Is This Repair Too Risky?

[hurricane4911]

Becuase of the sensitivity of this mission, every detail is under the proverbial microscope. Truth be told, foam has been flying off the ET for years. Two days ago, the St. Pete Times published an article with a graphic documenting that the orbiters have been struck over 25,000 times by debris.<br /><br />The questions are:<br />Is going out to repair the felt too risky?<br />Can more serious damage be done by the robotic arm or Robinson?<br /><br />IMHO, this must serious to risk a spacewalk and potentially damage the orbiter further.<br /><br />Your thoughts?

 

[drwayne]

This points out the issue I have been mumbling about for a while now. We really don't have a database of what a shuttle looks like in space. We know what they look like after re-entry (and we have seen lose gap fillers then) - but what they looked like before those vehicles re-entered, we really don't know. The fact of the matter is, we don't *really* know what fatal damage (i.e. Columbia) really looked like.<br /><br />So we really don't have an experience base on which to judge our actions, the risks and the consequences. We have to fall back on models that could well be wrong.<br /><br />This same sort of problem of available data also plays into the go/no go decision logic.<br /><br />And finally, I do not know how to assess the training/readiness of the astronauts to do this operation.<br /><br />So, to finally answer your question, I don't have the data to do much more than worry, and trust the controllers, astronauts and scientists have the data to weight re-entry risk versus risk of further damage.<br /><br />One somewhat less negative thought. If they have a problem and do significantly damage the TPS, then the ambiguity in the situation will be resolved, and we are looking at a ISS/lifeboat situation. <br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[shuttle_rtf]

It's a test flight, this is a good test of repairing a section of the TPS on the underbelly of an Orbiter. It's risky, but so's travelling at 17,500 mph in LEO <img src="/images/icons/smile.gif" />

 

[drwayne]

Its the part when things start to slow a bit that always worries me.<br /><br /><img src="/images/icons/wink.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[shuttle_rtf]

I hear you! <br /><br />I think the best way to show what deorbit and entry interface is like is the Clint Eastwood film, Space Cowboy. That showed the speed well.

 

[hurricane4911]

Yes, it is a test flight to test "scripted" repair techniques. This is not scripted. Statements were made that this level of protusions may have occured in the past, but re-entry destroyed whatever evidence there was. But, post-flight inspections would have indicated missing filler.<br /><br />That's why I'm somewhat skeptical that this protrusion is "routine". I just can't see NASA going to this much effort "just for the heck of it because it's a test flight" (my words).<br /><br />Everything about this business is risky. Why assume a higher risk when it may be totally unecessary?

 

[gpurcell]

What infuriates me is that, 25 years into the program, this is the first time they think it is important to do this type of on-orbit assessment of the TPS.

 

[centsworth_II]

I feel your pain. It seems that this level of scrutiny should have been devoted to the FIRST shuttle orbiting missions. <div class="Discussion_UserSignature"> </div>

 

[arconin]

Of course nobody wants to see another tragedy but this stuff is not what caused Columbia to disintigrate. It was the large gaping hole in the wing, right? Precautions are nice, but there come a time where you have to say " we are on STS-114 not STS-1, we are confident that this stuff wont cause a catostrophic failure on re-entry based on the previous 25 years of experience.<br /><br />Now, if their new models are showing them something different and we have just been lucky these past 25 years, I dont know that the shuttle should fly ever again, I only say that with the impending retirement date looming, I am not knee-jerk anti-shuttle by any standard.

 

[viper101]

Agreed - this should have been something looked at 20+ years ago. It's amazing that is has taken this long. Imagine if they were still perfecting the Gemini capsules in the 1980s....

 

[starfhury]

I really think they are being over cautious. Columbia was lost due to damage to the heat shield. If Discovery encounters a fatal heat shield problem again and every thing wasn't done to eliminate it then these guys would be murderers. I'm sure Discovery probably has the cleanest heat shield since the first launch, but they can't take a chance. Plus who wouldn't want to take a chance in making history? This will actually be the first on orbit repair of the space vehicle returning to earth. This will set a precedence for future repair and is a small step in building and repairing ships in space all together. <div class="Discussion_UserSignature"> </div>

 

[hurricane4911]

<font color="yellow">"I'm sure Discovery probably has the cleanest heat shield since the first launch, but they can't take a chance."</font><br /><br />On the surface, a very good statement. But take a look at it from this perspective.<br /><br />If this is indeed the cleanest an orbiter has ever been, why do the spacewalk? A statement saying that we have seen this before, and there is no concern would be fine with me.<br /><br />I cannot fathom NASA would go through these motions if they are unecessary. Doing the repair "as practice" just doesn't sit well with me.<br /><br />If that is indeed what they are doing, IMHO it is a big mistake since they are focusing attention "non-issues". Of course, if their goal is to hasten the shuttles retirement, well, that's a topic for a different post.<br /><br />

 

[Testing]

I would have to say moving a 600+ pound Rate Gyro by hand twice involved considerably more risk than trying to extract a splinter of gap filler. <div class="Discussion_UserSignature"> </div>

 

[drwayne]

I do not see the parallel. One is an exercise in dealing with massive objects. The other is an exercise in dealing with relatively small (remember the gloves) objects in the presence of items (tiles), which are not *that* rugged.<br /><br />In both cases, oops is not something we want to hear, but I see the challenges and the risks as quite different.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[Leovinus]

My guess is that this is not the first time that the spacer stuff has popped out. The fact that we saw it the very first time we looked at the bottom of the shuttle tells me that it must be common. And it never brought a ship down before. I'm surprised that anyone thinks this stuff will harm anything. I'd expect it to incinerate within milliseconds of entry and not be a factor. But I'm no expert. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[tomnackid]

Didn't John Glenn reenter with the entire retro pack still strapped to his heat shield? Unmanned Gemini capsules with hatches cut into their heat shields were tested with no ill effects. I'm not sure why an inch of felt is causing so much concern. I don't know if NASA is being overly cautious so that if there IS a problem they won't be accused of ignoring it, or the news media are just overhyping the whole situation.

 

[Leovinus]

My nightmare is that the guy pulls the felt and out pops a tile. <div class="Discussion_UserSignature"> </div>

 

[drwayne]

Different situation with Glenn. Much different type of heat shield, and idea of using the retropack to hold a potentially loose heat shield into place was really the only play they had to call.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

"My nightmare is that the guy pulls the felt and out pops a tile."<br /><br />Or two. Yes, I worry too much... there is a reason why I could not manage such a program, or be president, or...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

But, looking on the pseudo-bright side, pulling a few tiles off would probably remove the ambiguity from the safety situation.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[mrmorris]

<font color="yellow">"...looking on the pseudo-bright side..."</font><br /><br />So... if the ozone layer were to simply go *poof* and disappear tomoorow, you'd consider it having a pseudo-bright side like: "At least you don't have to pay for a trip to Florida to get a nice tan." ??? <img src="/images/icons/smile.gif" />

 

[hurricane4911]

<font color="yellow"> I don't know if NASA is being overly cautious so that if there IS a problem they won't be accused of ignoring it, or the news media are just overhyping the whole situation. </font><br /><br />It's probably both. One can understand the media overhype, but NASA shouldn't overreact and schedule an unrehearsed spacewalk to appease pundits.<br /><br />That is bad decision making.

 

[drwayne]

Since I live in Florida it would remove the worry factor from *whether* I was going to get skin cancer.<br /><br /><img src="/images/icons/wink.gif" /><br /><br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

I remember seeing some flow plots back in the Columbia time frame, I just can't remember where...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[ehs40]

we wont know if it is risky untill he starts to try but i agree we should have been worried about this kind of stuff on the FIRST shuttle mission