There may have been engineering challenges in the '50's, but
technology and construction techniques have improved significantly
since then.

It's the unknown unknowns that get you. Materials and construction
techniques aren't the problem. Things like injector designs don't
necessarily scale up easily when you consider problems like
combustion instability.

Even if things look like they're going smoothly, you still want to
have a robust, somewhat lengthy, ground test period to make sure
you're not missing something. This takes time and money even if you
don't run into significant problems.

You mean the computer simulation isn't accurate? Inconceivable!

rick jones
--
The glass is neither half-empty nor half-full. The glass has a leak.
The real question is "Can it be patched?"
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...