"What you did must have been a blast. I recall a time when the SRB's sank during a mission. Don't know the specifics, just heard of it at work. I always thought the chutes failed to deploy somehow. Our main task there was the ET of course."
This is pretty off-topic, but if the moderators will permit:
Yes, we lost the SRB's on STS-4 and another (been awhile), IIRC. The main parachutes are attached to the forward deck (NOT the forward pressure dome) of the SRB. The main deck fittings are attached by means of large bolts, which at the time were attached with explosive nuts. When the SRB separates from the side of the ET, a pilot parachute is deployed by firing the nose cap, which pulls out a drogue chute. The drogue slows the SRB and also orients it tail first as it is falling. At about 10,000 ft. a barometric switch detects the altitude and fires initiators that trigger a linear shaped charge surrounding the circumfrence of the SRB. The conical section (called the frustum, because it is a frustum of a cone) is attached to an aluminum grid with dividers that keeps the main parachutes from moving around during powered flight. The drogue pulls the frustum away deploying the three 136 ft dia. main ribbon chutes (made out of nylon strap that individually makes great automobile tow cable!). The chutes come out but are restrained from opening fully by "reefing lines". Shortly after deployment, explosive-actuated guillotine reefing line cutters cut each of the two reefing lines in short sequence, permitting the chute to open in two stages.
On the early SRB flights, NASA wanted to detach the main chutes at water impact to facilitate recovery of the chutes and the boosters without tangling the divers that put the nozzle plug in place to keep the water out of the inside of the booster.
MMC warned NASA that the vibrations caused by the firing of the separation ring during main chute deployment was pretty close to the vibration caused by the accelerometer that detected water impact. They either ignored the warning or requested a change too late for STS-4. The possibility which came true on STS-4, was that the ringing frequency of the sep ring charge would match the vibration caused by water impact. If that happened, the circuits would think the booster had landed and fire the explosive nuts that detatched the main deck fittings. On STS-4 that's what happened, and the main deck fittings detached at altitude. No chutes, the boosters just hit the water, broke up and sank.
The sequence logic was changed by adding a barometric switch to the firing circuit for the deck fittings, so it had to pass through a certain altitude AND sense the impact before detaching the chutes, and later the whole thing was changed a couple of times.
Anyhow, it's been a long time, and I'm not sure what the procedure is on current SRB's.
Be interesting to make a model of SRB sements for a flatcar load.
I've got another historical load. I have two flatcars. One has a pair of HO scale M4A3E8 Sherman tanks. (The "Easy-8's" are easy to spot because I added muzzle brakes to the ends of the main "tubes".) On the other flatcar are two Soviet T-34 tanks. One is intact. But the other has the turret resting on the car deck. A small hole drilled in the chassis of the tank, just below where the turret attached, on one side, plus some judicious black streaks painted on show "what happened". It is 1952. The four tanks are being shipped to some base in CONUS for analysis. It seems the two North Korean tanks were taken under fire by the Easy-8's 76mm high velocity gun. The one T-34 was hit and the turret blown off. The second tank's crew bailed out and surrendered. I haven't paid too much attention to the theoretical weights, and am using regular flatcars, but I might have to change to a heavy duty car for each later on.
Green board all the way!
Trailrider