These are the most frequently used words in this book.
amount
apollo
ascent
atmosphere
carbon
chamber
change
chemical
course
courtesy
crew
days
down
during
earth
electric
energy
engine
exhaust
expedition
exploration
explorers
figure
first
force
fuel
gas
gravity
heat
high
however
human
hydrogen
journey
lander
landing
large
launch
launcher
less
liquid
low
manoeuvre
mars
martian
mass
material
mission
moon
must
nasa
necessary
need
new
now
nozzle
nuclear
orbit
oxygen
payload
place
planet
point
power
pressure
produce
programme
propellant
propulsion
ratio
reactor
required
requirements
requires
return
rocket
should
shuttle
space
spacecraft
stage
surface
system
take
tanks
technology
temperature
therefore
thrust
thruster
time
tonnes
transfer
two
use
used
vehicle
velocity
water
years