Plasma Reactor Engine

DigTech co.'s Research & Development Staff unveils what they've been working for months. DigTech Developted its first prototype of a direct Helium-Deuterium fusion reactor which has the optional feature of a Liquid Oxigen afterburner.
The new reactor is designed specially for interplanetary spaceflight, but it's able to atmospheric flight using fly-by-wire built-in systems. The Atmospheric flight performance in a theorical blunt spacecraft model is expected to be greater than the Mark IV Engine used in Spacetech's DeltaGliderIV. It has got an ISP value similar to NASA's Saturn V rocket's engine, but more redundant and therefore less likely to fail plus its fusion process produces Water and Lithium that may be collected for crew's resource needs.
The downfall of this new reactor is that it weights about 11 tons and therefore it will only be used by a secret spacecraft codenamed "Crane" that's being constructed by Alrik (from the Orbiter-Forum Community), yet.

Picture of the Reactor Engine Prototype