In the UK witness coaching is not allowed even if you are the defendant. So you are not allowed to refer to council if you are on the stand, you just have to answer the questions asked. Your lawyer can go through questions that may be asked but they cannot tell you how to answer them.
F-22 has supercruise capability i.e. that is can maintain supersonic flight without afterburners, as can the the Eurofighter Typhoon but historically so could both Concorde and the TU-144 and a few other aircraft.
The first aircraft to supercruise was the English Electric Lightning which did so in 1954
Concorde was a truley amazing aircraft nothing has come close to its perfomance and range, it could cruise at mach 2.02 for 4500 miles!
compare that with new aircraft like the F22 which has about a 600mile supercruise range, The Eurofighter is even less. (but the can refuel when flying)
I completely agree with you, however my stats for houses in the UK are pretty accurate the average UK domestic electricity bill in 2006 was 95.75 GBP per quarter and average electricity price of about 9.9p/kWh this is mainly due to the fact that most houses are heated with gas or oil. Standard UK domestic supply available capacity is 100A at 240V.
I am interested to know why cooling towers are not used, I understand that when near the coast or large river it is far better just to dump the heat into water but when that is not available I believed they were the most efficient way to dump heat into the atmosphere, apart from the planning issues. I understand that a forced convection method would be more compact but it would consume quite a bit of power?
1GW is huge amount of power, to give people some idea, very few houses have an average load of more that about 0.5 a kW (.5kw * 24hours * 90days * 10pence = £108 per quarter bill) most are way below that. So you are talking about the equivalent of about 2 million house supplies! Or say 1million electric bar heaters, which if you laid them out each within a square 0.5m * 0.5m you would need a field with 500m sides and it would be seriously warm!
The fundamental thing that is missing is the amount of power being generated.
You have to cool the steam down somehow, normally it looses energy by turning the generators but if that is not the case the energy needs to go somewhere.
The steam is normally re-condensed and then reused in a closed or semi closed loop depending on whether there are cooling towers. There is no way that the
cooling capacity would be able to dissipate the full load and hence the need to rapidly shut-down. This is the same for coal and gas plants as well.
The pressure is not really that great 1Atm is about 14 pounds per square inch, with a cylinder and hemispherical shape you can withstand incredible pressures, you just cannot have any weak spots.
Bicycle tyres are inflated to up to 80 pounds per square inch.
A submarine has to undergo far greater pressures, even though the air is kept at say 1 Atm internally the pressure underwater goes up by 1Atm per 10m depth so
the pressure at say 915m depth would be 1316 pounds per square inch! (record manned sub with full crew 1968)
The analogue cell network had much greater separation between towers which required considerably higher power output from both the phone (several watts) and the tower.
Also with digital you can improve the SNR dramatically therefore reducing the power required.
These 2 factors are what led to digital networks requiring a lower power output from the phone combined with the greatly improved tower technology for ultra low power signal reception which used to require cooling with liquid nitrogen to get a low thermal background noise.
It should be noted that the towers for digital have to be closer together as they tend to use higher frequencies which require line of sight whereas the older 900MHz networks would go through things much better, this is one of the advantages of the 700MHz network that Google is bidding for.
Also with CAT5/6 you have to untwist some of the cable when you use connectors which affects the cable velocity due to the change in effective dielectric, whereas with fibre you really only get an attenuation as the joins are not in-line, the length of material change(glue) is small in comparison to a few tens of mm for a CAT cable plug and patch.
I do agree with you, however the accuracy of the groove is in reality less than half the equation as the needle pick-up is actually where the problem lies. The upper end of human hearing is at around 20kHz which means the needle needs to vibrate at 20,000 times a second both vertically and horizontally (stereo), it must do this with no resonance or harmonics that is within the audio range and it must faithfully represent the movement of the grove, which requires a linear voltage to be produced depending on the deflection. This is non trivial in engineering terms, therefore expensive. (If you use a laser to read the vinyl this is not an issue but you will then most probably be digitally sampling the result in any case.).
Another interesting point about vinyl is that the frequency response is different as you go from the outside grooves to the centre. Better frequency resp. at the outside considerably so in fact, it is the same with analogue tape and is also the reason that we had to wait till helical/transverse scan worked before video was practical on home systems as the tape speed was to great. The BBC recorded video to steel ribbon which ran very fast and required miles of tape.
While in principle you are correct you will still have in the region of hundreds of Amps, 100Amps would be 2.5MW which just might power a train, it is still only about 3000 horse power.
You increase the voltage to reduce the resistance losses (Power = I^2R) however you are limited by what can effectively be used in a safe manner with a pantograph.
Even super grid wires which in the UK run at 450 KV still have large currents ~ 1,000Amps which is why they are so hot ~200 deg C when under load (this is actually what limits the max load as the wires sag as they get hotter and they must not fall below the minimum safe height).
To put that into perspective 1000 Amps would be still under 0.5Gw and there is a 6GW power station in the UK, most are around 1GW.
The car computer analogy completely breaks down due to the fact that there is no single car manufacturer who supplies 95% of all cars.
If that were the case then you can bet that Sony would sue if that manufacturer chose Philips etc. instead.
In the car market you have a relatively large number of manufacturers and it is unlikely that they will all bundle the same make
of CD player.
The record in question actually has nothing to do with solar power. It is purely an endurance record for longest flight time under continuous power. The Global Hawk is actually powered by a turbojet engine and normal Jet A1 fuel.
Solar powered aircraft have been quite successful for some time for instance the Pathfinder and Helios aircraft by NASA the biggest issue is to get through the night on battery power. I believe the NASA aircraft had to resort to gliding and soaring which this aircraft does not.
A purely battery aircraft would fall out of the sky in a relatively short period of time, it would probably not even get to altitude before having to glide home.
Typically solar vehicles have to start races with the energy store empty however this is very unlikely in this case as they were just doing some tests. The flight tests all seem to end when there is an issue with the aircraft or the weather is not looking good. So it may well be the case that it would not be able to stay airborne indefinitely.
You are correct, it is part of the GSM mobile specification. If I recall correctly it is a drop test of 1.2m or 1.5m onto concrete. The phone is allowed to come apart, e.g. the battery may detach, but it should work fine once re-assembled.
Interesting enough VW have already done it, see: http://www.greencarcongress.com/2005/04/vw_abandon s_its.html The VW Lupo is available but it only does 78.4mpg(US). Their development car did much better: 0.89 litres of diesel per 100 kilometres (264 mpg) top speed was still 75mph. but they could not make the commercial version cheaper than $25K
Can I strongly suggest that NOBODY tries this at home. Gasoline in its liquid state will always have fumes above it at room temperature, and throwing a match into it will definitely result in a very severe fire!
The match going out comment in more usually attributed to Diesel fuels, Kerosene and paraffin, which have a much higher flash point, and a higher boiling point. This means there is little vapor above the liquid and they are not likely to be ignited by a lighted match. It usually requires a wick to make fuel Oils burn e.g. a rag etc. or alternatively high temp and pressure such as in a diesel engine or gas turbine.
Simple, on the way up you have air and therefore great resistance. So it is far better to go up at mach 2-3 and then when in space (no air) turn around and rocket propel yourself back towards the atmosphere, doing most of your acceleration before you hit the atmosphere. This way you have to use much less fuel and a much smaller rocket. Air resistance is a far bigger proportion of the expended energy than that of gravity.
This kind of test has been used at Woomera many times before, originally developed by the British for testing reentry systems for warheads in the 50's, the Black Arrow program. Incidentaly this was so successful that the Americans paid to extend the program so they could use the results. Basically they stuck the test reentry unit on top of a rocket, flew it to space then used a rocket to propel it towards the ground at up to mach 12, to test the materials and telemetry.
Interestingly the British re-entry warhead design was the opposite of the USA in that it came down pointy end first whereas the US models at that time came down blunt end first. The British design was far better as it came down much faster and therefore was much more difficult to intercept.
FYI The record for air breathing aircraft (not rocket) is 85,068 feet, set in 1976 by a Lockheed SR-71 jet-powered aircraft. This was broken by the NASA helios solar powered (not air breathing) flying wing 96,500 feet in 2001 Concorde was the highest flying commercial airliner with an operational ceiling of 60,000 feet.
The SR-71(AKA blackbird had very specialised jet-engines which operated in a semi ramjet mode.
The biggest problems with a scram-jet is trying to make it a scram-jet, i.e. the airflow through the engine has to remain supersonic. The shock wave angle decreases with mach speed, at low mach numbers it is too wide. This means that you have to have an impossibly large diameter and short engine to maintain supersonic flow. When you get hypersonic (above mach 5) the shock waves get much closer to parallel to the direction of motion, hence you can have a reasonable length and diameter on your engine. The length is the critical problem, as it is necessary to combust fuel and expand the working mass (air) within the engine in order that it can do any useful work. This is very difficult as mach 5 is 1701.45 m/s so if you have a 2m engine tube you have roughly 1.2 milliseconds in which to compress, burn and expand your fuel! The rate of flame propagation in kerosene is just not high enough to get even close at this kind of scale therefore hydrogen is realistically the only fuel which will work as it has the highest flame propagation rate, even hydrogen is difficult.
Scram-jets are a very interesting technology, but there are others like air breathing rocket motors which use the liquid hydrogen to cool the intake air so that it can be compressed sufficiently to be fed into the rocket combustion chamber. This is a pretty good technique although the heat exchangers are pretty difficult to build. The have the advantage that you just bleed in more and more O2 as you leave the atmosphere until they are running in pure rocket mode. They do have the disadvantage that they can realistically only operate with a max velocity of about mach 5.5 when air-breathing as above that you get 0 net thrust and they are fairly complex. Air breathing rockets make single stage to orbit possible without ridiculous fuel to weight ratios.
Encryption is unfortunately directly opposed to that other very important networking tool compression.
By definition compression usually uses patterns in order to reduce the amount of data being send and also by definition encryption deliberately removes patterns as much as possible.
This fact is made even worse when the size of the data being encrypted is small as in (IM etc.) as it is necessary to pack the data with extra 'rubbish' data in order that it does not become trivial to decrypt, because it will not contain enough randomness (entropy). This is one of the issues with SSH style protocols, if one character is sent at a time over an encrypted socket then instead of trying to crack the encryption you just use time between keystroke's and the probabilities of the various keys being hit on the keyboard due to their distance apart and typing difficulty. Given a sufficiently large sample it is relatively easy, as long as the same person is typing. There are obviously methods to avoid this.
I agree that it would be great if things were built secure from the start and it will become what happens with any luck, but Internet network bandwidth is going to have to multiply before this becomes a reality. SMTP for instance would be an ideal candidate for encryption however it is bloated enough with the MIME encoding of attachments. Using PGP style plugins is great but again the message size multiplies.
VNC is an interesting one, I personally use it a great deal and mostly over VPN's to manage many disparate server systems, it would be nice if it was not necessary to have to open up the separate VPN's, however all the other traffic, filesharing etc. already use VPN's so really it is not that bad and would result in yet another firewall port to be forwared.
I mostly develope with Java which makes adding encryption to software trivially easy with the securoty libraries which are included by default. This is the case with most languages so the difficulty is not the problem, just speed and data size.
Short example using gnupg: Message text: This is a test to demonsrate the size difference Encrypted text: hQEOA/xuotSLmEetEAP9E3zO4QuUUYiLZLXUyuIpCf/wYCxQhv J5sdcNrws2sRGGwgpAGS7 A3syqu16/EktGavpjX+pRa74R3WAygphL8xOgw/Jze/zB3RvWJ Y3OBriBzWvN06uB9LuGhx k2DSieJcGw1zkj89JXTUyKptrW/iFOdEojLXe/V5k/W/coGM4D /1NhB2JOaTqzqvV4I5TPq 0KhLs19Z2cV4J+jGE7rJritBhyGU4lRRPYIjbkRFnYJQ6/iDsj 0Qh/zXLxAF5OMj+CcqzP8 fJvD/ovh9ARnKdNaoAbUCbBY0AWjFY1dgHCItXz0hu4iquhvLl Lqiguj4yXuRlCmwYUZg9u ZByvAoSBNhQEOAxwUT1jMpp2zEAP/cTX3aH4sOHcnVO6FzO9Qd 8UexU9cFhmPMP/gBAtxQk uGMzGk5LpXNeL5WPmOnt+TXEWHAHRT/gYMZYZKqxFyn9Fj7cfI NvEFfI5SeqVtQS6/gJ/zf mBXVP/UimwlgmsVbnS51qhLPRR3WKOoIiPiX+WnZRkp/cTKktD O94HtKHoEALZvrSbgXejd FYqdcFXifsJoLPUdlVGyjrGkbxXSKRntq/87eXUGe3g7K6/LjQ c2osoNLiqFVTjc7DRVWnN qdydPwIy+IsOpIuGom+V2I496lydOyKuMJLRUujlqDWRcduesO rkEGl3JbT3p3vo1J05UFV 2Maqon1WdtKfFA/nCF0moBK5rMbK/Fzi7kd5uZ4lviIJZhWIru bqNIROM96YrGzMjWHEwsR qaPLEXdYY3VBhBb9dzzuAweQAon/uwXtjwvmn7o5JjMAY0/QP5 SEpqCK/37DY3Xxr/qZhwi e4dZoXFmubLLbd3/5Zv2
Yes they could, but He is very expensive stuff, hence why recondensing is an option, but the equipment is heavy!. This would also limit the number of trips.
You are correct in your main assumptions apart from the fact that this particular design is not designed for VTOL.
It gains approx 20% of its lift from its aerodynamic form, which obviously requires it to have forward velocity to "fly". This results in quite a large saving in volume of lifting gas.
The lifting gas issue is actually one of the biggest problems with theses airships as it is all fine when you have the load on, but what do you do when you have unloaded. You suddenly have an enormous mass requirement. Options such as compressing and condensing the He have been considered, but not practical, loading with water / earth are options but AFAIK there is no simple solution to this problem. Added to the fact that this issue gets much harder to solve as the lifting capabilities are increased. Especially since the whole idea is to be able to land in remote locations!
While I do agree with your point that 25 years is a long term investment, so is building a nuclear power station, in UK ~15 years for planning application ~10-15 years to build and ~50 year lifespan.
It is very difficult to make the numbers add up in the short term for any kind of energy generation, the same argument applies to Coal fired, wind, water wheels/turbines, tidal.
The only 'quick buck' was and still is to a certain extent Gas. Quick to build, less environmental penalties (financial) than coal, relatively cheap to build, can be built on a small scale and still have good efficiency. Also gas has the great advantage of very fast startup and stop times meaning that they can cream off the top of the energy price markets as the online time is much faster. For example a typical gas turbine(100MW unit with waste heat steam turbine) start-up time to full load is around 90 mins. Compared to Coal approx 12 hours for cold start.
This is why we built a load of Gas fired plants in the UK, unfortunately we are now running out of gas and are a net importer again.
So in a real sense the best investment opportunity for short term (in power systems) is in insulation and other efficiency systems to reduce energy requirements as these typically are paid back in saving in 1 to 5 years:).
My personal opinion is that 25 years may seem a terrible investment but in Power generation terms that is pretty fast.
Sorry but this is simply not the case. Typical solar panels even in 1994 would have a production energy pay-back period of around 50 months. http://www.ecotopia.com/apollo2/pvpayback.htm More modern cells are even better, typical payback of a couple of years depending on location.
On the other had financially speaking you are talking about 25 years to recoup the cost of installation, which is why adoption has to be promoted by governments as very few people are prepared to think that far ahead!.
Well in th UK we generates around 25% of Electricity with gas, so I would say that it is a pretty huge percentage, especially given that the UK used to supply 100% of its own gas but as supplies in the North Sea reduce we are now importing around 18% of the gas we use, so the protection of energy supply becomes more difficult (threat to national security).
Nuclear power is generating around 20% coal and renewables the rest. The pecentages change dynamically due to market forces. (Gas comes on-line quicker than coal, pollutes less and costs more than coal.) Nuclear is run all the time and Coal and Gas fight it out for the rest.
Slashdot Mirror
In the UK witness coaching is not allowed even if you are the defendant. So you are not allowed to refer to council if you are on the stand, you just have to answer the questions asked. Your lawyer can go through questions that may be asked but they cannot tell you how to answer them.
They did, it is called The Flying Scotsman.
F-22 has supercruise capability i.e. that is can maintain supersonic flight without afterburners, as can the the Eurofighter Typhoon but historically so could both Concorde and the TU-144 and a few other aircraft.
The first aircraft to supercruise was the English Electric Lightning which did so in 1954
Concorde was a truley amazing aircraft nothing has come close to its perfomance and range, it could cruise at mach 2.02 for 4500 miles! compare that with new aircraft like the F22 which has about a 600mile supercruise range, The Eurofighter is even less. (but the can refuel when flying)
The SR71 could do about 2900miles
I completely agree with you, however my stats for houses in the UK are pretty accurate the average UK domestic electricity bill in 2006 was 95.75 GBP per quarter and average electricity price of about 9.9p/kWh this is mainly due to the fact that most houses are heated with gas or oil. Standard UK domestic supply available capacity is 100A at 240V.
I am interested to know why cooling towers are not used, I understand that when near the coast or large river it is far better just to dump the heat into water but when that is not available I believed they were the most efficient way to dump heat into the atmosphere, apart from the planning issues. I understand that a forced convection method would be more compact but it would consume quite a bit of power?
1GW is huge amount of power, to give people some idea, very few houses have an average load of more that about 0.5 a kW ( .5kw * 24hours * 90days * 10pence = £108 per quarter bill) most are way below that. So you are talking about the equivalent of about 2 million house supplies! Or say 1million electric bar heaters, which if you laid them out each within a square 0.5m * 0.5m you would need a field with 500m sides and it would be seriously warm!
The fundamental thing that is missing is the amount of power being generated.
You have to cool the steam down somehow, normally it looses energy by turning the generators but if that is not the case the energy needs to go somewhere.
The steam is normally re-condensed and then reused in a closed or semi closed loop depending on whether there are cooling towers. There is no way that the
cooling capacity would be able to dissipate the full load and hence the need to rapidly shut-down. This is the same for coal and gas plants as well.
The pressure is not really that great 1Atm is about 14 pounds per square inch, with a cylinder and hemispherical shape you can withstand incredible pressures, you just cannot have any weak spots.
Bicycle tyres are inflated to up to 80 pounds per square inch.
A submarine has to undergo far greater pressures, even though the air is kept at say 1 Atm internally the pressure underwater goes up by 1Atm per 10m depth so the pressure at say 915m depth would be 1316 pounds per square inch! (record manned sub with full crew 1968)
The analogue cell network had much greater separation between towers which required considerably higher power output from both the phone (several watts) and the tower.
Also with digital you can improve the SNR dramatically therefore reducing the power required.
These 2 factors are what led to digital networks requiring a lower power output from the phone combined with the greatly improved tower technology for ultra low power signal reception which used to require cooling with liquid nitrogen to get a low thermal background noise.
It should be noted that the towers for digital have to be closer together as they tend to use higher frequencies which require line of sight whereas the older 900MHz networks would go through things much better, this is one of the advantages of the 700MHz network that Google is bidding for.
Also with CAT5/6 you have to untwist some of the cable when you use connectors which affects the cable velocity due to the change in effective dielectric, whereas with fibre you really only get an attenuation as the joins are not in-line, the length of material change(glue) is small in comparison to a few tens of mm for a CAT cable plug and patch.
I do agree with you, however the accuracy of the groove is in reality less than half the equation as the needle pick-up is actually where the problem lies. The upper end of human hearing is at around 20kHz which means the needle needs to vibrate at 20,000 times a second both vertically and horizontally (stereo), it must do this with no resonance or harmonics that is within the audio range and it must faithfully represent the movement of the grove, which requires a linear voltage to be produced depending on the deflection. This is non trivial in engineering terms, therefore expensive. (If you use a laser to read the vinyl this is not an issue but you will then most probably be digitally sampling the result in any case.).
Another interesting point about vinyl is that the frequency response is different as you go from the outside grooves to the centre. Better frequency resp. at the outside considerably so in fact, it is the same with analogue tape and is also the reason that we had to wait till helical/transverse scan worked before video was practical on home systems as the tape speed was to great. The BBC recorded video to steel ribbon which ran very fast and required miles of tape.
While in principle you are correct you will still have in the region of hundreds of Amps, 100Amps would be 2.5MW which just might power a train, it is still only about 3000 horse power.
You increase the voltage to reduce the resistance losses (Power = I^2R) however you are limited by what can effectively be used in a safe manner with a pantograph.
Even super grid wires which in the UK run at 450 KV still have large currents ~ 1,000Amps which is why they are so hot ~200 deg C when under load (this is actually what limits the max load as the wires sag as they get hotter and they must not fall below the minimum safe height).
To put that into perspective 1000 Amps would be still under 0.5Gw and there is a 6GW power station in the UK, most are around 1GW.
The car computer analogy completely breaks down due to the fact that there is no single car manufacturer who supplies 95% of all cars.
If that were the case then you can bet that Sony would sue if that manufacturer chose Philips etc. instead.
In the car market you have a relatively large number of manufacturers and it is unlikely that they will all bundle the same make of CD player.
The record in question actually has nothing to do with solar power. It is purely an endurance record for longest flight time under continuous power. The Global Hawk is actually powered by a turbojet engine and normal Jet A1 fuel.
Solar powered aircraft have been quite successful for some time for instance the Pathfinder and Helios aircraft by NASA the biggest issue is to get through the night on battery power. I believe the NASA aircraft had to resort to gliding and soaring which this aircraft does not.
A purely battery aircraft would fall out of the sky in a relatively short period of time, it would probably not even get to altitude before having to glide home.
Typically solar vehicles have to start races with the energy store empty however this is very unlikely in this case as they were just doing some tests. The flight tests all seem to end when there is an issue with the aircraft or the weather is not looking good. So it may well be the case that it would not be able to stay airborne indefinitely.
You are correct, it is part of the GSM mobile specification.
If I recall correctly it is a drop test of 1.2m or 1.5m onto concrete.
The phone is allowed to come apart, e.g. the battery may detach, but it should work fine once re-assembled.
Errr no,
In the UK it is NOT legal to copy music from a CD to MP3 player or to magnetic tape or any other format full stop.
The only legal way to put MP3's onto an MP3 player is to purchase the MP3's on-line.
Interesting enough VW have already done it, see:n s_its.html
http://www.greencarcongress.com/2005/04/vw_abando
The VW Lupo is available but it only does 78.4mpg(US). Their development car did much better: 0.89 litres of diesel per 100 kilometres (264 mpg) top speed was still 75mph. but they could not make the commercial version cheaper than $25K
Can I strongly suggest that NOBODY tries this at home. Gasoline in its liquid state will always have fumes above it at room temperature, and throwing a match into it will definitely result in a very severe fire!
The match going out comment in more usually attributed to Diesel fuels, Kerosene and paraffin, which have a much higher flash point, and a higher boiling point. This means there is little vapor above the liquid and they are not likely to be ignited by a lighted match. It usually requires a wick to make fuel Oils burn e.g. a rag etc. or alternatively high temp and pressure such as in a diesel engine or gas turbine.
So please be careful!
Simple, on the way up you have air and therefore great resistance. So it is far better to go up at mach 2-3 and then when in space (no air) turn around and rocket propel yourself back towards the atmosphere, doing most of your acceleration before you hit the atmosphere. This way you have to use much less fuel and a much smaller rocket. Air resistance is a far bigger proportion of the expended energy than that of gravity.
This kind of test has been used at Woomera many times before, originally developed by the British for testing reentry systems for warheads in the 50's, the Black Arrow program. Incidentaly this was so successful that the Americans paid to extend the program so they could use the results.
Basically they stuck the test reentry unit on top of a rocket, flew it to space then used a rocket to propel it towards the ground at up to mach 12, to test the materials and telemetry.
Interestingly the British re-entry warhead design was the opposite of the USA in that it came down pointy end first whereas the US models at that time came down blunt end first. The British design was far better as it came down much faster and therefore was much more difficult to intercept.
FYI The record for air breathing aircraft (not rocket) is 85,068 feet, set in 1976 by a Lockheed SR-71 jet-powered aircraft. This was broken by the NASA helios solar powered (not air breathing) flying wing 96,500 feet in 2001
Concorde was the highest flying commercial airliner with an operational ceiling of 60,000 feet.
The SR-71(AKA blackbird had very specialised jet-engines which operated in a semi ramjet mode.
The biggest problems with a scram-jet is trying to make it a scram-jet, i.e. the airflow through the engine has to remain supersonic. The shock wave angle decreases with mach speed, at low mach numbers it is too wide. This means that you have to have an impossibly large diameter and short engine to maintain supersonic flow. When you get hypersonic (above mach 5) the shock waves get much closer to parallel to the direction of motion, hence you can have a reasonable length and diameter on your engine. The length is the critical problem, as it is necessary to combust fuel and expand the working mass (air) within the engine in order that it can do any useful work. This is very difficult as mach 5 is 1701.45 m/s so if you have a 2m engine tube you have roughly 1.2 milliseconds in which to compress, burn and expand your fuel! The rate of flame propagation in kerosene is just not high enough to get even close at this kind of scale therefore hydrogen is realistically the only fuel which will work as it has the highest flame propagation rate, even hydrogen is difficult.
Scram-jets are a very interesting technology, but there are others like air breathing rocket motors which use the liquid hydrogen to cool the intake air so that it can be compressed sufficiently to be fed into the rocket combustion chamber. This is a pretty good technique although the heat exchangers are pretty difficult to build. The have the advantage that you just bleed in more and more O2 as you leave the atmosphere until they are running in pure rocket mode.
They do have the disadvantage that they can realistically only operate with a max velocity of about mach 5.5 when air-breathing as above that you get 0 net thrust and they are fairly complex. Air breathing rockets make single stage to orbit possible without ridiculous fuel to weight ratios.
Encryption is unfortunately directly opposed to that other very important networking tool compression.
v J5sdcNrws2sRGGwgpAGS7J Y3OBriBzWvN06uB9LuGhxD /1NhB2JOaTqzqvV4I5TPqj 0Qh/zXLxAF5OMj+CcqzP8l Lqiguj4yXuRlCmwYUZg9ud 8UexU9cFhmPMP/gBAtxQkI NvEFfI5SeqVtQS6/gJ/zfD O94HtKHoEALZvrSbgXejdQ c2osoNLiqFVTjc7DRVWnNO rkEGl3JbT3p3vo1J05UFVu bqNIROM96YrGzMjWHEwsR5 SEpqCK/37DY3Xxr/qZhwi
By definition compression usually uses patterns in order to reduce the amount of data being send and also by definition encryption deliberately removes patterns as much as possible.
This fact is made even worse when the size of the data being encrypted is small as in (IM etc.) as it is necessary to pack the data with extra 'rubbish' data in order that it does not become trivial to decrypt, because it will not contain enough randomness (entropy). This is one of the issues with SSH style protocols, if one character is sent at a time over an encrypted socket then instead of trying to crack the encryption you just use time between keystroke's and the probabilities of the various keys being hit on the keyboard due to their distance apart and typing difficulty. Given a sufficiently large sample it is relatively easy, as long as the same person is typing. There are obviously methods to avoid this.
I agree that it would be great if things were built secure from the start and it will become what happens with any luck, but Internet network bandwidth is going to have to multiply before this becomes a reality. SMTP for instance would be an ideal candidate for encryption however it is bloated enough with the MIME encoding of attachments. Using PGP style plugins is great but again the message size multiplies.
VNC is an interesting one, I personally use it a great deal and mostly over VPN's to manage many disparate server systems, it would be nice if it was not necessary to have to open up the separate VPN's, however all the other traffic, filesharing etc. already use VPN's so really it is not that bad and would result in yet another firewall port to be forwared.
I mostly develope with Java which makes adding encryption to software trivially easy with the securoty libraries which are included by default. This is the case with most languages so the difficulty is not the problem, just speed and data size.
Short example using gnupg:
Message text:
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Yes they could, but He is very expensive stuff, hence why recondensing is an option, but the equipment is heavy!. This would also limit the number of trips.
You are correct in your main assumptions apart from the fact that this particular design is not designed for VTOL.
It gains approx 20% of its lift from its aerodynamic form, which obviously requires it to have forward velocity to "fly". This results in quite a large saving in volume of lifting gas.
The lifting gas issue is actually one of the biggest problems with theses airships as it is all fine when you have the load on, but what do you do when you have unloaded. You suddenly have an enormous mass requirement. Options such as compressing and condensing the He have been considered, but not practical, loading with water / earth are options but AFAIK there is no simple solution to this problem. Added to the fact that this issue gets much harder to solve as the lifting capabilities are increased. Especially since the whole idea is to be able to land in remote locations!
While I do agree with your point that 25 years is a long term investment, so is building a nuclear power station, in UK ~15 years for planning application ~10-15 years to build and ~50 year lifespan.
:).
It is very difficult to make the numbers add up in the short term for any kind of energy generation, the same argument applies to Coal fired, wind, water wheels/turbines, tidal.
The only 'quick buck' was and still is to a certain extent Gas. Quick to build, less environmental penalties (financial) than coal, relatively cheap to build, can be built on a small scale and still have good efficiency. Also gas has the great advantage of very fast startup and stop times meaning that they can cream off the top of the energy price markets as the online time is much faster. For example a typical gas turbine(100MW unit with waste heat steam turbine) start-up time to full load is around 90 mins. Compared to Coal approx 12 hours for cold start.
This is why we built a load of Gas fired plants in the UK, unfortunately we are now running out of gas and are a net importer again.
So in a real sense the best investment opportunity for short term (in power systems) is in insulation and other efficiency systems to reduce energy requirements as these typically are paid back in saving in 1 to 5 years
My personal opinion is that 25 years may seem a terrible investment but in Power generation terms that is pretty fast.
Sorry but this is simply not the case. Typical solar panels even in 1994 would have a production energy pay-back period of around 50 months.
http://www.ecotopia.com/apollo2/pvpayback.htm
More modern cells are even better, typical payback of a couple of years depending on location.
On the other had financially speaking you are talking about 25 years to recoup the cost of installation, which is why adoption has to be promoted by governments as very few people are prepared to think that far ahead!.
Well in th UK we generates around 25% of Electricity with gas, so I would say that it is a pretty huge percentage, especially given that the UK used to supply 100% of its own gas but as supplies in the North Sea reduce we are now importing around 18% of the gas we use, so the protection of energy supply becomes more difficult (threat to national security).
Nuclear power is generating around 20% coal and renewables the rest. The pecentages change dynamically due to market forces. (Gas comes on-line quicker than coal, pollutes less and costs more than coal.) Nuclear is run all the time and Coal and Gas fight it out for the rest.