The Specific Variable Impulse Rocket Magnetoplasm ( VASIMR ) is an electromagnetic thruster in development for possible use of spacecraft propulsion. It uses radio waves to ionize and heat the propellant. Then the magnetic field speeds up the resulting plasma to produce a boost (plasma propulsion machine). This is one of several types of electric spacecraft propulsion systems.
The VASIMR method for plasma heating was originally developed from nuclear fusion research. It is intended to bridge the gap between high impulses, low specific impulses and high-pressure low-impulse systems, and is capable of functioning in either mode. Former NASA astronaut Franklin Chang DÃÆ'az created the concept of VASIMR and has developed it since 1977.
VASIMRs units for development and testing are assembled by Ad Astra Rocket Company in Costa Rica.
Video Variable Specific Impulse Magnetoplasma Rocket
Design and operation
VASIMR, sometimes referred to as Electro-thermal Plasma Thruster or Electro-thermal Rocket Magnetoplasma, uses radio waves to ionize and heat the propellant, which is then accelerated with a magnetic field to generate a boost. This machine is not energized, from the same propulsion family as electrodeless plasma thruster, microwave arcjet, or thrust pulsed inductive thruster. This can be regarded as an electrodeless version of an arcjet rocket that can reach higher propellant temperatures by limiting the heat flux from the plasma to the structure. No type of machine uses electrodes; this eliminates the erosion of the electrode that shortens the life of the other thruster ion designs. Since each part of the VASIMR engine is magnetically shielded and indirectly contacts the plasma, the engine's durability is predicted to be larger than many other ion/plasma machines.
VASIMR has been described as a convergent-diverging nozzle for ions and electrons. Propellant (a neutral gas such as argon or xenon) is injected into a vacuum cylinder that appears with an electromagnet. Upon entering the engine, the first gas is heated to a "cold plasma" by an RF helical antenna (also known as a "coupler") that bombards the gas with electromagnetic waves, releasing electrons from the propellant atoms and generating the ion plasma. and loose electrons that flow down the engine compartment. By varying the amount of energy dedicated to RF heating and the amount of propellant delivered for plasma generation, VASIMR is capable of producing low impulse impulses, high-specific impulse or relatively high, special low impulse exhaust. The second phase of the machine is a strong electromagnet positioned to compress the ionized plasma in the same way as the convergent-divergent nozzle that suppresses the gas in a traditional rocket engine.
The second coupler, known as the Ion Cyclotron Heating (ICH) section, emits electromagnetic waves in resonance with ion orbit and electrons as they travel through the machine. Resonance is achieved by reducing the magnetic field in this part of the machine that retards the orbital movement of the plasma particles. This section further heats the plasma to more than 1,000,000 kelvins - about 173 times the surface temperature of the Sun.
The ion and electron lines through the machine approach the line parallel to the machine wall; However, the particles actually orbit the stripes while traveling in a linear fashion through the machine. The final, divergent, part of the machine contains an expanding magnetic field that pushes the ions and electrons in a spiral that extends and removes them from the engine, parallel to and contrary to the direction of motion at a speed of 50,000 m/s.
Advantages and Disadvantages
In contrast to typical cyclotron resonance heating processes, the VASIMR ion is immediately removed from the magnetic nozzle before it reaches the thermal distribution. Based on a new theoretical work in 2004 by Alexey V. Arefiev and Boris N. Breizman of the University of Texas at Austin, nearly all the energy in ionic cyclotron waves is transferred uniformly to the ionized plasma in a single cyclotron absorption process. This allows the ion to leave a magnetic nozzle with a very narrow energy distribution, and for a significantly simplified and compact magnetic arrangement in the machine.
VASIMR does not use electrodes; instead, magnetically protects the plasma from most parts of the hardware, thereby eliminating the erosion of the electrode, the main source of wear in the ion machine. Compared to traditional rocket engines with very complex pipes, high performance valves, actuators and turbopumps, VASIMR has virtually no moving parts (other than small ones, such as gas valves), maximizing long-term durability.
However, new problems arise, such as interactions with strong magnetic fields and thermal management. The relatively large power in which the VASIMR operates generates the great waste heat that needs to be funneled without creating thermal overload and thermal stress. Strong superconducting electromagnets, which are required to contain hot plasma, produce a tesla-range magnetic field that can cause problems with other onboard devices and generate undesirable torque by interaction with the magnetosphere. To counter this last effect, the VF-200 consists of two 100 kW thruster units packed with an opposing-oriented magnetic field, resulting in a zero-torque magnetic quadrupole.
Maps Variable Specific Impulse Magnetoplasma Rocket
Research and development
The first VASIMR experiment was conducted at the Massachusetts Institute of Technology in 1983 on a magnetic mirror plasma device. Significant improvements were introduced to rocket concepts in the 1990s, including the use of a "helicon" plasma source, which replaced the initially imagined plasma rifle and made the rocket completely "without electrodes" - adding durability and longevity. A new patent was awarded in 2002.
In 1995, the Advanced Space Propulsion Laboratory (ASPL) was established at NASA's Lyndon B. Johnson Space Center, at the Sonny Carter Training Facility. The magnetic mirror device is brought from MIT. The first plasma experiment in Houston was conducted with microwave plasma sources. The collaboration was established with the University of Houston, UT-Austin, Rice University and other academic institutions.
In 1998, the first plasma helicon experiment was conducted at ASPL. The VASIMR (VX) 10 experiment in 1998 achieved a 10 kW RF helical output, VX-25 in 2002 of 25 kW, and VX-50 at 50 kW. In March 2000, the VASIMR group was awarded the Rotary National Award for Stellar Space Achievement/Stellar Award. In 2005 a breakthrough was obtained at ASPL including full and efficient plasma production and plasma ion acceleration. The VX-50 proved to be 0.5 Newton (0.1 lbf) of thrust. The data published on the VX-50, capable of 50 kW of total radio frequency power, shows the ICRF (second stage) efficiency to 59% calculated by 90% A efficiency coupling ÃÆ'â € 65% N B increases the efficiency of ion speed.
Ad Astra Rocket Company (AARC) was established on January 14, 2005. On June 23, 2005, Ad Astra and NASA signed the first Space Act Agreement to privatize VASIMR Technology. On July 8, 2005, DÃÆ'az retired from NASA after 25 years. Ad Astra's Board of Directors was formed and DÃÆ'az became chairman and CEO on July 15, 2005. In July 2006, the AARC opened a Costa Rica branch in Liberia on the University of Earth campus. In December 2006, AARC-Costa Rica conducted its first plasma experiment on a VX-CR device, using argon ionic ionisation.
The 100 kilowatt VASIMR experiment was successfully carried out in 2007 and showed efficient plasma production with ionization costs below 100 eV. The plasma VX-100 output triples from the previous record of the VX-50.
The VX-100 model is expected to have N B increasing the 80% efficiency ion speed. In contrast, efficiency losses arise from the conversion of DC electrical currents to radio frequency power and energy consumption of supplementary equipment to superconducting magnets. For comparison, the proven ion engine design in 2009, such as NASA's High Power Electricity (HiPEP) operates at 80% of total thruster/energy efficiency of the PPU.
200 kW machine
On October 24, 2008 the company announced that the plasma generation component of the VX-200 engine - the first level helicon or solid state power frequency transmitter that has reached operational status. Key activation technology, DC-RF solid-state power processing, achieves 98% efficiency. The release of the helicons uses 30 kW radio waves to convert argon gas into plasma. The remaining 170 kW of power is allocated to the plasma acceleration in the second part of the machine, by heating the cyclotron ion resonance.
Based on data from the VX-100 test, it is expected that the VX-200 engine will have a system efficiency of 60-65% and a thrust rate of 5Ã, N. The optimal specific impulse seems to be approximately 5,000s using low cost argon propellant. One of the untested problems is still potential vs. actual thrust - whether the hot plasma is completely detached from the rocket. Another problem is the waste heat management. About 60% of the input energy becomes a useful kinetic energy. Most of the remaining 40% is the secondary ionization of the plasma magnetic field line and the difference of the exhaust. Most of the 40% is waste heat (see energy conversion efficiency). Managing and rejecting waste heat is very important.
Between April and September 2009, tests were performed on a prototype VX-200 with an integrated 2-tesla superconductor magnet. They expanded the VASIMR's power range to an operating capability of 200 kW.
During November 2010, long duration, full power outage tests were performed, reaching steady state operations for 25 seconds and validating basic design characteristics.
The results presented in January 2011 confirmed that the design point for optimal efficiency at VX-200 is the exhaust speed of 50 km/sec, or I sp 5000 s. Based on this data, 72% efficiency is achieved, resulting in overall system efficiency (DC power for driving force) of 60% (because the conversion efficiency of DC to RF power exceeds 95%) with argon propellant.
The 200 kW VX-200 has executed over 10,000 engine discharges in 2013, while demonstrating greater than 70% thruster efficiency - relative to RF power input - with argon propellant at full power.
VF-200
The VF-200 rated thruster consists of two 100-kW VASIMR units with opposite magnetic dipole so no net torque is applied to the space station when the thruster magnet works. VF-200-1 is the first flight unit and is scheduled to be tested in space attached to the ISS.
NASA Partnership
In June 2005, Ad Astra signed its first Space Act Agreement with NASA, which led to the development of VASIMR engines. On December 10, 2007, the AARC and NASA signed the Umbrella Space Act Agreement related to the potential interest of the space agency in the machine. On December 8, 2008, NASA and the AARC signed a Space Treaty Act that could lead to space flight testing on machines on the ISS.
From 2008, Ad Astra is working on the placement and testing of flight versions of the VASIMR Thruster for the International Space Station (ISS). The first related agreement with NASA was signed on December 8, 2008;. initial formal design review takes plaace on 26th June 2013.
On March 2, 2011, Ad Astra and NASA Johnson Space Center signed a Support Agreement to collaborate on research, analysis and development on the operation of space-based cryogenic magnets and electrical propulsion systems currently under development by Ad Astra. In February 2011, NASA has assigned 100 people to the project to work with Ad Astra to integrate the VF-200 into the space station. On December 16, 2013, the AARC and NASA signed the five-year Umbrella Act Act.
However, by 2015 NASA ends its plan to fly the VF-200 to the ISS. A NASA spokesman stated that the ISS "is not the ideal demonstration platform for desired engine performance levels". Ad Astra stated that the VASIMR driving test on ISS will remain an option after future space demonstrations. Working with NASA resumes in 2015 under NASA's NextSTEP program with planning for a vacuum 100 hour test of the VX-200SSTM booster.
Because the power available from the ISS is less than 200 kW, ISS VASIMR will include a battery-charged battery system, allowing for 15 minutes pulse boost. Testing the engine on the ISS will be invaluable, as it orbits at relatively low altitudes and experiences a high level of atmospheric resistance, thus increasing the required height periodically. Currently, the reboosting height by chemical rockets meets these requirements. The VASIMR test on the ISS may lead to the ability to maintain an ISS, or similar space station, in a stable orbit at 1/20 of the estimated cost of approximately $ 210 million/year.
VX-200SS
In March 2015, Ad Astra announced a $ 10 million award from NASA to improve the technological readiness of the next VASIMR engine version, VX-200SS (SS stands for steady state) to meet the needs of space missions.
In August 2016, Ad Astra announced the completion of a milestone for the first year of a 3-year contract with NASA. This will enable the loading of the first high-power plasma from the machine, with the target set to reach 100 Ã, hr and 100 kW by mid 2018. In August 2017, the company reported completing the 2 Years achievement for the plasma rocket engine electric VASIMR. NASA granted approval for Ad Astra to continue into Year 3 after reviewing the completion of the 10-hour cumulative test of the 200SS (TM) rocket at 100 kW.
Potential applications
VASIMR is not suitable for launching loads from the Earth's surface because it has a low thrust-to-weight ratio and requires an ambient vacuum. Instead, the engine will serve as the upper stage for the load, reducing the need for fuel for space transportation. This machine is anticipated to perform the following functions for a small portion of the cost of chemical technology: pull compensation for space stations, cargo shipments of the moon, satellite repositioning, satellite fueling, maintenance and repair, in space resource recovery, and robot missions in space.
Other applications for VASIMR such as the rapid transit of people to Mars will require very high power, low mass energy sources, such as nuclear reactors (see nuclear power rockets). In 2010 NASA administrator Charles Bolden said that VASIMR technology could be a breakthrough technology that would reduce travel time on Mars missions from 2.5 years to 5 months.
In August 2008, Tim Glover, Ad Astra's development director, publicly stated that the first applications expected from VASIMR engines were "transporting [non-human cargo] goods from low-Earth orbit to low-lunar orbit" that support NASA's return to effort of the Moon.
Tension transport/orbital transfer vehicle
The most important short-term application of the VASIMR-powered spacecraft is cargo transport. Research has shown that, in spite of longer transit times, the VASIMR-powered spacecraft will be much more efficient than traditional integrated chemical rockets when moving goods through space. An orbital transfer vehicle (OTV) - essentially a "pull of space" - powered by a single VF-200 engine will be capable of transporting about 7 metric tons of cargo from a low Earth orbit (LEO) into a low Lunar orbit (LLO) with approximately six transit times month.
NASA envisions sending about 34 metric tons of useful cargo to LLO in one flight with chemically driven vehicles. To travel, about 60 metric tons of propellant LOX-LH2 will be removed. Comparable OTV will use 5 VF-200 engines powered by 1 MW solar array. To do the same work, the VASIMR-powered OTV will need to remove only about 8 metric tons of argon propellant. The total mass of such electrical OTV will be in the range 49 Â ° t (outbound fuel & return: 9 Â °, hardware: 6 Â °, cargo 34 Â °).
OTV transit times can be reduced by carrying lighter loads and/or issuing more argon propellant with VASIMR released to higher thrust under inefficient operating conditions (lower sub
In October 2010, Ad Astra Rocket Company targeted a space withdrawal mission to help "clean up the growing garbage problem". In 2016 no such commercial products reach the market.
Mars in 39 days
For a manned journey to "Mars in just 39 days", VASIMR will require the level of electrical power available only by nuclear propulsion (especially nuclear power types) by means of nuclear power in space. Such nuclear fission reactors may use traditional Rankine/Brayton/Stirling conversion machines such as those used by SAFE-400 reactors (Brayton cycles) or Kilopower DUFF reactors (Stirling cycle) to convert heat into electricity. However, vehicles may be better served with non-moving parts and non-steam-based power conversion using thermoelectric thermosel technology (including graphene-based thermal power conversion), pyroelectric, thermophotovoltaic, thermionic magnetohydrodynamic type. The thermoelectric material is also an option to convert heat energy (into black-body radiation and thermal vibrations of kinetic molecules and other particles) into electrical current energy (electrons flowing through the circuit). Avoiding the need for a "football field size radiator" (Zubrin quote) for a "200,000 kilowatt (200 megawatt) reactor with a power density up to 1,000 watts per kilogram" (DÃÆ'az quote) this reactor will require efficient heat dissipation capturing technology. For comparison, Seawolf's nuclear-grade nuclear attack submarines use a 34 megawatt reactor, and Gerald R. Ford class carrier uses the A1B 300 megawatt reactor.
Zubrin Criticism
Marshacked mission adviser Robert Zubrin called VASIMR a hoax, claiming it was less efficient than any other electric propulsion currently operating. He also believes that electric motors are not needed to get to Mars; therefore, the budget should not be assigned to develop it. The second criticism concentrates on the lack of appropriate resources. Ad Astra responded in a press release:
In the near future, using solar-electric power at a rate of 100 kW to 1 MW, VASIMR propulsion can transfer heavy loads to Mars using only one to four first-generation drivers in relatively simple machine architectures. [...] It is very clear that the nuclear reactor technology required for such a mission is not available today and major advances in reactor design and power conversion required.
In response to the VASIMR labeled as a hoax by Zubrin, Ad Astra added a section to their FAQ:
That [hoax claim] was created by someone who has never visited MIT or NASA facilities where the research originated or the Ad Astra Rocket Company lab where the development continues and, even if there is an open invitation. , never bothered to see any prototype fired in a vacuum and review the amount of calibrated and validated data available. It is unclear whether this person has read or understood many articles reviewed and published by colleagues regarding this work.
See also
References
Further reading
External links
- "Rocket Plasma" (Video). Brink . Science. December 18, 2008.
- NASA Documents
- Technical Paper: Rapid Mars Transit with Propagate Plasma Switch-Modulation (PDF)
- Rocket Magnetoplasm Variable-Specific-Impulse (Technical Explanation)
- Advanced Space Propulsion Laboratory: VASIMR
- Future Propulsion System
Source of the article : Wikipedia
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