The Estes Converter was an almost-ready-to-fly (ARTF) offered by the Big E from 2007 to 2009. It featured a plastic fin unit and 4 BT-56 body tube segments with screw type couplers, enabling the owner to vary the rocket's length from 24 to 40 inches. I am one of these owners, and the sight of it a few days ago got me wondering if one could design and build a TARC rocket that could reach the three altitude marks simply by screwing on different lengths of body tube. After pondering the matter for a couple of days, I decided to look into the concept further.
|Estes Converter (Click to enlarge).||A shorter Converter|
(Click to enlarge).
The first step was to determine if similar screw-type couplers could be had from the rocket vendors. Such things could probably be 3D printed, but I don't have easy access to this technology, so I need to be able to purchase them from somewhere. Fortunately eRockets offers them in various diameters, including BT-70. This obstacle now eliminated, I fired up Open Rocket and set to work.
|eRocket's BT-70 screw type coupler (Click to enlarge).|
|The Bullpup 1(Click to enlarge).|
|Open Rocket simulations in order of decreasing altitude (Click to enlarge).|