Combined Heat Shield and Solar Thermal Propulsion System for an Oberth Maneuver

Abstract

A powered gravity assist around the sun, also known as an Oberth maneuver, has the potential to achieve a solar system escape velocity of 20 astronomical units (AUs) per year, which is desirable for an interstellar mission. Unfortunately, current heat shields and propulsion technology struggle to outperform an unpowered Jupiter gravity assist, let alone 20 AUs/year, due to unfavorable mass tradeoffs. We are therefore developing an unconventional approach that simultaneously addresses the need for high specific impulse and close proximity to the sun: convert the heat of the sun into usable thrust by passing a propellant through the heat shield. To demonstrate the concept of a combined heat shield and solar thermal propulsion system, we designed and fabricated a prototype and exposed it to a 20-sun solar simulator. The reflective yttria-stabilized zirconia coating and helium gas flow maintained a temperature of 339 K. With a dark chrome oxide coating facing the simulator, it generated 1.3 N of thrust at a flow rate of and a temperature of 516 K. The agreement between theory and the experiment suggests that an escape velocity of 15 AUs/year is attainable at a mass ratio of two and a perihelion of 2.5 solar radii.