Leading Edge on Orbiter Tail

[haywood]

Does the Orbiter tail leading edge have impact sensors like the wings do?<br />Just wondered.<br />

 

[haywood]

Thank you Shuttle Guy.<br />

 

[drwayne]

I don't always have a good mental picture of what's in the "shadow" of the orbiter.<br /><br />For example, I had to look at some visualizations to see how vortices from the Columbia wing damage where interacting with the OMS pod.<br /><br />It probably helps to have seen the shape of the craft most every day for years. <img src="/images/icons/smile.gif" /><br /><br />Or be less spatially challenged than I am...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[mlorrey]

The orbiter essentially flies with a 40 degree angle of attack during reentry until it falls to about 200,000 feet altitude. So, visualize the orbiter outline, tipped with nose up so that the bottom surface makes a 40 degree angle with the ground. If you were standing in front of the orbiter, staring at the underbelly from the ground, everything you can see is "windward surface" and everything you can't is pretty much in the aerodynamic shadow.<br /><br />The reason the nose and leading edge of the wing need RCC is that when they come out of the 40 degree AOA, the nose and leading edge are bearing the brunt of the dynamic pressure from the hypersonic velocity, rather than the whole undersurface.<br /><br />Part of the problem the orbiter faces in reentry is that its wing loading is so high. This is the pounds of vehicle mass per square foot (or kg/m^2) of lifting surface area. The orbiter's load is about 96 lb/ft^2. The X-33's wing load would have been about 29 lb/ft^2, less than 1/3 of the orbiters, which is why it could reenter with much more conventional materials for its TPS, like titanium aluminide panels.

 

[jschaef5]

What's the critical angle of attack of the shuttles wings? <div class="Discussion_UserSignature"> </div>

 

[drwayne]

I think he was asking at what AOA the wing stalls.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[jschaef5]

Aye, had to learn all about that when doing stalls. <img src="/images/icons/smile.gif" /> I was just wondering what it was for the shuttle since 40 degrees is pretty high. At that point is air still flowing over the wings right or is it essentially in a controlled stall until it gets more into the atmosphere where it pitches nose down and uses the lift created by the wings to glide? <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

At the altitude of 400,000 down to 200,000 feet, the orbiter isn't so much flying as skidding. Their job at that point is to lose as much airspead as possible as fast as possible, so they are essentially in a controlled stall for that stage of reentry. Compound delta wings like the orbiters can fly somewhat stably at high angles of attack. This is why the F-16, F-18, Mig-29, Su-37, and other high performance fighters all have strakes ahead of their wings: to allow high AOA maneuvering.<br /><br />What happens is the highly swept strake generates a vortex over the top of the wing to enhance lift. Any delta wing is going to generate some lift by vortexes generated by the sweep angle of the leading edge. The way it does this is the angle of the sweep causes air under the wing to curve outward, and air over the wing to curve inward. This generates big vortexes at the wingtips, and wherever the sweep angle of the wing changes (like where the strake meets the main part of the wing) a vortex is generated that flows over the top of the wing.<br /><br />If the shuttle were to try to fly normally at that velocity, even the RCC would not be able to withstand the heat, as all of the dynamic pressure of mach 25 down to mach 12 would be exerted against just the leading edge and the nose cone. The plasma generated at that speed for that small of a frontal area would burn up the RCC like a match. By presenting the whole underbelly at a 40 degree angle, their cross sectional area is greatly increased, so the energy is spread over a much larger area.

 

[jschaef5]

Cool, thanks. I hadn't known the reason for the swept wings like that. It makes sense now; i have a video of the SU-35 with the canard on the front. It is flying striaght a level then all of a sudden points straight up but instead of going up it's underbelly acts as an airbrake and the smoke that he has turned on makes huge vortices off the wing. I have never seen an american plane do this. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

http://www.aerospaceweb.org/question/planes/q0176.shtml<br /><br />This is a good page on the F-18's strakes, or as they are also called "leading edge extensions". Particularly this picture:<br /><br />http://www.aerospaceweb.org/aircraft/fighter/f18/f18_46.jpg<br /><br />and this one:<br />http://www.aerospaceweb.org/aircraft/fighter/f18/f18_43.jpg<br /><br />shows the vortex in reality. The following pictures show a computer model:<br /><br />http://www.aerospaceweb.org/question/planes/f18/f18-lex-cfd2.jpg<br /><br />Here are pics of vortexes on F-16 and F-22:<br /><br />http://www.cloud9photography.us/sub-v-003.html<br />http://www.fluidmech.net/gallery/vortex/sw1065.htm<br />

 

[sorehed]

Delta wings don't exactly have a critical aoa like other planforms. They just sort of mush into a stall.

 

[llivinglarge]

What would happen if something were to hit the tail's leading edge and cause Columbia-like damage?

 

[vogon13]

Slight increase in drag of the vehicle would not be significant unless damage was 'large'.<br /><br />Flight control software would delay/ reduce use of the RSB. <br /><br />Assymetric (aerodynamically) damage easily countered with other control surfaces.<br /><br />On STS-1, NASA almost found out about aerodynamics of vehicle with out the body flap . . . <br /><br />{but that's another story}<br /><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>

 

[llivinglarge]

Speaking of STS-1... Anyone got pictures of that warped landing gear?