That works pretty well, too (sorta like using the solar light energy, but it's probably easier to do)... the problem is, it only works in the neighborhood of a star, where there's a stellar wind that's significant. What if you want to keep accelerating, right into interstellar space?
The folks thinking up the laser-propelled systems have gotten into some pretty sophisticated concepts: for example, they've proposed using a gigantic Fresnel lens, free-flying between the starship and the laser battery, to focus the laser beam onto the lightsail once the starship has gotten far enough that the sail is smaller than the beam diameter. The lens flies toward the target star, too, but much slower than the starship...
They even propose multi-stage systems for deceleration at the far end -- you use concentric rings of sail, and let the outermost of them keep going... but you deform it so it reflects the light back at you, so you can decelerate... and even come back!. (Although it might be easier to do with yet another ring of lightsail.)
Needless to say, it makes control very interesting, when the object you're aiming at is lightyears away, and you wait years to see the effects of your corrections; some say it's impossible, but then so was heavier-than-air flight, a century ago.;>
What I got out of the BBC article was more along the lines of, "astronomers are now able to start looking at the differences among planetary nebulae, and so better understand the details of the process of carbon production."
While it's true that we've known about the carbon cycle and nucleogenesis of heavier elements for quite a while, we still haven't developed a very clear understanding of the details of the whole process by which those elements are formed and then returned to the interstellar medium. For an example, just look at this planetary nebula: the structure is extremely difficult to understand, but it's clearly the result of the changing behavior of the parent star's stellar winds and their interaction with the local ISM. We used to just say that elderly stars "shed a lot of gas and dust" to form planetary nebulae -- a simple, first-order concept that obviously can't survive pictures like this!
Similarly, we've only recently begun to run more sophisticated numerical models of the interior of stars, in which we actually account in detail for things like convection -- and we're finding that the interior of a star is probably as complex (and unexpected) as these planetary nebulae. The models also help us understand why material which should remain deep inside the star is expelled as efficiently as it is (the parent star doesn't explode, but sheds the material in some less-violent fashion... so how does the inside get outside?) -- we just don't have the simple "spherical symmetry" that the first-order concepts posited.
This sample of planetary nebulae from the Large Magellanic Cloud should help the astrophysicists make the next step up in theoretical complexity... and I think that concept is actually found in the BBC article, as simplistic as it is. (Because it's so basic, the article just can't spend much time on that level -- I suspect that's what grates on the more-educated here.)
Let's look at it another way. My sister works for Agilent (which used to be the scientific measurement divisions of HP), and I often listen to her describe some of the things the company does for its employees. And y'know, they appear to be actively nice to their employees -- almost as though they've figured it out: if they treat the employees decently, they'll have loyal, enthusiastic workers!
BTW, my sister happens to really enjoy working for Agilent... so it seems to be a successful approach. Maybe they're not alone in trying this approach?
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As Pogo said, "We have met the enemy..."
on
Database Nation
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...and they is us."
I think a big part of the problem is the ease of using our technology, and the tiny amount of attention we pay to it, ourselves! Here's an example:
About a year ago, I couldn't find my credit card when I tried to pay for a meal; after digging around in my wallet, I found it "filed" in the wrong slot. Because I was searching for a specific card (I have a few of 'em), I actually looked at the damned thing for the first time in weeks. It was someone else's card.
To make a long story short, I used the information on the card itself to turn it off (after I turned mine off, first!), then identify and find its owner. As it turned out, we'd used each other's cards for a week, since they were switched in another restaurant; each ran up several hundred dollars in purchases, without anyone checking the name or signature, and without once looking at the card ourselves.
It's so easy to use this technology, we simply don't think about it. The only ones who really pay attention to our behavior are the data collectors.
My point isn't to tell a somewhat-funny, somewhat-scary story; it's to encourage people to take back control of the technology. That necessarily includes the use of the technology for purposes other than their own. And so an important part of the story is this epilogue:
Both I and the other guy tried to fix the mixed-up expenditures by working with the two credit card companies. This proved almost impossible: we'd have had to cancel payment on all the cross-use purchases, then go back and repair the newly-inflicted damage ourselves. And there was no guarantee that doing this wouldn't cause bad posts to our credit ratings -- the companies were emphatic about this! So in the end, we did the simple thing: we tracked down all the purchases, and simply wrote each other checks to cover the balance.
We were both lucky that we were honest, but that's not the real point. The point is that the machine exists for the ultimate use of someone other than ourselves: we're just the grist the mill grinds. And if we don't watch out for ourselves, there's no one who will.
It occurred to me that I should expand that third point: remember that all this high-tech stuff is basically being hand-built, because there's no assembly-line volume required -- but there is still an enormous tooling cost associated with it. In other words, they have to make several identical parts (and I mean identical!), so they build dies and jigs and other miscellaneous tooling, pretty much as though they were going to do more production... and then all that tooling is worthless (but still charged to the project) after the half-dozen parts are built.
Think how much it would cost you to have a custom, high-tech titanium gas tank built for your Harley... and then consider that the tanks in the story are literally rocket science, rather than scooter parts.
There are at least four partial answers, matter of fact.
First, the hardware is being designed for human use in space, so there are an incredible number of specifications it must meet -- and each specification carries with it at least one test, and probably more. The final hardware must be certified as having been tested to each of these specs, and having passed. So a very large part of what's being paid for is the cost of meeting the required specs, and then maintaining the paperwork trail. (It's a common saying in the aerospace industry that you can't fly something until the paperwork weighs more than the vehicle; this is way too conservative for space stuff, though.)
Second, because it's space hardware, NASA is paying for it to be light weight; with each pound orbited by the Shuttle costing between $5K and $10K (depending on how you do the accounting, but I won't go there), time-consuming design work and lightweight-but-expensive construction is cheaper than orbiting a quickly-designed (and overdesigned), heavy version. Added to this is the complication that it is for space use, and there are design considerations you don't face here on earth (things like the zero-gee environment -- you have to stir liquid gasses, because there's no convection -- safety requirements for both on-orbit use and for transport in the Shuttle's cargo bay, and so on). All these add to the cost, too.
Third, the production run on these parts can be counted on the fingers of one hand, probably -- one set for the station, one or two sets of spares, and two or three more sets for testing here on earth. So there's no cost savings from amortizing the upfront engineering costs over a large production; it's all on the handful that are produced. And note that the cost of the ones used in testing is absorbed into the station set and the spares, too -- so they cost something like double what you might expect just from that alone.
Having said all that in defense of the cost, I do have to confess that it probably doesn't cover the entire price quoted in the article. There is no doubt a pretty fair chunk of the cost that exists solely because it's an aerospace contract for NASA; some of this is because they can get away with it, and some is because they have to put up with NASA being a pain in the ass... (I've worked on a number of contracts for NASA; it's hard to charge enough for PITA, because they are pros at it!). If the parts were spec'd, designed and built in-house, for a Boeing-funded project, I suspect they would cost a fraction of the quoted value -- even for the identical application.
And now that you know, I'm going to bet that it doesn't really make you feel all that much better, does it?
Your links point to a different technique for using lasers as part of a propulsion system: the laser heats the air that's inside the "combustion chamber" (quotes, because nothing actually burns), which then expands through a nozzle as with any rocket. The laser is providing the energy, instead of chemical reactions. They pulse the laser, so air flows back into the chamber between expansions. (Note that with this method, you must provide some source of gas -- an ablative lining, or somesuch -- at great altitudes where the air is too thin for this trick to work).
The news article describes a second method of laser propulsion, in which the momentum of the laser-generated photons are used directly: you bounce the photons off the "sail," and gain a tiny amount of momentum with each photon. This is very much like using a spinnaker sail, which is where the term "light sail" comes from. And because each photon has such a small momentum compared to the sail, it takes huge fluxes to cause a measurable accleration. This is why they talk about the elevated temperatures: they are throwing so much light at the sail that they're seriously heating it. (I glossed over the fact that you can make it work by absorbing the photon instead of reflecting it, which is actually what they appear to do -- with a loss in efficiency. So don't flame me, okay?)
Accelerations with proposed light sail vehicles are generally very small; they are effective because they are continuous, and the velocity builds up over time. This isn't completely novel, though -- we routinely account for the perturbing effects of sunlight on the orbits of spacecraft...
While I'm at it, I might as well point out that there are at least two other propulsion concepts which use lasers: laser-induced fusion concepts, where the laser is just the "trigger" and you use the heat from fusion to heat a working fluid (like more gas) or even directly exhaust the fusion products (definitely high-tech); and the ultimate propulsion system, where you "exhaust" nothing but light itself, substituting photons for atoms in your rocket (not the sort of thing you'd like to be behind, while it was working!).
There are plenty of cases I'm aware of where someone patented something that was already implemented. It's most common when the originator is small and fairly local, and the patenting body is a big company.
The big company almost always wins the lawsuit, too, if one is ever filed. Odd, that...
...saying that Galileo had not been [decontaminated], is not equivalent to saying that other probes had.
True -- NASA only decontaminates probes which go places they might plausibly expect life to exist, and not many people really thought that Europa would turn out to be one of those places (Arthur C. Clarke aside...). Now we know better. So far, not many probes have been decontaminated.
Does NASA know why the high gain antenna did not deploy? If so, why?
The reason for the failure isn't truly known -- Galileo was 37 million miles away when it occurred, a bit far to eyeball it -- but the best guess is that three of the 18 ribs of the antenna (it's an umbrella-like configuration) failed to deploy. They think that the standoff pins in the middle of the ribs became cocked, and locked in their sockets. I've heard speculation that it had to do with loss of dry lubricant due to vibration, since the spacecraft was transported around much more than was intended (Galileo was originally going to be launched shortly after the ill-fated Challenger mission, but was warehoused for years before Shuttle flew again; it also had a different transstage fitted, since part of the fallout from Challenger was that the original liquid-fuel rocket which would have injected Galileo into the transfer trajectory was redefined as too dangerous to fly on Shuttle, and they substituted a solid rocket system which delivered a smaller impulse; Galileo had to make multiple gravitational-whip maneuvers and take years longer to get to Jupiter).
See the High Gain Antenna FAQ for some info on this; there are good links for more detail within the FAQ.
I earlier read an article saying that even though the data stream would be slow, information could still be derived while Galileo was plummeting to it's death.
True; the real-time data rate now is three orders of magnitude lower than the high-gain antenna would have delivered (160 bps vs. 134.4 Kbps max rates), but at least some data might come back. The problem is, JPL did a hack where they now use the onboard processors to compress much of the science data before sending it through the low-gain antenna, and this takes time (the computers are old -- early 80's tech -- and can't do the compression real-time; it was never planned for the high-gain antenna transmission). Actual (uncompressed) data rates are probably more like 80 bps at this point, which means the data would be very sparse. I don't know what format the science data comes in, but I'll bet it's in at least 16-bit words, maybe 32-bit...
I read your post carefully; that's why I commented on it. You based your analysis of NASA's motives partly on the assumption that you guessed correctly about the Viking probes not being decontaminated.
I think you misunderstand the situation Galileo faces in Jovian orbit. Doing what they're presently doing with the probe is gaining us good information, and NASA can keep doing it for very little cost as long as things keep working. Problem is, they can't predict when a critical breakdown will take place and they'll lose control of the spacecraft. And if Galileo is no longer controlled, where it will wander in the Jovian system is anybody's guess. Collision with one of the four major moons has a higher probability, simply because they are the bigger targets.
They can't "just point the thing out into space" -- it doesn't have the fuel for an escape orbit. And if they relied on only gravitational slingshot maneuvers for an escape trajectory, they'd be flying very close to the moons, repeatedly, all the while risking collisions and expending plenty of fuel for midcourse corrections (and they still need to have control, while the failure clock is ticking). Besides, this would be a lengthy maneuver, and they'd waste observation time doing it.
Further, Galileo is crippled when it comes to transmitting data back to us -- remember, the high-gain antenna never deployed, so they're storing the data and beaming it back slowly, over extended periods of time, long after the observations are made. So if they deliberately send Galileo into Jupiter's atmosphere, it will take its data down with it when it burns... we'll never know what the instruments find, because there won't be time to send it back.
So there truly is no other reason to sacrifice the probe before its final hardware failure ends communication and control, except to protect Europa from possible contamination. And from NASA's point of view, this is a good reason to destroy the $1.5B spacecraft, which was my point. They take extraterrestrial life very seriously.
I understand the definition of "insight." Go back and re-read what you wrote: the concept of "truth" is inherent in "the inward or hidden nature of things." I also understand that your comment was moderated up as "insightful" -- clearly, you don't work for NASA and don't know first-hand why they're proposing this maneuver, which would be required for it to be "informative." You were just wrong when it came to your guess.
I'll also admit to being a little harsh -- but this is an area dear to my heart, because I don't get my hands on spacecraft often enough to satisfy me. So I'll apologize for busting your butt, if you'll recognize that my comment was mostly directed at the moderator instead of at you. Okay?
You'll understand that I feel just because they said Galileo didn't undergo decontamination doesn't mean that other spacecraft have. Certainly Viking had not, if this is only a modern phenomenon.
Actually, you're wrong. The Viking spacecraft were decontaminated before launch, expressly to avoid introducing terrestrial life to Mars (they also had life-detecting experiments which they ran on Mars, with results which have been controversial ever since).
The more recent landers (Pathfinder and the ill-fated Polar Lander) weren't as rigorously decontaminated as the Viking spacecraft, but they were still decontaminated.
BTW, just to forestall complaints: I happen to know this, because I worked on the Pathfinder spacecraft as a consultant. During that work, I had access to plenty of data from the Viking project -- the sterilization procedures for Viking were serious enough that parts of the system (the parachutes, for example) had to be specially designed to survive that alone!
This is not "posturing on NASA's part." NASA might have some problems, but they don't lack employees who are knowledgeable, aware, and concerned. There are few places in the Solar system where life might exist, and Mars (and now Europa) is among them. NASA pays attention to this.
I'd like to note that stuff like the preceeding post really don't deserve being moderated up; if you're going to moderate, do it on something you have knowledge of. Otherwise, you're wasting your points...
AFAIK, the Saturn V at the Cape wasn't flight-ready hardware (I think it was a tooling testbed). The other two were the last of the production run of boosters (NASA didn't want the Shuttle to have competition, it's said; pretty effective way of enforcing it).
My work takes me to JSC (Houston) and to the Cape from time to time, and I meet the people who really do the work. For the most part, they're dedicated, even pretty idealistic folks; they work where they do because it's the only space game in town, as far as I can tell. Hell, JSC is full of engineers who'd freely give body parts to be astronauts, but haven't made the cut yet (or will never, but can't stand to be away from it).
Their bosses, OTOH, are somewhat different... and their bosses are the ones who farm out the tourist crap. I won't even get into the political stuff...
This makes the ISS/Boeing story all the more offensive. I only wish there were some way to take those people I know, and let them loose on a modern version of the Apollo Program; we really ought to be able to use their talents and enthusiasm to accomplish something, rather than see them abused.
Unfortunately, NASA took the last two (perfectly good!) Saturn V's and laid them out as lawn ornaments in Houston and Huntsville. And we couldn't build another one now even if we wanted, because we've lost the technological infrastructure necessary to build them.
My real point: A lot has changed since the start of the Apollo Program. When I first started working in the aerospace industry, my boss was an old Apollo vet; he cared about everything he did, just as if it were still Apollo and the astronauts' lives (and our nation's prestige) depended on it. His boss, on the other hand, is the younger jerk who told me that the most important concept I could learn was to say, "That's not in scope."
At the root of it, that's what this present problem is: Boeing (just like all the other contractors) lowballs their bids, in the near-certain knowledge that changes will come down the pipe (often because of Congress, often because of NASA's own internal problems), and they'll be able to make back that money and a good bit of extra change with the "out-of-scope" modifications to the contract.
I think Boeing was just keeping quiet, waiting for this to happen, and they got caught when NASA held to the financial line drawn by Congress. And for its part, NASA doesn't have the money or the manpower to constantly monitor its contractors -- hell, they don't have the time to check their units, or run a complete end-to-end test series on a system (remember the last two Mars missions?).
Things are a mess on all sides: the system has fossilized. I want to get off this rock, too -- but I suspect the only way to make that happen is too do it with other like-minded adventurers, instead of waiting for NASA and the aerospace industry.
Now, does anyone know someone rich enough *cough*Gates*cough* to fund some real space exploration?
While I agree with Krauthammer also, I think it's important to recognize that the only reason NASA has as much budget as it presently does, is the Station. Remove that, and the idiots in Congress will remove all the funding associated with it -- and all that'll be left is the occasional $180M faster-cheaper (I refuse to say "better") mission. As it is, there are constant efforts to kill ISS (and NASA, too, pretty much).
Realistically, the only reason we were able to pull the Apollo program off was because it was really a Cold War effort, not simply a manifestation of mankind's enquiring spirit. Kennedy made a great speach, but it was propaganda. And when we'd definitely shown the Russians where they stood, the program was gutted, then cancelled.
OTOH, the American people were genuinely thrilled by the whole thing; as I recall, it wasn't lack of interest by the public that caused the networks not to broadcast the Apollo 13 launch, it was the networks' desire to pull in more advertising dollars. But the American public doesn't really run the show, do they? Congress has its own agenda, and I get the feeling that they don't want people to raise their eyes too high -- they'd rather folks kept their heads down, eating the bread and watching the circus.
Antiparticles "explode" when they combine with their matching particle (antielectrons - which are positrons - with electrons, for example), but not when they interact with photons (which are their own antiparticles, BTW). Particle/antiparticle pairs annihilate each other when they meet, and produce a pair of photons with equivalent energy.
You're right, they're working with single atoms, not the subatomic particles. If they could construct an "anti-atom" they could in principle do the same trick with it, but AFAIK only anti-hydrogen has been manufactured so far.
Well, you found precisely the paper I was referring to (it's the actual paper in question; I didn't know it was available without a subscription - I pay for the right, y'know). "Science Online" is the journal Science's online publication, at sciencemag.org.
Yeah, I guess it is dense... but then, my degree's in physics. I don't know offhand where to suggest you go for a lay explanation; the subject matter is moderately esoteric. You might try the online version of Science News where a more user-friendly version could appear within the next few weeks.
I took it as an analogy: with both MRI and the "microscope" in the article, you're not actually imaging your target directly, but measuring the effects on a probe and using sophisticated computer analysis to back out an image. In each case, the probe is light (the RF field and the laser); in each case, there's a resonant condition at the sample.
Like all analogies, though, it breaks down if you lean on it hard enough.
I think his point is valid, that with this new tool they're not imaging the atom directly. I understood you to be saying that in your first post, myself. The actual situation is quite different; if you've got access to Science Online, check the paper out (it's in the new issue). The Wired story really doesn't do it justice (oh wow, something new!).
Slashdot Mirror
The folks thinking up the laser-propelled systems have gotten into some pretty sophisticated concepts: for example, they've proposed using a gigantic Fresnel lens, free-flying between the starship and the laser battery, to focus the laser beam onto the lightsail once the starship has gotten far enough that the sail is smaller than the beam diameter. The lens flies toward the target star, too, but much slower than the starship...
They even propose multi-stage systems for deceleration at the far end -- you use concentric rings of sail, and let the outermost of them keep going... but you deform it so it reflects the light back at you, so you can decelerate... and even come back!. (Although it might be easier to do with yet another ring of lightsail.)
Needless to say, it makes control very interesting, when the object you're aiming at is lightyears away, and you wait years to see the effects of your corrections; some say it's impossible, but then so was heavier-than-air flight, a century ago. ;>
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While it's true that we've known about the carbon cycle and nucleogenesis of heavier elements for quite a while, we still haven't developed a very clear understanding of the details of the whole process by which those elements are formed and then returned to the interstellar medium. For an example, just look at this planetary nebula: the structure is extremely difficult to understand, but it's clearly the result of the changing behavior of the parent star's stellar winds and their interaction with the local ISM. We used to just say that elderly stars "shed a lot of gas and dust" to form planetary nebulae -- a simple, first-order concept that obviously can't survive pictures like this!
Similarly, we've only recently begun to run more sophisticated numerical models of the interior of stars, in which we actually account in detail for things like convection -- and we're finding that the interior of a star is probably as complex (and unexpected) as these planetary nebulae. The models also help us understand why material which should remain deep inside the star is expelled as efficiently as it is (the parent star doesn't explode, but sheds the material in some less-violent fashion... so how does the inside get outside?) -- we just don't have the simple "spherical symmetry" that the first-order concepts posited.
This sample of planetary nebulae from the Large Magellanic Cloud should help the astrophysicists make the next step up in theoretical complexity... and I think that concept is actually found in the BBC article, as simplistic as it is. (Because it's so basic, the article just can't spend much time on that level -- I suspect that's what grates on the more-educated here.)
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Let's look at it another way. My sister works for Agilent (which used to be the scientific measurement divisions of HP), and I often listen to her describe some of the things the company does for its employees. And y'know, they appear to be actively nice to their employees -- almost as though they've figured it out: if they treat the employees decently, they'll have loyal, enthusiastic workers!
BTW, my sister happens to really enjoy working for Agilent... so it seems to be a successful approach. Maybe they're not alone in trying this approach?
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I think a big part of the problem is the ease of using our technology, and the tiny amount of attention we pay to it, ourselves! Here's an example:
About a year ago, I couldn't find my credit card when I tried to pay for a meal; after digging around in my wallet, I found it "filed" in the wrong slot. Because I was searching for a specific card (I have a few of 'em), I actually looked at the damned thing for the first time in weeks. It was someone else's card.
To make a long story short, I used the information on the card itself to turn it off (after I turned mine off, first!), then identify and find its owner. As it turned out, we'd used each other's cards for a week, since they were switched in another restaurant; each ran up several hundred dollars in purchases, without anyone checking the name or signature, and without once looking at the card ourselves.
It's so easy to use this technology, we simply don't think about it. The only ones who really pay attention to our behavior are the data collectors.
My point isn't to tell a somewhat-funny, somewhat-scary story; it's to encourage people to take back control of the technology. That necessarily includes the use of the technology for purposes other than their own. And so an important part of the story is this epilogue:
Both I and the other guy tried to fix the mixed-up expenditures by working with the two credit card companies. This proved almost impossible: we'd have had to cancel payment on all the cross-use purchases, then go back and repair the newly-inflicted damage ourselves. And there was no guarantee that doing this wouldn't cause bad posts to our credit ratings -- the companies were emphatic about this! So in the end, we did the simple thing: we tracked down all the purchases, and simply wrote each other checks to cover the balance.
We were both lucky that we were honest, but that's not the real point. The point is that the machine exists for the ultimate use of someone other than ourselves: we're just the grist the mill grinds. And if we don't watch out for ourselves, there's no one who will.
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Think how much it would cost you to have a custom, high-tech titanium gas tank built for your Harley... and then consider that the tanks in the story are literally rocket science, rather than scooter parts.
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First, the hardware is being designed for human use in space, so there are an incredible number of specifications it must meet -- and each specification carries with it at least one test, and probably more. The final hardware must be certified as having been tested to each of these specs, and having passed. So a very large part of what's being paid for is the cost of meeting the required specs, and then maintaining the paperwork trail. (It's a common saying in the aerospace industry that you can't fly something until the paperwork weighs more than the vehicle; this is way too conservative for space stuff, though.)
Second, because it's space hardware, NASA is paying for it to be light weight; with each pound orbited by the Shuttle costing between $5K and $10K (depending on how you do the accounting, but I won't go there), time-consuming design work and lightweight-but-expensive construction is cheaper than orbiting a quickly-designed (and overdesigned), heavy version. Added to this is the complication that it is for space use, and there are design considerations you don't face here on earth (things like the zero-gee environment -- you have to stir liquid gasses, because there's no convection -- safety requirements for both on-orbit use and for transport in the Shuttle's cargo bay, and so on). All these add to the cost, too.
Third, the production run on these parts can be counted on the fingers of one hand, probably -- one set for the station, one or two sets of spares, and two or three more sets for testing here on earth. So there's no cost savings from amortizing the upfront engineering costs over a large production; it's all on the handful that are produced. And note that the cost of the ones used in testing is absorbed into the station set and the spares, too -- so they cost something like double what you might expect just from that alone.
Having said all that in defense of the cost, I do have to confess that it probably doesn't cover the entire price quoted in the article. There is no doubt a pretty fair chunk of the cost that exists solely because it's an aerospace contract for NASA; some of this is because they can get away with it, and some is because they have to put up with NASA being a pain in the ass... (I've worked on a number of contracts for NASA; it's hard to charge enough for PITA, because they are pros at it!). If the parts were spec'd, designed and built in-house, for a Boeing-funded project, I suspect they would cost a fraction of the quoted value -- even for the identical application.
And now that you know, I'm going to bet that it doesn't really make you feel all that much better, does it?
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The news article describes a second method of laser propulsion, in which the momentum of the laser-generated photons are used directly: you bounce the photons off the "sail," and gain a tiny amount of momentum with each photon. This is very much like using a spinnaker sail, which is where the term "light sail" comes from. And because each photon has such a small momentum compared to the sail, it takes huge fluxes to cause a measurable accleration. This is why they talk about the elevated temperatures: they are throwing so much light at the sail that they're seriously heating it. (I glossed over the fact that you can make it work by absorbing the photon instead of reflecting it, which is actually what they appear to do -- with a loss in efficiency. So don't flame me, okay?)
Accelerations with proposed light sail vehicles are generally very small; they are effective because they are continuous, and the velocity builds up over time. This isn't completely novel, though -- we routinely account for the perturbing effects of sunlight on the orbits of spacecraft...
While I'm at it, I might as well point out that there are at least two other propulsion concepts which use lasers: laser-induced fusion concepts, where the laser is just the "trigger" and you use the heat from fusion to heat a working fluid (like more gas) or even directly exhaust the fusion products (definitely high-tech); and the ultimate propulsion system, where you "exhaust" nothing but light itself, substituting photons for atoms in your rocket (not the sort of thing you'd like to be behind, while it was working!).
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The big company almost always wins the lawsuit, too, if one is ever filed. Odd, that...
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True -- NASA only decontaminates probes which go places they might plausibly expect life to exist, and not many people really thought that Europa would turn out to be one of those places (Arthur C. Clarke aside...). Now we know better. So far, not many probes have been decontaminated.
Does NASA know why the high gain antenna did not deploy? If so, why?
The reason for the failure isn't truly known -- Galileo was 37 million miles away when it occurred, a bit far to eyeball it -- but the best guess is that three of the 18 ribs of the antenna (it's an umbrella-like configuration) failed to deploy. They think that the standoff pins in the middle of the ribs became cocked, and locked in their sockets. I've heard speculation that it had to do with loss of dry lubricant due to vibration, since the spacecraft was transported around much more than was intended (Galileo was originally going to be launched shortly after the ill-fated Challenger mission, but was warehoused for years before Shuttle flew again; it also had a different transstage fitted, since part of the fallout from Challenger was that the original liquid-fuel rocket which would have injected Galileo into the transfer trajectory was redefined as too dangerous to fly on Shuttle, and they substituted a solid rocket system which delivered a smaller impulse; Galileo had to make multiple gravitational-whip maneuvers and take years longer to get to Jupiter).
See the High Gain Antenna FAQ for some info on this; there are good links for more detail within the FAQ.
I earlier read an article saying that even though the data stream would be slow, information could still be derived while Galileo was plummeting to it's death.
True; the real-time data rate now is three orders of magnitude lower than the high-gain antenna would have delivered (160 bps vs. 134.4 Kbps max rates), but at least some data might come back. The problem is, JPL did a hack where they now use the onboard processors to compress much of the science data before sending it through the low-gain antenna, and this takes time (the computers are old -- early 80's tech -- and can't do the compression real-time; it was never planned for the high-gain antenna transmission). Actual (uncompressed) data rates are probably more like 80 bps at this point, which means the data would be very sparse. I don't know what format the science data comes in, but I'll bet it's in at least 16-bit words, maybe 32-bit...
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I think you misunderstand the situation Galileo faces in Jovian orbit. Doing what they're presently doing with the probe is gaining us good information, and NASA can keep doing it for very little cost as long as things keep working. Problem is, they can't predict when a critical breakdown will take place and they'll lose control of the spacecraft. And if Galileo is no longer controlled, where it will wander in the Jovian system is anybody's guess. Collision with one of the four major moons has a higher probability, simply because they are the bigger targets.
They can't "just point the thing out into space" -- it doesn't have the fuel for an escape orbit. And if they relied on only gravitational slingshot maneuvers for an escape trajectory, they'd be flying very close to the moons, repeatedly, all the while risking collisions and expending plenty of fuel for midcourse corrections (and they still need to have control, while the failure clock is ticking). Besides, this would be a lengthy maneuver, and they'd waste observation time doing it.
Further, Galileo is crippled when it comes to transmitting data back to us -- remember, the high-gain antenna never deployed, so they're storing the data and beaming it back slowly, over extended periods of time, long after the observations are made. So if they deliberately send Galileo into Jupiter's atmosphere, it will take its data down with it when it burns... we'll never know what the instruments find, because there won't be time to send it back.
So there truly is no other reason to sacrifice the probe before its final hardware failure ends communication and control, except to protect Europa from possible contamination. And from NASA's point of view, this is a good reason to destroy the $1.5B spacecraft, which was my point. They take extraterrestrial life very seriously.
I understand the definition of "insight." Go back and re-read what you wrote: the concept of "truth" is inherent in "the inward or hidden nature of things." I also understand that your comment was moderated up as "insightful" -- clearly, you don't work for NASA and don't know first-hand why they're proposing this maneuver, which would be required for it to be "informative." You were just wrong when it came to your guess.
I'll also admit to being a little harsh -- but this is an area dear to my heart, because I don't get my hands on spacecraft often enough to satisfy me. So I'll apologize for busting your butt, if you'll recognize that my comment was mostly directed at the moderator instead of at you. Okay?
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Actually, you're wrong. The Viking spacecraft were decontaminated before launch, expressly to avoid introducing terrestrial life to Mars (they also had life-detecting experiments which they ran on Mars, with results which have been controversial ever since).
The more recent landers (Pathfinder and the ill-fated Polar Lander) weren't as rigorously decontaminated as the Viking spacecraft, but they were still decontaminated.
BTW, just to forestall complaints: I happen to know this, because I worked on the Pathfinder spacecraft as a consultant. During that work, I had access to plenty of data from the Viking project -- the sterilization procedures for Viking were serious enough that parts of the system (the parachutes, for example) had to be specially designed to survive that alone!
This is not "posturing on NASA's part." NASA might have some problems, but they don't lack employees who are knowledgeable, aware, and concerned. There are few places in the Solar system where life might exist, and Mars (and now Europa) is among them. NASA pays attention to this.
I'd like to note that stuff like the preceeding post really don't deserve being moderated up; if you're going to moderate, do it on something you have knowledge of. Otherwise, you're wasting your points...
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Sorry 'bout that! (at least you made me look)
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My work takes me to JSC (Houston) and to the Cape from time to time, and I meet the people who really do the work. For the most part, they're dedicated, even pretty idealistic folks; they work where they do because it's the only space game in town, as far as I can tell. Hell, JSC is full of engineers who'd freely give body parts to be astronauts, but haven't made the cut yet (or will never, but can't stand to be away from it).
Their bosses, OTOH, are somewhat different... and their bosses are the ones who farm out the tourist crap. I won't even get into the political stuff...
This makes the ISS/Boeing story all the more offensive. I only wish there were some way to take those people I know, and let them loose on a modern version of the Apollo Program; we really ought to be able to use their talents and enthusiasm to accomplish something, rather than see them abused.
It's a damned shame.
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My real point: A lot has changed since the start of the Apollo Program. When I first started working in the aerospace industry, my boss was an old Apollo vet; he cared about everything he did, just as if it were still Apollo and the astronauts' lives (and our nation's prestige) depended on it. His boss, on the other hand, is the younger jerk who told me that the most important concept I could learn was to say, "That's not in scope."
At the root of it, that's what this present problem is: Boeing (just like all the other contractors) lowballs their bids, in the near-certain knowledge that changes will come down the pipe (often because of Congress, often because of NASA's own internal problems), and they'll be able to make back that money and a good bit of extra change with the "out-of-scope" modifications to the contract.
I think Boeing was just keeping quiet, waiting for this to happen, and they got caught when NASA held to the financial line drawn by Congress. And for its part, NASA doesn't have the money or the manpower to constantly monitor its contractors -- hell, they don't have the time to check their units, or run a complete end-to-end test series on a system (remember the last two Mars missions?).
Things are a mess on all sides: the system has fossilized. I want to get off this rock, too -- but I suspect the only way to make that happen is too do it with other like-minded adventurers, instead of waiting for NASA and the aerospace industry.
Now, does anyone know someone rich enough *cough*Gates*cough* to fund some real space exploration?
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Realistically, the only reason we were able to pull the Apollo program off was because it was really a Cold War effort, not simply a manifestation of mankind's enquiring spirit. Kennedy made a great speach, but it was propaganda. And when we'd definitely shown the Russians where they stood, the program was gutted, then cancelled.
OTOH, the American people were genuinely thrilled by the whole thing; as I recall, it wasn't lack of interest by the public that caused the networks not to broadcast the Apollo 13 launch, it was the networks' desire to pull in more advertising dollars. But the American public doesn't really run the show, do they? Congress has its own agenda, and I get the feeling that they don't want people to raise their eyes too high -- they'd rather folks kept their heads down, eating the bread and watching the circus.
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You're right, they're working with single atoms, not the subatomic particles. If they could construct an "anti-atom" they could in principle do the same trick with it, but AFAIK only anti-hydrogen has been manufactured so far.
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Yeah, I guess it is dense... but then, my degree's in physics. I don't know offhand where to suggest you go for a lay explanation; the subject matter is moderately esoteric. You might try the online version of Science News where a more user-friendly version could appear within the next few weeks.
Otherwise, if I find something I'll post it here.
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Like all analogies, though, it breaks down if you lean on it hard enough.
I think his point is valid, that with this new tool they're not imaging the atom directly. I understood you to be saying that in your first post, myself. The actual situation is quite different; if you've got access to Science Online, check the paper out (it's in the new issue). The Wired story really doesn't do it justice (oh wow, something new!).
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