The basic process by which the mission is designed starts by defining the scientific scope, i.e. primary, secondary, etc. mission objectives. Based on those, you see which instruments and support devices you need to achieve each mission, and optimize the design to get the most of your objectives done within cost and reducing complexity. The reduction of complexity is important, because a project with a less than double the cost and double the "stuff" is not necessarily better because it probably has a higher likelihood of failure.
Of course, whether or not this is the right approach is a good question. Personally the idea of a huge number of incredibly cheap drones with a 10% success rate sounds especially appealing to me... but thats just me. The high cost of launch reduces the utility of that kind of model.
I can assure you, as a student at Texas A&M (I know one of Lemmon's students pretty well), that we are in fact very wet and windblown thanks to Ike. But, we got off class on Friday, so I can't complain too much.
I think you hit the nail on the head. The implicit collusion between the cell companies so that prices are the same and so that switching is difficult makes it so that refusing to use them when they charge that much is impossible. For instance, I certainly see the utility, for instance, setting up a quick lunch date while in class or giving directions in a crowded, loud bar or restaurant. However, I refuse to pay extra for something that shouldn't be, so I just don't use them, and even turned them off on my last phone so I couldn't be charged with recieving them. Of course, plenty of people don't seem to care, and I can't switch to something else easily, so the system rolls forward, despite what seems to act like a trust, even if they don't actually meet to agree on set prices.
Of course I just got an EDGE iPhone, so I couldn't avoid them this time, but its $10 less than my old blackberry plan for basically the same thing (minus push data, plus 200 SMS), so I can't complain too much this time.
So basically all the detriments of working off of an existing design, while it seems almost deliberately avoiding any advantage that can be gained by it.
Of course, given that it's NASA, at the congressional level, the two goals are to keep/create jobs in certain districts and to maintain national prestige, both of which entail making the most "high-tech" (read complicated) system possible. Efficiency was never really in the equation.
While I agree that dumping money beyond the scope of COTS on SpaceX isn't going to make the situation better, I'll explain what I see as wrong with Ares.
Ares is not what it was supposed to be. It was to be a shuttle derived system capable of returning man to the moon at a reduced cost by using already existing infrastructure. Unfortunately, shuttle-derived seemed to be mostly ignored except enough to keep congress happy, by making it look its cobbled together from shuttle parts. However, they have changed every component so that they are having to re-engineer every component.
For instance, the current architecture has everything but the manned component on the massive Ares V. In order to make it powerful enough to do that, they had to add an extra segment to the SRBs. That doesn't sound too hard, except it changes all the combustion thermodynamics and fluid flow in the engine, forcing a complete redo of the design. Granted, the experience from the original SRBs will make them safer, but putting the LEM with the Orion capsule and launching only the Earth Departure Stage (EDS) on the V would have reduced the thrust needs. Similarly, the huge amount of thrust needed also made it so that the external tank is now 5.5 meters rather than 4.5 for the shuttle. This means thats the Michoud plant in New Orleans will have to be completely retooled, (with the roof raised or floor lowered as well) for something that's supposedly 'just the same.' The retooling will take 2 years, helping cause the gap thats gotten so much press, and also requiring massive layoffs that will be followed by massive hirings. If it weren't for the fact that the engineers and floor hands are going to require money in the meantime, this would be a great plan.
And of course, they keep underestimating the thrust needs; they recently had to add an extra engine to Ares V, and everytime I see something about Ares I, the Orion capsule is way over mass-budget. Granted, I can tell you immediately that my idea of moving the LEM to the capsules LV has issues with having to man-rate a larger vehicle, but its more for illustration that there were other architecutres that work around the issues. I really feel mostly that the current architecture is fine if you were starting from scratch, but it seemed to ignore any idea of working off of what we already have to get the best, cheapest system while minimizing the flight gap. If only Jupiter could get a chance...
I tend to handle diffraction in terms of Fourier optics, and the effects of the aperture shapes are defined by the Modulation Transfer Function (MTF).
This basically acts as a multiplicative mask for the Fourier transform of the image, and can be calculated as the convolution of the aperture function with itself. When you cut out small segments it has the effect of slightly reducing the MTF at whatever corresponding spatial frequency that is. The practical effects of this are minimal, with only small (~5%?) reductions over small intervals; if it really bothers someone they can correspondingly increase that component in post-processing, and the only change is a slight increase in noise.
Put more simply, it slightly reduces the components of the image corresponding to the spatial frequencies of the gaps, which is in most cases not a practical problem.
There's a difference between a segmented or even sparse primary mirror and an interferometer.
A telescope with a segmented mirror works almost exactly the same way as a normal telescope, except its easier to manufacture mirrors. Of course, this is with the cost of making it harder to keep aligned, and introduce unnecessary complexity for a small mirror, but as the sizes grow it becomes more and more cost effective to segment.
A sparse mirror with a well designed layout (say a Golay array) will be very effective also as a traditional telescope. The array is designed to gather all the spatial frequencies (think of a telescope as an analog Fourier transform) with as few elements as possible. Thus, though gathering less light, it will create an image of the same resolution. Of course less light leads to lower SNRs which can be tricky and is why you don't see too many sparse systems right now.
An interferometer, while conceptually similar to a sparse aperture system, only measures a single frequency component at a time, by taking the light from two distant telescopes and interfering them to determine the "fringes" (Young's experiment) which measure how similar the light beams are. It is thus very precise, but also very limited. Given enough time and patience you could move the relative positions of the telescopes to fill out the Fourier transform, but this is usually not very practical given that alignments need to be maintened within 10s of nanometers.
THere is no Flash implementation in the webbrowser. However, there is a built-in app that reads the videos directly from YouTube, which is very nice. Unfortunately, it also means other flash-based video sites (e.g. Hulu) are unavailable.
Actually, its not that they're not joining up, its that the XPC isn't happening this year as far as most people can tell.
I'd venture a guess that it'll be back next year though, and continue biannually in conjunction with the air show at the Air Force base there, although I'm not sure if we'll see a solo event again; if/when the whole private suborbital flight thing really takes off, I'd imagine it'll be shown off at things like Osh Kosh, where one of Diamandis's other ventures, Rocket Racing League, made its debut.
I like your first statement. I must say, as a Kindle owner I perfectly understand your point of view. Here's the way I see it
1. The cost was fine for me, but I'm also a young guy with a decent job so I've got some disposable income. 3. PDF's can't transfer well because of the size of the screen... I do wish there were an easy way to read technical papers on it though, I dont see it until the E-ink comes down in price and improves durability though. 4. Again, I've got adequate money right now, if its a book I really like and would want to lend, I'm at the point now where I can give gifts or buy a copy to lend... 5. The selection is a little frustrating, but it also gives me a chance to find things I may not read otherwise. I just finished Ken Follett's Pillars of the Earth, which I don't think I would have found otherwise, which would have been sad.
Now... for #2... I really wish they'd learn from the music guys. The simplicity of buying off the device itself makes it so that they shouldn't need DRM, and it being a smaller, generally more respectful market makes a difference as well; the small file size is the one difficulty. And of course the worst part is that unlike with music, theres no easy way to buy a book and rip it.
There are definitely some flaws, most notably the DRM issue, but since I still move around a lot and dont like having to carry boxes of books around, its great. Plus, I actually think its more comfortable to read than a book, since there are no awkward poses in bed trying to keep it open when your at the beginning or end of a paperback that simply does not want to stay open.
But saying all that, I can definitely see how its not for you or most people, and 240,000 seems pretty respectable.
Usually you can get blogs delivered automatically for about $1-2/month, or you can access them via the internet app for free, and its not too much more difficult if you set up google reader or something like that. Magazines like Time and Newsweek are $1.50/month.
Its not as bad as me... I called my roommate for next semester up last night to see about moving arrangements, and he was out there to watch the test, with my old roommate who works out there... and I was in Virginia.
I would say that their main innovations are business and engineering practices, rather than core technologies. Basically doing the old things with new computers and a focus on simplicity and efficiency (monetary, not fuel).
You have to remember, the military has a mission they're focused on and want to get the tools they need to complete. NASA's mission for the most part seems to be making sure they keep their budget.
Not saying that military contracting is a paragon of efficiency, but generally having a defined goal that everyone believes in helps a lot to keep you on track.
The basic difference is that PDF is designed to give you exact page layout, which is great for printing things out, while other formats like mobipocket are 'reflowable' and generally good for devices that arent the size of 8.5x11 paper. Differences otherwise I guess relate to feature sets, but those are the big ones.
I'd agree, but at this point I dont think the appeal is price. Its partially the coolness, like a nerdier iphone, and partially the convenience. I'm a student and move around a lot, so being able to keep a large collection of paperbacks without the necessary bulk of boxes is really appealing; of course, you still want real dead-trees for textbooks and such. I can also imagine if you fly a lot, its nice to be able to finish a book, hop on the internet, and buy a new one, rather than walk to the opposite terminal to find something at a shop.
That said, a better business model, particularly one without the DRM, would be nice and is still making me wonder whether I should buy one.
I know that its a well thought out position that I get the feeling she would follow through on. I can't cite any particular sources, but I did get to hear her space/science advisor speak at an AAS conference last year, and while she may not be particularly passionate about it, she has people working for her who are, and I imagine that they'd keep her honest on it. Especially since this was last November when she was still a clear frontrunner, and not desperate to say anything to get her ahead.
Note that I say this as a likely McCain supporter.
Fair enough, I was just going off graphs I remember seeing a few years ago in my aerodynamics courses. I'm more focused on spacecraft dynamics and those kind of things now, so I'm going to guess you know more than me.
A supersonic plane is already pretty stealthy sound-wise until its already gone over you. The Mach cone extends behind the vehicle so that you'll only hear it after its passed you, at which point if you care that its there its probably too late.
The big advantage would be to allow supersonic or hypersonic flights over continental landmasses. While it doesn't help the main issue of economics, it opens the business possibilities for cross country high-speed flights. Where I see this really opening up possibilities is hypersonic flight (M > 4~5) since the drag drops back down to subsonic levels, making fuel economy on par with the current crop of jet liners. Of course all the hypersonic combustion (scramjet) issues and the heating issues are still uhh, very non-trivial. I hate to know what a fleet of jets with titanium tipped, actively-cooled wings would cost.
I'm guessing it was a result of the usage of microsatellites for small satellites between 10 and 100 kg, which was colloquially below normal satellites and miniature satellites (100-500kg). Once you have that usage of micro its straightforward enough to define nano- and pico-sats as being the two orders of magnitude below that. Not strictly SI units, but I doubt the terms are going to change now since they have pretty well defined usages in the satellite community.
It depends on how long you mean. Its certainly still a long way from being able to run an interstellar mission, but for an interplanetary mission it provides a lot of benefits. Lower mass and faster travel times are the primary ones; even though its low thrust its constant thrust so it can build up, particularly on longer missions (think to Jupiter rather than the moon).
Also, the one problem I see with the idea of 'vacuuming' space, beyond the obvious engineering problems, is that in order to use them in a system you'd lose more momentum than you'd gain, at least using engine technology of this sort. Imagine it from the spacecrafts point of reference, all the very rarefied gas is coming towards it at the speed the spacecraft is traveling in the inertial frame. As it captures the gas, it has to slow it down to stationary, and then speed it up and send it back out; in doing so unless the exhaust velocity is faster than the spacecraft velocity, you're going to lose momentum rather than gain it.
Now if you could come up with a way to ionize the gas as it passes and use magnetic fields to accelerate it further (like a swimmer or an air-breathing engine) that would certainly be interesting.
Any kind of rocket propulsion will inherently have these limits. Whether its a chemical rocket at 3000m/s with lots of thrust, an ion thruster (which aren't that uncommon, not sure why the article says it is) with 30000m/s and fractions of newtons, or something advanced like VASMIR with high exit velocities and relatively high thrust (and large power requirements), you run into the basic problem that you have to carry all your fuel with you, and the thrust you get out of it is limited by the velocity of the fuel, for which the power requirements increase my v^2 (E=1/2 m v^2).
The only ways I can see to get away from this rather immutable law of nature is to use something like solar sails, which are cool but have a lot of engineering work still needing to be done, or designing a whole new kind of physics that lets us warp space to our needs. I'm pretty sure thats how even the impulse engines work on Star Trek, since if it wasn't, the Enterprise would probably have to be mostly fuel tanks. Of course if you're working on those physics, good luck, I hope you figure out.
Thinking about the problem for a second, I can see how you can make some rough calculations. Generally any GEO, HEO, etc. type orbit will be fairly slow, especially compared to the hyperbolic orbit that the asteroid will be entering at (in the Earth's reference). Thus based on the range of velocities and masses you could predict a range of possible perturbations to the orbit.
Though I don't have any numbers to back it up right now, a small perturbation in the velocity can propagate forward to be a very large error after 7 years. Thats why we have so much trouble predicting whether or not it will hit us; a 10 meter error in its position or a 1 m/s error in velocity measurements translates into multiple Earth radii over a few years. So combine the small change in velocity from an impact with the gravitational slingshot from the 2029 close approach, and it may be enough to shift the keyhole.
Of course I think the article is misleading, it may be more like there's a 1/450 chance of some kind of impact that will have an unknown effect on the orbit but may shift it into an impact trajectory, or something like that. At any rate, there are still other unknowns such as the effect of solar wind that can vary the trajectory dramatically too.
Note of course that I could be completely wrong, although I do plan to attempt some simulations now, since one of my advisors classes is working on a related project.
Thats actually the reason why the home-builts and experimentals are so popular. It takes a lot of work to make a new factory-built plane with all the new FAA regulations, thus why you don't see that many new Cessnas around.
However, if you just sell the parts and have the customer build it themselves, and attach a big 'EXPERIMENTAL' tag to the outside those regulations don't apply. Not that I'm arguing that this makes much sense, but from what I understand thats the situation.
(I don't have much firsthand knowledge, I just read up on this a lot a couple of years ago.)
That's exactly what they plan, having worked their table a couple of years ago at the X-Prize Cup. Peter Diamandis (X-Prize Foundation) and the rest of that gang are involved so their ultimate goal is to have a testing bed for new rocket technologies in the same way that Formula 1 and the rest develop automotive technologies.
Of course this is all with the provision that concept works in the first place... but then again I don't understand the popularity of watching car races either, so I can't really judge.
Slashdot Mirror
The basic process by which the mission is designed starts by defining the scientific scope, i.e. primary, secondary, etc. mission objectives. Based on those, you see which instruments and support devices you need to achieve each mission, and optimize the design to get the most of your objectives done within cost and reducing complexity. The reduction of complexity is important, because a project with a less than double the cost and double the "stuff" is not necessarily better because it probably has a higher likelihood of failure.
Of course, whether or not this is the right approach is a good question. Personally the idea of a huge number of incredibly cheap drones with a 10% success rate sounds especially appealing to me... but thats just me. The high cost of launch reduces the utility of that kind of model.
I can assure you, as a student at Texas A&M (I know one of Lemmon's students pretty well), that we are in fact very wet and windblown thanks to Ike. But, we got off class on Friday, so I can't complain too much.
I think you hit the nail on the head. The implicit collusion between the cell companies so that prices are the same and so that switching is difficult makes it so that refusing to use them when they charge that much is impossible. For instance, I certainly see the utility, for instance, setting up a quick lunch date while in class or giving directions in a crowded, loud bar or restaurant. However, I refuse to pay extra for something that shouldn't be, so I just don't use them, and even turned them off on my last phone so I couldn't be charged with recieving them. Of course, plenty of people don't seem to care, and I can't switch to something else easily, so the system rolls forward, despite what seems to act like a trust, even if they don't actually meet to agree on set prices.
Of course I just got an EDGE iPhone, so I couldn't avoid them this time, but its $10 less than my old blackberry plan for basically the same thing (minus push data, plus 200 SMS), so I can't complain too much this time.
So basically all the detriments of working off of an existing design, while it seems almost deliberately avoiding any advantage that can be gained by it. Of course, given that it's NASA, at the congressional level, the two goals are to keep/create jobs in certain districts and to maintain national prestige, both of which entail making the most "high-tech" (read complicated) system possible. Efficiency was never really in the equation.
While I agree that dumping money beyond the scope of COTS on SpaceX isn't going to make the situation better, I'll explain what I see as wrong with Ares.
Ares is not what it was supposed to be. It was to be a shuttle derived system capable of returning man to the moon at a reduced cost by using already existing infrastructure. Unfortunately, shuttle-derived seemed to be mostly ignored except enough to keep congress happy, by making it look its cobbled together from shuttle parts. However, they have changed every component so that they are having to re-engineer every component.
For instance, the current architecture has everything but the manned component on the massive Ares V. In order to make it powerful enough to do that, they had to add an extra segment to the SRBs. That doesn't sound too hard, except it changes all the combustion thermodynamics and fluid flow in the engine, forcing a complete redo of the design. Granted, the experience from the original SRBs will make them safer, but putting the LEM with the Orion capsule and launching only the Earth Departure Stage (EDS) on the V would have reduced the thrust needs. Similarly, the huge amount of thrust needed also made it so that the external tank is now 5.5 meters rather than 4.5 for the shuttle. This means thats the Michoud plant in New Orleans will have to be completely retooled, (with the roof raised or floor lowered as well) for something that's supposedly 'just the same.' The retooling will take 2 years, helping cause the gap thats gotten so much press, and also requiring massive layoffs that will be followed by massive hirings. If it weren't for the fact that the engineers and floor hands are going to require money in the meantime, this would be a great plan.
And of course, they keep underestimating the thrust needs; they recently had to add an extra engine to Ares V, and everytime I see something about Ares I, the Orion capsule is way over mass-budget. Granted, I can tell you immediately that my idea of moving the LEM to the capsules LV has issues with having to man-rate a larger vehicle, but its more for illustration that there were other architecutres that work around the issues. I really feel mostly that the current architecture is fine if you were starting from scratch, but it seemed to ignore any idea of working off of what we already have to get the best, cheapest system while minimizing the flight gap. If only Jupiter could get a chance...
I tend to handle diffraction in terms of Fourier optics, and the effects of the aperture shapes are defined by the Modulation Transfer Function (MTF).
This basically acts as a multiplicative mask for the Fourier transform of the image, and can be calculated as the convolution of the aperture function with itself. When you cut out small segments it has the effect of slightly reducing the MTF at whatever corresponding spatial frequency that is. The practical effects of this are minimal, with only small (~5%?) reductions over small intervals; if it really bothers someone they can correspondingly increase that component in post-processing, and the only change is a slight increase in noise.
Put more simply, it slightly reduces the components of the image corresponding to the spatial frequencies of the gaps, which is in most cases not a practical problem.
There's a difference between a segmented or even sparse primary mirror and an interferometer.
A telescope with a segmented mirror works almost exactly the same way as a normal telescope, except its easier to manufacture mirrors. Of course, this is with the cost of making it harder to keep aligned, and introduce unnecessary complexity for a small mirror, but as the sizes grow it becomes more and more cost effective to segment.
A sparse mirror with a well designed layout (say a Golay array) will be very effective also as a traditional telescope. The array is designed to gather all the spatial frequencies (think of a telescope as an analog Fourier transform) with as few elements as possible. Thus, though gathering less light, it will create an image of the same resolution. Of course less light leads to lower SNRs which can be tricky and is why you don't see too many sparse systems right now.
An interferometer, while conceptually similar to a sparse aperture system, only measures a single frequency component at a time, by taking the light from two distant telescopes and interfering them to determine the "fringes" (Young's experiment) which measure how similar the light beams are. It is thus very precise, but also very limited. Given enough time and patience you could move the relative positions of the telescopes to fill out the Fourier transform, but this is usually not very practical given that alignments need to be maintened within 10s of nanometers.
THere is no Flash implementation in the webbrowser. However, there is a built-in app that reads the videos directly from YouTube, which is very nice. Unfortunately, it also means other flash-based video sites (e.g. Hulu) are unavailable.
Actually, its not that they're not joining up, its that the XPC isn't happening this year as far as most people can tell.
I'd venture a guess that it'll be back next year though, and continue biannually in conjunction with the air show at the Air Force base there, although I'm not sure if we'll see a solo event again; if/when the whole private suborbital flight thing really takes off, I'd imagine it'll be shown off at things like Osh Kosh, where one of Diamandis's other ventures, Rocket Racing League, made its debut.
I like your first statement. I must say, as a Kindle owner I perfectly understand your point of view. Here's the way I see it
1. The cost was fine for me, but I'm also a young guy with a decent job so I've got some disposable income.
3. PDF's can't transfer well because of the size of the screen... I do wish there were an easy way to read technical papers on it though, I dont see it until the E-ink comes down in price and improves durability though.
4. Again, I've got adequate money right now, if its a book I really like and would want to lend, I'm at the point now where I can give gifts or buy a copy to lend...
5. The selection is a little frustrating, but it also gives me a chance to find things I may not read otherwise. I just finished Ken Follett's Pillars of the Earth, which I don't think I would have found otherwise, which would have been sad.
Now... for #2... I really wish they'd learn from the music guys. The simplicity of buying off the device itself makes it so that they shouldn't need DRM, and it being a smaller, generally more respectful market makes a difference as well; the small file size is the one difficulty. And of course the worst part is that unlike with music, theres no easy way to buy a book and rip it.
There are definitely some flaws, most notably the DRM issue, but since I still move around a lot and dont like having to carry boxes of books around, its great. Plus, I actually think its more comfortable to read than a book, since there are no awkward poses in bed trying to keep it open when your at the beginning or end of a paperback that simply does not want to stay open.
But saying all that, I can definitely see how its not for you or most people, and 240,000 seems pretty respectable.
Usually you can get blogs delivered automatically for about $1-2/month, or you can access them via the internet app for free, and its not too much more difficult if you set up google reader or something like that. Magazines like Time and Newsweek are $1.50/month.
Its not as bad as me... I called my roommate for next semester up last night to see about moving arrangements, and he was out there to watch the test, with my old roommate who works out there... and I was in Virginia.
I would say that their main innovations are business and engineering practices, rather than core technologies. Basically doing the old things with new computers and a focus on simplicity and efficiency (monetary, not fuel).
You have to remember, the military has a mission they're focused on and want to get the tools they need to complete. NASA's mission for the most part seems to be making sure they keep their budget. Not saying that military contracting is a paragon of efficiency, but generally having a defined goal that everyone believes in helps a lot to keep you on track.
The basic difference is that PDF is designed to give you exact page layout, which is great for printing things out, while other formats like mobipocket are 'reflowable' and generally good for devices that arent the size of 8.5x11 paper. Differences otherwise I guess relate to feature sets, but those are the big ones.
I'd agree, but at this point I dont think the appeal is price. Its partially the coolness, like a nerdier iphone, and partially the convenience. I'm a student and move around a lot, so being able to keep a large collection of paperbacks without the necessary bulk of boxes is really appealing; of course, you still want real dead-trees for textbooks and such. I can also imagine if you fly a lot, its nice to be able to finish a book, hop on the internet, and buy a new one, rather than walk to the opposite terminal to find something at a shop.
That said, a better business model, particularly one without the DRM, would be nice and is still making me wonder whether I should buy one.
I know that its a well thought out position that I get the feeling she would follow through on. I can't cite any particular sources, but I did get to hear her space/science advisor speak at an AAS conference last year, and while she may not be particularly passionate about it, she has people working for her who are, and I imagine that they'd keep her honest on it. Especially since this was last November when she was still a clear frontrunner, and not desperate to say anything to get her ahead.
Note that I say this as a likely McCain supporter.
Fair enough, I was just going off graphs I remember seeing a few years ago in my aerodynamics courses. I'm more focused on spacecraft dynamics and those kind of things now, so I'm going to guess you know more than me.
A supersonic plane is already pretty stealthy sound-wise until its already gone over you. The Mach cone extends behind the vehicle so that you'll only hear it after its passed you, at which point if you care that its there its probably too late.
The big advantage would be to allow supersonic or hypersonic flights over continental landmasses. While it doesn't help the main issue of economics, it opens the business possibilities for cross country high-speed flights. Where I see this really opening up possibilities is hypersonic flight (M > 4~5) since the drag drops back down to subsonic levels, making fuel economy on par with the current crop of jet liners. Of course all the hypersonic combustion (scramjet) issues and the heating issues are still uhh, very non-trivial. I hate to know what a fleet of jets with titanium tipped, actively-cooled wings would cost.
I'm guessing it was a result of the usage of microsatellites for small satellites between 10 and 100 kg, which was colloquially below normal satellites and miniature satellites (100-500kg). Once you have that usage of micro its straightforward enough to define nano- and pico-sats as being the two orders of magnitude below that. Not strictly SI units, but I doubt the terms are going to change now since they have pretty well defined usages in the satellite community.
It depends on how long you mean. Its certainly still a long way from being able to run an interstellar mission, but for an interplanetary mission it provides a lot of benefits. Lower mass and faster travel times are the primary ones; even though its low thrust its constant thrust so it can build up, particularly on longer missions (think to Jupiter rather than the moon).
Also, the one problem I see with the idea of 'vacuuming' space, beyond the obvious engineering problems, is that in order to use them in a system you'd lose more momentum than you'd gain, at least using engine technology of this sort. Imagine it from the spacecrafts point of reference, all the very rarefied gas is coming towards it at the speed the spacecraft is traveling in the inertial frame. As it captures the gas, it has to slow it down to stationary, and then speed it up and send it back out; in doing so unless the exhaust velocity is faster than the spacecraft velocity, you're going to lose momentum rather than gain it.
Now if you could come up with a way to ionize the gas as it passes and use magnetic fields to accelerate it further (like a swimmer or an air-breathing engine) that would certainly be interesting.
Any kind of rocket propulsion will inherently have these limits. Whether its a chemical rocket at 3000m/s with lots of thrust, an ion thruster (which aren't that uncommon, not sure why the article says it is) with 30000m/s and fractions of newtons, or something advanced like VASMIR with high exit velocities and relatively high thrust (and large power requirements), you run into the basic problem that you have to carry all your fuel with you, and the thrust you get out of it is limited by the velocity of the fuel, for which the power requirements increase my v^2 (E=1/2 m v^2).
The only ways I can see to get away from this rather immutable law of nature is to use something like solar sails, which are cool but have a lot of engineering work still needing to be done, or designing a whole new kind of physics that lets us warp space to our needs. I'm pretty sure thats how even the impulse engines work on Star Trek, since if it wasn't, the Enterprise would probably have to be mostly fuel tanks. Of course if you're working on those physics, good luck, I hope you figure out.
Thinking about the problem for a second, I can see how you can make some rough calculations. Generally any GEO, HEO, etc. type orbit will be fairly slow, especially compared to the hyperbolic orbit that the asteroid will be entering at (in the Earth's reference). Thus based on the range of velocities and masses you could predict a range of possible perturbations to the orbit.
Though I don't have any numbers to back it up right now, a small perturbation in the velocity can propagate forward to be a very large error after 7 years. Thats why we have so much trouble predicting whether or not it will hit us; a 10 meter error in its position or a 1 m/s error in velocity measurements translates into multiple Earth radii over a few years. So combine the small change in velocity from an impact with the gravitational slingshot from the 2029 close approach, and it may be enough to shift the keyhole.
Of course I think the article is misleading, it may be more like there's a 1/450 chance of some kind of impact that will have an unknown effect on the orbit but may shift it into an impact trajectory, or something like that. At any rate, there are still other unknowns such as the effect of solar wind that can vary the trajectory dramatically too.
Note of course that I could be completely wrong, although I do plan to attempt some simulations now, since one of my advisors classes is working on a related project.
Thats actually the reason why the home-builts and experimentals are so popular. It takes a lot of work to make a new factory-built plane with all the new FAA regulations, thus why you don't see that many new Cessnas around.
However, if you just sell the parts and have the customer build it themselves, and attach a big 'EXPERIMENTAL' tag to the outside those regulations don't apply. Not that I'm arguing that this makes much sense, but from what I understand thats the situation.
(I don't have much firsthand knowledge, I just read up on this a lot a couple of years ago.)
That's exactly what they plan, having worked their table a couple of years ago at the X-Prize Cup. Peter Diamandis (X-Prize Foundation) and the rest of that gang are involved so their ultimate goal is to have a testing bed for new rocket technologies in the same way that Formula 1 and the rest develop automotive technologies.
Of course this is all with the provision that concept works in the first place... but then again I don't understand the popularity of watching car races either, so I can't really judge.