The shuttle must perform the de-orbit burn to change its orbit so that the perigee, the point in the orbit closest to Earth, is inside of Earth's atmosphere. De-orbit maneuvers are done to lower the perigee of the orbit to 60 miles (or less). An altitude of 60 miles is important because this is where the orbiting spacecraft is recaptured by Earth’s gravity and re-enters Earth’s atmosphere.

Question

Calculate the minimum change in velocity (delta v or ∆v) required for the space shuttle to decrease its altitude to 60 miles when it’s orbiting with an apogee of 246 miles and a perigee of 213 miles above the surface of Earth.

Answer 1

Calculate the minimum change in velocity (delta v or ∆v) required for the space shuttle to decrease its altitude to 60 miles when it’s orbiting with an apogee of 246 miles and a perigee of 213 miles above the surface of Earth.

Answer 2

415

Answer 3

306

Answer 4

perigee changes from 213 to 60
153 miles
multiply 2 due to the rule of 1 mile per 2 ft/s
306 ft/s
it is a slowing maneuver so it is negative
-306 ft/s

Answer 5

Nobody- how did you do that? What formula?

Answer 6

There is no formula. It's simple math. Just look at the units. When you subtract 60 from 213, you get how far you have to travel (still in miles). Then you multiply the result by 2 ft/s per mile. In this, the miles cancel out, and you are left with ft/s. That gives the change in the magnitude of the velocity, but you have to add the direction which is negative because you are decreasing speed rather than increasing it.