ET Foam Home thread

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rogers_buck

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I know its too late for the STS, but it would be interesting to catalog some ideas for how to protect an ET type assembly from icing to eliminate the foam problems experienced by the shuttle.<br /><br />Hwere are a few ideas that come to mind.<br /><br />1) ET condom. A plastic envelope baloon filled with He or dry Nitrogen. At launch, the bag would pull away.<br />2) Pyro-foam. When the solids ignite, so does the ET foam. It burns and spalls off at a low temperature that will not damage the vehicle. The foam would burn off by the time the tank hit 20,000 feet the tank would be bare.<br />3) Microwave beams bathing the tank in combination with a thin layer of foam. Ice would be evaporated keeping the tank nice and dry even though it would be cold.<br /><br />These might be dumb ideas, but so is the FOAM!<br />
 
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llivinglarge

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I lol'd at the condom idea...<br /><br />ET's are quite phallic...
 
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rogers_buck

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Don't confuse ideas with engineering. We don't do engineering on SDC threads, but we can have ideas. As I indicated, the STS is what it is. NASA had no other options than to make the foam work. We here have the luxury of proposing new avenues of approach that may well be as near impossible to engineer as the foam or worse.<br /><br />Since the foam seems to be unmanageable, the question remains to be asked what else could be done given the same vehicle configuration. NASA has ultimately solved this problem by not using the shuttle configuration any more.<br /><br />Things like double walled internally insulated tanks are too heavy. Aerogel insulation blankets might be too costly and fragile. Etc.<br /><br />
 
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j05h

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> Don't confuse ideas with engineering. <br /><br />Definitely! I'm proudly part of the peanut gallery. <br /><br /> /> NASA has ultimately solved this problem by not using the shuttle configuration any more. <br /><br />And that is the most practical solution. The next step is to realize they can 3/4 of the needed exploration architecture with existing launchers. <br /><br />The fact that foam, of all things, is keeping America out of space. Foam. Not the USSR, not gamma rays, foam. Hanging unprotected payloads on the side of cryogenic rockets doesn't make sense. <br /><br />Focusing only on the current launch is impossible at this stage. If they fly and foam is shed, that's it. No more Shuttle launches (at least not w/ people). If they standdown and roll back to the VAB, the last Shuttle will have already flown. Even if they fly and no foam comes off, there is still going to be pressure to find alternate access. Dr. Griffin and NASA are in a tight spot. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>
 
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CalliArcale

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<blockquote><font class="small">In reply to:</font><hr /><p>The fact that foam, of all things, is keeping America out of space.<p><hr /></p></p></blockquote><br /><br />Sort of. I'd rather say that side-mounted payloads on a cryogenic rocket are keeping us out of space. Foam will undoubtedly be on the CEV's launcher, but will not be a problem because the CEV itself will not be in the line of fire, so to speak. <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>
 
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propforce

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<font color="yellow">Sort of. I'd rather say that side-mounted payloads on a cryogenic rocket are keeping us out of space. Foam will undoubtedly be on the CEV's launcher, but will not be a problem because the CEV itself will not be in the line of fire, so to speak. </font><br /><br />You know, I have not thought of this until now. Does anyone know if the EELVs have the foam falling off problem? I know that they don't have side-mounted vehicle to worry about, I just wonder if the foam chemistry is different on the EELV than on the ET? <div class="Discussion_UserSignature"> </div>
 
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radarredux

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> <i><font color="yellow">Does anyone know if the EELVs have the foam falling off problem?</font>/i><br /><br />Maybe all those flames going up the side of the Deltas at ignition help bake any foam on to the tanks. <img src="/images/icons/wink.gif" /></i>
 
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j05h

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Delta IV uses same type of foam IIRC. They shed foam and debris, but it doesn't matter becomes there's nothing critical to impact. Calli is right- side mounted payloads don't make sense. We are scared of foam. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>
 
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propforce

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<font color="yellow">Maybe all those flames going up the side of the Deltas at ignition help bake any foam on to the tanks. </font><br /><br />Well... there goes the Boeing trade secret on the foam curing process !!! <img src="/images/icons/laugh.gif" /><br /> <div class="Discussion_UserSignature"> </div>
 
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drwayne

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Note also that some systems have ice itself falling off the vehicle.<br /><br /><img src="/images/icons/smile.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>
 
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backspace

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"Note also that <b> most </b> systems have ice itself falling off the vehicle. "<br /><br />There, fixed that for ya. <img src="/images/icons/smile.gif" /><br />
 
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rogers_buck

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Now that's an idea. How about a phase change foam. Lay it on nice and thick and it looks pretty much like a rougher version of the current foam. Hit it with 110db of accoustic energy and it liquifies and flows off the vehicle as it climbs.<br />
 
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askold

Guest
I love those old videos of Apollo launches with the ice shaking off the lower stages in slow montion.
 
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rogers_buck

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I worked with a guy who had been a pad worker during Apollo. He told me something that I chose not to believe all these years, but perhaps it is worth mentioning in case he wasn't pulling my leg. He told me that they used Kotex to fill cracks in insulation on the Saturn V and that some of that stuff falling off the rocket as it lept from the pad was Kotex. Sounded like a bunch of bull to me, then and now... If someone can affirm or deny the use of feminine napkins I can delete that memory.<br /><br />
 
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askold

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Yeah, those were the days. When men were men, and women --- contributed in their own way ....
 
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vulture2

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The first insulation applied to the outside of a rocket was pearlite glued to the nose cone of early post-war V-2s launched in the US. It came off. The Delta IV switched from spray-on foam like to ET to glue-on blocks to cut down on pollution; it may come off but doesn't hit anything. The only insulation system that really solved the problem was the composite liquid hydrogen tank developed originally for the X-33 program by Northrup Grumman. Unfortuantely, success came to late to save the program, see http://www.spaceref.com/news/viewpr.html?pid=14973
 
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scottb50

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If you enclose the tanks in an outer shell with insulation and an airspace between them and the outer skin the skin would stay clear of ice. Side mounted payloads allow a more compact stack and easier control of the vehicle, why they have to add fins to the SRB when a second stage is stacked on top of it. <div class="Discussion_UserSignature"> </div>
 
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barrykirk

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I would hope that at this point in the technology that<br />control of direction of the rocket is one of the most<br />understand and solved problems.<br /><br />With modern computers, the control problem should be<br />, uhm well trivial.<br /><br />As for making the stack more compact. Well, again that<br />isn't a good reason. The more frontal area, the more<br />drag for the first couple of minutes of flight anyway.<br /><br />I would think that the optimal shape would still look like,<br />say Saturn V?<br /><br />If you need to go with less height, than make the rocket<br />wider or go with a higher density fuel.<br /><br />As for the shuttle, it will stay the same for the next 17<br />launches with possibly some minor tweaks.<br /><br />If anybody wants to gripe that this or that needs to be<br />changed, then those gripes should be addressed to the<br />next generation launcher vehicle.<br /><br />The CLV and the CaLV won't be damaged by moderate<br />quantities of foam loss.
 
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rogers_buck

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Agreed, the issue is mute for the CLV and CALV. However, the ET/foam configuration has been evolved for over 20 years. Volumes of engineering and flight data have been garnered about this configuration. Both the US and the Soviet Union have flown variants and it was felt at one time by both space powers to be an optimal configuration. It can't be that the only lesson from the cryo-side mount configuration is "don't go there."<br /><br />It's impractical to redefine the DNA of the shuttle and make it something better, but one day the configuration might once again suggest itself as an optimal solution.<br /><br />Perhaps with newer composite materials an two-skinned tank with inner insulation would be viable. Or, perhaps some exotic active protection (microwave dessication) would be viable, or some other hair-brained scheme someone might think of. But the here and now is the time to reflect. In another decade all this will be a dim memory.<br /><br />I for one would like NASA to do a retro-cycle on the Shuttle. Formally re-spec the vehicle to include all that was learned in its operation and its failures. A document called something like "How The Shuttle Should Have Been Implimented." This would be a document for history, and not for direct use in the next round of transportation system. I don't know, but I doubt such an undertaking will be compiled in one place. The people will retire, and the information all but lost...<br /><br />
 
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propforce

Guest
Why does the ET foam problem primarily on the LOX tank side and not the hydrogen tank side?<br /><br />Hydrogen is about 100 degree F colder than LOX, so one would think there would be more icing problems and foam cracks and falling off. Yet most of the foam problems (including Columbia) are on the LOX tank section of ET. <br /> <div class="Discussion_UserSignature"> </div>
 
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scottb50

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Probably because the LOX tank is above the Shuttle allowing chunks to accelerate. <div class="Discussion_UserSignature"> </div>
 
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ltm_se

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I belive nasa is focusing on the wrong end of the problem. They will never make the foam 100% secure, there will always be some foam shed. They cannot add more or heavier material to the tank. Sure the foam is the solution to the ice problem. But why do we need to carry the foam to all the way to space?<br /><br />Here are my ideas.<br /><br />1) Stop trying to make the foam stronger. Make it weaker. So weak that it will fall of att low speed during the first seconds of flight.<br />2) Cut the foam in smaller pieces that will fall of more controlable.<br />3) It all else fails. Make rigid foam made of large platisc/composit plates that are tied to the ground. Is the shuttle ascends the ET will be stripped of the protective foam lika a big banana.<br /><br />Another plus of all this is the ligher weight of the tank will let the orbiter carry more payload to orbit.<br /><br />What do you think?
 
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qso1

Guest
You've got some interesting ideas.<br /><br />1.....The foam needs to be on the tank as long as there is the potential for icing. And that potential exists within the lower atmosphere. The icing comes from LOX/LH2 which remains liquid within the tank during ascent. The icing does not stop just after launch.<br /><br />2.....Cutting the foam into smaller pieces makes installing the foam not unlike installing the tiles. More labor intensive equals more expensive.<br /><br />3.....The stripping of the shuttle like a banana introduces other problems. How or what will initiate the strip out?<br /><br />Assuming one of your ideas could prove to work. It will take a few years first to prove it will work. Ground testing of partial tank simulators etc. Any one of the ideas would probably be ready in 3 to 5 years. Just in time for shuttle retirement.<br /><br />Best thing now is to work with what we have. Today we have 15 or 16 shuttle missions left. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
 
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rogers_buck

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Well, you could add active protection to the existing system. Imagine some heavy duty chem lasers aimed along the plain of the tank in a cross-fire configuration. Any foam leaving the surface would have to pass through the beam and "poofed" into vapor.<br />
 
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vulture2

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>>If you enclose the tanks in an outer shell with insulation and an airspace between them and the outer skin the skin would stay clear of ice<br /><br />Essentially this is what Northrup did with the new tank (originally designed for the X-33), however the middle layer is not insulation but composite material that provides strenth and light weight, with an outer skin of metal foil to prevent the intrusion of gas into the composite, and a layer of hollow plastic cells on the inside covered by another layer of metal foil. When the tank is filled with liquid hydrogen, the air in the plastic cell layer freezes, leaving a vacuum that insulates the liquid hydrogen.<br /><br />As to the fins on the CLV, I guess it's just another blast from the past. Seriously, the SRB was never designed to be launched as a single rocket, and even though the steerable nozzel can provide control of pitch and yaw, there is no mechanism to control roll. The fins permit roll control at least within the atmosphere, and at the cost of some additional drag provide a nice "Buck Rogers" motif. Probably roll thrusters will be needed as well.
 
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