Ugh. If it's one thing I can't stand about slashdot is that all you people are CS majors or some such... Why I bother at all boggles the mind!
Okay, so here's the WHY of it. Asteroid composition is a very interesting subject because it seriously affects whatever technique you decide to use to divert a threatening asteroid. What you are looking for when studying asteroids is their porosity. Asteroids are not like they are portrayed on TV or in the movies, i.e. they are not solid chunks of rock. Instead, they can range from solid pieces of stainless steel (frigthening!) to loose aggregations of rubble (flying gravel piles) which are very porous. Porous materials are very good at absorbing energy and hence are much more difficult to deflect.
So, if one were to use a nuke on an asteroid that was porous, it would do a lot less to the porous asteroid than one that was solid through and through. So the purpose of these missions would be to scout out and start to get a better idea of what the distirbution (statistically speaking) of the porosity of the asteroids that are floating around out there. Their idea is to do this cheaply with ion propulsion. If you've got a lot of time to spend, ion propulsion is ideal to get around the inner solar system without spending a lot of mass on fuel.
If you have any more questions, I suggest you look at some papers by Ahrens or Holsapple. Also check out http://neo.jpl.nasa.gov.
At my CS department (University of Washington) we had a similar program running. As it turned out, about 10% of the class was cheating. Normally, the faculty can't do anything about cheaters because it takes up so much time cutting through the red tape (that, and the student union is really strong). But for some reason my class had so many cheaters that they decided to actually go after these guys.
The class had a about 200 people or so... 20 or so cheaters. That's practically a whole section!
I always thought it'd be a fun idea to put full size pictures of known terrorists' faces on t-shirts to screw around with it. I could just see it now: SWAT team converging on terminal B-9 at Miami Airport, over the radio you hear,
"Osama's been spotted. Take him out, over."
"I guess he didn't stay in that cave very long, over."
He mentions the idea of a U-2 like plane, or high aspect-ration wing-design. Unfortunately, planes with this design have very poor performance with regards to turning, and they have a tendency to fail structurally quite easily. And as the guy pointed out, you're already moving pretty fast to generate the lift, so you already are not going to be able to turn very fast at all.
What he didn't point out are the compressibility effects when you're going that fast. Since the speed of sound on Mars is roughly that of Earth (a = sqrt(gamma * R * T)), you are going to get big `ol shockwaves, which with those high aspect ratio wings--they're going to cause a very large amount of drag at those high speeds. Which means you need a bigger engine, yadda yadda more weight, thus bigger wings.
And if you're going to do the stubby wing design, what's the point? It won't generate enough lift. You might as well strap rockets onto yourself to get off the ground.
I guess my point on this is that you should probably do away with this whole idea of winged flight on mars until we've terraformed it (ha!). My personal favorite is a big, fat, blimp. It's a bit more practical then any of those high speed deathtraps.
This is kind of a side blurb, but I thought it might add to the discussion. At my university, I had the good fortune (it was a requirement:) ) to take a basic programming class where we were taught C. We five homework assignments, each one getting progressively harder. Each assignment was logically a computer program, not yet compiled. All work was turned in electronically via the CS school's server.
Anyway, there is a search algorithm that scans the code you just turned in and looks to see if it is similar to any previous assignments turned in. It doesn't just scan variable names and function names, but it also scans the way your program is set up (logic trees?). If it finds a high probability match, it informs the professor.
Some people were really stupid and just copied their friend's homework line for line... some were more clever and changed the variable names. As it turned out, something like 10% of the class was cheating. They normally don't pursue cheaters--ie. the red tape is impossible to cut through to get someone punished, but in this case they did their damndest. This was last year's freshman/sophomore class...
-greesil
"When in danger or in doubt, run in circles scream and shout" -- Lazarus Long
The place sounds nify, but one has to wonder at the cost effectiveness of this place. I mean sure, the tests aren't subject to the vagaries of weather, but how much did it cost to build?
"Never freighten a little man, he'll kill you" -Lazarus Long
radioactive waste is not a problem if your are fusing helium-3 and deuterium.
It is a problem with deuterium-detuerium reactions, though, but no worries, there are oceans of helium-3 in Jupiter... we just gotta extract it.
Also, fusion will be MUCH cheaper than gasoline. Consider the fact that the fuel supply for fossil fuels is limited, wheras deuterium is found EVERYWHERE. We have oceans of it here... It is a very good long term solution for any technological civilization, just in terms of fuel supply. Burning old dinosaur bones will only last so long.
I think it is the latest issue of SciAm that mentions something about extracting stem cell tissue from cadavers, which would finally get them darned yappity ethics people to cram it.
Meanwhile, back at the bat cave... er... the whitehouse, El Shrubo is will decide if the federal government will fund this sort of thing.
"I'd rather have a bottle in front of me than a frontal labotomy --
If you live in Seattle, where there is ALWAYS congestion, and there are really only 1 route to go from point alpha to point beta, more data isn't going to help. However, maybe we could make a device that would track where the department of transportaiton officals were at any given time, so we could always find them and throw eggs, rotten tomatos, etc. at them to make them build more roads!
"Money is truthful. If a man speaks of his honor, make him pay cash." --Lazarus Long
So far, this is all theoretical. I propose that we experimentally verify magnetic coupling with space time curvature (ie. gravity, according to Einstein)
In order to do this, one would need a large chunk of mass, and a pretty powerful magnetic field. So, you float out a detection platform in earth orbit, but across the solar system, so when you send a laser beam from earth it gets very close to the sun before going to the detector. Then, closer in (like mercury orbit) you have a big solar array and torus filled with supercooled liquid helium to produce a large magnetic field. Then spin the sucker (or find a convenient way to turn it on and off) and see how much you play with the beam. Voila, experimentally verifiable proof.
Of course, you'd have to deal with the sun's magnetosphere, any gas jets that get in the way, etc. Boy, getting data might be a mess. But, at least you'd get an idea of how much magnetic field it'd take to uncrinkle space, so if you wanted to reduce the gravity in a region
I gotta take more physics classes... E & M stress tensors.... yargh... Pretty cool stuff, though.
I think it was Tacitus who once said something to the affect of, "The empire was the most corrupt when the laws were most prolifigate." He was talking about the Roman Empire, circa 50ad, if you didn't know who he is.
The trouble is in this situation is what happens when corporations start doing some of the things that the government has traditionally done, ie. like speeding tickets? Do you regulate it such that the government has the sole power to enforce speeding? Essentially what the corporation has done is that it has become a government unto itself, with bureaucracies, evil dictators, etc... Generally with no constitution, charter, etc. And what happens when the government exists solely to make a profit? Ouch, it's illegal to pee now, and you gotta pay a fine every time you do it! Good thing there's competition...
No no no, you got it all wrong. The dust wouldn't move it off course, but it would distort the signal we are getting from the probe, hence the index of refraction.
And yes, I know some basic physics cause I'm studying to be a rocket scientist right now!
Solar wind could theoretically blow it off course, but you'd really need a big sail (like a light sail or similar device never before deployed by us humans) to have a noticeable effect.
I don't think the likely explanation has to do with exotic physics at all. It is true that we've never sent anything out of the solar system before, and hence this is uncharted territory...
Newtonian gravity seems to work pretty well on the local level (never mind this inflationary universe stuff, that doesn't really affect us in the Milky Way), so I don't think it's that.
My opinion is this: It is either that the NASA people didn't take into account the distortion effect (gravitational lensing or what have you) of the sun's own gravity, or...
There's lots of stuff floating around in the ecliptic of the solar system--dust, planets, but lots of dust. Wouldn't that give the solar system a different index of refraction than perhaps interstellar space? There's not much dust per unit volume, but there's a lot of distance between here and the probe... Anyone in agreement here?
It could also be that the Sun's own gravitational field is bending the light enough so that the NASA folk report an error of the actual trajectory that they see. Remember, Earth is pretty deep inside the gravity well of the sun.
Also, notice that since the Earth orbits Sol, and that the probe is in the plane of the ecliptic, the sun will swing by and block out the probe signal from time to time, also... it will distort the crap out of the observed constellations and hence, maybe cause an error or two in calculations.
This is all null and void, of course, if the sun is "behind" us in regards to the probe. Can anyone find this out?
Me thinks that the NASA folk probably already checked this... they're a smart bunch.
Slashdot Mirror
Ugh. If it's one thing I can't stand about slashdot is that all you people are CS majors or some such... Why I bother at all boggles the mind!
Okay, so here's the WHY of it. Asteroid composition is a very interesting subject because it seriously affects whatever technique you decide to use to divert a threatening asteroid. What you are looking for when studying asteroids is their porosity. Asteroids are not like they are portrayed on TV or in the movies, i.e. they are not solid chunks of rock. Instead, they can range from solid pieces of stainless steel (frigthening!) to loose aggregations of rubble (flying gravel piles) which are very porous. Porous materials are very good at absorbing energy and hence are much more difficult to deflect.
So, if one were to use a nuke on an asteroid that was porous, it would do a lot less to the porous asteroid than one that was solid through and through. So the purpose of these missions would be to scout out and start to get a better idea of what the distirbution (statistically speaking) of the porosity of the asteroids that are floating around out there. Their idea is to do this cheaply with ion propulsion. If you've got a lot of time to spend, ion propulsion is ideal to get around the inner solar system without spending a lot of mass on fuel.
If you have any more questions, I suggest you look at some papers by Ahrens or Holsapple. Also check out http://neo.jpl.nasa.gov.
-banjo
At my CS department (University of Washington) we had a similar program running. As it turned out, about 10% of the class was cheating. Normally, the faculty can't do anything about cheaters because it takes up so much time cutting through the red tape (that, and the student union is really strong). But for some reason my class had so many cheaters that they decided to actually go after these guys.
The class had a about 200 people or so... 20 or so cheaters. That's practically a whole section!
-me
"Osama's been spotted. Take him out, over."
"I guess he didn't stay in that cave very long, over."
-G
He mentions the idea of a U-2 like plane, or high aspect-ration wing-design. Unfortunately, planes with this design have very poor performance with regards to turning, and they have a tendency to fail structurally quite easily. And as the guy pointed out, you're already moving pretty fast to generate the lift, so you already are not going to be able to turn very fast at all.
What he didn't point out are the compressibility effects when you're going that fast. Since the speed of sound on Mars is roughly that of Earth (a = sqrt(gamma * R * T)), you are going to get big `ol shockwaves, which with those high aspect ratio wings--they're going to cause a very large amount of drag at those high speeds. Which means you need a bigger engine, yadda yadda more weight, thus bigger wings.
And if you're going to do the stubby wing design, what's the point? It won't generate enough lift. You might as well strap rockets onto yourself to get off the ground.
I guess my point on this is that you should probably do away with this whole idea of winged flight on mars until we've terraformed it (ha!). My personal favorite is a big, fat, blimp. It's a bit more practical then any of those high speed deathtraps.
-Rub a dub dub, thanks for the grub, yay god!
This is kind of a side blurb, but I thought it might add to the discussion. At my university, I had the good fortune (it was a requirement :) ) to take a basic programming class where we were taught C. We five homework assignments, each one getting progressively harder. Each assignment was logically a computer program, not yet compiled. All work was turned in electronically via the CS school's server.
Anyway, there is a search algorithm that scans the code you just turned in and looks to see if it is similar to any previous assignments turned in. It doesn't just scan variable names and function names, but it also scans the way your program is set up (logic trees?). If it finds a high probability match, it informs the professor.
Some people were really stupid and just copied their friend's homework line for line... some were more clever and changed the variable names. As it turned out, something like 10% of the class was cheating. They normally don't pursue cheaters--ie. the red tape is impossible to cut through to get someone punished, but in this case they did their damndest. This was last year's freshman/sophomore class...
-greesil
"When in danger or in doubt, run in circles scream and shout" -- Lazarus Long
The place sounds nify, but one has to wonder at the cost effectiveness of this place. I mean sure, the tests aren't subject to the vagaries of weather, but how much did it cost to build?
"Never freighten a little man, he'll kill you" -Lazarus Long
It is a problem with deuterium-detuerium reactions, though, but no worries, there are oceans of helium-3 in Jupiter... we just gotta extract it.
Also, fusion will be MUCH cheaper than gasoline. Consider the fact that the fuel supply for fossil fuels is limited, wheras deuterium is found EVERYWHERE. We have oceans of it here... It is a very good long term solution for any technological civilization, just in terms of fuel supply. Burning old dinosaur bones will only last so long.
Meanwhile, back at the bat cave... er... the whitehouse, El Shrubo is will decide if the federal government will fund this sort of thing.
"I'd rather have a bottle in front of me than a frontal labotomy --
Big deal.
If you live in Seattle, where there is ALWAYS congestion, and there are really only 1 route to go from point alpha to point beta, more data isn't going to help. However, maybe we could make a device that would track where the department of transportaiton officals were at any given time, so we could always find them and throw eggs, rotten tomatos, etc. at them to make them build more roads!
"Money is truthful. If a man speaks of his honor, make him pay cash." --Lazarus LongSo far, this is all theoretical. I propose that we experimentally verify magnetic coupling with space time curvature (ie. gravity, according to Einstein)
In order to do this, one would need a large chunk of mass, and a pretty powerful magnetic field. So, you float out a detection platform in earth orbit, but across the solar system, so when you send a laser beam from earth it gets very close to the sun before going to the detector. Then, closer in (like mercury orbit) you have a big solar array and torus filled with supercooled liquid helium to produce a large magnetic field. Then spin the sucker (or find a convenient way to turn it on and off) and see how much you play with the beam. Voila, experimentally verifiable proof.
Of course, you'd have to deal with the sun's magnetosphere, any gas jets that get in the way, etc. Boy, getting data might be a mess. But, at least you'd get an idea of how much magnetic field it'd take to uncrinkle space, so if you wanted to reduce the gravity in a region
I gotta take more physics classes... E & M stress tensors.... yargh... Pretty cool stuff, though.Yeah, what you say is true (in my humble opinion), but how do you explain the losses in Kangaroo Land coinciding exaclty with the arrival of humans?
I think it was Tacitus who once said something to the affect of, "The empire was the most corrupt when the laws were most prolifigate." He was talking about the Roman Empire, circa 50ad, if you didn't know who he is.
The trouble is in this situation is what happens when corporations start doing some of the things that the government has traditionally done, ie. like speeding tickets? Do you regulate it such that the government has the sole power to enforce speeding? Essentially what the corporation has done is that it has become a government unto itself, with bureaucracies, evil dictators, etc... Generally with no constitution, charter, etc. And what happens when the government exists solely to make a profit? Ouch, it's illegal to pee now, and you gotta pay a fine every time you do it! Good thing there's competition...
Aaaah, sweet capitalism.
No no no, you got it all wrong. The dust wouldn't move it off course, but it would distort the signal we are getting from the probe, hence the index of refraction. And yes, I know some basic physics cause I'm studying to be a rocket scientist right now! Solar wind could theoretically blow it off course, but you'd really need a big sail (like a light sail or similar device never before deployed by us humans) to have a noticeable effect.
I don't think the likely explanation has to do with exotic physics at all. It is true that we've never sent anything out of the solar system before, and hence this is uncharted territory... Newtonian gravity seems to work pretty well on the local level (never mind this inflationary universe stuff, that doesn't really affect us in the Milky Way), so I don't think it's that. My opinion is this: It is either that the NASA people didn't take into account the distortion effect (gravitational lensing or what have you) of the sun's own gravity, or... There's lots of stuff floating around in the ecliptic of the solar system--dust, planets, but lots of dust. Wouldn't that give the solar system a different index of refraction than perhaps interstellar space? There's not much dust per unit volume, but there's a lot of distance between here and the probe... Anyone in agreement here?
It could also be that the Sun's own gravitational field is bending the light enough so that the NASA folk report an error of the actual trajectory that they see. Remember, Earth is pretty deep inside the gravity well of the sun. Also, notice that since the Earth orbits Sol, and that the probe is in the plane of the ecliptic, the sun will swing by and block out the probe signal from time to time, also... it will distort the crap out of the observed constellations and hence, maybe cause an error or two in calculations. This is all null and void, of course, if the sun is "behind" us in regards to the probe. Can anyone find this out? Me thinks that the NASA folk probably already checked this... they're a smart bunch.