Magnetic Shielding of Ion Beam Thruster Walls
Hello
reader!
It
follows a note published on the day (02/15), in the site
"www.space-travel.com", highlighting that a research team at the Caltech's Jet Propulsion Laboratory, is developing
magnetic shielding walls for rocket motors ion beam.
Duda Falcão
ROCKET SCIENCE
Magnetic Shielding of Ion Beam
Thruster Walls
by Staff
Writers
Washington
DC (SPX) Feb 15, 2013
File image. |
Electric
rocket engines known as Hall thrusters, which use a super high-velocity stream
of ions to propel a spacecraft in space, have been used successfully onboard
many missions for half a century. Erosion of the discharge channels walls,
however, has limited their application to the inner solar system.
A
research team at Caltech's Jet Propulsion Laboratory, in Pasadena, Calif., has
found a way to effectively control this erosion by shaping the engine's
magnetic field in a way that shields the walls from ion bombardment.
Ions are
produced in Hall thrusters when electrons from an electric current collide with
the propellant atoms to form a plasma in the discharge chamber. Thrust is then
generated by the interaction of this current with an applied magnetic field
that creates a strong electric field.
The
magnetic field is mostly perpendicular to the channel walls whereas the
electric field is mostly parallel to the walls. This electric field then acts
as the driving force on the ions, accelerating them to very high speeds
(>45,000 mph) toward the exhaust opening.
However,
the presence of a plasma in the thruster's discharge chamber leads also to a small
component of the electric field parallel to the magnetic field lines. This
component then accelerates some ions toward the discharge chamber (rather than
the exhaust opening) causing erosion by sputtering material from the walls.
Guided
by theory and numerical simulations, the research team designed a thruster
configuration in which the effect of the plasma on the magnetic field lines
along the walls is minimized, forcing the electric field to be perpendicular to
the lines.
Based on
the numerical predictions, the effect of this magnetic field topology would be
to accelerate ions away from walls while also significantly reducing their
energy adjacent to the walls. Erosion then would be reduced without degrading
propulsive performance.
The
method now known as magnetic shielding was verified by experiments in a vacuum
facility using a modified thruster.
The
combined results of the simulations and experiments demonstrated that there was
100 to 1,000 times less wall erosion when using magnetic shielding. The results
were published in the American Institute of Physics (AIP) journal Applied
Physics Letters.
"Magnetic
shielding of walls from the unmagnetized ion beam in a Hall thruster" is published in the journal Applied
Physics Letters.
Fonte: Site www.space-travel.com
Comentário: Trago essa notícia para o blog pois pode ser
interessante para o grupo do Professor José Leonardo Ferreira do Laboratório
de Plasma do Instituto de Física da Universidade de Brasília (saiba
mais sobre esse trabalho clicando aqui) que trabalha na área de motores iônicos
por efeito Hall, como também para o Laboratório
Associado de Plasma (LAP) do Instituto
Nacional de Pesquisas Espaciais (INPE). Além disso essa notícia
está aberta ao debate entre os interessados.
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