On Sat, 03 Feb 2007 02:47:10 GMT, "William R Thompson"
wrote:

"Dave Kearton" wrote:

William R Thompson wrote:

One obvious question--can you find out if those
nuts are metric or SAE?

I'll ask the question and see what happens, if it's a confused mixture
of metric and imperial, does that mean it's a NASA rocket?

Only if it's from a project that NASA wanted to kill.

NASA has recently announced (see

http://science.nasa.gov/headlines/y2...metricmoon.htm

that all manned operations on the moon will use metric measurements.
This is probably NASA's way of telling the American public that
we won't return to the moon after all, not if we have to go without
our 3/8 inch socket wrenches.


In 1963 I was designing ducting for the Saturn V/S-1C.

"Everyone knows" that for the same bolt cross sectional area the
weight goes down as you increase the number of bolts. (I. E. use a lot
of small bolts for light weight.)

I used 1/4" but I was told that "our Germans" in Huntsville didn't
like that, they liked 3/8 inch. Being the kind that asks, asked.

Two reasons.

1) 3/8 is the "same" size as a 10 mm bolt and they knew how big that
was.

2) 3/8 big enough that the mechanics couldn't break them when they
ovr torqued them.

I am willing to meet people half way (sometimes). I used 5/16s
exclusively.

(I later heard that at P&W the jet engine shop rebelled and they got
the chief engineer to agree to send every designer out on the foor
where they had a rig set up with 10-56 screws, which was what everyone
wanted ot use for case flanges and stuff.

They said anyone who could torque them without wringing them off could
design with them. No one could. )

This is not the first time that NASA "metricated." And, if fact, I am
not sure that NASA has evre been any different than the US as a whole.
Congress authorized (but did not require) the use of the metric system
in the mid 1800s. That is the same as NASA always was. (One time
Congress was going to require my MOTHER to learn how much a kilo of
butter was. That was going TOO far. )

The Saturn V had 10 meter (first and second stages) tanks, for
example.

The first time NASA put out rules that said that everything had to be
expressed in "SI" I happened to have wandered off and was working on
AF programs.

When I started back on NASA proposals I was told SI was off. I asked
what happened and I was told "Isp choke.".

What?

They said that we went to NASA for a presentation and the program
manager was livid when he found that the charts did not have thruster
Isp on them. He said "Isp on ALL charts." Our guys said "Isp is not a
SI unit." NASA said "well, put it on in SI units." Our guys said "Isp
is not an SI concept." He said "No more SI on this program." And they
withdrew the everything SI rule.

When I got to the ISS that was a hot debate. I said "Show me where
this rule is written down, I want to see what it says. BUt I could
never find it. There was a "everyone knows" rule that said that "for
astronaut safety" you couldn't do anything thta made the astronauts
talk about SI units. At least in our end of the station.

When we got to talk to Russians we found out that they had about as
many opinions per person as we did. All there data had Isp in seconds
adn they didn't know exhaust velocites. Other stuff was in all sorts
of "*******ized" units. I never saw a presure in pascals, for example.
I think they mostly used "kilobar" or "kg/cm**2."

One guy was very adamant that the program should use SI and I told him
I would support him on that if they would agree to convert too.And at
the design review for the FGB I challanged them on that, and they
produced a document (the originals, actually. They were not big on
coping machines.) that gave evreything on the whole program in SI. BUt
I couldn't find anyone at the working level that knew that the
document existed or what it said.

I could go on, but I won't. I am the only person in the world
completly happy with both systems, and who thinks they are both
equally screwed up.

Henry H.










--Bill Thompson