Magnetics Business & Technology - Summer 2018 - 11

SPECIAL REPORT: AEROSPACE & DEFENSE
Glenn's breakthrough technology prolongs this operational
lifetime through two related innovations. The first is an innovative
magnetic field configuration that provides magnetic shielding to
eliminate interactions between the high energy xenon plasma
produced by the HET and the ceramic chamber that contains it.
The second is a means of replacing eroded discharge channel
material via a channel wall replacement mechanism. By increasing the lifetime and efficiency of HETs, Glenn's technology is
expected to help enable a new era of space propulsion.
The benefits include improved efficiency because unique designs
minimize energy loss to the discharge chamber, which improves
discharge efficiency. Lifetime of the HET is extended five times,
from approximately 10,000 hours to more than 50,000 hours.
Performance improvements result from a greater fraction of the
electrical energy from the solar array being used to produce
thrust, and a decrease in electrical energy being lost as waste
heat radiated to space.
The technology is believed to have application for satellite propulsion, material processing such as ion implantation and etching
for semiconductor manufacturing, high-energy physics and deep
space probes.

The interaction of the accelerated plasma and the downstream
edge of the channel, where the plasma is the most energetic,
results in erosion of the surrounding magnetic system used to
generate the plasma. One of NASA Glenn's novel designs relies
on an azimuthally symmetric configuration that minimizes radial
magnetic fields at the discharge chamber walls. This configuration completely shields the walls of the discharge chamber from
the high-energy plasma ions.
In the discharge-channel-wall replacement innovation, an actuator can be configured to extend the discharge chamber along
the centerline axis. The actuator can be either mechanical or
programmable. In either case, the sleeve can be extended while
an upstream portion of the discharge chamber remains stationary, thereby preventing plasma exposure. These novel designs
increase the efficiency and extend the lifetime of the HET to five
times that of unshielded thrusters, aimed at enabling a new era
of space missions.
Visit https://www.nasa.gov for the latest space news.

How it works
Used for propelling earth-orbiting satellites and deep-space robotic vehicles, the HET gets its name because it traps electrons
with an intense radial magnetic field in an azimuthal Hall current
moving around the circumference of an annular ceramic channel.
The electrons in the circulating Hall current ionize the onboard
propellant - the inert gas xenon - and create an ionized plasma.
The xenon plasma is then accelerated axially, via an applied
electric field along the coaxial channel, to an exit velocity of up to
65,000 miles per hour to produce thrust.

To Space

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Summer 2018 * Magnetics Business & Technology

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