"Pat Flannery" wrote in message
dakotatelephone...

Sort of solved... they never did completely figure out the root cause of
it in the first stage, and the second stage severely manifested it at
least once - during the Apollo 13 mission in which it caused the center
J-2 to shut down just prior to it getting to the point where it could have
caused vehicle failure.
There's a discussion of it in relation to various boosters he
http://www.pwrengineering.com/articles/pogo.htm

To be fair, there really weren't enough Saturn V flights to completely work
out the bugs. As the above article states, there were several causes for
POGO type vibrations on the various Saturn V stages.

My point is that no matter how many times Ares I flies, its SRB will
*always* be generating thrust oscillations. With a liquid fueled engine,
there are always things you can tweak which could potentially reduce or
eliminate things like hard starts, combustion instabilities, and POGO.

Hybrids are the worst of both worlds. They have most of the disadvantages
of solids and liquids.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein