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        Discussion How would you set up control surfaces on a lifting body glider?

#1 danpass Dec 02, 2011 12:00 AM

How would you set up control surfaces on a lifting body glider?
 
Using the X-24a as an example http://upload.wikimedia.org/wikipedi...4A_diagram.png

I'm mostly wondering about speed control. My design will have the rudder. I'm thinking of angling the wings further down for roll control surfaces and using a split rudder as a simple speed brake.

Or I can go with the rudder ... as a rudder lol and upper body flap for a speed brake (but that disrupts flow over the rudder) and then X-24a style rear body flaps for roll control.

I'm looking to minimize weight and control functions.

It only has to stay wings level and autopilot (I'm leaning toward the Ardupilot Mega) itself to preprogrammed coordinates by way of a simple, falling glide.

Does the APM do elevons? If so I believe that would simplify things. And I could hook the throttle control to a split rudder speed brake. No brake='max throttle' and some/all brake='less/no throttle'.

Would a lower body flap (like the shuttle), dropping the nose, increase the horizontal speed component or just the vertical component? Could that be run as a throttle increase by the autopilot?

#2 jkettu Dec 02, 2011 07:58 AM

That thing was designed as a space re-entry vehicle and has nothing to do with a glider. I would be surprised if it's L/D is more than 3:1. In other words, it will drop like a controlled brick.

#3 ChillPhatCat Dec 02, 2011 08:07 AM

Those re-entry vehicles are heavy since they have to be covered in ceramic plates... that's at least something us modelers don't have to deal with. So, if built light enough it probably wouldn't be that bad, but I would not build it as a glider, there are no redeeming glider qualities about it.

#4 AndyKunz Dec 02, 2011 08:32 AM

Standard elevon mix on the tail (make sure you can get lots of UP for the flare). Rudders are not especially effective on them.

Your elevator is really going to be your throttle, too (just like a glider). At high alpha you WILL experience a lot of oscillations on roll - just let it rock.

A friend of mine flew the original model that now hangs in the AMA museum.

Andy

#5 JetPlaneFlyer Dec 02, 2011 12:45 PM

yep, I'd just use elevons or, if mixing is an issue, have the surfaces split with the outer part working as ailerons and the inner as elevators.

As noted by others, the lifting body as a glider will have terrible glide performance. Basically it's about the worst layout it's possible to have for a glider. Unless you plan on re-entering the Earth's atmosphere then there are no redeeming qualities (other than looking cool:D)

#6 CNY_Dave Dec 02, 2011 02:40 PM

Quote:

Originally Posted by jkettu (Post 20029664)
That thing was designed as a space re-entry vehicle and has nothing to do with a glider. I would be surprised if it's L/D is more than 3:1. In other words, it will drop like a controlled brick.

If nothing else, those teach you how to fly high-alpha!

http://www.dfrc.nasa.gov/gallery/pho...m/EC64-404.jpg

Check out the angle on the pitot probe- I assume it's bent to be horizontal during level flight.


Dave

#7 AndyKunz Dec 02, 2011 03:18 PM

But that one was light enough to fly behind a tow car.

Andy

#8 danpass Dec 02, 2011 04:05 PM

Quote:

Originally Posted by JetPlaneFlyer (Post 20031978)
yep, I'd just use elevons or, if mixing is an issue, have the surfaces split with the outer part working as ailerons and the inner as elevators.

As noted by others, the lifting body as a glider will have terrible glide performance. Basically it's about the worst layout it's possible to have for a glider. Unless you plan on re-entering the Earth's atmosphere then there are no redeeming qualities (other than looking cool:D)

looking cool is always priority #1 :D

#9 herk1 Dec 02, 2011 05:35 PM

This thread might be of some help to you: http://www.rcgroups.com/forums/showthread.php?t=1388037


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