Grad student receives prestigious NASA fellowship

Oct 30, 2017

By UCLA Samueli Newsroom

Stephen Samples, an aerospace engineering doctoral student advised by Professor Richard Wirz, has been awarded a NASA Space Technology Research Fellowship (NSTRF), to investigate and develop a miniature ion thruster for in-space propulsion.

This prestigious NASA fellowship includes an annual stipend, with additional funding support to cover tuition, fees and other expenses. The fellowship also includes ten weeks conducting research at a NASA facility.

Ion thrusters use electric power to generate thrust. They operate by first ionizing a xenon gas propellant, and then use electrostatic acceleration to expel these ions at over 40 kilometers per second. As a result, ion thrusters are very fuel efficient compared to conventional chemical propulsion. This high fuel efficiency allows ion thrusters to perform missions with significantly less propellant, and therefore less launch mass.

Current full-sized ion thrusters are about 30 centimeters in diameter and require over 2,000 Watts of electric power. The UCLA-led DAWN mission to the protoplanets Vesta and Ceres in the Asteroid Belt used three such ion thrusters, and cost nearly $500 million. To reduce costs on future missions, NASA wants to develop miniature ion thrusters with similar efficiencies for smaller, more affordable spacecraft.

Samples’ research goal is to develop a miniature ion thruster that is only 3 centimeters in diameter and only needs 20 Watts of electric power to operate. At these lower power levels, the advantages of ion thrusters can be realized for small spacecraft, even down to the size of a 3U CubeSat (which measures 10cm by 10cm by 30cm).

During the four-year fellowship, Samples will focus on the physics and engineering of efficiently confining the discharge plasma inside the thruster by advancing and employing new approaches to magnetically-confined miniature plasmas (ionized gas). He will also develop high-efficiency miniature cathodes for the thruster system. These provide the electrons to produce the thruster’s discharge plasma.

Samples, a member of Wirz’ Plasma & Space Propulsion Laboratory, joined UCLA in 2015. He received his bachelor’s degree in aerospace engineering from Auburn University.

Samples is the second student advised by Wirz to receive this honor. In 2013, his former doctoral student Ryan Conversano was awarded the fellowship for space propulsion research. Conversano is now an electric propulsion technologist at NASA’s Jet Propulsion Laboratory.

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