Ex-Astronaut Developing Plasma Rocket To Revitalize NASA

TechReviewAl writes "Former astronaut Franklin Chang Diaz believes that the private sector can revitalize NASA, and his company is developing a plasma rocket to back up that claim. Chang Diaz argues that private industry can be used to develop much of the basic technology needed for space exploration, allowing NASA to focus on more sophisticated and critical components. His company, Ad Astra, is developing a variable specific impulse magnetoplasma rocket (VASIMR) that will be used to reposition the International Space Station. Last week, the rocket passed an important milestone in testing — reaching 200 kilowatts (enough to move the ISS). A video of the rocket can be seen on Ad Astra's site."

Comments

Summary is incorrect

[Tekfactory]

Since the ISS only has 120-130 Kilowatts of Solar Panels, running a 200 Kilowatt motor would be difficult.

Also Kilowatts though stated in the article aren't really a measure of thrust.

The engine can operate at different levels UP TO 200 kW, but would probably have to use about half that because of the stations limitations. Though if the Motor can use waste hydrogen from the Fuel Cells/Ox Generators they are estimating it would save NASA bringing up fuel for reboosts. (From the Proposal/white paper on VASIMR)

Re:Summary is incorrect

[Tekfactory]

VASIMR can fire for up to 10 minutes at 200 kW using trickle charged batteries.

http://spacefellowship.com/2008/12/13/nasa-and-ad-astra-rocket-company-sign-agreement-for-flight-test-of-the-vasimr-rocket-engine-aboard-the-international-space-station/

Re:Summary is incorrect

[ender06]

Since the ISS only has 120-130 Kilowatts of Solar Panels, running a 200 Kilowatt motor would be difficult.

I am sorry to go on a rant about this, but as someone who works on solar power on a daily basis, I am sick of people assuming that since something uses solar power to generate the electricity, that it will only work when the sun is shining. Ever heard of batteries? Do you honestly think that the ISS is up there, without batteries, which allow a system to draw more instantaneous power than the solar panels can supply, but can be recharged later when the system isn't drawing so much power?

I worked on the solar array for the University of Michigan Solar Car Team and people always thought that they were so clever when they said that it can only run when the sun is shining. God forbid a solar car or anything else solar powered have a battery!

Re:Summary is incorrect

[Bruce Perens]

This kind of thruster doesn't have electrodes, and there's a magnetic bottle so that the ionized plasma doesn't touch the engine.

Perspective

[LaminatorX]

If you measure distance in terms of transit times, the sustainable thrust potential of this technology would make the Solar System the same size to travelers as the Earth was during the Age of Sail.

Re:They've been working on this for a while now

[Sebilrazen]

AFAIK they have been working on VASIMR for over a decade now... This isn't exactly "news"

I think you're mistaken, "news" and "new" aren't the same thing. If you're pining for something "new" in this "news" it's the fact that they passed a significant milestone last week.

Note: If English isn't your first language and you're mistaking "news" as the plural of "new" (which usually doesn't have a plural as it's not generally used as a noun) disregard.

Re:"200Kw, which is enough to move the ISS"

[vlm]

Can't any amount of power move the ISS just at a slower rate?

Kind of. It has to boost altitude, on average, more than 200 meters per day, just to keep up. Over and above that, yes anything will do.

There is also a scheduling issue. Currently they burn chemical thrusters every month for a couple hours. That means no "microgravity environment" for less than 1% of the time. That is OK, 99% of the time is good enough for experiments, etc. Now, if the fancy new vasmir can only boost 400 meters per 24 hours of continuous operation, then just to keep up with atmospheric drag, it absolutely must run 1/2 of the time, meaning you only get that fancy microgravity environment for 1/2 of the time. Also with respect to maintenance and reliability, that means it has to be operational about half the time or better. And finally, a 1% of the time activity means direct astronaut operation/intervention is possible, but there is not the staffing to baby sit a low thrust engine literally half the time, so it has to be highly automated.

http://web.archive.org/web/20080213164432/http://pdlprod3.hosc.msfc.nasa.gov/D-aboutiss/D6.html

"Reboost mode is necessary because the Station's large cross-section and low altitude causes its orbit to decay due to atmospheric drag at an average rate of 0.2 km/day (0.1 n mi/day)."

Re:Really?

[LaminatorX]

While 180 day circumnavigation is possible, the travelers of the 16th-18th Centuries usually took three to four years to circle the globe. That's the basis for the comparison I was making.

Re:"200Kw, which is enough to move the ISS"

[vlm]

If you, on the other hand, had a tiny thruster operating 100% of the time that kept the ISS in its perfect orbit, wouldn't that mean a BETTER microgravity environment, not a worse one?

In theory, yes, but in practice, good luck.

Then you need 100% reliability or 100% redundancy. I would guess they'll require the engines to be shut off during spacewalks, maybe while the shuttle is docked (who knows what effect fumes could have on the tiles, etc). Conveniently you'll need multiple separate engine systems for reliability, so after the spacewalk you just light off both primary AND backup. True 100% operation and true 100% microgravity is unlikely.

Not to mention whatever outgassing and optical effects the thrusters might have. If you only burn a chemical thruster 1% of the time every month or two, you can schedule optical and materials testing in the weeks up to a burn without interference.

Finally you would need 100% power all the time, meaning pretty much nuclear is the only option. Either that or drain the batteries in the dark and charge them in the light, with a cycle every 1.5 hours. Icky. From an electrical standpoint, better off running the thruster only in the sunlight only on excess capacity after the batteries are topped off. I'm guessing that would be about a 10% duty cycle, about ten minutes every hour and a half, although it obviously depends on solar power available and to some extent on thrust required.

Re:"200Kw, which is enough to move the ISS"

[Cold hard reality]

It isn't a stupid question, and yes, by counteracting drag thrust can get you to true freefall.