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

A couple points I might add:

- Until 9/30 most all of the CDs are $7 which includes a physical CD and 192K MP3 files loaded nicely and permanently into your locker.

- One poster complained you can't download the MP3 file without installing an application. That's inaccurate. You can download all the tracks individually directly from the locker - no application install required. Just click on the triangle in the flash UI and select "download".

- We do provide several different applications for your convenience all of which work on Linux as well as the other PC OSes. There's an Album Downloader which will with one click download any new purchases and load into iTunes or your fave media player. There's also Locker Sync 3.0 which will sync your entire music library from locker to PC. So lots of different options.

- Slashdotters might be interested in our API (see: http://mp3tunes.com/api). My vision is all your music goes into your personal locker and then with a click can be streamed or synced to ANY device in the world. It's a very open view of the world and of your media. We have 100,000 lockers and a great list of devices coming by this holiday season all of which talk directly to a locker. We're even having a contest to spur developers for $10,000 to come up with new music devices/interfaces: See http://mp3tunes.com/contest

-- MR

Instead they play nice and hope you do the same. I.e. they let you stream full traks for free, and ask you not to distribute them on P2P networks even if is legal.

Exactly right. Since DRM is both evil to the typical user, and frequently easily cracked, it doesn't provide real value. I'd rather trust people to be honest and support a business they like. Besides, there are much easier ways to steal music (p2p comes to mind) than to fuss over Magnatune's m3u files.

Of course they can be "easily cracked" -- they are not protected in the least, because I want Magnatune to work easily and simply on every computer, and not spend my time fighting my customer base too prevent 1% who wants to "download it all for free" -- those people would clearly never pay Magnatune for music anyhow, even if we had DRM to "protect it".

Also, because you can "'name your price" when you buy from Magnatune, if you don't think something's worth much, you don't have to pay much.

-john (who runs Magnatune.com)

Thanks for thinking of me, first. Have a great day.

I can't wait to see someone make a movie out of this fiasco, just like "Pirates of Silicon Valley" . Only it should be called "The Lone Cockblocker Who Almost Destroyed The Web" . No one else could make such outrageous claims like they invented the letter "e" and sold it to IBM.

All I can say is Tim Berners-F'n-Lee is on this now? ... hell yeah baby, lead the charge and while you're at it get that other guy that invented the information super thingy , Al what's-his-beard!

Booyah, Grandma, Booyah!