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Spacecraft hardware trade studies compare options primarily on mass while considering impacts to cost, risk, and schedule. Historically, other factors have been considered in these studies, such as reliability, technology readiness level (TRL), volume and crew time. In most cases, past trades compared two or more technologies across functional and TRL boundaries, which is an uneven comparison of the technologies. For example, low TRL technologies with low mass were traded directly against flight-proven hardware without consideration for requirements and the derived architecture. To provide for even comparisons of spacecraft hardware, trades need to consider functionality, mission constraints, integer vs. real number of flight hardware units, and mass growth allowances by TRL.

In the Sabatier reactor, oxygen is recovered (as water) by hydrogenation of carbon dioxide. One half of the reacted hydrogen is contained within the product water, the other half is used to form methane (CH4). Hydrogen resupply requirements for the oxygen recovery process can be minimized by reclamation of hydrogen from the methane waste. To this end, we have developed effective methods for the recovery of hydrogen from CH4 using a microwave plasma reactor. By selectively promoting the oligomerization reaction which forms hydrogen and acetylene, up to 75% of the waste hydrogen can be recovered in a manner which minimizes the carbon fouling and carbon build-up problems which drastically reduce the long-term viability of traditional methane pyrolysis methods using fixed bed and fluidized bed reactors.

The baseline environmental control and life support (ECLS) systems currently deployed on board the International Space Station (ISS) and that planned to be launched in Node 3 are based upon technologies selected in the early 1990's. While they are generally meeting or exceeding requirements for supporting the ISS crew, lessons learned from years of on orbit and ground testing, together with new advances in technology state of the art, and the unique requirements for future manned missions prompt consideration of the next logical step to enhance these systems to increase performance, robustness, and reliability, and reduce on-orbit and logistical resource requirements. This paper discusses the current state of the art in ISS ECLS system technologies, and identifies possible areas for enhancement and improvement.

In the Sabatier reactor, oxygen is recovered (as water) by hydrogenation of carbon dioxide. Half of the reacted hydrogen is contained within the product water, the other half forms methane (CH4). To close the hydrogen loop, we are investigating methods for the efficient recovery of hydrogen from CH4. This paper describes microwave plasma-based methods for the thermal decomposition (cracking) of methane to produce hydrogen, elemental carbon, and related carbonaceous substances. Two primary reactor configurations have been employed in this work: 1) a quartz tube vertically oriented within a section of rectangular waveguide, and 2) waveguide transmission through a quartz window into a cylindrical vacuum chamber based multimode cavity. Hydrogen recoveries of up to 98% have been obtained. Three primary mechanisms of methane decomposition have been identified: methane pyrolysis, methane oligomerization, and methane aromatization.