Feasibility Study of SSTO Programs Using Thermodynamic Properties

The purpose of this research is to study the feasibility of Liquid Air Cycle Engines (LACE) and Air Collection and Enrichment System (ACES) for single stage to orbit (SSTO) space programs. Various thermodynamic properties such as Joule-Thomson, Para-to-Ortho with hydrogen, and general heat exchanger performance are used to determine feasibility on a fundamental theoretical level. For LACE we examined the condensation ratio (CR) kg air condensed by kg H₂ coolant used, and examined how much variations in pressure, as well as para-orthohydrogen conversion would aid heat-exchanger efficiency. No matter what is done, we cannot achieve a desired CR that is close to the needed stoichiometric ratio of 34.4. For ACES we examined CR with and without precooling with excess N₂. Remarkably, precooling intake air with nitrogen worsens performance dramatically. The deficiency that causes ACES to be counterproductive is that, below 165 Kelvin, the proportional rise in the constant pressure heat capacity (Cp) of air is much greater than the proportional fall in the Cp of para-H₂. Additionally, masses of system components needed for precooling and heat-exchange would need to be carried to space on the vehicle thus, further reducing efficiency.