Successful Test of Superconducting Plasma Rocket Engine 168
xp65 writes to mention that Ad Astra has successfully tested their VX-200 plasma engine at full power in superconducting conditions, the first time such an engine has been tested at those power levels. "The VX-200 engine is the first flight-like prototype of the VASIMR® propulsion system, a new high-power plasma-based rocket, initially studied by NASA and now being developed privately by Ad Astra. VASIMR® engines could enable space operations far more efficiently than today's chemical rockets and ultimately they could also greatly speed up robotic and human transit times for missions to Mars and beyond."
What terrible timing. (Score:5, Funny)
Damn, this is terrible timing. On the weekend my lady and I were thinking that a new pet name for my penis was due. The current "Superfluidic Particle Accelerating Colossus" was getting a bit stale.
The better half suggested "Superconducting Plasma Rocket Engine". But now that that name is taken we'll have to use our second favourite choice: "Hank".
.
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Re:What terrible timing. (Score:4, Funny)
Since your lady probably has trouble finding it....
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I have a friend like that, no matter all the tall stories he shares, no-one has actually spoken to a girl who has actually let him get it out. Poor guy. It's that bad, we have actually started passing a hat around at work.
Re:What terrible timing. (Score:4, Funny)
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You could name it after your game console, perhaps calling it the Wii Wii.
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I ain't putting that into your xbox bro.
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High Thrust, High Specific Impulse (Isp) (Score:5, Interesting)
For those of you who are unclear on why the VASMIR system is so cool, allow me to give you a brief bit of background. Practically every propulsion method developed to date falls into one of two categories:
1. High thrust, low efficiency
2. Low thrust, high efficiency
Generally how it works is that the more power you get out of engines, the less energy you extract from the fuel. This is the case of chemical fuels like Liquid Hydrogen/Oxygen or Kerosine. These fuels provide the massive amounts of thrust necessary to get off the ground, but they burn through their fuel very quickly. Interestingly, LHOx is more efficient than Kerosine, but it's also harder to get as much raw thrust out of it. That's one of the reasons why Kerosine was the heavy lifter during the space race with the LHOx engines reserved for in-space stages.
On the other side of the coin, you have engines like Ion propulsion. These engines are able to inject incredible amounts of energy into tiny amounts of fuel, thus making them extremely fuel efficient. The only problem is that the amount of thrust is very low. Most of the ion engines that have operated to date produce thrust that matches the weight of a sheet of paper. Definitely not enough for liftoff, but perfect for extended missions in space where constant low thrust provides more velocity over time than the chemical engines which fire once, then coast the rest of the way.
The problem with both types of engines is that neither one gets spacecraft to their destination all that fast. Chemical rockets have the thrust to do it, but you couldn't feasibly build a chemical rocket with enough fuel to get you to another planet in a reasonable amount of time. A nuclear pulse propulsion craft could feasibly get fairly close, but it would just have more power in the intial thrust rather than providing a constant, high power thrust. (Obviously these have been discounted over the difficulties of building a large enough craft without using a nuclear ground launch. Nuclear ground launches are a no-no under current test-ban treaties.)
This is where VASMIR comes in. These engines are incredibly efficient. The specific impulse (measurement of efficiency) is between 3,000-30,000 seconds depending on the configuration and current thrust levels of the engine. This compares favorably with the ~450 seconds of shuttle engines and 3,000-10,000 seconds of Ion thrusters. Meanwhile, the thrust of Ion engines ranges from 90-3,000 mN while the thrust of VASMIR is expected to be ~5000 mN of thrust when tested at 200 kW of power.
What this means is that we may be able to build spacecraft where a trip from LEO to the moon is a daily affair and a trip from LEO to Mars takes only a few months (or less!) vs. the current flight time of nearly a year. The better these engines get (and the more we can put on a craft), the faster those flight times will get!
Re:High Thrust, High Specific Impulse (Isp) (Score:5, Insightful)
Re:High Thrust, High Specific Impulse (Isp) (Score:5, Insightful)
THIS is why we need to go to the Moon and Mars and beyond... it is only through pushing through the boundaries to the unknown that we advance as a species. Otherwise, all we do is sit in self-induced stagnation endlessly trying to perfect ourselves.
I agree, but this is going to be the tough sell over the next 30 years. I know where I work I am drowning a deluge of people who never crack a book, have no curiosity beyond what will happen on the next American Idol, and have no deep thoughts about anything.
Vonnegut (and many others) seem to be right and we seem to be devolving. Endeavours in space and science is how we move forward, but there are less and less people that are interested in anything beyond where they are going to eat tonight. Fighting shallow mindedness is the REAL struggle.
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I so agree with you, one thing to add, right now it's more important to "sound" like you know what your talking about than actually knowing. I also wonder if it isn't because of affluence that most of society in G8 countries tend to be complacent or afraid to loose what they have.
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I so agree with you, one thing to add, right now it's more important to "sound" like you know what your talking about than actually knowing.
[citation needed]...
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I so agree with you, one thing to add, right now it's more important to "sound" like you know what your talking about than actually knowing.
It's even worse than that. You don't even have to sound like you know what you're talking about. You can be a complete dumb ass, and just appeal to people's emotions, and you'll gain a following. Witness Sarah Palin.
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I think you misspelled "Barrack Obama" ... aka "Hopey Changey".
Re:High Thrust, High Specific Impulse (Isp) (Score:5, Funny)
I know where I work I am drowning a deluge of people who never crack a book...
I commend you for your efforts in stamping out illiteracy.
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Let's hope he doesn't get caught.
Re:High Thrust, High Specific Impulse (Isp) (Score:5, Insightful)
Don't get me wrong, fighting shallow mindedness is TOTALLY necessary, but it has always been. There has been no "golden age" where everybody was open-minded and well-educated.
Focus is no substitute for vision. (Score:2)
Focus is no substitute for vision.
"Today's research focuses - has to focus - on incremental improvements. Huge, mindblowing breakthroughs are becoming increasingly rare."
The way to guarantee that you get only incremental improvements rather than huge mind-blowing breakthroughs is to attempt only incremental improvements. Or to quote Robert Browning: "Ah, but a man's reach should exceed his grasp, or what's a heaven for?". One of the worst things IBM, in the person of Louis Gerstner, ever did to itself is
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There are many times more people graduating from schools with skills more advanced than "the 4 Rs", yet the audience for drivel like reality shows is no larger than it has ever been. That increase in education is because of "the 1960s".
Besides, if an acceleration in society's decay exactly correlates with the rise of rightwing "conservatism", then it's more clearly "conservatism's" fault than the liberalism that predated such "conservatism" by many generations. And the audience for drivel more closely corre
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many times more people graduating from schools with skills more advanced than "the 4 Rs"
And what are they graduating in? Law, Finance and Business, all three of which have done major destruction to our country.
if an acceleration in society's decay exactly correlates with the rise of rightwing "conservatism"
If conservatism was so successful, then we wouldn't be living in an entitlement nanny state, and neither California nor the US would be bankrupt.
But you go ahead believing whatever you heard from Rush Li
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Game-shows used to be more popular, and reality shows are usually a type of game-show.
Comparing the $10,000 Pyramid to Survivor???
Certainly college education levels have increased
Sure. There are a lot more lawyers and "business people". It has not made the world a better place...
The fascists or whatever you call the liberal opposition are obviously to blame for not counteracting
Sure they have. But the "liberals" are stronger, because they "care".
the destructive liberalization.
This isn't your great-grandf
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I know where I work I am drowning a deluge of people who never crack a book, have no curiosity beyond what will happen on the next American Idol, and have no deep thoughts about anything.
It's always been like that, at least in my 57 year long life. Actually, most of the women I know are readers, but sadly all they read are romance novels.
At least being a nerd isn't the social stigma it was when I was a teenager, now we're cool. We'd have never gone to the moon in the forst place if it weren't for the Soviet
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Well, if you think about it, humans are made to be efficient: Only do what is really needed.
So nowadays, where there are enough people for it to be very unlikely that the *whole* humanity could become extinct, and where everything is taken care of, people just instinctively wonder, why they should do anything at all... beyond reproducing etc.
So, as I always say: The intelligence on this planet is constant. Only the number of humans grows.
Only when the planet will become overcrowded, and life will become har
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Re:High Thrust, High Specific Impulse (Isp) (Score:4, Interesting)
THIS is why we need to go to the Moon and Mars and beyond... it is only through pushing through the boundaries to the unknown that we advance as a species.
A good way to explain it to the technophobes is this with the Turner Thesis [wikipedia.org], which stated that what made America exceptional was its frontier. And in a lot ways, Turner was right. Continental expansionism (the so-called Manifest Destiny [wikipedia.org]) was the impetus for much technological innovation in North America, including the telegraph, the steam locomotive, etc.
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Neither of which were invented by Americans. Is this an example of your higher standards in college education ?
The Chinese built the trans-continental railway, Irish and Eastern Europeans dug most of the gold out of them thar hills, the British started the plantations and the Africans worked them, the Italians organised your crime a
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We can push ourselves and technology even better if we send robots instead of ugly bags of mostly water.
200 kW (Score:2)
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Re:High Thrust, High Specific Impulse (Isp) (Score:4, Interesting)
" ... but you couldn't feasibly build a chemical rocket with enough fuel ... "
In fact, you can't do it all. There is a theoretical maximum amount of chemical energy/mass
you can achieve. Even when you are able to use this energy at 100% efficiency, the amount of energy required
to move the fuel itself reaches a point at which its payload can go no faster.
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Your post says that VASIMR combines high-thrust with high-specific-impulse.
But the wikipedia article http://en.wikipedia.org/wiki/VASIMR_Engine [wikipedia.org] says instead that VASIMR operates in either high-thrust low-specific impulse mode, or in low-thrust high-specific-impulse mode.
Have I understood this correctly? Which is right?
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It's adjustable. That makes it good. :-P
Cheers
Re:High Thrust, High Specific Impulse (Isp) (Score:5, Interesting)
Both are, to some extent. You (and Wikipedia) are correct in that VASIMR engines can change between high-power and high-efficiency (think of it like changing gears in your car; you're much more fuel-efficient cruising in top gear, but can accelerate much harder in low gear). Indeed, that's a fundamental characteristic of the engine, and explains the first two letters of the acronym (VAriable Specific Impulse Magnetoplasma Rocket). However, the OP is also correct in that VASIMIR engines are extremely efficient in general. Part of this is due to their variability - as with a car, the efficient way to use a rocket is to increase its specific impulse (gear ratio/fuel efficiency) as its speed increases (currently no other rocket engine that I know of can do this). On the other hand, look at the high-end of that specific impulse - it's several times what our best Ion drives produce, while also putting out substantially more thrust. Theoretically, VASIMR engines are strictly superior (in terms of thrust and SIP, at least) to ion engines.
Of course, even at maximum thrust, current VASIMR drive designs produce *maybe* enough thrust to lift about .5 kilos (call it 1 lb) into space from the surface. Since the engine itself masses far more than that, you'll still need something with really high thrust to get it into space in the first place. Based on that, chemical engines will probably be around for a while, unless we can whip up a space elevator while we're at it. Theoretically you could run more power through a VASIMR and get more thrust, but I suspect the practical limit on doing so is far less than would be required for liftoff (if you could even get it to operate in an atmosphere). Even without that, though, it would be an incredible boon to intrasystem travel, or for station-keeping engines on satellites.
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The real breakthrough will be takeoff to spaceflight in one stage with a sustained 1G of acceleration (I seem to remember that 1G X 355 days = 92% C) if we do that our future may be brighter than it looks now.
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Nowhere near that, sadly. Chemical rockets measure burn times in minutes or seconds. Thermal nuclear engines last longer, but still not long enough (fuel-wise), and we aren't currently developing them. Ion engines can last that long if they have a long-lived power source and enough fuel (yes, they still need some reaction mass) but their thrust is crap; you're unlikely to see 1/1000 of 1G out of one. VASIMR is more powerful and more efficient, but it too needs some fuel... and it reqires a much more powerfu
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~5000 mN sounds nice, but it doesn't sound so significant when we use proper SI - 5 Newtons thrust, rather than 5000 milli-Newtons.
In order to get to the moon in a day at 5N, we'd need a vehicle that massed about 25 kg. Or, perhaps, a 200 MW power plant that massed considerably less than 5 tons - good luck with that.
Realisitcally, VASIMR won't substit
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5000 mN, 5N, is enough force to lift a 1lb melon 1 meter every dozen seconds, increasing by a meter every dozen seconds, away from our 1G Earth (F=ma). 200KW (268HP) is about triple the redline output of a big car engine. We clearly have a lot of efficiency improvements to look forward to in our climbs into space.
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Try looking at the specific impulse on those. ~800-1000 seconds. Now compare to 3,000-30,000 seconds. Which one is more efficient with its fuel?
NTRs are very, very cool. But they're very wasteful with the energy produced by the reactor. Potentially great for liftoff (if anyone ever building a modern variant without the graphite flaking problems), but nowhere near as useful for interplanetary travel as the VASMIR engines are promising.
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if there's a malfunction during liftoff, having a fission reactor coming down isn't such a great thing
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if there's a malfunction during liftoff, having a fission reactor coming down isn't such a great thing
Don't worry about liftoff... an unused reactor core pretty much by definition has none of the highly dangerous waste byproducts in it... because... it's unused. A new reactor core is fundamentally mostly harmless, not really worth worrying about.
On the other hand, when landing, its still super hot, still streaming out delayed neutrons, full of extremely nasty waste isotopes, if the burnup ratio is high enough its physically weak and "crumbly", probably neutron-activated otherwise non-radioactive components
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the designs I have seen are of reactors used to launch from earth oceans, because the weight makes a chemical stage underneath it an absurd proposition.
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Gas Core Nuclear Thermal Rockets are still science fiction. No one has yet built the necessary components, and there is a great deal of argument over whether or not "nuclear light bulbs" are even possible.
I'd love to see a 3,000 - 5,000 second NTR engine as well, but it would still be better suited for liftoff. For interplanetary travel, you simply can't beat the efficiency numbers of VASMIR. They start at the theoretical limits of NTRs!
I don't have the reference in front of me
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Actually, given the incredible thrust of a NTR, I can see them being used for short (objects in Earth orbit) trips, rather than designing your spacecraft for switchover to a more efficient engine. That said, the fact that a VASIMR can maintain thrust all the way would make them faster than NTRs for any sufficiently long trip - maybe even for just getting to the moon and back; anybody want to do the math on that?
One advantage that a NTR could offer is maintaining "gravity" from the trust. If you can somehow
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You'd still have to haul around a LOT of fuel; they can't sustain thrust for anywhere near the time that a VASIMR could. This is not to say they aren't fantastic, and they CAN produce enough thrust for takeoff from earth (something no rocket using an ionized reaction mass - like a VASIMR - is ever likely to accomplish). Once you're in space, though, a VASIMR is more efficient, lasts longer, and (in the long run) allows much faster travel.
Any idea what the thrust level is? (Score:2)
Is it a newton? More?
Apparently the power level was only sustained for a second or so...it's going to have to run for a month or so to be useful, but this is probably a good start.
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The expected thrust is 5 newtons for 200 kW of power. However, they have only tested 30 kW of power.
170 kW? (Score:2)
TFA is light on details, it reads like a press release.
Superconducting Plasma Rocket Engine? (Score:4, Funny)
Superconducting Plasma Rocket Engine?
Sounds like it oughta be able to make at least Warp 3.
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"Full impulse power."
"No sir! You have Genesis! You can have whatever..."
"Full impulse power! Damn you!"
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high Impulse speeds (0.90g+) subject the starship to relativistic speeds. Federation protocols recommend avoiding high impulse travel except in distress or emergency situations. the computers' chronometer should be resynchronised to federation subspace timing beacons when possible.
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Actually, to the best that I ever understood it (almost nothing; it wasn't ever explained very much) it's the closest to an "impulse engine" from Star Trek the we've ever seriously considered. For anythign like a "true" impulse drive, you'd probably need to get the fuel mass up a LOT higher - kinetic energy may go up as the square of velocity, but momentum is only lineraly proprtional, and the mass ejected is really, REALLY minimal - but the theoretical speed capabilities aren't too far off.
Checklist (Score:4, Funny)
Superconducting: check
Plasma: check
Rocket: check
Linux:
Three for four isn't bad.
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Shake-n-bake (Score:2)
Now that's a proper name: shake-n-bake.
Dude 1: What's this?
Dude 2: VX-200.
Dude 1: Ok, what actually is it?
Dude 2: Superconducting plasma rocket engine.
Dude 1: Yeah, fuck you, too.
Let's not get out of hand about Mars (Score:5, Interesting)
Now don't quote me on this b/c it's been a while since I took orbital mechanics... but I seem to remember the "optimal" window for an Earth-to-Mars transfer opening up once every 2.5 years, it would take 8 months to travel there, 90-98% of your ship's mass would have to be fuel, and then you'd have to wait 1.5 more years for the "optimal" Mars-to-Earth orbital transfer window. In other words, doing a round-trip flight to Mars is no trivial matter.
Even with a more efficient fuel, perhaps you can stretch those windows, but you're not going to find an astronaut who is willing to leave now for a 1.5-year-commute to Mars, instead of waiting a year and doing an 8-month-commute. Even if those times are shrunk by a factor of 2 with a more efficient fuel, it's always going to be a huge operation.
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You're partially correct. But only partially. While you generally need to wait for proper alignment to make your journey, the length of the journey is still dependent on how fast you go. Chemical rockets are so slow that we need to begin the orbital transfer ~260 days before the expected orbital intersection with Mars. With more acceleration, the ship could leave later and still make the rendezvous.
Ok, that's horribly simplified. But I simply don't have the time to look up and explain the myriad of orbital [wikipedia.org]
Re:Let's not get out of hand about Mars (Score:5, Informative)
You're mixing about a zillion different orbits into one recollection.
If you've got enough fuel, just turn and burn man... simple. Of course that takes a heck of a lot of fuel, like your idea of 98% mass fraction of fuel.
A Hohmann TO is the simplest imaginable transfer to design and is pretty quick too. Draw an ellipse that touches both orbits...
http://en.wikipedia.org/wiki/Hohmann_transfer_orbit [wikipedia.org]
A Bi-elliptic is way slow, but if you're making a major/huge change to your orbital parameters it takes less fuel. Enter a giant orbit way the heck out there, then on the return pass enter your new orbit. Handy for inclination changes too.
http://en.wikipedia.org/wiki/Bi-elliptic_transfer [wikipedia.org]
And if you literally have decades of spare time there is the famous "ITN" which takes practically no fuel and takes practically forever, which works by wandering around the various eddies of the Lagrange points or something very vaguely like that.
http://en.wikipedia.org/wiki/Interplanetary_Transport_Network [wikipedia.org]
As for your claim of 98% mass fraction, check out the math on
http://www.iki.rssi.ru/mirrors/stern/stargaze/Smars2.htm [iki.rssi.ru]
"showing we need add just 2.966 km/s, a shade short of 3 km/s or 10% of the orbital velocity."
and then when you get there you need another 2.5 km/s to match mars orbit, although you can play various gravitational slingshot games to help that out...
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It's been a couple decades for me, too, though my masters class in space vehicle guidance and nav had the final as a mars shot (NASA Admin Griffin was the professor; yes he has always been hyped on mars!)
Anyway, while the sibling posts are correct, there are orders of magnitude between this technology and the reality of meaningfully shifting the duration of a Mars shot. There are certain "safe" transfer orbits which get the crew back to earth automatically (you can intercept mars, and if you miss injectio
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Thanks for the excellent post! But there's one minor detail I'd like to inject here:
If you're going to pay the weight cost for a nuclear reactor (which is the only technology that can feasibly produce that much energy for sustained periods), you might as well attach more engines to it. This will give you far more thrust for the journey as well as spread the weight cost of the reactor across many engines. And since much of the cost of the reactor is fixed (e.g. You've got to shield the thing from the crew) i
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I'm trying really hard to come up with an appropriate response to that. Unfortunately, you have left me speechless and dumbfounded. Maybe some day I'll even understand what the point was you were trying to make.
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No kidding. But this engine is able to take large amounts of energy and impart it into very little matter. 200 kW per engine for 5 newtons of thrust to be specific. At an Isp ranging from 3,000 to 30,000 seconds, it needs very little reaction mass to operate. But to sustain that much power, it needs a nuclear generator. And if you're going to pay for the weight to generate 200 kW, you might as well pay to generate a megawatt or more. You'll need to carry more nuclear fuel and reaction mass, but the high eff
Summary Wrong (Score:3, Informative)
Referring Back (Score:2, Offtopic)
Referring back to http://ask.slashdot.org/article.pl?sid=09/06/27/0152216 [slashdot.org] , where someone asked about a freer country to move to, I suggested Costa Rica.
Besides the humanitarian lean of their universities, they're quite up on technology. They don't have a lot, but they like it. TFA is an example -- Ad Astra is based there in part. It's founder is a native of C.R. and ex-NASA astronaut, Dr. Franklin Chang-Diaz.
There's also been a few folks go down there to check it out for a possible launch site for commerci
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Isn't Costa Rica a US territory? or it that Puerto Rico I'm thinking of?
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Given your handle, I've got my sarcasm filter set to "high", but for the unenlightened, technically, it's Puerto Rico.
There are entities that consider all of Central (if not South, as well) America as "US Territory".
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I actually looked it up after I posted. I'm not sure why I didn't just do it without posting.
Thanks anyways.
Yiddish (Score:4, Interesting)
In Yiddish (the Jewish-German creole of Eastern Europe), VASIMR means "woe is me".
I know, probably o/t.
Also obligatory post (Score:2)
His life story is amazing and should be inspirational for many people in which education and hard work can enable you to succeed in life.
power sources - hither and yon (Score:5, Insightful)
It doesn't matter too much how efficient a power source is, as long as the fuel is plentiful. For instance, if you have a REAL LOT of petrochemicals it doesn't really matter how much you have to use to get to mars, etc. BUT more important is how DENSE the energy source is...i.e, how much more of the fuel does it take to move the fuel that is going to be used later on. This gets to be a BIG PROBLEM with chemical fuels, as even at their best they are not very DENSE. Of course, efficiency helps. But say, for a moment, that you have a nice large nuclear power plant on earth...you could probably use all that heat to either directly or indirectly (though electricity) create some high-density chemical fuels...but there's a limit to how much power a chemical fuel can provide. We need NUCLEAR FUEL, be it fission or fusion, or even better ANTIMATTER fuel. While some people claim that nuclear fuel is too dangerous to use on earth, I disagree. But I do think that antimatter is too dangerous to be used anywhere in the vicinity of important and/or massive objects (can't have the earth or space station pummeled by shrapnel in the case of an antimatter explosion, can we? And remember, there's no air friction to slow this shrapnel down). So, the best advice is to use fission, or hopefully fusion once technology gives up on the silly Tokamak idea, to leave earth's gravity well and move far enough out of the plane to be safe, and then use antimatter to the long haul. What, you say antimatter is too expensive? That's only because you've picked the wrong places to manufacture it. Production using solar power in CLOSE SOLAR ORBIT, in a thousand factories, should make antimatter cheap enough. You just have to go fetch it from close-solar orbits, which can be robotically done using the antimatter as fuel itself! The factories themselves can be replicaed using easily available materials from the moon or asteroids, and then replicated in close solar orbit using the vast energy resouces of the sun.
So to sum up, the problem isn't the amount of energy required, but the location of that energy. Move our energy conversion devices closer to the source, and we'll have plnety of consumable energy, even if it has to go through several intermediate storage mechanisms to become safe and easily accessible.
And yes, I've said this in other places, over time. I just hope that I get through to someone who is charged with long-term planning for space exploration.
Re:Total power (Score:5, Informative)
For comparison, your car needs about 20 kW of power to maintain cruising speed on the interstate. 200 kW of power would be akin to running a 300 horsepower engine at its peak power output. With the way cars are designed, that doesn't happen much with the possible exception of expensive sports cars and pickups hauling a heavy load.
If we take the case of the sports car, we find that it's enough energy to slam you against your seat and hold you there while you do 0-60 in 3 seconds. (Hey look, ma! Artificial gravity!) In the case of a pickup pulling a heavy load, it's enough to accelerate reasonably while dragging a trailer full of spools of heavy steel cabling.
The difference between your car and the spaceship is that the spaceship will be powered by some sort of long-term fuel supply. e.g. A nuclear reactor. Which means that the spaceship will be able to continue accelerating for millions of miles while your car would have run out of gas after the first few hundred miles.
Since acceleration is cumulative, being able to continuously accelerate like that means that distances between planets become a lot smaller on one "tank of gas" as it were. Add more engines for greater thrust and redundancy, and you have a souped-up hot-rod of a ship that can take you interplanetary distances in record time.
Hmm... I'm sure someone is about to chide me for some horribly sloppy analogies, but look on the bright side. It's got cars in it! And hopefully it will make the energy budget a bit more understandable. ;-)
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Re:Total power (Score:5, Insightful)
Correct. While it's theoretically possible to use engines like this as part of a liftoff stack (assuming enough engines, low enough weight per engine, and a high enough power budget), it's not really practical to consider such a concept at this time. For the short term at least, LEO access will remain the purview of chemical rockets.
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For the short term at least, LEO access will remain the purview of chemical rockets.
And that (besides the cosmic rays, loss of bone mass, lack of ability to pull over into a petrol station when you get hungry or something breaks, the Bad Thing that would happen when a rock smashes through your craft, and i-m-m-e-n-s-e distances) is why we are effectively stuck on this nice, green, wet, magnetically-shielded rock for the foreseeable future...
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Liftoff with a VASIMR would require pushing it WELL above the current power limits of any design on the table. The problem is that making the exhaust go faster makes the ship more efficient (less reaction mass needed for a given thrust), but since energy is proportional to the square of velocity (while momentum is only linearly proprtional), and since the mass exhausted is truly miniscule, it would take really incredible amounts of energy to produce enough thrust for liftoff. Pumping out more reaction mass
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20KW? Wow. That's just made me think. 20KW to pull a car along at (I'm guessing) 65MPH. Meanwhile, 250W or so from my two legs will propel me at a steady 25MPH on my pushbike.
Aren't bikes clever?
Only if you're looking for exercise. (Score:3, Informative)
Biking for an hour at 25MPH costs 1181 kcal, according to this calendar [geocities.com] (others suggest it costs even more calories), which translates to 1373 watt-hours. (Your body isn't that efficient at converting fuel to energy.) So let's assume your 250W figure is correct, and your body is about 18% efficient in converting calories to power.
Biking for an hour at 65MPH (if you could) would burn 18669 calories -- remember, wind resistance goes up as the cube of speed. That works out to -- let's see -- 21712 watt-hour
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Yeah. I mean, 65MPH on the flat would be no trouble, but I'm afraid passengers and luggage is right out of the question...
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I'm sure someone is about to chide me for some horribly sloppy analogies
At least you dodn't talk about light bulbs or libraries of congress.
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When you have constant thrust, this is an easy to solve problem. You speed up until you reach the halfway point. Then you turn the ship around and begin thrusting the opposite direction for the second half of the journey. Assuming sufficient constant thrust, you'll still get to your destination faster than the yahoos attempting a low-energy transfer.
As a bonus, thrusting forward and t
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Well, slowing down is pretty much the same issue as speeding up. When you get about halfway there, you turn around and fire the engines in the opposite direction.
The debris issue? Well, first, you have this thing called radar, which can detect fairly big chunks from a distance. You could use chemical engines to maneuver so you avoid hitting these rocks. Remember that, assuming you're on a collision course, it wouldn't take a whole lot of propellant to change your course a fraction of a degree so that it
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Of course, to borrow a phrase, "Space is big." The chances of hitting/being hit by a micro-meteor in such a way that the rocket is destroyed are probably less likely than an airplane crashing.
[Citation needed]
Any place one would want to go will include great quantities of small particles. These things are the dust left over from planet building.
If you can not detect them on radar, speculation of their density in what we presume to be empty space seems premature.
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You do realize that when talking about traveling to the moon or Mars, we've already been there, right?
We know the density of microparticles isn't high because we've already passed through and our craft weren't sandblasted into oblivion.
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And how fast were we going?
The craft were hit multiple times by slow moving particles. Just try that at the speeds being discussed.
Think before you post.
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How, exactly, would the speed of travel increase the number of particles hit?
Sure, faster travel increases the rate at which you hit particles, but you will hit the same number of particles. Doesn't matter if you're going 0.99c or 0.000000000001c.
(assuming a relatively constant microparticle density. But that's a pretty safe assumption, since a significant increase in density should be detectable as a "
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The faster you go, the more distance you travel in a given period of time. (And "time" is the only measure that counts, since this engine technology's sole purpose is to make the time of travel useful to humans).
The more distance you travel the more particles you encounter [again assuming constant density, which I do not accept as fact].
But the speed of impact is high enough that the vehicle may not survive even ONE such impact.
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You're traveling the same distance. Mars doesn't suddenly get further away because you're going faster.
And this has no bearing on the density of these particles, which was my entire point.
Our "slow" probes have provided data on the density of the particles. A "fast" probe will encounter the same particle density.
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Our slow probes have been hit repeatedly.
Our fast probes would not have survived any of these hits.
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Also, when building up to this insanely fast speed, what are they planning to do if some random debris gets in their path?
The spaceships will naturally come with pre-installed cowcatchers [wikipedia.org].
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This topic is important for me, as this planet isn't big enough for me and You.
So, how to deal with space junk of one type or another? The first problem is detection. The faster your trael, the more difficult it is to detect and react quickly enough. This limits us to less than half-light speed, because the best we can do is to use radio or light to broadcast and have time to reflect back to us (taking into account various doppler shifts), some processing time, and then enough time to perform a countermeasu
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For 200 kW per engine, we're thinking nukes.
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Yeah, and it took FEMA five days to get water to the Superdome and turned away truckloads of supplies. But that's what kind of government you get when you elect people who think government is always the problem into government.
The problem isn't "government", it's bureaucracy, and the larger any organization is, the more bureaucratic it becomes. Anyone who dealt with AT&T before the government broke up their monopoly knows this. The phone company was far more bureaucratic then the DMV.
Springfield, IL's p
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Does this experiment mean we'll be seeing some sort of plasma weapon any time soon?
On most things we want to kill, bullets work just fine. Also, any kind of plasma weapon is probably totally useless if not in a vacuum, and marginally useful in a vacuum (can probably be deflected or dispersed with a big frickin' magnet).