T-shirt air cannon?

One of the t-shirt hurling contest entrants sent some photos of their entryvia [James Gosling: on the Java road…]

For those who’ve never been to JavaOne, the hurling of t-shirts to the audience (and let’s face it: that is what keeps the conference industry alive) in ever-more-elaborate ways is a tradition. Last year, they used a trebuchet (tasteless yet compelling images of a cow flung 1/4 mile). The photo linked to above looks to me like an air cannon, which have come to dominate punkin’ chunkin’ (http://www.clubmedia.com/punkin/)