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High-Temp Electronics For Venus Exploration, recent advances
dtolman
post Jun 18 2013, 02:30 PM
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I think you're being pessimistic. The state of the art for commercial tech is moving to a 500C package. Automotive want it, and drillers need it - with immediate potential sales in the 10K-100K annual range, and potentially in the Millions if it becomes standard in engines, there's enough sales carrot to push research. NASA can wait, and in 5-10 years use COTS equipment as the basis of a Venusian lander.

The question of pushing existing tech into the 500C range is interesting - found this abstract that claims they were able to get existing Silicon-on-Insulator EEPROM cells working at up to 450C in a lab, well beyond the ~200C they are rated for now. That bodes well for getting memory working at venusian ranges in the near-future, rather the nebulous "5-10 years from now" that never arrives.

As for existing tech - there definitely isn't anything outside of a lab that will work over long durations, but short duration missions are possible now with existing tech from what I can see. For example, here is an existing pressure/temperature sensor package that is rated at 4-5 hours at 400C. While the sensors in this particular unit may be of limited interest*, my point is that they can get modern electronics to last long enough to return useful data from the upper elevations of the highlands for a few hours - now.

EDIT * - thinking about it, measuring temp/pressure/motion at a lot of locations would probably be useful. Wonder how expensive it would be to equip borehole sensor packages with a transmitter and a parachute, and dump a bunch across the highlands of Venus? Gotta be cheaper than doing it from scratch...
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Robotbeat
post Jun 18 2013, 03:36 PM
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QUOTE (dtolman @ Jun 18 2013, 08:30 AM) *
...

EDIT * - thinking about it, measuring temp/pressure/motion at a lot of locations would probably be useful. Wonder how expensive it would be to equip borehole sensor packages with a transmitter and a parachute, and dump a bunch across the highlands of Venus? Gotta be cheaper than doing it from scratch...

I've thought of the same thing... The issue is partially that if you /actually/ press the borehole guys about operation at 460C, they dither a bit. They aren't nearly so optimistic as their websites claim.

I hope you're right about me being pessimistic
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dtolman
post Jun 18 2013, 06:36 PM
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Its a good thing that Ishtar Terra has temperatures that drop as...low... as ~380 (Maxwell Mons - +11km above surface), and averages "only" 420 or so at its average height of ~+5km.
Gotta start somewhere on Venus, and Maxwell Mons and the other high peaks around Ishtar Terra might be a good place to start with existing tech.

EDIT: Another project for ~450 C operation, through the DoE:
http://www4.eere.energy.gov/geothermal/projects?filter[field_project_technology][0]=%2214%22
This presentation in particular (from last year - final results in the forthcoming 2013 report) indicates they were able to get data back from a 450C environment (vacuum flasked electronics).
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Robotbeat
post Jun 18 2013, 07:22 PM
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QUOTE (dtolman @ Jun 17 2013, 03:13 PM) *
...
EDIT: and I now see this note by Raytheon that they are working on a SiC based CMOS rated at 450C.
So why can't we do CMOS on Venus?
...
IC related Bonus - found this paper describing the results of actual testing at 500C with a custom IC built by NASA. Think I missed this on my last review of papers on high temperature ICs.

A quote from the NASA paper: "While silicon electronics experience clearly demonstrates that complementary MOSFET (CMOS) technology is desired for implementing integrated circuits, development of the necessary high electrical quality gate-insulators that would enable long-term 500 °C operation of SiC MOSFETs will likely prove elusive for many years to come [21]."
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stevesliva
post Jun 19 2013, 06:08 AM
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^ Yeah, JFETs don't need that gate insulator. They also only had n-type, so of CMOS, they have MS. Nothing people haven't worked around in the past to make large devices. But, unfortunately, at the 10um geometries I poo-pooed earlier and with really low reliability, which isn't something that's easy to work around. Infinite money and access too commercial dev fabs, though... sigh.
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dtolman
post Jun 19 2013, 02:49 PM
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Sorry to keep shining rays of optimism here, but circling back to Raytheon's claims, it looks like its more than pie-in-the sky. Here is a 2012 paper describing testing they did with a SiC CMOS at 400C:
http://www.raytheon.co.uk/rtnwcm/groups/rs...emp_article.pdf.

So components that could theoretically function at ambient temperature on the (high plateau/peak) surface of Venus are in labs now. Assuming they're reliable, its just a question of time before they're commercially available.

Finally - if you want something to add to your reading list, I stumbled upon this fantastic overview of the 2013 state-of-the art in high temperature SiCs
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Robotbeat
post Jun 19 2013, 02:57 PM
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dtolman:
Ah, behold the motivating power of proving someone wrong on the Internet!

Thank you. smile.gif The Raytheon paper is quite useful to me. http://www.raytheon.co.uk/rtnwcm/groups/rs...emp_article.pdf.

(Still, power consumption at temperature is pretty high...)
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Bill Harris
post Jun 21 2013, 07:00 PM
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I'd suspect that the solution will come from the emerging technology of non-silicon transistors with nanoscale materials.

Beyond Silicon: Transistors Without Semiconductors
http://www.sciencedaily.com/releases/2013/...30621121015.htm

--Bill



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Robotbeat
post Jun 25 2013, 12:25 PM
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QUOTE (Robotbeat @ Jun 19 2013, 08:57 AM) *
dtolman:
Ah, behold the motivating power of proving someone wrong on the Internet!

Thank you. smile.gif The Raytheon paper is quite useful to me. http://www.raytheon.co.uk/rtnwcm/groups/rs...emp_article.pdf.

(Still, power consumption at temperature is pretty high...)

The Raytheon paper makes no mention to how long it can last at 400C. I've heard that the insulating layer doesn't last terribly long at those temperatures. The fact that no mention is made of length of time is a bad sign.
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tasp
post Jun 25 2013, 03:27 PM
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Thanx Robotbeat for mentioning the power consumption, it brings up another concern.

A hypothetical device on Venus operating at the high ambient temperature there will not be 100% efficient (nothing is anywhere), and it will warm above ambient temperature and need to dissipate some power into the environment.

It's another challenge, the device will need a heat sink (or active cooling, erf) and it makes the situation more complex, like it's not difficult enough already.

The material of the heatsink will need to be compatible with the environment and function properly.
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djellison
post Jun 25 2013, 04:11 PM
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QUOTE (tasp @ Jun 25 2013, 07:27 AM) *
The material of the heatsink will need to be compatible with the environment and function properly.


The material of every spacecraft needs to be compatible with the environment it's sent to and to function properly.

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SpaceListener
post Jun 25 2013, 08:48 PM
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If the chamber where it is stored electrical instruments has a static insulation and the air is emptied, the internal temperature would be lower than outside? I think the heat sink in Venus is not useful because the atmosphere is warmer outside than the inside of chamber.
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dtolman
post Jun 26 2013, 03:45 PM
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If you can get electronics running at ambient, just leave them exposed* and cool them off with a fan. After all - thats what we do with PCs here when they run hotter than the atmospheric temp smile.gif

On a more realistic note, if memory serves, the latest surface proposals were nuclear powered and cooled with a Stirling Cycle heat engine. Of course those missions anticipated a 200 C interior and 500 C exterior - a 300 C differential. I imagine the power requirements for running the heat engines would be lower if you can get the electronics closer to 400 C and a 100 C - or smaller - differential, and more than make up for the hotter electronics.

*Now we just need high temperature, acid rain resistant electronics
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siravan
post Jun 26 2013, 05:59 PM
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QUOTE
Now we just need high temperature, acid rain resistant electronics


Not much of acid rain on the surface (sulfuric acid evaporates before reaching ground), but high preesure-hot CO2 is highly corrosive and problematic. It seems that the only thing "easy" for a venus lander is the actual EDL. Parachutes to around 20-30 km, then free fall all the way down.
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Robotbeat
post Jun 26 2013, 09:09 PM
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QUOTE (dtolman @ Jun 26 2013, 10:45 AM) *
If you can get electronics running at ambient, just leave them exposed* and cool them off with a fan. After all - thats what we do with PCs here when they run hotter than the atmospheric temp smile.gif

On a more realistic note, if memory serves, the latest surface proposals were nuclear powered and cooled with a Stirling Cycle heat engine. Of course those missions anticipated a 200 C interior and 500 C exterior - a 300 C differential. I imagine the power requirements for running the heat engines would be lower if you can get the electronics closer to 400 C and a 100 C - or smaller - differential, and more than make up for the hotter electronics.

*Now we just need high temperature, acid rain resistant electronics

Indeed, those actively cooled mission proposals are what my mentor has been working on. But the power requirements are pretty big for active cooling, since your heat dump is so hot. That means completely custom high-power radioisotope... Flagship class funding requirement, but at best a Discovery-class risk level, so unlikely to fly before I retire.

But one good thing about Venus's atmosphere is that because it's so dense, it should carry /extra/ heat away rather well, better than on Earth. Of course, the problem is that you have to start out at ~450C or so....

Also, although there is no acid rain droplets on the surface, you do have the products of dissociated sulfuric acid, so corrosion is still a problem. But a better problem to have than the incredibly high temperatures.
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