"The basic components of E'Prime's "System of Systems" are as follows:"
" - Space Plane -- The space plane is a lifting body flight vehicle with a composite wound structure."

Problem with any plane is the protective tile system needed on the leading edge, same as the shuttles current problem.

" - Nuclear Propulsion System -- The Nuclear Propulsion System features a redesigned thermo nuclear propulsion system suitable for long transit times."

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR), which is a prototype spacecraft electric propulsion system intended for large high-power missions to Mars is being currently developed but it will need not only researchers but also cash for the program.

" - Modular Expendable Launch Vehicle -- The Modular Expendable Launch Vehicle serves as EPAC's Eagle Series of launch vehicles."

Like any new rocket design concept it takes cash if there is a poor starting point from current existing systems to be spirally developed.

" - Unified Space Transfer Module - The Unified Space Transfer Module is a derivative base line technology of the Apollo LEM, with a major design enhancement, and will provide lunar-surface-to-lunar-orbit transportation."

Basically long duration crew cabin but then again this is a new design concept in need of cash in an already cash crunched budget.

A draw back to nuclear material use for rocket s that could get us to mars alot quicker is in there use for terrorist activity.

U.N.: Uranium Mine Poses Security Threat
U.N.: Illicit Digging at Congo Uranium Mine Threatens to Put Nuclear Ore Into Terrorists' Hands

http://abcnews.go.com/wire/World/ap20040720_2681.html