Applications of the HDLT
Satellite Station Keeping
Though the HDLT has not yet flown in space, several current orbiting satellites use ion thrusters in the same fashion as is envisaged for the HDLT. In response to any change in a satellite's orbital plane an North South Station Keeping (NSSK) maneuver is engaged. For a satellite carrying ion thrusters, this is typically achieved by firing the NSSK thrusters twice a day for around 5 hours. As the satellite ascends through the Earth's equatorial plane on its inclined plane, the North thruster is fired for a period centered around this point of passage. Twelve hours later when the satellite this time descends through the equatorial plane, the South thruster is fired in the same manner and for the same duration. EWSK and attitude control is undertaken in a similar fashion.
In the future, it is increasingly likely that we will see plasma propulsion systems such as the HDLT flying on low earth orbit (LEO) satellites. It is envisaged that such thrusters would be used to transfer the satellites from their drop-off altitude to their operational orbit and maintain proper station keeping. At the end of their useful lifetimes, the plasma thrusters would be used to deorbit the satellites in a controlled fashion so that they burn up harmlessly in the atmosphere.
Interplanetary Missions
Artificial satellite's have enabled many scientific advances, but Humanity's imagination has not been satisfied to dwell on the Earth and its very close orbital neighbourhood. Many satellites have been deployed on interplanetary missions and humans have traveled as far as the moon. Though the moon landing is arguably Humanity's greatest engineering achievement, the moon itself has represented the boundary of practical manned missions into the solar system using conventional chemical rockets. The shear quantity of propellant and incredible time scale required to reach even our closest planetary neighbour, Mars, with traditional space technologies has to this day made the dream of crossing interplanetary space prohibitively costly both in financial terms and in potential risk to would-be human travelers. If chemical propulsion is capable of great thrust (on the order of several Mega-Newtons) it also has very low specific impulse a measure of the propellant burn rate efficiency. Maximum velocity is also restricted by low specific impulse making transit time too long for any practical mission with a human payload. If effective manned missions are to be mounted to breach the distance of interplanetary space, a faster and more efficient mode of transport is required. Plasma propulsion can achieve these goals.
It is for the purpose of interplanetary missions that NASA has sought to collaborate with our laboratory. In particular we are currently active with Astronaut F. Chang-Diaz's VASIMR group in the Advanced Space Propulsion Laboratory at Johnson Space Center, Houston. We envisage that the high performance and low risk design of the HDLT will make it a viable candidate for future manned missions to Mars.
The Plasma Research Laboratory at the Australian National University (Australia), the Cooperative Research Center for Satellite Systems and Auspace are also collaborating with the Propulsion and Aerothermodynamics Division at the European Space Agency (ESTEC Holland) on the development and testing of the HDLT prototype. This joint research program is funded by the DEST innovation access grant in Australia.
Return to HDLT Background Information Page
