Issue link: https://www.e-digitaleditions.com/i/1520252
forming flight simulations, it was time to actually build a rocket. e upper stage nose used custom laser- cut centering rings to fit a BT-60 body tube into a BT-80 nose cone. Kevlar anchored to a centering ring served as the attachment point for the burn thread and metal BBs coated with epoxy provided nose weight. I built the booster with through-the- wall basswood fins suitable for tumble re- covery landing on the Utah desert floor. e booster of a two-stage rocket should have neutral static stability so it can tum- ble properly. I used the cardboard cutout method to calculate the CP and made sure the CG was located at the CP, with a used motor inserted. I had to use oversized fins to achieve a calculated descent rate of 6 m/s. To calcu- late the descent rate, I assumed the fins had a drag coefficient (C D ) of 1.3 and the body tube had a C D of 1.0. Painting and Finishing Using the method documented on the NAR website, I filled the basswood fin grain with wood filler. I selected a NO- VAAR orange and black paint scheme for the rocket, in honor of my old rocket club. Of course, I had to ruin a perfectly good paint scheme by throwing my NAR num- ber on the rocket, but I think it's a little too late for NOVAAR to disown me. Flight For once, one of my rockets worked correctly on the first attempt. Using a 3D printed launch lug, I launched the rocket from a 15mm aluminum guide rail point- ed straight up. e first stage went up with some reasonable weathercocking, and the second stage lit, sending the nose skyward until the rear ejected plastic parachute de- ployed. Figure 3 shows the flight sequence in graphic novel form. Future Improvements e rocket I designed and built worked just fine. However, a lot of nose weight combined with oversized fins was a recipe for a very statically stable first stage rocket susceptible to weathercocking. Without fins, the upper stage also had very little aerodynamic damping and if you watched carefully, it visibly "wobbled" during flight. Relatively late in the project I had the idea of incorporating electronic staging which would allow the booster to deploy a parachute and use smaller fins or even add a weight, making the first stage less stati- cally stable. I might incorporate this in fu- ture designs. Incidentally "relatively late in the proj- ect" by Against the Grain standards is typi- cally three months aer final submission deadline when I've nearly completed my first rough dra. Not much can be done to increase aero- dynamic damping of a flying nose. One possibility would be to add small fins, al- though upper stage nose cone purists will tell you this is uncouth. Conclusion It turns out you can build an upper stage nose cone. One way to do it is to use a burn thread to keep the rocket from drag sepa- rating, and to add a lot of nose weight. And it turns out I'm capable of building a rocket that does what it's supposed to do on the first attempt, so we'll call this one a success. References and Further Reading 1. Barrowman, J., Barrowman, J., e theoretical prediction of the center of pressure, National Association of Rocketry Annual Meet 8, 1966. 2. "NAR Certified Motors," retrieved from https://www.nar.org/ standards-and-testing-committee/ nar-certified-motors/. 3. "Filling Seams & Balsa," retrieved from https://www.nar.org/ educational-resources/model- rocket-building-techniques/ filling-seams-balsa/. 40 MAY/JUNE 2024 SPORT ROCKETRY https://thecreatorslaboratories.square.site/ Single-Board Computers! Arduino Inside! Write Your Own Code! Customize: Events, Lighting, Telemetry, Beeps and more! Log Data to an SD Card: Accelerometers Gyros Barometer NEW LIGHTING PRODUCTS! Engineering to Explore God's Creation! Designed and Assembled in the U.S.A!