VASIMR Propulsion: Revolutionizing Space Transportation & Exploration

[Astronuc]

Evo brought this to my attention in another thread.

http://www.adastrarocket.com/home.html

OUR VISION:
To revolutionize space transportation and exploration, through the development and commercialization of the VASIMR engine and related technologies

Technology
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.

http://www.adastrarocket.com/vasimr.html

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.

This is basically a plasma device, but there is not thermonuclear reactions. The gas propellant is simply heated by RF heating and passed through a magnetic nozzle.

Cheers, Evo!

 

[Janus]

A couple of years ago, we had a little project here at PF where we planned a sample return mission to Europa. The VASIMR was our propulsion system of choice.

 

[Astronuc]

VASIMR is attractive, but the last I heard about 2 yrs ago was that there was no thrust, or rather insubstantial thrust.

So the technical challenges have been thrust and duration.

With very high Isp, VASIMR would be fine for a small spacecraft , e.g. on the order of 1 MT (1000 kg), and hopefully the thrust would be something like 10-100 N. Even then the acceleration is very low, but it's continuous.

Basically, the force has to exceed the force imposed by the local gravitational field, otherwise the craft is not going anywhere.

Then there is the matter of duration. About 20+ years ago, the benchmark was 7 yrs or ~61,000 hrs (219,600,000 s) of continuous operation. The challenge for many plasma and electrodynamic systems is the erosion of components at temperature, and rates of nm/s add up.

 

[sanman]

VASIMR is attractive, but the last I heard about 2 yrs ago was that there was no thrust, or rather insubstantial thrust.

So the technical challenges have been thrust and duration.

With very high Isp, VASIMR would be fine for a small spacecraft , e.g. on the order of 1 MT (1000 kg), and hopefully the thrust would be something like 10-100 N. Even then the acceleration is very low, but it's continuous.

Basically, the force has to exceed the force imposed by the local gravitational field, otherwise the craft is not going anywhere.

Then there is the matter of duration. About 20+ years ago, the benchmark was 7 yrs or ~61,000 hrs (219,600,000 s) of continuous operation. The challenge for many plasma and electrodynamic systems is the erosion of components at temperature, and rates of nm/s add up.

So you're saying that under ideal conditions, a 1000-kg VASIMR rocket could launch from Earth to orbit? How slow would its acceleration be in Earth's gravity? How long would it take to reach orbit?

 

[Danger]

No way could one of those launch from Earth. It would have to be either assembled in orbit or lifted to orbit by a chemical rocket. It would be the same idea as an ion thruster—small impetus over an extended period of time.

 

[Astronuc]

VASIMR is low thrust, high Isp, so as Danger mentioned, it won't get from Earth's surface to orbit. VASIMR would be applied to a craft already in orbit, whether launched whole from the surface or assembled wholly or partially in orbit.

 

[sanman]

So then what is the solution for very heavy launch payload to orbit, like on the or of a thousand tonnes or more?

 

[Astronuc]

So then what is the solution for very heavy launch payload to orbit, like on the or of a thousand tonnes or more?

Traditional chemical (LOX/LH or LOX/kerosine) as Danger indicated. The Saturn V or NOVA rockets would likely be used, or a Shuttle-derived Launch Vehicle (e.g. Ares) - http://en.wikipedia.org/wiki/Shuttle-Derived_Launch_Vehicle

http://en.wikipedia.org/wiki/Ares_V

http://www.hq.nasa.gov/office/hqlibrary/pathfinders/constellation.htm

 

[Aero Stud]

There are no fundumental problems with VASIMR. The main problem is simply power. For example, just the 10 N thrust version with an Isp as low as 1,000 seconds would require over 50 KW, which is something above 11,000 square feet of solar panels. At this point, unless a nuclear reactor is used, the advantages of using such a system on a large spacecraft are negligible if any.

 

[sanman]

Naturally, I was only considering VASIMR in conjunction with a nuclear power source, as any other power source would be impractical.