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Not to stray off topic, but I was wondering if an informed person could reveal to me the purpose of the yellowish rings towards the bottom of the SRB. They have a fairly rough texture, and I was trying to figure out what they're made of, and what they do:

I've never looked it up, but always guessed that it is insulation to protect the rings from heat.
 
I've never looked it up, but always guessed that it is insulation to protect the rings from heat.

Thanks, that's what I was thinking as well (some kind of spray-on material, or a type of wrap?).

Now, how to model it at ~1/60th scale... :)
 
Not to stray off topic, but I was wondering if an informed person could reveal to me the purpose of the yellowish rings towards the bottom of the SRB. They have a fairly rough texture, and I was trying to figure out what they're made of, and what they do:
The SRB aft segment has several "stiffener rings" to help to maintain its roundness. This is particularly key in the aft segment because of the side bending loads on the aft segments when the orbiter is hanging off the side of the ET, and then at ignition when the orbiter SSME engine thrust tries to bend those SRB segments the other way (and indeed the bend a little bit, enough for the top of the ET to sway out about 30 inches, then liftoff is timed so the shuttle does not take off until the ET nose has swung back from that 30 inches to zero).

Anyway, the stiffener rings stick out pretty far. Actually they are sort of like "H" beams that are “round", if that makes sense (OK, technically, it is a sideways "T" cross section where the base of the "T" is welded to the SRB casing, and the top of the "T" is the black ring you see from a side view of the SRB). So, the tops and undersides of them are hollow.

So, what about the yellow stuff? It is indeed expanding foam. The stiffener rings are black (as are other joints and some shallower rings). The foam is applied underneath the stiffener rings, with a ramp type shape, to deflect water when the SRB splashes down. It is for reducing the water impact forces. I was surprised when I found out about that very long ago, because I would have thought the huge area of the bottom of the aft skirt caused so much impact energy when it hit the ocean, that the ocean impact contribution of the stiffener rings farther up would not be very significant, but apparently it is significant (I think originally it was not there, but was added after STS-1 or at least not long after the earliest missions).

BTW - pretty much anything you see that is pale yellow or orange-ish on the ET or SRB is expanding foam (Excluding a bright yellow remove before flight type covering that each SRB has over its access door before flight). Originally the foam is very pale yellow, almost like butter, then gets darker both with age and also the darkening accelerates rapidly when exposed to direct sunlight. So this is why photos of the same exact area of one part can show a change from light to darker from when first received, then stacked, then rolled out, and then finally when launched. Some shuttle ET's have gotten "sunburned" so most of the tank gets darker, but the areas covered over by the RSS until shortly before launch are a lighter shade because they do not get the same sun exposure (example in 3rd photo below). Also, on the ETs, some areas may be lighter than others because there was new foam added over old foam, OR, old foam was cut into which exposes the pale foam underneath (only the outer skin of the foam tends to darken).

For comparison, the 4th pic shows how very pale yellow the foam can be on an ET (this pic taken on arrival at KSC). That particular one was the first super-lightweight ET, flown by STS-88, flown in 1998. So you can compare that with the 3rd photo, which while not the same ET, shows how much darker the ET’s get. I also think that the ET foam formulation might have changed a bit for the super-lightweight tanks, onwards, since before those I do not recall seeing any pale yellow ET’s, just ET’s that were deep orange to nearly rust brown in color.

OK, 5th pic for comparison, STS-47, 1992 (Jay Apt’s 2nd flight). This was more representative of what the ET foam colors were, and the SRB stiffener ring foam ramps too, before the super-lightweight ET's came out in 1998. Though the colors have always varied, but not as distinctly different from before SLWT's in 1998 and then after SLWT's in 1998.

- George Gassaway

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The SRB aft segment has several "stiffener rings" to help to maintain its roundness...
- George Gassaway

Wow, thank you very much, very good info to know. I was wondering about the color change; they do seem to be a bit brighter/darker in the launch photos (the insert photo from my previous post seems to enhance the color a little unnaturally, but based on the other images taken around the time of the launch they do seem to have darkened slightly).

Again, thanks!
 
Video with parachute deployment
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So, what about the yellow stuff? It is indeed expanding foam. The stiffener rings are black (as are other joints and some shallower rings). The foam is applied underneath the stiffener rings, with a ramp type shape, to deflect water when the SRB splashes down.

While I could tell it was foam, I would have never guessed the purpose had to do with "splashdown". I figured they may have had weakening of the rings due to extreme heat from reflection of exhaust on the pad and radiation from the large exhaust plume during ascent. George, did you just happen to come across all the info you know about the SS while gathering data for your scale models, or are you just a general fan of the shuttle system? It's cool, nonetheless. :cool:

I can just imagine the huge pile of empty cans of "Great Stuff" foam at the prep facilities for the boosters and all the local Walmart/Lowe's/Home Depot inventory guys scratching their heads, wondering why they can't keep the stuff in stock. :D (I'm sure they use something more similar to our two part urethane expanding foams.)
 
Just to add a bit of trivia to George's terrific information- the Insta-foam seems to have first appeared on the SRBs, as best my research can find, on the 10th shuttle mission STS 41-B, launched 3 Feb. 1984.
 
Just to add a bit of trivia to George's terrific information- the Insta-foam seems to have first appeared on the SRBs, as best my research can find, on the 10th shuttle mission STS 41-B, launched 3 Feb. 1984.

I remember thinking how hokey it looked to me when I first saw the "rusty" tank. Now when I see photos or video from the first few missions, the white tank looks bland/generic to me. It's funny how views change over time.
 
I can just imagine the huge pile of empty cans of "Great Stuff" foam at the prep facilities for the boosters and all the local Walmart/Lowe's/Home Depot inventory guys scratching their heads, wondering why they can't keep the stuff in stock.

If only that were true- it would be a good argumant against that old quip that tax money is spent "in space" when actually it is taken home by aerospace workers and spent at Walmart... and there ain't any of those stores "in space." Still, the money trail is basically the same.;)
 
George, did you just happen to come across all the info you know about the SS while gathering data for your scale models, or are you just a general fan of the shuttle system? It's cool, nonetheless. :cool:
Both, a fan of the shuttle and from gathering info for scale models. I think that most builders of scale models HAVE to be a fan of the vehicle they are modeling, to put their best efforts into it.

However, when the shuttle was first being developed in the mid 1970&#8217;s, I never expected that I could build a GOOD scale model of a shuttle someday. I did not have the scale building skills, and did not know how to fly R/C. And some of the technology that would be key to the ultimate model, like the onboard flight computer, did not exist (heck, home computers were only just on the verge of coming out).

My first model was just an orbiter, built the day after Enterprise&#8217;s first drop test glide flight in August 1977. About 1/80 scale very crude orbiter, piggybacked on a long rocket. A full stack shuttle model at about 1/110 scale, still very crude orbiter type and very crude model, in 1979.

In 1983, I made an R/C 1/72 scale R/C orbiter, based on a plan from Model Aviation magazine, though I made my own mods to make it as lightweight as possible (I think 7.5 ounces with 3-channels of radio gear). That one did look more like the real one since I used Monokote, decals, and vac-formed OMS pods and main engines.

In 1984, a boilerplate 1/72 shuttle with ET and SRB&#8217;s, and a boilerplate orbiter that has flown many times on other ET/SRB combos. The idea of that boilerplate was to prove out a version that someone on the U.S. Team might fly at the World Championships one day (such as Matt Steele and John Pursley, while my scale skills were still WAY behind the curve). But, nobody else picked it up and ran with it, at least not at 1/72, for an R/C gliding orbiter (Rob Justis did fly a 1/100 shuttle at the 1983 WSMC in Poland, but it crashed. He never built a boilerplate for it, and it was never going to fly stably the way he did it).

And, many on again and off again attempts to work out an improved shuttle boilerplate thru the years, including experimenting with some other scales like 1/87 and 1/96, and trying other tricks like SRB sep. Also for Sport flying, made a 1/60 piggyback orbiter in 1992, to boost on a very customized rocket powered by the Aerotech 32mm RC Reload (G12 power).

Also thru the years, my scale building improved. First with Juno-I models and a Delta 3920. Actually, in 1985 or so I was deeply researching the Mercury Redstone for an all-scratchbuilt model (2.6&#8221; diameter), but after some fabrication R&D tests I came to realize my modeling skills were not up to the task of making a GOOD Mercury capsule (with all of those dimples in the shingles), so I switched to the Juno-I. Then in 1990 with the Little Joe-II where I started using more new methods, plus casting parts for a Little Joe-II in 1991 (using RTV molds and Alumilite resin).

The boilerplate testing resumed for the 1/72 model, notably again around 1994, but there were more setbacks so it floundered again. Finally, in 1998 there were new incentives to try it again and new technology (the flight computer using two Basic Stamp microcontrollers, built and programmed by Jay Marsh as a modified versions of a flight computer he had made for his FAI Saturn-IB models). Worked out all of the bugs in that boilerplate, and had many successful flights in fall of 1998. Including sepping the SRB&#8217;s, and little wind-up timers onboard the SRB&#8217;s to deploy the SRB chutes.

So that opened the door to finally building a &#8220;serious&#8221; scale model in 1999, which was flown at NARAM-42, and won easily (well, the first flight had a problem and DQ&#8217;ed but it as fixed and the second flight flew well). Also flew it at the WSMC in 2002, where for some reason the flight computer did not eject the ET chutes. Then flew it at the 2002 WSMC, where it worked great. It may only have come in about 10th out of 20 entries there, but it got the loudest crowd reaction of the day when it flew successfully.

Oh, yeah, also some personal experiences with the shuttle. March 1978, saw Enterprise flown into MSFC in Huntsville on the 747. 3 weeks later, MSFC had an &#8220;Open House&#8221; with Enterprise, SRB segments, and an ET on display (wish I still had the photos I shot). August 1978, NARAM was in California. One day, (while others did the Disneyland thing), some of us toured the Rockwell plant in Palmdale, where the orbiters were built. Saw and went inside of a full size mock-up of an orbiter. Did not get to go into where the orbiters were built, but DID see what turned out to be Columbia being built, from a distance, seen thru an open hangar door. Tried to see a shuttle launch of Challenger (STS-7 IIRC) in 1983, but a delay ruined that (fortunately I went there mainly for a rocket contest, so the shuttle launch was going to be a &#8220;bonus&#8221;). Finally in 1992, the stars aligned, when I went to Melbourne Florida for the FAI WSMC being held there that year, STS-47 was launched on the ideal calendar date to see it being flown while I was down there. So that is the one and only time I saw a shuttle launch.

BTW - Link to the shuttle section on my website I still need to get my whole website completed. It has been &#8220;under construction&#8221; for nearly a year since AOL killed everybody&#8217;s AOL web pages.
https://homepage.mac.com/georgegassaway/GRP/Scale/SHUTTLE.htm

Photo captions:
New photo of old 1/110 orbiter built in 1979. My first orbiter, 1/80, in August 1977, was built exactly the same way.

Launch of 1979 shuttle stack at NARAM-21 in Houston (using the 1/110 orbiter).

1984 shuttle boilerplate at 1/72 scale.

1986 flight of the boilerplate using the old Aerotech F 15 motor (tiny point of light offset in ET aft dome). That flight proved out the stability when using a single fin on each SRB at 45 degrees (when enough noseweight was used in the ET nose).

Myself doing some wishful thinking with a large display model at MSFC, in 1988.

- George Gassaway

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More pics.

Data Collection:
Shuttle_data-2.JPG


Captions for below:

1994 testing of 1/72 boilerplate

1998 boilerplate (which finally got it all to work right) alongside the 1/60 piggyback orbiter.

Final 1/72 contest model (of STS-47) which won NARAM in 1999 and flew at two WSMC's (2000 and 2002).

Myself with model at the 2000 WSMC in Slovakia.

Endeavour Squared. Real Endeavour, STS-47 with Jay Apt, launches in September 1992. My 1/60 piggyback Endeavour orbiter in foreground.

- George Gassaway

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I saw one of your R/C orbiters (1/60?) fly a couple of times at the Rocket City Classic at the old airport in Huntsville, I reckon around the early 90's, but I've never seen your full stack shuttles. Seems like the wind was blowing a hundred mph every time I went to a RCC and it made your orbiter recoveries a bit interesting. You always got it down safely when I was there. I flew a lot with old Rocketflite F-50SS Silver Streaks at the RCC launches, and had to walk about as far to retrieve them as you did the "pumpkin chute" rockets in that wind. :)
 
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