a bunch of paperwork and promotional material available.  NASA Watch also says that there's consideration of dumping the CLV for an EELV because the CLV is having trouble lifting the CEV and is costing way more than was expected.

How serious is this "chatter?"  Based on what I understand (which could be incorrect), I would assume a kerosene 1st stage (RD-180) for the core stage would need a beefy second stage.  The current plan for the 2nd stage/EDS doesn't seem to be this.

Could an RD-180 based 1st stage truly be a replacement for the capability of the RS-68 CaLV core stage, or would other vehicle changes be necessary to accompany this?

RD-180 for the 1st stage of the CLV makes good sense to me.

Quote
edkyle99 - 13/7/2006 10:04 AM

Fair to mention, by the way, that liquid boosters fail more often than solids.

...but AFAIK the only failure of a manned launch in the U.S. was due to a solid failure (Challenger).

Offline Jim

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RE: RS-68 CLV First Stage
« Reply #11 on: 07/13/2006 03:41 pm »
Quote
edkyle99 - 13/7/2006  11:04 AM

I don't breath until wheels stop on the runway.  Fair to mention, by the way, that liquid boosters fail more often than solids.  Just look at the recent GSLV failure from India, for one example.  GSLV has a powerful solid booster core with four strap-on liquid boosters.  The solid worked fine.  One of the liquids failed.  

There have been three launch failures this year so far, in 31 attempts.  All of the failures involved liquid propulsion systems.  Last year there were three failures in 55 attempts.  All of the failures were liquids.  Three of the four failures in 2004 were liquids.  The solid rocket failure (Shavit) involved a failed stage separation.  Etc.

 - Ed Kyle

the liquied failures are surivable.  The rest of the world is not a good database.  Spacex and India are not in the same population as the US and Russia wrt spacelaunch

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Re: RS-68 CLV First Stage
« Reply #12 on: 07/13/2006 03:43 pm »
Quote
rumble - 13/7/2006  10:11 AM

Quote
edkyle99 - 13/7/2006 10:04 AM

Fair to mention, by the way, that liquid boosters fail more often than solids.

...but AFAIK the only failure of a manned launch in the U.S. was due to a solid failure (Challenger).


The Challenger failure could have been survivable on a launcher with an escape system.  

The other manned U.S. failure (Columbia) was due to a problem with insulation on the *liquid* propulsion system tank during the launch phase.  No escape system for that one.

 - Ed Kyle

Offline rumble

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Re: RS-68 CLV First Stage
« Reply #13 on: 07/13/2006 04:23 pm »
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edkyle99 - 13/7/2006  10:30 AM

The Challenger failure could have been survivable on a launcher with an escape system.  

Agreed.  Especially if the SRB could have shut down when it started detecting problems.

Quote

The other manned U.S. failure (Columbia) was due to a problem with insulation on the *liquid* propulsion system tank during the launch phase.  No escape system for that one.

 - Ed Kyle

Well...  That's a stretch.  It DOES speak to the danger of putting the re-entry vehicle where falling ice/debris can strike it, so if the crew re-entry vehicle had been above the booster, that wouldn't have happened.


And, as for the Challenger disaster, I think it would have required a launch escape system AND having the crew above the launch vehicle for that to have been survivable.

Offline yinzer

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Re: RS-68 CLV First Stage
« Reply #14 on: 07/13/2006 04:34 pm »
With an escape system, a Challenger-style hardware failure could have been escaped from.  However, the escape system would have to be fairly robust as solids can't be shut down gracefully enough for a system designed around a 3G limit.  The Columbia failure was more or less independent of propulsion mode, and was in fact more related to the total vehicle design.  After all, the foam fell off of the upper stage, and I haven't seen anyone propose an all-solid LV of more than about 5 tons capacity.

Then you start looking at catastrophic failures during first stage flight; the Titan IV that pitched over and blew up (avionics), the Delta III that ran out of stored hydraulic system energy (design/solids), the Delta II that had a solid motor blow up (solids), the X-43 Pegasus (design/structural failure), the first LMLV/Athena (avionics), the Atlas II that got hit by lightning (avionics), the Titan 34D that blew up (solids), the Conestoga that also ran out of stored hydraulic system energy (design/solids), and the SpaceX Falcon (operational/liquid).

Which brings you back to the point that there's no incredible advantage either way, just that you want people and preferably a team who have been around the block with launch vehicle design and operation.  Which is not MSFC.
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Offline Jim

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Re: RS-68 CLV First Stage
« Reply #15 on: 07/13/2006 04:52 pm »
Quote
edkyle99 - 13/7/2006  11:30 AM

Quote
rumble - 13/7/2006  10:11 AM

Quote
edkyle99 - 13/7/2006 10:04 AM

Fair to mention, by the way, that liquid boosters fail more often than solids.

...but AFAIK the only failure of a manned launch in the U.S. was due to a solid failure (Challenger).


The Challenger failure could have been survivable on a launcher with an escape system.  

The other manned U.S. failure (Columbia) was due to a problem with insulation on the *liquid* propulsion system tank during the launch phase.  No escape system for that one.

 - Ed Kyle

Columbia is not a launch failure.  No where near one.  It is a entry failure.  It doesn't matte what caused the damage

Online edkyle99

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RE: RS-68 CLV First Stage
« Reply #16 on: 07/13/2006 05:09 pm »
Quote
Jim - 13/7/2006  10:28 AM

Quote
edkyle99 - 13/7/2006  11:04 AM

I don't breath until wheels stop on the runway.  Fair to mention, by the way, that liquid boosters fail more often than solids.  Just look at the recent GSLV failure from India, for one example.  GSLV has a powerful solid booster core with four strap-on liquid boosters.  The solid worked fine.  One of the liquids failed.  

There have been three launch failures this year so far, in 31 attempts.  All of the failures involved liquid propulsion systems.  Last year there were three failures in 55 attempts.  All of the failures were liquids.  Three of the four failures in 2004 were liquids.  The solid rocket failure (Shavit) involved a failed stage separation.  Etc.

 - Ed Kyle

the liquied failures are surivable.  The rest of the world is not a good database.  Spacex and India are not in the same population as the US and Russia wrt spacelaunch

If we only look at US launch vehicles since 1980 (including all shuttle launches), there have been 605 by my count with 36 launch vehicle failures.  Of these, I can only identify four that were clearly solid rocket motor failures:  STS-51L, Delta 241, Titan 4 K-11, and Titan 34D-9.  I count at least nine that were clearly liquid propulsion system failures:  AC-62, AC-70, AC-71, AC-74, Atlas 19F, Delta 178, Delta 269, Titan 34D-7, and Titan 34D-3.  There may have been others, as a few of the DoD launches are listed cryptically as "failed to orbit" on my list.

 - Ed Kyle

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Re: RS-68 CLV First Stage
« Reply #17 on: 07/13/2006 05:11 pm »
Quote
Jim - 13/7/2006  11:39 AM

Columbia is not a launch failure.  No where near one.  It is a entry failure.  It doesn't matte what caused the damage

The root cause occurred during the launch phase.  Columbia's crew were as good as dead when the bipod ramp hit the wing less than two minutes into the flight.

 - Ed Kyle

Offline Jim

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Re: RS-68 CLV First Stage
« Reply #18 on: 07/13/2006 05:14 pm »
It was a successful launch and the mission was completed as far as a launch vehicle. And that is the official ruling.

Online edkyle99

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Re: RS-68 CLV First Stage
« Reply #19 on: 07/13/2006 05:18 pm »
Quote
rumble - 13/7/2006  11:10 AM

And, as for the Challenger disaster, I think it would have required a launch escape system AND having the crew above the launch vehicle for that to have been survivable.

I've always wondered about that, since the crew module and crew did survive the initial breakup.  The crew may have been alive, if not conscious, right down to impact with the ocean.  I've always wondered what might have happened if they had had pressure suits and parachutes, but a true rocket-propelled escape module would have provided the only real chance.

 - Ed Kyle

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