June 3, 2008 Slide 1 Lunar/Mars Surface Power Architecture Analysis Follow-up Chase Cooper August 7, 2008

June 3, 2008 Slide 2 Areas of Revision l Regenerative fuel cell performance: n Original Energy density: w~700 Wh/kg n Revised Energy Density: w~250 Wh/kg l Wind considerations: n Found that a wind speed of 7.35 m/s would in fact lift the solar array off the surface. n Altered conceptual array design to include Kevlar areas equal to 10% of the total array area to provide space for Martian rock placement for weighing down the array. n 9.2 kg/m^2 of rock is needed in the 10% Kevlar regions to secure the array against the top recorded Mars wind of 25 m/s. n The major effect of this consideration is increased deployment time. Solar Cells Kevlar Areas

June 3, 2008 Slide 3 Areas of Revision cont. l Latitude considerations: n Ran model for multiple latitudes to show change in performance based on location. n Optimal location at 31° N, with a minimum of 6.57(kW-h/m^2/sol) and 49% daylight/sol for a period of 100 sols. n Northern latitudes better than corresponding southern latitude.

June 3, 2008 Slide 4 Results

June 3, 2008 Slide 5 Results cont.

June 3, 2008 Slide 6 Effects on Deployment Time l Considered the 100kW average power system located at the equator. n Requires a 25,000 m^2 rollout array field due to addition of the Kevlar areas. n Assume array blankets are 2m wide for easy storage and handling by two astronauts n Assume each blanket weighs 80lbs again for easy handling n With 0.07 kg/m^2 expected array density, need only 18 blankets total n Assume astronauts can unroll array at a walking speed of 1m/s, requires only 7hrs for unrolling n Time will be needed for unloading positioning and hookup, if assume 1hr for this for each array this adds 18hrs n In addition to this rocks must be placed in the Kevlar areas. Assume Kevlar areas are 1ft in length and the complete 2m width. Need 5.6kg of rock in each area. There are 225 of these Kevlar areas per array so a total of 4050 of these areas. Assuming 2 rocks are needed per area to secure the 2 sides of the array this requires 8100 rocks to be placed. If 30 seconds is needed to pick and place a rock this will take 33.75hrs for 2 crew. l Total deployment time is then 66hrs for 2 crew members

June 3, 2008 Slide 7 Deployment Time cont. l Power delivery during deployment: n We see that deployment gives 0.76 kW per man hour, therefore we only need 13.2 man hours to reach a capability of 10 kW which is enough for minimal stay alive power. n If you are conservative and neglect this and say full deployment and initial usefulness takes 1 week, we need either a 10kW RTG or fuel cell system to provide 10kW power over the week n RTG system would be approximately 1200kg and 0.6 m^3 n If use RFC, need 2400kg system with volume 8.4 m^3 l Sensitivity of total deployment time to different factors: n Sensitivity to array area=0.99 n Sensitivity to walking time=0.96 n Sensitivity to rock placement time=0.97 n Sensitivity to off-load and hookup time=0.965 n We see that the total deployment time is most sensitive to walking time so the design should be sure to make the unrolling of the array by astronauts in suits easy

June 3, 2008 Slide 8 For Winfried