This NASA Phase I SBIR proposal seeks to demonstrate a new class of ultra-low-density (ULD) polymer matrix composites of high specific modulus and specific strength for mass sensitive space and aerospace applications. the "baseline" composite system for this program is state-of-the-art carbon fiber reinforced epoxy and/or bismaliimide. The key materials innovations are light-weight hollow carbon fibers in a light-weight porous (closed pores) polymer matrix. This innovation in composites technology would enable structural composites of lower density and higher specific modulus and strength than any currently available. If successful, this technology could have a profound impact and reduced payload weight and cost. Potential applications include planetary landers, satellites, large orbiting arrays and structures, booster motor cases. This program benefits from the support and participation of Lockheed Martin and Raytheon.