Author Topic: SDLV - Only two SRBs? Why not more?  (Read 5805 times)

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SDLV - Only two SRBs? Why not more?
« on: 03/12/2007 11:04 pm »
Ares V insists on additional segments on the two SRB's (ASRM's). How come three or four of the existing shuttle ASRM's never show up in Shuttle-derived LV's? Cost of recovery/reuse too high given more to recover? Or is it reliability suffers due to complexity? Or cost of modifications to launch pad systems / thrust diverters /etc?

Offline Jim

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RE: SDLV - Only two SRBs? Why not more?
« Reply #1 on: 03/13/2007 02:02 am »
The existing ET attachment system is not applicable and would need redesign

new MLP's, crawlers and pads would be required.

VAB might needs some major mods

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Re: SDLV - Only two SRBs? Why not more?
« Reply #2 on: 03/13/2007 03:36 am »
Thanks

Offline CFE

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Re: SDLV - Only two SRBs? Why not more?
« Reply #3 on: 03/13/2007 04:50 am »
Then again, the current Ares V design requires new crawlers and MLP's.  Why not build in the option for four or six SRB's while we have the chance?
"Black Zones" never stopped NASA from flying the shuttle.

Offline Jim

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Re: SDLV - Only two SRBs? Why not more?
« Reply #4 on: 03/13/2007 11:50 am »
Quote
CFE - 13/3/2007  2:50 AM

Then again, the current Ares V design requires new crawlers and MLP's.  Why not build in the option for four or six SRB's while we have the chance?

Ares V doesn't require new crawlers.  The crawlers just new to be replaced.  I believe Ares I gets the new MLP's and Ares V reuses the old one

The pads can't handle 4 or 6 SRB's that is the real issue.  

Also there is no requirement for 4 or 6 SRB vehicles



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Re: SDLV - Only two SRBs? Why not more?
« Reply #5 on: 03/13/2007 03:23 pm »
Couldn't one obviate the need for the development of Ares additional segment versions with 3 existing SRB's? Wouldn't that bring in the schedule and lower budget?

Offline Tergenev

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Re: SDLV - Only two SRBs? Why not more?
« Reply #6 on: 03/13/2007 03:35 pm »
Actually, I would think that adding a segment to the SRB's is probably about the most inexpensive way to lift additional mass to orbit. It requires very little to no modification to most infrastructure, including test facilities. Probably most importantly, adding additional SRBs would significantly change the physics of things like immediate post-launch roll-maneuvers. These things are well understood with two boosters. I know they do multiple SRBs, including air started SRBs, on the Delta 4s, but those aren't human rated systems, and they are significantly less massive systems. I would think that adding additional large (shuttle sized) SRBs to the Ares V would require huge new engineering efforts to understand the loads and stresses involved all through the launch stack.

So, bottom line, the more you change the basic geometry of the launch stack, the more expensive the development will likely be.  At least, that's how I interpret the situation. However, I am not a rocket scientist, as are a few people around these forums.

Offline Jim

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Re: SDLV - Only two SRBs? Why not more?
« Reply #7 on: 03/13/2007 10:15 pm »
Quote
nobodyofconsequence - 13/3/2007  1:23 PM

Couldn't one obviate the need for the development of Ares additional segment versions with 3 existing SRB's? Wouldn't that bring in the schedule and lower budget?

3 would be worse than 4.   Pad, MLP, and VAB mods. 3 SRB attachment would be iffy

Offline Scotty

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Re: SDLV - Only two SRBs? Why not more?
« Reply #8 on: 03/14/2007 01:48 am »
The limiting factor are the launch pads, as they were designed with about 9 to 10 million pounds of lift off thrust maximum.
Ares V as it is planned right now, will be pushing past that limit by a couple million pounds of thrust.

As it is planed today, Ares V will use the existing MLP's, very much modified; and two totally new transporters.

Ares I will get the new ML; and will use the existing transporters with little modification.

So to fly four or six SRB's on a Super Ares V, or the Super Big Jupiter that has been proposed, you would need:
1) new launch pads at a minimum of a couple Billion bucks each.
2) new Super ML's at a minimum of 200 Million each.
3) New Super transporters at a minimum of 100 Million each.

Anyone got five billion extra bucks under your bed, that you can afford to donate to NASA?

That does NOT include modifications to the VAB, new crawler pathways, KSC infrastruction improvements, a couple new booster recovery ships, another booster processing facility, and of course the flight vehicle itself!
I figure you could do the whole job for around 20 to 25 billion bucks.

Wait a minute, how much will we spend in Iraqi this year alone?
Just what is 25 Billion to a one Trillion plus Dollar National Budget?
The answer is nothing at all!

It just makes me sick; as we piss money all over the place, and then give NASA and the Space Program the table scraps.

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Re: SDLV - Only two SRBs? Why not more?
« Reply #9 on: 03/15/2007 02:32 am »
Ironically, recent years have proven how little budget discipline matters, and how much congressional district earmarks do matter. It will be hard to return to more sensible budget practices, or know when that will be politically feasible. My guess is that money for development and qualification of new flight hardware will be harder than that  for re-purposing existing flight hardware. So using more of what you already have is easier than improvements.

Offline publiusr

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Re: SDLV - Only two SRBs? Why not more?
« Reply #10 on: 05/21/2007 10:35 pm »
Quote
Jim - 13/3/2007  6:15 PM

Quote
nobodyofconsequence - 13/3/2007  1:23 PM

Couldn't one obviate the need for the development of Ares additional segment versions with 3 existing SRB's? Wouldn't that bring in the schedule and lower budget?

3 would be worse than 4.   Pad, MLP, and VAB mods. 3 SRB attachment would be iffy

True, a four SRB iteration would look like the pair of twin Zenit-strap-ons....2X2

Offline aftercolumbia

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Re: SDLV - Only two SRBs? Why not more?
« Reply #11 on: 05/28/2007 09:17 pm »
Quote
Jim - 13/3/2007  6:50 AM

Quote
CFE - 13/3/2007  2:50 AM

Then again, the current Ares V design requires new crawlers and MLP's.  Why not build in the option for four or six SRB's while we have the chance?

Ares V doesn't require new crawlers.  The crawlers just new to be replaced.  I believe Ares I gets the new MLP's and Ares V reuses the old one

The pads can't handle 4 or 6 SRB's that is the real issue.  

Also there is no requirement for 4 or 6 SRB vehicles

Ares I uses modified MLPs, Ares V uses new MLPs.

Offline aftercolumbia

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Re: SDLV - Only two SRBs? Why not more?
« Reply #12 on: 05/28/2007 09:25 pm »
Quote
Jim - 13/3/2007  5:15 PM

Quote
nobodyofconsequence - 13/3/2007  1:23 PM

Couldn't one obviate the need for the development of Ares additional segment versions with 3 existing SRB's? Wouldn't that bring in the schedule and lower budget?

3 would be worse than 4.   Pad, MLP, and VAB mods. 3 SRB attachment would be iffy

I very much doubt that.  The arrangement of the existing Shuttle stack is not too far removed from a 3*SRB plus inline core, actually: 2*3 million pound thrust SRBs on each side of the ET, and a 1.35 million pound thrust Orbiter orthogonal to the SRBs' situation.

What could be a bit more of a boon to the 3 SRB edition of the Ares V is to size up the Ares V core diameter to the point where two boosters, placed 120deg apart, are the same distance apart as the two boosters on the Shuttle stack that we have.  That way the same SRB flame trench could be used for those two.  Alas, the SSME flame trench would have to be overhauled to handle the fourfold increase in thrust going through that side of the pad.  Since the Ares V already has similar issues, I don't see that we are losing much.

Offline simonbp

Re: SDLV - Only two SRBs? Why not more?
« Reply #13 on: 05/29/2007 01:36 am »
Also, just to note because I didn't see it mentioned, the SRBs are connected (on both STS and Ares V) via a beam in the interstage. Adding boosters would require a new crosspiece inside; this isn't impossible, but it makes it that much harder to add two extra RSRMVs to the Ares V...

Simon ;)

Offline Jim

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Re: SDLV - Only two SRBs? Why not more?
« Reply #14 on: 05/29/2007 02:02 am »
Quote
aftercolumbia - 28/5/2007  5:25 PM

Quote
Jim - 13/3/2007  5:15 PM


3 would be worse than 4.   Pad, MLP, and VAB mods. 3 SRB attachment would be iffy

I very much doubt that.  The arrangement of the existing Shuttle stack is not too far removed from a 3*SRB plus inline core, actually: 2*3 million pound thrust SRBs on each side of the ET, and a 1.35 million pound thrust Orbiter orthogonal to the SRBs' situation.

What could be a bit more of a boon to the 3 SRB edition of the Ares V is to size up the Ares V core diameter to the point where two boosters, placed 120deg apart, are the same distance apart as the two boosters on the Shuttle stack that we have.  That way the same SRB flame trench could be used for those two.  Alas, the SSME flame trench would have to be overhauled to handle the fourfold increase in thrust going through that side of the pad.  Since the Ares V already has similar issues, I don't see that we are losing much.

"
I very much doubt that"  Really?  Based on what experience?

The holes in the MLP have nothing to do with it.  The orbiter hole wasn't designed to support an SRB.
 
Also the orbiter hole is further away from the ET.

Stacking ops in the VAB are affected, as well as platforms

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