[eagle] Re: Revised Module Suggestion

Chuck Green greencl at mindspring.com
Tue Oct 16 08:15:18 PDT 2007

Hi Dick,

When considering special needs, don't forget that the IHU has already 
been designed and will need a box to accommodate it. You did this once, 
but with the new box designs, it may need to be done again.


Dick Jansson-rr wrote:
> 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,
> Dick Jansson, KD1K
> kd1k at amsat.org <mailto:kd1k at amsat.org>
> kd1k at arrl.net <mailto:kd1k at arrl.net>
> *From:* wa6htp at gmail.com [mailto:wa6htp at gmail.com] *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
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