Airborne Recovery of the X-61A Gremlin Unmanned Aircraft

The X-61A Gremlin is an autonomous unmanned aircraft designed and developed to demonstrate airborne launch and recovery. Airborne recovery of an unmanned aircraft is a complex operation involving multiple air vehicles and numerous unique engineering challenges. This paper describes the complex and interactive flight dynamics of airborne recovery using a physics-based simulation in comparison to flight test measurements to illustrate key principles. After a brief system overview, a 78 Degree-of-Freedom recovery simulation is described with emphasis on the challenging nature of modeling multiple flight vehicles in close proximity and the transition from free-flight to tethered-flight, which the X-61A demonstrated safely and successfully on October 29th, 2021. The demonstrated flight test results are in exceptional agreement with the simulation predictions, providing validation of modeling approach and demonstrating feasibility of airborne recovery.