In article ,
Martin Eastburn wrote:

NASA didn't grind the mirror - Another very respected company did -
I want to say Perkin-Elmer - who had made others for years.

It was a simple grinding tech goof that wasn't caught locally and not at
NASA upon reception. The precision had to be out of the world for that
lens, but we do them much larger and better now.

The problem was not a grinding error per se, it was that the fancy null
corrector was made wrong. If I recall, one of the lens spacers was one
millimeter too long or too short, and the mirror was ground to match
the fancy null corrector.

Joe Gwinn



Martin

On 3/24/2013 6:55 PM, Joe Gwinn wrote:
In article , Larry Jaques
wrote:

On Sun, 24 Mar 2013 14:50:07 -0400, Joe Gwinn
wrote:

I just read the 18 March 2013 issue of Aviation Week. On pages 28-29,
there are two articles on the 787 battery investigation results and
proposed fixes.

What caught my eye, and apparently that of the investigators, was that
there was never an all-up test of the 787 battery charging system with
the actual Yuasa-made production battery. They were tested
independently, but there is no record of them ever being tested
together.

So, they're doing things like our CONgress critters do now, eh?
deep sigh "We need to pass this bill so we can see what's in it."
said Nancy Pugnosy.

Well, the individual companies (for battery and for charger) no doubt
satisfied their respective contracts. It's Boeing that should have
insisted of a full-up test, and it's the FAA that should also have
insisted that Boeing insist.

This reminds me more of the NASA screwup that caused the Hubble to be
nearsighted - there was never a full-up optical test on the ground.
The problem was that they had two null-corrector results. The big
fancy null corrector said the optics were perfect, while the simple
crosscheck corrector said the optics were off. Perkin-Elmer, the
optics house that made the mirrors, offered to do a full up test for
something like $20 million, but NASA declined, and chose to believe the
complex null corrector. Oops.

[snip]

Joe Gwinn