Vincent C. Nardone

Metal/ceramic composite heat pipes for a low‐mass, intrinsically‐hard 875 K radiator

Thermacore, Inc. of Lancaster, Pennsylvania has recently completed Phase I of a development program to investigate the use of layered metal/ceramic composites in the design of low‐mass hardened radiators for space heat rejection systems. This effort evaluated the use of layered composites as a material to form thin‐walled, vacuum leaktight heat pipes. The heat pipes would be incorporated into a large heat pipe radiator for waste heat rejection from a space nuclear power source. This approach forms an attractive alternative to carbon/carbon, or silicon‐carbide fiber reinforced metal heat pipes by offering a combination of low mass and improved fabricability. Thermacore and United Technologies Research Center have jointly developed an approach for fabrication of layered composite thin‐walled heat pipes for use in hardened space radiators. Potassium heat pipes with wall thicknesses as low a 0.3 mm have been built and tested. Wall thicknesses as low as 0.13 mm are believed to be achievable with this approach.

Metal/ceramic niobium composite fin heat pipes for a low mass radiator

Niobium/alumina composite materials show promise for providing low mass fin heat pipes for space heat rejection systems. These heat pipes would be incorporated into a large radiator for waste heat rejection from a space nuclear power source. Current fabrication technology limits the heat pipes to straight lengths, although different cross‐sections can be fabricated. A radiator analytical model was developed and used to examine the effects of fin pipe cross‐section and fin material on radiator mass. Carbon‐Carbon, Compglas, and beryllia fins were examined. The overall radiator mass was only slightly affected by the choice of material, however, the carbon‐carbon design required fewer fin heat pipes. Radiators with carbon‐glass composite (Compglas) fins had a slightly higher mass, but may still be attractive based on the other properties of Compglas, including resistance to atomic oxygen, and the ability to be fabricated into thin sheets. Square Nb/Alumina tubes have already been fabricated, while rectangular niobium composite tube is under development. These tubes will be bonded to carbon‐carbon or Compglas fins, and fabricated into sodium heat pipes.Niobium/alumina composite materials show promise for providing low mass fin heat pipes for space heat rejection systems. These heat pipes would be incorporated into a large radiator for waste heat rejection from a space nuclear power source. Current fabrication technology limits the heat pipes to straight lengths, although different cross‐sections can be fabricated. A radiator analytical model was developed and used to examine the effects of fin pipe cross‐section and fin material on radiator mass. Carbon‐Carbon, Compglas, and beryllia fins were examined. The overall radiator mass was only slightly affected by the choice of material, however, the carbon‐carbon design required fewer fin heat pipes. Radiators with carbon‐glass composite (Compglas) fins had a slightly higher mass, but may still be attractive based on the other properties of Compglas, including resistance to atomic oxygen, and the ability to be fabricated into thin sheets. Square Nb/Alumina tubes have already been fabricated, while rectangula...