NASA's NEXT Ion Thruster Runs Five and a Half Years Nonstop To Set New Record 184
cylonlover writes "Last December, NASA's Evolutionary Xenon Thruster (NEXT) passed 43,000 hours of operation. But the advanced ion propulsion engine wasn't finished. On Monday, NASA announced that it has now operated for 48,000 hours, or five and a half years, setting a record for the longest test duration of any type of space propulsion system that will be hard to beat."
Perfect analogy for NASA (Score:5, Funny)
Running your engines at full power but standing in one spot for 5 years. That pretty much sums up our space program since Apollo.
Re:Perfect analogy for NASA (Score:5, Insightful)
So then those rovers on Mars are figments of my imagination?
Our space program since Apollo has gotten better. Unless you think their is some scientific value in sending humans to play golf on other worlds.
Re:Perfect analogy for NASA (Score:5, Insightful)
Our space program since Apollo has gotten better. Unless you think their is some scientific value in sending humans to play golf on other worlds.
Laugh and minimize all you want, but the one geologist to land on the Moon [wikipedia.org] managed to learn more (and faster) in his one short trip than all of the Mars rovers combined. Why, you ask? Because he didn't have to waste time looking at a picture and speculating on what a shadow or shape looked like it could be. Instead, he just walked up to an item of interest, looked at it, and was able to discern in seconds something that, well, takes teams of scientists weeks on end to speculate over nowadays.
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I am not laughing nor minimizing. Scientists are not stuck with pictures, but tools not even available during the Apollo era are on those rovers to sample rocks.
I agree, but we simply will not bother until we are forced. We can't even get people to update coal power plants, you can forget them wanting to spend a dime on this.
Re:Perfect analogy for NASA (Score:5, Interesting)
Not really. The tools are impressive, but mostly in how they try to overcome the crippling need to run remotely from umpteen million miles away.
Let's have a look: http://en.wikipedia.org/wiki/Curiosity_(rover)#Instruments [wikipedia.org]
Lists 14 instruments. But 5 of them are just cameras, strategically placed because they can't be moved. My friend the amateur photographer could do much better with her DSLR. The "environmental monitoring station" measures humidity, pressure, temperatures, wind speeds, and ultraviolet radiation; not exactly groundbreaking stuff here. Same with radiation assessment. There's a robotic arm capable of drilling holes a whopping 2" deep and a dust removal tool, commonly known as a 'broom'. The "Dynamic Albedo of Neutrons" sounds sexy as hell, but then you realize a person with a trowel could do the same job.
The other instruments are all spectrometers and a chromatograph. The means by which they work are novel, due to the aforementioned remote requirements, but the end result is not really different from what could be done in any decent lab 50 years ago. Honestly, a decent scientist with a shovel and a few thousand dollars in high school lab gear could do better than all the rovers ever sent. God help us if we ever needed a probe to do something _really_ difficult.
So by all means, send what probes are needed to figure out how to get people there, but anything beyond that will just provide minimal information at enormous cost.
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My friend the amateur photographer could do much better with her DSLR.
Can your friend do better while fitting in a small box without life support? If we took the budget, both in terms of costs, volume, and amount of equipment needed to send a person there, that could buy a lot of cameras, and ones that could move around just as much as your friend could move them around.
The "Dynamic Albedo of Neutrons" sounds sexy as hell, but then you realize a person with a trowel could do the same job.
Not quite the same as a person with a trowel, considering neutron sources get used for analysis by geologists on Earth even where there are plenty of trowels. Even if you had a person on Mars, with a trowel
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...The means by which they work are novel, due to the aforementioned remote requirements, but the end result is not really different from what could be done in any decent lab 50 years ago. Honestly, a decent scientist with a shovel and a few thousand dollars in high school lab gear could do better than all the rovers ever sent. God help us if we ever needed a probe to do something _really_ difficult.
So by all means, send what probes are needed to figure out how to get people there, but anything beyond that will just provide minimal information at enormous cost.
But the cost of sending a person there dwarfs the mission cost and there would be a much greater chance of total mission failure because of the complexity of the life support systems.
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Its more the long turn around time between observations, new instruments and different observations.
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Actually the geologist learned more than the Mars rovers combined since the rovers didn't land on the moon. Its hard to learn more about the moon than a live person when you are millions of miles away.
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The guy who went to the moon and didn't find any evidence of water? And now is dedicating himself to disproving the idea of global warming? I'd rather have robots.
Not totally fair to say he couldn't find water, but Opportunity found it, while the geologist couldn't.
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If the geologist was far better than a robot, how come the geologist didn't learn the most basic geological facts?
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If the geologist was far better than a robot, how come the geologist didn't learn the most basic geological facts?
He did. He learned there was no evidence for flowing water on that part of the moon...because there was never flowing water on the moon. Seriously? Are you trolling or do really not understand this?
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Re:Perfect analogy for NASA (Score:4, Interesting)
He wasn't talking about Mars, but the moon. His argument stands.
No, he was walking about Mars. Quote: Not totally fair to say he couldn't find water, but Opportunity found it, while the geologist couldn't. Opportunity is a Mars rover. The geologist in question is Harrison Schmitt who went to the moon. He wasn't even looking for water...not that they put him in a place likely to have it. He was simply there to use his expert geologist eyes to find something geologically interesting, otherwise they would have just had one of their pilot astronauts grab some rocks. These aren't even comparable things. But I'm sure if you placed a geologist in the same spot Opportunity was, he could have found evidence for water in 30 minutes or less and spotted several other interesting things as well. Robots aren't adaptable to other kinds of missions. They do what they're designed for. A human can accomplish a multitude of things, adapt, and apply new knowledge on the spot. Yeah, robots cost a fraction of what it would take to put a human up there, a human can also accomplish far far more. But to argue that humans can't do more than a robot like the GP implied, is totally absurd.
Re:Perfect analogy for NASA (Score:5, Interesting)
Don't take offense, because I'm sure you're thinking this because you've been told so many times that this would be the case, but why is there the common belief that mankind would find a complete vacuum, devoid of ANY resources other than photons, be more suitable for our life than the Earth would be in any state of pollutive decay?
If we can build capsules for space, why not do the same thing here and protect ourselves from the elements? We can use space suits to travel around the exterior here, too, extracting useful resources from the fetid scum we created, and if we can shield ourselves from cosmic radiation, why wouldn't we be able to shield ourselves from any possible post-nuclear-holocaust radiation?
I'm certainly not suggesting that NASA is a waste of money - I am an aerospace engineer, after all - I'm just saying that if your house became infested with termites, you wouldn't resign yourself to abandoning it and living on a houseboat in the middle of the ocean because there are no termites in the middle of the ocean.
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devoid of ANY resources other than photons, be more suitable for our life than the Earth would be in any state of pollutive decay?
Those photons are quite a resource in their own right. But there is also every element you can find on earth floating around in ridiculous abundance, and easier to access too.
As to why, well there aren't many reasons to choose a station over earth, but there are plenty of reasons to choose a station over anywhere else. We would have perfect control over the gravity in a station for a start, which neatly sidesteps a whole host of problems with either bone decalcification or excessive gravity, not to mention
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But there is also every element you can find on earth floating around in ridiculous abundance, and easier to access too
I appreciate a good sci fi yarn as much as the next guy, but do try to keep in mind the "fiction" aspect of it. In fact, the overwhelmingly defining characteristic of space would be the tremendous amount of emptiness that it is comprised of. The vast distances just within our own solar system immediately decry the abundance and easy access to useful resources. That will hold true at least until you solve the problem of cheap and efficient energy. I would argue that when you have solved that problem, yo
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And if it were cheaper and easier to construct a metal alloy machine using sophisticated internal combustion mechanics after extracting the fuel from suboceanic deposits and refining the stuff before transporting it around the globe in huge container ships, more of these vehicles, and finally pumping it back into the ground from whence it gets pumped up again, we'd do that rather than riding horses everywhere.
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Interesting argument. What does it cost to feed and maintain a horse? What is the maximum speed and range of a horse? Can a horse power air travel? The energy cost efficiency of internal combustion is pretty hard to beat with today's technology.
That undersea oil was there 100 years ago, but there was more readily available oil that was easier and cheaper to get to so we didn't have a motivation to go after the harder stuff. Technology also improved to enable us to go after the harder to retrieve resour
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Interesting argument. What does it cost to feed and maintain a horse? What is the maximum speed and range of a horse? Can a horse power air travel? The energy cost efficiency of internal combustion is pretty hard to beat with today's technology.
The advantage of asteroid resource exploitation and indeed deep space manufacturing is that it can be scaled up arbitrarily, not terribly dissimilar to the speeds and economies achievable with internal combustion engines. There are no effective limits to how big we can make things and how much we can do up there, an advantage that terrestrial manufacturing does not share, if for no other reason than we'd have to turn the planet into a slag heap to approach a similar result.
That undersea oil was there 100 years ago, but there was more readily available oil that was easier and cheaper to get to so we didn't have a motivation to go after the harder stuff. Technology also improved to enable us to go after the harder to retrieve resources.
We've been approaching peak oil for twenty years now. What is the forecast for hitting peak iron or peak nickel?
Did we hit peak speed or peak fodd
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The point of course is that without massive investment in infrastructure, pipelines, manufacturing capability, and technological advancement which continues to this day, cars would make much less sense than horses, particularly economically. Cars and oil didn't become cheaper by accident/act of god, they are the product of decades, even centuries, of effort.
Obviously it isn't difficult to extrapolate this as regards asteroid mining.
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It takes huge amount of energy and labour to get something into orbit
This is in fact the only major stumbling block in the way of economical and profitable space exploration and development. The solution to this problem can be found here: http://maglaunch.com/ [maglaunch.com]
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The dinosaurs are extinct simply because they didn't have a space program.
Not to mention, there's an awful lot more resources available in space than just vacuum and photons.
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The dinosaurs are extinct because they didn't adapt to a changing environment.
And one way to adapt to a changing environment is to not be there when it's changing.
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If we can build capsules for space, why not do the same thing here ...
You make good points for cases where the Earth in general becomes less/un-inhabitable - for whatever reason - but not for large asteroid strikes, gamma-ray bursts and eventual Sun death. Yes, those are very rare or far off in the future, but the long-term survival of those types of events requires us living somewhere else.
Hopefully, we'll evolve into a less stupid, petty, short-sighted, self-destructive species by the time we need to deal with those kind of things.
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but why is there the common belief that mankind would find a complete vacuum, devoid of ANY resources other than photons, be more suitable for our life than the Earth would be in any state of pollutive decay?
Well, one can look at what's actually out there. When you do, you will find that it's not a complete vacuum devoid of any resources other than photons.
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, space may be the only habitable home we have left after this one gets wrecked
The least hospitable places on earth are still far more hospitable than pretty much the safest places within traveling distance.
It's a lot easier to clean up earth than to terraform or colonize a planet. Even if we nuked the living snot out of this planet it would still be lower radiation than the trip to Mars or the Moon. It's easier to filter out viruses than it is to create oxygen. It's easier to dive deep under the ocean to escape a catastrophic tsunami or asteroid impact than to fly to another pl
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Laugh and minimize all you want, but the one geologist to land on the Moon [wikipedia.org] managed to learn more (and faster) in his one short trip than all of the Mars rovers combined.
Well, I think you may be comparing apples and oranges (Moon vs. Mars), but your point is valid. We learned more and we learned it faster with the Apollo missions than the Soviet Union did with their plethora of lunar probes, rovers, and sample retrieval missions.
The question becomes, is it worth the money to learn more faster?
Imagine you're getting ready to enter college. You can pay, say, $400,000 and spend four years of your life attending college to gain knowledge. Or, with my handy-dandy memory devic
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If we humans go to Mars, it'll be very, very hard not to seed the environment with life. Of course said life might take very long to flourish, but contamination of Martian surface is a real problem for human visitors.
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Knowledge has no value to you?
That must be one hell of a miserable existence you live.
Re:Perfect analogy for NASA (Score:5, Informative)
Would it be insufferably pedantic to mention Pioneer 10/11, Explorer 49, Mariner 10, Helios A/B(with Germany), Viking 1 and 2, Voyager 1 and 2, Pioneer Venus 1 and 2, ISEE-3(with EU), Magellan, Galileo, Hubble(with EU), Ulysses(with EU), Mars Observer, Clementine, WIND, NEAR Shoemaker, Mars Global Surveyor, Mars Pathfinder, ACE, Cassini-Huygens(with EU), Lunar Prospector, DS1, Stardust, Mars Odyssey, Genesis, Mars Exploration Rovers, MESSENGER, Deep Impact, Mars Reconnaissance Orbiter, New Horizons(in transit), STEREO, Pheonix, Dawn, Lunar Reconnaisance Orbiter, Solar Dynamics Observatory, Juno, GRAIL, Mars Science Laboratory, and Radiation Belt Storm Probes?
Sure, our man-in-a-can cred isn't what it used to be; but I, for one, welcome our robotic overlords.
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The problem is that the thruster only produces 236 mN of thrust. NASA's bureaucracy coupled with the infinitely massive boat anchor called the US government has created an object so huge that 236 mN over 5.5 years has only moved it an imperceptible distance.
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It also sums up the fact that space is an enormous deadly vacuum with no real reason to send people there.
Hate to say it, but we already live in space - this big ball of mud and air that we call home happens to float in it. It'd be nice to get out in the neighborhood a little, no?
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If you've got the money, honey - I've got the time.
Specific impulse (Score:5, Funny)
I wonder if they had felt a specific impulse to switch it off?
Re:Specific impulse (Score:5, Funny)
Nah. The lead scientist felt it was ok to let it run as long as they kept a close ion it.
Could we achieve 1G of thust. (Score:5, Interesting)
My Hope if we could build a space craft that can accelerate 9.8m/s^2 (1g) for the duration of going to Mars and Back. You go to at 1g half way to mars, then you decelerate at 1g the other half. Orbit for a period of time. Drop down a landing party for a while. And go back at 1g half way decelerate at 1g the other half. Then you would have a good long range mission with out the 0g effect messing up the body.
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Not to mention that at 1g it wouldn't take long to get to speed of light :-)
Re:Could we achieve 1G of thust. (Score:4, Informative)
Without relativistic effects about a year but, as noted by the sibling poster, relativity gets in the way from the outside observers point of view. And what good is next day delivery if the goods are 1 day old and the recipient's great, great, great, great, great granddaughter has to sign for the package?
Though practically impossible with current or proposed technology, it would, indeed, take only 35 days to reach 0.1c, and we'd be 225 million km from our starting point, ignoring gravitational effects of other bodies. Though in astronomical terms that's not very far (less than the diameter of Earth's orbit) - less than half way to Jupiter on the closest possible approach.
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Without relativistic effects about a year but, as noted by the sibling poster, relativity gets in the way from the outside observers point of view. And what good is next day delivery if the goods are 1 day old and the recipient's great, great, great, great, great granddaughter has to sign for the package?
As a method of delivery its worthless, but as a method of colonization its pretty neat. If by some stretch of the imagination we could identify a planet as definitely habitable from here we send off a crew at some significant fraction of the speed of light. I'm sure the people actually travelling there care a lot more about the passage of time than those of us back on Earth (they'd have to be specially selected with the idea that everyone back on Earth that they knew would be dead by the time they arrived
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Wrong. Classical (i.e. useful) communication via quantum entanglement cannot exceed the classical speed limit. See the no-cloning [wikipedia.org] and the no-broadcast [wikipedia.org] theorem (or
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they'd have to be specially selected with the idea that everyone back on Earth that they knew would be dead by the time they arrived
Heck, I'd go with understanding that just certain people would be dead back on Earth... :-)
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they'd have to be specially selected
As an aside, "special selection" probably doesn't have to be all that special. The prime criteria in your example probably would be that the person is willing to go and isn't too unhealthy.
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So it takes about a year to get up to (oh, lets say 0.75c) and the same to decelerate. That puts a robotic mission to the closest stars on the table.
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And what good is next day delivery if the goods are 1 day old and the recipient's great, great, great, great, great granddaughter has to sign for the package?
If you're the one signing for the package, it's not exciting. If you're the goods, it is. As MBGMorden noted, this would be remarkable transportation for colonization efforts.
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This made me laugh out loud. A toast to you my good AC.
1G of thust - you're gonna need a bigger boat (Score:5, Informative)
1G of thrust would require, as you mentioned, almost 10m/s2 of acceleration, or your mass x 10 in Newtons.
NEXT produces 236 mN of thrust at 7kW of power
A typical terrestrial nuclear power plant will produce about 1 GW of power, or enough to power 143,000 of these engines. That would result in 33,700 Newtons of thrust, able to accelerate a spacecraft at 1G weighing 3433kg.
To put that into perspective, those (143,000) engines would burn 2860kg/hr in fuel alone.
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to put in perspective for some here, that's not quite 0.05 pounds of thrust. Not quite quite in the range of pushing a viable starship (let's estimate with mass of say a "boomer" submarine) to anywhere in the solar system, let alone the stars
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That reduces the efficiency, requiring more nuclear reactors to power it (but less fuel).
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In practice, having your exhaust velocity near your final delta-v tends to be a pretty good combination of speed and propellant to vehicle mass ratio.
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Even a level of trust that can help a satellite/ship leave an asteroid would be useful.
After that, a level of trust that can make a ship escape the gravity of the moon would be very useful.
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Then you would have a good long range mission with out the 0g effect messing up the body.
Or you can just spin the spacecraft and save all that fuel.
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Still you need to fight momentum. If you have a ship big enough to hold heavy people with heavier supplies that is a lot of momentum to fight all the time. Sure we can burst speed of multiple G's but once the fuel runs out and the ship goes at a constant speed we are down to 0g.
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It won't be like driving a car. You accelerate 1/2 of the way there, turn around, and decelerate the rest of the way. That way you're at 1 G the whole time.
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If you have a ship big enough to hold heavy people with heavier supplies that is a lot of momentum to fight all the time.
Only send skinny people - duh.
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You mean accelerating at 9.8m/s^2
The same as the pull of gravity of earth.
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Hello Troll.
I mean what I said. Acceleration is a different measurement than speed.
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There is no resistance but the mass of the ship and the cargo will increase with the speed. Thus, if you had to spend, say, Z amount of joules to achieve 1g acceleration at low (compared to c) speeds, you woudl need many more joules to sustain the 1g acceleration the closer you are to c.
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There is no resistance but the mass of the ship and the cargo will increase with the speed.
Or does the mass of the Universe decrease?
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Fools! (Score:5, Funny)
Running that engine for 5 years attached to the planet already caused a diversion of 0.01 on the orbit we have around the sun! That's why the sudden global warming! Tin foil ionic hat
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I'm sure they every now and then turn the engine around to compensate for this effect.
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This is one of the most insightful short AC comments, like, ever. Good job, AC! :)
Re:Fools! (Score:5, Informative)
Bzzt you are both wrong. The net acceleration due to this test is zero, because the ions ejected out of the engine are halted by the test chamber. Net result is zero force.
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By the way, also undermining the value of this test was the fact that a test chamber is a grounded metal tube. Running in free space is utterly difference, as hs been discovered the hard way
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Wait till next week.
How Fast? (Score:3)
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Well, NEXT produces 236 milliNewtons of thrust, according to this article: http://www.newscientist.com/article/dn12709-nextgeneration-ion-engine-sets-new-thrust-record.html#.UcxBsfmcf4o [newscientist.com]
NEXT + nuclear reactor ~ 5000kg* (wag)
Fuel 1000kg
Voyager = 722kg
If we take our mass as an average to simplify the math, and ignore relativity (which I'm betting we can),
6222kg avg mass at 0.236N is 4.22x10-5 m/s2 acceleration. And for 50,000hx3600s/h = 7600 m/s delta V
So in 6 years, we will have accelerated from 11,100 m/s to
Re:How Fast? (Score:4, Funny)
a =
V=V0+a*t
V=(40,000 km/h)/(3600 sec/hr) + (.000236 m/s^2)*(50000 hours *3600 sec/hr)
V=53,591 m/s => 192928 km/hr =>0.00018 c
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You need to use the rocket equation for that. At the end of the burn, you'll be lighter.
Assuming Voyager with a NEXT thruster (unrealistic since the NEXT would need a much heavier RTG!),
delta_v= v_exhaust * ln(m_initial / m_final)
At 720kg initial weight, assuming 80kg initial propellant weight (I couldn't find it anywhere!), at I_sp=4000 we have exhaust velocity v_ex = I_sp*g = 40,000m/s.
Thus delta_v = 40,000 m/s * ln(720/640) = 4.7 km/s (10,500 mph).
How fast would it be going? (Score:3)
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Actually they started looking at using full fission reactors (space capable submarine reactors) rather than RTGs for outer planet ion drive craft.
http://en.wikipedia.org/wiki/Project_Prometheus [wikipedia.org]
http://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Orbiter [wikipedia.org]
We all know what comes next. (Score:2)
All we need is two of those engines, a spherical cockpit, and two large solar panels attached to each side.
NASA should come clean (Score:2)
What is strange is that it is on the ground. (Score:2)
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We can do the energy input with free-electron laser to 500kW or so, and multiple lasers and targets can of course multiply that. That's not a problem. VASIMIR uses Argon rather than Xenon. Argon is more common and Xenon is quite rare. The difference in efficiency is appropriate for the difference in availability of reaction mass. Ideally Hydrogen would be best as that's the commonest material in space, and VASIMIR works on hydrogen but less efficiently.
VASIMIR is scheduled for test on the ISS in 2015.
Speaking of, how's that space sail working out? (Score:2)
Yeah, Thomas Gold was right.
Re:Too bad it's at NASA (Score:4, Informative)
Which all but guarantees that this engine will never do anything more.
Sort of like the ion thruster on the Dawn [nasa.gov] probe, which left Vesta about a year ago with an ETA on Ceres sometime in 2015?
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The ion thrusters on the Japanese Hayabusa asteroid sample-return mission kept on breaking down but after a lot of TLC the main spacecraft did get back to Earth and its sample capsule was recovered.
A European Space agency probe, the 370kg SMART 1 was powered by an ion motor and flew from Earth orbit to Lunar orbit under ion propulsion in 2004. It burned 80kg of fuel over about 13 months producing 68 mN of thrust.
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http://en.wikipedia.org/wiki/Dawn_(spacecraft) [wikipedia.org]
It was launched in 2007 with an ion thruster.
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NASA's been stymied by the neo-cons, BUT, that is about to change over the next 2 years. The neo-cons continue to pour money into the SLS, but it will not fly humans until 2022. OTOH, SpaceX will have their Falcon Heavy available at end of this year, or early next year. At that time, Musk is supposed to announce how much longer to develop the Dragon Rider (human rated launch ca
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wow. The fact that NASA has more interplanetary probes out there than all of the other nations combined, means nothing to you, eh?
NASA's been stymied by the neo-cons, BUT, that is about to change over the next 2 years. The neo-cons continue to pour money into the SLS, but it will not fly humans until 2022. OTOH, SpaceX will have their Falcon Heavy available at end of this year, or early next year. At that time, Musk is supposed to announce how much longer to develop the Dragon Rider (human rated launch capsule), and is saying that he will introduce information about MCT. MCT is what others of us know as BFR (big fucking rocket), but the new name is Mars Colonial Transport. if the inside info is to be believed, it will be ready by 2020, and will launch 150-200 tonnes, while the neo-con's SLS will take only 70 tonnes and will cost 3-5x the costs to launch.
So, I fully expect that NASA WILL get back on track, assuming that we can keep neo-con's dirty stinking paws off NASA for about 1 year or so.
Most of the space exploration done by the U.S. has been done on the watch of a Republican president, including all of the Apollo missions.
https://en.wikipedia.org/wiki/Timeline_of_Solar_System_exploration [wikipedia.org]
http://en.wikipedia.org/wiki/List_of_Presidents_of_the_United_States [wikipedia.org]
Also, Elon Musk is a registered independent, neither a Republican nor a Democrat:
http://en.wikipedia.org/wiki/Elon_Musk [wikipedia.org]
You should also be aware that the backdrop for the majority of the space program was military, and based in the cold ware
Re:Distance estimate (Score:4, Insightful)
Don't know where you got these numbers from, but:
- There is no way this ion engine can produce 0.3g acceleration on 2000kg probe; something is way off.
- in addition to propellant, ion engine requires power - a lot of power ; you need to add weight of nuclear reactor on top of that (which is probably only thing able to produce enough power for long term with small amount of consumable fuel); for 2000N you would need something like 50MW of constant power supply
But yes, if you can create imaginary engine giving you even 0.1g of constant acceleration for spaceship over period of few decades, entire galaxy is yours.
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Not for the people on spaceship - and you care about them, not Earth. You can colonize the galaxy, you just cannot exploit settlers afterwards.
http://einstein.stanford.edu/content/relativity/q917.html [stanford.edu]
0.9c 2.29
0.99c 7.08
[...]
0.999999c 707.1
0.9999999c 2236.0
Of course, at high speed you will get problems with acceleration... fortunately, your fuel will get heavier as well. It all depends on that imaginary, perfect 0.1g engine which can sustain it even a
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Something is seriously wrong with your maths here. Don't quit your day job.
Thruster = 0.000236 N
Mass = 2000
f=ma ; a=f/m=0.000236/2000=1.18e-7 (this is a VERY low acceleration)
s=ut+(1/2)at^2 (u=0 so we ignore that part)
assume t=24000 hrs=2e9 seconds (to turnaround point)
s=0.5 * 1.18e-7 * 2e9 * 2e9=2.360e9 metres
By turn-around you would have travelled 2.36 million kilometres.
1 light year is 9.461e15 metres, so the space craft would have travelled about 2.5 millionths of a light year.
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Oh no it might just be a question of scale. How about a vehicle roughly the size of Discovery in 2001. Fission reactors for power and iion drives for propulsion. Plan on a ten year cruise to Saturn.