Juan:
There is another issue that comes to mind regarding “specialized”
modules. In a program such as Eagle we will need to create an acceptable module
design that is useful for many applications in the mission and then turn on the
fabrication machinery for producing these long before the electronic forces are
ready to populate them for flight. On P3D in 1992-3 we gambled and manufactured
a very many module parts, expecting that we would have some spares left over –
wrong! Even with this quite large quantity of parts (and at that time there was
criticism that we were making too many) we ran out before flight and had to
make some more.
Fabricating module parts for this program is a guessing game, with
some estimates of needing to construct up to 80 sets of parts, and that may not
be enough. You can do the detailed program mathematics and come up with some
number and I will be willing to bet that you end up on the wrong side of that
guess. It’s a dicey game.
The lesson in this is that we must create a generic module design
and hardware that can be adapted for many different assignments in the spacecraft.
Save for your specialized need, we have no indication of any other specialized
module needs. This is why I prefer to adapt a generic module to your needs with
the added heat sinks, rather than make just a specially machined device just
for your needs. And if we do, we will probably not have enough of them. This is
why I prefer to have a generic module design and then carefully adapt it as
required for specialized module needs. We will be flying more than just the U
receiver!.
’73,
From: [email protected] [mailto:[email protected]] On Behalf Of Juan
Rivera
Sent: Monday, 15 October, 2007 15.38
To: Dick Jansson-rr
Cc: Bob Davis; AMSAT Eagle
Subject: Re: [eagle] Revised Module Suggestion
Dick,
That looks nice! It appears to solve the issue of
getting that front panel at exactly 90 degrees to the baseplate and also
increases the stiffness of the baseplate. Increasing the useful front
panel space also eases the problem of working around the CAN-Do PCB with all of
the necessary I/O connectors.
Would it be possible to customize the baseplate for the few
modules that draw high power? It would be nice to machine the baseplate
and heat sinks as one chunk of metal instead of the existing method of having
several individual heat sink pieces. I would like to see the PCB laying
flat on top of the baseplate with milled cutouts to accommodate any devices
attached to the bottom side. In a perfect world there would be no
components on the bottom and the PCB would make contact with the baseplate
across the entire surface. Another possibility that might be worth
considering would be the ability to include "U" shaped heat sinks
that would bridge over the top side of hot components and attach to the
baseplate through holes cut into the PCB on either side of the component.
Thermal gap filler could allow room for CTE mismatches so that the device isn't
crushed.
73, Juan - WA6HTP