|What is meant by a
hypergolic propellant and oxidizer?
Why is using a hypergolic fuel important when attempting to liftoff
from the moon's surface?
The mass of the LEM is about 5,000 kg. With an acceleration of
gravity of 1.7 m/s2, the weight of the LEM at liftoff is
W = m * g =
5,000 kg * 1.7 m/s2 =
The single engine on the LEM can produce 16,000 N of force.
(Remember, the Saturn V engines were measured in millions of Newtons of
force - not thousands of Newtons.) With the LEM's weight at 8,500 N, the
resulting net upward force is
Fnet = Fthrust
- W = 16,000 N
- 8,500 N = 7,500 N.
The initial liftoff acceleration of the LEM is
a = F / m
= 7500 N / 5000 kg =
The LEM will reach an orbital velocity of 1600 m/s at the orbital
altitude of 110 km above the lunar surface. While in orbit, the
LEM will catch up to the command module and dock. After docking
with the command module, it returns to Earth.
The following two images show the LEM a fraction of a second prior to
and after liftoff. Only the top section leaves the Moon. The
base remains on the Moon.