1. Announcements Pick up graded homework. Pick up handout (“The Virtual Astronaut”) and read over the weekend. First project due today by 5:00 p.m.

2. Space Exploration 13 October 2006

3. Today: History of space exploration Cost of the space program Why it’s difficult, expensive, and dangerous WARNING: Today’s lecture will contain OPINIONS!

4. History 1957: Sputnik 1, first artificial satellite 1958: Explorer III, first US satellite, discovered radiation belts 1959: Lunar flyby, landing 1960: Weather satellite 1961: Humans in space 1962: Venus flyby 1965: Mars flyby 1969-72: Apollo moon landings 1973: Jupiter flyby 1979-89: Voyager flybys of Jupiter, Saturn, Uranus, Neptune 1982-2010: Space shuttle program 1990: Hubble Space Telescope deployed 2000-?: International space station

5. Apollo Moon Landings

6. NASA budget

8. Physics of Space Flight Low earth orbit: 200 miles high Gravitational energy is about 3.1 megajoules per kilogram Required speed: 7.9 km/s (!) Kinetic energy is 31 MJ/kg (For comparison, boiling water into steam requires about 2.5 MJ/kg)

9. Physics of Space Flight Rocket propulsion is inefficient! Cost of shuttle program: $1.3 billion per launch

11. Humans vs. Robots NASA annual budget is about $16 billion Of this, about half is for human space flight (shuttle, space station); other half is for robotic missions, space telescopes

12. Why haven’t we gone to Mars? 140 times farther than the moon (at best) Months of weightlessness is crippling Serious radiation hazards Would have to carry food, fuel, oxygen to last years Taking earth life to Mars could confuse search for native Martian life So much to learn from unmanned exploration!

13. The Outer Solar System Jupiter Saturn Uranus Neptune On this scale: 1 A.U. = 7 pixels Orbital radii: Jupiter5.2 A.U. Saturn9.5 A.U. Uranus19 A.U. Neptune30 A.U.

14. The Inner Solar System Mercury Venus Earth Mars Sun On this scale: 1 A.U. = 120 pixels Diam. of Sun = 1 pixel Diam. of moon’s orbit = 1/2 pixel Diam. of earth = 1/100 pixel

15. Earth and Moon to scale

16. Low-Earth orbit

18. NASA’s future plans