And yet surface temperatures do produce electromagnetic waves - eg. infrared.Would it be possible to harvest infrared spectrum along with solar energy that makes it through Venus' clouds, to then power a surface probe? And considering how dense Venus' atmosphere is, perhaps it might be possible to make use of buoyancy forces to reduce the effective weight of the probe and increase its mobility.
Quote from: sanman on 11/25/2017 06:41 pmAnd yet surface temperatures do produce electromagnetic waves - eg. infrared.Would it be possible to harvest infrared spectrum along with solar energy that makes it through Venus' clouds, to then power a surface probe? And considering how dense Venus' atmosphere is, perhaps it might be possible to make use of buoyancy forces to reduce the effective weight of the probe and increase its mobility.There have been suggestions to use sunlight. Venus surface level light levels have been described as "Twilight."There have also been designs for "electric" cars to burn short chain hydrocarbons in a burner surrounded by IR PV cells. A thermophotovoltaic system. The problem is semiconductors need a certain level of free electrons. All our conventional semiconductors are chosen to have this level around room temperature. As the temperature rises the line between P, N and Intrinsic levels of conductivity blurs into a single level and the devices made out of them stop working.
Quote from: colbourne on 11/23/2017 05:00 amFor the power source why not get the Venus temperature to work for you.Using a pressurised liquid (probably solid for most of the trip) from Earth let the heat run a steam engine or turbine, which can drive a generator. The liquid does not have to be water, but the most suitable material for Venus, possibly a metal or salt.If well designed the steam engine will also be able to cool the lander at the same time.It's not a high temperature you need to extract useful energy, it's a difference in temperature. Steam engines work by extracting power from the movement of heat from the boiler to the outside world.If you're sitting on the surface of Venus, everything around you is at the same high temperature. So you can't extract any energy from it. It's one of the fundamental principles of thermodynamics.
For the power source why not get the Venus temperature to work for you.Using a pressurised liquid (probably solid for most of the trip) from Earth let the heat run a steam engine or turbine, which can drive a generator. The liquid does not have to be water, but the most suitable material for Venus, possibly a metal or salt.If well designed the steam engine will also be able to cool the lander at the same time.
Quote from: ChrisWilson68 on 11/23/2017 06:05 amQuote from: colbourne on 11/23/2017 05:00 amFor the power source why not get the Venus temperature to work for you.Using a pressurised liquid (probably solid for most of the trip) from Earth let the heat run a steam engine or turbine, which can drive a generator. The liquid does not have to be water, but the most suitable material for Venus, possibly a metal or salt.If well designed the steam engine will also be able to cool the lander at the same time.It's not a high temperature you need to extract useful energy, it's a difference in temperature. Steam engines work by extracting power from the movement of heat from the boiler to the outside world.If you're sitting on the surface of Venus, everything around you is at the same high temperature. So you can't extract any energy from it. It's one of the fundamental principles of thermodynamics.I dont think you need a difference in temperature as long as what you use as fuel will reach a high enough pressure to be vented after it has produced useful work (like the toy CO2 engines). As it expands it will also cool the vital component of the lander. The tank which stores the working fluid will not need to be as strong, due to Venus's high pressure, as would be required on Earth. Having a solid at Earth temperatures for this fluid will allow a lighter craft to be built.
So maybe it's a matter of searching for the right material with the desired bandgap properties. A suitable candidate could be out there.
Not really. You have contradictory requirements. You want a material which has a narrow bandgap for IR PV cells but a wide band gap so the semiconductor physics works right at 450c+.Making something that is both at the same is AFAIK impossible.
Quote from: colbourne on 11/26/2017 12:33 pmQuote from: ChrisWilson68 on 11/23/2017 06:05 amQuote from: colbourne on 11/23/2017 05:00 amFor the power source why not get the Venus temperature to work for you.Using a pressurised liquid (probably solid for most of the trip) from Earth let the heat run a steam engine or turbine, which can drive a generator. The liquid does not have to be water, but the most suitable material for Venus, possibly a metal or salt.If well designed the steam engine will also be able to cool the lander at the same time.It's not a high temperature you need to extract useful energy, it's a difference in temperature. Steam engines work by extracting power from the movement of heat from the boiler to the outside world.If you're sitting on the surface of Venus, everything around you is at the same high temperature. So you can't extract any energy from it. It's one of the fundamental principles of thermodynamics.I dont think you need a difference in temperature as long as what you use as fuel will reach a high enough pressure to be vented after it has produced useful work (like the toy CO2 engines). As it expands it will also cool the vital component of the lander. The tank which stores the working fluid will not need to be as strong, due to Venus's high pressure, as would be required on Earth. Having a solid at Earth temperatures for this fluid will allow a lighter craft to be built.Good to know you don't let the laws of thermodynamics stop you.
Is there some reason that an actively cooled rover isn’t a possibility?
NASA has demonstrated a resolve for a flagship mission in the coming years to revisit Venus and land instruments on the surface. Venus has a corrosive, high-pressure (~100 bar), high-temperature (up to 500C) environment.The SiC-JFET technology and RS-485 link proposed complement Ozark IC's existing SiC-CMOS designs, including a general-purpose microprocessor and an integrated UV camera, that can be combined to create scientific instruments and housekeeping circuits that can operate at Venus surface temperature conditions.
Doesn't have to be clockwork.Ozark IC is one of the firms doing some work for NASA.For example, on silicon carbide ICsQuoteNASA has demonstrated a resolve for a flagship mission in the coming years to revisit Venus and land instruments on the surface. Venus has a corrosive, high-pressure (~100 bar), high-temperature (up to 500C) environment.The SiC-JFET technology and RS-485 link proposed complement Ozark IC's existing SiC-CMOS designs, including a general-purpose microprocessor and an integrated UV camera, that can be combined to create scientific instruments and housekeeping circuits that can operate at Venus surface temperature conditions. A report on the microcontroller developed under this program https://techport.nasa.gov/file/20579 .This is leveraging commercial SiC IC processes, though at higher temperature.
Oh, wait - how about this - why not have an orbiter or a balloon sitting above the clouds, which harvests some of that abundant solar radiation up there and it then downconverts and re-transmits the stuff as microwave energy down to the rover on the ground, which would harvest that with a rectifier-type of antenna?Why wouldn't that be feasible - or what are the pro's & cons of it?
The upper layer of troposphere exhibits a phenomenon of super-rotation, in which the atmosphere circles the planet in just four Earth days, much faster than the planet's sidereal day of 243 days. The winds supporting super-rotation blow at a speed of 100 m/s (~360 km/h or 220 mph)
Obviously with the high temperature and pressure on Venus, to get the most cooling and power from a compressed gas engine would make the choice of fluid an important choice.How many seconds of run time would be considered a success ?
What are the wind conditions like at the surface? Could a small wind turbine be used to harvest useful energy to power a rover?