it would only have to be deflected a very miniscule amount.
yea, you're right. I acknowledged this error on another post.
Re:Depends on how the laser works.
on
Spy Fly
·
· Score: 1
You do realize, theres alot more solar energy in space than there is on earth?
not so much more, the energy density is only several times more. But you can harvest much larger areeas.
You do realize there are particles in space, waves carrying these particles allow solar sails to travel as such great speeds.
I assume you mean the solar wind. It's energy density is actully very low: the particles are high-energy, but there are not a lot of them.
In space, you should in theory be able to create a laser thousands of times more powerful than it would be if its on earth, due to the fact that if done right, the suns energy could be harnessed.
how exactly ? the physical characteristics of the laser would have to be the same (lasers are based on population-inversion of some medium, which is a very delicate quantum phenomena. I don't know of a machinery directly using crude sunlight to do this, correct me if I'm wrong).
The real difference is that there is no atmosphere, which limits the power passing through it (see below on non-linear phenomena), but don't forget, that the laser light will have to pass through the gases and plasma emmited from the asteroid for thrust (the explosion remnants). when a very strong laser light passes through a dense medium it goes through non-linear effects which may cause the beam to implode, split, and miss the asteroid entirely (for more info lookup the non-linear Schroedinger equation, implosions and multiple-filamentations in non-linear kerr medium).
Also theres other ways, you could simply use more than one laser aimed at the same target to increase how effective the laser is.
true that, but it does not solve the problems of hitting the asteroid from a distance and through the emitted gasses/plasma.
as for the site of the USAF, and this relates to another discussion we had, I belive a battery of high-power lasers on the moon is much more likely to be used for military purposes than for deflecting large asteroids...
it can be used, though, to send a light sail with a nuke to the asteroid. much more efficient usage of energy.
Re:This technology is evil
on
Spy Fly
·
· Score: 1
Im sorry but there is absolutely no way in hell this technology could ever be used for anything good
absolutely nothing like:
finding out and destroying agricultural pests ? much more efficient seeding techniques (of fields) ? cleaning up non-biodegradeable material from dumps ?
like there is allways a way to abuse technology, there are allways ways to use it for good.
Re:You dont need nuke to do that
on
Spy Fly
·
· Score: 1
A laser cannon could deflect the astriod, the laser could literally beam the astriod and deflect it off its course
see a rough calculation of the amount of energy needed to stop such an asteroid here.
deflecting the asteroid may need about 1/10000 of this amount, but not much less . This is about 30 megaton TNT worth of energy.
IIRC laser efficiency is never more than several percent, even if you "shoot" from orbit (no atmospheric losses) and manage to hit the asteroid perfectly from tens of millions of killometers (highly unlikely), you will not be able to deflect an asteroid of this magnitude with a laser, much less evaporate it.
(and BTW, IIRC, the strongest lasers are X-ray lasers produced by nuclear explosions)
crawling into people's houses, looking and listening to everything happening in every room
I'm going to risk some karma here, and suggest you're barking up the wrong tree here:
surveilance devices allready exists, they are very cheap and use realy old-fashioned technology (remember Orwell's 1984 was written >60 years ago )
and to the extent the (any) goverment wants to control the ordinary people's lives they can allready do this technologically and financially.
IMHO, the issues of privacy and citizen-state relationship are not technological by nature, but are political issues, and technology rarely changes them. the only possible exception to the above is of encryption technology. But as for being afraid of miniature mechanical bugs listening to our conversations / sexual activities / whatever I say nothing has changed. The goverment allready has practically indetectable bugs...
so, contrary to common geek belief, technology will nither greatly help nor greatly impede you in your civil-rights struggle. It's not a technology issue.
but that's just my non-expert oppinion, lets wait and see...
well, TDA is one of the greatest, most imaginative, SF books ever, but maybe they got the idea from researching insect flight...
incredibly interesting science
on
Spy Fly
·
· Score: 1
the fluid-dynamical problems in insect flying are a hard, very much still in research physical problem.
this is the most interesting aspect of this project, and it's a pity/. responses overlook the serious stuff.
for those interested, there was a Sci. Am. article on robotic insect-flight several months ago.
you're right, for the wrong reasons
on
Back to the Moon?
·
· Score: 2
yes, we definately need a moon base, but only for mining purposes.
1) space fabrication will benefit much more from microgravity: build them in orbit, then use centrifugal forces for whatever gravity you wish.
2) solar-power-satellites can be built with much less resources (and less fuss) in microgravity: build them in orbit.
3) the moon AFAIK is mainly made of Si, O, N and some C (not in that order) what is really missing is Hydrogen, which you can provide by bringing small asteroids/comets back to near-earth orbit. (landing them on the moon in one piece is much harder...)
so, to summarize: yes, the human race very much needs a moon base, but not as a standalone project, but as part of a larger free-space colonizaiton and industrialization effort.
2002 has been the worst year out of the nearly 40 I've seen
I'm (was) a permanent reader of LWN and will sorely miss them (I also donated when I could), but come on, in the last 40 years there had been wars, famine and disease that killed and maimed hundreds of millions of people worldwide ; some of these events I find a bit worse then closing of my favourite magazine.
2002 wasn't very bright so far, but it also wasn't the gloomiest.
You didn't account for the inefficiency factor... one half of the solid angle at the bomb would be outer space so you loose 1/2 the energy right there
Right, but this was an O.O.M. calculation anyway, factors less than 10 I don't take into account.
a lot of the energy doesn't go into momentum change but it other stuff like melting, heating, or break up the rock
My guess is you're wrong there: Since the energies at the boundry of the rock are at least ~ 10eV the important processes are ablation of the rock and thermal expansion of the gas. The energy difference is so large at such a short time these processes would probably be adiabatic. melting occurs at ~0.1 eV, breaking and other solid-state phenomena at even lower energies, by the time you're at such energies most of the energy is far gone.
In short, the major processes are probably adiabatic, so my calculation still seems reasonable, even conservative, since I did not consider mass loss due to ablation.
I made one serious error, though: I calculated how much would it take to STOP the asteroid, when all you need is to deflect it far enough...
actually I'm not sure how much solid debries stays after a thermonuclear explosion.
anything the size of a sand-grain and below will be ionized by UV radiation from sun and caught in the sun-wind (it has it's own embeded magnetic field), and is therefore not a problem.
and my guess is most of the debries mass will not be larger; however you're right in saying this does constitutes a problem, not so much to earth (the large chunks you can detect, smaller will burn in atmosphere), as to spaceships and sattelites.
note, also, the original poster said such a feat is impossible in today's technology, and my answer is this does not seem impossible, just very costly and undesirable; it should only be done if the asteroid is on a confirmed collision course with earth. In that case, several megaton sized explosions on earth and a serious future problem for spacecraft are a small cost compared with total-asteroid impact...
some of the strange priorities of universities stems from dedicated donations: the university must BY CONTRACT use the money from a specific donation in a specific way.
so, if someone decided to give a donation for such a specific project, it doesn't matter that the money would be 100X time more usefull in adding to the local library, since they can't use the money that way.
it's a pitty, because many times the sexy subjects are by far not the effective ones.
the only out of this energy mess, besides a huge drop in human populatiom, is fusion
wrong. as a student in plasma-physics I am all for fusion-research, but I very much doubt we'll have commercially viable fusion reactors in less than 30 years. Actually a proof-of concept break-even machine has not been develloped yet (though the advances were enourmous). Fusion reactors are not fully a technology-problem yet, there is still much basic scientific research involved.
but we have an alternative: SPS (Solar Power Satelites) : they can utilize conventional turbine-generator techniques at a large scale, and beam the power as microwaves down to earth.
there is no new, yet to be researched science in SPS (as opposed to fusion), the only problem is financial: get the investment to start mining the asteroid belt.
for a rocket, every component has to work right, every combination of components has to work right, for every step in the launch sequence, for every pressure, temperature, vibration-mode...
and those are the things a layman (me) thought of just at first glance, I'm sure there are more.
since there are a lot of components, there are even far more combinations and configurations to test. This SHOULD be done by rocket scientists and technitians, not by (even knowledgeable) amatures, and should be done many times over for each configuration, to increase the level of statistical confidence (remember sigma ~ 1/sqrt(N) )
in short QA of critical systems is a very large-scale labor-intensive problem, I don't believe one man can do this alone reasonably well, and even should he by some miracle succeed, I will NOT take the next rocket up.
You do realize, right, that this is exactly the FreeBSD release method? wrong, I actually don't know the BSD dev-model.
(3) is STABLE, (2) is RELEASE, and (1) is CURRENT. but if I understand correctly the meaning of RELEASE label, it is for testing purposes only, while I suggest 2 branches for both dev and QA, only the scales differ.
then when you approach a "freeze" (updating 1->2 or 2->3 ) you will need a short-lived release-candidate branch for each.
I know all the arguments about how it is a "stable" series and all
but you want to discard stability of a STABLE branch for features - not a great deal for users who wish to actually use the system.
- but some people want new features, and 2.5 is not an option, thanks to IDE being owned by Martin
have you considered that IDE instabilities are in 2.5 because this is where new features and engineering reforms should be done, regardless of who is the maintainer ?
my belief: there should be a split to 3 branches:
1) long-term dev-branch: this branch is where large-scale (>months) changes are made and tested.
2) medium and short-term dev-branch: this branch is what you're looking for, where features and fixes which take months or less are made and tested, really tested, not like the 2.4 VM fiascos, before becoming stable.
3) stable branch: this branch changes once a year or less, except for very minor bug/security fixes.
changes will NOT be imported directly from 1->3, only 1->2 , 2->1 and 2->3 .
this will give you both stability for those who need it, long-term dev and testing environemnt for the systemic reformers, and short-term devellopment for the medium- to small-scale changes.
and before anyone of you jumps and shouts "but this is exactly the debian model of stable, testing, unstable branches" I say that both branch 1 AND 2 are dev. AND testing branches, the criterion sugested is the changes scale, not the targeted audience (though ususally decisions may be similar between models).
Slashdot Mirror
it would only have to be deflected a very miniscule amount.
yea, you're right. I acknowledged this error on another post.
You do realize, theres alot more solar energy in space than there is on earth?
not so much more, the energy density is only several times more. But you can harvest much larger areeas.
You do realize there are particles in space, waves carrying these particles allow solar sails to travel as such great speeds.
I assume you mean the solar wind. It's energy density is actully very low: the particles are high-energy, but there are not a lot of them.
In space, you should in theory be able to create a laser thousands of times more powerful than it would be if its on earth, due to the fact that if done right, the suns energy could be harnessed.
how exactly ? the physical characteristics of the laser would have to be the same (lasers are based on population-inversion of some medium, which is a very delicate quantum phenomena. I don't know of a machinery directly using crude sunlight to do this, correct me if I'm wrong).
The real difference is that there is no atmosphere, which limits the power passing through it (see below on non-linear phenomena), but don't forget, that the laser light will have to pass through the gases and plasma emmited from the asteroid for thrust (the explosion remnants).
when a very strong laser light passes through a dense medium it goes through non-linear effects which may cause the beam to implode, split, and miss the asteroid entirely (for more info lookup the non-linear Schroedinger equation, implosions and multiple-filamentations in non-linear kerr medium).
Also theres other ways, you could simply use more than one laser aimed at the same target to increase how effective the laser is.
true that, but it does not solve the problems of hitting the asteroid from a distance and through the emitted gasses/plasma.
as for the site of the USAF, and this relates to another discussion we had, I belive a battery of high-power lasers on the moon is much more likely to be used for military purposes than for deflecting large asteroids...
it can be used, though, to send a light sail with a nuke to the asteroid. much more efficient usage of energy.
Im sorry but there is absolutely no way in hell this technology could ever be used for anything good
:
absolutely nothing like
finding out and destroying agricultural pests ?
much more efficient seeding techniques (of fields) ?
cleaning up non-biodegradeable material from dumps ?
like there is allways a way to abuse technology, there are allways ways to use it for good.
A laser cannon could deflect the astriod, the laser could literally beam the astriod and deflect it off its course
see a rough calculation of the amount of energy needed to stop such an asteroid
here.
deflecting the asteroid may need about 1/10000 of this amount, but not much less . This is about 30 megaton TNT worth of energy.
IIRC laser efficiency is never more than several percent, even if you "shoot" from orbit (no atmospheric losses) and manage to hit the asteroid perfectly from tens of millions of killometers (highly unlikely), you will not be able to deflect an asteroid of this magnitude with a laser, much less evaporate it.
(and BTW, IIRC, the strongest lasers are X-ray lasers produced by nuclear explosions)
could be a great weapon once they figure out how to attach the big friggin' laser to it's head.
not laser, poison.
crawling into people's houses, looking and listening to everything happening in every room
...
...
I'm going to risk some karma here, and suggest you're barking up the wrong tree here:
surveilance devices allready exists, they are very cheap and use realy old-fashioned technology (remember Orwell's 1984 was written >60 years ago )
and to the extent the (any) goverment wants to control the ordinary people's lives they can allready do this technologically and financially.
IMHO, the issues of privacy and citizen-state relationship are not technological by nature, but are political issues, and technology rarely changes them.
the only possible exception to the above is of encryption technology. But as for being afraid of miniature mechanical bugs listening to our conversations / sexual activities / whatever I say nothing has changed. The goverment allready has practically indetectable bugs
so, contrary to common geek belief, technology will nither greatly help nor greatly impede you in your civil-rights struggle. It's not a technology issue.
but that's just my non-expert oppinion, lets wait and see
well, TDA is one of the greatest, most imaginative, SF books ever, but maybe they got the idea from researching insect flight
the fluid-dynamical problems in insect flying are a hard, very much still in research physical problem.
/. responses overlook the serious stuff.
this is the most interesting aspect of this project, and it's a pity
for those interested, there was a Sci. Am. article on robotic insect-flight several months ago.
yes, we definately need a moon base, but only for mining purposes.
...)
1) space fabrication will benefit much more from microgravity: build them in orbit, then use centrifugal forces for whatever gravity you wish.
2) solar-power-satellites can be built with much less resources (and less fuss) in microgravity: build them in orbit.
3) the moon AFAIK is mainly made of Si, O, N and some C (not in that order) what is really missing is Hydrogen, which you can provide by bringing small asteroids/comets back to near-earth orbit. (landing them on the moon in one piece is much harder
so, to summarize: yes, the human race very much needs a moon base, but not as a standalone project, but as part of a larger free-space colonizaiton and industrialization effort.
2002 has been the worst year out of the nearly 40 I've seen
.
I'm (was) a permanent reader of LWN and will sorely miss them (I also donated when I could), but come on, in the last 40 years there had been wars, famine and disease that killed and maimed hundreds of millions of people worldwide ; some of these events I find a bit worse then closing of my favourite magazine
2002 wasn't very bright so far, but it also wasn't the gloomiest.
You didn't account for the inefficiency factor ...
...
one half of the solid angle at the bomb would be outer space so you loose 1/2 the energy right there
Right, but this was an O.O.M. calculation anyway, factors less than 10 I don't take into account.
a lot of the energy doesn't go into momentum change but it other stuff like melting, heating, or break up the rock
My guess is you're wrong there: Since the energies at the boundry of the rock are at least ~ 10eV the important processes are ablation of the rock and thermal expansion of the gas. The energy difference is so large at such a short time these processes would probably be adiabatic. melting occurs at ~0.1 eV, breaking and other solid-state phenomena at even lower energies, by the time you're at such energies most of the energy is far gone.
In short, the major processes are probably adiabatic, so my calculation still seems reasonable, even conservative, since I did not consider mass loss due to ablation.
I made one serious error, though: I calculated how much would it take to STOP the asteroid, when all you need is to deflect it far enough
please login and say thankyouon the comments page.
give thanks where thanks is due.
actually I'm not sure how much solid debries stays after a thermonuclear explosion.
...
anything the size of a sand-grain and below will be ionized by UV radiation from sun and caught in the sun-wind (it has it's own embeded magnetic field), and is therefore not a problem.
and my guess is most of the debries mass will not be larger; however you're right in saying this does constitutes a problem, not so much to earth (the large chunks you can detect, smaller will burn in atmosphere), as to spaceships and sattelites.
note, also, the original poster said such a feat is impossible in today's technology, and my answer is this does not seem impossible, just very costly and undesirable; it should only be done if the asteroid is on a confirmed collision course with earth. In that case, several megaton sized explosions on earth and a serious future problem for spacecraft are a small cost compared with total-asteroid impact
The coming together of balls and stupidity.
best definition of a soldier i've ever seen.
how about a series of thermonuclear detonations ?
...
say radius ~ 1 KM => mass ~ 3*10^15 gr
v=30Km/sec = 3*10^6 cm/s => Energy ~ 3*10^28 ergs
1 Megaton TNT is 4.5* 10^ 22 ergs
and IIRC we have TN bombs of hundreds of megatons:
300 megaton ~ 10^25 ergs
so 3000 such bombs will do the trick
and this is a rough calculation, actually the asteroid will lose mass due to evaporation, so the number may be considerably lower.
why not giving them 6 months (probation?)?
...
why not give them several years in prison were they apparently belong ?
or, alternatively, they could allways finance the next mission to the moon to replace what they stole
this is what many people don't understand:
some of the strange priorities of universities stems from dedicated donations: the university must BY CONTRACT use the money from a specific donation in a specific way.
so, if someone decided to give a donation for such a specific project, it doesn't matter that the money would be 100X time more usefull in adding to the local library, since they can't use the money that way.
it's a pitty, because many times the sexy subjects are by far not the effective ones.
I just SEE an old guy with moist eyes.
but then, I'm telepathicly impaired, so what do I know.
the only out of this energy mess, besides a huge drop in human populatiom, is fusion
wrong.
as a student in plasma-physics I am all for fusion-research, but I very much doubt we'll have commercially viable fusion reactors in less than
30 years. Actually a proof-of concept break-even machine has not been develloped yet (though the advances were enourmous). Fusion reactors are not fully a technology-problem yet, there is still much basic scientific research involved.
but we have an alternative: SPS (Solar Power Satelites) : they can utilize conventional turbine-generator techniques at a large scale, and beam the power as microwaves down to earth.
there is no new, yet to be researched science in SPS (as opposed to fusion), the only problem is financial: get the investment to start mining the asteroid belt.
What else is there this old that still looks as good......?
Volkswagen Beatle.
when a car is still manufactured ~60 years (in latin america) after design.
when a car that was manufactured before I was born is still operative sufficiently for my day-to-day needs, and not as a collector's item.
than that is, in my biassed opinion, good engineering design == real beauty.
A good example of this is that NASA still uses 8086 processors: You know exactly how they work.
I thought this was more due to radiation robustness , than due to plain conservatism (which I agree is an asset in critical-system engineering)
am I wrong ?
for a rocket, every component has to work right, every combination of components has to work right, for every step in the launch sequence, for every pressure, temperature, vibration-mode
and those are the things a layman (me) thought of just at first glance, I'm sure there are more.
since there are a lot of components, there are even far more combinations and configurations to test. This SHOULD be done by rocket scientists and technitians, not by (even knowledgeable) amatures, and should be done many times over for each configuration, to increase the level of statistical confidence (remember sigma ~ 1/sqrt(N) )
in short QA of critical systems is a very large-scale labor-intensive problem, I don't believe one man can do this alone reasonably well, and even should he by some miracle succeed, I will NOT take the next rocket up.
You do realize, right, that this is exactly the FreeBSD release method?
wrong, I actually don't know the BSD dev-model.
(3) is STABLE, (2) is RELEASE, and (1) is CURRENT.
but if I understand correctly the meaning of RELEASE label, it is for testing purposes only, while I suggest 2 branches for both dev and QA, only the scales differ.
then when you approach a "freeze" (updating 1->2 or 2->3 ) you will need a short-lived release-candidate branch for each.
I know all the arguments about how it is a "stable" series and all
but you want to discard stability of a STABLE branch for features - not a great deal for users who wish to actually use the system.
- but some people want new features, and 2.5 is not an option, thanks to IDE being owned by Martin
have you considered that IDE instabilities are in 2.5 because this is where new features and engineering reforms should be done, regardless of who is the maintainer ?
my belief: there should be a split to 3 branches:
1) long-term dev-branch: this branch is where large-scale (>months) changes are made and tested.
2) medium and short-term dev-branch: this branch is what you're looking for, where features and fixes which take months or less are made and tested, really tested, not like the 2.4 VM fiascos, before becoming stable.
3) stable branch: this branch changes once a year or less, except for very minor bug/security fixes.
changes will NOT be imported directly from 1->3, only 1->2 , 2->1 and 2->3 .
this will give you both stability for those who need it, long-term dev and testing environemnt for the systemic reformers, and short-term devellopment for the medium- to small-scale changes.
and before anyone of you jumps and shouts "but this is exactly the debian model of stable, testing, unstable branches" I say that both branch 1 AND 2 are dev. AND testing branches, the criterion sugested is the changes scale, not the targeted audience (though ususally decisions may be similar between models).
there is no silver bulochka