On Jul 12, 7:59 pm, Jeff Findley wrote:
In article ,

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 Skylo
n
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).

The engine doesn't have any more moving parts than a conventional
aircraft turbine. True, the vehicle is big, but not as heavy as a
747.

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.

How do you get it back? If you put wings on it and land, then the
structure mass eats the whole mass budget.

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.

I agree entirely with you statement. There is only one projected
market I know about where Skylon makes sense (SBSP) and even for that
market it takes something extreme for the second stage.

Power satellites really need $100/kg to GEO to make economic sense.

Keith

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