Author Topic: Titan SRB's and lessons for the Ares SRB's  (Read 5845 times)

Offline CFE

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Titan SRB's and lessons for the Ares SRB's
« on: 10/11/2007 05:59 AM »
During the history of the Titan program, there have been four different SRB designs: the UA1205, UA1206, UA1207, and USRM.  The boosters were stretched twice, then redesigned to reduce the number of field joints.

I was wondering if there are any lessons from the Titan SRB development that can be applied to the current process of redesigning the Shuttle SRB into the Ares SRB.  The figure of $3bil has been tossed around for Ares SRB development, and I was wondering if the development efforts for any of the Titan SRB's fell into the same ballpark (adjusting for inflation, of course.)  The development of UA1206 and UA1207 undoubtedly required major changes to the propellant grain.  I suspect that USRM's propellant segments looked a lot like longer versions of those used on UA1207, but mechanically the booster was very different.
"Black Zones" never stopped NASA from flying the shuttle.

Offline Jim

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #1 on: 10/11/2007 11:00 AM »
The SRMU was wider and had different propellant from a 1207 SRM.  Actually, the information flowed from shuttle to titan

Offline CFE

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #2 on: 10/13/2007 07:15 AM »
Any idea for how much it cost to develop each new version of the Titan SRB's?
"Black Zones" never stopped NASA from flying the shuttle.

Offline tnphysics

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #3 on: 10/13/2007 11:43 AM »
Could 2 SRMUs replace each 5 segment RSRB?

Offline Jim

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #4 on: 10/13/2007 12:13 PM »
Quote
tnphysics - 13/10/2007  7:43 AM

Could 2 SRMUs replace each 5 segment RSRB?

no, it was "smaller"

Offline clongton

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #5 on: 10/13/2007 01:05 PM »
Both the Titan and Shuttle SRB’s suffer from the same unpleasant condition which is similar to the “pogo” effect documented at the beginning of the Saturn program. On both launch vehicles however, the severe effects of this condition were reasonably well mitigated by how they were attached to the core booster. In the case of STS, the cross beam connecting port and starboard SRBs acts, not only as a structural member to transfer the forward thrust to the LOX tank, but also as a sort of “spring” which absorbs these forces and prevents them from being transmitted into the rest of the vehicle airframe. On the STS SRBs, this “pogo” effect allows the inner and outer sides of the booster (close to the ET and furthest away from the ET) to flex as much as plus or minus a full quarter of an inch, and to do so completely independently of each other. It sets up a resonance that could be perfectly capable, if unmitigated, of destroying the launch vehicle. You can imagine what kind of stress this flexing puts on the main airframe. Now, take the main airframe away and fly the SRB by itself, aka Ares-I, and there is nothing there to mitigate this effect. So in the case of the Ares, it gets transmitted in its entirety into the rest of the airframe, specifically into the upper stage and the Orion spacecraft. My question is: how is this dangerous bending and twisting “pogo” effect to be mitigated for the Ares to prevent the launch vehicle itself from destroying the stage and spacecraft that are mounted above it?

BTW, this effect is inherent in all solids, from the STS SRB all the way down to the Estes model rocket engines. It’s a product of the fuel grain and core design. It’s the nature of the beast but only becomes dangerous on big solids, like the SRB. Mounted in pairs with a structural flex member like the horizontal beam that connects them on Shuttle, it is mitigated. But flying alone, without mitigation? This was a VERY big deal to the STS designers, and for a while they were not sure they could make it safe enough for a man-rated launch vehicle. The structural configuration of Shuttle was their answer, which worked very well. But now, with Ares-I, that solution is no longer possible. So what’s the new solution?

Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline hmh33

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #6 on: 10/14/2007 02:36 AM »
Could you explain in more detail (or link to an explanation of) what causes this "pogo-like" effect in solids?

Thanks!
Henry

Offline Lee Jay

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #7 on: 10/14/2007 04:17 AM »
Quote
hmh33 - 13/10/2007  8:36 PM

Could you explain in more detail (or link to an explanation of) what causes this "pogo-like" effect in solids?

The rate of propellant burn in a solid is dependent on pressure (among other things).  The pressure is dependent on propellant burn rate (feedback loop).  If these become resonant (blow over a bottle top...the sound is the air resonating in the chamber), you get rapidly changing thrust at the resonant frequency.

Happens in liquids too, for similar reasons (chamber pressure - tank/pump pressure).

Generally it's considered bad form to have huge stuff operating at resonance.  To put it another way, you have to design carefully to avoid, damp, or tolerate a resonant condition when the resonance is potentially a source of failure or fatigue.

Offline CFE

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #8 on: 10/14/2007 05:00 AM »
Pogo was a considerable problem on the Saturn V (Apollo 6 & 13,) and would have needed to be addressed if there was any production of the Saturn V beyond the initial 15 examples.  The SSME engineers did learn their lessons from the J-2, though, and designed pogo suppression into the SSME from the start.  I would assume that J-2X will also have pogo suppression.
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Offline AntiKev

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #9 on: 10/14/2007 08:16 AM »
But it's not the second stage that has the issue (J-2), it's the first stage (SRB).  They could design some sort of pogo suppression (dampers?) into the interstage.

Offline clongton

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #10 on: 10/14/2007 01:26 PM »
Quote
AntiKev - 14/10/2007  4:16 AM

But it's not the second stage that has the issue (J-2), it's the first stage (SRB).  They could design some sort of pogo suppression (dampers?) into the interstage.
The 2nd stage certainly will suffer the consequences of this resonance. Unless it is suppressed or mitigated, this feature of the 1st stage could potentially damage both the 2nd stage and the spacecraft above it, bringing about a LOM and potentially, if it damaged the abort sequencers, a LOC.

Any suppression of this effect can only be built into the interstage, and if successful, will protect the 2nd stage and the spacecraft, but this will not do anything toward mitigating what this resonance is able to do to the 1st stage itself.

On STS, the structural flex member in the ET below the LOX tank not only suppressed the effect, it also absorbed it so that the solid SRBs were protected from themselves. The two SRBs fed the resonance into the member from opposite sides and they tended to cancel each other out to some degree, leaving the flex connections to handle the rest. This resulted in less flexing in the segments, lowering the damage potential. It was pretty ingenious when you think about it. Function in simplicity. It’s a perfect example of structural engineering at its best. On the Ares-1, this protection is not there so the resonance could still potentially damage or destroy the first stage itself, mid flight.

I have yet to see this addressed in any detail from anyone. Does anyone on here have any idea how the design engineers are handling this?

Lee Jay’s example of blowing over the top of a bottle and hearing the sound of the resonance in the chamber is perfect. The unique sound of a Shuttle launch is EXACTLY that. The vast majority of the sound you hear as STS climbs toward orbit is not the sound of the SSMEs, it’s the resonance in the chambers of the 2 SRBs, at ~11.5 hertz. You will never watch and listen to a Shuttle launch in the same way again.  :)
Chuck - DIRECT co-founder
I started my career on the Saturn-V F-1A engine

Offline AntiKev

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #11 on: 10/14/2007 08:24 PM »
Chuck, I was referring to CFE's comment about the J-2X's pogo suppression.  I realize what the consequences of the 11.5Hz vibration are, see my replies in the Ares I thread.

Offline CFE

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #12 on: 10/14/2007 09:01 PM »
As much as people are focusing on the solid 1st stage pogo problem, the second stage (after J-2X ignition) will need to be addressed as well.
"Black Zones" never stopped NASA from flying the shuttle.

Offline tnphysics

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #13 on: 10/17/2007 12:28 AM »
I hope that this problem is either solved or leads to a CLV change and that nobody is posting "Launch failure" after the Ares-1-X launch.

Offline tnphysics

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Re: Titan SRB's and lessons for the Ares SRB's
« Reply #14 on: 10/17/2007 12:29 AM »

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