Technical Sessions

Session II: Liquid to Gas

Chair: Aaron Rogers – Johns Hopkins University Applied Physics Laboratory

Monday, August 10, 2009

4:30 p.m. CubeSat Propulsion Using Electrospray Thrusters

Tom Roy, Vlad Hruby, Nathan Rosenblad, Peter Rostler and Douglas Spence – Busek Co. Inc.

ABSTRACT: The space industry is showing increasing interest in small, low‐cost CubeSats which can serve a variety of missions. Busek Co, Inc is developing a small TOAC (thruster‐on‐a‐card) that is designed to provide both primary and ACS propulsion within a 1U CubeSat volume. Electrospray thrusters operate by electrostatically accelerating charged droplets of an electrically conductive ionic liquid, and are capable of providing a high degree of throttling and variable Isp. The electrospray thruster, propellant reservoir and power processing unit and digital control interface unit (DCIU) occupy less than 1U and will provide over 350m/s delta‐v for a 1kg CubeSat. The propulsion system presented here has a target thrust of 75µN, is designed to operate on a specific impulse of 800‐1600s and a nominal power consumption of 2.5W. This propulsion system can be used to enable formation flying, pointing and orbit maintenance applications for CubeSats. This device has grown from AFRL and NASA development heritage, including Busek’s recent delivery of 8 flight electrospray thrusters to Space Technology 7 Disturbance Reduction System (ST7‐DRS) technology demonstration mission, sponsored by NASA’s New Millennium Program and managed by JPL, slated to fly in 2011. This paper describes the electrospray thruster system and its capability.

4:45 p.m. Expanding the ADN‐Based Monopropellant Thruster Family

K. Anflo – ECAPS; S. Moore – ATK, Tactical Propulsion & Controls; P. King – Moog Inc.

ABSTRACT: The development of High Performance Green Propulsion (HPGP) was initiated with the goal of meeting the requirements for future satellite missions. The HPGP technology includes a storable monopropellant blend based on Ammonium DiNitramide (ADN) and a thruster with a high‐temperature resistant thrust chamber and catalyst. After more than 10 years of R&D, the HPGP technology is emerging as an enabling technology for improved performance, enhanced volumetric efficiency, reduction of propellant handling hazards and safer launch operations. The development has been performed by ECAPS under contract from the Swedish Space Corporation, the Swedish National Space Board and the European Space Agency (ESA). The progress of the development has been presented in several papers since 2000. Ref. 1‐11. ECAPS, ATK and Moog are in partnership to pursue new applications for this novel technology.

This paper describes current status of the implementation of HPGP technology for satellite programs and the latest results from the development of larger HPGP thrusters.

5:00 p.m. Micro RF Ion Engine for Small Satellite Applications

Michael Tsay, Kurt Hohman, Lynn Olson – Busek Co., Inc.

ABSTRACT: A xenon‐fueled, micro rf ion engine suitable for small satellite propulsion was developed by Busek. Operating with a pair of grids that are 3 cm in diameter, the thruster demonstrates 1.4‐2.1 mN thrust and 1500‐2850 seconds Isp. Total power consumption ranges from 60 to 100 W. At the optimum Isp of 2500 seconds, the estimated thrust efficiency and propellant utilization is 49% and 47%, respectively. Total efficiency, including 90% dc‐to‐rf conversion, is estimated at 21%. The total efficiency can potentially be increased up to 27% by reducing rf coupling loss. Busek is dedicated to further miniaturize rf ion engines with the development of a 1‐cm thruster equipped with a propellant‐less carbon nanotube field emission neutralizer. Projected performance of the 1‐cm micro rf ion engine is 0.15 mN thrust, 1570 seconds Isp and 14 W total power consumption.

5:15 p.m. Monopropellant Micro Propulsion System for CubeSats

Chris Biddy, Tomas Svitek – Stellar Exploration

ABSTRACT: Stellar Exploration Inc. has developed a high performance Hydrazine Monopropellant Micro Propulsion system for use with CubeSats with focus on manufacturability and affordability. The 1kg micropropulsion system will be coupled to one or two additional 1kg CubeSat units making an overall 2‐3kg two or three unit CubeSat system compatible with California Polytechnic State University’s P‐POD deployment system. The micro propulsion system includes four 1.5 Newton thrusters arranged appropriately to control roll, pitch, yaw and axial translation. The monopropellant micropropulsion system required many innovations in order to miniaturize it to meet the geometric and mass requirements of CubeSats. These innovations include the use of specially designed catalysts, micro solenoid thruster valves and micro machined combustion chamber and nozzle. This paper outlines the decision processes involved in choosing the type and configuration of the micro prolusion system as well as a detailed description of the innovations leading to a functional system. Future improvements and lessons learned from development will also be discussed and concluded with the micro propulsion test results.