[xi] History is written and read for several reasons, and the
NASA history program serves multiple purposes. John Sloop's
history of liquid hydrogen as a fuel illustrates the most
practical of those purposes: it is useful to current and future
managers of high technology. Of course history does not repeat
itself-there are too many variables. But similar situations
often have similar results, and thoughtful study of the
management of technology in the past can sometimes help us to
recognize pitfalls in the present pitfalls that managers can
then act to avoid. We may also find ways to make desired
outcomes more likely. In any event, study of history lets us see
current problems more clearly. For example, notice in this book
how many times something had to be rediscovered. This has been a
real problem, and a costly one, in the recent past; it is apt to
get worse in the future. Are we in NASA doing all we reasonably
can to manage this problem-not just making new technology
available to industry, not just trying t