Comments on: Last week’s news

By: Dfens

Dfens — Mon, 05 Sep 2005 21:16:17 +0000

It was a Titan IVA with the 7 segment CSD solid. It seems they decided it was a case burn through, so the number of segments really wasn’t an issue. None the less, they went to a 3 segment composite case with the B model. Wasn’t that the one that got to about 90 degrees of yaw before the range safety officer hit the button? It was 100 seconds into the launch, so it must have been going pretty fast, and probably didn’t need any help. It’s amazing how many unmanned vehicles have failed just in the ’90s. There were at least 3 Titan missions that failed, one due to the IUS upper stage. Not an IUS I worked on. Mine all worked very well, thank you very much, which got me into lots of trouble with the program manager. It got me into lots of trouble with those Aerospace Corp. weenies too. Every time I’d find something the USAF would call them on the carpet for not finding it first. Then they’d start stabbing me in the back. Too bad they couldn’t take up the slack after I left.

By: Paul Dietz

Paul Dietz — Mon, 05 Sep 2005 15:33:57 +0000

If I remember correctly either a 34 or IV flight had to be terminated because of a joint failure.

‘Had to be terminated’ in the sense of ‘had to watch all the pretty burning fragments crash to the ground after it catastrophically spontaneously disassembled.’

By: Dfens

Dfens — Mon, 05 Sep 2005 15:05:32 +0000

No, Donald, the redesign of the shuttle SRBs was limited to a redesign of the joints, which is the part that failed on Challenger. CSD makes (made?) some 7 segment solids for Titan IV. If I remember correctly either a 34 or IV flight had to be terminated because of a joint failure. I seem to recall at least one friend and a paper perhaps citing this as a reason fewer joints are better.

I would think the advantage of the SRB approach would be not having to deal with cryo-fuels. It would seem to me, if the first stage was solid, the thing to do would be to make them all solid.

By: Cecil Trotter

Cecil Trotter — Sat, 03 Sep 2005 13:20:07 +0000

“Why not use the existing 4 segment SRB as the CLV and eliminate some of the risk?”

Simple, a 4-segment SRB doesn’t have the lift capacity NASA has determined it will need.

By: clcops

clcops — Sat, 03 Sep 2005 11:21:21 +0000

Why not use the existing 4 segment SRB as the CLV and eliminate some of the risk?

By: Donald F. Robertson

Donald F. Robertson — Fri, 02 Sep 2005 21:17:33 +0000

I thought we’d started out with more segments and reduced them in the post-Challenger redesign, but maybe my memory is wrong.

Haven’t we been launching heavy nuclear weapons on top of heavy second stages on top of first stage SRBs for decades? It seems to me that the loads from a liquid second stage plus CEV would be differrent in magnitude but less so in degree.

Am I wrong?

— Donald

By: Cecil Trotter

Cecil Trotter — Fri, 02 Sep 2005 20:08:26 +0000

I understand what Mr. Walkers concerns were and also that, as you state, the SRB structural loading is a bit more simple as compared to a liquid fueled vehicle. I was simply wondering if the 5-segment SRB was a completely paper idea or if any hardware had been built. Since my post above I’ve found a few “references” to a 5-segment test firing by Thiokol, but nothing really definitive.

By: Dfens

Dfens — Fri, 02 Sep 2005 19:56:52 +0000

Even if they had fired one, the point Mr. Walker was making is the load path is completely different, and he is correct. On the other hand, a solid, unlike a liquid booster, is pressurized along it’s entire length, with part of the thrust coming from the top bulkhead. I don’t know about them having tested one. I haven’t been following closely enough to know.

By: Cecil Trotter

Cecil Trotter — Fri, 02 Sep 2005 19:41:34 +0000

Dfens: “I wish I had a little more confidence there was some actual analysis behind that 5 segment booster concept.”

Have they not actually test fired a 5 segment SRB, or just an “advanced” 4-segment SRB?

By: Dfens

Dfens — Fri, 02 Sep 2005 19:29:11 +0000

Good Mexican food always puts me in a better frame of mind, or it may have been a post hypnotic suggestion. I’m not sure any more. My bias is against NASA these days, but I’m trying to give them a fair shake. I wish I had a little more confidence there was some actual analysis behind that 5 segment booster concept.