The Lightspeed Rangefinder

Abstract

The Lightspeed Rangefinder is a novel application of a radio-based distance measuring system built from consumer components to the field of amateur rocketry. Using an arrangement where multiple ground stations communicate with a transponder attached to a flight vehicle, the vehicle’s altitude can be determined to within roughly 100 meters at altitudes of over 100 km. While each individual measurement is imprecise, the system runs at a high polling rate so averaging allows a more precise position to be produced from a large number of less precise points. This system has major implications for Rocket Propulsion Lab’s future operations, and we believe that it will allow the flight path of its vehicles to be tracked much more accurately and reliably than was ever possible before. Over the last year and a half, a team of engineers at the USC Rocket Propulsion Lab (led by Jamie Smith) conceptualized the rangefinder system, designed and built multiple iterations of PCBs, created embedded software to run the system, ran a bevy of qualification tests, and prototyped methods of analyzing the resultant points. While the first flight test of the system was inconclusive, long-distance ground tests of the rangefinder produced very promising results. This thesis will detail the process of design, iteration, and revision that led to the rangefinder system, as well as the theory by which it operates and how the data it produces is analyzed.