Start with: horizontal acceleration vs. gravity
Fire a bullet and drop another at same time
Which hits ground first? (both same time)
Explain
Satellite orbits similar
Velocity of initial trajectory will determine what happens
See fig. 4.1, pg. 60
Obviously, a minimum velocity is required to get through the atmosphere
Anything less, and the object will fall back to earth
Circular satellite velocity: 8 km/sec
Velocity needed to achieve earth orbit
NOT out of gravitational influence
Satellite "falls" around the earth, just like the moon
Apogee vs. perigee: relative orbital distances
Farthest distance vs. closest approach to parent body
Final speed of rocket at burn-out determines resulting orbit
See fig. 4.2, pg. 61
If <8 km/sec: orbit is an ellipse
Will impact earth: works well for ballistic missiles
"Crimson Tide" scene
If > CSV then will achieve earth orbit
If > 11 km/sec then will escape earth's gravitational pull
The "Escape Velocity" needed for interplanetary travel
Also called "parabolic velocity"
Interplanetary travel
Payload weight is critical (payload is anything taken aloft)
Directly affects the amount of fuel needed to achieve escape velocity (F=ma)
Vicious circle: the added fuel also adds weight!
The idea is to minimize the weight of the fuel to allow more payload
Videodisc: "For All Mankind" Ch. 29 (Saturn V), Ch. 25 (Apollo 8 lift-off)
Earth vs. lunar rendezvous debate
We have used flybys to get us to the outer planets, and beyond
See fig. 4.7, pg. 64
Space programs of all countries have been very active
Lots of debris left in orbit (see fig. 4.5, pg. 63)
What to do with it all?
A real problem? or no big deal?