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

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

Comment Re:IE Development Resources (Score 1) 204

I think it may be up to web developers (me, you, and the other guy) to use the newest standards that are supported by the other browsers (Opera, Firefox, Safari) and to stop supporting IE to any extent other than basic page layouts. I know its often dictated by business to support IE, and you still would be, but not to the extent that it has been. Telling people that a site will be better in a alternate browser may be a good choice in this as well.

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