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

You are right that I read rather too much into his comment. I think he would, as you say, disagree with the kind of sexist enslaving scenario I presented. What I was trying to say is that the sort of reasoning he presented: "accept" differences and "use" them (as opposed to, as I advocate, accept them but then largely ignore them in practice to avoid discrimination --- essentially the same as what you say), when brought to its logical conclusion, naturally and unconsciously leads to discrimination. It's just that I phrased it in a way that made me sound too extreme, sorry.

...is how I read this headline.