Next Generation Ion Thruster that has recently achieved long duration test milestone of operating for 46,000 hours at NASA Glenn Research Center. Credit: NASA Glenn Research Center, Cleveland, Ohio
Could there be a time in the future whereby, we could pull an asteroid out of the heavens, place it in a stable orbit and explore it?
We may be looking more at something straight out of a science fiction movie but, as we stare into the cool, blue glow, made up of Xenon gas within NASA's new ion propulsion engine; science fiction looks as though it's becoming a reality.
'NASA's New Solar Electric Propulsion Engine'
The technology is part of NASA's Asteroid Retrieval Initiative, with the task of robotically pulling asteroids that are close to Earth and stabilizing them within an orbit, which we could actually explore.
Still an unapproved plan (with the president proposing in the FY14 budget) the concept is really quite spectacular and for one solar technology enthusiast, an extremely interesting insight into the power of the solar electric propulsion system.
The technology can only work in space; high arrays from solar cells taking energy from the sun and using it to generate energy for geosynchronous spacecraft.
Speaking to NASA’s Michael Patterson from the Glenn Research Center in Cleveland, he described the mechanics of solar electric propulsion on board spacecraft as: ‘taking the power available from the sun and converting it into thrust and it does so by using solar arrays that can flux the photons to electrical current and that power is made available to the thrusters’.
Comparing solar technology for space travel to that of what we use here on planet earth, there is quite a difference in terms of the sophistication with the development and production of the solar technology.
Artist Concept of a Solar Electric Propulsion System - Image Credit: Analytical Mechanics Associates
Michael Patterson (Glenn Research Center) states that ‘one of the downsides of solar-electric propulsion is that you have to use the solar arrays and solar arrays are expensive to manufacture and fly although, on the other hand, now that you have these arrays on board spacecraft, once you are done operating a propulsion system that can be made available to the spacecraft to operate payloads and that has been a great marriage for geosynchronous communication satellites’.
He goes onto further state that ‘solar technologies [and] the arrays that are used in space are fairly sophisticated. They are relatively high efficiency cells and many of which are implemented in a very sophisticated fashion. For example; on the Deep Space One mission we flew solar arrays that had [a] concentrator lens over the cells to increase the flux of photons for unit area to increase the power generation of the cells.’
What I do find interesting is that while the cost and the demand is high, perhaps the overall efficiency could potentially outweigh the cost, and, if you have the arrays at a constant angle to the sun, then the potential for a massive amount of energy is there to use with financial benefits either coming from, as Patterson states; ‘allowing you to get on a smaller launch vehicle with significant cost savings [could] be the reduction in class launch vehicle or it could allow you to put more payload in the spacecraft that would generate revenue’.
In terms of what goes into the production of this technology and what the solar cells are made up from, Patterson states that because they are ‘gallium arsenide solar cells [with] arrays that are high efficiency; their radiation [is] hardened and the arrays are articulated to constantly point with a decent sun angle.’
Looking to the future, the potential for harnessing asteroids and exploring them is only still in formulation but, the concept would involve the use of solar electric propulsion technology (with regards to being able to perhaps develop and understand the requirements for human space exploration beyond the earths orbit).
Michael Patterson (Glenn Research Center) discusses the concept as; ‘a high power solar electric propulsion system with [a] high field efficiency [that] would be launched off a very large launch vehicle, and then be able to have enough energy to be able to go out to an earth crossing asteroid [to] capture it - lasso it essentially; and retrieve it back to a stable orbit between the earth and the moon (and that requires a lot of energy and really the only practical way of doing this is with solar electric propulsion). So there’s no real energy constraint because we get our energy continuously from the sun (as opposed to stored energy in the chemical bonds of a chemical rocket)’.
Solar Electric Propulsion technology as a concept used in human space exploration is something which could really be a pathway into learning - not only about the asteroid - but also about exploring how we would deal with space exploration that goes beyond our orbit.
Sure, there is a high cost mixed with high demand and the technology is (and has to be) massively sophisticated. Although, perhaps the long term benefits for space travel using this form of propulsion could see us take the next step in space travel.
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