reply to post by Foppezao
ICBM's are designed to carry a payload into low orbit, then release them so they re-enter over their targets. They are not designed to go into space,
they don't carry enough fuel to make the burns required to achieve escape velocity. A rocket in orbit has NOT
escaped gravity, as you claim, if
it had, then it would have flown off into space. What you see when a rocket is in orbit is it falling in freefall around the planet, but by changing
the eccentricity of the orbit, the ship always falls beyond the arch of the planet, thereby missing it.
If a rocket was launched into orbit, it would fall back to the ground on the next pass, because it has not escaped the earths gravity. Using a series
of rocket burns, they make the eccentric (oval) orbit, less and less eccentric (more circular) until the object misses falling back to earth on the
Pardon my crappy graphics here, but it something like this:
This is a highly eccentric orbit, immediately following the launch, that will bring the craft right back to the ground:
Using a pro-grade burn, they move the Periapsis (closest point in the orbit) out from the plant, but its still a pretty eccentric orbit:
If they keep making pro and retograde burns at the right time, they can get the eccentricity as low as possible, which makes for a stable orbit:
If they continue to make only pro-grade burns they can finally achieve escape velocity:
Rockets themselves are complex custom made pieces of precision engineering that are ordered as needed in advance of a mission. NASA does not keep a
warehouse of “ready to go” rockets configured for whatever scenario might come up on a seconds notice. That's why rescue in space has always been
considered a non-option. Toward the end of the shuttle program, for certain missions, they were being forced to prep two shuttles at a time to attempt
a rescue if needed, but everyone knew that it was just for show because of the bad press over Columbia. It was costing them twice as much time and
money just to have that backup moved to the pad.
The Voyagers were sent on Titan IIIE-Centaur rockets, which have not been in production since 2005. They used low power, time consuming routes that
allowed them to use planets gravity to pull, and slingshot them along their paths (gravitational assist trajectories ). In the scenario we're talking
about here, we would not have years to build, outfit, prep, and launch a rocket, then wait while it built up enough speed to reach its target.
edit on 3/24/2012 by defcon5 because: (no reason given)