Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: marc on 22/03/2009 15:30:02

Title: How fast do you need to go to reach low orbit?
Post by: marc on 22/03/2009 15:30:02

marc asked the Naked Scientists:
   
If you were at 12 degrees and 3 miles high how fast would you have to be going to reach a low orbit.

What do you think?

Title: How fast do you need to go to reach low orbit?
Post by: Vern on 22/03/2009 15:45:35

This is a nice paper on the subject. (http://www.spacefuture.com/archive/getting_to_low_earth_orbit.shtml)
I think three miles up might be a little too low. There is still a lot of atmosphere at that height and an orbit would quickly deteriorate.

Quote from: the link

First, you need something that can push, pull, drag or carry a given mass and volume about 150 kilometers up with a net velocity of at least 7,814 m/s tangent to the curve of the Earth. The height is needed to get out of most of the drag in the air, which is noticeable at the needed speeds to stay in orbit. The velocity is what is needed to stay in orbit at that altitude.

Title: How fast do you need to go to reach low orbit?
Post by: syhprum on 22/03/2009 23:07:42

The minimum orbital time at ground level is 84 minutes but this cannot be used by a satellite due to the atmosphere, the minimum time for a practical satellite is about 90 minutes to give a life of about a month.