The Supreme Court ruled yesterday that federal judges are no longer bound by mandatory sentencing guidelines but need only consult them when they punish federal criminals.
Note that judges were not required before this to always impose the "maximum possible sentence", but rather one determined by sentencing guidelines. And now, with the SCOTUS ruling, the guidelines are purely advisory.
In addition, federal prosecutors retain prosecutorial discretion. So you're 0/2.
OK. Please provide a better cite; note that the ruling was not on the basis of the secrecy, but on whether the suspects' reasonable expectation of privacy was violated.
identity theft is mostly accomplished via social engineering and/or improper security controls being installed on complex programmable systems.
Tracking cars with simple ROM devices is a much different technology, more like what we have been doing for emissions control, for instance.
Identity theft is stealing an access credential-- by whatever means (breaking into e-commerce sites, stealing trash that contains the access credential, social engineering) in order to use that access credential to impersonate another person or steal assets.
A computer in a car that monitors GPS and speedometer signals and sends messages over a cellular network is not a simple "ROM device"; it is a somewhat complicated embedded system consisting of instrumentation, embedded processing in the form of a microcontroller (probably a few; in both the GPS chipset, the monitoring device, and the cellular transmitter), and communications facilities. In the system, some sort of access credential or identifier is used to identify the car that has broken the rules and call home. Stealing that credential through appropriate means (physical tampering, social engineering, communications intercepts) would allow you to impersonate that vehicle. See the analogy now?
In any event, the system wouldn't tell the govt. what you were doing, it would tell it what your car was doing, so there is direct 4th amendment issue--it is well established that govt. can monitor your property to prevent you doing something with it that may harm others.
Really? Please give me a relevant citation on that, where probable cause doesn't exist. The law I've searched for says differently:
In Moore DEA agents, without the benefit of a warrant or the owner's consent, surreptitiously attached beepers onto two vehicles parked by defendants in a shopping center parking lot. As the Court of Appeals for the First Circuit framed the issue: "The basic question [was]
whether the use of beepers so implanted to monitor the movements of the U-Haul van and the 1966 Mustang . . . violated defendants' reasonable expectations of privacy." United States v. Moore, supra, at 112. That court answered the question affirmatively, but reasoned that the lessened expectation of privacy associated with motor vehicles justifies the installation and use of beepers without a warrant so long as the officers installing and using the device have probable cause.
Voting machines, another conflation: the majority of drivers are cheating the current speed control system, so we need a new system that reduces cheating-- with voting, the ability to cheat has been increased by the current implementaion, the opposit case.
Ah, but beware of unintended consequences. Before electronic voting machines were widely deployed they were touted as a technological cure-all that would eliminate most abuses and errors in the existing system; as a technologist, I know it is often difficult to arrive at technological systems with a higher level of robustness than tried and true conventional systems; I also know it can be much more difficult to spot and monitor abuses when technology and technology vendors are involved.
I think it would be pretty easy to catch the very few people who would have the knowledge and talent to do this, certainly easier than enforcing the traffic laws using the current system.
You have a lot of faith; check out identity thefts for a nice counterexample. We have a whole ton of people dealing with a big hassle, temporarily losing access to funds, and having to go through great degrees of trouble to prove their innocence/need to not pay debts; very few of the people abusing the system and causing this are getting caught. Worse, identity theft is a well understood and known problem, and requires a much greater of degree of interaction by the thief than a system like the one we're describing would. It is also likely that faith in the technology will cause adverse consequences for those who are framed or erroneously tagged by the technology, especially until abuses become extremely wide in scope and well known.
Why, what are you doing?
Brilliant. Who needs the fourth amendment? After all, you should have nothing to hide; so it's perfectly OK for the government to know everything....it's better to participate in the democratic process to limit abuses of these things than to try and prevent progress...
Sure-- because you know we'll have plenty of infrormation available about how the systems work, and tons of checks and balances on the departments and the vendor to know when things go awry. The bulk of the populace won't be blindsided like they were about electronic voting machines this time around.
An astronaut is probably more likely to die in the plane ride from Wherever, USA to Florida.
And even more likely to die from a car accident on his/her commute from the airport to the Kennedy Space Center than from a shuttle reentry.
Hmm.. I think space travel is relatively safe for the energy level involved.. but still, a.5-3% chance of fatality per mission is not exactly comparable to air transportation or driving; indeed, it's quite likely the risk from a single mission exceeds your lifetime exposure to risk from dying in a traffic collision (either as a pedestrian or in a car-- which is about 1-2%).
In any event, cracking a simple ROM chip is not easy like cracking a Wintel & if just about everyone drove the speed limit it would be pretty easy to catch the crackers. You would stand out pretty well and pissed off citizens would be sending pics from their cell phones to LE.
Modifying what an embedded system does is usually not that difficult at all; microcontrollers are fairly standardized and there's been a lot of effort put into making them easy to develop on and debug. There's sometimes security bits, but they're generally fairly easy to turn off and read the code/data out; once you've reverse engineered things you can burn a new device. And if strong cryptography isn't used, you could just sniff the protocol and figure out how to send messages.
Seems like it would be pretty easy to catch you doing that, since LE would recieve two signals from my car, one that wasn't speeding and one that was.
So I take it you drive 24/7?
I don't like speeders; but also, I don't want a device on my car reporting my driving habits (and who knows what else-- like location, etc) to police.
And was under the impression there are mobo limitations on the amount of RAM which can be installed, regardless of the physical capacity (bays) and the apparent storage of the DIMMs themselves (Someone got anything more defintive on this front?)
The anonymous coward would be correct; you're still limited by the number of address lines hooked up (in the memory controller itself and on the traces on the motherboard); and limited as well by the memory controller's ability to refresh the memory possibly. (The worst case scenario is being able to address the memory but not have it refreshed properly-- resulting in information in upper memory quickly decaying to garbage).
and by design not crumble when bad drivers are installed or poorly written software runs.
No, *BSD and Linux will indeed crumble and happily kernel panic away when bad drivers are in place. Some microkernel OS's are a fair bit better at this, but the market doesn't seem to think the resilience is worth the performance penalty.
You might have a valid point if the article was talking about market share being up 237%; or even if it said that Firefox usage was up 237%. However, it wasn't-- it was talking about visits to the firefox site. Oops.
BTW, if we're talking about visits for your site, it looks like visits by firefox users are up 225% for your site in that timespan-- from 2293 to 7452.
One other point: transistors on exotic processes like these are most suited for wireless and communications applications at this point; problems with power density, logic density, yields, and manufacturability have thus far kept them isolated to radio and interconnect modulation systems to date, rather than bulk logic. These problems are not necessarily insurmountable, but prevent its use in fast microprocessors for the foreseeable future.
And as to your:
they aren't going to be using these devices in a microprocessor pipeline
Really? Many would disagree with you; IBM has been really pushing the edge SiGe and GaAs HBT for logic. I personally think it's unlikely anytime in the next decade, but who knows.
One other point: transistors on exotic processes like these are most suited for wireless and communications applications at this point; problems with power density, logic density, yields, and manufacturability have thus far kept them isolated to radio and interconnect modulation systems to date, rather than bulk logic. These problems are not necessarily insurmountable, but prevent its use in fast microprocessors for the foreseeable future.
Depends on the transistor and its function, actually. In manufacturing of CPUs, individual transitors on critical paths have their geometry specified based on switching time requirements, acceptable upstream capacitive loads, number of loads driven, etc.
Information like this is highly confidential process information (and one of the key things that differentiates foundries from each other).
Because the information is so proprietary, I would be guessing; but I would guess it's on the order of 70-80GHz; the transistors don't actually switch that many times per second in a P4, but they have a switching time of a bit less than 10 picoseconds or so.
In a clock cycle that is 330 picoseconds long, that gives a signal time to propagate through 7-8 levels of gates, and leaves a little bit of spare time for setup and hold requirements.
Notice this is pure speculation on my part; the stuff I've been involved with the design of has been on much larger geometries where interconnect time doesn't matter and switching speed is king; as things become smaller this condition reverses itself.
It all depends on the wiring delay and how many transistors deep a pipeline stage is.
fMax of a pipeline stage is 1/(switching times+wiring delays) under worst case thermal conditions. The wiring delays will stay about the same unless they're also improved by the new process, which is unlikely.
A 600GHz transistor, with really deep pipelines like the P4, and very good interconnect technology might allow 20-50GHz operation; but there are many other things to contend with (like thermals/dissipation) that can limit speed. Thermals, in turn, depend on the amount of capacitance being switched, which isn't specified here.
But anyway, what I'm getting at, is it possible for a human falling purely by the acceleration of gravity in our atmosphere with ambient temperature not exceeding, lets say, 80 degrees at the surface... Is it possible for that falling human to heat up much at all?
At 30000 meters, the density and pressure of the atmosphere are both about 1% of the pressure at sea level; this increases to 10% by 20000 meters. So basically, a person has a lot of altitude to accelerate (70,000 meters in virtually no atmosphere, when jumping from 100km) to high supersonic velocities. Then, that speed will be lost in comparatively little altitude.
The actual speed at 30,000 m will be lower than this, because there is some (but very little) drag.. but I calculate that a jumper will be going about 1180 m/s at 30,000m; this is 2630 MPH. Indeed, this is plausible as Kittinger reached 615MPH jumping from 100,000 feet.
Let's do the math in a back-of-the-envelope fashion since I don't know the exact numbers involved. If you assume terminal velocity is proportional to the square root of the ratio of pressures-- a fair assumption, but broken at high speeds because of compressability effects-- and that terminal velocity of a human body is 200km/hr at sea level, Tv at 30000 m is about 2000 km/hr, versus 630 km/hr at 20km.
Since I don't have air data over this whole region to integrate the real deceleration curve, I'll make a very optimistic assumption for the jumper: the average speed of the fall between 30km and 20km could be 700km/hr (it is likely much faster); this equals 51 seconds of falling (in reality, the heat would be dissipated over much less time). Assuming that the jumper is travelling at 2000 km/hr at 30000m, and 630 km/hr at 20000m, this is a delta v of 1400 km/hr in 51 seconds. Assuming this deceleration is uniform (again, an optimistic assumption):
237 kW over your body's surface area for 51 seconds-- no thanks. Note that all these calculations (other than perhaps the terminal velocity calculation that could be off by 20-40%) are signficantly optimistic with respect to the peak thermal load on the jumper.
No atmosphere, no heat -- the only heat the process will produce in that case will be from the impact.
Uh, ok...
Yes, if you jump from 100km onto a rock with no atmosphere, you indeed will produce no significant heat until you crater at the bottom; but if the rock has nominal earth gravity of 9.8 ms^-2, you indeed will still dissipate ~88MJ.
But the point here is to parachute from 100km; the atmosphere is very thin at 100km, so the person will accelerate at 9.8 ms^-2 for some time. Then, the person will come in contact with the atmosphere, and Q will increase very quickly. Then, over a very small period of time, the person will decelerate to a more familiar terminal velocity and friction will dissipate very large portions of that 88MJ as heat on the person falling.
First law of thermodynamics applies here; if potential energy is lost, it must become some other form of energy. When we're talking about an object falling from up high, eventually it will end up at rest at ground potential (ignoring ridiculous cases where ejecta from an impact reaches orbit, etc). All that potential energy will get traded for kinetic energy and then that will be traded for heat.
Well, terminal velocity doesn't matter for this purpose; every joule of heat will be dissipated by the person as they fall, and it's just a question of how quickly. The time an object spends decelerating to terminal velocity is very small in the upper atmosphere, because the pressure increases so quickly. And aircooling in this case is significant, but not all that effective. (Likewise, heat will be lost by radiation, as well).
Still, 88MJ is a tremendous amount of energy to dissipate over the surface area of a person in tens of seconds.
It would take quite a clever parachute to spread the heat produced over a much longer time-- indeed, things in contact with an atmosphere tend to decelerate to their equilibrium speeds very, very quickly. That is, they quickly decelerate to the point where thrust (or weight, in this case) equals drag. Hence my two minutes was a very very optimistic number in assuming that deceleration would be uniform over a very long time.
The nice thing about the parachute is that it allows the heat to be dissipated over a larger physical area; but still, 88MJ is a lot.
It might be possible to use a variable area parachute/system of multiple parachutes to stretch the time over which deceleration occurs, but this would be tricky as atmospheric pressure increases so fast relatively in the upper atmosphere. And anyways, as I was arguing: thermals would be one of the principle design problems of such a system.
Well, it's not as if you're at orbital velocity at low altitudes, but there is a nontrivial amount of energy you've accumulated.
For instance, a 80kg person who is 100km up the space elevator has accumulated ~80MJ of potential energy; this is a nontrivial amount of energy that will be dissipated as heat over a very short period-- the vast majority of it in a couple minutes.
I don't know the appropriate constants offhand (surface area of a person, etc) to calculate temperature under these thermal loads, but i can throw out a few numbers:
80MJ = 19 megacalories-- enough to raise the temperature of 190 kilograms of water by 100 degrees celsius.
80MJ = enough to run 450 standard home 1500W space heaters for the 2 minutes of heating.
So clearly, thermal considerations do matter for jumping from 100km.
He's talking about a CNAME; a CNAME is like a symbolic link for DNS. That is, if you try and look up www.foo.com, it can contain a CNAME saying that www.foo.com is an alias for www.google.com. This can be really nice, because if you have many services running on one server, you can CNAME (e.g. you could have one big host, bigserver, and CNAME www.whatever.com for multiple domains to bigserver; if bigserver's address gets changed, you only need to modify one zone file).
If a DNS server returns a CNAME record, it's supposed to return an address record for the destination server if it can; e.g. it says
www.foo.com. IN CNAME www.google.com. www.google.com. IN A 64.233.187.99
Bad things happen if the server that hosts DNS for foo.com is malicious and returns an invalid address for www.google.com; because naïve DNS implementations would then trust foo.com's address for google.com.
The whole hybrid trick wouldn't work for airplanes very well. Hybrid technology in car relies on the fact that most of the time only a small amount of power is needed to cruise or idle; but the engine needs to be sized for much larger acceleration/hill climbing requirements. Hybrids size the engine a little bigger than the cruise requirements, and add batteries for peak acceleration.
Airplanes spend most of their time at 75% power or more; so the efficiency advantage would be next to nil; coupled with the fact that batteries are heavy, you'd likely get much worse efficiency than current technologies.
I saw a French research company that is making cars run off of compressed air. Using a Carbon-fibre based compressed air canister, the PSI in the tank is about around 3500 or 3800. There is enough air in the tank to drive about 130 to 180 km @ 60 KM/H.
Yes, but how much energy are you throwing away when you initially compress the air, and then when you use it to power the car? I'd guess 50% or more each time; so even if you have an ideal power source providing power to your air compressor you'd get less efficiency than an internal combustion engine. Batteries/motors are much better in power conversion efficiency.
Nice retreat from your previous position. As I said many posts ago:
Look, you're confused, OK? Why don't you just admit it? There is clear notice of copyright on the XML recommendation (as exists on all W3C recommendations), and W3C has a specific license for distribution of the standards. If you duplicate a W3C standard, and don't keep with the requirements (e.g. you change the standard, or you remove the linkback to the canonical version on the W3C site, etc), you will get a C&D for violating the copyright and license agreement. If you don't comply with that C&D, you'll most likely get sued. And if you get sued, they will win.
Notice I said "duplicate the standard", and "distribution of the standards", not implementation of the standard. Writing a program that implements XML and distributing it is not a distribution of the XML standard; sticking the standards document on a webpage is. I think you also misunderstand the reasoning for the copyright protection and limited redistribution licenses-- it helps to prevent third parties from creating modified versions of the standard text that others might rely on, and allows an organization like W3C to keep control of the canonical version of the standard. Likewise, the reason why many other standards are copyrighted is to provide funding for the particular standards body; creating standards costs money, and people building implementations realistically need the standards document in order to verify that they comply with it; hence, the standards body charges for physical copies of the standard (just about every standards body in the world does this; W3C and IETF are welcome exceptions compared to others like ANSI, IEEE, ASME, PCI-SIG, SD Association, etc).
I have 6 patents issued (with all of the claims intact except in one case) and 20 patents pending; so I think it's pretty clear I have an idea what the scope is of patent protection. Likewise, I sat on the patent committee of Symantec, and made determinations as to what the company should and should not file for; likewise, I've worked with the IEEE in the past, so I have a pretty good idea of what standards bodies use IPR protection for.
You're the one who made the original post and was grossly in error as everyone pointed out. Please kindly stop spouting nonsense. kthx.
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From the Washington Post:
Note that judges were not required before this to always impose the "maximum possible sentence", but rather one determined by sentencing guidelines. And now, with the SCOTUS ruling, the guidelines are purely advisory.
In addition, federal prosecutors retain prosecutorial discretion. So you're 0/2.
OK. Please provide a better cite; note that the ruling was not on the basis of the secrecy, but on whether the suspects' reasonable expectation of privacy was violated.
Tracking cars with simple ROM devices is a much different technology, more like what we have been doing for emissions control, for instance.
Identity theft is stealing an access credential-- by whatever means (breaking into e-commerce sites, stealing trash that contains the access credential, social engineering) in order to use that access credential to impersonate another person or steal assets.
A computer in a car that monitors GPS and speedometer signals and sends messages over a cellular network is not a simple "ROM device"; it is a somewhat complicated embedded system consisting of instrumentation, embedded processing in the form of a microcontroller (probably a few; in both the GPS chipset, the monitoring device, and the cellular transmitter), and communications facilities. In the system, some sort of access credential or identifier is used to identify the car that has broken the rules and call home. Stealing that credential through appropriate means (physical tampering, social engineering, communications intercepts) would allow you to impersonate that vehicle. See the analogy now?
In any event, the system wouldn't tell the govt. what you were doing, it would tell it what your car was doing, so there is direct 4th amendment issue--it is well established that govt. can monitor your property to prevent you doing something with it that may harm others.
Really? Please give me a relevant citation on that, where probable cause doesn't exist. The law I've searched for says differently:
Voting machines, another conflation: the majority of drivers are cheating the current speed control system, so we need a new system that reduces cheating-- with voting, the ability to cheat has been increased by the current implementaion, the opposit case.
Ah, but beware of unintended consequences. Before electronic voting machines were widely deployed they were touted as a technological cure-all that would eliminate most abuses and errors in the existing system; as a technologist, I know it is often difficult to arrive at technological systems with a higher level of robustness than tried and true conventional systems; I also know it can be much more difficult to spot and monitor abuses when technology and technology vendors are involved.
I think it would be pretty easy to catch the very few people who would have the knowledge and talent to do this, certainly easier than enforcing the traffic laws using the current system.
...it's better to participate in the democratic process to limit abuses of these things than to try and prevent progress...
You have a lot of faith; check out identity thefts for a nice counterexample. We have a whole ton of people dealing with a big hassle, temporarily losing access to funds, and having to go through great degrees of trouble to prove their innocence/need to not pay debts; very few of the people abusing the system and causing this are getting caught. Worse, identity theft is a well understood and known problem, and requires a much greater of degree of interaction by the thief than a system like the one we're describing would. It is also likely that faith in the technology will cause adverse consequences for those who are framed or erroneously tagged by the technology, especially until abuses become extremely wide in scope and well known.
Why, what are you doing?
Brilliant. Who needs the fourth amendment? After all, you should have nothing to hide; so it's perfectly OK for the government to know everything.
Sure-- because you know we'll have plenty of infrormation available about how the systems work, and tons of checks and balances on the departments and the vendor to know when things go awry. The bulk of the populace won't be blindsided like they were about electronic voting machines this time around.
An astronaut is probably more likely to die in the plane ride from Wherever, USA to Florida.
.5-3% chance of fatality per mission is not exactly comparable to air transportation or driving; indeed, it's quite likely the risk from a single mission exceeds your lifetime exposure to risk from dying in a traffic collision (either as a pedestrian or in a car-- which is about 1-2%).
And even more likely to die from a car accident on his/her commute from the airport to the Kennedy Space Center than from a shuttle reentry.
Hmm.. I think space travel is relatively safe for the energy level involved.. but still, a
In any event, cracking a simple ROM chip is not easy like cracking a Wintel & if just about everyone drove the speed limit it would be pretty easy to catch the crackers. You would stand out pretty well and pissed off citizens would be sending pics from their cell phones to LE.
Modifying what an embedded system does is usually not that difficult at all; microcontrollers are fairly standardized and there's been a lot of effort put into making them easy to develop on and debug. There's sometimes security bits, but they're generally fairly easy to turn off and read the code/data out; once you've reverse engineered things you can burn a new device. And if strong cryptography isn't used, you could just sniff the protocol and figure out how to send messages.
Seems like it would be pretty easy to catch you doing that, since LE would recieve two signals from my car, one that wasn't speeding and one that was.
So I take it you drive 24/7?
I don't like speeders; but also, I don't want a device on my car reporting my driving habits (and who knows what else-- like location, etc) to police.
And was under the impression there are mobo limitations on the amount of RAM which can be installed, regardless of the physical capacity (bays) and the apparent storage of the DIMMs themselves (Someone got anything more defintive on this front?)
The anonymous coward would be correct; you're still limited by the number of address lines hooked up (in the memory controller itself and on the traces on the motherboard); and limited as well by the memory controller's ability to refresh the memory possibly. (The worst case scenario is being able to address the memory but not have it refreshed properly-- resulting in information in upper memory quickly decaying to garbage).
and by design not crumble when bad drivers are installed or poorly written software runs.
No, *BSD and Linux will indeed crumble and happily kernel panic away when bad drivers are in place. Some microkernel OS's are a fair bit better at this, but the market doesn't seem to think the resilience is worth the performance penalty.
Hi, Dr. Moron!
You might have a valid point if the article was talking about market share being up 237%; or even if it said that Firefox usage was up 237%. However, it wasn't-- it was talking about visits to the firefox site. Oops.
BTW, if we're talking about visits for your site, it looks like visits by firefox users are up 225% for your site in that timespan-- from 2293 to 7452.
Standard n.
A flag, banner, or ensign, especially:
The ensign of a chief of state, nation, or city.
A long, tapering flag bearing heraldic devices distinctive of a person or corporation.
An emblem or flag of an army, raised on a pole to indicate the rallying point in battle.
The colors of a mounted or motorized military unit.
vs.
Indeed, that's what the word "standard" meant of old. A standard is a pole, a stick -- such as a flagpole, hence the term "standard-bearer".
So you're saying a flagpole is called a standard bearer because it.. bears a stick, rather than bearing a flag?
My OED is upstairs, but according to NOAD it's a shortening of Old French estendart, from estendre 'extend'.
From my post over 3 hours before your post:
One other point: transistors on exotic processes like these are most suited for wireless and communications applications at this point; problems with power density, logic density, yields, and manufacturability have thus far kept them isolated to radio and interconnect modulation systems to date, rather than bulk logic. These problems are not necessarily insurmountable, but prevent its use in fast microprocessors for the foreseeable future.
And as to your:
they aren't going to be using these devices in a microprocessor pipeline
Really? Many would disagree with you; IBM has been really pushing the edge SiGe and GaAs HBT for logic. I personally think it's unlikely anytime in the next decade, but who knows.
One other point: transistors on exotic processes like these are most suited for wireless and communications applications at this point; problems with power density, logic density, yields, and manufacturability have thus far kept them isolated to radio and interconnect modulation systems to date, rather than bulk logic. These problems are not necessarily insurmountable, but prevent its use in fast microprocessors for the foreseeable future.
Depends on the transistor and its function, actually. In manufacturing of CPUs, individual transitors on critical paths have their geometry specified based on switching time requirements, acceptable upstream capacitive loads, number of loads driven, etc.
Information like this is highly confidential process information (and one of the key things that differentiates foundries from each other).
Because the information is so proprietary, I would be guessing; but I would guess it's on the order of 70-80GHz; the transistors don't actually switch that many times per second in a P4, but they have a switching time of a bit less than 10 picoseconds or so.
In a clock cycle that is 330 picoseconds long, that gives a signal time to propagate through 7-8 levels of gates, and leaves a little bit of spare time for setup and hold requirements.
Notice this is pure speculation on my part; the stuff I've been involved with the design of has been on much larger geometries where interconnect time doesn't matter and switching speed is king; as things become smaller this condition reverses itself.
It all depends on the wiring delay and how many transistors deep a pipeline stage is.
fMax of a pipeline stage is 1/(switching times+wiring delays) under worst case thermal conditions. The wiring delays will stay about the same unless they're also improved by the new process, which is unlikely.
A 600GHz transistor, with really deep pipelines like the P4, and very good interconnect technology might allow 20-50GHz operation; but there are many other things to contend with (like thermals/dissipation) that can limit speed. Thermals, in turn, depend on the amount of capacitance being switched, which isn't specified here.
At 30000 meters, the density and pressure of the atmosphere are both about 1% of the pressure at sea level; this increases to 10% by 20000 meters. So basically, a person has a lot of altitude to accelerate (70,000 meters in virtually no atmosphere, when jumping from 100km) to high supersonic velocities. Then, that speed will be lost in comparatively little altitude.
The actual speed at 30,000 m will be lower than this, because there is some (but very little) drag.. but I calculate that a jumper will be going about 1180 m/s at 30,000m; this is 2630 MPH. Indeed, this is plausible as Kittinger reached 615MPH jumping from 100,000 feet.
Let's do the math in a back-of-the-envelope fashion since I don't know the exact numbers involved. If you assume terminal velocity is proportional to the square root of the ratio of pressures-- a fair assumption, but broken at high speeds because of compressability effects-- and that terminal velocity of a human body is 200km/hr at sea level, Tv at 30000 m is about 2000 km/hr, versus 630 km/hr at 20km.
Since I don't have air data over this whole region to integrate the real deceleration curve, I'll make a very optimistic assumption for the jumper: the average speed of the fall between 30km and 20km could be 700km/hr (it is likely much faster); this equals 51 seconds of falling (in reality, the heat would be dissipated over much less time). Assuming that the jumper is travelling at 2000 km/hr at 30000m, and 630 km/hr at 20000m, this is a delta v of 1400 km/hr in 51 seconds. Assuming this deceleration is uniform (again, an optimistic assumption):
237 kW over your body's surface area for 51 seconds-- no thanks. Note that all these calculations (other than perhaps the terminal velocity calculation that could be off by 20-40%) are signficantly optimistic with respect to the peak thermal load on the jumper.
No atmosphere, no heat -- the only heat the process will produce in that case will be from the impact.
Uh, ok...
Yes, if you jump from 100km onto a rock with no atmosphere, you indeed will produce no significant heat until you crater at the bottom; but if the rock has nominal earth gravity of 9.8 ms^-2, you indeed will still dissipate ~88MJ.
But the point here is to parachute from 100km; the atmosphere is very thin at 100km, so the person will accelerate at 9.8 ms^-2 for some time. Then, the person will come in contact with the atmosphere, and Q will increase very quickly. Then, over a very small period of time, the person will decelerate to a more familiar terminal velocity and friction will dissipate very large portions of that 88MJ as heat on the person falling.
First law of thermodynamics applies here; if potential energy is lost, it must become some other form of energy. When we're talking about an object falling from up high, eventually it will end up at rest at ground potential (ignoring ridiculous cases where ejecta from an impact reaches orbit, etc). All that potential energy will get traded for kinetic energy and then that will be traded for heat.
Well, terminal velocity doesn't matter for this purpose; every joule of heat will be dissipated by the person as they fall, and it's just a question of how quickly. The time an object spends decelerating to terminal velocity is very small in the upper atmosphere, because the pressure increases so quickly. And aircooling in this case is significant, but not all that effective. (Likewise, heat will be lost by radiation, as well).
Still, 88MJ is a tremendous amount of energy to dissipate over the surface area of a person in tens of seconds.
It would take quite a clever parachute to spread the heat produced over a much longer time-- indeed, things in contact with an atmosphere tend to decelerate to their equilibrium speeds very, very quickly. That is, they quickly decelerate to the point where thrust (or weight, in this case) equals drag. Hence my two minutes was a very very optimistic number in assuming that deceleration would be uniform over a very long time.
The nice thing about the parachute is that it allows the heat to be dissipated over a larger physical area; but still, 88MJ is a lot.
It might be possible to use a variable area parachute/system of multiple parachutes to stretch the time over which deceleration occurs, but this would be tricky as atmospheric pressure increases so fast relatively in the upper atmosphere. And anyways, as I was arguing: thermals would be one of the principle design problems of such a system.
We've got a little bit of an anal fixation, don't we?
Well, it's not as if you're at orbital velocity at low altitudes, but there is a nontrivial amount of energy you've accumulated.
For instance, a 80kg person who is 100km up the space elevator has accumulated ~80MJ of potential energy; this is a nontrivial amount of energy that will be dissipated as heat over a very short period-- the vast majority of it in a couple minutes.
I don't know the appropriate constants offhand (surface area of a person, etc) to calculate temperature under these thermal loads, but i can throw out a few numbers:
80MJ = 19 megacalories-- enough to raise the temperature of 190 kilograms of water by 100 degrees celsius.
80MJ = enough to run 450 standard home 1500W space heaters for the 2 minutes of heating.
So clearly, thermal considerations do matter for jumping from 100km.
...the only communicable diseases that are seriously fatal are biologically engineered bacteria, and viruses.
:)
As opposed to what, just-kidding-fatal?
He's talking about a CNAME; a CNAME is like a symbolic link for DNS. That is, if you try and look up www.foo.com, it can contain a CNAME saying that www.foo.com is an alias for www.google.com. This can be really nice, because if you have many services running on one server, you can CNAME (e.g. you could have one big host, bigserver, and CNAME www.whatever.com for multiple domains to bigserver; if bigserver's address gets changed, you only need to modify one zone file).
If a DNS server returns a CNAME record, it's supposed to return an address record for the destination server if it can; e.g. it says
www.foo.com. IN CNAME www.google.com.
www.google.com. IN A 64.233.187.99
Bad things happen if the server that hosts DNS for foo.com is malicious and returns an invalid address for www.google.com; because naïve DNS implementations would then trust foo.com's address for google.com.
Also "its" means it is, "it's" is the possesive from of it.
Maybe you want to look that one up again?
The whole hybrid trick wouldn't work for airplanes very well. Hybrid technology in car relies on the fact that most of the time only a small amount of power is needed to cruise or idle; but the engine needs to be sized for much larger acceleration/hill climbing requirements. Hybrids size the engine a little bigger than the cruise requirements, and add batteries for peak acceleration.
Airplanes spend most of their time at 75% power or more; so the efficiency advantage would be next to nil; coupled with the fact that batteries are heavy, you'd likely get much worse efficiency than current technologies.
I saw a French research company that is making cars run off of compressed air. Using a Carbon-fibre based compressed air canister, the PSI in the tank is about around 3500 or 3800. There is enough air in the tank to drive about 130 to 180 km @ 60 KM/H.
Yes, but how much energy are you throwing away when you initially compress the air, and then when you use it to power the car? I'd guess 50% or more each time; so even if you have an ideal power source providing power to your air compressor you'd get less efficiency than an internal combustion engine. Batteries/motors are much better in power conversion efficiency.
Nice retreat from your previous position. As I said many posts ago:
Look, you're confused, OK? Why don't you just admit it? There is clear notice of copyright on the XML recommendation (as exists on all W3C recommendations), and W3C has a specific license for distribution of the standards. If you duplicate a W3C standard, and don't keep with the requirements (e.g. you change the standard, or you remove the linkback to the canonical version on the W3C site, etc), you will get a C&D for violating the copyright and license agreement. If you don't comply with that C&D, you'll most likely get sued. And if you get sued, they will win.
Notice I said "duplicate the standard", and "distribution of the standards", not implementation of the standard. Writing a program that implements XML and distributing it is not a distribution of the XML standard; sticking the standards document on a webpage is. I think you also misunderstand the reasoning for the copyright protection and limited redistribution licenses-- it helps to prevent third parties from creating modified versions of the standard text that others might rely on, and allows an organization like W3C to keep control of the canonical version of the standard. Likewise, the reason why many other standards are copyrighted is to provide funding for the particular standards body; creating standards costs money, and people building implementations realistically need the standards document in order to verify that they comply with it; hence, the standards body charges for physical copies of the standard (just about every standards body in the world does this; W3C and IETF are welcome exceptions compared to others like ANSI, IEEE, ASME, PCI-SIG, SD Association, etc).
I have 6 patents issued (with all of the claims intact except in one case) and 20 patents pending; so I think it's pretty clear I have an idea what the scope is of patent protection. Likewise, I sat on the patent committee of Symantec, and made determinations as to what the company should and should not file for; likewise, I've worked with the IEEE in the past, so I have a pretty good idea of what standards bodies use IPR protection for.
You're the one who made the original post and was grossly in error as everyone pointed out. Please kindly stop spouting nonsense. kthx.