"The JP-10 is a liquid propellant called DICYCLOPENTADIENE. It is used for propulsion systems of short-range missiles, often combined with other chemicals. If you look-up in the USAF inventory, JP10 is catalogued as "Jet Propellant 10 (standard missile fuel, MIL-P-87107)", most commonly used in cruise missiles as well as short-range missiles like the "Harpoon" air-to-ship missile carried by the S3-B ASW aircraft."
From: http://www.madsci.org/posts/archives/aug2000/966261622.Ch.r.html