VASIMR

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) system encompasses three linked magnetic cells. The "Plasma Source" cell involves the main injection of neutral gas (typically hydrogen, or other light gases) to be turned into plasma and the ionization subsystem. The "RF Booster" cell acts as an amplifier to further energize the plasma to the desired temperature using electromagnetic waves. The "Magnetic Nozzle" cell converts the energy of the plasma into directed motion and ultimately useful thrust.

Coupled with nuclear power this new type of rocket technology could dramatically shorten human transit times between planets (less than 3 months to Mars) and propel robotic cargo missions with a very large payload mass fraction. Trip times and payload mass are major limitations of conventional and nuclear thermal rockets because of their inherently low specific impulse (less than 1000 seconds). Plasma rockets such as VASIMR enable a very high specific impulse (greater than 10,000 seconds.) For these missions VASIMR will operate with hydrogen or deuterium propellant, both are abundant throughout the known universe.

The VASIMR has two additional important features that distinguish it from other plasma propulsion systems:
1. Ability to vary the exhaust characteristics (thrust and specific impulse) in order to optimally match mission requirements. This results in the lowest trip time with the highest payload for a given fuel load.
2. VASIMR is driven by electromagnetic (RF) waves and has no physical material electrodes in contact with the hot plasma. This results in greater reliability and longer life and enables a much higher power density than competing designs.

4-th State of Matter
The first step to understanding how a plasma rocket operates is learning about plasma. A plasma state can be achieved when a substance in its gaseous state is heated to very high temperatures - tens of thousands to millions of degrees. At this temperatures, electrons are stripped, or lost, from the neutral atoms.

In the overheated gas, electrons, which hold a negative charge, and ionized atoms, which hold a positive charge, mixed together making an electrically neutral "soup" of charged particles that is a plasma. This is a very common occurrence in nature. In fact, 99 percent of the visible universe is in some form of a plasma state, including lightning, very hot flames, nebulas, the Sun and other stars. The plasmas at the extreme temperatures required of a plasma rocket cannot be contained by any known material. Fortunately, plasmas can be controlled by a magnetic field.
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Starship: Plasma Shields

Shields For Starships: A Reality?

To protect the occupants from the potentially lethal radiation in space from the Sun, a superconducting ring on board the space craft could produce a magnetic field, or mini-magnetosphere, similar to the Earth's, which would create a 'deflector or plasma shield'.
(Credit: Image courtesy of Royal Astronomical Society)


Cosmic rays and radiation from the Sun itself can cause acute radiation sickness in astronauts and even death. Between 1968 and 1973, the Apollo astronauts going to the moon were only in space for about 10 days at a time and were simply lucky not to have been in space during a major eruption on the sun that would have flooded their spacecraft with deadly radiation. In retrospect Neil Armstrong’s ‘one small step for Man’ would have looked very different if it had.

On the International Space Station there is a special thick-walled room to which the astronauts have had to retreat during times of increased solar radiation. However on longer missions the astronauts cannot live within shielded rooms, since such shielding would add significantly to the mass of the spacecraft, making them much more expensive and difficult to launch. It is also now known that the ‘drip-drip’ of even lower levels of radiation can be as dangerous as acute bursts from the sun.

On the surface of the Earth we are protected from radiation by the thick layers of the atmosphere. And the terrestrial magnetic field extends far into space, acting as a natural ‘force field’ to further protect our planet and deflecting the worst of the energetic particles from the Sun by creating a ‘plasma barrier’.

Now scientists at the Rutherford Appleton Laboratory in Oxfordshire plan to mimic nature. They will build a miniature magnetosphere in a laboratory to see if a deflector shield can be used to protect humans living on space craft and in bases on the Moon or Mars.

In order to work, an artificial mini-magnetosphere on a space craft will need to utilise many cutting edge technologies, such as superconductors and the magnetic confinement techniques used in nuclear fusion.

Thus science is following science fiction once again. The writers of Star Trek realised that any space craft containing humans would need protection from the hazardous effects of cosmic radiation. They envisioned a ‘deflector shield’ spreading out from the Starship Enterprise that the radiation would bounce off. These experiments will help to establish whether this idea could one day become a practical real.
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Astronomers Map Out Planetary Danger Zone
Astronomers Make Detailed Image Of Giant Stellar Nursery
Hubble Space Telescope Reveals The Aftermath Of 'Star Wars'
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