Variable specific impulse magnetoplasma rocket
Encyclopedia
The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an electro-magnetic thruster for spacecraft propulsion
. It uses radio waves
to ionize
and heat a propellant
and magnetic field
s to accelerate the resulting plasma
to generate thrust
. It is one of several types of spacecraft electric propulsion systems.
The method of heating plasma
used in VASIMR was originally developed as a result of research into nuclear fusion
. VASIMR is intended to bridge the gap between high-thrust
, low-specific impulse
propulsion systems and low-thrust, high-specific impulse systems. VASIMR is capable of functioning in either mode. Costa Rican scientist and former astronaut Franklin Chang-Diaz created the VASIMR concept and has been working on its development since 1977.
, the microwave arcjet, or the pulsed inductive thruster
class. It can also be seen as an electrodeless version of an arcjet, able to reach higher propellant temperature by limiting the heat flux from the plasma to the structure. Neither type of engine has any electrode
s. The main advantage of such designs is elimination of problems with electrode erosion that cause rival designs of ion thruster
s which use electrodes to have a short life expectancy. Furthermore, since every part of a VASIMR engine is magnetically shielded and does not come into direct contact with plasma, the potential durability of this engine design is greater than other ion/plasma engine designs.
The engine design encompasses three parts: turning gas into plasma via helicon
RF antennas; energizing plasma via further RF heating in an ion cyclotron resonance frequency (ICRF) booster; and using electromagnets to create a magnetic nozzle to convert the plasma's built-up thermal energy into kinetic force. By varying the amount of energy dedicated to RF heating and the amount of propellant delivered for plasma generation VASIMR is capable of either generating low-thrust, high-specific impulse exhaust or relatively high-thrust, low-specific impulse exhaust.
VASIMR does not use electrodes and magnetically shields plasma from most of the hardware parts, thus eliminating electrode erosion, a major source of wear and tear in ion engines. Compared to traditional rocket engines with very complex plumbing, high performance valves, actuators and turbopumps, VASIMR eliminates practically all moving parts from its design (apart from minor ones, like gas valves), maximizing its long term durability.
However, some new problems emerge, like interaction with strong magnetic fields and thermal management. The relatively large power at which VASIMR operates generates a lot of waste heat, which needs to be channeled away without creating thermal overload and undue thermal stress on materials used.
Powerful superconducting electromagnets, employed to contain hot plasma, generate tesla
-range magnetic fields. They can present problems with other on board devices and also can produce unwanted torque by interacting with the magnetosphere
. To counter this latter effect, the VF-200 will consist of two 100 kW thruster units packaged together, with the magnetic field of each thruster oriented in opposite directions in order to make a zero-torque magnetic quadrapole.
is critical of the VASMIR design listing several serious problems and points out that it is less efficient than other electric based thrusters which are now operational. Zubrin believes that electric propulsion is not the best way to get to Mars and therefore budgets should not be assigned to develop it. His second point of criticism concentrates on lack of suitable power source.
At the Mars Society
2011 Dallas Convention, Zubrin invited the VASIMIR inventor, Dr. Franklin Chang Diaz, to debate the merits of his thruster. Dr. Diaz did not attend to defend his ideas.
After many years researching the concept with NASA, Franklin Chang-Diaz set up the Ad Astra Rocket Company
in January 2005 to begin development of the VASIMR engine. Later that year, the company signed a Space Act Agreement
with NASA
, and were granted control of the Advanced Space Propulsion Laboratory. In this lab, a 50 kW prototype was constructed, and underwent testing in a vacuum chamber. Later, a 100 kW version was developed, and this was followed by a 200 kW prototype. After a long period of rigorous testing in a 150 m3 vacuum chamber, the latest configuration was deemed space-worthy, and it was announced that the company had entered into an agreement to test the engine on the International Space Station
, in or before 2013.
The first VASIMR engine model VX-50 proved to be capable of 0.5 newton (0.112404471556438 lbf) thrust. Published data on the VX-50 engine, capable of processing 50 kW of total radio frequency power, showed thruster efficiency to be 59% calculated as: 90% NA coupling efficiency × 65% NB ion speed boosting efficiency. It was hoped that the overall efficiency of the engine could be increased by scaling up power levels.
Model VX-100 was expected to have a thruster efficiency of 72% by improving the NB ion speed boosting efficiency to 80%. There were, however, additional (smaller) efficiency losses related to the conversion of DC electric current to radio frequency power and also to the superconducting magnets' auxiliary equipment energy consumption. By comparison, 2009 state-of-the-art, proven ion engine designs such as NASA's HiPEP operated at 80% total thruster/PPU
energy efficiency.
Ongoing improvement to the the engine design concentrate on increasing power level which should lead to higher efficiency level.
In September 2011 the Ad Astra Company has published the results of first full scale tests of VX-200 engine. They confirm theoretical predictions measuring thruster efficiency at 72% [+/-9%] at 200kW power level with specific impulse of 4900s with corresponds to trust level of 6N. This represents much higher thrust and power level than any other currently existing prototype of electric propulsion system.
first stage or solid-state high frequency power transmitter - had reached operational status. The key enabling technology, solid-state DC-RF power-processing, has become very efficient reaching up to 98 % efficiency. The helicon discharge uses 30 kWe of radio waves to turn argon
gas into plasma. The remaining 170 kWe of power is allocated for passing energy to, and acceleration of, plasma in the second part of the engine via ion cyclotron resonance heating.
Based on data released from previous VX-100 testing, it was expected that the VX-200 engine would have a system efficiency of 60-65 % and thrust level of 5 N. Optimal specific impulse
appeared to be around 5000s using low cost argon propellant. The specific power estimated at 1.5 kg/kW meant that this version of the VASIMR engine would weigh only about 300 kg. One of the remaining untested issues was potential vs actual thrust; that is, whether the hot plasma actually detached from the rocket. Another issue was waste heat management (60 % efficiency
means about (100 %-60 %)/100 %*200 kW = 80 kW of unnecessary heat) critical to allowing for continuous operation of VASIMR engine.
Between April and September 2009, tests were performed on the VX-200 prototype with fully integrated 2 Tesla
superconducting magnets. They successfully expanded the power range of the VASIMR up to its full operational capability of 200 kW.
During November 2010, long duration, full power firing tests were performed with the VX-200 engine reaching the steady state operation for 25 seconds thus validating basic design characteristics.
Results presented to NASA and academia in January 2011 have confirmed that the design point for optimal efficiency on the VX-200 is 50 km/s exhaust velocity, or an Isp
of 5000 s. Based on these data, thruster efficiency of 70 % has been deemed by Ad Astra to be achievable, yielding an overall system efficiency (DC electricity to thruster power) of 60 % (since the DC to RF power conversion efficiency exceeds 95 %).
to arrange the placement and testing of a flight version of the VASIMR, the VF-200, on the International Space Station
(ISS). , its launch is anticipated to be in 2014, though it may be later. The Taurus II
has been reported as the "top contender" for the launch vehicle. Since the available power from the ISS is less than 200 kW, the ISS VASIMR will include a trickle-charged battery system allowing for 15 min pulses of thrust.
Testing of the engine on ISS is valuable because it orbits at a relatively low altitude
and experiences fairly high levels of atmospheric drag, making periodic boosts of altitude necessary. Currently, altitude reboosting by chemical rockets fulfills this requirement. If the tests of VASIMR reboosting of the ISS goes according to plan, the increase in specific impulse could mean that the cost of fuel for altitude reboosting will be one-twentieth of the current $210 million annual cost. Hydrogen
generated by the ISS as a by-product is currently vented into space but will be redirected to the VASIMR to act as the fuel in place of the current Argon.
s so that no net rotational torque
is applied to the space station when the thrusters are firing. The VF-200-1 is the first flight unit and will be tested in space attached to the ISS.
VASIMR is not suitable to launch payloads from the surface of the Earth due to its low thrust-to-weight ratio and its need of a vacuum to operate. Instead, it would function as an upper stage for cargo, reducing the fuel requirements for in-space transportation. The engine is expected to perform the following functions at a fraction of the cost of chemical technologies:
Other applications for VASIMR such as the rapid transportation of people to Mars would require a very high power, low mass energy source, such as a nuclear reactor (see nuclear electric rocket
). NASA Administrator Charles Bolden
said that VASIMR technology could be the breakthrough technology that would reduce the travel time on a Mars mission from months to days.
In August 2008, Tim Glover, Ad Astra director of development, publicly stated that the first expected application of VASIMR engine is "hauling things [non-human cargo] from low-Earth orbit to low-lunar orbit" supporting NASA's return to Moon efforts.
An orbital transfer vehicle (OTV) — essentially a "space tug" — powered by a single VF-200 engine would be capable of transporting about 7 metric tons of cargo from low Earth orbit
(LEO) to low Lunar orbit (LLO) with about a six month transit time. NASA envisages delivering about 34 metric tons of useful cargo to LLO in a single flight with a chemically propelled vehicle. To make that trip, about 60 metric tons of LOX-LH2 propellant would be burned. A comparable OTV would need to employ 5 VF-200 engines powered by a 1 MW solar array. To do the same job, such OTV would need to expend only about 8 metric tons of argon propellant. Total mass of such electric OTV would be in the range of 49 t (outbound & return fuel: 9 t, hardware: 6 t, cargo 34 t). The OTV transit times can be reduced by carrying lighter loads and/or expending more argon propellant with VASIMR throttled down to lower Isp. For instance, an empty OTV on the return trip to Earth covers the distance in about 23 days at optimal specific impulse of 5,000 s (50 kN·s/kg) or in about 14 days at Isp of 3,000 s (30 kN·s/kg). The total mass of the NASA specs' OTV (including structure, solar array, fuel tank, avionics, propellant and cargo) was assumed to be 100 metric tons (98.4 long tons; 110 short tons) allowing almost double the cargo capacity compared to chemically propelled vehicle but requiring even bigger solar arrays (or other source of power) capable of providing 2 MW.
, Ad Astra Rocket Company
is working toward utilizing VASIMR technology for space tug
missions to help "clean up the ever-growing problem of space trash." They hope to have a first-generation commercial offering by 2014.
NASA documents
Spacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...
. It uses radio waves
Radio waves
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves,...
to ionize
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
and heat a propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
and magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
s to accelerate the resulting plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
to generate thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
. It is one of several types of spacecraft electric propulsion systems.
The method of heating plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
used in VASIMR was originally developed as a result of research into nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
. VASIMR is intended to bridge the gap between high-thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
, low-specific impulse
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
propulsion systems and low-thrust, high-specific impulse systems. VASIMR is capable of functioning in either mode. Costa Rican scientist and former astronaut Franklin Chang-Diaz created the VASIMR concept and has been working on its development since 1977.
Design and operation
The Variable Specific Impulse Magnetoplasma Rocket, sometimes referred to as the Electro-thermal Plasma Thruster or Electro-thermal Magnetoplasma Rocket, uses radio waves to ionize and heat propellant, which generates plasma that is accelerated using magnetic fields to generates thrust. This type of engine is electrodeless and as such belongs to the same electric propulsion family (while differing in the method of plasma acceleration) as the electrodeless plasma thrusterElectrodeless plasma thruster
The electrodeless plasma thruster is a spacecraft propulsion engine. It was created by Mr. Gregory Emsellem based on technology developed by French Atomic Energy Commission scientist Dr Richard Geller and Dr...
, the microwave arcjet, or the pulsed inductive thruster
Pulsed inductive thruster
Pulsed inductive thrusters are a form of ion thruster, used in spacecraft propulsion. A PIT uses perpendicular electric and magnetic fields to accelerate a propellant. A nozzle releases a puff of gas which spreads across a flat induction coil of wire about 1 meter across...
class. It can also be seen as an electrodeless version of an arcjet, able to reach higher propellant temperature by limiting the heat flux from the plasma to the structure. Neither type of engine has any electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
s. The main advantage of such designs is elimination of problems with electrode erosion that cause rival designs of ion thruster
Ion thruster
An ion thruster is a form of electric propulsion used for spacecraft propulsion that creates thrust by accelerating ions. Ion thrusters are categorized by how they accelerate the ions, using either electrostatic or electromagnetic force. Electrostatic ion thrusters use the Coulomb force and...
s which use electrodes to have a short life expectancy. Furthermore, since every part of a VASIMR engine is magnetically shielded and does not come into direct contact with plasma, the potential durability of this engine design is greater than other ion/plasma engine designs.
The engine design encompasses three parts: turning gas into plasma via helicon
Helicon (physics)
A helicon is a low frequency electromagnetic wave that can exist in plasmas in the presence of a magnetic field. The first helicons observed were atmospheric whistlers, but they also exist in solid conductors or any other electromagnetic plasma....
RF antennas; energizing plasma via further RF heating in an ion cyclotron resonance frequency (ICRF) booster; and using electromagnets to create a magnetic nozzle to convert the plasma's built-up thermal energy into kinetic force. By varying the amount of energy dedicated to RF heating and the amount of propellant delivered for plasma generation VASIMR is capable of either generating low-thrust, high-specific impulse exhaust or relatively high-thrust, low-specific impulse exhaust.
Benefits and drawbacks of design
In contrast with usual cyclotron resonance heating processes, in VASIMR ions are immediately ejected through the magnetic nozzle, before they have time to achieve thermalized distribution. Based on novel theoretical work in 2004 by Arefiev and Breizman of UT-Austin, virtually all of the energy in the ion cyclotron wave is uniformly transferred to ionized plasma in a single-pass cyclotron absorption process. This allows for ions to leave the magnetic nozzle with a very narrow energy distribution, and for significantly simplified and compact magnet arrangement in the engine.VASIMR does not use electrodes and magnetically shields plasma from most of the hardware parts, thus eliminating electrode erosion, a major source of wear and tear in ion engines. Compared to traditional rocket engines with very complex plumbing, high performance valves, actuators and turbopumps, VASIMR eliminates practically all moving parts from its design (apart from minor ones, like gas valves), maximizing its long term durability.
However, some new problems emerge, like interaction with strong magnetic fields and thermal management. The relatively large power at which VASIMR operates generates a lot of waste heat, which needs to be channeled away without creating thermal overload and undue thermal stress on materials used.
Powerful superconducting electromagnets, employed to contain hot plasma, generate tesla
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
-range magnetic fields. They can present problems with other on board devices and also can produce unwanted torque by interacting with the magnetosphere
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...
. To counter this latter effect, the VF-200 will consist of two 100 kW thruster units packaged together, with the magnetic field of each thruster oriented in opposite directions in order to make a zero-torque magnetic quadrapole.
Criticisms of VASIMR
Robert ZubrinRobert Zubrin
Robert Zubrin is an American aerospace engineer and author, best known for his advocacy of the manned exploration of Mars. He was the driving force behind Mars Direct—a proposal intended to produce significant reductions in the cost and complexity of such a mission...
is critical of the VASMIR design listing several serious problems and points out that it is less efficient than other electric based thrusters which are now operational. Zubrin believes that electric propulsion is not the best way to get to Mars and therefore budgets should not be assigned to develop it. His second point of criticism concentrates on lack of suitable power source.
At the Mars Society
Mars Society
The Mars Society is an international space advocacy non-profit organization dedicated to promoting the human exploration and settlement of the planet Mars. It was founded by Robert Zubrin and others in 1998 and attracted the support of notable science fiction writers and filmmakers, including Kim...
2011 Dallas Convention, Zubrin invited the VASIMIR inventor, Dr. Franklin Chang Diaz, to debate the merits of his thruster. Dr. Diaz did not attend to defend his ideas.
Research and development
Ad Astra Rocket Company
The Ad Astra Rocket Company is a rocket propulsion company dedicated to the development of advanced plasma rocket propulsion technology. Located in Webster, Texas, several miles from NASA's Johnson Space Center, the company was incorporated on January 14, 2005. The President and CEO of Ad Astra...
in January 2005 to begin development of the VASIMR engine. Later that year, the company signed a Space Act Agreement
Space Act Agreement
Space Act Agreement is a type of legal agreement specified in the National Aeronautics and Space Act that established NASA. Agreements of this type have been reached under the Commercial Orbital Transportation Services and Commercial Crew Development programs are examples of Space Act agreements...
with NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, and were granted control of the Advanced Space Propulsion Laboratory. In this lab, a 50 kW prototype was constructed, and underwent testing in a vacuum chamber. Later, a 100 kW version was developed, and this was followed by a 200 kW prototype. After a long period of rigorous testing in a 150 m3 vacuum chamber, the latest configuration was deemed space-worthy, and it was announced that the company had entered into an agreement to test the engine on the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...
, in or before 2013.
The first VASIMR engine model VX-50 proved to be capable of 0.5 newton (0.112404471556438 lbf) thrust. Published data on the VX-50 engine, capable of processing 50 kW of total radio frequency power, showed thruster efficiency to be 59% calculated as: 90% NA coupling efficiency × 65% NB ion speed boosting efficiency. It was hoped that the overall efficiency of the engine could be increased by scaling up power levels.
Model VX-100 was expected to have a thruster efficiency of 72% by improving the NB ion speed boosting efficiency to 80%. There were, however, additional (smaller) efficiency losses related to the conversion of DC electric current to radio frequency power and also to the superconducting magnets' auxiliary equipment energy consumption. By comparison, 2009 state-of-the-art, proven ion engine designs such as NASA's HiPEP operated at 80% total thruster/PPU
Power processing unit
In the context of spacecraft, the power processing unit is a module containing the electrical subsystem responsible for providing electrical power to other parts of the spacecraft...
energy efficiency.
Ongoing improvement to the the engine design concentrate on increasing power level which should lead to higher efficiency level.
In September 2011 the Ad Astra Company has published the results of first full scale tests of VX-200 engine. They confirm theoretical predictions measuring thruster efficiency at 72% [+/-9%] at 200kW power level with specific impulse of 4900s with corresponds to trust level of 6N. This represents much higher thrust and power level than any other currently existing prototype of electric propulsion system.
Development of the 200 kW engine
On October 24, 2008 the company announced that the plasma generation aspect of the VX-200 engine - heliconHelicon (physics)
A helicon is a low frequency electromagnetic wave that can exist in plasmas in the presence of a magnetic field. The first helicons observed were atmospheric whistlers, but they also exist in solid conductors or any other electromagnetic plasma....
first stage or solid-state high frequency power transmitter - had reached operational status. The key enabling technology, solid-state DC-RF power-processing, has become very efficient reaching up to 98 % efficiency. The helicon discharge uses 30 kWe of radio waves to turn argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
gas into plasma. The remaining 170 kWe of power is allocated for passing energy to, and acceleration of, plasma in the second part of the engine via ion cyclotron resonance heating.
Based on data released from previous VX-100 testing, it was expected that the VX-200 engine would have a system efficiency of 60-65 % and thrust level of 5 N. Optimal specific impulse
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
appeared to be around 5000s using low cost argon propellant. The specific power estimated at 1.5 kg/kW meant that this version of the VASIMR engine would weigh only about 300 kg. One of the remaining untested issues was potential vs actual thrust; that is, whether the hot plasma actually detached from the rocket. Another issue was waste heat management (60 % efficiency
Energy conversion efficiency
Energy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat.-Overview:...
means about (100 %-60 %)/100 %*200 kW = 80 kW of unnecessary heat) critical to allowing for continuous operation of VASIMR engine.
Between April and September 2009, tests were performed on the VX-200 prototype with fully integrated 2 Tesla
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
superconducting magnets. They successfully expanded the power range of the VASIMR up to its full operational capability of 200 kW.
During November 2010, long duration, full power firing tests were performed with the VX-200 engine reaching the steady state operation for 25 seconds thus validating basic design characteristics.
Results presented to NASA and academia in January 2011 have confirmed that the design point for optimal efficiency on the VX-200 is 50 km/s exhaust velocity, or an Isp
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
of 5000 s. Based on these data, thruster efficiency of 70 % has been deemed by Ad Astra to be achievable, yielding an overall system efficiency (DC electricity to thruster power) of 60 % (since the DC to RF power conversion efficiency exceeds 95 %).
Testing on the space station
On December 8, 2008, Ad Astra Company signed an agreement with NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
to arrange the placement and testing of a flight version of the VASIMR, the VF-200, on the International Space Station
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...
(ISS). , its launch is anticipated to be in 2014, though it may be later. The Taurus II
Taurus II
Taurus II is an expendable launch system being developed by Orbital Sciences Corporation. It is a two stage vehicle designed to launch payloads weighing up to into low-Earth orbit...
has been reported as the "top contender" for the launch vehicle. Since the available power from the ISS is less than 200 kW, the ISS VASIMR will include a trickle-charged battery system allowing for 15 min pulses of thrust.
Testing of the engine on ISS is valuable because it orbits at a relatively low altitude
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
and experiences fairly high levels of atmospheric drag, making periodic boosts of altitude necessary. Currently, altitude reboosting by chemical rockets fulfills this requirement. If the tests of VASIMR reboosting of the ISS goes according to plan, the increase in specific impulse could mean that the cost of fuel for altitude reboosting will be one-twentieth of the current $210 million annual cost. Hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
generated by the ISS as a by-product is currently vented into space but will be redirected to the VASIMR to act as the fuel in place of the current Argon.
VF-200
The VF-200 flight-rated thruster consists of two VASIMR units with opposite magnetic dipoleMagnetic dipole
A magnetic dipole is the limit of either a closed loop of electric current or a pair of poles as the dimensions of the source are reduced to zero while keeping the magnetic moment constant. It is a magnetic analogue of the electric dipole, but the analogy is not complete. In particular, a magnetic...
s so that no net rotational torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
is applied to the space station when the thrusters are firing. The VF-200-1 is the first flight unit and will be tested in space attached to the ISS.
NASA partnership
, NASA has 100 people assigned to the project to work with Ad Astra to integrate the VF-200 onto the space station.Potential future applications
- drag compensation for space stations
- lunar cargo delivery
- satellite repositioning
- satellite refueling, maintenance and repair
- in space resource recovery
- ultra fast deep space robotic missions
Other applications for VASIMR such as the rapid transportation of people to Mars would require a very high power, low mass energy source, such as a nuclear reactor (see nuclear electric rocket
Nuclear electric rocket
In a nuclear electric rocket, nuclear thermal energy is changed into electrical energy that is used to power one of the electrical propulsion technologies. Technically the powerplant is nuclear, not the propulsion system, but the terminology is standard. A number of heat-to-electricity schemes...
). NASA Administrator Charles Bolden
Charles F. Bolden, Jr.
Charles Frank "Charlie" Bolden, Jr. is the current Administrator of NASA, a retired United States Marine Corps major general, and former NASA astronaut....
said that VASIMR technology could be the breakthrough technology that would reduce the travel time on a Mars mission from months to days.
In August 2008, Tim Glover, Ad Astra director of development, publicly stated that the first expected application of VASIMR engine is "hauling things [non-human cargo] from low-Earth orbit to low-lunar orbit" supporting NASA's return to Moon efforts.
Use as a space tug or orbital transfer vehicle
The most important near-future application of VASIMR-powered spacecraft is transportation of cargo. Numerous studies have shown that, despite longer transit times, VASIMR-powered spacecraft will be much more efficient than traditional integrated chemical rockets at moving goods through space.An orbital transfer vehicle (OTV) — essentially a "space tug" — powered by a single VF-200 engine would be capable of transporting about 7 metric tons of cargo from low Earth orbit
Low Earth orbit
A low Earth orbit is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km...
(LEO) to low Lunar orbit (LLO) with about a six month transit time. NASA envisages delivering about 34 metric tons of useful cargo to LLO in a single flight with a chemically propelled vehicle. To make that trip, about 60 metric tons of LOX-LH2 propellant would be burned. A comparable OTV would need to employ 5 VF-200 engines powered by a 1 MW solar array. To do the same job, such OTV would need to expend only about 8 metric tons of argon propellant. Total mass of such electric OTV would be in the range of 49 t (outbound & return fuel: 9 t, hardware: 6 t, cargo 34 t). The OTV transit times can be reduced by carrying lighter loads and/or expending more argon propellant with VASIMR throttled down to lower Isp. For instance, an empty OTV on the return trip to Earth covers the distance in about 23 days at optimal specific impulse of 5,000 s (50 kN·s/kg) or in about 14 days at Isp of 3,000 s (30 kN·s/kg). The total mass of the NASA specs' OTV (including structure, solar array, fuel tank, avionics, propellant and cargo) was assumed to be 100 metric tons (98.4 long tons; 110 short tons) allowing almost double the cargo capacity compared to chemically propelled vehicle but requiring even bigger solar arrays (or other source of power) capable of providing 2 MW.
, Ad Astra Rocket Company
Ad Astra Rocket Company
The Ad Astra Rocket Company is a rocket propulsion company dedicated to the development of advanced plasma rocket propulsion technology. Located in Webster, Texas, several miles from NASA's Johnson Space Center, the company was incorporated on January 14, 2005. The President and CEO of Ad Astra...
is working toward utilizing VASIMR technology for space tug
Unmanned resupply spacecraft
Unmanned resupply spacecraft are a special kind of robotic spacecraft that operate autonomously without a human crew, designed to support space station operation...
missions to help "clean up the ever-growing problem of space trash." They hope to have a first-generation commercial offering by 2014.
See also
- Electrodeless plasma thrusterElectrodeless plasma thrusterThe electrodeless plasma thruster is a spacecraft propulsion engine. It was created by Mr. Gregory Emsellem based on technology developed by French Atomic Energy Commission scientist Dr Richard Geller and Dr...
- Helicon Double Layer ThrusterHelicon Double Layer ThrusterThe Helicon Double Layer Thruster is a prototype spacecraft propulsion engine. It was created by Australian scientist Dr. Christine Charles, based on a technology invented by Professor Rod Boswell, both of the Australian National University....
- Magnetoplasmadynamic thrusterMagnetoplasmadynamic thrusterThe Magnetoplasmadynamic thruster is a form of electrically powered spacecraft propulsion which uses the Lorentz force to generate thrust...
- Ion thrusterIon thrusterAn ion thruster is a form of electric propulsion used for spacecraft propulsion that creates thrust by accelerating ions. Ion thrusters are categorized by how they accelerate the ions, using either electrostatic or electromagnetic force. Electrostatic ion thrusters use the Coulomb force and...
- Pulsed plasma thrusterPulsed plasma thrusterPulsed plasma thrusters are a method of spacecraft propulsion also known as Plasma Jet Engines in general. They use an arc of electric current adjacent to a solid propellant, to produce a quick and repeatable burst of impulse...
- Solar panels on spacecraftSolar panels on spacecraftSpacecraft operating in the inner solar system usually rely on the use of photovoltaic solar panels to derive electricity from sunlight. In the outer solar system, where the sunlight is too weak to produce sufficient power, radioisotope thermal generators are used as a power source.-History:The...
- Spacecraft propulsionSpacecraft propulsionSpacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...
- List of plasma (physics) applications articles
External links
- Ad Astra Rocket Company
- Comparison between the different types of rocket propulsion - Astra Rocket Company's technology section
- http://science.discovery.com/videos/brink-package-plasma-rocket.htmlVideo about the VASIMR rocket on the Science Channel BrinkBrink (television series)Brink, stylized as brink., was an American news documentary television series that was produced by CBS Eye Too Productions for the Science Channel and that originally aired from November 28, 2008 to August 25, 2009...
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NASA documents