-Z- (z@gundam.com)
Sat, 23 Sep 2000 11:57:02 -0700


> -----Original Message-----
> From: owner-gundam@1u.aeug.org [mailto:owner-gundam@1u.aeug.org]On
> Behalf Of Ricky Lai
> Sent: Saturday, September 23, 2000 09:06
> To: gundam@aeug.org
> Subject: [gundam] MS lanching
>
> Pardon my ignorance, but what is "delta-V?" How does a quick attaining of
> delta-V useful in economizing on propellant?

Delta-V is an engineering term meaning "change in velocity" -- the Greek letter
delta is the mathematical symbol for change, the Latin letter V is the symbol
for velocity.

One travels through space by changing one's acceleration, because an orbit is
determined by the speed at which one travels. That's how you get to orbit in
the first place, by achieving a speed so great that you fall around the Earth
instead of back to the surface.

(Newton's Cannon: place a cannon on a mountain so high that it sticks out of the
atmosphere, so no friction. Fire a charge and watch the cannonball fly out in
an arc that conforms to the Earth's surface until graviy caused it to fall to
the ground. Bigger charge and the ball flies further around the Earth before
falling. Big enough charge and you'd better move the cannon before the ball
goes all the way around and up your tailpipe!)

To move from a low orbit to a higher orbit, you increase your velocity, to move
from high orbit to low orbit you decrease it. The difference between the two
orbits is the delta-V -- the change in velocity -- required to make the
transition.

To go from Earth's surface to low Earth orbit (LEO) -- the altitude at which the
space shuttle and International Space Station operate -- requires a delta-V of
8.6 km per second. To go from LEO to geosynchronous Earth orbit (GEO) -- 22,500
miles (35,400 km) up, where communications satellites operate -- requires
another 3.8 km per second, which is what the Payload Assist Module (PAM) uses to
kick a satellite out of the shuttle's cargo bay to put a commsat in orbit.

If your browser can handle JavaScript, you might enjoy playing with the Delta-V
Calculator:

http://www.strout.net/info/science/delta-v/intro.html

For information on how delta-V impacts Gundam, try my Gundam High Frontier page:

http://www.dyarstraights.com/msgundam/frontier.html#Lagrange

-Z-

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