Gap Filler Removal on Space Shuttle

[on-ramp]

As an engineer, my first intuitive thought would be to push those 2 protruding gap fillers back into place and apply a little adhesive around the edge for re-entry.

I wouldn't think to remove them, because now you have a thin film of space where the gap fillers were. And that could be susceptable to the heat build-up on re-entry.

All over the news we hear about the success of this repair but was it the right thing to do?

any other thoughts?

[dhoward]

I agree with you. Unless the concern was asymmetrical drag during re-entry if they came loose again? Wish I knew more about the dynamics of how those tiles worked. They seem terribly fragile, don't they?

[singpilot]

The ceramic spacers were there to prevent the tiles from being 'battered' on ascent. They are not needed for descent. Normally they do not loosen and protrude (or at least, no one has seen them before, this being the first real inflight inspection). The worry was that the laminar plasma flow in the highest heating time would be disturbed by the protruding material and cause the wake of the plasma flow from the protrusion to impinge on something downstream, burning it.

The tiles were so fragile to the touch, that the loss of flexibility working in the space suits attached to the footstep of the 50 foot long robotic arm would have made pushing the material back into the gap problematic. It wasn't needed, the idea was to remove it, or worst case, cut it so as not to impede the laminar crossways flow of the heated plasma.

[dhoward]

That makes perfect sense.
First time any one has "seen" it. Kind of makes you wonder, doesn't it?

[gassy]

Yeah, that's what I was going to say.

[singpilot]

Something else to think about. The astronaut was attached to a footrest by twisting his feet into a restraint, attached to the very end of a 50 foot articulated, jointed hydraulically operated boom. Being operated visually by another astronaut inside the shuttle. The operator could not see the end of the boom (and it's human cargo) from his position. He was talked thru the procedure by a third astronaut watching the end of the boom from quite a way away inside the space station that the shuttle is docked with. Even he could not see the bottom of the shuttle and the end of the boom once it went behind the hull of the shuttle. The final positioning was done by vocal commands from the cargo (astronaut) end of the boom. There was a second spacewalking astronaut in the cargo bay standing by in case the first repairman astronaut's comm system failed, or he had some problem.

The repairman astronaut also had a tether attaching him to the mid joint on the boom, and had to hold this tether and it's slack between his legs so as not to touch the thermal tiles. It was attached 25 feet away in case the end of the boom broke, detached or went inop, and gave the spacewalker a second attach point. Even the velcro tool pouch was being held rather than trusting the velcro.

So lets get this straight. Talking to a blind controller. Blind assistant who is monitoring the blind controller. Verbal commands given in three axis where there is no up or down, whose left or right are we speaking of. The tiniest mistake or boom mechanical hiccup or failure means bumping the tiles (dooming the shuttle), or worse, crushing, or ripping the single seal suit.

We won't even discuss the motion sickness aspects here. No horizon. Rebound damping on a 50 foot arm every time the boom moved or stopped. Position keeping movements of the entire station / shuttle combo amplified by the boom. Constant muscle tension to hold feet in stirrups, to hold tether in between legs, to hold the tool pouch. The glare of the unshielded sun.

And these guys made it look easy.

The definition of balls falls somewhere in here. Their commander may not physically have them, but she can fly my plane anyday.

[dhoward]

Agree.
Although I think part of the compexity of that whole manuever comes from trying to hastily throw some new equipment and procedures at an organization not very well equipped to handle anything outside of their normal operating policies.
You and I and a couple of others on this board could have come up with a better way with a PC, some wireless parts and duct tape.
I'm joking, but not really.

[singpilot]

Having been involved with a military program using existing technology thrown together in a new configuration for an unheard of mission, the rules and engineering reviews as well as the flight test regime was incredibly complex. Every design team and service branch rep had their own agenda, and needs as well as reservations and a configuration veto authority. It was a quagmire trying to get anything done in real time. 3 years later we got a useable product. Some of the technology developed will show in the civilian sector shortly. Ron Brown and that crew would not have died in Yugoslavia with the GPS (IBLS) autoland system we developed.

The final product was a compromise at best, and nobody was completely happy, but no one was completely unhappy.

Then along came the farm boys who took the ops guys (myself included) aside. Told the engineers to go away, and said, no rules, make it work and what would you change. 2 months later the bird made world headlines when it found, photographed, identity verified, illuminated, and after obtaining clearance from the highest possible level, took out a terrorist in his car on a coastal road with no collateral damage. All in real time. The vid link was watched live in Virginia as it happened.

Yes, sometimes thinking out of the box does get things done.

But not at NASA.

[singpilot]

Steve Robinson was the repairman. Steve Johnson was the cargo bay backup.

In case you run across one of these guys in a bar and want to buy them a beer.