<i>Run a 100 tests in a day until the foam does not come off the external fuel tank.</i><br /><br />Real tests should be run with ET (or, say, surface to which the foam is applied) temperature close to the hydrogen boiling point. These are rather expensive.
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I've done painting for the government and NASA. Pre columbia, we werent even given a specification for painting for nasa. Post columbia the spec for paint is about 60 pages, all concerning test.<br /><br />But if I expect the "green paint" under the foam is infact 23377 polyamide primer, the top coat must be applied between 2 and 20 hours after application of the primer to guarantee good adhesion of the topcoat. In this case the topcoat is foam. I doubt if it is applied 20 hours after primer.<br /><br />There is no quick fix using the current system. Long run would be cheaper to strap her to a rocket or three to get her flying. The only way to protect the heat shield is to cover it during ascent, and let the foam fly off it necessary. But how can you put it on the shuttle and remove it without damaging the tile? You couldnt leave it on the ET cuz I dont think they could control where it goes with a wing on it. But even an aluminum shield around the half of the tank on the shuttle side would be better than saying they dont have an answer.
In this picture you can see a tile broken or something wrong with a tile.<br /><br />It is right below the nose a little bit to the right of the image. You will see it better if you zoom the image.<br /><br />http://www.nasa.gov/images/content/123677main_8M2C2673_hires.jpg
Some thoughts on the foam<br /><br />It has been my experience that closed cell spray-on foams will absorb water. On the ET that means that absorbed water is going to freeze and expand and thereby crack and weaken the foam.<br />If this is part of what is going on with the ET foam then maybe some type of waterproof barrier coating (such as a flexible paint) would help keep the moisture out of the foam.<br /><br />It has also been my experience with spray on foams that they outgas as they expand and harden. So in the case of a patch to existing foam, the newly sprayed foam will outgas against the surface of the already cured foam, some of which gas will then get trapped in place causing a void. That void then becomes a pocket for moisture, that in the case of the ET, will freeze and expand, further weakening the bond between the patch and the parent material.<br />One possible solution to this would be to cut a piece of already cured foam to the necessary shape to fill the void and then bond it in place.<br />Another possible solution would be to dip some kind of reinforcing material such as wire, thin graphite or fiberglass rods, or bamboo sticks, in glue, stick them in the parent material where the patch needs to be and then spraying on the new foam over them. This way they would act as Z-axis reinforcements that would help the patch stick to the parent material.<br /><br />Adding some kind of fiber reinforcement to the foam as it is sprayed on will also help hold the foam together in the places where moisture does get in and then freezes. But this most likely will only add reinforcement in the XY plane and would not work for a patch.<br />It could also be that bonding/welding some kind of reinforceing rods normal to the tank surface (Z-axis reinforcement) prior to the foam being sprayed would also be a big help in getting the foam to stay on the tank.<br /><br />Another thought is to hold off on filling the ET until the last possible moment before launch as an attempt to
From what I have seen so far it looks like Discovery is in as good a condition as any shuttle that has ever reached orbit (with the exception of the Columbia's last flight, of course). So it doesn't look at all like ANY kind of rescue mission is going to be needed. To the best of your knowledge am I correct?<br /><br />If this is the case then I suggest that all disccussion now center on the futuure AFTER Discovery comes back safe and sound!
The FOAM is just bad engineering, sorry to say. Some may remember the whole discussion and my comments directly after Challenger -<br /><br />The RCC is too brittle to suffer impact -<br /><br />The Tiles can abosrb some due to their friability/dent/gouging -<br /><br />The Foam is a losing solution from day 1 because of the 10^12 cells that are fracture initiation sites - plus the 10^3 inches of seams at least -<br /><br />Made worse by 1. low temperature cooling, and terribly worse by 2. Hi rate embrittlement<br /><br />Solutions - saran wrap, vacuum bottle, the removable at launch tank cover - not bare foam -
I didnt want to start anything, just that I thought the reason the shuttle was developed to conserve parts.<br /><br />I dont think the down time or threat of losing life is worth worth the cost of a rocket.<br /><br />If the paint on the outside helped keep the foam waterproof, then that is a great answer for me, although a reinforcing wire would be a good addition. And there should be no empty spaces in the cable and fuel pipe area. If the area was completely filled with foam and the turbulence was reduced, I dont think the foam would have peeled.<br /><br />As far as the rockets, if two rocket boosters are the extra punch the shuttle needs with two of her engines running at 100% or all three at 66%, a 6 pack of boosters might launch the shuttle without her engines running, so there is no need to build the super rocket again, just the 6 pack of boosters they probably already have in stock.<br /><br />I'm sorry to sound like such an idiot, but the speed of the shuttle, is that critical to get to 17,500 miles per hour in 8.5 minutes? I mean if they got there in 15 minutes and reduces stress on the parts by 40% could the shuttle still get up in orbit with a safer ascent stage, less stress on the foam and less chance of damaged tile?<br /><br />Does anybody know about Russias old liftoff procedure?
I *do* think it looked better and I completely understand *why* the white paint was eliminated but ... WHY was it there in the first place? Image?
> <i><font color="yellow">When we repaired the foam we always painted it again IF if was on the side which the press could see, otherwise we did not paint it.</font>/i><br /><br />LOL ! <img src="/images/icons/laugh.gif" /><br /><br />Whenever I see video of a Saturn launch in the future, I will always have this in my mind now!</i>
SG, little things like this is why you're such a joy to have here! That's too funny .. I'll have to look at some old footage and see what I can see ;-)
sometimes it's better to tell the old guys off and go your own way, dare to try new stuff, make mistake, blunder...<br />that's how science and technology evolved...we seem to have forgotten that. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>
I've seen a process like that in my work. Unfortunately, what results is what I call "The idea that never dies".<br /><br />It goes like this:<br /><br />(1) Someone thinks of a way to to something. It makes sense at a top level, so efforts are funded to develop it. These effort uncover problems which make the promising method not so promising.<br /><br />(2) Effort gets dropped<br /><br />(3) Years pass<br /><br />(4) Young folks think about the same idea. They assume the previous work had been done by fools and buffoons who were too stupid to do the problem. Or they did not have enough of a can-do attitude. Being much smarter than the old timers, they will make it work.<br /><br />(5) Young folks discover the same problems, the cycle continues.<br /><br />I have seen cycles of this play out within my career. It would be amusing if I did not know what real dollars were being spent doing this.<br /><br />Like everything in life, there is a balance. You have to balance listening to what you seniors tell you about what can and can't be done, but at the same time you have to be ready/willing to challenge ideas and data at times. It is a very tough balance to develop and maintain.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything." Admiral Jackie Fisher</p> </div>
I meant,try a novel way to do things. Do your research first, but don't fear to stray from the beaten path 
<div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>
<div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>Some geniuses, (Feynman leaps to mind), would NOT read the work done in an area - they would just start from scratch and work foward. I can tell you however that in my case, I am NOT Richard Feynman, so I have to do my homework.<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>
By the way, on a number of my trips to White Sands Missile Range, I went by the outdoor museum displaying a lot of missiles from the 40's and 50's.<br /><br />One had to be struck by the obvious element if trial and error that was in evidence. These days, development and testing costs have become *so* high, not to mention the political cost if something fails, that that method of learning does seem to have been taken away from us.<br /><br />I think that something special has been lost.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything." Admiral Jackie Fisher</p> </div>
I was watching a documentary once on that Russian rocket engine the US took over - RS something, forgive me, I can't remember the number!<br /><br />It was very efficient because it used something the US engineers' paper studies said couldn't work. So the US engineers didn't try it. The US methodology was to spend a lot of time on paper designs. When you finally built something it was pretty close to what you'd end up with.<br /><br />However, the Russian engineers had a different methodology. They built a rocket engine; tested it; thought of some ideas to improve it, and built another. After 20 or 30 cycles they had a good engine.<br /><br />The US engineer that commented on this difference didn't say the Russian method was superior on average, but he did say there was something to be learnt from it.
From what I understand, the large piece that came off was actually part of a patch. Was this patch repairing previous damage (ie: not part of the original insulation application) ?<br /><br />How did the tank fare otherwise... because other than what appear to be 'minor' scuffs and pits (I'm no expert, of course, but I haven't heard the experts ringing any alarm bells), the tile damage doesn't sound too bad compared to previous flights. If this patch was the only significant piece of foam to come off the ET... then maybe this is more a matter of investigating the patching process rather than returning to square one. Maybe it still does validate the work that's been done over the last 2 1/2 years and simply points out that only the patching process needs to be re-examined. <br /><br />Just tossing out some thoughts...
The big probelm i see here is any lack of real world testing done with the ET and the foam.<br /><br />i worked at a vehical testing facility and was thier for a first hand problem that arose from doing only testing via computer simulation.<br /><br />the total design and testing of an SUV was done soley based on computer simulation and no real world testing was done on the vehical. very shortly after the release of the vehical they discovered that a fuel line nut would vibrate loose and squirt fuel on the exaust causing the vehical to be destrioed in a nice little fire.<br /><br />NASA should have done some real world testing of the ET every thing from shaker tables to wind tunnels to eaven possabley a launch of the ET and SRB's sans the shuttle.<br /><br />Computer modeling and simulation has come a long ways but in no way what so ever can it replace real world testing.<br /><br />and one follow on comment reading some of the peoples comments of thats impossable that cant be done. <br />thies 3 laws are from one of the great minds of our generation<br /><br />arthur c clarke's 3 laws of science<br /><br />1."When a distinguished but elderly scientist states that something is possible he is almost certainly right. When he states that something is impossible, he is very probably wrong."<br /><br />2."The only way of discovering the limits of the possible is to venture a little way past them into the impossible."<br /><br />3."Any sufficiently advanced technology is indistinguishable from magic."<br /><br />just somthing to think about the next time you want to say somthing is impossable<br /><br />gawin
Let me take a step further....<br /><br />The testing you mention is neccessary but not sufficient. You have to fly.<br /><br />I love and believe in realistic HIL testing. Period. But I also know that for things with enviroments as seemingly simple as an infrared seeker, things happen in the real flight regime which you don't anticipate and don't fully test against.<br /><br />You gotta fly. <br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything." Admiral Jackie Fisher</p> </div>
<< then maybe this is more a matter of investigating the patching process rather than returning to square one >><br /><br />Based on what I have been hearing, and not hearing, my thoughts have been running in the same direction.<br /><br />But even if this is not the case it would appear that some of the ideas suggested on this thread would be fairly quick to try out and would have a pretty good chance of solving the problem what ever it is.
Some random thoughts...........I see two primary problems here.....the foam sheds and it can contact (and damage) the shuttle's vulnerable (forward facing) surfaces............I'll try to apply some common sense logic to this..............<br /><br />First, the foam sheds because the outer layers melt while the inner layers are frozen....the foam's purpose is to keep ice from building up on the tank, then shedding during flight. I know that weight and time are issues, but are they greater issues than safety? The only soution I can think of is a thin metal layer over the foam, perhaps stainless or titanium (or even an unobtanium) that would contain the foam, unless some composite material I am not aware of would work. Too simple, or too much weight? <br /><br />Second........why not protect the vulnerable surfaces? I know that they are desoigned to withstand the forces of reentry, which are spread rather evenly over the surfaces, leaving them vulnerable to the focused loads of debris contact. Why not add some sort of metal or composite shield to these surfaces which could then be shed in orbit, returning these areas to their present state? The shuttle now uses two rockets and a tank to lift off, why not have unobtanium shields that would withstand impacts, then would be removed in orbit?<br /><br />I would not be surprised if there are many good reasons why solutions such as these have been considered, then discarded, but sometimes engineers can become so focused, so overloaded with detail and imagination, that the simple, basic and logical can become lost or unseen. I understand that time and weight are huge factors here, but my practical racing car experience (IMSA prototypes) tells me that a soultion is more important than the obstacles to the solution.<br /><br />Thanks for bearing with my two cents.
Upon further review of this thread.............and please forgive my ignorance...........<br /><br />Do not all foams, by definition, have air or gas filled voids of some size in them? If so, could part of the problem not be the difference in atmospheric pressure at launch (sea level/14.7 PSI) and the constantly lowering ambient air pressure on ascent causing these voids to expand, eventually compromising the foam layer?<br /><br />Just a thought.
IIRC, an open cell foam would not experience this, closed cell would. If mechanical strength of closed cell material is high enough, it would still work.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>
I'll take a stab at starting a reply...<br /><br />Paint? The paint that was used did nothing to keep the foam together. I think the jury is still out on whether other materials designed expressly for encapsulation might work.<br /><br />Fibres: Unresolved issue on this thread with fibres is the danger that this may just make bigger chunks rip away as the piece falling off takes more of the surrounding material with it. May still have some merit.<br /><br />Sheild: New idea but my thoughts are in order to withstand the kinetic energies involved in a worst case strike, you'd need one hell of a plate of armour... and this would be too heavy. <br /><br />Mounting Shuttle on Top: This was discarded because of issues with weight/balance. The C of G was too far out for this to be flyable. The Soviets also slung their orbiter on the side of Energia for similar reasons.
"I wish I had time to read thru all of these posts. The answers to my questions are probably in here somewhere. <br /><br />Did the paint (on the tank on the early flights) help at all in keeping the foam together?"<br /><br />SG alone has answered this question at least half a dozen times. The answer is no.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything." Admiral Jackie Fisher</p> </div>
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