PIC's in space

[mister_e]

IcePaks and Vanilla Ice ... the dairy product... not the rapper

[Charles Linquis]

I can guarantee that some of my hardware designs - and code are orbiting the earth. There are many challenges. For example: Go to DigiKey and
buy a Panasonic lithium cell. Ask them if the cell will work in a vacuum. They will tell you they don't know. If you call Panasonic, they will also tell you
they don't know.
You will find the same thing with most capacitors. You may need a 450uF @ 50V. You can't use electrolytics because they generally can't take vacuum.
Tantalums generally have an MTBF (Mean Time Between Failures) that is too low (at least according to MIL-HDBK 217). The answer is 21 X 22uF ceramic caps
in parallel. Pricey!

And testing isn't always the answer. You can only test a few. What if there is a 10% failure rate of a part when subjected to 5 years of vacuum, and you
have 2 parts (because of price or availability) that you can test for 1 month at most (because of delivery schedules)? Now it isn't just electronics, it is statistics. And what if a part fails during testing? You start all over.

A full-blown military testing sequence (MIL-810, MIL-461, DO-160 etc.) generally costs $50K - $75K. This is the cost for unit #1. If the military wants 4 pieces
of something that doesn't already exist, then testing adds at least $13K to each one.

People are amazed when they find the military spends $500 for a hammer or some exorbitant amount for a part and they get outraged and want their congressman to take action.
I assure you, not all of that is graft and/or corruption.

[rsocor01]

People are amazed when they find the military spends $500 for a hammer or some exorbitant amount for a part and they get outraged and want their congressman to take action.
I assure you, not all of that is graft and/or corruption.

You can probably find that same hammer or a similar one at HomeDepot for $20. The contractors don't necessarily follow the specs all the time. I have seen over the years many overpriced products and projects been sold to the government.

Robert

[Charles Linquis]

I'm not denying that you can find the same one at Home Depot for $20. My point is that the military probably will not buy that hammer from Home Depot without a test report stating that it meets certain requirements.
I see all sorts of requirements, such as NO PVC (Polyvinyl Chloride) - a common plastic used to coat lots of things, like hammer handles and wire insulation.
PVC can't be used because if it is in a fire, it releases toxic fumes, which can kill a pilot or a submariner.

Also, we sometimes have to prove (by analysis or testing) that no material used in our product is destroyed by a variety of chemicals - like jet fuel, bunker fuel, sea water or engine oil.

And often, we are must test to prove that the metals used will not corrode when subjected to 14 days of high-temperature salt-fog spray.
We can't perform any of these tests ourselves, the tests must be performed by a qualified third-party testing lab that has *proved* they are qualified to test to a given MIL spec.

Home Depot's hammers may, in fact, meet all the requirements. But will they provide test reports to prove it? I serously doubt it.

[Ioannis]

Still, how do you cool a 7805 in space??? I insist on this

Ioannis

[rsocor01]

Still, how do you cool a 7805 in space??? I insist on this

Ioannis

A quick search in google... Radiators that emit heat as IR.

Telecommunication satellites are all based on the same overall design using a 3 axis stabilization process, in which the North and South panels act as radiators and so ensure heat removal.

http://www.electronics-cooling.com/1...e-electronics/

[Charles Linquis]

A lot of the thermal analysis tools we use (FlowWorks, for example) allows you to assign materials and heat sources (in Watts, BTUs, or other units). You build your mechanical model, assign all heat sources (7805's or PICs or whatever), tell it what the conductivity and "emissivity" rating of the materials and surfaces (flat black, shiny black, titanium , aluminum alloy, etc), and tell the program it must use "radiation only", and it will tell you what temperature it will stabilize at. Sometimes you have to add to radiant sources - a large heater called "the sun" and a smaller one called "the earth".

It is totally amazing what FEA and thermal analysis tools can do these days.

[Archangel]

I'm not denying that you can find the same one at Home Depot for $20. My point is that the military probably will not buy that hammer from Home Depot without a test report stating that it meets certain requirements.
I see all sorts of requirements, such as NO PVC (Polyvinyl Chloride) - a common plastic used to coat lots of things, like hammer handles and wire insulation.
PVC can't be used because if it is in a fire, it releases toxic fumes, which can kill a pilot or a submariner.

Also, we sometimes have to prove (by analysis or testing) that no material used in our product is destroyed by a variety of chemicals - like jet fuel, bunker fuel, sea water or engine oil.

And often, we are must test to prove that the metals used will not corrode when subjected to 14 days of high-temperature salt-fog spray.
We can't perform any of these tests ourselves, the tests must be performed by a qualified third-party testing lab that has *proved* they are qualified to test to a given MIL spec.

Home Depot's hammers may, in fact, meet all the requirements. But will they provide test reports to prove it? I serously doubt it.

I can verify the validity of Charles' statements as I do my work inside a test lab, as for the $20 hammer, I am sure it would work in " most " of the Govt.'s needs, the problem as I see it is in the Mil. Spec.'s usage. Typically they have an Equipment Specialist who determines "Which" mil spec. gets chosen for that hammer. If He chooses the wrong one then "Doggies and Marines" end up carrying $6000 hammers into battle instead of the $20 ones. It IS an area which MUST have some changes, Product engineers MUST be allowed to question the buyers, and as taxpayers they should.

[SteveB]

...Product engineers MUST be allowed to question the buyers, and as taxpayers they should.

<cynicism> But will the managers/VPs/Board allow it? Where is the profit in that? </cynicism>

[Archangel]

<cynicism> But will the managers/VPs/Board allow it? Where is the profit in that? </cynicism>

Sometimes. Probably not in the case of the hammer, an example, that comes to mind, while building a fixture, OEMs engineer spending OPM, specs an threaded insert which our cost was $600 ea in qty 100. No benefit in this unusual insert. Boss told the buyer, buyer told the lead engineer and inserts got changed.

[rsocor01]

I can verify the validity of Charles' statements as I do my work inside a test lab, as for the $20 hammer, I am sure it would work in " most " of the Govt.'s needs, the problem as I see it is in the Mil. Spec.'s usage.

I know he is right. Like you say the problem is in the spec's usage and also in all the bureaucracy involved in the process.

[Charles Linquis]

I know that everyone really loves to believe in conspiracies, but there isn't one. They guy ordering the hammer fills out a form. That form may or may not request that he state the specs it must adhere to. If is used in space, he checks a certain number of boxes. If is used around airplanes and fuel, he may check another (after all - the hammer may have to be made from a metal that doesn't produce sparks when it hits something hard. There are a very large number of "boxes". He doesn't know how much the hammer costs, or what the difference in cost really is if he checks, or doesn't check box #39. The guy just needs a certain type of hammer. The request goes to the buyer, who knows little or nothing about specs. So the buyer sends out the RFQ (Request For Quote) to a variety of hammer suppliers. The suppliers see that the hammer must be tested to pass a particular test suite and and they submit their bids. They aren't colluding, they just realize that they are going to have to send their hammer out for $20K testing, and price their hammer accordingly.
The buyer gets the lowest bid and buys the hammer from the lowest cost (and approved) supplier. The original guy gets his $500 hammer (or $1000 hammer, or whatever). He is happy. He DOES NOT KNOW (or care) how much that hammer cost. Even if he did, what other person in his organization would listen? If anyone buys a $20 hammer at Home Depot and it fails when used for a particular application in Afghanistan, he loses - big time, maybe it somehow results in the death of a soldier. If he goes through accepted channels, chose the correct "boxes" (explained above), and gets a $500 hammer and it fails in Afghanistan, it is not his fault.

Which would you choose, the $20 hammer or the $500 hammer? And who is the "evil" money-grubbing person here?