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Comment: Re:oh good... let's all bury our heads... (Score 4, Insightful) 270

by Obasan (#24541983) Attached to: Massachusetts Sues to Halt Defcon Subway Hacking Talk

I don't agree with the Massachusetts decision to attempt to stifle the presentation. This was foolish on a number of levels, not the least of which was it will probably help draw far more attention to the hack than it otherwise would have obtained.

That being said, it is perfectly reasonable to not "fix" a system if the cost of the fix is more than the cost of fare evasion. Look - in many cities "evading the fare" is as simple as getting on the bus and choosing not to pay. These systems depend on users for the most part obeying an honor system with periodic random enforcement by transit personnel checking for passes / ticket validation. This is done across Europe and in a number of cities in Canada (not sure about the USA). Why do this? For starters most people aren't jerks, and pay their fares. Second, there will ALWAYS be a way to evade a fare system without massive (expensive) enforcement that would cost far more than the added fare revenue. You would not get on one of the systems where there is no ticket check on entry and then crow about how you evaded the system (or you wouldn't without looking like a complete dork).

It's worth noting that this injunction is not analogous to software companies hiding known exploits in their systems where their customers may suffer the consequences. Boston IS the end user.

Moving people from place to place should always be the highest priority of transit authorities. In general most people are good about paying their fares. Dealing with smalltime one-off thieves is a waste of their resources.

If you use the system without paying, you are a thief and you are doing a tremendous disservice to your fellow citizens.

Comment: Re:Iron Man's Suit Defies Physics -- Mostly (Score 2, Interesting) 279

by John Carmack (#23266718) Attached to: The Science of Iron Man
Hydrogen peroxide powered rocket packs fly for around 30 seconds, because they have a specific impulse of around 125, meaning that one pound of propellant can make 125 pound-seconds of thrust, meaning that it takes about two pounds of propellant for every second you are in the air. Mass ratios are low for anything strapped to a human, so the exponential nature of the rocket equation can be safely ignored.

A pretty hot (both literally and figuratively) bipropellant rocket could manage about twice the specific impulse, and you could carry somewhat heavier tanks, but two minutes of flight on a rocket pack is probably about the upper limit with conventional propellants.

However, an actual jet pack that used atmospheric oxygen could have an Isp ten times higher, allowing theoretical flights of fifteen minutes or so. Here, it really is a matter of technical development, since jet engines have thrust to weight ratios too low to make it practical. There is movement on this technical front, but it will still take a while.

John Carmack
Businesses

+ - Business Week shows offshoring bad for the economy->

Submitted by
Obasan
Obasan writes "A 'gaping flaw' in the way economic numbers are computed may be the cause of a disconnect between GDP growth claims and actual growth, especially in terms of real wages, a phenomenon many of us are at least anecdotally familiar with. Business week calls this gap "phantom-GDP", gains in reported GDP that cannot be correlated with domestic production."
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