I saw this while looking at B47 stuff. Called JATO (jet assisted take off) or more recently RATO (rocket assisted take off). From what I found out, when planes are heavily loaded and have short runways or are taking off in a hot and high elevation, they use these to give them an extra kick in the rear. I thought it was absolutely incredible.

http-~~-//www.youtube.com/watch?v=Nw2bAJGgCZI&feature=related

Then theres this thing which is just nuts.

http-~~-//www.youtube.com/watch?NR=1&v=WKCl3lfAx1Q

Heres a pic of a B47 using them.

--- Update to the previous post...

Just found this, my new boat.

http-~~-//www.youtube.com/watch?v=WlEt0bCeTy8&feature=related

That is wild... Wow!

my son flys as a flight engineer on C130's and said it is a real kick in the pants on take off. a C130 doesnt need much room for take off anyway, and they can fly them in some pretty crazy places.

Wow thats pretty cool, and that shot of the B47 is awesome!-Jordan-