It takes about 10kWh of energy per kg to reach earth orbit (36MJ), which according to my electric bill costs about $1.50. The fact that current rockets cost thousands of times this to get a kg of something into space means *we are doing it wrong*.
There are *lots* of ways to reduce the cost, mostly involving using something other than chemical rockets for part or all of the trip. My favorite is a "particle bed gas gun". This takes room temperature hydrogen gas, runs it through a bed of heated aluminum oxide particles (aka #40 sandpaper grit), then exhausting that hot hydrogen through a large pipe, where it pushes your rocket to around half of orbital speed.
The reason to use hot hydrogen is that has the highest speed of sound for a gas, and thus the highest muzzle velocity before becoming inefficient. The reason for the particle bed is you can heat it over a long time (hours) using anything, like an electric heating element. Then you dump the heat into the hydrogen in a fraction of a second due to the large surface area of the particles.
A conventional rocket is 14% hardware, 3% payload, and 83% fuel. Doing half the work with the gun changes the numbers to 20% hardware, 20% payload, and 60% fuel. You need more hardware cause its being fired out of a gun. But the payload is now 6x greater.
Yes, people can't be fired out of a gun, but lots of stuff can be. Food (frozen), water, more fuel, and structural materials.
Another good answer is a "partial space elevator". A full space elevator has its center of mass at GEO, so the orbital period matches the Earth's rotation and it appears to hang in one spot. Those are currently very hard to build with available materials. But one that is not as large, using existing materials, would have an orbital period somewhere between 90 minutes (LEO) and 24 hours (GEO). The bottom end would therefore have a speed somewhere between 7900m/s (LEO orbital speed) and stationary. So now a rocket, or whatever, only needs to match the speed of the bottom of the elevator.
Real building materials like carbon/epoxy used in modern airliners, can be used to make towers 60-100km tall. If your rocket *starts* from the top of such a tower, it gets to miss all the drag and almost all the gravity turn losses a rocket starting from the ground has. That's about another 10% shaved off the job of getting to orbit. And launching from a tower is compatible with people. (so is firing from a gun, but it has to be a fairly gentle gun, so you dont get that much speed from it, maybe 2000 m/s at best @ 9 g's)
If it is leaked from several different sources and posted on independent websites, it should be easy enough to compare. By different sources I mean a leak from an Australian trade representative, USA trade representative etc.
If you just have one leak from a single source, then you cannot be sure that the original leaker made it up on his own.
You would use the same solar panels they have there now, but since the Station is in the earth's shadow 40% of the time, they don't generate power currently during part of the orbit. And by bypassing the batteries on the truss, you also gain from not having the battery conversion losses, so its possible to get around a 2x total power increase.
@LehiNephi - The Space Station is a big enough target that atmospheric distortion is not a problem. At that altitude you would be able to see a target about 1.5m across without adaptive optics, and the station is a lot larger than that.
@TheKidWho - yes, a single ground station does not provide coverage of much of the Station's ground track. But remember that each of the 4 solar arrays on the station cost $300million, even a small increase in power would pay for a lot of overgrown searchlights. Because the target is so large, your optics on the ground does not have to be as good as a telescope, somewhat better than those big searchlights they use for store openings will work.
The space station is typically 1 arc minute across when seen from the ground, which is about the same resolution as the human eye, or about 1/30 the width of the moon, its a big target.
Its about as dangerous as the inside of a coal fired plant boiler - ie not a good place to stand, if they used a high intensity beam. They probably wont though. Although some solar cells on the ground receiving end can take 400 suns intensity, they require active cooling or they melt (very much the same as CPUs in computers, and roughly the same energy per area). If your cooling failed, you would damage your reciever, so it would be an expensive repair.
The point of solar from space is that you get around 5x as much sunlight to work with up there (less nighttime, clouds, and atmosphere absorption). So if the extra costs of putting it up there are less than 5x as high, you are ahead by putting it in space. If not, you are better off putting it on the ground.
For certain uses like the military, even an expensive, but *steerable* power source is a big win over using trucks carrying fuel.
And since power in space is currently a lot more valuble than on the ground, a first experiment should be to beam power *up*, for example to add extra power to the Space Station, or to test out that nifty VASIMR plasma thruster, they eat lots of power. Power on board the Space station runs $140/kWh, around 1000x what it sells for on the ground, so sending it *up* makes economic sense.
World energy use is increasing about 2% a year. Speed of a vehicle goes as the square root of the kinetic energy. Therefore if the speed of a vehicle depends on the energy you have to throw at the problem, you can expect your spaceships to get faster about 1% a year.
Therefore any trip over 100 years, you would expect a faster ship launched later to overtake you. So any spaceship heading for alpha Centauri (4.3 light years), you may as well wait till you have 4% of lightspeed ships or better.
There are two numbers which are not changing: the energy in chemical rocket fuel and the mass of the earth. Those two dictate that about 90% of a rocket's liftoff mass be fuel.
Airbreathing launch vehicles, by using oxygen from the atmosphere, get more energy per kg of fuel.
The Virgin Galactic launcher is a step in this direction, using the carrier plane with jet engines to get part of the way up.
The Ares is actually no improvement over the Shuttle, its the exact same set of rockets (Ammonium Perchlorate/Rubber/Aluminum solid booster, LOx/LH2 upper stage)
(and yes, I was a rocket scientist, with Boeing, in Huntsville AL for many years, but retired now)
It's called Opensim, virtual world regions hosted on people's own computers rather than Linden Lab (owners of Second Life) servers. Since the Second Life server software is not open source, people are having to recreate the functionality on their own, as an open source software project.
Read up on the "Hype Cycle" (The Gartner Group came up with that description). Most new technologies go through it. Some survive. The process is roughly, new idea comes out, someone implements it, the promoters and the media go crazy for a while hyping it. Lots of people try it, many find it *isnt* the best thing since sliced bread and give it up. Then it goes into hibernation for a while. Some technologies die at this point, either lack of interest, or something else takes over that space. The good technologies go on to version 2 and version 3, and sometimes people find good uses for it and build on that. So the general curve is first over-hype, then under-hype, while the actual uses are a more steady growth curve.
Virtual worlds like Second Life are not the answer to everything. If you want 3D without interaction, you have 3D video. If you want just interaction but don't need 3D, there's instant messaging, VOIP, and webcams. If you want *both* 3D and interaction, that's where virtual worlds have a space. Breaking that down further, if you don't want user-content, you end up with something like an MMO game - someone else makes the content, you enjoy it. If you *do* want user content, you end up with something like Second Life.
Besides the entertainment uses, the serious uses revolve around "cheap simulation and training". For example, the Red Cross is using Second Life to practice post-disaster setup. You can use the same people as you would in a real disaster, and simulate your refugee camp setup, or whatever to get some practice and work out the bugs. It's way cheaper to do that than bring out the real aid tents. It's not 100% replacement, any more than airplane flight simulators are 100% replacement for getting in the real airplane and flying it. But in the flight simulators you can practice losing an engine, which you don't *want* to do in real training.
Another good use is any time the users are widely dispersed and bringing them all to a training facility would be too expensive. An example is car repairs, where a 3D walkthrough for a rare repair would be handy, and the repair guys are scattered all over the world. Something like that would work better with 3D glasses and force-feedback gloves, but those are not commonly available yet, PCs with graphics cards are, so for now, use what you got.
Just before the announcement of listing fees, there were 1.15 million items listed on http://www.xstreetsl.com/ , their web commerce site. Many of them were just color variations of the same item, or free items. By not having a listing fee previously, people had no incentive to be efficient in what they put there, in fact they had incentive to spam the listings with as many items as possible to be seen (just like email spam occurs because sending emails is essentially free).
So this move will force people to be somewhat efficient in what they put there. Note that the fee is L$10 per month, which equates to about a postage stamp for a year's worth of listing. Big surprise that people whine about the changes in a social media space (not). They were whining before the changes that it was cluttered with too many listings.
For those who say it's not popular, they have 750,000 active accounts (people who log in more than once a month), which is probably more than the active accounts here at Slashdot. It does not appeal to everyone, but then *nothing* appeals to everyone. It does, however fit with some of the tropes at Slashdot, the people who like to make their own stuff, and mess around with open source. The viewer code for Second Life (the client software you run on your PC) has been open-sourced for a while now, and around 40% of players are using alternate viewers (especially the one that has enabled "breast physics" *heh*).
Disclosure: I'm a top 20 currency trader in SL and derive a moderate monthly income from that and other in-game activities. I'm also a developer for Blue Mars, a new virtual world that's in early beta (much better graphics, using the Cryengine2 graphics engine from the Crysis games), so I'm agnostic about virtual worlds if they are good ones.
2nd Amendment dude, and its a bit out of range for home ownership, but perhaps Jules Verne got it right, his gun was financed by the Baltimore Gun Club.
A BFG project promising to "fire your shit into space" with everyone kicking in a subscription might be enough to get a demo gun built.
We need to test some carbon fiber- wrapped frozen pumpkins for g-tolerance:-)
For the numbers I posted above, the gun force is 1.4 Mega-newtons (315,000 pounds). So a concrete backstop anchored to bedrock needs to be around 500 square inches in area, if we are generous about shock loads and safety factors. Probably need some of that elastomeric earthquake damper stuff between the foundation and barrel end to prevent cracking.
Why a gas gun and not a mag-lev or something like that? Well, foot per foot, a steel pipe is way cheaper than a set of coils, or a humongous power supply. We deliver oil and gas by pipeline for that reason.
Why not use the gun to get full orbital speed? Both the performance of the gun falls off exponentially as you get above Mach 1 of the working gas, and air drag goes as the square of the muzzle velocity.
How much do you lose going thru the atmosphere? Well drag = 0.5 * Cd * rho * A * v^2
Cd = drag coefficient of the projectile, assume 0.15 rho = air density, assume 0.75kg/m^3 at for a muzzle at 4000m elevation A = projectile area, for 30cm diameter its 0.07m^2 v = 5000m/s lets say
Then drag = ~100kN. With a 360kg projectile thats negative 276m/s. With a 30 degree elevation, distance thru the atmosphere is equivalent to 17km, so about 4 sec of drag loss, at an average of 4500m/s, so around 800-900m/s lost. Net velocity out of the atmosphere will then be 4100m/s. You need to add around 4km/s with the rocket onboard.
With internal barrel pressure of 200 atmospheres (3000 psi, or 20Mpa), projectile acceleration is just under 4000m/s^2 (400g) at first. Firing time in an ideal gun would be 1.25 sec, and barrel length would be a bit over 3km. Higher pressures would get you a shorter barrel.
With a good grade of steel for the barrel, say 60ksi safe working pressure (400Mpa), the wall thickness needs to be internal pressure/barrel strength = 20/400 times the diameter. With 30cm barrel, that comes to 1.5cm wall thickness, or a bit over 1/2 inch. This is quite easy to find commercially.
This is about the smallest gun that would be commercially useful (~100kg net payload). Bigger ones would be more efficient, but more expensive to build.
Something about halfway in scale between the SHARP gun (already done), and this would be a good intermediate step to prove the technology.
The prototype gun would then have the following parameters:
Muzzle velocity - 4 km/s Projectile mass - 40kg (about 8 standard pumpkins:-) Projectile/barrel diameter - 15cm Acceleration - 1000g peak Barrel length - around 1000m Working pressure - 23Mpa (3300psi) peak
The actual SHARP gun tests were into the side of a hill at Livermore Lab. You had the 50m barrel horizontal, then a 10m long block of concrete with a slightly more than 10cm hole down the middle for the 10cm projectile to fly through. That was to protect the gun from blast damage. The hill had a hole dug in it filled with plastic milk jugs filled with water as "shock absorber". Otherwise your hill would get demolished by repeated firings.
At low speed tests, you could recover parts of the projectile and the milk jugs. At high speeds, pretty much everything vaporized.
The concrete block with the gun behind it was about 50 or 100m from the hill. If fired for best range, ie around 45 degree elevation, the projectile would land in NEVADA from Livermore, CA
You cannot fire such a gun in machine gun style, the barrel will overheat. As it is, we had a replaceable liner that could take high temperature, and the main barrel structure was based on high pressure natural gas lines (went so far as to get quotes from the people who make that stuff).
You can get a bit more efficiency by having a cover over the muzzle, keeping air out, and pumping the barrel down to some fraction of air pressure. You leave a little air in the barrel, which piles up in front of the projectile, and ensures the cover pops open just before the projectile leaves.
Such a gun is *LOUD* I remember figuring out that all living things within 50m of the muzzle get killed, by the combination of shock wave, followed by hot hydrogen that was just behind the projectile burning with the air when it reaches it. I forget what the hearing protection radius was, I think it was on the order of 1 km or so, and the sonic boom as it travels upwards would be audible for quite a ways.
On Hawaii, you would be firing over the top of an active volcano, so other than making ripples in the lava pool from the shock blast, its not too much of an issue. One thing we did not analyze in detail is what happens to all the delicate astronomical observatories on the *other* peak on the island.
Surprisingly, frozen food survives 1000g just fine, as does properly made electronics, fuel, breathing gases, and structural items, so a very large fraction of what you want in space, besides people, can be fired out of a gun.
One cool use for such a gun is launching spools of space elevator cable. A partially built space elevator lowers the speed required to get to orbit via a vehicle. The landing platform at the bottom end moves slower as the elevator cable gets longer. So the gun can indirectly help with the people launching job.
Our projectile was re-useable liquid fueled. And the mission was to feed a fuel depot for geosynchronus satellites. 3/4 of the mass of comsats in low orbit is fuel to get them to GEO, and stationkeeping for 15 years. The projectile was very simple, pressure fed liquid engine. It used part of the fuel to get itself into orbit, the remainder is transferred to a fuel depot.
The projectile uses GPS nav borrowed from artillery shells to get to the close vicinity of the depot, then the depot has the smarts to find and dock (that way the smarts occurs once, not on every projectile).
Once done, we deorbit and land anywhere, even on concrete. There is a couple of inches of ablative heat shield on the nose, backed up with 10cm of crushable honeycomb. A bit of the heat shield burns off going up, and more coming back. The honeycomb lowers the landing shock to under 1000g's. Since that's the g-force being fired up in the first place, the projectile can already stand that landing.
Our design projectile was about 360kg loaded, if I recall, and about 100kg or less empty, Ill have to dig out the documents to be sure.
We factored in a 4% loss rate on projectiles after you had experience (40% on the first 10, declining as you gain experience).
Costs worked out to $300/kg ongoing if I remember.
Back when I was doing giant space gun work at Boeing:-). Feel free to ask questions. I'm not about to type in several volumes of technical data, but it's nice to see he's converged on the same muzzle velocity we came up with (5.7km/s).
Our desigh: particle-bed heater with Aluminum-oxide heat storage (it's actually #20 sandpaper grit). It's much easier to store hydrogen at room temperature, then heat it just before it hits the barrel. Using small particles, you get lots of area for heat transfer. The particle bed gets warmed up with heaters of your choice over a period of hours, then you fire the gun and in a second or so transfer a good chunk of that heat to the hydrogen.
Why heat the hydrogen? The speed of sound of a gas depends on the molecular weight and temperature, and hot hydrogen works best. The efficiency of a gun drops dramatically as you reach the speed of sound of the working gas. Think of it this way, speed of sound is how fast pressure waves travel.
If the projectile outruns that speed, there is no way for the gas at the back end to send push to the projectile further up the barrel. It's a bit more complicated than that since you are constantly feeding gas from the back end, and the gas right near the projectile is moving almost as fast, so pressure waves can catch up, but on the whole as you get near Mach 1 of the gas, your ability to push drops way down.
Depending on size of the gun, and where you are launching to, the west slope of Hawaii and the Andes are good locations. The first has *long* even slopes, courtesy of lava flows. The second are shorter, steeper slopes, but somewhat higher altitude (less air to fly through), and closer to the equator.
Destroying a missile in boost phase has some options besides burning thru the missile. The nozzle is unlikely to be highly reflective, it is too necessary for it to be strong and hear resistant. The exhaust is also unlikely in the extreme to be reflective. Your laser only needs to deposit enough energy on one or the other to create a shock wave that will damage the nozzle, and you are done.
The nosecone is also not likely to be reflective, because it has to be strong and heat resistant, and flying through the air often generates fog streaks as water vapor gets compressed. Again, you don't have to burn through the wall of the missle, just deposit enough energy to make a shock wave that will damage something important.
Think of it this way: with a hand grenade, the chemical explosives contain the energy to go boom. With the airborne laser, the iodine-oxygen fuel for the laser contains the energy, and the laser is just how you deliver the energy to the near vicinity of the target. Whether heat to failure or shockwave to failure is easier, I will leave to the experts, but there's more than one damage mode to consider when imagining countermeasures
If you define nanotech as technology of scale closer to a nanometer than a micrometer, ie less than 30 nm, then we are one chip fabrication generation away from it at the moment.
As was pointed out above, the thickness of some semiconductor layers already is down in the couple of nm range, the 30nm I refer to is the length and width of features.
Look at the cover of Popular Science, October 1983. Note: I used to work with Dr. Dana Andrews, at Boeing, in the early 80's. We were working on such things back then. Dana was the consultant for the movie 2010. We had fun going to see the movie as a group, and making critiques:
"Hey, that's a subsonic wake, that's wrong"
Aerobraking is a subset of hypersonic aerodynamics. Inflatable things like Ballutes are zero lift pure drag devices. You can also control direction if you use a lifting body shape. if you fly nozzle-first and shoot some cold fuel out, you can use it for a cool film and protect everything from melting.
I just checked, and TPB is still online. If the 4 defendants end up losing their appeal, but the site is still online, will the court case have made any difference?
If TPB site is actually shut down, and the torrent users just shift to the other torrent sites, will it have made any difference?
There's a fundamental problem for the type of people trying to stop file sharing. Their ability to target a particular sharing channel and use the legal system against it takes *years*. The internet and its users can respond and shift to something else much faster.
Slashdot Mirror
http://www.census.gov/main/www/popclock.html
A device like the Thing-o-matic is unlikely to work as a replicator by itself. It only makes one kind of part (plastic) and has no assembly ability.
What you would need is a machine that can produce a number of types of parts (metal, plastic, glass), and then assemble the parts.
Top machine: 2500 x 10^12 floating point ops x 64 bits = 160 x 10^15 bits per second
Human brain: 10^11 neurons x 10^4 synapses x 100 Hz firing rate = 100 x 10^15 bits per second.
I am not saying it will wake up tomorrow and launch Skynet, but until now inadequate hardware was a barrier to human-level AI.
And yes, I am quite aware that a synapse firing is not directly comparable to a binary bit. Call this a rough comparison.
It takes about 10kWh of energy per kg to reach earth orbit (36MJ), which according to my electric bill costs about $1.50. The fact that current rockets cost thousands of times this to get a kg of something into space means *we are doing it wrong*.
There are *lots* of ways to reduce the cost, mostly involving using something other than chemical rockets for part or all of the trip. My favorite is a "particle bed gas gun". This takes room temperature hydrogen gas, runs it through a bed of heated aluminum oxide particles (aka #40 sandpaper grit), then exhausting that hot hydrogen through a large pipe, where it pushes your rocket to around half of orbital speed.
The reason to use hot hydrogen is that has the highest speed of sound for a gas, and thus the highest muzzle velocity before becoming inefficient. The reason for the particle bed is you can heat it over a long time (hours) using anything, like an electric heating element. Then you dump the heat into the hydrogen in a fraction of a second due to the large surface area of the particles.
A conventional rocket is 14% hardware, 3% payload, and 83% fuel. Doing half the work with the gun changes the numbers to 20% hardware, 20% payload, and 60% fuel. You need more hardware cause its being fired out of a gun. But the payload is now 6x greater.
Yes, people can't be fired out of a gun, but lots of stuff can be. Food (frozen), water, more fuel, and structural materials.
Another good answer is a "partial space elevator". A full space elevator has its center of mass at GEO, so the orbital period matches the Earth's rotation and it appears to hang in one spot. Those are currently very hard to build with available materials. But one that is not as large, using existing materials, would have an orbital period somewhere between 90 minutes (LEO) and 24 hours (GEO). The bottom end would therefore have a speed somewhere between 7900m/s (LEO orbital speed) and stationary. So now a rocket, or whatever, only needs to match the speed of the bottom of the elevator.
Real building materials like carbon/epoxy used in modern airliners, can be used to make towers 60-100km tall. If your rocket *starts* from the top of such a tower, it gets to miss all the drag and almost all the gravity turn losses a rocket starting from the ground has. That's about another 10% shaved off the job of getting to orbit. And launching from a tower is compatible with people. (so is firing from a gun, but it has to be a fairly gentle gun, so you dont get that much speed from it, maybe 2000 m/s at best @ 9 g's)
If it is leaked from several different sources and posted on independent websites, it should be easy enough to compare. By different sources I mean a leak from an Australian trade representative, USA trade representative etc.
If you just have one leak from a single source, then you cannot be sure that the original leaker made it up on his own.
You would use the same solar panels they have there now, but since the Station is in the earth's shadow 40% of the time, they don't generate power currently during part of the orbit. And by bypassing the batteries on the truss, you also gain from not having the battery conversion losses, so its possible to get around a 2x total power increase.
@LehiNephi - The Space Station is a big enough target that atmospheric distortion is not a problem. At that altitude you would be able to see a target about 1.5m across without adaptive optics, and the station is a lot larger than that.
@TheKidWho - yes, a single ground station does not provide coverage of much of the Station's ground track. But remember that each of the 4 solar arrays on the station cost $300million, even a small increase in power would pay for a lot of overgrown searchlights. Because the target is so large, your optics on the ground does not have to be as good as a telescope, somewhat better than those big searchlights they use for store openings will work.
The space station is typically 1 arc minute across when seen from the ground, which is about the same resolution as the human eye, or about 1/30 the width of the moon, its a big target.
Its about as dangerous as the inside of a coal fired plant boiler - ie not a good place to stand, if they used a high intensity beam. They probably wont though. Although some solar cells on the ground receiving end can take 400 suns intensity, they require active cooling or they melt (very much the same as CPUs in computers, and roughly the same energy per area). If your cooling failed, you would damage your reciever, so it would be an expensive repair.
The point of solar from space is that you get around 5x as much sunlight to work with up there (less nighttime, clouds, and atmosphere absorption). So if the extra costs of putting it up there are less than 5x as high, you are ahead by putting it in space. If not, you are better off putting it on the ground.
For certain uses like the military, even an expensive, but *steerable* power source is a big win over using trucks carrying fuel.
And since power in space is currently a lot more valuble than on the ground, a first experiment should be to beam power *up*, for example to add extra power to the Space Station, or to test out that nifty VASIMR plasma thruster, they eat lots of power. Power on board the Space station runs $140/kWh, around 1000x what it sells for on the ground, so sending it *up* makes economic sense.
Dam :-)
World energy use is increasing about 2% a year. Speed of a vehicle goes as the square root of the kinetic energy. Therefore if the speed of a vehicle depends on the energy you have to throw at the problem, you can expect your spaceships to get faster about 1% a year.
Therefore any trip over 100 years, you would expect a faster ship launched later to overtake you. So any spaceship heading for alpha Centauri (4.3 light years), you may as well wait till you have 4% of lightspeed ships or better.
There are two numbers which are not changing: the energy in chemical rocket fuel and the mass of the earth. Those two dictate that about 90% of a rocket's liftoff mass be fuel.
Airbreathing launch vehicles, by using oxygen from the atmosphere, get more energy per kg of fuel.
The Virgin Galactic launcher is a step in this direction, using the carrier plane with jet engines to get part of the way up.
The Ares is actually no improvement over the Shuttle, its the exact same set of rockets (Ammonium Perchlorate/Rubber/Aluminum solid booster, LOx/LH2 upper stage)
(and yes, I was a rocket scientist, with Boeing, in Huntsville AL for many years, but retired now)
It's called Opensim, virtual world regions hosted on people's own computers rather than Linden Lab (owners of Second Life) servers. Since the Second Life server software is not open source, people are having to recreate the functionality on their own, as an open source software project.
Read up on the "Hype Cycle" (The Gartner Group came up with that description). Most new technologies go through it. Some survive. The process is roughly, new idea comes out, someone implements it, the promoters and the media go crazy for a while hyping it. Lots of people try it, many find it *isnt* the best thing since sliced bread and give it up. Then it goes into hibernation for a while. Some technologies die at this point, either lack of interest, or something else takes over that space. The good technologies go on to version 2 and version 3, and sometimes people find good uses for it and build on that. So the general curve is first over-hype, then under-hype, while the actual uses are a more steady growth curve.
Virtual worlds like Second Life are not the answer to everything. If you want 3D without interaction, you have 3D video. If you want just interaction but don't need 3D, there's instant messaging, VOIP, and webcams. If you want *both* 3D and interaction, that's where virtual worlds have a space. Breaking that down further, if you don't want user-content, you end up with something like an MMO game - someone else makes the content, you enjoy it. If you *do* want user content, you end up with something like Second Life.
Besides the entertainment uses, the serious uses revolve around "cheap simulation and training". For example, the Red Cross is using Second Life to practice post-disaster setup. You can use the same people as you would in a real disaster, and simulate your refugee camp setup, or whatever to get some practice and work out the bugs. It's way cheaper to do that than bring out the real aid tents. It's not 100% replacement, any more than airplane flight simulators are 100% replacement for getting in the real airplane and flying it. But in the flight simulators you can practice losing an engine, which you don't *want* to do in real training.
Another good use is any time the users are widely dispersed and bringing them all to a training facility would be too expensive. An example is car repairs, where a 3D walkthrough for a rare repair would be handy, and the repair guys are scattered all over the world. Something like that would work better with 3D glasses and force-feedback gloves, but those are not commonly available yet, PCs with graphics cards are, so for now, use what you got.
Just before the announcement of listing fees, there were 1.15 million items listed on http://www.xstreetsl.com/ , their web commerce site. Many of them were just color variations of the same item, or free items. By not having a listing fee previously, people had no incentive to be efficient in what they put there, in fact they had incentive to spam the listings with as many items as possible to be seen (just like email spam occurs because sending emails is essentially free).
So this move will force people to be somewhat efficient in what they put there. Note that the fee is L$10 per month, which equates to about a postage stamp for a year's worth of listing. Big surprise that people whine about the changes in a social media space (not). They were whining before the changes that it was cluttered with too many listings.
For those who say it's not popular, they have 750,000 active accounts (people who log in more than once a month), which is probably more than the active accounts here at Slashdot. It does not appeal to everyone, but then *nothing* appeals to everyone. It does, however fit with some of the tropes at Slashdot, the people who like to make their own stuff, and mess around with open source. The viewer code for Second Life (the client software you run on your PC) has been open-sourced for a while now, and around 40% of players are using alternate viewers (especially the one that has enabled "breast physics" *heh*).
Disclosure: I'm a top 20 currency trader in SL and derive a moderate monthly income from that and other in-game activities. I'm also a developer for Blue Mars, a new virtual world that's in early beta (much better graphics, using the Cryengine2 graphics engine from the Crysis games), so I'm agnostic about virtual worlds if they are good ones.
2nd Amendment dude, and its a bit out of range for home ownership, but perhaps Jules Verne got it right, his gun was financed by the Baltimore Gun Club.
A BFG project promising to "fire your shit into space" with everyone kicking in a subscription might be enough to get a demo gun built.
We need to test some carbon fiber- wrapped frozen pumpkins for g-tolerance :-)
For the numbers I posted above, the gun force is 1.4 Mega-newtons (315,000 pounds). So a concrete backstop anchored to bedrock needs to be around 500 square inches in area, if we are generous about shock loads and safety factors. Probably need some of that elastomeric earthquake damper stuff between the foundation and barrel end to prevent cracking.
Part 4:
Why a gas gun and not a mag-lev or something like that? Well, foot per foot, a steel pipe is way cheaper than a set of coils, or a humongous power supply. We deliver oil and gas by pipeline for that reason.
Why not use the gun to get full orbital speed? Both the performance of the gun falls off exponentially as you get above Mach 1 of the working gas, and air drag goes as the square of the muzzle velocity.
How much do you lose going thru the atmosphere? Well drag = 0.5 * Cd * rho * A * v^2
Cd = drag coefficient of the projectile, assume 0.15
rho = air density, assume 0.75kg/m^3 at for a muzzle at 4000m elevation
A = projectile area, for 30cm diameter its 0.07m^2
v = 5000m/s lets say
Then drag = ~100kN. With a 360kg projectile thats negative 276m/s. With a 30 degree elevation, distance thru the atmosphere is equivalent to 17km, so about 4 sec of drag loss, at an average of 4500m/s, so around 800-900m/s lost. Net velocity out of the atmosphere will then be 4100m/s. You need to add around 4km/s with the rocket onboard.
With internal barrel pressure of 200 atmospheres (3000 psi, or 20Mpa), projectile acceleration is just under 4000m/s^2 (400g) at first. Firing time in an ideal gun would be 1.25 sec, and barrel length would be a bit over 3km. Higher pressures would get you a shorter barrel.
With a good grade of steel for the barrel, say 60ksi safe working pressure (400Mpa), the wall thickness needs to be internal pressure/barrel strength = 20/400 times the diameter. With 30cm barrel, that comes to 1.5cm wall thickness, or a bit over 1/2 inch. This is quite easy to find commercially.
This is about the smallest gun that would be commercially useful (~100kg net payload). Bigger ones would be more efficient, but more expensive to build.
Something about halfway in scale between the SHARP gun (already done), and this would be a good intermediate step to prove the technology.
The prototype gun would then have the following parameters:
Muzzle velocity - 4 km/s :-)
Projectile mass - 40kg (about 8 standard pumpkins
Projectile/barrel diameter - 15cm
Acceleration - 1000g peak
Barrel length - around 1000m
Working pressure - 23Mpa (3300psi) peak
The actual SHARP gun tests were into the side of a hill at Livermore Lab. You had the 50m barrel horizontal, then a 10m long block of concrete with a slightly more than 10cm hole down the middle for the 10cm projectile to fly through. That was to protect the gun from blast damage. The hill had a hole dug in it filled with plastic milk jugs filled with water as "shock absorber". Otherwise your hill would get demolished by repeated firings.
At low speed tests, you could recover parts of the projectile and the milk jugs. At high speeds, pretty much everything vaporized.
The concrete block with the gun behind it was about 50 or 100m from the hill. If fired for best range, ie around 45 degree elevation, the projectile would land in NEVADA from Livermore, CA
Part 3:
You cannot fire such a gun in machine gun style, the barrel will overheat. As it is, we had a replaceable liner that could take high temperature, and the main barrel structure was based on high pressure natural gas lines (went so far as to get quotes from the people who make that stuff).
You can get a bit more efficiency by having a cover over the muzzle, keeping air out, and pumping the barrel down to some fraction of air pressure. You leave a little air in the barrel, which piles up in front of the projectile, and ensures the cover pops open just before the projectile leaves.
Such a gun is *LOUD* I remember figuring out that all living things within 50m of the muzzle get killed, by the combination of shock wave, followed by hot hydrogen that was just behind the projectile burning with the air when it reaches it. I forget what the hearing protection radius was, I think it was on the order of 1 km or so, and the sonic boom as it travels upwards would be audible for quite a ways.
On Hawaii, you would be firing over the top of an active volcano, so other than making ripples in the lava pool from the shock blast, its not too much of an issue. One thing we did not analyze in detail is what happens to all the delicate astronomical observatories on the *other* peak on the island.
Surprisingly, frozen food survives 1000g just fine, as does properly made electronics, fuel, breathing gases, and structural items, so a very large fraction of what you want in space, besides people, can be fired out of a gun.
One cool use for such a gun is launching spools of space elevator cable. A partially built space elevator lowers the speed required to get to orbit via a vehicle. The landing platform at the bottom end moves slower as the elevator cable gets longer. So the gun can indirectly help with the people launching job.
Part 2:
Our projectile was re-useable liquid fueled. And the mission was to feed a fuel depot for geosynchronus satellites. 3/4 of the mass of comsats in low orbit is fuel to get them to GEO, and stationkeeping for 15 years. The projectile was very simple, pressure fed liquid engine. It used part of the fuel to get itself into orbit, the remainder is transferred to a fuel depot.
The projectile uses GPS nav borrowed from artillery shells to get to the close vicinity of the depot, then the depot has the smarts to find and dock (that way the smarts occurs once, not on every projectile).
Once done, we deorbit and land anywhere, even on concrete. There is a couple of inches of ablative heat shield on the nose, backed up with 10cm of crushable honeycomb. A bit of the heat shield burns off going up, and more coming back. The honeycomb lowers the landing shock to under 1000g's. Since that's the g-force being fired up in the first place, the projectile can already stand that landing.
Our design projectile was about 360kg loaded, if I recall, and about 100kg or less empty, Ill have to dig out the documents to be sure.
We factored in a 4% loss rate on projectiles after you had experience (40% on the first 10, declining as you gain experience).
Costs worked out to $300/kg ongoing if I remember.
Back when I was doing giant space gun work at Boeing :-). Feel free to ask questions. I'm not about to type in several volumes of technical data, but it's nice to see he's converged on the same muzzle velocity we came up with (5.7km/s).
Our desigh: particle-bed heater with Aluminum-oxide heat storage (it's actually #20 sandpaper grit). It's much easier to store hydrogen at room temperature, then heat it just before it hits the barrel. Using small particles, you get lots of area for heat transfer. The particle bed gets warmed up with heaters of your choice over a period of hours, then you fire the gun and in a second or so transfer a good chunk of that heat to the hydrogen.
Why heat the hydrogen? The speed of sound of a gas depends on the molecular weight and temperature, and hot hydrogen works best. The efficiency of a gun drops dramatically as you reach the speed of sound of the working gas. Think of it this way, speed of sound is how fast pressure waves travel.
If the projectile outruns that speed, there is no way for the gas at the back end to send push to the projectile further up the barrel. It's a bit more complicated than that since you are constantly feeding gas from the back end, and the gas right near the projectile is moving almost as fast, so pressure waves can catch up, but on the whole as you get near Mach 1 of the gas, your ability to push drops way down.
Depending on size of the gun, and where you are launching to, the west slope of Hawaii and the Andes are good locations. The first has *long* even slopes, courtesy of lava flows. The second are shorter, steeper slopes, but somewhat higher altitude (less air to fly through), and closer to the equator.
Anyone here think that will not be a major selling point?
(and dont forget the wireless sex toys)
Destroying a missile in boost phase has some options besides burning thru the missile. The nozzle is unlikely to be highly reflective, it is too necessary for it to be strong and hear resistant. The exhaust is also unlikely in the extreme to be reflective. Your laser only needs to deposit enough energy on one or the other to create a shock wave that will damage the nozzle, and you are done.
The nosecone is also not likely to be reflective, because it has to be strong and heat resistant, and flying through the air often generates fog streaks as water vapor gets compressed. Again, you don't have to burn through the wall of the missle, just deposit enough energy to make a shock wave that will damage something important.
Think of it this way: with a hand grenade, the chemical explosives contain the energy to go boom. With the airborne laser, the iodine-oxygen fuel for the laser contains the energy, and the laser is just how you deliver the energy to the near vicinity of the target. Whether heat to failure or shockwave to failure is easier, I will leave to the experts, but there's more than one damage mode to consider when imagining countermeasures
If you define nanotech as technology of scale closer to a nanometer than a micrometer, ie less than 30 nm, then we are one chip fabrication generation away from it at the moment.
As was pointed out above, the thickness of some semiconductor layers already is down in the couple of nm range, the 30nm I refer to is the length and width of features.
Look at the cover of Popular Science, October 1983. Note: I used to work with Dr. Dana Andrews, at Boeing, in the early 80's. We were working on such things back then. Dana was the consultant for the movie 2010. We had fun going to see the movie as a group, and making critiques:
"Hey, that's a subsonic wake, that's wrong"
Aerobraking is a subset of hypersonic aerodynamics. Inflatable things like Ballutes are zero lift pure drag devices. You can also control direction if you use a lifting body shape. if you fly nozzle-first and shoot some cold fuel out, you can use it for a cool film and protect everything from melting.
I just checked, and TPB is still online. If the 4 defendants end up losing their appeal, but the site is still online, will the court case have made any difference?
If TPB site is actually shut down, and the torrent users just shift to the other torrent sites, will it have made any difference?
There's a fundamental problem for the type of people trying to stop file sharing. Their ability to target a particular sharing channel and use the legal system against it takes *years*. The internet and its users can respond and shift to something else much faster.
Its a chase they will always lose.