Author Topic: Clockwork Rover to Explore Venus - AREE  (Read 4341 times)

Offline john smith 19

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #20 on: 11/25/2017 09:33 PM »
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.
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.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline sanman

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #21 on: 11/25/2017 10:31 PM »
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.
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.

So maybe it's a matter of searching for the right material with the desired bandgap properties. A suitable candidate could be out there.

Offline colbourne

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #22 on: 11/26/2017 12:33 PM »
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.

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.

Offline john smith 19

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #23 on: 11/26/2017 05:41 PM »
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.

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.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline john smith 19

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #24 on: 11/26/2017 05:53 PM »
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.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline sanman

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #25 on: 11/26/2017 08:57 PM »
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.

What if you just look for the material having the lowest possible bandgap that functions at that temperature?

Offline colbourne

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #26 on: 11/27/2017 03:24 AM »
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.

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.
You either do not understand  CO2 motors or have no knowledge of the laws of thermodynamics yourself.

https://en.wikipedia.org/wiki/Pneumatic_motor

Offline tnphysics

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #27 on: 12/06/2017 04:56 PM »
Is there some reason that an actively cooled rover isnít a possibility?

Online A_M_Swallow

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #28 on: 12/06/2017 10:49 PM »
Is there some reason that an actively cooled rover isnít a possibility?

Cooling systems require large quantities of energy. Where the hear sink is at a high temperature even more energy is needed and our power sources run inefficiently.

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