These are the most frequently used words in this book.
agency
air
american
apollo
astronaut
atmosphere
between
carried
carry
center
communications
control
crew
data
date
days
delta
design
designed
development
during
early
earth
energy
engine
experiments
explorer
first
flight
force
fuel
high
however
including
ing
kg
km
known
later
launch
launched
lunar
manned
mars
mass
may
missile
mission
module
moon
nasa
national
new
orbit
orbiter
part
payload
pilot
point
probe
program
project
propellant
propulsion
provide
research
rocket
satellite
science
second
see
series
shuttle
site
small
solar
soviet
soyuz
space
spacecraft
speed
stage
states
station
study
surface
system
technology
test
three
thrust
time
tion
two
university
use
used
vehicle
world
years