SpaceX is almost ready to fly people and to dock with the ISS, which is much farther than any other private organization has done. The Space Shuttle can't go to the moon, so the shuttle's replacement doesn't have to either -- it just has to be able to get people and cargo up into low-Earth orbit. Moon rockets and beyond come later.
JWST's optics and sensors have to be kept very cold, something that is difficult to do in LEO thanks to all of the Earth IR and albedo. Putting it at L2 means the Earth's disturbances will be in line with the Sun's, and they can use a single stationary shield to protect the optics and sensors.
But yes, you are right, it will be significantly more difficult (impossible with current technology) to service it.
L1, L2, and L3 are not stable (if you stick a rock there, it will fall away in "no time"). JWST is going to be placed at L2 (though it will move around a bit in a halo orbit). Only L4 and L5 are stable.
So, if someone gets a hold of one of your single-use passwords, then that's it, game over? That's pretty silly.... if anything, those are the passwords that are more likely to get hacked/found out/stolen/whatever.
For each 3rd-party application accessing your Google account, you set up a separate single-use password for (single-use here means one application, not one login attempt). Presumably these single-use passwords offer limited access to your account, in particular any security settings.
Likewise, I would like to see you strap pedals to a drive train underneath that solar car, and powering it to 88 km/h for a kilometre; I'll watch.
In the Autumn of 1985, at the International Human Powered Speed Championships, a fully-faired Moulton ridden by Jim Glover broke the 200 metres flying start speed record, at 50.21mph (80.79kph). Then on August 29th 1986, at the same event, he broke his own record at a speed of 51.29mph (82.54kph) which still stands today for the conventional riding position. [1].
It seems that if you design a bike completely around top speed, and if you are a professional-caliber cyclist in excellent competition health, you can beat 88 km/h for brief periods [2]. On the other hand, these are 200 m races lasting under 10 s, so they are a little more sprinty than the 1 km achieved by the car in question.
It's a hell of a lot more efficient than piston->electric->battery->motors. Also, if designed well, then if the turbines were running, they would power the electric motor demand directly, and using any excess power generation to top up the batteries.
Well, if you believe that planes fly through the air, then what is different about water? Air and water are both fluids, they just have different densities. Think of a submarine -- it has control surfaces just like an airplane.
The term "flight" is widely used in the space industry, regardless of how appropriate the original meaning was at describing the motion of spacecraft and satellites (recall that early rockets didn't even make it to orbit, but still passed the edge of "space").
Why does this need to be the case? Rolling resistance is a measure of the rolling friction between the tire and the road -- the more rolling friction, the faster the wheel will de-spin without applying power to it. While I'm not an expert in the area, it would seem to me that your stopping distance is governed more by the static friction between the tire and the road -- i.e. how much lateral force you can apply at the tire-road interface before the wheel overcomes static friction and starts sliding on the surface. Since kinetic friction is much lower than static friction, we always want our wheels to be rolling when we are stopping, hence the introduction of ABSs[1].
To me, the rolling resistance and stopping distance are not necessarily heavily coupled. Perhaps the geometry and physical limitations of tires makes them so, but that is a different discussion.
-Aikon
[1] Note that ABSs performance depends on the surface -- on flat, dry pavement (what most cars see most of the time), ABSs decrease the stopping distance. On grass-covered dirt, locking the tires decreases stopping distance because they pile dirt up in front of the wheels.
ummm cable and telephone lines are pretty much in the definition of Natural Monopoly.
Bell and Rogers would have a "duopoly" regardless of what the government did. All the government really did was to force them to provide services in rural areas so Canada doesn't have shitty rural internet service like the US does.
It doesn't have to be like that, though; the municipality could own the phone and cable lines as they do the electricity and water. You then purchase service from whichever provider you choose, all of whom can compete on a fair basis.
The governments subsidized the initial build-out, which is great, but now that the infrastructure is there, it's time to revisit the ownership rights. Telcos in Canada have absconded with the continual government subsidies to fill to boost their bottom line, while letting their technology languish in the early 1990s. If you had real competition, then ISPs would be striving to provide the best possible service they can to entice more customers to join them.
I am so sick of hearing this typical comment from lazy people who are more than happy to spread their asscheeks and let Rogers and Bell frack them up the butt into the depths of their bowels instead of even considering an alternative. Does Bell get all the money you would pay for an account from a reseller? NO! So I would think that everyone that hates Bell or Rogers would be more than happy to drop them and switch to an ISP where a good chunk of your monthly bill goes into non-big-business pockets. But alas, it's always easier to sit, do nothing, and complain instead of taking action.
Sure, there is alternative action. For example, TekSavvy has finally struck a deal with Rogers to provide cable internet service in some regions in Ontario, in particular the GTA. Their deals are great and much more cost-effective than Rogers, however they require significant up-front costs -- installation (they need to hire a Rogers guy to come flip an electronic switch) and hardware (you need to own your own cable modem). For me, TekSavvy becomes a better deal at ~7 months, and I would be more than happy to switch
Unfortunately, their deal with Rogers is not a contract, and Rogers is free to change the terms of the wholeseller agreement whenever they like. If two months from now Rogers downranks TekSavvy cable into oblivion, then I am left out to rot in the Sun.
The fact that Bell and Rogers (or whoever your local telephone and cable providers are) have an artificial duopoly on the last mile basically screws everyone over and completely stifles competition.
Take another look at the two pictures in the article; looks pretty symmetrical to me. Both wingtips are raked, and also point down with negative dihedral.
[1] For the physically inclined, there's a more subtle error, too. The impulse supplied by a photon is related to its momentum, which is a function of wavelength. So, unless something weird's happening in the sail, blue photons supply a larger impulse than red photons.
This is, in fact, the case -- not all photons exert the same impulse on the sail. However, there are other factors as well -- for one, the sail reflectivity is not uniform across all wavelengths, and so will have different absorption rates throughout the spectrum; for another, the solar spectrum is not uniform either, and emits many more photons at certain wavelengths than at others. This means that, on average, you may get more thrust out of a lower-energy portion of the spectrum than from a higher energy portion.
I think the OP was proposing something along the lines of a hinged joint, such that as the pressure underneath the cover increased, it would pivot the cover about this hinge, somewhat like a butterfly valve. An interesting proposition, though I'm not certain how you would stop it from flipping over if a heavy enough vehicle drove over it.
Yes, you are right -- micrometeoroid impacts are definitely an issue that you have to deal with when you are using thin-membrane materials in space. Hopefully the engineers will design features called "rip stops" (among other names) into the sail to prevent tears from spreading through the sail. These are usually accomplished by putting a grid of perforations throughout the sail -- when a tear encounters one, the circular shape spreads the tensile stresses across the adjacent material, reducing the likelihood that the tear will propagate. This way a micrometeoroid impact won't ruin your entire sail, just the local grid element.
There are probably other methods of implementing rip stops, but I haven't read any significant literature on them. Anything bigger than a micrometeoroid, and you have bigger problems -- but in this case, a traditional satellite would have just as big a problem.
Possibly; I was going off a meme at our lab that originates from one person saying something negative, and the other responding "you mispronounced 'awesome'."
Ha! Well played, sir. Actually I was all proud of myself when I came up with it, but apparently it was far more obvious than I thought as 'celliquette' seems to already be in use out there =/
Slashdot Mirror
The SSMEs (Space Shuttle Main Engines), the three things on the back of the orbiter itself, are free if you pay for shipping.
Aikon-
SpaceX is almost ready to fly people and to dock with the ISS, which is much farther than any other private organization has done. The Space Shuttle can't go to the moon, so the shuttle's replacement doesn't have to either -- it just has to be able to get people and cargo up into low-Earth orbit. Moon rockets and beyond come later.
Aikon-
JWST's optics and sensors have to be kept very cold, something that is difficult to do in LEO thanks to all of the Earth IR and albedo. Putting it at L2 means the Earth's disturbances will be in line with the Sun's, and they can use a single stationary shield to protect the optics and sensors.
But yes, you are right, it will be significantly more difficult (impossible with current technology) to service it.
Aikon-
L1, L2, and L3 are not stable (if you stick a rock there, it will fall away in "no time"). JWST is going to be placed at L2 (though it will move around a bit in a halo orbit). Only L4 and L5 are stable.
Aikon-
So, if someone gets a hold of one of your single-use passwords, then that's it, game over? That's pretty silly.... if anything, those are the passwords that are more likely to get hacked/found out/stolen/whatever.
Aikon-
For each 3rd-party application accessing your Google account, you set up a separate single-use password for (single-use here means one application, not one login attempt). Presumably these single-use passwords offer limited access to your account, in particular any security settings.
Aikon- (but this time, I am logged in)
Likewise, I would like to see you strap pedals to a drive train underneath that solar car, and powering it to 88 km/h for a kilometre; I'll watch.
It seems that if you design a bike completely around top speed, and if you are a professional-caliber cyclist in excellent competition health, you can beat 88 km/h for brief periods [2]. On the other hand, these are 200 m races lasting under 10 s, so they are a little more sprinty than the 1 km achieved by the car in question.
Aikon-
It's a hell of a lot more efficient than piston->electric->battery->motors. Also, if designed well, then if the turbines were running, they would power the electric motor demand directly, and using any excess power generation to top up the batteries.
Aikon-
Well, if you believe that planes fly through the air, then what is different about water? Air and water are both fluids, they just have different densities. Think of a submarine -- it has control surfaces just like an airplane.
The term "flight" is widely used in the space industry, regardless of how appropriate the original meaning was at describing the motion of spacecraft and satellites (recall that early rockets didn't even make it to orbit, but still passed the edge of "space").
Aikon-
I agree, maybe they should make like a tree and get the fcuk out of here ;)
Aikon-
Bah, forgot my <p>s.. sorry about that!
Aikon-
Why does this need to be the case? Rolling resistance is a measure of the rolling friction between the tire and the road -- the more rolling friction, the faster the wheel will de-spin without applying power to it. While I'm not an expert in the area, it would seem to me that your stopping distance is governed more by the static friction between the tire and the road -- i.e. how much lateral force you can apply at the tire-road interface before the wheel overcomes static friction and starts sliding on the surface. Since kinetic friction is much lower than static friction, we always want our wheels to be rolling when we are stopping, hence the introduction of ABSs[1]. To me, the rolling resistance and stopping distance are not necessarily heavily coupled. Perhaps the geometry and physical limitations of tires makes them so, but that is a different discussion. -Aikon [1] Note that ABSs performance depends on the surface -- on flat, dry pavement (what most cars see most of the time), ABSs decrease the stopping distance. On grass-covered dirt, locking the tires decreases stopping distance because they pile dirt up in front of the wheels.
Except that kinetic friction is different from static friction, both of which are different again from rolling friction.
ummm cable and telephone lines are pretty much in the definition of Natural Monopoly.
Bell and Rogers would have a "duopoly" regardless of what the government did. All the government really did was to force them to provide services in rural areas so Canada doesn't have shitty rural internet service like the US does.
It doesn't have to be like that, though; the municipality could own the phone and cable lines as they do the electricity and water. You then purchase service from whichever provider you choose, all of whom can compete on a fair basis.
The governments subsidized the initial build-out, which is great, but now that the infrastructure is there, it's time to revisit the ownership rights. Telcos in Canada have absconded with the continual government subsidies to fill to boost their bottom line, while letting their technology languish in the early 1990s. If you had real competition, then ISPs would be striving to provide the best possible service they can to entice more customers to join them.
I am so sick of hearing this typical comment from lazy people who are more than happy to spread their asscheeks and let Rogers and Bell frack them up the butt into the depths of their bowels instead of even considering an alternative. Does Bell get all the money you would pay for an account from a reseller? NO! So I would think that everyone that hates Bell or Rogers would be more than happy to drop them and switch to an ISP where a good chunk of your monthly bill goes into non-big-business pockets. But alas, it's always easier to sit, do nothing, and complain instead of taking action.
Sure, there is alternative action. For example, TekSavvy has finally struck a deal with Rogers to provide cable internet service in some regions in Ontario, in particular the GTA. Their deals are great and much more cost-effective than Rogers, however they require significant up-front costs -- installation (they need to hire a Rogers guy to come flip an electronic switch) and hardware (you need to own your own cable modem). For me, TekSavvy becomes a better deal at ~7 months, and I would be more than happy to switch
Unfortunately, their deal with Rogers is not a contract, and Rogers is free to change the terms of the wholeseller agreement whenever they like. If two months from now Rogers downranks TekSavvy cable into oblivion, then I am left out to rot in the Sun.
The fact that Bell and Rogers (or whoever your local telephone and cable providers are) have an artificial duopoly on the last mile basically screws everyone over and completely stifles competition.
Aikon-
Take another look at the two pictures in the article; looks pretty symmetrical to me. Both wingtips are raked, and also point down with negative dihedral.
Aikon-
[1] For the physically inclined, there's a more subtle error, too. The impulse supplied by a photon is related to its momentum, which is a function of wavelength. So, unless something weird's happening in the sail, blue photons supply a larger impulse than red photons.
This is, in fact, the case -- not all photons exert the same impulse on the sail. However, there are other factors as well -- for one, the sail reflectivity is not uniform across all wavelengths, and so will have different absorption rates throughout the spectrum; for another, the solar spectrum is not uniform either, and emits many more photons at certain wavelengths than at others. This means that, on average, you may get more thrust out of a lower-energy portion of the spectrum than from a higher energy portion.
Aikon-
I think the OP was proposing something along the lines of a hinged joint, such that as the pressure underneath the cover increased, it would pivot the cover about this hinge, somewhat like a butterfly valve. An interesting proposition, though I'm not certain how you would stop it from flipping over if a heavy enough vehicle drove over it.
Aikon-
I think you'll find that [the Universe/saying dumb things] pretty much covers [everything/everyone]
Shutup woman, get on my horse.
Yes, you are right -- micrometeoroid impacts are definitely an issue that you have to deal with when you are using thin-membrane materials in space. Hopefully the engineers will design features called "rip stops" (among other names) into the sail to prevent tears from spreading through the sail. These are usually accomplished by putting a grid of perforations throughout the sail -- when a tear encounters one, the circular shape spreads the tensile stresses across the adjacent material, reducing the likelihood that the tear will propagate. This way a micrometeoroid impact won't ruin your entire sail, just the local grid element.
There are probably other methods of implementing rip stops, but I haven't read any significant literature on them. Anything bigger than a micrometeoroid, and you have bigger problems -- but in this case, a traditional satellite would have just as big a problem.
Aikon-
Possibly; I was going off a meme at our lab that originates from one person saying something negative, and the other responding "you mispronounced 'awesome'."
Aikon-
You mispronounced "so unused that it took 17 years to find."
I don't know why this has not yet been linked, but... obligatory XKCD reference
Aikon-
In your case, 'cell-ibacy' would be preferable.
Ha! Well played, sir. Actually I was all proud of myself when I came up with it, but apparently it was far more obvious than I thought as 'celliquette' seems to already be in use out there =/
Aikon-
Can we please call it "celliquette"? ohplz ohplz ohplz!
Aikon-