STS-4 SRBs

[erauskydiver]

So what is the story here? Both SRBs crashed into the water and sank after no parachute deployment. I guess it wouldnt seem odd if just one SRB did this, but both?? What happend?

 

[trailrider]

It's fairly simple: The original setup for the SRB Decelerator Subsystem (SRBDSS), aka the parachutes, was that the main deck fittings were attached to the SRB forward dome (not the pressure dome, but a structure on top of it to which the deck fittings attached) with explosive bolts. These were intended to fire when the SRB's aft skirt hit the water, decelerating and separating the main chutes completely from the SRB. The chutes on STS-1 to -3 had floats in the apex of the chutes and the chutes would hang down in the water to be recovered by the recovery ships "Freedom Star" and "Liberty Star". Damage to the main chutes on STS-3 resulted in removal of the floats for STS-4. The explosive nut on one of the two main deck fittings bolts were deactivated, leaving the other one live to be fired on water impact of the SRB. The idea was to "spill" the chute but leave it attached to the SRB.<br /><br />In the deployment sequence of the chute system, the "beanie cap" on the tip of the nose cone was fired by a small rocket triggered by the decleration of the SRB as it came back into the atmosphere. The beanie cap then pulled the pilot chute out of the top of the frustum, which, in turn deployed the drogue chute. The drogue slowed the SRB somewhat, and caused the SRB, which would usually tumble on separation from the External Tank, to be oriented tail first.<br /><br />At about 15,000 ft, a baroswitch fired the linear shaped charge around the base of the frustum (the conical nose cone), and the drogue chute then pulled the frustum off the front of the SRB. The interior of the frustum contains deployment bags for the three main parachutes. The frustum thus acts as a deployment mechanism for the mains.<br /><br />Unfortunately, the ringing frequency of the explosive charge was approximately the same as that of the water impact switches! (We had warned NASA of the possibility of the switches activating, but were told to make the modifications anyway!) As a result, instead of t

 

[najab]

Wow, interesting stuff. I've got to read it through again a couple times to make sure I got it all. <img src="/images/icons/smile.gif" /><p>><i>...a proposal by the Planetary Society to use a single SRB as a ground-to-LEO booster for the CEV...</i><p>I don't know if it's the same proposal, but it isn't supposed to be SSTO, they are planning to stick a fairly large upper stage on there too.</p></p>

 

[georgeniebling]

is there any video footage of the SRBs "landing"? Do they bob in the water "straight up" or on their sides?<br /><br />also, re: the Challenger silo .... are you saying concrete was poured *into* the debris or just *over* the site to seal it? To pour the concrete *into* the silo and thus interlock the concrete with the debris seems ... odd.<br /><br />what is being/has been done with the remains of Columbia?

 

[drwayne]

I was told that the debris is actually organized and available, and studies have been done on some items since the debris was put in there.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Unfortunately, the ringing frequency of the explosive charge was approximately the same as that of the water impact switches!<p><hr /></p></p></blockquote><br /><br />Wow. That's eerily similar to the problem that killed Mars Polar Lander. (The sensors that said when it had touched ground were set off by the pyrotechnics that separated either the heatshield or the backshell, I can't remember which.) <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[trailrider]

The boosters may bob vertically in the water for awhile, until the cooling of the interior space causes the water level to increase to the point where they fall over on their sides. A diver is then put in the water with a special motorized plug that is driven into the nozzle opening, sealing it. Air is then pumped in and the water out until the booster is floating on its side. A line is attached to the forward deck fittings and the booster winched to the side of the boat (1 booster per boat), which then secures it to the side and tows it to Port Canaveral, where it is returned to the receiving facility. The parachutes are winched onto reels and returned to the Parachute refurb facility, where they are washed (salt water is bad on nylon), inspected and repaired, and then repacked for future use. Likewise, the frustum and drogue chute are refurbed and reused. (At least that's how it used to be. Have been out of touch since 1989, so I don't know about changes, mods, etc., since then.)<br /><br />On p. 51 of the April 25, 2005, issue of AvWeek, there is an artist's conception of the CEV and booster. There is apparently an upper stage composed of a "new cryogenic upper stage based on existing rocket engine technology. Under this approach, NASA would develop a 'Block 2' CEV later for human exploration beyond LEO." The ATK Thiokol drawing shows a larger diameter upper stage and CEV, which looks darned Apollo-like, including excape tower. <br /><br />Just MHO, but with that firecracker underneath, they NEED an escape tower! <img src="/images/icons/frown.gif" /> Thiokol says that using the SRB would obviate the need to man-rate either the Delta IV or Atlas V, since "the SRM is already rated safe for human flight...." !!!! These are viewed (de javued???) as "faster and cheaper" than man-rating the EELV's! <br /><br />What Griffin will finally come up with, I don't know. However, I have to believe he's smarter than that!!!<br /><br />So far as the disposition of the "concr

 

[henryhallam]

If the SRB is essentially unchanged from the existing design, why should it be any less safe than during a shuttle launch? It burns for the same period, and a catastrophic failure during a shuttle launch would be just as lethal. Reliability is improved by using only the one SRB.<br /><br />I agree that generally liquid engines have friendlier failure modes but the shuttle SRB has a pretty good track record.

 

[henryhallam]

Makes sense.

 

[erauskydiver]

Wow, I never thought I'd get such a detailed answer. That was great! Thanks!!<br /><br />As a side note, I finally got a transfer down there to florida... woohoo!!!!<br /><br />

 

[ascan1984]

What previous missions were the SRBG's on STS 51L flown?<br />

 

[georgeniebling]

SG,<br /><br />So Columbia debris ia available for study (I thought so ... isn't it in a hanger at KSC?) but Challenger debris is (as we know) in the silo at KSC but it is retrievable or is it mixed in with concrete and therefore not seperatable at this time?<br /><br />and yes, I know there is really no *reason* why anyone would need access to Challenger debris ... I'm sure all study that could be done has been done ... just seems ... I dunno ... I hate to think of those remains solidified in concrete when a concrete cap on the silo would have sufficed.<br /><br />

 

[najab]

><i>So Columbia debris ia available for study (I thought so ... isn't it in a hanger at KSC?)</i><p>Not a 'hangar' really, it's in the VAB. There is a...exhibit isn't the right word, neither is shrine....room on the 10th floor where it is kept.</p>

 

[georgeniebling]

never fails to amaze me how *big* the VAB is ... to be able to have the room to keep the remains of Columbia in the VAB ... a fitting tribute and I imagine a sobering aspect for those who work there.<br /><br />Why was this done with Columbia and not Challenger and will Columbia be iterred at some point int he future at the Silo?<br /><br />