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

• If we're not coming up with something new and innovative we're stuck making outlook clones. People don't like writing software like that.

What are you talking about?? Writing clones of commercial software is the prime directive of open source! I'm going to go out on a limb and say that actually there are quite a lot of people who like nothing more than doing exactly that.

I have an NEC ND-1100A drive (DVD+R/RW) that I bought for under $200. I bought a stack of 100 Ritek 2.4x DVD+Rs for about $1.30 per disc, which seemed very reasonable to me. I remember when CD-Rs were over a dollar a disc, too, and at the time I thought that was worth it for copying^H^H^H^H^H^H^Hbacking up music and games.

I've copied^H^H^H^H^H^Hbacked up 35 DVDs since I got the drive. I have a Pioneer set-top player that I'd guess is 4 years old anyway, and a Playstation 2, and both play the movies without a hitch. I've brought them to a friend's place and they played in his player as well, though I didn't note the model. I'm not sure where the impression comes from that DVD+Rs don't work in anything and nobody uses them. I didn't read the article, but before I bought my drive I did what research I could, and there was a site I found that listed hundreds of set top players and the vast majority of them played DVD+Rs fine... if there was any problem, it was with +RW, but -RW wasn't exactly universal either. And why would anybody want to burn DVD movies onto DVD+RW/DVD-RW anyway? Do you burn movies, watch them, delete them, and then record onto the DVD again as if it were a VHS tape? I mean, you're already saving $19-some dollars if you're swiping a buddy's copy to make the disc, why not pony up the extra dollar and change and have copies of all of them? (This is a hypothetical question, as everyone on Slashdot knows that nobody abuses fair use rights.)

I've used my burner for legitimate reasons too. I have ~75gb of legal mp3s that I made from my own cds (I immediately rip and encode every cd I buy and then put the cd in one of my cd books at home. A couple years ago when I was getting ready to come to college, I didn't want to risk someone walking into my dorm room and walking out with 600+ cds just by lifting my three cd books, so I didn't bring them with me) and that I don't share on Kazaa or anything similar, and I would be forced to commit suicide if I were to boot to an unrecoverable fsck error, or my drive were to set fire (did I mention I have four IBM drives? I am a master hardware buyer), or any number of other things were to happen and I was caught without backups.

And as appealing as burning 110+ cds sounds... no thanks. Though I must admit, I anxiously await the day where blank DVD+R/DVD-R (whichever format wins out, I don't care) discs can be had for $.30 a piece in retail stores.