The goal of the project is the thermal reduction of samples of lunar regolith simulant as a possible technique for producing oxygen by pyrolysis on a lunar base. The extraterrestrial production of oxygen is a key technology for a lunar base or manned missions to near-Earth asteroids or Mars. The solar heated vacuum pyrolysis has some important advantages, because it is based upon the realities of the lunar environment. As a tool for investigating the basic reactions and the technology the DLR High Flux Solar Furnace was used. This facility is operated since 1994 in Cologne. It delivers concentrated solar radiation up to a peak flux of 5 MW/m2. This power can be used to cause thermal or photochemical effects in irradiated materials. For the astrophysical and mineralogical applications discussed here, a vacuum chamber with a solar-adapted design and new instrumentation was developed. The pyrolysis experiments were conducted under high vacuum. Using the concentrated beam of the solar furnace as heat source, the lunar soil simulant samples achieved liquid phase in 10 - 20 seconds and reached temperatures between 1500 to 1900 K, were the relevant processes took place. The heating phase was followed by a controlled cooling. The partial pressure of oxygen and several other constituents in the vapour phase was measured with a differentially pumped quadrupole mass spectrometer. The temperatures of the samples were measured by an IR camera with a special optical system. Baseline experiments with different reference metal oxides like SiO2, CaO, and ZnO were made to verify the apparatus and investigate background contamination. The data of the five experiments with regolith showed typical features and a similar behaviour of gas partial pressure depending on temperature level, with an increase of oxygen during the strongest irradiation. The detected oxygen originates from thermal decomposition of the mineral sample and caused a large numbers of gas bubbles inside the melt. Mineralogical analyses of the exposed samples revealed a depletion of oxygen and volatile elements (Na, K, P). In conclusion the thermal decomposition of lunar soil by intense solar light is feasible and it is reasonable to take the next step in investigating the more technological problems of a process leading to oxygen production from extraterrestrial resources.
35th COSPAR Scientific Assembly
- Pub Date: