Mars Atmosphere Carbon Dioxide Freezer (MACDOF)
The MACDOF project involves design and construction of a demonstration unit that will freeze carbon dioxide from the Martian atmosphere. The MACDOF is much less massive than a sorption pump sized for the same production rate and can significantly reduce the mass of the unit required to obtain carbon dioxide from the Martian atmosphere for ISRU processing. Joseph Trezathan was the JSC CTOR, and Robert Zubrin was the principal investigator at Pioneer Astronautics.
During the MACDOF project, Pioneer conducted a series of systems studies which showed a decisive advantage in CO2 acquisition system mass if a refrigerator was used in place of a passive sorption pump. We then built three prototype carbon dioxide freezers and successfully operated one of them in several different configurations. The freezers were sized to produce 700 grams of carbon dioxide per day. During a Mars mission using in situ resources, a spacecraft can use carbon dioxide frozen in the equipment demonstrated during this project to supply a fuel or oxygen production process.
While by no means demonstrating the full potential of refrigeration systems over sorption pumps, the data acquired in the Pioneer Astronautics refrigeration experiments nevertheless made a conclusive case. In operation, the refrigerator employed was able to demonstrate twice the daily CO2 acquisition capacity of a passive sorption pump massing 1.4 times as much. The freezer's mass advantage is understated, however, because it was built out of steel while the sorption pump was built out of aluminum. Had the same materials been employed in construction, the freezer mass would have been about a fourth of the sorption pump, while still outproducing it daily by a factor of 2.
The MACDOF Project was supported by SBIR Funding from NASA Johnson Space Center.