In article , lid

says...



Nothing would ever get built if nothing was ever built before it had

been built.



On paper, Sabre has the characteristics required for an SSTO, and Skylon

itself isn't designed around unobtanium. So far no show stoppers have

been identified.



On paper.



The show stoppers are the flight rate and reliability of bleeding edge

technologies. In order to make a profit (and pay off development

costs), Skylon will have to fly quite often and have an extremely high

reliability (hardware losses will be very expensive for such a complex

engine/vehicle).



A more conventional approach to reusable SSTO using VTVL and plain old

liquid fueled rocket engines would be a far more sane approach when you

take into account economics. That said, even SpaceX didn't use this

approach, instead choosing to build an expendable in order to minimize

development costs and time.



There are no existing markets which would require the high flight rates

needed to justify the development costs for Sabre and Skylon. It's a

research project which belongs in Popular Science magazine.



Jeff

--

" Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry

Spencer 1/28/2011