Propulsion Electronics Get Smaller

by Joe Singleton/jsingleton@nttc.edu

Electronics used for commercial satellite propulsion systems may soon become smaller and less expensive with the help of MDA-funded research.


The technology, developed by Space Micro Inc. (San Diego, CA), involves the miniaturization and radiation hardening of electronics through a novel means of stacking commercial-off-the-shelf semiconductor materials.
MDA funded Space Micro through a 2007 SBIR Phase II contract to develop an electronics module for interceptor divert attitude and control systems (DACS) that meet radiation-hardness requirements.

Space Micro’s technology focuses on the electronic circuitry used in a DACS module to control thrusters to propel a missile or satellite into position to acquire a target. In either a missile or satellite, minimal space is available for placement of electronics, making miniaturization of such components essential.

Company engineers begin the process of designing DACS electronic modules by procuring commercially available circuitry components, specifically those that can be acquired in die form. Materials in die form are preferred because they generally are about one-fifth the size and weight of manufactured components. These semiconductor die are three-dimensionally stacked, which reduces the circuitry footprint currently found in conventional modules. Stacking enables many circuits to be fitted in an area of 0.5 square inches, over 50 times smaller than the space requirements of other commercially available modules. Effectively a circuit board about the size of the MDA TechUpdate newsletter can be compressed into a board smaller than a quarter. After the components are stacked, Space Micro then hermetically seals the stacked module in a radiation-hardened alloy made of high-density materials.

While other competitors occasionally design products that use stacking to conserve space, Space Micro’s product is designed for space-borne computer applications, namely memory chips used on high-power space platforms or technologies. One particular DACS module chip, known as a power MOSFET—a metal oxide semiconductor field-effect transistor used to handle large amounts of power—produces about 8 amperes of power for controlling the thrusters of a missile or satellite.

Cost savings are another advantage. The biggest savings is through the use of commercial off-the-shelf processes and materials. Generally, these materials are less expensive than custom solutions, which means end users ultimately can enjoy a lower price. For example, a power MOSFET costs around $450 from major suppliers, if radiation hardened. But a non-rad-hard power MOSFET can be procured for around $10. As six power MOSFETs are needed for a DACS module, the company pays $60 and packages it with a proprietary blend of high-density, radiation-shielding materials. By doing the work in-house, Space Micro President and CEO David Strobel says his company’s overall cost can be significantly reduced for its customers.

While the technology is designed primarily for military satellites and missiles, Strobel said Space Micro’s DACS modules could be used on commercial satellites. The closest commercial application on the ground may involve opening valves at nuclear power plants, which Strobel considers to be a stretch since miniaturization is not critical.
Space Micro intends to continue developing this technology in the near term—which stands at Technical Readiness Level 5—while growing the company. Partnering, and possibly merging, with larger companies that can use Space Micro’s technology is being pursued.