Xref: utzoo sci.space:15753 sci.space.shuttle:4099
Newsgroups: sci.space,sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: space news from Oct 2 AW&ST
Message-ID: <1989Nov28.060957.12226@utzoo.uucp>
Organization: U of Toronto Zoology
References: <1989Nov26.223357.27453@utzoo.uucp> <4300@helios.ee.lbl.gov>
Date: Tue, 28 Nov 89 06:09:57 GMT

In article <4300@helios.ee.lbl.gov> mikec@ux1.lbl.gov (Mike Chin) writes:
>Why is 20 kHz bad? I vaguely remember an article in Powertecnics describing
>this system, but I wasn't aware of any controversy.

The 20kHz power system was bad because it was new technology for the sake
of new technology, instead of new technology for the sake of a working
space station.  It did promise some modest improvements in weight.  In
return, it demanded that all power equipment be developed from scratch,
specially for the space station.  Not even the light bulbs would be
standard.  The obvious alternative -- use 400Hz aircraft systems --
would have been slightly heavier but vastly cheaper, because much of
the hardware could be had off the shelf and all the design issues were
fully understood.

>I was involved in a Explorer sat project where all voltages were derived
>from a 28V bus; designing the DC-DC converters was a major effort (luckily
>not done by me).

I agree that the switch to DC sounds dumb, although I haven't seen a
detailed technical explanation of the tradeoffs.  As I said, I suspect
it's a face-saving maneuver for someone.
-- 
That's not a joke, that's      |     Henry Spencer at U of Toronto Zoology
NASA.  -Nick Szabo             | uunet!attcan!utzoo!henry henry@zoo.toronto.edu