Type

Dragstar is a cluster design inspired by a conversation I had with another CRASH member named Gary. He was showing me his LOC Viper-IV cluster rockets (he has three of them!) and said he wanted to try a drag race with another 4x24mm rocket. Since I am completing the NARTREK training program and needed to build a cluster anyways, I accepted Gary's challenge on the spot. But, to me, a drag race involves four wheels and nitro-methanol. Hmmm, I wonder ...

	Dragstar is a 3x18mm cluster rocket meant to resemble a top-fuel rail dragster and has round fins (slicks), a cockpit, and a "tubular" (spruce dowel) front end with tires on the nosesection. (Click on image for full size picture. Use "BACK" button to return.)
	To keep the overall length and fin sizes small enough to even resemble a dragster, there's 3 ounces of lead fishing weight in the tapered nosesection. The tubular framed front section of this rocket is NOT something you would want coming in ballistic after a shock cord separation or shred. (Click on image for full size picture. Use "BACK" button to return.)

Notes

The rocket was simulated in Rocksim by using BT-5 as the forward section and it showed almost 2-caliber stability with three B6-4 motors and a .75 ounce weight in the nose, but it FLEW BACKWARDS in a swing test. Using a simulated BT-20 front section also showed stable. Another .75 ounce sinker showed over 4 caliber stability in Rocksim, but the model still flew in reverse. A third fishing weight caused the Dragstar to turn around and fly forward when swung.

A swing test on a relatively short tether gives an overly conservative indication of stability. In fact, a rocket can swing backwards and still fly in a stable manner. The reason for this has to do with the circumference of the swing circle and the length of the rocket. If the rocket length is a substantial percentage of the circumference of the swing circle, the rocket is not "flying" in a low angle of attack manner as it would during a normal launch (the nose is outside the swing circle radius, as is the tail). A good swing test is a good indicator of stability, but the opposite is not necessarily true; a bad swing test does not mean an unstable rocket.

Since this is a new design and construction method for me, I opted to make sure the model would swing test even though Rocksim showed several calibers of over-stability. After some good flights, I'll start taking weight out of the nose and see how she does.