Author Topic: Ares V limited to only two 5-seg SRBs?  (Read 7348 times)

Offline amaturespacecase

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Ares V limited to only two 5-seg SRBs?
« on: 05/22/2008 07:28 am »
This may have already seen heavy discussion but what is the possibility that Ares V could be augmented with more than just two 5-seg SRBs? I realize that this system is still just on paper but barring clearance issues with the launch tower (and $ problems) it shouldn't be too hard to do this right? Could it be possible we will see Ares V rockets that resemble Delta IIs with several boosters strapped around the first stage? This would assume NASA builds a new supercrawler for this system. No?  :o
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Offline MATTBLAK

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RE: Ares V limited to only two 5-seg SRBs?
« Reply #1 on: 05/22/2008 07:46 am »
With four SRBs, (4 or 5 segment), even the new Crawler Transporter -- the proposed 6-treaded one -- would be unable to bear the load. This would be a monstrously heavy booster, too heavy get to the pad. In the current preliminary studies of Ares V, it is proposed that any augmentation would take the form of 2x Delta IV corestages used as additional strap-ons. Empty until launch day, their increased load would be negligible for the crawlers during rollout.
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Offline amaturespacecase

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RE: Ares V limited to only two 5-seg SRBs?
« Reply #2 on: 05/22/2008 07:54 am »
See that's what I was afraid of. Actually, I was wondering why NASA insists on using these 5-seg SRBs instead of taking more reasonable approaches that EELVs (Delta IVs) have already taken. Do they really save that much money to come at the expense of possible mass to orbit? I just feel like Ares V is being predestined because we are trying so hard to make Ares I work.
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Offline kraisee

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #3 on: 05/22/2008 08:20 pm »
They are an incestuous pairing.   Ares-I is justified only because of Ares-V's greater lift capacity later - and Ares-V is justified only because Ares-I pays for half its technology.   Without one, the other fails to justify itself independently.

Ares-I on its own only manages to replicate the capabilities of an existing EELV, but at $14bn higher cost and at a development time about 4 years longer.

Ares-V on its own would cost twice as much as Ares-I.   It is, after all, a vehicle even more powerful than Saturn-V.   If Ares-I doesn't pay for things like 5-seg and J-2X development for it, then those costs have to be absorbed by Ares-V, making an already-expensive solution into a lot more expensive one.

And Ares-V's LOC/LOM numbers for safety are not meeting ESAS' minimum targets either.


As for the 4x 5-seg option - another limit is the liftoff thrust it would produce is too great for the Pad structure to handle.   IIRC the current limit was assessed to be in the 11m lb thrust range.   Such a beast as suggested would be somewhere over 16m lb thrust - so would require a new Concrete Hardstand to be built.

Other limits which would be breached apparently include the weight on the VAB floor during loading onto the Crawlers as well.

4x 5-seg (or even 4 x 4-seg) would require too many facility modifications to make it worthwhile.

Ross.
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Offline GraphGuy

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #4 on: 05/23/2008 04:41 pm »
Kraisee what do you think of using 2x4 Segment SRBs for Ares V and a Delta IV for the CEV?  What would this do to costs?

Offline kraisee

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #5 on: 05/23/2008 05:34 pm »
It would certainly improve things.

Ares-V's costs would remain about the same (minus SRB development, but now including J-2X development no longer carried by Ares-I) - somewhere in the neighbourhood of $15bn (GAO accounting method, not NASA's).

You could also field Orion much sooner too using some of Ares-I's money to accelerate Orion's development - 2012/13 ish should be doable.


But it still doesn't get you away from the fact that you're still operating two separate launch vehicle systems - which adds a considerable penalty (more than $1bn) to your yearly operating costs.   Not only are you paying for your own Delta launch facilities on top of the Ares-V facilities, but you would also be flying each vehicle only half as many times as a 1-vehicle solution would.   This means that you will not get good economies of scale/amortization effects into either system - unless you can *somehow* afford to fly 20 launches per year (yeah, that's gonna happen!).


More critically, this still doesn't do anything about the Ares-V already being ~13mT below it's performance targets for the mission (the CLV being unable to contribute anything in a "1.5 launch solution" architecture), so you still have to overcome that fairly serious problem, now compounded even further by dropping the SRB performance back to 4-seg levels again.


It's 'better', but is still falling a long way short of hitting the marks accurately IMHO.


A "2-launch solution" architecture, using two 100 ton launchers addresses every one of these issues.   And we are lucky enough to have just such a solution within easy reach with the existing Shuttle stack - if modified into an In-Line configuration launcher ready to take an upper stage (EDS) on top.

With that available, I just don't see the purpose in wasting such vast sums of money on Ares-V, let alone Ares-I as well.   And the savings would certainly allow us to afford to man-rate an EELV as well.   Although it isn't a necessity, it might be a nice backup to have in our pockets.

Ross.
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Offline jml

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #6 on: 05/23/2008 08:08 pm »
The development, manufacturing, and infrastructure costs could be reduced a little more by using an 8.4m core for Ares V, and an 8.4m upper stage that uses the same tank tooling as the core with 2 or more J-2X's. Now we've got something that looks more like a J-234 or J-244 (or even a J-3441 with a third stage) as the Heavy CaLV. And, it might even be able to lift enough for a 1.5 launch architecture to work.

But that still doesn't take care of the biggest issue - two huge sets of recurring annual fixed costs for two separate launch systems.

Offline CFE

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #7 on: 05/23/2008 10:34 pm »
One obstacle to adding more boosters is adding the necessary cross-beam structure in the core stage's intertank.  In the case of adding two Delta IV cores, how would the forward domes attach to the Ares core?  Unless the tankage is stretched, there's no way they could reach the intertank area.
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Offline sbt

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #8 on: 05/26/2008 09:29 am »
IIRC from earlier discussions there are limits to the Pads ability to handle higher thrust vehicles than Ares V. Remember that they were designed for Saturn V and even Apollo didn't gratuitously overdesign stuff for the sake of it.

I believe that Ares V will have to be 'clocked' round at an angle to ensure the thrust from the two boosters goes to different sides of the flame deflector as it is. Any more thrust and major modifications to the Pad, such as opening out additional flame ducts to the sides, would have to be made.

IIRC again there are upper limits even for completely new pads. These are imposed by the acoustic loads on nearby structures and adjacent populated areas. Whilst it may take you quite a few more boosters to do it and you might, with lots of money expended, build Pad C, strengthen various on base structures etc. the upper limit is the fact that you don't want broken windows and claims for hearing damage in Cocoa Beach!

Rick
« Last Edit: 05/26/2008 09:30 am by sbt »
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Offline kraisee

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #9 on: 05/26/2008 08:31 pm »
IIRC from earlier discussions there are limits to the Pads ability to handle higher thrust vehicles than Ares V. Remember that they were designed for Saturn V and even Apollo didn't gratuitously overdesign stuff for the sake of it.

Correct.   The Flame Trench is going to be real close to its limits with the 6-engined Ares-V using 5.5 segment SRB's.   IIRC 11 million pounds thrust was the limit mentioned in previous threads.

I have yet to see numbers for the 5.5 segment boosters, but I'm going to estimate the pair will be about 7.72m lb thrust at liftoff.   With 6 RS-68A's at 688k lb thrust (4.13m lb) you're looking at almost 11.85m lb thrust at liftoff.

This might still *just* be 'possible' without extensive changes, but I sure don't see any room at all for further increases without incurring big additional costs.

Mind you, I have yet to see the Ares program hold back much from "just throwing more money at problems".   It seems to be the only way to achieve upper managements directives so far.


Quote
I believe that Ares V will have to be 'clocked' round at an angle to ensure the thrust from the two boosters goes to different sides of the flame deflector as it is. Any more thrust and major modifications to the Pad, such as opening out additional flame ducts to the sides, would have to be made.

Exactly right.

I've heard that the Ares-V team are already looking at rotating the vehicle by 30 degrees for this very reason.

They have also looked at opening up the catacombes under the Pad to allow flame out the sides - like we saw in the Apollo 13 movie :)


Quote
IIRC again there are upper limits even for completely new pads. These are imposed by the acoustic loads on nearby structures and adjacent populated areas. Whilst it may take you quite a few more boosters to do it and you might, with lots of money expended, build Pad C, strengthen various on base structures etc. the upper limit is the fact that you don't want broken windows and claims for hearing damage in Cocoa Beach!

Another limit on the current Pad structures is that the Fire Bricks in the Trench are over 30 years old and would cost a real fortune (hands-on labor charges mostly) to re-build in a stronger arrangement.   They don't want to add those costs though, because they are already over-budget as it is.

Ross.
« Last Edit: 05/26/2008 08:43 pm by kraisee »
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Offline kraisee

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #10 on: 05/26/2008 08:49 pm »
One obstacle to adding more boosters is adding the necessary cross-beam structure in the core stage's intertank.  In the case of adding two Delta IV cores, how would the forward domes attach to the Ares core?  Unless the tankage is stretched, there's no way they could reach the intertank area.

I saw some imagery a little while back, and it looks like they would just attach Delta-IV Cores to the tanking area directly.

The Delta-IV Cores don't have the same Thrust Oscillation issues as the SRBs do, so a brace between the mountings isn't required.   Also, the pressurized Tanking is able to handle quite a bit of side-load anyway (with a few suitable modifications) - think about the Aft Orbiter mounts on Shuttle today.

Still, it drops the LOM to below that of Shuttle - so the whole concept of 3rd and 4th strap-on boosters for Ares-V is not a good one.   They would have to be *really* desperate to seriously do that to this turkey IMHO.

Ross.
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Offline Jim

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #11 on: 05/26/2008 09:12 pm »
I saw some imagery a little while back, and it looks like they would just attach Delta-IV Cores to the tanking area directly.

The Delta-IV Cores don't have the same Thrust Oscillation issues as the SRBs do, so a brace between the mountings isn't required.   Also, the pressurized Tanking is able to handle quite a bit of side-load anyway (with a few suitable modifications) - think about the Aft Orbiter mounts on Shuttle today.

Ross.

The shuttle is the only vehicle where the strap ons apply their thrust loads at the forward attachment.  Most vehicles with strap ons apply their loads at the aft attachment since this is the thrust section.  List of vehicles with standard (aft) thrust loading are:
All Delta/Thor variants, Atlas IIAS, Atlas V XXX, Atlas V Heavy, Delta IV Heavy, Delta IV M+, Titan III, Titan IV,
« Last Edit: 05/26/2008 09:12 pm by Jim »

Offline kraisee

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #12 on: 05/27/2008 02:41 am »
Off topic, but where is the dynamic load from the SRB's provided to the core of the Ariane-V?   Is it the Fwd or Aft attachment?

Ross.
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Online edkyle99

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #13 on: 05/28/2008 03:08 pm »
Off topic, but where is the dynamic load from the SRB's provided to the core of the Ariane-V?   Is it the Fwd or Aft attachment?

Ross.

As I understand it, primary thrust loads are transmitted from the EAP to the EPC through an attachment on the EAP front skirt (nose fairing section).  Here are some descriptions:

http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1996ESASP.386..453B&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1996ESASP.386..463B&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf

The first paper is especially interesting since it describes Ariane 5's novel design for handling acoustic oscillation modes in the EAP boosters. 

 - Ed Kyle
« Last Edit: 05/28/2008 03:44 pm by edkyle99 »

Offline kraisee

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #14 on: 05/29/2008 06:11 am »
Thanks for those Ed.   Very interesting read, both of them.
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Offline kevin-rf

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Re: Ares V limited to only two 5-seg SRBs?
« Reply #15 on: 06/02/2008 01:50 pm »
Not to resurect this thread, but the shuttle knocked a bunch of bricks loose over the weekend. What is a 5 segment going to do to the pads, much less four five segments?

SpaceflightNow's article with pictures :
http://spaceflightnow.com/shuttle/sts124/080601pad/

 
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