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Post by bearcat on Feb 3, 2010 23:36:58 GMT -5
I was thinking about this today. It wouldn't be too hard to make a rocket glider if I keep it light. Best way to do it would be to build a fuselage around a model rocket and make enough room for the RC equipment. Then you just load it up with a rocket motor and launch it straight up.
G forces are tremendous in those things. So good chance the wings could come off. In that case, it'd be a good idea to have a deployable parachute. If the plane is heavy enough, compared to the plain old rocket, it'll just slow down the acceleration and not go as high. But if I get a couple hundred feet out of it, I think it would exceed my expectations.
If I do this, I'll start off with the orange foam wing you gave me, Mitch. If it rips the wings off, it'll be a short experiment. But if it works, it would be very cool. I'm thinking a T-tail to keep it from catching fire.
More on this later. When I go pick up the Bird of Time kit, I'll look at model rocket kits too.
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Post by bearcat on Feb 3, 2010 23:40:43 GMT -5
Let me explain further. If the rocket motor is in the tail, it would tend to make the plane tailheavy unless it's balanced for it. And if it is, then once it's spent, it'll become nose heavy.
The way to control this is with a boom and pod fuselage with the rocket motor centered on the CG under the wing. So if I do that, then the tail has to be a T-tail to avoid burning the horizontal stab.
I omitted those details in the first post.
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Post by bearcat on Feb 4, 2010 10:29:48 GMT -5
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Post by bearcat on Feb 4, 2010 10:44:32 GMT -5
If you wanna see how cool this is:
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Post by bearcat on Feb 4, 2010 11:13:02 GMT -5
Here's a few more vids. This one is an interesting concept, although it's not very aerodynamic. He's got six motors and fires them off remotely one at a time, in flight. Sorry about the amateurness of the film, the photographer sucks bad:
This one is hand-launched from a fuse. But I don't think I'd want to be the launcher. Looks a little risky to me.
This one is COOL:
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Post by Lt Swiss on Feb 4, 2010 11:55:35 GMT -5
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Post by bearcat on Feb 4, 2010 12:34:23 GMT -5
That's an interesting read. There is a difference between a simple ballistic boost glider that is uncontrolled and an RC controlled boost glider.
If it is a non-controlled boost glider, the CG has to shift. The CG needs to be forward in boost mode, and shift back to the wing for glide mode. There are several methods to do that.
But for RC mode, the control surfaces have to be used to keep the glider in its intended path during the ballistic phase. In that case, I think just having it with a downward thrust angle, like you would any powered aircraft, would keep it under control.
I have to give some thought to the center of pressure though.
I'll read that document in more detail later. But I'm thinking I could vaguely copy the Easy Star pusher design.
So if the rocket motor is on top pushing 2 degrees down, then I probably need a V-tail and mixer for the servos. If the rocket motor is underneath pushing 2 degrees down, then a T-tail should work okay, hopefully. And probably a carbon fiber boom.
On the Easy Star, the motor is aft of the trailing edge of the wing, but just barely. I'd probably copy that position, because the center of pressure has already been calculated.
Trial and error, baby.
The pod encloses the rocket tube, but has room for a small battery, servos and receiver. I might make the tube angle adjustable inside the fuselage, in case trial and error indicates I need something else. Hmmm...
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