No not the bottom the top! So we could align the panels with the sun and the sides of the bus makes great heat radiator My thruster design: http://www.alibaba.com/product-gs/1454501646/12V600AH_LiFePO4_battery_pack_for_electric.html : 12 VDC, 600 Ah, 53 kg MPD thruster = 4 4 cm internal diameter, with persistent superconducting magnet for external field, 30 kg? >110000 m/s exhaust velocity Power converting circuit: Still not sure with the design that can elevate 12v toward like 10kv, 20 kg max, radiator inclusive? Capacitor bank: 1 megawatt firing every 1 minute? 50 kg? Tank mass: 500 kg Argon mass: 1200 kg Assuming school bus weight is 9 metric tons, then Total dry mass: 10153 kg Wet mass: 11353 kg Delta-v = 12288.41 m/s Unfortunately wikipedia dV chart for low-thrust engine doesn't include LEO to GEO, but LEO to low lunar orbit requires 8 km/s So in short this bus could go to moon! Yay Reaction/rotation control system: 3 magnetorquers Several rotation and translation RCS ports using argon from main tank 3 control moment gyro