Replacement Electronics in Space

[SomeGuy123]

So, having done a little bit of hobbyist level electronic construction myself (designed a few PCBs, populated them and used a homemade reflow oven), I'm wondering how you'd design electronics so you could manufacture replacements in the field.

What I think you'd have to do is to simplify the designs of all the systems in a spacecraft so that they use a limited set of parts.  A limited set of resistances, capacitances, and inductances shared in common.  Instead of thousands of separate complex ICs, make every system work with just a few types - probably something like an FPGA (possibly with an onboard board ARM processor when you need high end calculating) with just a few different sizes.

Like, the airlock controller might use a "small" FPGA, since there aren't really that many inputs and the control loop is simple.  The one that runs the radars or implements machine vision would be a "huge" FPGA, possibly several of them on one board.  You can substitute huge for small but not the other way around.  

One thing I'm not sure you can combined in parallel are power FETs.  I thought if they weren't quite balanced, all the current will go through one of them.  If you can't, you'd basically have to stock a bunch of oversized power FETs.

Anyways, the TLDR is that you want there to be less than 100 or so total unique types of parts.  That way, when something breaks, it draws from a common pool of parts.  

To actually build a replacement, there would have to be a fully robotic system.  It would have to carve the circuit board, then put globs of solder paste held by surface tension to the board, then grab parts from a feed system for all of them and place them, then move out of the way and put the board in an oven.  You'd want to fill the oven chamber with nitrogen during reflow then vent the solder fumes to space.  

I wonder how you would do the same thing for mechanical systems so you don't have to stock 10,000 separate mechanical parts.