Validation of a unique concept for a low-cost, lightweight space-deployable antenna structure

Abstract Large space-deployable antennas are needed for a variety of applications that include mobile communications, radiometry, active microwave sensing, very-long-baseline interferometry, DoD space-based radar and microspacecraft. Investigators in these fields identify the need for structures up to tens of meters in size for operation from 1 to 90 GHz, based on different aperture configurations. The selection criteria common to all of the users are low cost, lightweight, high reliability and good reflector surface precision. Fortunately, a unique class of space structures has recently emerged that offers great potential for satisfying these criteria. They are referred to as inflatable deployable structures. A good example of such a concept is under development at L'Garde Inc. Serious interest from the user community will depend on realistic demonstrations of the viability of the concept. This means that large, lightweight, low-cost structures need to be developed and used to demonstrate deployment reliability in realistic service environments. The technology data base for the L'Garde inflatable concept will accommodate the development of reflector antenna structures up to 30 m in diameter. Since the concept utilizes very low inflation pressure to maintain the required geometry on orbit, gravity-induced deflection of the structure precludes any meaningful ground-based demonstrations of functional performance. Therefore this concept has been selected for a NASA In-Space Technology Experiment Program (IN-STEP) space-based experiment. The objectives of this experiment are to validate and characterize the mechanical functional performance of a 14-m-diameter inflatable deployable reflector antenna structure in the orbital operational environment. The experiment will be carried by the NASA Spartan spacecraft, which is launched, deployed and recovered by the STS. The Spartan will provide mounting, attitude control, power and data recording for the antenna experiment. The antenna concept development will benefit from both the experiment and supporting technology developments. Results of this experiment are expected to verify the feasibility of fabricating a large space structure for only a few million dollars, demonstrate the reliability of deployment, characterize the quality of the reflector surface and correlate the analytical performance prediction models with actual measured characteristics. Technology developments in support of the experiment, to be conducted at NASA Langley Research Center and the University of Colorado, will include investigation of new and advanced flexible materials, as well as system studies to assess the adequacy of this structural concept for specific classes of applications and for the development of analytical performance production tools. These combined results will be used to advance the technology of the concept with respect to improving surface precision and performance predictability and accommodating larger size structures with different configurations in different orbits.