low thrust propulsion is essential for
all space missions and NASA's Lewis
research center is conducting programs
to provide a broad range of low thrust
propulsion concepts for these auxiliary
and primary functions auxiliary
propulsion basically is used for keeping
space systems in desired locations or
for orientation typical examples are the
reaction control systems for earth to
orbit vehicles drag makeup and attitude
control for low Earth orbit systems such
as the Space Station freedom station
keeping for higher orbit systems such as
geosynchronous satellites and then retro
functions near planetary bodies primary
propulsion functions include the moving
of space vehicles from point to point in
earth space as well as propulsion from
Earth space to various planetary bodies
on earth to orbit vehicles such as the
Shuttle Orbiter low thrust propulsion
systems are used to control the
orientation of the vehicle examples
would be to control the movement of the
shuttle orbiter to face the Sun or
reorient it to meet other specific
requirements and then to deorbit the
shuttle for its return to Earth the low
thrust devices used for these
applications are called reaction control
systems for use on the space station
freedom to different times of low thrust
propulsion systems have been selected
for drag makeup thrusters call resistol
jets will be
these resistor Jets will use the waste
gas from the various Space Station
modules this approach eliminates the
requirement for the launch of drag
makeup propellant and the return of
waste gases for the attitude control of
the space station lewis is working on
small chemical rockets these engines are
used to control the torques and forces
that are created during shuttle birthing
and other situations where moderate
thrust levels are required high Earth
orbit systems need two very different
kinds of auxiliary propulsion systems
first when geosynchronous satellites are
placed into orbit an apogee propulsion
system is required to circularize the
satellite and place it into the correct
orbit the geosynchronous orbit is the
one that makes the satellite appear to
be in a fixed position when viewed from
the earth in order to keep the
satellites in desired orbit NASA Lewis
is working on very low thrust Electric
Rockets called arc Jets a final example
of auxiliary propulsion is the use of
chemical rockets near planetary bodies
it is necessary to provide a retro
propulsion maneuver at planetary bodies
so they may be captured and allow the
spacecraft to go into orbit around the
bodies or simply to slow down to obtain
desired data primary propulsion is being
developed for use in both Earth orbit
and for planetary missions planetary
missions include the transfer of systems
to beyond Earth space to such targets as
planets comets and asteroids in summary
then all space missions use low thrust
propulsion in one form or another the
Lewis research center is conducting a
low thrust propulsion program utilizing
an in-house University and industrial
team
this blend of skill and capability
assure that the program will develop
practical devices for near-term
applications and at the same time
produce more advanced concepts for the
longer term higher payoff national space
missions