Phase II Final Report - NASA's Institute for Advanced Concepts

Chapter 3.0 Vehicle Design
3.5 Fuel Storage and Production
Figure 3-160: Hydrogen Gas Storage System
3.5.3.3 Sorption Compressor
To produce O 2 from the atmosphere, a sorption compressor can be used to separate the CO 2
from the atmosphere and increase its pressure so that it can be used in the zirconia process
described previously. A sorption compressor contains virtually no moving parts and achieves its
compression by alternately cooling and heating a sorbent bed comprised of materials that absorb
low pressure gas at low temperatures and desorb high pressure gas at higher temperatures. The
characteristics of the material in the sorption pump define how much gas can be absorbed and
which species are more readily absorbed than others. Due to the lack of rotating/moving parts, it
has significant potential for long lifetime, reliability, and robustness. Like the zirconia oxygen
generator, a sorption compressor was also scheduled to be part of the Mars in suit propellantprocessing
experiment for the Mars 2001 Surveyor lander. [138].
The sorption material, a zeolite, can adsorb approximately 135 mg/g of material at Mars atmospheric
conditions (6 Torr, 200°K). The mass of oxygen produced from the CO 2 is approximately
one-third the mass of the CO 2 collected. The amount of energy (E, in Jules) needed to
raise the temperature from the initial 200° K to 450° K, where the CO 2 is released at higher pressure,
is given by the following equation: where c p is 1,010 [J/kg °K] for the sorption material, m
is the mass in kilograms of the sorption material used and ∆T is the change in temperature in
degrees Kelvin [139]:
199