No problem. My survey of nonconventional launch technologies is up at Popular Mechanics.

I’m doing a piece for Popular Mechanics on alternatives to rockets, and I was going to cover rail guns, gas guns, space elevators, sky hooks, and perhaps the launch loop. Does anyone have any other suggestions?

[Update a while later]

Folks, when I say alternatives to rockets, I am including all vehicles that employ chemical rocket engines, including airbreathers. As I said, unconventional.

[Update a few minutes later]

OK, I’m thinking of three categories: cannons (whether EM, chemical, whatever), external energy (laser, Orion), and momentum exchange (tethers, space elevators, compression towers). I know the latter isn’t really momentum exchange, but it fits sort of. The former don’t work well for passengers, but are well suited to bulk delivery of low-cost stuff (e.g., propellants), and the latter require very high up-front capital costs, in general. With a lot of tech risk.

Congratulations to Barnaby Wainfan (who I’ve known for over three decades, having gone to school with the woman who later became his wife), on the win in the Automotive X-Prize. Also on his becoming an adjunct professor at Michigan. One thing that the article doesn’t note, but I will, is that he also played a significant role in the design of XCOR’s Lynx.

…of the future. Three of them are space related. Actually, one of them I sort of do now. But it doesn’t pay very well…