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.

 

[Nate810]

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

 

[ogb p]

I am happy to help you in your learning journey. It is great that you are interested in understanding the formula for delta v and how it applies to de-orbit maneuvers. Let me break it down for you in simpler terms.

Delta v, or change in velocity, is a measure of how much the speed of an object changes. In the case of a de-orbit maneuver, we are looking at how much the speed of the Orbiter needs to change in order to lower its perigee (the point in an orbit closest to the Earth) to 60 miles.

Now, let's look at the given information. The Orbiter is currently at an altitude of 220 miles at its highest point (apogee) and 210 miles at its lowest point (perigee). In order to lower the perigee to 60 miles, we need to determine the change in velocity required.

We know that there is a 1 mile change for every 2 feet per second change in velocity when the Orbiter is below 500 miles above the Earth. So, we can use this information to calculate the delta v needed.

First, we need to find the difference between the current perigee altitude (210 miles) and the desired perigee altitude (60 miles). This gives us a difference of 150 miles.

Next, we can convert this difference to feet by multiplying it by 5,280 (the number of feet in a mile). This gives us 792,000 feet.

Now, we can use the given ratio of 1 mile change for every 2 feet per second change in velocity to determine the change in velocity needed. We divide 792,000 feet by 2 to get 396,000 fps.

Therefore, the Orbiter will need to change its velocity by 396,000 fps in order to lower its perigee from 210 miles to 60 miles. I hope this explanation helps you understand the concept of delta v and how it applies to de-orbit maneuvers. Keep learning and asking questions!