Brief:
Parachute-recovered core, two large gliders

Construction:
This twin uses the Space Shuttle foam gliders originally from Comet, but now distributed by Guillows. I replaced the thin (0.088") foam rudders with 3/16" balsa and the plastic insert used for rubber band launching with 1/8" dowel mounted to a 3/32" balsa spar. These dowels mate to a pair of 1" long 1/8" Estes launch lugs on the core, while the wings rest in a cradle made from 2" aileron material and 3/32" plywood "clips". The core is an 18" length of BT-60 with a standard 24 mm motor mount, and recovers on an 18" nylon parachute.

Needless to say, any serious software modeling of this bird was out of the question, though I did do some rough approximations. The gliders are amazingly light, massing right at one ounce, even with my mods. Still, she didn't have much margin, and was probably going to require some nose weight. I added an ounce of clay, but even with that, she's still less than six ounces dry, which means a three second delay is required. I did set up the motor mount so it can run the E11 reload, but its probably not a good motor for her. I thought Estes' new C11 might work too, but it only gets her to about 150 feet. I checked other motors, too, but this is pretty much a one-trick pony on the Estes D12-3.

I finished the core in Krylon Popsicle Orange (2410), followed by Testors Dull Coat (1260) to give the appearance of a stretched main (or should I now say "central") tank. I painted the gliders' rudders with Kilz white-pigmented spray sealer, and added the decals that came with the glider kits. In honor of the two Shuttles that no longer fly, I call one Enterprise (the stub-nosed one) and the other Challenger, though I haven't put their names on them yet.

Flight:
Her first flight was at Danville prior to paint, and she performed flawlessly. I didn't pay much attention to how I set her up, and put the wings parallel to the wind. As a result, she weathercocked quite a bit, but it didn't seem to hurt. The D12 ejected right after apogee, the gliders separated without a hitch and wobbled around in slow, lazy spirals. The core beat them to the ground by a good bit, as it should be. Her next flight was on a windier day, and she weathercocked pretty badly again. The gliders separated beautifully at ejection, just as before, but the strong winds kept them from gliding as well. They came down with the core, one inverted and one nose down. No damage, though, I'd just have to fly her were the winds aren't so bad. Her third flight was in slightly better winds, but she encountered some serious problems, nonetheless. She weathercocked and was going at the usual speed at ejection. The 'chute tangled on one of the wing cradles, and she recovered hard, breaking off one of the clips. The gliders faired no better, both landing on pavement, with Challenger sustaining a big dent on one side of her nose. Still, nothing that wasn't repairable, and I thought I'd keep her in the box until I had calmer conditions. I couldn't do it, though, and after repair I flew her on another windy day. This time I got her aligned properly and boost-out was relatively straight, i.e., no worse than any other that day. She snapped her shock cord, the body recovered ballistically, and the nose cone wound up about a 1/4 mile away, despite the nose weight. No damage to the core and the gliders flew and recovered fine, so a quick fix with some Rogue 300# Kevlar® put her back on the pad. After those repairs, she went in light winds.

My buddy's Flat Cat had just flown a spectacular glide, and I was afraid that the Twin Shuttle would disappoint when compared to it, but she surprised me by boosting straight and ejecting right at apogee. The center "tank" came down between the LCO table and the pads, and as everybody watched it come in, Enterprise banked in over their heads for a perfect touchdown feet from it. Challenger wound up about 75 yards away, but also had a perfect landing. Finally, success. As I carried the pieces back to my prep table, folks were telling me I should upscale it about three or four times. Ha! Her sixth effort was also in higher winds than I would have liked, but I put her on the pad with the rudders parallel to it and she flew pretty well. She even executed a little "roll program", turning the rudders perpendicular to the wind right after she left the rod, but then stabilized and flew straight thereafter. Ejection at apogee was at almost zero speed due to the small amount of weathercock. The pieces all drifted a good 150 yards, but landed within a few dozen feet of each other. When she flies right, this bird always impresses.

Summary:
Ever since I saw a pic of George Gassaway's twin boost glider in Sport Rocketry that utilized a pair of Turbo Jet 2000 two foot wingspan straight-wing foam gliders from Life-Like I've wanted to do one like it. This is a rather fitting tribute, as George is best known for his awesome Shuttle models. While she flies great, orientation on the pad is critical. These kinds of gliders are really designed for bungee launching and landing before terminal velocity is reached, so Flat Cats they ain't. A little more nose weight for them would help, as the upper pin is much lighter than the plastic insert it replaces. I don't like building rockets that only use one motor type, for that puts it at the mercy of a single manufacturer. Still, she was pretty easy to build, looks neat as heck, and with a little attention can perform wonderfully.