Found this:
http://www.aerospaceweb.org/design/aerospike/main.shtml
any use?

I have also been using this :
http://scientium.com/diagon_alley/commentary/bowden_essays/startrip/star...
as research for my book. No mention of the aerospike engine but some interesting stuff on other propulsion systems.

Hmmm, you got me thinking now.......

Happy cruising!

Also, less to do with nozzles and more to do with fuel type, there is a link to explain the up and coming Plasma Engine that NASA are working on to get us to Mars.

Checkout the article at Space.com

The big problem with reaching further and further out into space seems to be less to do with improving the performance of current engine technology but developing something a lot different. Burning plasma at very high temperature is a solution that could get us to Mars in a few weeks as opposed to a 10-12 months and this might help with the HUGE problem of astronaught sickness accosiated with prolonged weightlessness. Unfortunatley, that's all the Plasma Engine is good for - we'd have to develop something considerably more advanced to get to Proxima Centauri or any of the other close star systems.

Ever since the Shuttle, NASA has had some severe engine design difficulties. The positioning of the shuttle means that the LH LOX engines are only slightly more efficient than the LOX Kerosine engines of the Apollo programme (a technology starchaser industries still use by the way, usefull company to have now that skylark is defunct)

Back in 88 whilst in New York I bought a brilliant book - The Sharship Builders Guide - or something like that..I've since lost it as you do... but it is worth getting hold of if you're into such things. Best best for starship drives I remember was something called the interstellar ramjet..huge magnetic scoop out front.we're talkinf of a device that extends for 10's of kilometers....suck in the interstellar dust and blasts it out the back..no need to carry fuel..mmmm It might work.

Other than that best bet seemed to be the Project Orion pusher plate/A bomb system get you to mars in 6 weeks..they worked on this in the 60's

Biggest problem seemed to be buiding a ship out of a suitably tough enough substance to withstand the abrasion of the interstallar medium..best we've got is diamond..so

We need to develop some serious new technology and learn some new stuff/develop new theory to go anywhere. Sad isn't it. Took em 8 years to go from Gagarin to Armstong..what's happened in the last 30 years..Fuck All .. build ships not bombs..explore don't invade.

P.S.

Oh yeah..irony..whole space thing came courtesy of Adolf Hitler and the Cold War...