NASA rocket engine runs 5+ years

[n2doc]

By JAKE ELLISON, SEATTLEPI.COM STAFF
Updated 4:54 pm, Wednesday, June 26, 2013



It's been blasting away since early 2008, a constant thrust for over 48,000 hours, and it's still ready for more, NASA says of its advance ion propulsion engine.

"We will voluntarily terminate this test at the end of this month, with the thruster fully operational. Life and performance have exceeded the requirements for any anticipated science mission," said Michael J. Patterson, principal investigator for NEXT at Glenn, in a press release.

The agency says:

The thruster was developed under NASA's Evolutionary Xenon Thruster (NEXT) Project at NASA's Glenn Research Center in Cleveland. Glenn manufactured the test engine's core ionization chamber. Aerojet Rocketdyne of Sacramento, Calif., designed and built the ion acceleration assembly. ...

The NEXT engine is a type of solar electric propulsion in which thruster systems use the electricity generated by the spacecraft's solar panel to accelerate the xenon propellant to speeds of up to 90,000 mph. This provides a dramatic improvement in performance compared to conventional chemical rocket engines.

http://www.seattlepi.com/national/article/NASA-rocket-engine-runs-5-years-still-not-4623930.php

[leveymg]

1. Anyone estimate how far it would have traveled in five years, depending upon payload?

[Wounded Bear]

4. Well, the quoted article stated.....

30 million newton/seconds. I suppose one could calculate how much acceleration you would get for a given payload from that.

My math is no longer that good.

[muriel_volestrangler]

12. 30 million newton seconds over 5 years is a thrust of about 0.19 N

5 * 365.25 * 24 * 3600 = 1.58*10^8 seconds
30 *10^6 / 1.58*10^8 = 0.19 N

It used 770 kg of propellant; if the empty mass of the rocket is 100 kg, then you should be able to use the formula here: http://www.physicsforums.com/showthread.php?t=476154
D = (Ve / mdot) * (M0 - M * (log(M0 / M) + 1))
where Ve = exhaust velocity (90,000mph, which is 39,000 m/s); mdot = rate of change of mass = 770kg/1.58*10^8s; M0=initial mass with propellant = 870kg; M= final mass=100kg
which, if I've plugged it all in correctly, gives 4.4*10^12 metres. The distance from the Sun to Neptune is about 4.5*10^12 metres, so we'll say "it could have gone from here to Neptune - ignoring gravity".

[tinrobot]

5. Approx 3.94 billion miles.

[Callmecrazy]

7. If your math is right...

That's 2 round trips to Saturn. Pretty good. How long did it take Cassini to get there?

[Posteritatis]

8. Launched on October 15, 1997, and entered orbit on July 1, 2004. (nt)

[Callmecrazy]

9. So 7 years to go one way.

Wow.

[Posteritatis]

10. Yeah, though it was also taking the scenic route

Earth to Saturn via Venus (twice), Earth (again) and Jupiter.

[Callmecrazy]

11. Yep.

Plus a little gravity boost to get up to speed as it passed. I wonder how long it would have taken with an ion engine pushing that much mass? Got the math on that? An ion engine pushing something as heavy as Cassini a billion miles?

[muriel_volestrangler]

13. That looks like you've calculated the distance the exhaust would go in that time

which is not the same as how far a spacecraft with this engine would go. At the very least, you'd need to know the mass of the spacecraft to be able to work it out.

[longship]

2. As soon as I read the title I thought "Must be Ion!"

Very low thrust but high efficiency due to high velocity of the plasma. Plus, the damned things can go forever as long as you have fuel. And apparently a little goes a long way.

[ChairmanAgnostic]

3. considering this is but a prototype, with lots of room for improvement,

this is one hell of an achievement.

[byronius]

6. Totally boss.

Great picture, too.

[caraher]

14. Another way to think about the output of the engine

The article gives the total impulse it could impart to a payload as "30 million-newton-seconds" (in the figure caption). Of course, it had to eject 770 kg of xenon to do this... let's neglect the (nontrivial!) cost of moving the fuel and pretend we have a 1 tonne spacecraft (=1000 kg). 30 million N s of impulse could change the speed of such an object by 30,000 m/s - 67,000 MPH! (Of course, this would be over the course of 5 years...