---------- Forwarded message ----------
Date: Wed, 7 Mar 2001 17:48:45 -0600 (CST)
From: Gene Mechtly <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED], [EMAIL PROTECTED]
Subject: SI at NASA
Dear Paul,
After our telephone conversation yesterday, I studied the
Reply of NASA's Chief Engineer (W. Brian Keegan) to the Inspector
General's Assessment Report (G-00-021) in detail.
It is clear that Mr. Keegan makes little distinction between
metrication of flight performance variables (software) and metrication
of hardware objects. In fact, his primary concern appears to be the high
cost of *replacing* items of hardware by items that are procured or
redesigned to original SI specifications. Of course, costs of total
replacements would be prohibitive! That is *not* a reasonable intent of
metrication until new generations of hardware systems evolve.
Recommendation 1 of the Assessment calls for the Chief Engineer to
"...develop a new approach for the Agency's conversion to SI."
The present approach is vertical; SI, or not-SI (by waivers), for
each program or project, with recognition of hybrid mixes in some programs.
Here is a proposal for a new approach: *Metricate horizontally*
across program, project, and Center boundaries. Begin with flight
performance variables about which there is *no* cost penalty, great
promise of uniformity, and little potential for dispute.
For example, the SI Unit of acceleration is meter per second
squared (m/s^2). It shall be used. Waivers shall be difficult.
SI prefixes may be applied to scale numerical values up or down. e.g.
km/s^2 is an accepted multiple in SI.
Another example, the SI Unit of pressure is the pascal (Pa).
It shall be used. Waivers shall be difficult. Again, SI prefixes
may be applied. e.g. kPa, and MPa are accepted multiples in SI.
Replacement of non-millimeter hardware (e.g. fasteners, pipes,
tubes, connectors) shall *not be required* until new and improved
millimeter designs are widely adopted in private sector industry.
However, reasonable efforts shall be made to write millimeter
specifications for existing standard hardware items.
Please submit this proposal to the NASA Chief Engineer.
Gene Mechtly.
