Author Topic: Clockwork Rover to Explore Venus - AREE  (Read 14734 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.
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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.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

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.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

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?

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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.

Offline speedevil

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #29 on: 12/17/2017 09:04 PM »
Doesn't have to be clockwork.
Ozark IC is one of the firms doing some work for NASA.
For example, on silicon carbide ICs
Quote
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.

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.


« Last Edit: 12/17/2017 09:06 PM by speedevil »

Offline Nilof

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #30 on: 12/18/2017 05:07 AM »
Doesn't have to be clockwork.
Ozark IC is one of the firms doing some work for NASA.
For example, on silicon carbide ICs
Quote
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.

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.

One doesn't exclude the other. Lots of other components beside IC's have trouble in Venus conditions.
« Last Edit: 12/18/2017 05:07 AM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline sanman

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #31 on: 12/19/2017 03:03 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.

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?

Offline speedevil

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #32 on: 12/19/2017 09:38 PM »
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 ground side of this would be very easy.
From wikipedia on the atmosphere of venus
Quote
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)
- does not make this seem promising.

Offline redliox

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #33 on: 12/19/2017 09:53 PM »
A balloon operating in the upper cloud decks could probably suffice with current technology, but the needed science is near ground level including atmospheric composition.

My suggestion would be to start simple with a stationary lander.  At the least, supplement the electronics with some of the heat-resistant methods mentioned here and aim for a goal of 3 to 6 hours.  For something more ambitious, definitely intermix some clockwork instrumentation and have lander deploy it during its functional lifetime; ideally some of them could outlast the parent lander.

What kind of instruments could function with clockwork means?  I assume the more physical instruments like penetrometers, seismometers, and aneometers aren't too huge a stretch.
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Offline Nilof

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #34 on: 12/20/2017 05:33 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.
Good to know you don't let the laws of thermodynamics stop you.

The laws of thermodynamics do allow you to use a difference in pressure or a difference in chemical potential instead. Otherwise, you wouldn't be able to extract energy from a compressed spring for example. And fuel cells wouldn't be able to even come near the efficiencies that you commonly get from them, at their typical operating temperatures.
« Last Edit: 12/20/2017 05:34 PM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline colbourne

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #35 on: 12/21/2017 04:30 AM »
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 ?

Offline bad_astra

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #36 on: 12/21/2017 02:53 PM »
I for one am enthused for Rolex 1!

A stirling with a solar collector could be used for power to wind the mainspring and charge the spark gap coil, using something like zinc as the working fluid, which melts at a slightly higher temperature than Venus surface.
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Offline john smith 19

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #37 on: 01/24/2018 09:57 PM »
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 ?
Look up the history of Venus landers. Given the trouble you're looking at to develop for this environment that's the baseline you have to beat.

IIRC it's at least 2 hours. So 1 day is good. 1 Month better and 1 Venusian year would be great.
You need to be thinking about sidestepping electronics more or less totally.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline sanman

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #38 on: 01/24/2018 11:47 PM »
What are the wind conditions like at the surface? Could a small wind turbine be used to harvest useful energy to power a rover?

Offline colbourne

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Re: Clockwork Rover to Explore Venus - AREE
« Reply #39 on: 01/26/2018 02:30 AM »
What are the wind conditions like at the surface? Could a small wind turbine be used to harvest useful energy to power a rover?
At the surface the winds are very low speed due to the air density. You probably could still extract enough energy from it to power your equipment, but it may be rather unreliable.