During a de-orbit burn, a pre-calculated AV (delta V, change in velocity) will be used to decrease the Orion MPCV's altitude. The Orion MPCV's Orbital
Maneuvering System (OMS) engines provide a combined thrust force of 53,000 Newtons. The Orion MPCV has a mass of 25,848 kg when fully loaded.
What is the difference between the Orion MPCV's mass and weight? An object's mass does not change from place to place, but an object's weight does
change as it moves to a place with a different gravitational potential. For example, an object on the moon has the same mass it had while on the Earth
but the object will weigh less on the moon due to the moon's decreased gravitational potential. The Orion MPCV always has the same mass but will weigh
less while in orbit than it does while on Earth's surface.
CALCULATION: Calculate how long a de-orbit burn must last in seconds to achieve the Orion MPCV's change in altitude from 395.0 kilometers to
96.5 kilometers at perigee. Use the equations and conversions provided to find the required burn time.
Equations to use:
1. Newton's Second Law:
F = ma
o Where:
o a = acceleration is in meters per second per second ( ") units
o F = force is in Newtons IN = 1("
o M = mass is in kg units
o Solve for
2. Determination of AV:
Find the change in altitude (Original Perigee - New Perigee)
Use the conversion factor of
0.379
1 km
o Equation should read: AV = (Change in Altitude) X 0.379
3. Equation that defines average acceleration, the amount by which velocity will change in a given amount of time: a =
4. Rearranging the acceleration equation above to find the time required for a specific velocity change given a specific acceleration, where
t = AV
o AV = change in velocity in meters per second
o a = acceleration is in meters per second per second,
o t = required time in seconds (this is the value that you are solving for)