Resurrecting the Delta Clipper

> From: Marcel
> The entire cost of developing the first flight certified
> Delta Clippers was estimated at $5.06 billion, including
> production of four flight vehicles. And if it had been fully
> funded in 1991, the first fully operational orbital missions
> would have began in 1997, and we wouldn't be having this discussion.
>
> The Delta Clipper was originally designed to use liquid
> hydrogen and liquid oxygen. But there are new fuel concepts
> that could significantly lower the mass of this VTOVL
> vehicle. A 50/50 mix of liquid hydrogen and solid methane
> would require an 8% increase in additional fuel relative to
> an equal mass of liquid hydrogen which would be more than
> compensated by a 200% increase fuel density which would
> substantially reduce the bulk of the fuel tanks.

Has this technology ever been tested before? How much would it cost to
develop this new fuel technology and the engines needed to burn it safely
and reliably? What are the unforseen problems the development program would
encounter? What happens if the methane clumps together?

The Delta Clipper was and is a good idea because the concept was built
around operations, not new technology. Plug nozzel engines and carbon fibre
fuel tanks would have been nice, but the design could still work without
them. Because of that the concept could be throughly proven with a much
smaller investment (~$500M say) in the DC-Y.