CAPE CANAVERAL, Florida — The U.S. Air Force made an unusual announcement on Monday that its secret X-37B space plane will host a Hall thruster experiment during Orbital Test Vehicle mission 4, the fourth flight of the X-37B reusable flight vehicle scheduled to launch on May 20, 2015 from Cape Canaveral, Florida.
A Hall thruster is a type of electric propulsion device that produces thrust by ionizing and accelerating a noble gas, usually xenon. While producing comparatively low thrust relative to conventional rocket engines, Hall thrusters provide significantly greater specific impulse, or fuel economy. This results in increased payload carrying capacity and a greater number of on-orbit maneuvers for a spacecraft using Hall thrusters rather than traditional rocket engines.
Hall thrusters trap electrons in a magnetic field and use them to ionize the onboard propellant. The magnetic field also generates an electric field that accelerates the charged ions creating an exhaust plume of plasma that pushes the spacecraft forward. When solar arrays are used to supplement the electrical power, a Hall thruster can be a part of an advanced Solar Electric Propulsion system that uses 10 times less propellant than equivalent chemical rockets.
“We proved that this thruster can process three times the power of previous designs and increase efficiency by 50 percent,” said Dan Herman, Electric Propulsion Subsystem lead.
According to the Air Force, the Hall thruster that will fly on the X-37B experiment is a modified version of the units that have propelled its first three Advanced Extremely High Frequency military communications spacecraft.