MODIFICATION OF NASA CET93 CODE FOR EVALUATION OF FISSION FRAGMENT HEATING PROPULSION CONCEPT

摘要

One of the most important ingredients of a manned mission to the planet Mars is a propulsion system minimizing the mission time compared with times of gravity assisted trajectories. C.Rubbia's Fission Fragment Heating (FFH) concept proposes to use as a "combustion chamber" of an advanced propulsive system, a "black body" radiator cavity with inner walls lined by a layer of ~(242m)Am (Americium isotope) kept critical by effective neutron "storing" in the cavity volume (n-hohlraum). The fission fragments can act as a high-energy source maintaining enthalpies of propellants much higher than those of chemical fuel combustion products. The standard NASA rocket performance code, CET93, is an unappropriate tool to theoretically evaluate the FFH system efficiency due to the lack of high-temperature plasma information in the data library. A new version of this code, CEA400, is a more appropriate tool for such an analysis, albeit it requires modifications as well. In this paper the propulsive efficiency (Isp) of hydrogen, helium, air, and Martian atmosphere propellants has been evaluated in the plenum pressure range 0.1 - 50 bars, and in the propellant plasma temperature range 3000 - 20000 K using a modified CET93 code. In all cases studied, the non-ideal plasma effects are proven to be considerable at high stagnation chamber temperature and low pressure.