Ex-Astronaut Developing Plasma Rocket To Revitalize NASA 277
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."
Summary is incorrect (Score:3, Informative)
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)
Perspective (Score:5, Informative)
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.
Ob. Steinbeck (Score:1, Informative)
"Ad Astra Per Alia Porci" -- "To the stars on the wings of a pig". John Steinbeck's personal motto.
Re:Summary is incorrect (Score:5, Informative)
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/ [spacefellowship.com]
Re:Summary is incorrect (Score:3, Informative)
Thrust can be calculated by the power and the ISP:
I think it's something like this:
Thrust=Power*2/(effective velocity)
or
Thrust=Power*2/(ISP*9.81m/s^2)
So, if the power is 200kW and ISP= ~3000s (assuming 100% efficiency, where efficiency is probably more like 65%):
400,000W/(30,000 m/s)=13 Newtons
So, a thrust of 13 Newtons is possible at the low end of ISP. And, actually, thrust decreases with ISP, so ten times higher ISP (30,000s) would be about 1 Newton of thrust at 200kW.
Re:They've been working on this for a while now (Score:5, Informative)
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" (Score:5, Informative)
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 [archive.org]
"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)."
Really? (Score:3, Informative)
I was under the impression that VASMIR was a low-thrust technology (high energy, low propellant mass = high Isp, but normally with low absolute thrust). The proposed 200kW model was expected to have a thrust of 5 Newtons, according to wikipedia. Now, that's nice, but it's on the order of the smallest black powder Estes engines used to fly 50-100gram rockets for fun. It will move a space ship, but it will provide relatively low acceleration.
Since sail circumnavigation of the earth can be done in less than 180 days, it's a bit premature to expect us to circumnavigate the 12 billion kM diameter disc which houses our solar system in anything approaching that kind of time frame. Even if you allow for 1000 of these engines running continuously (all 300 metric tons of engines, plus the 200MW power source, plus the ship, shielding, etc. needed), 5kN is going to take quite a while to bring an interplanetary vessel up to any useful speed.
Don't get me wrong - it's cool technology...but it's still a couple of orders of magnitude from sailing around the world.
Re:Really? (Score:5, Informative)
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:Perspective (Score:3, Informative)
If you measure distance in terms of available air to breathe though it's still much larger.
Really, two years or more in the Age of Sail was a very different thing. You could (and they frequently did) call to a port or some island to get supplies, breathing was free and there were much more options for ending the journey somewhat gracefully while for space travelers going back to Earth and getting safely back to the ground is the one and only option. Space is so much larger and emptier than even the oceans of Earth that you'd need more speed and power to make it small enough for our humble bodies and minds than practical (and often enough even physically possible).
But this does not mean that VASIMIR isn't a great thing. If you keep near enough to the sun and have no tight time constraints and lightweight solar cells this could be very useful. And for a selected few missions it could even be useful for manned spaceflight. Solar-electric Mars missions for example. The Soviets back then have analyzed Mars missions for decades and in the end solar-electric won hands-down even with old-fashioned ion-drives. I have often wondered why NASA didn't end up with the same conclusions and then realized that this never was blue-sky researching, NASA is somewhat pre-occupied with burning chemicals...
BTW, the constant acceleration is for longer manned missions probably very useful, even if very weak. Casting along in free fall for two years is one thing and accelerating all the time with an even very limited sense of direction and "up" and "down" another. Being able to find lost stuff on the ground the next day or so is a very small convenience that may add up after a year or two to a larger one.
Re:Another ex-NASA type trying to cash in (Score:3, Informative)
Okay let's start off with why your nuts.
1. His Astronaut training that he got from NASA would have ZERO to do with a plasma rocket. He would get lots of training on how to operate the Space Shuttle systems and how to try and not die if things went very wrong.
2. His time in the advanced propulsion department might have something to do with with this but NASA doesn't make stuff. They may design stuff but then they have outside companies build the stuff.
In this case he is probably taking a project that was getting less funding than is spent on research of the American Bison flea and is getting outside funding for it. You really don't get rich starting a space technology company. It is a passion for a lot of people and I would say good show and I hope it works.
Re:"200Kw, which is enough to move the ISS" (Score:4, Informative)
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" (Score:3, Informative)
It isn't a stupid question, and yes, by counteracting drag thrust can get you to true freefall.
Re:Summary is incorrect (Score:3, Informative)
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 (Score:4, Informative)
Re:All that is keeping us from space is efficiency (Score:3, Informative)
Rockets are pretty efficient actually.
Their disadvantage is that they have to carry their working fluid with them. To get into orbit you need to gain over 8km/s of horizontal velocity and to do that you want to get above the majority of the atmosphere ASAP - so you quickly leave the area where you could snatch any external substance to use for propulsion.
Space elevators are not an automatic fix either - electric motors require power and to carry the kind of power supply that could lift you up a distance equal to about 5 times the diameter of the Earth would give you much the same engineering problems as a rocket.
Re:Another ex-NASA type trying to cash in (Score:3, Informative)
I'm guessing you're American, or at least a legal resident alien, since you're saying "we paid"
But from your post, I'm also going to guess that you went to private primary, secondary, and higher education schools. Either that or you graciously provide your services to society for no additional cost.
Otherwise, we paid for 90+% of your education and you're churlishly demanding payment for a job that you got because of your education.