We decided to do this project because, hey, who doesnt want a rocket powered airplane? Some of the issues tackled in this project were epic in scope (hot rockets + styrofoam, for example).
The goal of the project was simply to make this work. Eventually, we will interface a camera onto it for some onboard video. This can also be used as a test platform for an autopilot.
As Test Video 5 will show, a successful flight does not always end with a reuseable airplane... but hey, crashing is half the fun.
Reference links for the science are at the bottom of the page. Check these out for a better understanding of aircraft, rocket, and rocket motors.
Project Write-Up
The Airplane: The Turbo Jet 2000
After checking out many commercially available styrofoam airplanes, we opted to use the Turbo 2000, if not for the kickass name, then for the characteristics of the aircraft. The T-2000 had a small wingspan and thus would cope with the acceleration better. It was as light as a feather, a mere two ounces, meaning the rockets would have a greater effect on the plane. It was the cheapest, a setback of $3.50. Finally, it was sturdy and had enough room to mount a rocket without making it look too dangerous. The only real issue we had to worry about was extreme heat and/or crushing damage, which proved to be catastrophic in the T-101 and T-1000 models.
The Launcher
The launcher of a rocket is designed to do two very important jobs. First of all, the launcher is designed to hold the rocket in place securely until it is ready to be fired. The other task of a launcher is to fire the rocket in such a way that it is stable when it leaves the launcher. A rocket is unstable at low speeds, meaning it will tumble out of control. Estes model rocket launchers have a massive rod sticking out from the top of it to keep the rocket moving in a straight line until it gets up to speed... which hopefully happens before it gets to the end of the rod.
Since the airplane will be trying to lift off, we found it best to leave it resting on a set of rails. This is the method that we have used in all marginally successful tests and it has been very reliable. Be it PVC pipes laid on a box or metal rails, the system will work as long as the rails are alligned parallel to each other and are not pressing in against the aircraft.
One thing we certainly found: do not use a launch rod. The aircraft is trying to go either up or down at the start. It will get friction locked onto a rod or any other constrained launch system.
Balancing the Aircraft
The most important task of this project is balancing the aircraft. Stability is based on how the aircraft is balanced. First, assemble the aircraft as per the manufacturer's instructions. Now, balance the airplane on your finger (see picture at right). Wherever your finger is when the aircraft is balanced, mark with a pen. This is the design center of gravity (CG). Next, install everything that will be on the aircraft when it is to be launched. Finally, add weight to the nose or the tail until the airplane balances on the CG once again. Remember, the farther away from the mark that you put the weight, the higher affect it will have. Just keep in mind: more weight means decreased performance.
Another note about finding the center of gravity... We found the lengthwise CG location, but we are also concerned with the vertical CG location. You can find this by pinching the top of the tail and letting the airplane hang down. Draw a line straight down the airplane until it intersects with the location of the lengthwise CG. This is the airplanes actual center of gravity. The engine should be mounted so that the thrust is acting here (aka dont mount the engine below or above the CG, see lessons learned for why).
The important factor here is that the airplane must be balanced at the start, when you have a full rocket motor, as well as at the end, when you have an empty rocket motor. This means that the rocket motor must be placed on the center of gravity, in the dead center of the airplane on the CG mark. Failing to do this resulted in the loss of an aircraft (Test Video Two, below).
(Click to Enlarge)
Heat Management
The biggest problem that we had with this project was managing the heat produced by the rocket. In order to properly balance the aircraft , the engine must be located in the core of the aircraft. The problem... rocket motors produce a lot of heat. Styrofoam hates the heat. The only way to make this work is to shield the styrofoam from the exhaust using a sort of exhaust pipe out the back. We tried several methods over the years.
Carboard? Dont even try.
Aluminum pipe? Conducts through, heating the styrofoam. Also, the exhaust is hot enough to burn it away. A thick enough tube should work.
PVC? Heavy, but it works. It burns slowly and holds the heat relatively well.
Lessons Learned
Proper Balancing
While Heat Management is certainly an issue, do NOT allow it to affect the proper balancing of the aircraft. This attempt was made to keep the center of the aircraft safe from the heat, putting the motor in the back and adding counterweights to the front. Sure, it worked fine when we did glide tests, but the second we launched: FAILURE. Rocket motors work by throwing mass out the back. The rocket motor burning mass away in the back of the plane meant that the airplane was no longer balanced. Check out the results in Test Video Two.
Centerline Thrust
Aligning the rocket thrust is one of the more important requirements. Not doing this caused the failures of Test Video One. Any force applied away from the center of gravity of an airplane will cause it to rotate. In the case of Video One, we placed the rocket below the center of gravity at first, and above it on the next two tries. As you can see, this causes the aircraft to violently pitch and roll. Try to place the rocket motor in the exact center of the aircraft for the best results.
The Heat Deflector
The biggest issue of this project. Do not think that this can simply be ignored. In test video three, the aircraft became stable... because it burnt everything aft of the wings away. Though impressive, this was not an airplane, it was a rocket. Make certain that you use a good heat deflector or the image to the right could be your craft. The tube used to be twice as long. Also note the aircraft in the background. We found cardboard and thin aluminum to be insufficient in the quantities that we used. Try experimenting with thick aluminum, multiple layers of aluminum, or PVC.
Completed Pictures
Looking down the PVC Launch Rail Setup, not a good place to be in a moment.
Downrange during a high angle test of the new metal launch rails.
Damage from Test Video Four. Check out the video below - it flew!
A side effect of fixing the melting problem... the aircraft was used more than once. These were the final repairs made after 9 tests.
Completed Videos
Test Video One - 3 Initial Launches
Initial tests of the Rocket Plane. See Lessons Learned (above) for why this happened. Motor: C-6-7, C-6-5, A-8-3
Test Video Two - Epic Failure
Fresh out of the first year of Aerospace Engineering, Chadwick and Handley are back for another go. This is the first of many times this project has nearly killed us. See Lessons Learned (above) for why this happened. Motor: C-6-7
Test Video Three - The Near Death Experience
Proper balancing had been learned, and the new heat deflector was ready: time for test three. Unfortunately the camera angle wasnt great, but after it leaves the screen, she did NOT crash. In fact, it became stable and flew in a sweeping turn, nearly taking our heads off, before careening into a tree. Motor: E-9-P
Test Video Four - A Marginal Success!
A double feature. The first illustrates the issues with a constrained launch rail. The SECOND, however, is a marginal success of the concept! A successful flight is very close... Motor: C-6-5
Test Video Five - VICTORY!
Video of Test 5, a success! While the aircraft is not reuseable, she flew like a champ, and half the fun is the crash at the end of the flight, right? Motor: E-9-P
Future Revisions
GOT A SUGGESTION? POST IT ON THE FORUM. IF WE USE THE IDEA, WE WILL CREDIT YOU.
Onboard Video - Flight or Crash
Battle Hardening the Onboard Video System and using it as the balancing counterweight. Should make for some sweet video.
Tip Weights
To releive the bending stresses on the wings. Hopefully, the aircraft will be able to complete the flight intact. As well, this would decrease its tendency to roll.
Flight Control System
A LONG term project to throw a roll and pitch control system onto the aircraft. This should keep it wings level, following whatever pitch we want it to. We will ultimately use a microcontroller and two servos.
Safety
Check this information out before you start. This is not meant to be all inclusive.
Knives are sharp. They can cut you.
Same goes for saws.
Rockets are dangerous. They can explode. Dont be too close.
Rockets also make fire, which can ignite things. Bring sand/water/fire extinguisher with you.
The rocket plane's performance is unpredictable. Dont get hit by it.
Random people do not like being struck by projectiles. Inform all audiences. Do not launch near any unrelated person.
Quickbuild Options from the Store (if available)
Buy the KIT(Coming in August 2008) - Comes with all of the instructions and materials needed to reproduce our work.
Two Turbo Jet 2000 airplanes
Example heat deflector for C-type motors and D/E-type motors.
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Aerospace Projects 
.JPG "A Fine Setup. Note the wingtip streamers: the ultimate key to stability.")
.JPG "Finding the Longitudinal and Vertical CG")
.JPG "Chandley Tech's Heat Deflection Unit")
.JPG "Motor is mounted in the back. As the motor burns, the back gets lighter, making it more and more nose heavy.")
_300x106_90.jpeg "When mounted below, the rocket thrust causes the aircraft to pitch up.")
.JPG "Heat damage from an insufficient heat tube.")
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