"snidely" wrote in message
...
On Aug 4, 11:05 pm, Pat Flannery wrote:
richard schumacher wrote:
Or something as simple as thrust created by gas exhausting from the
(new) cooling system. Geez Louise. Does Falcon 1 use anything other
than explosive bolts and springs for stage separation? How many more
basic errors can they afford to re-discover?

That's their problem; they are basically rediscovering every problem
that rockets had in the mid-late 1950s.
They should have hunted down retired steely-eyed missile men who worked
on vehicles like Jupiter, Thor, Titan I, and Delta and pooled everything
they learned from those programs as how to do and not do things.
Propellant oscillation was a big problem in the early days, particularly
for Jupiter.

Per the SpaceX website:

"The problem arose due to the longer thrust decay transient of our new
Merlin 1C regeneratively cooled engine, as compared to the prior
flight that used our old Merlin 1A ablatively cooled engine. Unlike
the ablative engine, the regen engine had unburned fuel in the cooling
channels and manifold that combined with a small amount of residual
oxygen to produce a small thrust that was just enough to overcome the
stage separation pusher impulse. "

From what I can tell, stage separation events are one of the hardest things
to get right on a launch vehicle.

On another list Henry Spencer pointed out that, when they developed the
Saturns, Von Braun's team was pretty much the only team on the planet who
had real experience designing large rockets.

I talked to our senior engineer here about this (he does software today, but
spent maybe 10 years working for an aerospace company doing actual designs
for certain large satellite components). His take on this sort of thing is
that in any engineering organization, there is a certain amount of
knowledge, maybe even the majority of knowledge, that isn't captured in
formally documented analysis and design processes. Furthermore, it's not
appropriate to try to capture all of that knowledge. Every project is a bit
different, so the lessons learned vary a bit from project to project. If
the formal engineering process is too rigid, you wouldn't be able to
innovate.

Space-X is innovating while at the same time they're building up their
collective engineering knowledge for the approach they're taking. While
from the outside, it may look like they're making the same mistakes made in
the past, the details of their approach may be new enough that these really
are new mistakes which have never been made in exactly the same way.

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