In-situ Propellant Production and ERV Propulsion System Preliminary Design Review 2/6/01 Adam Butt

In-situ Propellant Production Propellants selected to be produced Reasons for the selection Method of production to be used Risk Analysis

Selections and Criteria Methane Advantages CH4/LOX reaction capable of Isp~365s Relatively efficient and cost effective to make Disadvantages Must be cryogenically stored Requires 3.5 times as much O2 for optimal reaction Methanol Advantages Does not require cryogenic storage Higher density  smaller tanks Requires only 1.5 times as much O2 Disadvantages CH3OH/LOX reaction Isp~340

Method of Production Methane LOX Methanol Sabatier Reactor Water Electrolysis Zirconia Cell process Methanol 2C0+3H2CH3OH+2H2O Methane derived methanol More in-depth study needed

ERV Propulsion System Consists of two stages Lower stage of Methanol/LOX Utilizes methanol’s higher density and lower mixture ratio to achieve an overall smaller and lighter system than just methane/LOX (Zubrin) Upper stage of Methane/LOX Utilizing this reaction’s increased performance to provide final impulsive DV to the smaller upper stage

Staging Comparison Two stages – both Methane/LOX Assumptions: DV=5.7km/s, mpayload=33tonnes, neglect drag/gravity loss Two stages – both Methane/LOX Total mass=190tonnes Vol of CH4=65m3 Vol of LOX=96m3 Two stages – 1st Methanol/LOX, 2nd Methane/LOX Total mass=185tonnes Vol of CH3OH=70m3 Vol of LOX=74m3

Power Requirements Based on the following equation, Pe = [0.145(MT)1.238] kW And on the ~115kW power production of the nuclear reactor It will take around 800 days to produce all the necessary propellant. Therefore as the HAB departs Earth 2 years after the ERV, around 90% of the propellant will have been produced.

Basic Risk Assesment The main back up will be the 2nd ERV/in-situ plant arriving around the same time as the astronauts In-situ plant Zirconia cell process involves the use of large brittle cells – Cannot withstand high g-loading, additional replacement cells need to be brought. Sabatier reactor comprised of simple, rugged steel pipes ERV Launch System – The more stages the more complexity, the greater the risk

Future Work Research Methanol production in greater depth Size in-situ production plant Further asses possible failure modes, and determine necessary redundancy plans