Resurrecting the Delta Clipper

Here's an abstract of the cryogenic propellant concept:

Cryogenic propellants and method for producing cryogenic propellants
Document Type and Number:
United States Patent 5705771

Abstract:
An improved cryogenic propellant which can be utilized as an improved rocket fuel, hypersonic vehicle fuel, aircraft fuel, explosive, or coolant is described.

The improved cryogenic propellant is illustrated by a mixture of liquid hydrogen and solid methane. As an example, an approximate 50/50 mixture by weight of liquid hydrogen and solid methane has a mixture density approximately 2.0 times that of liquid hydrogen alone. This increase in density is partially offset by a loss in ISP of about 8 percent, compared to that of liquid hydrogen alone, with oxygen. Broadly speaking, more of the improved fuel must be carried for a given mission to compensate for the loss in ISP. However, this weight penalty is offset by the 200 percent increase in density. Increased fuel density reduces fuel tank weight and drag.

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A full manuscript of the fuel patent can be found at:

http://www.freepatentsonline.com/5705771.html