2012.C.1.1 Ion Drive Interplanetary CubeSat

Author(s)

Carl Brandon (1)

Vermont Technical College

Session

C.1 – Propulsion Issues for Interplanetary Cubesat Missions

Keywords

ion, xenon, Mars, Moon, carbon fiber

Abstract

A triple unit ion drive CubeSat spacecraft suitable for Lunar or interplanetary travel is being developed at Vermont Technical College with The University of Vermont and Norwich University, through a NASA Consortium Development Grant. The structural elements will be of carbon fiber composite. There will be a 1 kg scientific instrument payload. It is based on the Lunar SMART-1 spacecraft of the European Space Agency (ESA). Our design will use the CubeSat-sized NASA-JPL developed miniature xenon ion thruster MiXI with a thrust of 1.5 mN and a specific impulse of 2,500 – 3,200 seconds. With this thruster, a 0.75 kg propellant load of 300 atmosphere xenon would give a Δv of about 3,500 – 4,500 m/s. 50W of power of for the thruster will come from photovoltaic cells on the spacecraft and four fold out double length panels. The control software for the mission is being written in Ada / SPARK which has a record of producing very reliable software, with about 1% the error rate of C.

A low energy trajectory provides a transfer to the Moon from a geostationary transfer ellipse through a Lissajous orbit at the Earth-Moon L1 Lagrange point. This strategy takes advantage of the complex dynamical behavior of the trajectory near the L1 point, and from a Lissajous obit about L1 it is possible to access various lunar and planetary orbital planes with different inclinations and ascending nodes using a minimal Δv. The second type of indirect trajectory is of the type used by the ESA SMART-1 mission in 2003. The spacecraft is first put into a geostationary transfer ellipse. It then elongates its Earth elliptical orbit and utilizes lunar resonance maneuvers to minimize propellant use. A final continuous thrust maneuver can be used to perform a lunar orbit capture at a distance of about 60,000 km from the lunar surface or to initiate a Hohmann transfer to Mars . For these transfers, there will be great demands on spacecraft navigation.

Navigation is by a NovAtel OEMV-1 GPS, with CoCom limits removed, and a star tracker camera. We will use the NASA Goddard developed GPS Enhanced Onboard Navigation System (GEONS) software rewritten in Ada / SPARK. GEONS will analyze both the GPS signal and the celestial information from the star tracker camera. We have been selected for a NASA launched ELaNa IV mission for a single CubeSat which will test this navigation system in orbit in 2013.