Mars trip

• Velocity (energy and $$expense$$) needed:
  • 11 km/s to escape from the Earth
    • at this point we are traveling 30 km/s around Sun
  • 2 more km/s
    • a perihelion velocity of 32 km/s gives aphelion at Mars
  • Launch window
    • start so that Mars (P = 1.9 y) arrives at the same time probe reaches aphelion
      • 0.7 y = 0.4 PMars
    • launch window repeats with synodic period of Mars
      • every 2.1 y
    • This is, literally, Rocket Science!
    • For Venus, a similar elliptical spacecraft orbit is needed
      • except: aphelion at Earth, perihelion at Venus
        • need 2 less km/s (i.e. 28 km/s) to “fall in” to Venus
      • To reach beyond Jupiter, use “gravity boost”, “cosmic billiards” Fig. 22-17, 18
        • Voyager 1 & 2 Grand Tour Jupiter, Saturn, Uranus, Neptune

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