I'm not good at maths. Don't get me wrong, it's cool and all but just I suck at it. Now, take this ability at maths and combine it with the fact that I've been given two (what I see as hard) mathematical questions to answer and one has a little problem. So I was kinda hoping that some kind soul at EOFF could put a poor person out of their number induced misery and help me out. I'm really at the end of my tether with these questions, I don't even know where to begin in trying to tackle them. If anyone can flex their big sexy mathematical muscles and help me out, I would be very grateful!

Quote Originally Posted by Question 1
1. When it is time for a Space Shuttle to come in for a landing, it needs to re-enter the Earth's atmosphere at the right time and place so that it can land successfully at the designated landing strip. Depending on the Shuttle's altitude, it's de-orbit burn must occur for the correct length of time for the Shuttle to begin its descent at the right speed and in the correct location. The de-orbit burn is done against the direction of travel. The Shuttle keeps going in the same direction but slows down due to the drag on the spacecraft as it enters the atmosphere.

De-orbit manoeuvres 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 215 miles above the Earth at perigee, and needs to drop the perigee to an altitude of 60 miles.

Your answer needs to be in feet per second.
Quote Originally Posted by Question 2
2. Using the change (delta) in velocity that must be used to lower the perigee to a 60-mile altitude (This was your answer to the Shuttle math question for Lesson 1) and assuming the Orbiter's OMS engines have a combined force (thrust) of 12,000 lbs and the Shuttle has a weight of 250,000 lbs (with a full cargo bay), use the equations below to compute the length (or time) of the burn necessary in minutes.

f = ma force equals mass times acceleration and t = v/a time equals velocity divided by acceleration

Your acceleration will be in G's, where 1 G = 32 feet per second per second (this is how far an object travels due to the force of gravity in a vacuum).

Hint: You can also use English slugs instead of G's. 1 slug = 32 pounds. This makes the equation somewhat simpler. Mass of the Orbiter = 250,000/32 slugs.