Shuttle Debris Protection Question.

[najab]

I haven't been following the tests closely, but what I have seen is that they have shown ways that tanks <i>could</i> shed damaging debris, but that it is highly unlikely. No matter what you do you can never guarantee that there won't be damage. Even your titanium shield could be destroyed...<p>The new tank design eliminates the one area where a large <i>chunk</i> of foam could come from. It will be safe.</p>

 

[cybernomad]

Simple, use an appropriate material for the task.

 

[najab]

><i>Didn't they already add a lot more mass with every shuttle req...</i><p>Yes. The mass penalty of the RMS extension and associated hardware is about 1 000 pounds. I would be suprised if the shield you are talking about could be done under 10 000 pounds.</p>

 

[cybernomad]

Many things were thought highly unlikely. When they finished the new tanks they were surprised that damaging debris was still being shed.<br /><br />I think they just want to hush that fact and not want to be put back months more for another fix.<br /><br />BRB again 2 hrs<br />

 

[cybernomad]

10,000 lbs! You got to be kidding. Explain further.<br /><br /><br />point is the Shuttle is still vulnerable to the same problem, albeit at a reduced level but not by much.<br />

 

[shuttle_rtf]

He has.<br /><br />If you're going to use what you suggest, then it's got to be thick enough to do a far better job the the RCC. So, look back at the calculation of weight for a 2mm shield on the leading edges of the wing. Increase the thickness to the point where it's going to be doing the job you want. You're looking at more like the figure above.<br /><br />It's heavy stuff, Titanium, you know.<br /><br />Basically, for the sake of this being the only time a critical fault has been caused by an impact - note it has happened before - then no. Best to eliminate the chance of a big chunk coming off the tank again.<br /><br />The chunk that hit Columbia was the size of a briefcase, you know.

 

[najab]

><i>10,000 lbs! You got to be kidding. Explain further.</i><p>10 000 pounds is a SWAG, it might be less, but it's definitely going to be over 5 000: a 2mm sheet of titanium isn't going to be enough. It would probably have to be about 4mm. That puts us at a minimum of 3 000 pounds, just for the metal. A thin sheet won't do because of the brittleness of Ti, a thin sheet would likely shatter, a thicker sheet would have the ductility needed.<p>Then you have to add attach fittings (which you can't do without compromising up the TPS), and an eject system (frangible bolts and wiring will add up quickly). You also need to figure out a way to ensure that the shield doesn't recontact the orbiter after ejecting it (cold-gas thrusters maybe?). All in all, it's likely to come pretty close to 10,000 pounds.</p></p>

 

[scottb50]

Kevlar/Carbon weave has been advanced quite a bit. Maybe a composite layered structure, outer Carbon Carbon and inner combined layers. Would certainly add weight, but maybe not that dramatically.<br /><br />With an expendable tank there is only so much you can do, if it was an integral part of a re-usable launcher then the concerns here would be moot. <div class="Discussion_UserSignature"> </div>

 

[rocketwatcher2001]

Kevlar is considered high temp stuff, by most standards, but for the leading edge of the Orbiter, you need extra-super-mega-high temp stuff. Kevlar wouldn't last.....niether would very much else. From what little I know of Kevlar's "replacement" due to hit the markets in a year or so, it can take a lot more heat, but not enough for reentry. <div class="Discussion_UserSignature"> </div>

 

[scottb50]

There is Carbon/Kevlar cloth that could be used behind a Carbon/Carbon layer, adding strength. I didn't mean the Kevlar would take the full heating, just reinforce that Carbon/Carbon outer surface. <div class="Discussion_UserSignature"> </div>

 

[cybernomad]

The leading edges are now currently protected by material (RCC) designed primarily for reentry. I doubt NASA or just about anyone had foam impact in mind originally. (they did not believe foam could do this much damage at first) As far as I know there is no material that is lightweight and heat resistant can also be made physically tough to with stand similar or even smaller impacts for that matter (the recent tests of the new tanks indicated much smaller pieces can still cause critical damage).<br /><br /><br />So what I was proposing at the beginning of his thread through to now is a separate detachable light weight shield designed solely for debris protection upon takeoff. With the right material it need not add much mass. Ceramics used in bullet proof vest come to mind. Note that this shield need not the heat resistance ability of the existing Carbon-Carbon material. <br /> <br /><br />Think about it this way, If heat was not a problem upon reentry would they use the current material? <br />The current material cannot stop a bullet but a thin ceramic can.<br />

 

[cybernomad]

Recent Article Tidbits<br />more...<br /><b>Shuttle Surface More Vulnerable Than Suspected</b><br />By JOHN SCHWARTZ <br /> <br />Published: January 20, 2005<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p><br />he space shuttle's skin is turning out to be even more fragile than NASA engineers thought, its scientists and engineers say.<br />Impact tests and analysis performed as part of the return-to-flight effort show that pieces of insulating foam that weigh less than half an ounce can cause small cracks and damage to the surface coating on the heat-resistant panels on the leading edge of the wing, agency officials said in interviews this week.<br /> <br /> <br />They said the foam pieces could, under the heat of re-entry into the atmosphere, lead to the kind of damage that destroyed the shuttle Columbia two years ago. <p><hr /></p></p></blockquote><br /><br /><blockquote><font class="small">In reply to:</font><hr /><p><br />The new testing showed that a piece of insulating foam just 2.3-hundredths of a pound, or 37-hundredths of an ounce, falling off the top of the external tank and striking a sensitive area of the wing could cause enough damage to bring down a space shuttle, said Donald Curry, a senior engineer at Johnson Space Center in Houston.<br /><p><hr /></p></p></blockquote><br /><br /><blockquote><font class="small">In reply to:</font><hr /><p><br />until the accident investigation showed that foam had caused the accident, many NASA officials refused to believe that the lightweight material could break through the seemingly tough panels, which are made of a composite called reinforced carbon carbon, or R.C.C<p><hr /></p></p></blockquote><br />

 

[earth_bound_misfit]

Wrong, the major foam sheading problem from the ET has been "solved."<br /><br />S_G, I suppose this has been looked into, dunno, you tell me.<br />Could something like aluminium chicken wire be snadwiched into the ET's foam? Surely this could help stop chunks falling off. Something like that safety glass with the mesh in it, it breaks but stays together. <div class="Discussion_UserSignature"> <p> </p><p> </p><p>----------------------------------------------------------------- </p><p>Wanna see this site looking like the old SDC uplink?</p><p>Go here to see how: <strong>SDC Eye saver </strong>  </p> </div>

 

[cybernomad]

from what i heard on a recent program (discovery canada) the debris shedding danger still exists. It came as a surprise to the engineers how small a piece can be to cause critical damage.<br /><br /><br />Their solution seems to be is to inspect the shuttle before reentry. They were not even sure what can be done to repair any possible damage saying not much can be done to repair it in orbit. Basically to mount a rescue mission and thus loose the entire Shuttle to save a few pounds a whole Shuttle in this scenario would be lost.<br />

 

[cybernomad]

Example: Boron Carbide (bullet proof vests) comes in at 2.5 g/cm³. Almost half the weight of titanium.

 

[najab]

><i>They were not even sure what can be done to repair any possible damage saying not much can be done to repair it in orbit.</i><p>I suspect the program on Discovery was a little out of date. There is an effective tile repair kit and the RCC repair kit is in advenced testing.</p>

 

[cybernomad]

its the same article i posted on this thread a few posts back. I think the article is Jan 20 2005.

 

[vogon13]

I had wondered about the spray on insulation used on the steel work of the World Trade Center. If it was shot all over the inside of the shuttles' wings, you would have a structure that could withstand a leading edge breach longer than Columbia did. Long enough to get down to bailout altitude? Idunno. That insulation material is light , but suspect it would complicate maintenance activities considerably. <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>

 

[tap_sa]

Sorry if this is a FAQ but I havent managed to find the answer anywhere; Why is the ET's foam on the outside instead of inside? IIRC insulation of Saturn V upper stages was inside the tanks.

 

[vogon13]

suspect many reasons (don't know for sure)<br /><br />* easier for automatic machine to spray it on outside when tank is finished rather than before you stick the end on<br /><br />* tank circumference shrinks dramatically when chilled, suspect insulation on outside would be easier to inspect for buckling <br /><br />* turbo pumps on engines running pretty close to redline all the time, probably do not want to run too much FOD thru them. <br /><br />* Have to be a hatch or something on tank to get in to inspect. Tank insulation couldn't be inspected with tank full. <br /><br />* more surface area inside lox tank inside than outside means more weight of insulation to do same job (more area because of anti-slosh baffles.)<br /><br />*lox might react with insulation (despite cold). Insulation is chemically complex so you'd have to keep track of lots of possible chemistry, aluminum is just one element, so it would be easier. They have twiddled with foam recipe since beginning of program.<br /><br />*I know the insulation in my house outgassed for years, not sure I want this stuff in fuel either<br /><br />*If a piece inside of tank is dislodged during flight, guaranteed show stopper when it plugs drain line, outside of tank, odds improve to 1 in 113. <br /><br />*Aluminum surface of tank would experience some ( not a lot) of heating during ascent, insulation can char a little and still work. Aluminum softens up dramaticaly when warmed.<br /><br /><br />Hope Shuttle-guy sees this and helps <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>