----- Original Message ----- From: "Gautam Mukunda" <[EMAIL PROTECTED]> To: "Brin-L" <[EMAIL PROTECTED]> Sent: Monday, April 22, 2002 7:06 PM Subject: RE: tech question
> Orbital Mechanics questions: > If you are traveling in the space Shuttle in space, and you want to > increase your altitude, do you increase or decrease your speed? > > Does this change when you are stationary in orbit vs orbiting? > > Nerd From Hell > > Decrease. I'm not sure what you mean by stationary in orbit. Well, that is only sorta true, Gautam. In order to increase your height, you accelerate along the direction you are traveling, thus increasing your speed. If you started out in a circular orbit, the result would be an elliptical orbit. At its apogee, the speed will be lower than it was in the original orbit. At its perigee, it it will be higher. Now, if you then do another burn half an orbit later, you can have a new circular orbit at a greater distance above the earth (or the moon or the sun or etc.). The velocity in this orbit will be lower than the velocity in the original orbit. > > For normal calculations, your velocity in orbit is that velocity at which > the inward pull necessary to bend your straight track into a circle with a > center at the center of mass of the earth is equal to the force of gravity > exerted by the earth at that altitude. Thus: > m1v^2/r = Gm1m2/r^2 > Where v is velocity, r is distance from the center of the earth, m1 is the > mass of the object in orbit, m2 is the mass of the earth, and G is the > Gravitational constant. > Simplifying: > v^2r=Gm2 > G and m2 are constants. Gm2=C > Thus, > v^2r=C and > v=(C/r)^.5 > So as r increases, v decreases. > > All of that from 5 years ago memory of my physics courses, but I'm pretty > sure it's right. Well, my last physics course was more than 20 years ago, but I'm fairly sure I'm right too. :-) Finally, I'm guessing Chad was thinking about a geosyncronous orbit. That really has nothing to do with the problem. Dan M.
