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  Filament-wound case shuttle solid rocket motors

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Author Topic:   Filament-wound case shuttle solid rocket motors
Sky dancer
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From: United Kingdom
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posted 04-03-2014 11:01 AM     Click Here to See the Profile for Sky dancer   Click Here to Email Sky dancer     Edit/Delete Message   Reply w/Quote
This is my first post on the forum, so I hope you'll forgive any mistakes!

I'm interested in a slightly different shuttle modelling project, namely a full stack but with filament wound case solid rocket motors (FWC-SRM) instead of the conventional SRMs.

The only close up photos I have of a FWC-SRM are a couple of press photo's from Thiokol showing DM-6 prior to and during it's test firing on 25th October 1984. The blurb on the back states that after two more test firings, two of these FWC-SRMs were going to be used by Discovery on her launch from Vandenberg in October 1985. Unfortunately, the "Challenger" tragedy occurred...

Two of the FWC-SRMs were later fitted to "Pathfinder" at Huntsville, before being painted white to resemble a more typical configuration.

From a modelling point of view, there are two options:

  1. A full stack of "Pathfinder" as she was first displayed
  2. A full stack of "Discovery" as she would have looked like on her first, but never to happen, launch from Vandenberg.
Pathfinder's FWC-SRMs appear to have different markings from the DM-6 test article, so were these the flight-ready versions destined for "Discovery"?

So my main question is this - does anyone have any photos, (close-up, detailed, distant or otherwise) of the FWC-SRMs fitted to Pathfinder before they were re-painted? There's a photo posted on a different thread in the forum, but I would be particularly interested in the SRM fitted to the port side as the only photos I've been able to get off the web show the starboard booster.

I'm afraid I live in the United Kingdom; info is bit bit hard to get over here and a trip to Huntsville is a pipe dream at the minute; but maybe one day. Hope you can help. — Michael

X-Plane Fan
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posted 04-03-2014 11:17 AM     Click Here to See the Profile for X-Plane Fan     Edit/Delete Message   Reply w/Quote
I asked our resident shuttle expert, Dennis Jenkins, about this and basically he said that if the FWC SRBs would have been used on an operational flight, they would have looked virtually the same as a standard booster and would have been painted white. There were no significant external differences between the two.

Since your plan is to build a 'what-if' model anyways, you can paint it any way you would like.

Robert Pearlman
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posted 04-03-2014 11:28 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Not that I would ever doubt Dennis, but it seems odd that they would paint the SRBs, as the point of the filament-wound casing was to deliver the reduced weight needed to launch heavy payloads from Vandenberg into polar orbit (or so is my understanding).

Ronpur
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posted 04-05-2014 08:50 AM     Click Here to See the Profile for Ronpur   Click Here to Email Ronpur     Edit/Delete Message   Reply w/Quote
I have read some place, but can't find it now, that they were to fly unpainted. But, I have also read they were to be painted. So, it seems like we may never know which way it was to be.

The only photos I have seen have them as unpainted and that was how I build my model of them back in 1986. I wish I still had it...

I went with black, otherwise, you can't tell the difference.

Sky dancer
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posted 04-05-2014 01:16 PM     Click Here to See the Profile for Sky dancer   Click Here to Email Sky dancer     Edit/Delete Message   Reply w/Quote
Thanks for your kind replies; sorry for the delay in getting back to you, I'm afraid work insists in getting in the way.

These photos show Pathfinder with the FWC-SRM's pre-painting, while the second is a press photo from Thiokol showing DM-6 before its first test firing:

X-Plane Fan and Robert: I have massive respect for Dennis Jenkins; he is the author of my two favourite shuttle books. Both your point of views are valid.

The photos show that DM-6 had a filament wound portion of the rear segment of the booster completely painted white.

The photo of Pathfinder (courtesy of "Hotdog" from the ARC and Hab1 forums — thank you so much!) is interesting in that the SRM shown has completely different markings in the area where the systems tunnel would be. It is this feature that makes me wonder if these were flight ready times for Discovery.

It is not terribly obvious in the photo of Pathfinder, but there appears to be slightly different markings on the mostly invisible left hand booster. There is an orange portion above the rear skirt that is not present on the right hand booster, while the rear skirt itself appears to be off-white or light grey.

I initially thought this was due to shadow, but "Hotdog" also provided a B&W image from a newspaper were the colour difference is more noticeable. Page 68 of Dennis Jenkins' Aerofax Datagraph on the shuttle also shows the difference — although this could also be shadow effect.

The Aerofax Datafile has two pictures of the FWC-SRM's on pages 67 and 68. These are fascinating, as although they are very small they show the contrast between different areas of filament, resulting in different shades/tones of grey/black rather than a uniform colour.

As for the nozzles themselves — why are they dark orange? Is this red oxide primer prior to re-paint? Dennis Jenkins states the nose segments and aft skirts were engineering and structural test items — is this why?

Does anyone have a way to contact Mr. Jenkins to clarify, or would he be willing to email colour versions of his photos to me?

Ronpur - glad to hear you had done this build in the past. "Hotdog" is doing a 1:144 model of Pathfinder, while I'm seriously considering a 1:72 version.

Any help with photos, guidance etc. would be greatly appreciated by both "Hotdog" and myself.

Jay Chladek
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From: Bellevue, NE, USA
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posted 04-06-2014 01:22 AM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Robert Pearlman:
...the point of the filament-wound casing was to deliver the reduced weight needed to launch heavy payloads from Vandenberg into polar orbit
I can think of a few practical reasons for painting them and one is more likely to see something painted than not. Corrosion control would be a prime reason (even if not for the cases themselves, at least for any metal fittings used, given the boosters are designed for water impact and recovery). Thermal control might perhaps be another issue, even though SRBs don't have cryogenic tanking like a liquid rocket stage might. Then there is also the practicality of a white object showing up A LOT more easily in the water than a darker one as these boosters were designed for recovery and reuse, just like the normal ones used for KSC launches.

Given the surface area of the casings, I don't think that much weight would be added if they were painted. Even though most everyone mentions the 550 lbs. weight savings from the ET shedding its white paint after STS-1 and 2, the main reason why the paint was there in the first place as there was a concern that UV light exposure on the ET tank foam would make it more brittle as it darkened. Turns out the foam didn't become more brittle at all, so the paint was left off more as a cost and time savings. The weight savings just happend to be more of a side benefit as refinements to ET manufacturing lead to much greater weight savings over the life of the shuttle program.

Aeropix
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posted 04-06-2014 03:00 AM     Click Here to See the Profile for Aeropix   Click Here to Email Aeropix     Edit/Delete Message   Reply w/Quote
How much weight was saved with the filament wound method? I wonder if this technology was pursued how much more cargo could have been uplifted to the ISS over the life of the shuttle program. It seems like an opportunity lost, that these were never introduced, as it would have furthered our understanding of new technology through data gathering on flights from KSC.

Sky dancer
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posted 04-06-2014 07:44 AM     Click Here to See the Profile for Sky dancer   Click Here to Email Sky dancer     Edit/Delete Message   Reply w/Quote
Again, thanks for your replies!

In Aerofax Datagraph on the shuttle, Dennis Jenkins states that a FWC-SRM weighted a massive 28,000 lbs less than a steel SRM, however I have also heard quoted that this only translated to an increase in the orbiter's payload of 5000-6000 lbs.

Based on the ET, I'm sure that painting the FWC-SRM's would only have added a few hundred pounds of weight — but I don't know what impact that would have had on payload.

There appears to have been six FWC-SRM made, FWC-1, 2 and 3, DM-6, DM-7 and QM-5. Again, according to Dennis Jenkins, none of these are painted, they were left in their natural state.

Any photos?

Headshot
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posted 04-06-2014 08:33 AM     Click Here to See the Profile for Headshot   Click Here to Email Headshot     Edit/Delete Message   Reply w/Quote
A similar picture to the second one posted by Sky Dancer appeared in an issue of AWST. The caption indicated that the large white segment to the left of the nozzle was steel to provide more strength for the shuttle's external tank attach point.

Sky dancer
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posted 04-06-2014 09:23 AM     Click Here to See the Profile for Sky dancer   Click Here to Email Sky dancer     Edit/Delete Message   Reply w/Quote
Thanks for that info. Would this be the photo from AW&ST?

Headshot
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posted 04-06-2014 10:34 AM     Click Here to See the Profile for Headshot   Click Here to Email Headshot     Edit/Delete Message   Reply w/Quote
Nice picture!

The AWST image looks like it was taken at the same time, but from a different angle.

I also sent you a private message.

Sky dancer
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posted 04-06-2014 05:46 PM     Click Here to See the Profile for Sky dancer   Click Here to Email Sky dancer     Edit/Delete Message   Reply w/Quote
Bill, got your PM okay; thanks very much. The photo from AW&ST is the same as the one I posted earlier in the thread.

What's very interesting about your scan is the caption:

  1. It explains the white-painted segment on the booster
  2. The complete change in attitude re. the captions used for the same photo; the original press blurb on my photo (dated 26 Oct. 1984) is to the effect "this is going to be used on Discovery in October 1985." The AW&ST caption (March 1986; post-Challenger) is to the effect "this is never going to be used due to safety concerns."
Here's the reverse of my photos:

hotdog
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From: Chattanooga, TN
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posted 04-07-2014 10:26 PM     Click Here to See the Profile for hotdog   Click Here to Email hotdog     Edit/Delete Message   Reply w/Quote
Michael, glad to see you have been able to find out more on the FWC-SRM's. My attempts to find out more information have fell short.

I think I can answer more on your question about the Pathfinder:

quote:
Originally posted by Sky dancer:
There appears to be slightly different markings on the mostly invisible left hand booster. There is an orange portion above the rear skirt that is not present on the right hand booster, while the rear skirt itself appears to be off-white or light grey.
The aft skirt on the starboard side is real, but the skirt on the port side is a mockup. It's a fairly decent copy that 99% of people visiting the museum don't ever notice. But a close inspection of the stack in person, you can see differences in the details. When I go back down there in a few weeks, I plan to get some close-up detail shots from a modeler's perspective that will help us with our builds.

I'm not sure about the burnt orange "primer" on the nozzles, but I would guess that's the condition the segment was in while it was stored at Marshall in the 1980s before it was selected to be used on the Pathfinder. The manufactured mockup nozzle was probably painted the same color to match the real one they were basing it off of, before both boosters got the completely white paint job after the stack was fully assembled. Pure speculation on that though!

Keep up the good work. A 1:72 Pathfinder stack - that should be impressive!

Headshot
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posted 04-08-2014 06:48 AM     Click Here to See the Profile for Headshot   Click Here to Email Headshot     Edit/Delete Message   Reply w/Quote
Michael, I hope you will post some images, on cS, of your model upon completion. I would certainly like to see it.

Jim Behling
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posted 04-08-2014 07:35 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Aeropix:
I wonder if this technology was pursued how much more cargo could have been uplifted to the ISS over the life of the shuttle program.
The Advanced Solid Rocket Motor (ASRM) would have superseded the performance gain from filament wound cases (FWC). ASRM was designed with ISS in mind. ASRM was superseded by the Super Lightweight Tank (SLWT) which used Li Al. The ISS got all the necessary performance it needed from the STS through the SLWT.

Sky dancer
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posted 04-09-2014 06:42 AM     Click Here to See the Profile for Sky dancer   Click Here to Email Sky dancer     Edit/Delete Message   Reply w/Quote
Good to hear from you again! Yes, the research continues — I think its half the fun. But maybe I'm just weird.

I've decided to do Pathfinder rather than Discovery, just to be completely different. It seems a bit strange that while all the members on ARC are trying to make their orbiters as accurate as they possibly can, I will be modifying mine to look LESS accurate! I believe Pathfinder is 3 feet shorter than a proper orbiter; I've also heard (unconfirmed) that the FWC-SRMs were slightly longer than the metal SRMs!

If your going to Huntsville and taking photos I would really appreciate hi-res copies, if you wouldn't mind? Obviously the FWC-SRMs would feature high up in my wish list, but also the fin area too — although I have read (again unconfirmed) that the current fin may not have been the one it was initially displayed with.

Just while I'm on here, a quick query about the other photo you took — I hope you don't mind me posting it here.

It just concerns the tip of the nose cone; any recollection of the colouring of this? Radome tan, or a variant of this?

quote:
Originally posted by Headshot:
I hope you will post some images, on cS, of your model upon completion.
I will gladly post pics when Pathfinder is built, but I have to advise that my ideas are not met by my abilities — please don't expect a masterpiece!

Regards to all, any more info. or photos etc. will be greatly appreciated!

hotdog
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posted 04-09-2014 08:25 PM     Click Here to See the Profile for hotdog   Click Here to Email hotdog     Edit/Delete Message   Reply w/Quote
It is definitely a surreal feeling trying to replicate an inaccurate test article after being so fixated on building accurate flight-worthy orbiters! I spent an entire day sanding off all of the surface details, filling in the RCS thruster holes and reshaping the stabilizer fin to look like the Pathfinder. It was almost painful watching some of those beautiful shuttle panel lines disappear!

I would be glad to share high-res copies of my images. It may be a few weeks before I get back down there. Not sure how good my pics of the stabilizer fin will turn out from down on the ground. Perhaps I can get a friend to let me up on the roof of the TCF for a quick photo or two.

You are correct that it is 3 feet shorter. It was cut down to facilitate its travel to Japan for a show in the early 1980s. I still haven't decided if chopping off the nose and performing this type of surgery in the name of accuracy is worth it at such a small scale as 1:144, but I imagine you will want to do it at 1:72?

The fin you see on there now is not the one it was originally displayed with the Teledyne-Brown refabrication of the early 80s. At some point in between the move from Japan to Huntsville, the fin either broke, got lost, or was not structurally sound enough for the stack display. I gather this just from seeing pictures of the finished Pathfinder with two distinctly different-shaped fins. I also heard somewhere that it fell off while the crane was mating it with the ET on the display, so perhaps that was it. I do know that the fin that's on there now is the same fin that was originally on the finished stack display, including in the unfinished image you posted.

I cannot take credit for taking that photo, I just had it saved on my drive after finding it online somewhere. However, I did a lot of color enhancement and retouching to it, as it was a rather dusty scan with a few scratches. I did not see Pathfinder stack until it was fully complete in 1989, so I cannot speculate on the true color of the SRB nose cap either. I would just match the photo as best you can if you're going for the unfinished Pathfinder look with your build. Radome Tan, yes, maybe a slightly dirty Radome Tan. Maybe go with the Radome Tan and get the dirty look after painting by adding some light brown pastel weathering?

Sky dancer
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posted 04-11-2014 04:31 PM     Click Here to See the Profile for Sky dancer   Click Here to Email Sky dancer     Edit/Delete Message   Reply w/Quote
Thank you for your kind offer!

In answer to your query - Yes! I would like to model Pathfinder with the shorter fuselage length — I assume it was the nose area that was shortened?

Any info gratefully received!

hotdog
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posted 04-12-2014 02:43 PM     Click Here to See the Profile for hotdog   Click Here to Email hotdog     Edit/Delete Message   Reply w/Quote
Yes, just behind the nose is where Pathfinder was cut. You can see it clearly in this photo:

Here is an image of Pathfinder taken right after Teledyne-Brown fixed her up, and before she was shortened. Note the different tail fin, correct lower-case Helvetica "Pathfinder", and overhead windows that were later filled-in.

Sky dancer
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posted 04-12-2014 05:00 PM     Click Here to See the Profile for Sky dancer   Click Here to Email Sky dancer     Edit/Delete Message   Reply w/Quote
That's a great shot!!

I had noticed that there was a change in shape at the forward of edge of the payload doors before, but I just thought it had something to do with the original payload doors on the "original" Pathfinder - it never occurred to be that this was were the 'cut' was made.

Your photo now explains that! Thanks a mill.

hotdog
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posted 04-12-2014 08:18 PM     Click Here to See the Profile for hotdog   Click Here to Email hotdog     Edit/Delete Message   Reply w/Quote
It's also worth mentioning that in the Teledyne-Brown picture, the Pathfinder payload bay doors have 12 "latches". If you look at an image of her now, she only has 10. The two forward latches are missing, indicating that the section that was removed from the craft.

Greggy_D
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posted 04-12-2014 09:05 PM     Click Here to See the Profile for Greggy_D   Click Here to Email Greggy_D     Edit/Delete Message   Reply w/Quote
Not necessarily. It appears the "latches" are simply painted on. Possibly when the Pathfinder font was changed, the "latches" were painted over. It doesn't appear to me that a section in that area was removed, especially with the square and rectangle markings remaining as reference.

hotdog
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posted 04-13-2014 12:08 AM     Click Here to See the Profile for hotdog   Click Here to Email hotdog     Edit/Delete Message   Reply w/Quote
Compare these two images of Pathfinder. The top image is before she was repainted (we know this because "Pathfinder" is not all upper case). You can count 11 of the painted on latches. In the second picture, taken before the 3-foot section was removed, you can count 12 latches. This, along with the visible seam where the cut was made, is how we know the 3-foot section removed was the forward portion of the cargo bay.

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