Future of Life in the Solar SystemFuture of Life in Solar SystemTerraform other planets (Mars most likely)Space ColoniesSolar Power from spaceDyson spheresRobotsVon Neumann DevicesTerraforming Planets Seed other planets with “bio-engineered organisms”These make the planet more habitable for humansTo terraform (need H2O, O2, O3)e.g., Melt polar caps on Mars (1014 tons of ice)2500 to 10000 years to build up atm. pressure, get liquid waterTerraformed MarsOcean in northern lowlands covers25% of planetSpace coloniesSolar Power satellitesDyson sphere (Type II Civilization)Role of RobotsVon Neumann deviceLiving in Space to Robots…Space Colony (Island One)Solar Power SatellitesSolar Power SatelliteRocketsPrinciple: Newton’s Third Law1. Exhaust velocity Ve (km s-1)Ve ∝ √FexhaustFrocketFrocket = FexhaustTM2. Thrust (Force) F = (dM/dt) Ve(Newtons, Pounds) dM/dt = rate at which mass is ejected3. Mass ratioRM = Total Mass at Takeoff Mass After Fuel Used UpHigh mass ratios mean you need a lot of fuel to get acertain payload accelerated to a certain speedRecall Newton’s second law:F = (dp/dt) = m (dv/dt) = m a, if m constantIf v constant, but m is not,F = (dm/dt) v4. Specific impulse (s.i.)Thrust (Newtons/kg/sec,Rate of Fuel Use Pounds/Pounds/sec = “sec”)A measure of efficiency.Highest possible s.i. with chemical fuels is < 500Can the Rocket take off?To take off: Thrust > WeightTo escape gravity v > vesc = 11.2 km s–1 (7 miles/sec)This is very difficult for the gravity of the EarthSo we use Multi-stage RocketsFgravFthrustCurrent situationSpace Shuttle: Mass = 2 × 106 kgFthrust = 29 × 106 NewtonsRM = 68 for actual payloads.i. = 455 sec. ~ best possible with chemical fuelFor more adventurous exploitation of Solar SystemProbably want Nuclear PropulsionFission could give s.i. = 1.5 × 106 sec(in principle, more likely to get 20,000 sec)Current Initiative• Human mission to Mars• Several attempts to get started in past• Exploration Vision in 2004– First return to Moon– Then Mars– Long-term program needed–
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