I am currently in the beginning stages of a design project for a club at Miami University. I am starting my research and thought I'd post to get some additional advice focusing on the structural components. I've never built a model from scratch but I do have some experience with model rockets and flying RC planes. The plan is to eventually have a working drone with auto-pilot and a live-feed camera on-board. However, since I have never taken on a project this large before I thought I'd take baby steps.
The vehicle will have a vertical take-off from a booster engine with a controlled ascent with the wings folded in. At the apex, we want the wings to unfold and keep the plane in the air for as long as possible. Since landing seems like a difficult process that required a large flat area and a skilled pilot, we decided to instead deploy a parachute when we want the plane to descend.
I am in charge of the structural development for the aircraft, so I have a few questions, but I am also open to any other advice from anyone who has experience with this kind of aircraft.
1. What shaped and airfoil design is suggested for the tail fins and the wings?
2. What mechanism can be used to unfold the wings? (spring system, etc.)
3. Where should the center of gravity be on the aircraft for the rocket take-off stage and during the gliding stage?
Any other advice or links you can share, will be greatly appreciated!
Replies
Interesting idea. I don't want to be a naysayer, so just take these as "considerations". I'm going to draw on history and observations I've made of the years of being an aeronautical enthusiast.
My perception of a rocket launch is quite violent, and aircraft construction strong enough to withstand it sort of precludes the attributes you normally want in a high performance glider. That being: low weight, long and thin wings, etc. Look at a missile. Some have fixed fins, some have folding fins, but they are always short and stubby. They are stabilizing fins, not wings.
Take a look at the Me 163. It was designed to do almost exactly what you want to do. In fact, they adapted an existing glider design and added a rocket at the back. But, there are two important differences. The wings didn't fold, they didn't care so much about the glide performance. It was designed to go up, shoot off it's rounds, and then glide only well enough to return to the ground safely. I'm not even sure if they returned to their home base or were picked up by truck.
I think the folding wing mechanism will add considerable weight and complexity to a glider design.
A big part of the problem is rocket motors tend to have short, powerful bursts of acceleration. Not the gentle thrust that a glider airframe would be designed to handle. I have seen JATO launches, but those rockets are just for assistance getting off a short runway. They don't have enough thrust to blast an airplane up to altitude.
I'm not sure what your rules are (is this a competition). But what might work better would be to consider a design of a conventional glider, and use an expendable motor pod. Motor/propeller/battery that can drop away after altitude is reached. Either that, or some sort of mother ship that would release the glider at altitude.
1. Most R/C airplanes use flat airfoils for the tail. They are litterally just slabs of film covered balsa. This does have disadvantages, but it's what is used.
2. No idea.
3. Well, the CG in glider mode needs to be where it needs to be. Really rough rule is about 1/4-1/3rd of the wing chord back from the leading edge. For rocket mode, I have no idea.
A booster engine-based launch is a very interesting idea. What role do you envision the autopilot taking during the boost?