SBIR-STTR Award

This Phase I SBIR proposal presents a very simple and practical approach to control the radiation from a surface. The method and prototype product developed as part of this Phase I proposal can replace louvers and provide improved performance with significantly reduced complexity and weight.The approach, which only works in a space environment and with a cold background, is based on the fact that the radiation from a high emissivity samples will be maximum when that surface is in intimate (good thermal) contact with a higher temperature surface, and is near or at that temperature. Alternately, when this thermal contact is missing, the radiation to a cold environment will lower its temperature and the radiation from this cover (which can be viewed as the total system emissivity) system will approach that of the lower emissivity, high temperature surface. Calculations indicate that an effective emissivity change from .05 to ~1 can be obtained when an electrostatic attraction is used to insure this intimate contact. Preliminary results of this system, using a thermal imager, indicate that the basic concept is viable, with measured changes in the apparent emissivity, from .38 to .95. Fabricating a practical coating requires detailed system design but does not require any technical breakthroughs.

Potential Commercial Applications:
A new and novel active control system will have multiple uses in temperature control of satellites an spacecraft. It is lightweight which will be a major advantage in space applications and will have very wide swing in emissivity, giving good thermal control. The approach also uses minimal power and is thus suited for all long mission time spacecraft/satellites.

This Phase II SBIR proposal will fabricate and deliver (for the ST-5 satellite) 4 space-qualified variable emissivity devices based on the ESR approach. This approach promises very low cost and high performance over competing technologies along with a very significant reduction in weight (~500 gm/sq. meter) In addition, during the Phase II, process improvement should result in a device with an electrically switchable emissivity range of .8. The approach works as a thermal switch, changing the mode of heat transfer from conduction (high heat loss) to radiation (low heat low). During the Phase I, heat loss measurements in a vacuum produced changes in effective emissivity as high as .74. The units to be fabricated for the Phase II will have more moderate performance to ensure high repeatability., but will still have changes in emissivity of .5. The ESR has low power consumption with very simple control electronics. Applying a high (200-500) volts turns it on producing a high e state; shorting it produces a low e state, with the device performing as a high quality capacitor (~ 400 pfd/cm2). The device is basically an off-on switch, but segmenting the area gives digital control on the emissivity to control temperature. POTENTIAL COMMERCIAL APPLICATIONS The ESR is a new and novel product. The only market for its application is for spacecraft that require switchable radiation for temperature control in applications where power and weight conservation are important. Technologies currently utilized for these applications (primarily mechanical louvers), are complex, cumbersome and expensive. Thus, the characteristic light weight and simple active control required of the ESR will be a significant advantage for space applications with tight requirements on temperature control.