"Len" wrote in message
oups.com...

I know that some think that I am rather fickle with respect to the
variety of launch vehicle concepts that I have proposed. However,
with our very limited resources, I have found that this is, by far,
the best way to make the most progress for the fewest bucks. Even
I am amazed--after 49 years of studying launch vehicle concepts
--how much can be done on the conceptual system design level, as
opposed to "space technology development."

From what I can gather the viability of a design is actually fairly
insensitive to specific technical details. TSTO, SSTO, air launch,
etcetera, they should all ultimately be capable of less than $100/kg to
LEO.

As my father says repeatedly, it is not the design but the development
process that is critical, all roads lead to Rome. The development
process is a learning process. Refining of the conceptual model from
which the design is derived is everything. This wants to follow the
most economical path. Generally the ROI clock really starts ticking
once metal gets bent. It costs little and is generally beneficial to
leave a design percolating until then.

Pete.