How Is Delta-V Calculated for De-orbit Maneuvers?

[davo]

please help me i am new here and need/want to learn this...

ok i am curently in WAS(wa arowspace scolars) I am a bad speller but i could care less also I am new here. I know what the formula for delta v is but i do not understand it. I am interested in learning but please put it into layman's terms. also hear is the Question.

De-orbit maneuvers are usually done to lower the perigee of the orbit to 60 miles (or less). The Orbiter is captured and re-enters as it passes into the atmosphere at this altitude.

There is a change of 1 mile for every 2 feet per second (fps) change in velocity when you are below a 500-mile altitude above the Earth.

Determine the change in velocity (delta-V) that the Shuttle will need to make if it is at an altitude of 220 miles above the Earth at apogee and 210 miles above the Earth at perigee, and needs to drop the perigee to an altitude of 60 miles.

 

[member 553083]

The formula for Delta V is: Delta V = (Vfinal - Vinitial)*sqrt(2*mu/r) where mu = the gravitational parameter, and r = the initial orbital radiusIn layman's terms, Delta V tells us how much of a change in velocity you need to make in order to reach your desired altitude. To calculate Delta V, you need to know your initial orbital radius and the desired final orbital radius. You can then calculate the difference between the two velocities and multiply it by the square root of 2 multiplied by the gravitational parameter divided by your initial orbital radius. In this case, the initial orbital radius is 210 miles and the final orbital radius is 60 miles. The gravitational parameter for the Earth is 398600 km3/s2. Using the formula above, Delta V = (Vfinal - Vinitial)*sqrt(2*mu/r) we get: Delta V = (Vfinal - Vinitial)*sqrt(2*398600 km3/s2/210 miles) Therefore, the change in velocity (Delta V) that the Shuttle will need to make if it is at an altitude of 220 miles above the Earth at apogee and 210 miles above the Earth at perigee, and needs to drop the perigee to an altitude of 60 miles is: Delta V = (Vfinal - Vinitial)*sqrt(2*398600 km3/s2/210 miles) = (Vfinal - Vinitial)*sqrt(18.8 km/s2/mile) = (Vfinal - Vinitial)*4.3 km/s