The drive to have new types of propulsion, such as plasma engines and ion thrusters, on current and future space missions brings up an interesting dilemma for mission planners…
If you want to go into deep space and you want to fly for long periods of time you are going to need fuel and power.
But where does it come from?
The big issue for any deep space missions and especially ion thruster or plasma engine missions is that you don’t have the Sun to power you…
So you look for other alternatives: nuclear is the best possibility…but this has its own challenges in that you have to launch a reactor, no matter how small, into space. The Prometheus idea by NASA was one such mission scenario.
There is always the possibility of…
What happens if the rocket blows up on the pad?
For fuel it is little better: most ion thrusters currently use rare gases, such as xenon or argon, and these are not in abundant supply on Earth. Maybe there would be better chances of finding them on other planets. But this doesn’t solve the future dilemma.
So while current missions can use them what about future missions in the next 10 to 15 years?
Is there a realistic plasma engine option then?
One possibility that has received a lot of interest and development, not only for its unmanned potential, but also for the ability to one day get men to other planets in the Solar System, is the VASIMR.
VASIMR is a Variable Specific Impulse Magnetoplasma Rocket, a type of electrode-less ion thruster that uses magnetic fields and radio waves to produce and guide a plasma through a nozzle, not unlike a jet engine.
An advantage of the VASIMR for deep space missions is that it uses hydrogen. Hydrogen can be found in the solar system and interstellar clouds, so for ultra deep space missions there is the possibility of refuelling.
The rocket uses a lot of power though…in the 50 to 200 kW range which is an order of magnitude higher than the combined thrusters used for Hayabusa or BepiColombo. So at the moment this means making a good size efficient nuclear fission reactor that can be safely launched and possibly assembled in space.
And that brings us back to the thorny issue: the thought of nuclear fission devices in space. It is still a controversial one…but it may be the only option.
So even though there thruster option for deep space missions that can more readily be re-fuelled, it’s the power side of things that can be the show-stopper.
And it will continue like this until moves are made to test nuclear reactors in space.
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