Setting a new standard in rocketry
Star Wars X-Wing Fighter
A long time ago, in a garage in Santee, California, a group of slightly insane rocketeers decided to make a flying scale model of the X-Wing fighter from what is arguably the best movie ever made, Star Wars.
We decided to make the project to celebrate the 30th anniversary of the first Star Wars movie. Our club members are making several Star Wars based projects to fly at Plaster Blaster VI, or Plaster Wars.
We decided to make the project challenging in several ways. The first is just the massive size of the rocket. It is over 21' long, with a wingspan of over 19'. We opted to use a cluster of four motors to emulate the "real" X-wing, and positioned the motors in the wing pods. The real challenge was to make the wings move in flight, from the "attack" position, or extended to the "landing" position, or folded. This proved to be quite a mechanical feat.
We started be laying out the rear fuselage section and wing root sections in CAD, then had RMS Laser and Routing Services CNC route all the fuselage and wing root components. The fuselage ends and wing root sections are cut from 3/4" Baltic Birch, while the internal stricture is cut from 3/8" Baltic Birch. The "wing box" assembly, or center of the fuselage, contains the electrical motor and gear / chain drive system that moves the wings, along with the center supports for the wing panels.
Here is the wing box assembly with one of the wing root sections in place.
The aluminum rod near the center is one of four 1" solid rods that form the pivot point for the wings. We needed solid rods as the wings will see the lateral stress of the motors, which will likely be large Ms. At this point we are just fitting the pieces together, so nothing is glued. The entire structure is is machined with keys and slots, so it assembles like a giant doll house.
The wing motion mechanism proved to be quite a challenge. The wings, including the root sections and the outer panels are about 8' long and weigh 60 pounds a piece, including the motors. The motion mechanism had to be able to move all 4 of these simultaneously, while keeping them in position relative to each other. Additionally, the motion hardware had to be strong enough to keep the wings in position once they were at the extents of their travel. We used an electric motor from one of my R/C helicopters for the drive motor. This motor is a brushless motor, about 1.75" in diameter, designed to operate at 22.2V drawing 75 amps. The motor turns about 40,000 RPM. We needed to reduce the motor RPM to generate torque, so I borrowed a few more parts from the helicopter. We used an 11 tooth pinion gear on the motor, driving a 168 tooth nylon gear. We machined a shaft to adapt the center of the 168 tooth gear for another 11 tooth pinion, then drove another 168 tooth nylon gear. This gave us a reduction of 233:1. The output of the second nylon gear drives a 12 tooth chain sprocket, which in turn drives two 57 tooth chain sprockets, one for each side of the ship. This further reduced the drive mechanism. The two 57 tooth sprockets drive an assembly of lead screws, one left hand and one right hand, that have lead nuts on them which in turn move the wings. The total gear reduction is 680:1, making the wings move slowly but with tremendous torque. The wings take about 35 seconds to travel from open to closed.
Here is the motion hardware. The left picture shows the chain and gear without the lead screws in place. The right picture shows the lead screws. You can see the motor and gear box in the right hand picture.
Here is the gear box and motor assembly. It is just C Clamped into place at this point. It will be bolted once the mechanism is tested. The yellow box in the front of the picture is the battery that will drive the system, and the R/C receiver and motor speed controller can also be seen.
The entire gear box assembly is removable for servicing, along with all the radio gear and batteries. Access is gained to the units from hatches in the top and bottom of the rocket.
The two rods visible in this picture are the lower pivot rods, forming the hinges for the lower wings.
The rocket is upside down in this picture.
Ok, due to me dropping my camera, we are lacking pictures for a couple of weeks. We have now completed all four wing braces, and have glued the wing box together. The wing motion hardware is in and tested. We spent lots of time playing with moving the wings in and out. We were really kind of surprised it worked as well as it did.
Here is what the rocket looks like from the front (the nose section is not on it, just the wing box). We are doing most of our work at night at this point as we are in the middle of a heat wave and it is well over 100 during the day.
The wings are extended here, but the outer panels are not on it. They are bolt-on for transportation and assembly. The rocket has to come apart to fit it into my trailer and for assembly and storage. It is big. Very big.
Here we have built and sheeted the aft section, and have installed the main motor tubes and engine covers on three of the four engine sections. The structure of the rear is 1/4" birch ply on end, sheeted with 1/8" birch ply. This section needs to be string as the rocket will be sitting on the aft end on the pad. The wing inner sections are also sheeted here.
The motor tubes are 5.38" diameter. We will reduce them to either 98mm, 75mm, or clusters of 54mms, depending on motor configuration. The final weight will determine what we fly it on, so we are reserving making the motor mounts until the final weight is determined. We are estimating about 450 pounds on the pad.
Here one of the outer wing panels has been roughed up and clamped into place. Each wing panel takes two full sheets of 1/8" plywood. We will be making the wings a laminate structure of plywood skins and foam in the center. It is the lightest construction that will take the stress of flight we can come up with.
After hefting the wing box assembly in and out of the shop each build session, we came up with a solution. Steve M. loaned the project his small 4x4 trailer and modified it with rails to support the rocket, making the 175 pound wing box assembly a lot easier to move around. What a life (and back) saver!
With the wing box resting on it's very mobile trailer, construction starts on the nose section. This section is built very much like an old style model airplane, with bulkheads and stringers, sheeted with thin ply. The bulkheads were CNC machined by the great people at RMS laser and Routing Services of El Cajon. The RMS people are hobby friendly and super people to work with. They also do all the laser and router work for the Polecat Aerospace Kits. Give them a call if you need custom laser or routing work! www.rmslaser.com 619-562-5943.
The nose section was very difficult to construct, having to get everything aligned and straight. There was a lot of adjusting, bending, pulling, swearing, drinking, and some crying as we did our best to make it straight.
Each piece of the airframe had to be machined and fit to the assembly. The complex geometry of the structure made it fun to get things lined up so the skins would lay flay and join to each other. Once a stringer was fit into place, gussets were added to strengthen the structure and allow it to support it's own weight during assembly. Once the skin was on it, the fuselage would gain flight strength.
This is just a hobby, right?
Here is a shot of one of the stringers
Ron D. is adding one of the dozens of custom cut gussets for the framework. There are virtually no right angles on this thing, so every piece is cut to fit.
At the end of another day we fitted the nose section onto the wing box. It was starting to look like something. We are not sure what, but something. Something big. Something evil.....
The next day we completed the framing on the forward fuselage. Cutting all those stringers was getting old very fast. The rocket here is upside down as we are fitting the final forward stringers into place.
Starting to skin the nose section. This seemed an eternal task. There are over 30 separate panels, that have to be fit, glued and nailed into place. I have a new respect for those poor people that fit the heat tiles onto the space shuttle.
After we got going, things speeded up a lot. It took us four days to fully skin the nose.
As Dori from "Finding Nemo" would say.....
"Keep on skinning, Keep on skinning....." Getting punchy after 30 hours or so of fitting panels and gluing, then checking for straightness, having a drink, thinking things are straight. You know.....
Almost there.... Just 15 more sections..
It is starting to look like an X-Wing, or maybe the front of a top fuel dragster. Something.
Finally, the last piece of the front section. Once we close it up, the skins do their job and make the entire structure very rigid. We hope.
The whole nose section is done, except for the tip and canopy, and it is surprisingly light at only 40 pounds.
Here is a cool shot looking down the nose. The work on this was amazing to do. Our team is fortunate to have such great builders and engineers. Everyone that works on our projects contributes to the design and fabrication.
If you have not done a group project, I recommend it. It is so cool to talk through the procedures and get different ideas and solutions to problems.
Ok, starting to get a visual of the size of this thing. So are the neighbors. We hear doors bring locked, shades being drawn.......
We made the tip of the nose section out of a block of EPS. It is easy to cut with a hot wire, and also to shape with sandpaper. Here is the block with the root template drawn onto it. This is the shape of the forward bulkhead. It will be trimmed, then hollowed out to fit over the nose bulkhead, sanded to shape and glassed. It took surprisingly little time to do, just a few hours.
Here I am using a hot wire bow to trim the block to shape. We use wood guides and later wood templates to cut the shape. A simple variac is the power source. running through a .025 piece of carbon steel wire at 15V @ 5A.
With the tip roughed out, we hollowed it out a bit with a knife then pressed it onto the front of the fuselage. To everyone's surprise, it fit very well.
Once we got it straight, we used tite-bond to secure it.
Is it straight? Is it?
We got it pretty straight, and the following day Hulan M. did the carving with a belt sander and a block to the final shape.
We used 7oz satin weave cloth and laminating epoxy for the glassing. It came out very smooth. Dok H. from ROC joined us for today's festivities. We had a lot of fun today. Great progress and great company.
With the tip curing, we started on the canopy section. Since the rocket will have a seat for a child in it (no, not to launch, just for pictures. Stop that.) We needed to reinforce the canopy section and frame up the pilot's area. Hunal M., Dok H. and I got the aft section framed up in just a few hours. We will be installing the plexi-glass windows after it is painted.
The night shift got the front part of the canopy in place. Here we are holding the frame while the epoxy cures. There was no way to clamp the pieces, so we made lots of small talk while the glue cured.
Here is the progress at the end of the day. The canopy is just about done. It is really starting to look like a rocket.
With just three weeks to launch, we are starting to feel the pressure. The last two days the support has been great.
Ok, sorry for the long delay between updates. We can build or we can play on the computer... :-)
I wanted to ad a personal thanks to Gary and all the great people at RCS Aerotech for their support with this project.
The last few days have been finish work, painting mainly. We have a few things left to do, but here is what she looks like now....
Now off to the local park for some pictures. We didn't attract any attention on the road. None at all.....
I have been asked many times "You built that by yourself?". No, Not even close. Our rocket club, Tripoli San Diego, has a diverse membership with a wide range of skills and abilities. Almost everyone in the club participated. Here are just a few of the build team members.
I wanted to thank everyone involved, especially our sponsors RCS Aerotech and RMS Laser for their great support. Thanks also to all the people that took time to come over to my garage and put in all the long hours on this bird.
Some late additions to the project was to make R2D2 turn via radio control and we even added sound for him.
Flight date: 10/6/2007, Plaster City, CA
Down with the Empire!!!!!
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