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USS Bekuo VASIMR
VASIMR or VAriable Specific Impulse Magnetoplasma Rocket is new propulsion concept
which uses microwave generated hydrogen plasma to propell spacecraft. It can work
with high range of Isp - from 5400 to 30000.
USS Bekuo is a real advanced plasma propelled spacecraft project, developed by
Dr.Franklin Chang-Diaz and his team in Advanced Space Propulsion Laboratory at the
Johnson Space Center. Now work continues in AdAstra Rocket company.
The design of the VASIMR
is so original that a prototype is being developed in collaboration with the
Department of Energy and with the Oak Ridge National Laboratory and its Center
for Manufacturing Technology. The VASIMR is expected to be commercially useful
for boosting communication satellites and other Earth-orbiting spacecraft to
higher orbits, retrieving and servicing spacecraft in high orbits around the
Earth, and boosting high-payload robotic spacecraft on very fast missions to
other planets. Similarly, the VASIMR should make it possible for robotic
spacecraft to travel quickly to the outer reaches of the Solar system and begin
probing interstellar space. By far, the greatest potential of the VASIMR is
expected to lie in its ability to significantly reduce the trip times for human
missions to Mars and beyond. This reduction in times is expected to enable
long-term exploration of outer space by humans — something that
conventional rocket designs now preclude. Because the VASIMR uses
plasma to produce thrust, it is related to several previously developed
thrusters; namely, the ion engine, the stationary plasma thruster (SPT) (also
known as the Hall thruster), and the magneto- plasmadynamic (MPD) thruster
[also known as the Lorentz-force accelerator (LFA)]. However, the VASIMR
differs considerably from these other thrusters in that it lacks electrodes (a
lack that enables the VASIMR to operate at much greater power densities) and
has an inherent capability to achieve high and variable Isp.
Both the ion engine and the SPT are electrostatic in nature and can only
accelerate ions present in plasmas by means of either (1) externally applied
electric fields (i.e., applied by an external grid as on an ion engine) or (2)
axial charge nonuniformity as in the SPT. These ion-acceleration features, in
turn, result in accelerated exhaust beams that must be neutralized by electron
sources strategically located at the outlets before the exhaust streams leave
the engines. In the LFA, acceleration is not electrostatic but
electromagnetic. A radial electric current flowing from a central cathode
interacts with a self-generated azimuthal magnetic field to produce
acceleration. Although LFAs can operate at power levels higher than those of
either the ion engine or the SPT and do not require charge neutralization,
their performances are still limited by the erosion of their electrodes. An MPD plasma injector
includes a cathode in contact with the plasma. Although the plasma at the
location of contact is relatively cold, the cathode becomes eroded and the
plasma becomes contaminated with cathode material (typically tungsten). The
erosion and contamination can contribute to premature failure and to increased
loss of energy through radiation from the contaminants in the plasma. An equal
limitation on performance is exerted by nonionized propellant in a high-power
amplifier cavity that is part of the MPD; the reason for this limitation is
that neutral atoms and molecules in this region lead to charge-exchange losses,
which, in turn reduce the overall efficiency of the engine and increase the
unwanted heat load on the first wall (the liner) of the MPD thruster. The design of the VASIMR
avoids the aforementioned limiting features. The VASIMR contains three major
magnetic cells — the forward, central, and aft cells. A plasma is injected
into these cells, then heated, then expanded in a magnetic nozzle. (The
magnetic configuration is of a type known as an asymmetric mirror.) The forward
cell handles the main injection of propellant gas and an ionization system; the
central cell serves as an amplifier to further heat the plasma to desired
magnetic-nozzle-input conditions; and the aft cell acts as a hybrid two-stage
magnetic nozzle that converts the thermal energy of the fluid into directed
flow while protecting the nozzle walls and allowing efficient detachment of the
plasma from the magnetic field. During operation of the VASIMR, a neutral gas
(typically, hydrogen) is injected into the forward cell, where it is ionized.
The resulting plasma is then heated in the central cell, to the desired
temperature and density, by use of radio-frequency excitation and ion cyclotron
resonance. Once heated, the plasma is magnetically and gas-dynamically
exhausted by the aft cell to provide modulated thrust. Contamination is
virtually eliminated and premature failures of components are unlikely. The VASIMR offers
numerous advantages over the prior art: ·
Its unique
electrodeless design provides not only high thrust at maximum power but also
highly efficient ion-cyclotron-resonance heating, and high efficiency of the
VASIMR regarded as a helicon plasma source. ·
Because the VASIMR
operates at relatively high voltage and low current, its mass is relatively
low. This means that a one-ship human mission will not depend on a high-energy,
complex rendezvous near Earth to achieve escape velocity. Instead, a rapid
interplanetary transfer will be achieved with an adaptable exhaust, which will
provide optimal acceleration throughout the mission. ·
The residual magnetic
field of the engine and the hydrogen propellant will be effective as a shield
against radiation. ·
Because of its
continuous acceleration, the VASIMR will be able to produce a small amount of
artificial gravitation, thereby reducing the physiological deconditioning
produced by weightlessness. ·
The variability of
thrust and Isp at constant power will afford a wide range of
capabilities to abort. ·
Because hydrogen is
the most abundant element in the universe, the supply of hydrogen could likely
be regenerated in situ. ·
The VASIMR is flexible
and adaptable to both fast transfers of humans and slower high-payload robotic
missions; hence, there would be no need to develop separate propulsion systems
for missions of each type, and costs would be held down accordingly. Long-range benefits
could be derived from the continued development of the VASIMR. The VASIMR can
be expected to pave the way for fusion-driven plasma rockets. In addition,
because the VASIMR is a high-Isp rocket, the VASIMR concept
can be expected to lead to lower initial mass in low Earth orbit, relative to
nuclear, thermal, and/or chemical rockets. This work was done by
Franklin R. Chang-Díaz of Johnson
Space Center. This invention is
owned by NASA, and a patent application has been filed. Inquiries concerning
nonexclusive or exclusive license for its commercial development should be
addressed to the Patent Counsel, Johnson Space Center, (281) 483-0837. Refer to
MSC-23041. Pictures: Screenshots: Video Project
status: Paused. Release date: 23 January 2008 Future
development:
Version 1.02 is almost ready with some new features: Sources:
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