Analysis of Miniature Payloads Launched from an Airborne Gun Launch Platform

摘要

Several launch methods have been proposed to economically deliver small payloads (~10 kg) into low Earth orbit at a high launch rate including gun launch concepts using electromagnetic and light gas guns. The traverse through the atmosphere subjects the launch vehicle to high aerodynamic heating loads, requiring the launch vehicle to incorporate a thermal protection system if the payload is to survive atmospheric transit. Additionally, small rocket motors are required to insert the payload into low Earth orbit. The objective of this effort is to apply the Advanced Ballistic Reentry System Shape Change Code to study ballistic and lifting trajectories of a nominal 10 kg launch package launched from a 16 km airborne platform using sphere-cone and elliptical aeroshells. The computer code was modified to incorporate lift and drag coefficients numerically computed using the modified Newtonian method and approximate quadrature to extend the capability of the code to compute lifting trajectories and ablation of elliptical aeroshells. In the first part of the study, total ablated mass and internal temperature distribution of the aeroshell for ballistic trajectories are quantified, assuming both laminar and turbulent flow, over a range of launch parameters relevant to gun launch. Total thermal protection system and propellant mass needed for orbital circularization are computed to serve as a baseline for the lifting trajectories. The second part of the study focuses on computing trajectories without ablation to quantify the reduction in propellant mass that can be obtained by employing aerodynamic lift. Optimal trajectories are sought that minimize total parasitic mass for 200 km orbital insertion. Results indicate that thermal heating is manageable with a passive thermal protection system and that lifting trajectories reduce propellant mass requirements over ballistic trajectories.