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High-Temp Electronics For Venus Exploration, recent advances
siravan
post Mar 27 2013, 05:16 PM
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Agree. I didn't think of it from this aspect. But in the end of day, you cannot rely solely on testing at 20. You need to test in a similar environment as Venus. Also, what about the atmosphere? I guess CO2 at 90 bars and 450 C is rather corrosive.
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Robotbeat
post Apr 5 2013, 05:56 PM
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I've found a microcontroller that's supposed to work at 250C:
http://www.ic72.com/pdf_file/i/141332.pdf
Doesn't look to be widely available, but it's still the very best I've found for a microcontroller (it's hard to even find transistors in this range...).
http://www.ims.fraunhofer.de/news/detailan...electronic.html

That's getting close. Some people think the highest altitude parts of Venus are around 350-380C (100 degrees cooler than the average surface). This would allow long-duration stays in the lower parts of Venus's atmosphere (tethered balloon?) or perhaps make simple cooling techniques feasible (high-temperature solar panels hooked directly up to Peltier cooling devices... though the long and hot night would be a problem...).

Which reminds me, are there any electronics that could /survive/ at 400C, even if they can't operate at that temperature? The instruments could be operated only during the daylight when there is power to run the cooling equipment. Of course, operation by an RTG (even a small one) would be preferable, but that increases the minimum cost significantly. Which reminds me, are there any betavoltaic devices (far cheaper, less restriction on usage I think) which can operate at 400C? Too bad they only output on the order of 1E-6 Watts. We need at least one Watt before we can talk about cooling electronics (more like tens of watts, for a very small device).

What is the insolation (Watts per meter squared, not just direct but also diffuse) at noon on the surface of Venus?
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stone
post Apr 8 2013, 06:34 AM
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All the ideas are very strange, but NASA Glenn Research Center is already working on it.

http://www.lpi.usra.edu/meetings/ipm2012/pdf/1133.pdf
Development of a High Temperature Venus Seismometer and Extreme Environment Testing Chamber

A lander mission without camera is not a mission.
One point is: Is it possible to have a CCD or MOSFET camera at 4500-500C?


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djellison
post Apr 8 2013, 01:32 PM
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QUOTE (stone @ Apr 7 2013, 11:34 PM) *
A lander mission without camera is not a mission.


Yes it is. Not all spacecraft can, should or must carry cameras. Would it be nice to take a more modern imaging suite to the surface of Venus? Obviously.

There is still huge quantities of science to be done without one, however.
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dtolman
post Apr 8 2013, 03:00 PM
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The Solder question is very interesting. Looking into the state of the art for down-hole operations, it seems the solders used are at the very edge of being useful in their current applications (150-200 C) - for COTS it seems the mix of 5% tin, 93.5% lead, and 1.5% silver is useful up to ~250 C.

Beyond that point it seems that we're off into specialty solders for research projects - I see references to Aluminum being used (692 C melting point), though I imagine that's hard to work with (and how long will it last?). I do see a recent announcement of a cheaper solder of gold-silver-germanium which may fill the gap (ceiling of 350 C) - which if it does take off commercially would get COTS printed circuit boards right on the edge of being useful for a Venus mission with minimal cooling.

Also, figured I'd throw in some references to some off the shelf ICs that I found while looking into this - I see references from TI for a PCB rated at up to 250 C (and down to -55 C). Honeywell claims they have an IC that is rated for 5 years operation at 225, and that their max temp is close to 300 C.

Amazing how far they've come in the past decade.

EDIT - and it may be moving a lot farther. Just found this Department of Energy grant to United Silicon Carbide to demonstrate an electronic sensor package for downhole operations that runs at 500C (!). Based off the linked abstract, they were able to demonstrate a working package...
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stevesliva
post Apr 8 2013, 03:56 PM
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Flash Memory would be vital-- avoids mechanical storage:
http://www.ti.com/ww/en/hirel/high_temp_fl...-htflash-bti-en
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Robotbeat
post Apr 8 2013, 04:30 PM
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QUOTE (djellison @ Apr 8 2013, 07:32 AM) *
Yes it is. Not all spacecraft can, should or must carry cameras. Would it be nice to take a more modern imaging suite to the surface of Venus? Obviously.

There is still huge quantities of science to be done without one, however.

It'd be useful to have a camera even for just a few minutes (during descent and on the surface) for situational awareness. It just needs to take a few pictures then can burn up. It would help tremendously to know exactly where on the surface of Venus your lander landed and what sort of soil or rock you landed on. Not needed for the long-term, though, like temperature, pressure, wind speed, and seismograph measurements would. A disposable camera is a good 80/20 solution for a lander (it's difficult to keep a camera cool, since heat can travel more easily through windows, for instance).

I suppose an old tube-style camera may be workable at high temps.

Interesting about the DOE electronic sensor package at 500C...

And when you're talking about 350+C, the term is usually "brazing" not soldering. But yeah, the non-active portions of the circuit become basically just as difficult at these temps...
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tasp
post Apr 8 2013, 05:43 PM
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Don't know specifically about vacuum tube cameras (iconosocope I believe is the archaic term, LOL) in high heat, but vacuum tubes in general have a problem with high temperatures, surprisingly enough.

Despite the vacuum tube cathodes being strongly heated during operation (and that's why we used to wait for things to warm up before they would work), the anodes (which tubes need too) cannot be too hot. Going back 40 years in my schooling, I think the problem is secondary emission at high temp on the anode. The tube won't work right (or at all) if the anode is as hot as the cathode, and performance decreases as the temperature difference between anode and cathode decreases.

Solid state electronics as noted above are the best bet. Amazing the advances they have made in this regard.

A camera at these temperatures, even neglecting the electronics, is a fussy thing. having it stay in focus when that hot since the housing will likely expand and move everything. Lens coatings, seals, chemical attack from the corrosive atmosphere, etc. this is a tough challenge all the way around.

You'd also not want too much IR sensitivity in the image pickup or it would be swamped with it!!
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centsworth_II
post Apr 8 2013, 05:53 PM
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Why is everyone talking about cameras on Venus like it's never been done?
Attached Image

http://photoshopnews.com/2006/09/12/old-so...resh-surprises/
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Gsnorgathon
post Apr 8 2013, 06:05 PM
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I'm guessing folks are thinking of design for long-term survival. A camera that lasts a few hours is a bit easier than one that might last long enough to see sunrise on the morning following the landing. (And wouldn't that be something?)
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Holder of the Tw...
post Apr 8 2013, 08:42 PM
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No roving. Probably very little change in local weather. Changes in shadow patterns on the ground over the course of weeks, but how likely is it you would see anything else different in the landscape in the short term? We really don't know for sure.

I'd say two highly detailed 360 pans in color, offset for 3D (raising or lowering the camera a bit), each pan transmitted twice, and maybe if you get the seismometer emplaced quickly enough, a quick parting shot of that. You're good to go and the camera can fry.
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siravan
post Apr 8 2013, 10:38 PM
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I think it is unreasonable to expect a full fledge high-temperature computer with tons of flash memory; at least early on. The more likely system would be something akin to the late 1960s or early 70s technology (say Voyager style). One solution is to have most of the telecommunication systems and memory and command handling in a separate orbiter (which of course uses regular electronics), which then commands the lander in realtime and records the data without need for much memory in the lander. The orbiter could be in a low polar orbit and can probably communicates with the lander 10 minutes every 90 minutes or so.
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tasp
post Apr 9 2013, 02:44 AM
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For instance, the longer the camera lasts, the longer the focal length you can have on the camera (assuming a scan platform or a moving mirror of some kind).

The idea being, you have more time for more pictures, so a longer focal length gets you higher resolutions further from the probe. You'd want the time available (indefinite would be GREAT!) and the data rate available for the camera system to be utilized in sending as many pixels as possible of the area the probe lands in. Probably too much to hope for that the probe could analyze the pictures and aim for 'interesting' rocks or hills/mountains in the distance. So the probe should attempt to mosaic the entire area. (maybe a simple filter might be possible, even analog techniques might be useful. For instance, a photo of sharp angular details will have more high frequencies in an analog readout of the camera than will a photo of an area with rounded/soft forms. Presumably the sharp angles pictures would be more interesting)

Also should factor in transmission efficiency of the atmosphere, a hazy or dusty area (assuming areas on Venus vary in these details) would limit how much detail could be recorded at a distance.

Colorimetry will be a little different. We already know from the color filters used in the Soviet era that there is essentially no blue or violet light at the surface. Color analysis will be confined to red thru ~green. Also, viewing the surface in IR will be hindered at wavelengths corresponding to the ambient temperature, an IR camera won't record much detail in that band, nor at longer wavelengths. I don't know about polarized IR, maybe somebody knows if that has any practicality in this tough environment?
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DFinfrock
post Apr 9 2013, 03:00 AM
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QUOTE (siravan @ Apr 8 2013, 10:38 PM) *
The orbiter could be in a low polar orbit and can probably communicates with the lander 10 minutes every 90 minutes or so.


How difficult would it be to park a satellite in a geostationary orbit for full-time communication with a lander? Would it require too much fuel to achieve such an orbit?
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tasp
post Apr 9 2013, 04:00 AM
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The rotation period for Venus is sooo long . . .

How long is it ???

It's Hill Sphere isn't big enough for a geostationary (Venusostati, whatever) satellite!!


biggrin.gif
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