On Tue, 17 Dec 2002 22:14:25 -0500, Alex Fraser <[EMAIL PROTECTED]>
wrote:
>I'm not so sure you need real accurate guidance for a space ship, isn't
>space a real big target? How could you miss?
The trick to flying, as Douglas Adams pointed out, is to throw
yourself at the ground and miss. So getting to space requires little
accuracy, you just have to stay pointed generally up.
But if you don't make orbit, you'll just fall back down. What good ia
that? (Well, there's tourism...) And to make orbit, you have to
climb up out of the atmosphere, then throw yourself *parallel* to the
ground. You'll cover hundreds of miles as you do this, and you have
to keep pointed in the same direction so you don't hit the ground, or
the air, or get too high and hit the air on the other side of the
planet, etc.
If you delta-v running out of your ears, you can take Vanguard
approach. They went way up, and didn't do that wonderful a job of
flying parallel to the ground. But because they went way up, their
margin for error went way up too. The Vanguards, launched in 1958 and
1959, are still up there, though you need a good telescope to see
them.
If you don't have a lot of delta-v to spare, you have to be pretty
accurate in your navigation. Otherwise you could reach orbital
velocity but fail to make orbit.
-R
--
"Is this a bagel?"
"It's the Guardian of Forever!"
"Well yes. But is it a bagel?"
--Overheard at Loscon 29
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