PIC's in space

[Ioannis]

I wonder how are the electronics cooled in space. Even the slight temp rise has to be taken into account since there is no heat dissipation in space.

IR maybe?

Ioannis

[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/

[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>

[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.