Large scale hybrids

I was thinking about a large hybrid rocket, say something on par with a Falcon V, or even Falcon IV, and was wondering - would it make sense to use the oxidizer to cool the nozzle?

SpaceDev are developing large hybrid rockets to power its Dreamchaser craft.

http://www.spacedev.com/newsite/templat ... 1&subSel=3

SpaceDev's hybrids use Nitrous Oxide. It has a tendency to decompose when exposed to too much heat. I don't think you would use it has a regen coolant.

But maybe you could have a separate fluid in a closed cooling loop, using the NOX tank as a heat sink, and maintaing NOX pressure & temperature as an added bonus. (A vapour pressurized NOX tank gets colder as it empties)

DreamChaser looks to use the large scale hybrids as advocated by AMROC.

There was a proposal to use a large solid fired off the deck of a modified supertanker that was to be housed over.

This vehicle would have lower stagers that were all solid rocket fuel, with the oxygen tank underneath the payload. The lower all-fuel stages would fall away having burned out, and the second stage would ignite. Only the thrird stage had both oxidant and fuel as part of its design, IIRC.