NASA's Ion Thruster Sets Continuous Operation Record 165
cylonlover writes "NASA's Evolutionary Xenon Thruster (NEXT) ion engine has set a new world record by clocking 43,000 hours of continuous operation at NASA's Glenn Research Center's Electric Propulsion Laboratory. The seven-kilowatt thruster is intended to propel future NASA deep space probes on missions where chemical rockets aren't a practical option. The NEXT is one of NASA's latest generation of engines. With a power output of seven kilowatts, it's over twice as powerful as the ones used aboard the unmanned Dawn space probe, yet it is simpler in design, lighter and more efficient, and is also designed for very high endurance. Its current record of 43,000 hours is the equivalent of nearly five years of continuous operation while consuming only 770 kg (1697.5 lbs) of xenon propellant. The NEXT engine (PDF) would provide 30 million newton-seconds of total impulse to a spacecraft. What this means in simple terms is that the NEXT engine can make a spacecraft go (eventually) very far and very fast."
If I am doing the math right (Score:5, Interesting)
This ion thruster placed on Voyager 1 would have taken it up to 37 km/s over 5 years compared to the 17km/s it is going now. Not part of my calculations is that Voyager 1 would have been slightly lighter due to the reduced fuel load. i don't have exact enough numbers to do the calc, but it would have likely been in the low 40's km/s.
Ion thrusters (Score:4, Interesting)
Re:Cool... (Score:4, Interesting)
Although acceleration is not the same as speed, AC is right. Even if you assume the probe's weight is negligible, you begin to run into issues with thrust to weight of fuel. Over the five years cited in this story, the ion thruster consisting of fuel only would get you to 75km/s, or about a 14,000 year flight to alpha centauri. Scaling up doesn't help much as the ion thruster has to accelerate a larger mass.
Re:Um, they used what? (Score:4, Interesting)
Last I heard, xenon was a gas, and that sure sounds like an awful lot of it - how much is left (on our planet)?
Seriously man.. 770kg shouldnt sound like "an awful lot of it" when you are asking about how much we have "on our planet." You do know how massive the atmosphere is, right?
Extracting a liter of xenon from the atmosphere requires 798000 joules of energy, and 770 kg of xenon is 131804 liters. So thats 104388768000 joules of energy.
(yes, I am shooting for "oh noes big number")
Thats equivalent to under 3 minutes of output of the typical (average American) coal plant that puts out 667MW.
Re:If I am doing the math right (Score:5, Interesting)
Agreed. You can get a lot of energy from solar in the inner solar system, but ion engines are about long durations, and you're not going to be spending that much time in the inner solar system. I guess you could launch it towards the sun and do a slingshot around it. That will let you pick up a lot more velocity due to spending more time where your panels are effective, but it obviously adds a lot more distance to your trip as well.
You could just use a much larger RTG, or perhaps even a reactor. Not sure how that works out in terms of mass trade-off vs just using a conventional rocket.
Re:Cool... (Score:4, Interesting)
Re:Um, they used what? (Score:1, Interesting)
That's about a $1 Million dollars worth of Xenon. Now, if they used mono-isotopic Xenon, they could improve the efficiency probably by a factor of two, which would cut way down on launch and carrying costs. But Xe-136, if it could be gathered in that amount, would cost over a Billion.
As long as I'm throwing millions and billions around, I should point out that the quantity of Xenon available is in the range of millions to billions of Kilograms. It's just difficult and expensive to purify. Unless we let an improperly run Nuclear Reactor make it for us. All the hot isotopes decay away rapidly, into chemically separable daughters, which leaves an enriched Xe-136 feedstock.
(My numbers may be way off; It's been a few years since I worked in those fields. If Xenon looks expensive... I once had to guard and supervise the purification of four grams of Calcium-48. It was, theoretically at least, (We were the only people on Earth using it.), worth about $1 Million a _gram_.)
Re:Cool... (Score:4, Interesting)
> Thinking that a gravity assist can help significantly ...
http://en.wikipedia.org/wiki/Gravity_assist [wikipedia.org]
Right. Most folks, even amateur space enthusiasts like us, don't really understand the gravity "slingshot" and how it works. Some have the idea that you can just accelerate like a demon toward a given planet or moon, whip around it and somehow gain all sorts of new velocity. That's not so.
What you will gain is part of the orbital velocity of the object that you're "slingshotting" around. Nice boost and it makes a difference -- our space probes use it all the time -- but it's not some magical means by which you can accelerate to C-fractional speeds.
Re:If I am doing the math right (Score:1, Interesting)
> I guess you could launch it towards the sun and do a slingshot around it.
No, too much energy! That will make it go faster than is possible in normal space, i.e. faster than the speed of light, and thus throw it back in time.
Previous to this discovery, only the mysterious energies released in a warp core cold start implosion could make you go faster than light while still in normal space.
Re:Cool... (Score:4, Interesting)
Trying to work a project for 700 years would also inevitably land you in the position of launching something that is 300 years newer that would pass your 300 year old probe long before it got to it's destination, because propulsion tech is 300 years better.
I mean, 700 years ago was 150 years before Copernicus created his heliocentric model of the solar system, and was lambasted for it. Now we've got probes on their way out of the solar system that he was mostly correct about.
Re:If I am doing the math right (Score:3, Interesting)
Only problem is coming up with a multi-kilowatt electrical source that far out in space
SAFE-30 [wikipedia.org] nuclear reactor. In fact the Jupiter Icy Moons Orbiter [wikipedia.org] (JIMO) was planned to use nuclear-electric propulsion to explore the moons of Jupiter but it was cancelled. Another possibility if you want to stay in the inner planets i.e. not go further than Mars is to use a gigantic solar panel array. The 8 ISS solar arrays generate 84 kW.