What, exactly, in the electronics requires heating? Is it just capacitors? Sensors calibrated for certain temp range? Most electronic components do very well down into the cryogenic temperature range.How is JWST handling this? I thought nearly all of its components were running at very cold temps.
Quote from: Don2 on 05/21/2016 08:23 pmWhat about the RTG? 20 years after manufacture that should still be producing 72% of its original power if it ages in the same way that the Viking ones did. Heat output should be 85% of new. Are you using actual power levels for the MMRTG being built for Mars 2020?Remember that the last Pu-238 manufactured in the U.S. was made in 1988.
What about the RTG? 20 years after manufacture that should still be producing 72% of its original power if it ages in the same way that the Viking ones did. Heat output should be 85% of new.
Quote from: a_langwich on 05/23/2016 09:35 pmWhat, exactly, in the electronics requires heating? Is it just capacitors? Sensors calibrated for certain temp range? Most electronic components do very well down into the cryogenic temperature range.How is JWST handling this? I thought nearly all of its components were running at very cold temps.Normal temperature for military grade electronics ( aka 'COTS' ) is -55C to 125C at best. First issues would be batteries, capacitors, but semiconductors will start to not behave at low temperatures as well. Unless they are specially designed low-temperature parts like 500-nano BiCMOS Here is a good read on this: link
Mismatches in the PCB coefficients of thermal expansion can cause solder joints to strain and fail.
True, but most of the external electronics in MSL had to be qualified to survive 3x mission life worth of thermal cycles without any heating (an exception was Chemcam in its heated box at the top of the remote sensing mast.)Most of the external heating requirements come from wet-lubricated mechanisms.See http://llis.nasa.gov/lesson/11501
There are many heritage hardware elements from MSL that will be re-used on M2020. Some of these are exact copies of MSL designs; others are MSL build-to-print designs with slight modifications. The M2020 mobility system, which has 6 drive motors and 4 steer motors, will be essentially the same as MSL. The MSL wheels, which sustained significant damage during traverses over sharp rock s inside Gale Crater, will be strengthened (at the cost of increased mass) for M2020.
I sure hope they toughen up the wheels of the next rover - Curiosity's have taken a hell of a hammering.
I wonder if the wheel damage is an example of something called stress corrosion cracking. If certain chemicals are present in the environment, it can greatly accelerate the rate at which fatigue cracks grow. I doubt anybody has ever studied the effect of perchlorate on aluminum, but I know that chloride ions do attack aluminum. Both chloride ions and perchlorates contain chlorine.
New stronger wheel design confirmed by Deputy JPL director today at Space Tech Expo. Thicker metal, curved tread pattern for less mechanical stress.
Also, it would not surprise me if JPL has already modeled further damage to the Curiosity wheels so they know what to do if it happens. It would make sense to at least do this on a computer, and maybe they've even put some very damaged wheels on their engineering mockup to see how it handles.
Amusingly, the only part of the wheel treads that survived alright were the sections with "JPL" stamped into them in Morse code.
I've seen them driving the test rig up and down a hill in the yard (which I don't seem to have a picture of), but I am not sure if that was just general drive performance characterization or if it was using damaged wheels. I would be surprised if they haven't done tests on damaged wheels, though.
Quote from: Star One on 05/10/2016 11:41 pmPotential biosignatures identified?Spirit observed some mineral fomations that looked like some seen here on Earth. Still not sure if the ones here on Earth were made by life though.'Cauliflower' Silica Formations on Mars: Evidence of Ancient Life?http://www.americaspace.com/?p=91183
Potential biosignatures identified?
Geyserite are generally associated with microbial activity. See:https://hal-insu.archives-ouvertes.fr/insu-01163128/documenthttp://www.mdpi.com/2078-1547/5/2/430Steve Ruff's presentation on possible geyserite at the 2nd 2020 rover landing site workshop resulted in Gusev crater being added to the list http://marsnext.jpl.nasa.gov/workshops/2015_08/16_Ruff_M2020_2nd_LSW_presentation_v3.pdfHere are some photos of geyserites from NZ