Use of non military/space grade IC's in space
skylight
Posts: 1,915
I can't remember where I read this but was quite shocked to see that due to increasing costs that there is talk that off the shelf devices could shortly be finding themselves in spacecraft.
Now does this mean that the rigorous testing of old is about to be stopped? I'm not saying that IC's etc are not reliable if specced correctly but that's on earth not in the hostile environment of space and lives can be at stake because of failure.
Just wondered what others views are on the subject, is every human endevour now going to be based on cost over safety?
Found the news item ( http://www.bbc.co.uk/news/science-environment-12253228 ) and I may be being hasty in thinking lives may be at risk but in the future maybe accountants will drive what spacecraft utilise?
Now does this mean that the rigorous testing of old is about to be stopped? I'm not saying that IC's etc are not reliable if specced correctly but that's on earth not in the hostile environment of space and lives can be at stake because of failure.
Just wondered what others views are on the subject, is every human endevour now going to be based on cost over safety?
Found the news item ( http://www.bbc.co.uk/news/science-environment-12253228 ) and I may be being hasty in thinking lives may be at risk but in the future maybe accountants will drive what spacecraft utilise?
Comments
Now, I have no idea about space hardened processors etc, I've just imagined they must be getting harder to find as they get smaller and smaller and less able to withstand cosmic ray strikes. But perhaps they are small enough and power frugal enough that reliability can be obtained from multiple redundant systems. Rather than spending a lot of money building bigger, slower, space hardened chips.
Early on in the space race, we didn't necessarily understand chip failure mechanisms. Over the years, failure mechanisms have become better understood and much of what we've learned has become common-place in commercial IC development and production. Witness Parallax's progression from commercial grade parts in their Stamp modules to industrial grade parts. The Propeller has already been characterized for military temperature range use.
Radiation hardening is another issue. That requires special materials, but it also limits designs to older parts, partly because newer parts (mostly memories) are inherently less radiation resistant than older parts because of thinner oxide layers, lower supply voltages and currents, etc. To achieve radiation hardening, systems have to be designed with redundancy and error recovery and that can be done with fewer radiation hardened parts.
Keep in mind also that increased cost doesn't necessarily mean increased reliability. Radiation hardened parts are not fail-proof. They just hold up on average longer than non-hardened parts. You still have to design the systems for failures.
The internet was a military application but we now use it. It has been years from when I heard this but I believe the 68000 was designed for space because they needed chips that could survive radiation and the technology was later sold for civilian use. If you research AMD or Intel along with other chipmakers, some of these companies received a lot of government contracts and which is why the 8088 or 8086 has become the monster that it is today.
are used in aerospace and military applications. Mil-spec and
rad-hard parts are not always required and when used add a lot
of cost to projects.
Here is an interesting blurb about this from "COTS Journal" .."The Journal of
Military Electronics & Computing"
COTS (kots), n. 1. Commercial off-the-shelf. Ter-
minology popularized in 1994 within U.S. DoD by
SECDEF Wm. Perry’s “Perry Memo” that changed
military industry purchasing and design guidelines,
making Mil-Specs acceptable only by waiver. COTS
is generally defined for technology, goods and services
as: a) using commercial business practices and specif-
cations, b) not developed under government funding,
c) offered for sale to the general market, d) still must
meet the program ORD. 2. Commercial business
practices include the accepted practice of customer-
paid minor modification to standard COTS products
to meet the customer’s unique requirements.
—Ant. When applied to the procurement of
electronics for the U.S. Military, COTS is a pro-
curement philosophy and does not imply commer-
cial, office environment or any other durability grade.
E.g., rad-hard components designed and offered for sale
to the general market are COTS if they were developed
by the company and not under government funding.
Link:
http://www.klabs.org/DEI/Processor/PowerPC/rad750/papers/spacewire_con_2007.pdf
The difference was in the testing and burn-in performed on the top grade assemblies, e.g. Commercial TACAS
collision-avoidance transponders were thoroughly and repeatedly tested at -40 to 85°C IIRC, with extended burn-in
times.
I would actually feel much safer flying with equipment built/tested in the above manner than something simply built with mil-spec
parts and shipped, because it is tested as a unit.
The truth is that any mission critical military and aerospace chips are likely never mentioned on the internet, may use completely different semi-conductor technology that is faster, and would land you in jail as a spy just for having in your possession.
We only get the mundane stuff, like the motor oil. And it is decent quality. The world would be a hellish place without somebody doing quality control and quality assurance.
What's actually in space.. you will never know. If you find out, they will shoot you. Take the Iridium Satellite System for instance....
He has told me things that would get us both jailed prolly, lol..and I can say with confidence that we have lost much over the years as we gain in other areas.
I will keep it simple like that.
the Rohs compliant solder -without lead- has the nasty habit of growing conductive crystalline protrusions over apparently not a lot of time...
I bet anything the military would use in high danger / high liability situations IS NOT Rohs compliant, lol
Great writeup: http://www.electricity-today.com/et/oct97/mars.html
Is there any data on how long this metal migration takes to kill parts verses temperature and/or current. It's unnerving to think that my big stash of 74 chips and assorted old microprocessors and RAMs/ROMs is slowly dying of metal migration even without being used. They are already decades old:(
Here the biggie though:
How many years are the Propellers gauged for. At what temperatures/currents?
"How many years are the Propellers gauged for. At what temperatures/currents?" ... The standard for TSMC's DRC rules are set at 10 years /125C which is what we used. This number though is analogous to a Power rating and does NOT necessarily mean that after 10 years they will stop working. Keep in mind also, that this value is more than likely derated a fair amount also. Usually you notice the metal migration failure in memories, since the DRC rules that apply to memory are generally 'tighter' than other parts of the design....AND that memories will usually experience more "electrical exercise" that other parts of the design.
Here is a quote from one of the Design sheets I have:
"These rules for aluminum alloy guarantee 10 years use life, with less than 0.01% cumulative failure."
You mean erco is causing this!
I am not sure why it would be so sensitive. My guess is the sensitive / finicky PLL circuitry on the Propeller that is the culprit in this case that may otherwise not exist on a PIC. I would think shielding would improve your results.
these were not 2MeV protons that could be shielded quite easily but 2GeV particles. Shielding would be ... cumbersome. Anyway these are the cosmic ray particles one would expect to be most effective on bringing a circuit down as shielding is not really possible and they are still quite common in space (of course not with this flux rate). The circuit board is still active from the treatment (~2µSv/h) and we will have to wait for it to cool down before looking at the components. The result is - to say the least - quite disappointing, we had hoped that the prop would have some resilience of at least a few minutes before going into whatever event. The charge injection into the whole chip is of the order of 10^8 Protons or ~16pC before failure after ~a second, so I suspect that something else is happening here. Maybe an inner photoeffect of secondary particles/gamma rays in the substrate that ignite some parasitic thyristors. Unfortunately it is not easy to pinpoint the location where exactly the event is taking place.
There is some protection from solar winds, particularly on the near side where the tail of the magnetosphere offers protection for a few days each month. And also when it's dark, obviously. But yeah, side on is going to get the full brunt twice a month.
I'm guessing geosynchronous orbit has limited continuous protection by the magnetosphere.
PS: I found this interesting titbit about the moon crossing earth's tail: "During the crossing, the moon comes in contact with a gigantic plasma sheet of hot charged particles trapped in the tail. The lightest and most mobile of these particles, electrons, pepper the moons surface and give the moon a negative charge.
On the moons dayside this effect is counteracted to a degree by sunlight: UV photons knock electrons back off the surface, keeping the build-up of charge at relatively low levels. But on the nightside, in the cold lunar dark, electrons accumulate and surface voltages can climb to hundreds or thousands of volts.
Imagine what it feels like to be a sock pulled crackling from a dryer. Astronauts on the moon during a magnetotail crossing might be able to tell you. Walking across the dusty charged-up lunar terrain, the astronauts themselves would gather a load of excess charge. Touching another astronaut, a doorknob, a piece of sensitive electronics -- any of these simple actions could produce an unwelcome discharge. Proper grounding is strongly recommended, says Stubbs."