NASA SBIR 2008 Solicitation


PROPOSAL NUMBER: 08-1 S3.04-8865
SUBTOPIC TITLE: Propulsion Systems
PROPOSAL TITLE: Light Metal Propellant Hall Thruster

SMALL BUSINESS CONCERN (Firm Name, Mail Address, City/State/Zip, Phone)
Busek Co., Inc.
11 Tech Circle
Natick, MA 01760 - 1023
(508) 655-5565

PRINCIPAL INVESTIGATOR/PROJECT MANAGER (Name, E-mail, Mail Address, City/State/Zip, Phone)
James J. Szabo
11 Tech Circle
Natick, MA 01760 - 1023
(508) 655-5565

Expected Technology Readiness Level (TRL) upon completion of contract: 4

TECHNICAL ABSTRACT (Limit 2000 characters, approximately 200 words)
Busek proposes to develop light metal Hall Effect thrusters that will help reduce the travel time, mass, and cost of SMD spacecraft. Busek has identified three attractive light metal propellants: magnesium (Mg), zinc (Zn), and a eutectic (Mg/Zn). These metals are plentiful and practical alternatives to Xe and Kr, which are expensive and scarce, and Bi, which is overly condensable and requires a high voltage power processing unit (PPU) to reach velocities of interest. Because Mg and Zn are lightweight, specific impulse > 3000 s will be available with a near term, low voltage PPU, decreasing propellant mass and program and hardware costs. Both metals have favorable ionization properties, implying high efficiencies are possible. Mg can also be combusted with water in a rocket, enabling a multi-mode propulsion system where the Hall thruster and rocket share propellant. The availability of a high thrust impulsive mode can greatly decrease delta V and trip times for SMD spacecraft.

These light metals are non-toxic and solid at room temperature. They can be stored and fed to a thruster as a wire. For Zn and Mg/Zn, liquid distribution is also feasible. Life testing will be low cost because the light metals are inexpensive and self pumping; they will condense on the vacuum chamber wall. Vapor pressure curves suggest minimal spacecraft interactions.

In-situ propellant production is also possible. Mg, for example, can be extracted from Martian regolith using solar energy.

The key innovation in this proposal is the use of light metals to fuel a Hall thruster. In Phase I, Busek will design and demonstrate a wire based light metal feed system that will be integrated with an existing 1-2 kW bismuth vapor Hall Effect thruster. Busek will then demonstrate a Mg, Zn, or Mg/Zn discharge and measure its operating parameters. Finally, Busek will lay out a dedicated thruster and feed system to be built and tested in Phase II.

POTENTIAL NASA COMMERCIAL APPLICATIONS (Limit 1500 characters, approximately 150 words)
Light metal vapor may be a better propellant option for high power missions than Xe, Kr, or Bi. Both Mg and Zn are non-toxic, condensable, plentiful, and inexpensive, and easy to ionize. Because these metals have favorable vapor pressure curves, high temperatures are not required to avoid condensation inside the thruster, and spacecraft interactions will be minimal by comparison with Bi.

Because both metals are much lighter than Xe, high specific impulse will be available from low voltage PPUs. This makes the technology well suited for high Delta V SMD missions. Examples include exploration missions to asteroids, comets, and other small bodies, as well as outer planets. Sample return missions are also enabled.

Light metal Hall thrusters can also accomplish valuable missions to the moon and mars. One possibility is the deployment of multiple robotic spacecraft into lunar orbit form Busek's ESPA orbit maneuvering system, (OMS). A high power cluster would even support for manned missions. Transport of fuel and cargo to the Moon and Mars is possible.

In-situ propellant utilization is a distinct possibility. Earth return missions from Mars could be fueled by Mg present in Martian regolith.
A high power system could be extensively ground tested, greatly reducing risk. Such a test is affordable because Mg and Zn will condense on water-cooled panels.

POTENTIAL NON-NASA COMMERCIAL APPLICATIONS (Limit 1500 characters, approximately 150 words)
Light metal Hall thruster technology may enhance many critical DoD and commercial missions such as satellite orbit raising and repositioning. Zinc and magnesium offer performance similar to xenon with the possibility of long term, low maintenance, solid propellant storage. If a wire feed system proves practical, no tankage is required. Spacecraft interaction issues should be minimal by comparison with bismuth.
Mg and Zn Hall thrusters could be integrated with Busek's EELV Secondary Payload Adapter (ESPA) Orbit Maneuvering System, which presently carries a multi-mode propulsion system based upon hydrazine and xenon. A Mg or Mg/Zn Hall thruster could be paired with a Mg-water rocket to provide both high thrust and high Isp. The two systems would share propellant feed system components, tanks, and fuel.

Light metal thrusters also have terrestrial applications. A zinc plasma thruster can be used for zinc plasma spraying. Zinc is an extremely common metal coating. Zinc spraying is normally accomplished by feeding zinc in wire or powder form into a heated gun, where it is melted and sprayed on to the part to be coated using combustion gases and/or auxiliary compressed air.

NASA's technology taxonomy has been developed by the SBIR-STTR program to disseminate awareness of proposed and awarded R/R&D in the agency. It is a listing of over 100 technologies, sorted into broad categories, of interest to NASA.

Electrostatic Thrusters
Feed System Components
In-situ Resource Utilization
Propellant Storage

Form Generated on 11-24-08 11:56