Magnetics Business & Technology - May/June 2019 - 22

INDUSTRY NEWS

Future of Electric Propulsion for Aerospace Subject of In-Depth Workshop at Upcoming
SpaceTech Expo
expo and welcomes space and defense executives and technical
leaders to hear industry heavyweights share their technical expertise, real-world case studies, and insights on industry trends.
Innovators at NASA's Glenn Research Center in Cleveland
have developed new technologies that increase the operational
lifetime of a HET, which is used primarily on earth-orbiting satellites and can also be used for deep-space robotic vehicles. The
operational lifetime of HETs is determined by the amount of time
the thruster can operate before the plasma within the channel damages the magnetic system. Prior to this innovation, the
plasma would erode the ceramic chamber of the HET in just over
a year of operation.

Photos courtesy of NASA

Electric propulsion, which often relies on advanced Hall Effect
thrusters (HET), may have been around for more than 50 years,
but it still has huge potential. It is being integrated in many cubesats and will also play a big role in the area of satellite servicing of crewed missions to the moon including the Lunar Orbital
Platform-Gateway and exploration missions that go deep into, or
even beyond, our solar system.
The capabilities of electric propulsion are becoming more apparent and are seen as a real
game changer in future missions, according to
Dr. John Brophy, engineering fellow and principal engineer of electric propulsion at NASA's
Jet Propulsion Laboratory in Pasadena, CA.
He will be presenting a workshop at the upcoming SpaceTech Expo in Pasadena
highlighting the history of electric propul- Dr. John Brohy of
NASA's Jet Propulsion
sion as well as some key challenges,
Laboratory
areas of research and a future outlook
on what electric propulsion can bring to
the aerospace business. Key learning
objectives will range from an overview of
the different types of electric propulsion systems, to current standards and certifications for electric propulsion systems and future
prospects for electric propulsion in the coming decade.
This workshop will be one of many featured at Space Tech Expo
2019 which takes place the week of May 20 in Pasadena. The
event is a leading showcase of space technology and services
for spacecraft, satellite and launcher systems, sub-systems,
components and materials for civil, military and commercial
space.

The breakthrough 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 will enable a new era
of space propulsion. HET lifetime is extended five times from approximately 10,000 hours to more than 50,000 hours.
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. 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. With regard to 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, enabling a new
era of space missions.
For more information, visit: http://www.spacetechexpo.com/

Space Tech Expo USA unites thousands of industry leaders,
decision makers, engineers, specifiers and buyers with the
manufacturers and supply chain for civil, military and commercial
space to network, discover the latest innovations, and grow their
businesses. The Space Tech Conference runs alongside the

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