Hot chips for Venus

[lajoswinkler]

http://www.eetimes.com/document.asp?doc_id=1327322&_mc=NL_EET_EDT_EET_daily_20150803&cid=NL_EET_EDT_EET_daily_20150803&elq=69756d91c25c4d1a82e352046f6dc7f8&elqCampaignId=24193&elqaid=27324&elqat=1&elqTrackId=1282d02ef1c445739ca5599b25089647

http://spectrum.ieee.org/tech-talk/aerospace/robotic-exploration/nasa-commissions-ultra-high-temp-chips-for-venus-landsailing-rover

They couldn't survive surface temperature of Venus, but they will keep working at much higher temperatures than the ones we normally use.

That means that, properly shielded, they would work for a longer time.

This is what I find most interesting about designing a related rover/probe:

NASA, understandably, wants to minimize the amount of electronics that need to be actively cooled on any Venus lander, because keeping things cool on the surface of Venus is going to suck down a massive amount of power. Photovoltaics won’t really work under all those clouds. But one slightly counterintuitive option might be a cooling system powered by a Stirling engine, which depends on the rover generating as much heat as it possibly can. Stirling engines convert a heat differential into mechanical energy, so the idea is that you’d bottle up a bunch of plutonium-238, which would heat itself to 1,200 °C through radioactive decay. With one side of a Stirling engine acting as a heat sink for the plutonium and the other side exposed to the comparatively frigid Venutian atmosphere, a Stirling engine could generate several hundred watts of powerâ€â€enough to keep the electronics of a well insulated rover under 300 °C.

Exact same thing I've been talking about. To cool it down, you need to heat one part of the system way up.

This would work for a long time, if the Stirling engine is well made. The probe would be refrigerated to 200-250 °C by using the heat flow (therefore work) from a very hot first tank to the heatsink which is Venusian atmosphere.

We might land a rover there sooner than we thought.

[vger]

"Nuclear-powered" air-conditioning! Very Kerbal!

[PB666]

http://www.eetimes.com/document.asp?doc_id=1327322&_mc=NL_EET_EDT_EET_daily_20150803&cid=NL_EET_EDT_EET_daily_20150803&elq=69756d91c25c4d1a82e352046f6dc7f8&elqCampaignId=24193&elqaid=27324&elqat=1&elqTrackId=1282d02ef1c445739ca5599b25089647

http://spectrum.ieee.org/tech-talk/aerospace/robotic-exploration/nasa-commissions-ultra-high-temp-chips-for-venus-landsailing-rover

http://img.deusm.com/eetimes/2015/08/1327322/rcj_NASA_Venus_Rover_Ozark-IC_1.jpg

They couldn't survive surface temperature of Venus, but they will keep working at much higher temperatures than the ones we normally use.

That means that, properly shielded, they would work for a longer time.

This is what I find most interesting about designing a related rover/probe:

NASA, understandably, wants to minimize the amount of electronics that need to be actively cooled on any Venus lander, because keeping things cool on the surface of Venus is going to suck down a massive amount of power. Photovoltaics won’t really work under all those clouds. But one slightly counterintuitive option might be a cooling system powered by a Stirling engine, which depends on the rover generating as much heat as it possibly can. Stirling engines convert a heat differential into mechanical energy, so the idea is that you’d bottle up a bunch of plutonium-238, which would heat itself to 1,200 °C through radioactive decay. With one side of a Stirling engine acting as a heat sink for the plutonium and the other side exposed to the comparatively frigid Venutian atmosphere, a Stirling engine could generate several hundred watts of powerâ€â€enough to keep the electronics of a well insulated rover under 300 °C.

Exact same thing I've been talking about. To cool it down, you need to heat one part of the system way up.

This would work for a long time, if the Stirling engine is well made. The probe would be refrigerated to 200-250 °C by using the heat flow (therefore work) from a very hot first tank to the heatsink which is Venusian atmosphere.

We might land a rover there sooner than we thought.

The RTG is not efficient, it gets less so as the differential decreases, and it has to get rid of waste heat. I would be cheaper to carry 50 gallons of water, insulate the hell out of the thing, place the RTG well away from the ship, and a drip of water to create steam and cool the ship down to whatever the boiling point of water is at Venus pressure. You could run the exhaust steam passed to RTGs to remove heat as it passed and still not very efficient. RTGs work great in the dead cold of space, at a very high temperature one has to wonder how long a thermocouple will last.

Even if the thermodynamics of the model worked, think about the fact that the surface temperature of venus is 462 °C which is above not only the vaporization point of oil required to lubricate the engine, but is at the denaturation temperature of oil molecules themselves.

[AngelLestat]

The problem that RTG will add substantial weight for not a great amount of energy.. You need to transmit data, move around, cooling, etc.

I will look more seriously how to use the kinetic energy of the wind to move the rover and produce energy.

This may reduce the overall weight by a lot, but it will need more research, because is a lot more easy to put a RTG inside and move on.

We have 5km/h to 10km/h wind at surface, with a density of 64kg/m3. This is not the best to extract energy from it, but is great to move your prove around.

I imagine a prove with variable density (that can expand and contract it self), two main parts, one that can deploy and touch the ground (also act as anchor) to make experiments, and the other to float around generating power, and reducing its density in case it wants to move to other location.

Like this concept but very different:

You can not choose very well where to go, but you can explore bigger distances without get stuck around rocks or lava.

PB666: I dont understand, you are talking of a open cycle? But what happens when your water is out?

Edited August 7, 2015 by AngelLestat

[Armchair Rocket Scientist]

The RTG is not efficient, it gets less so as the differential decreases, and it has to get rid of waste heat. I would be cheaper to carry 50 gallons of water, insulate the hell out of the thing, place the RTG well away from the ship, and a drip of water to create steam and cool the ship down to whatever the boiling point of water is at Venus pressure. You could run the exhaust steam passed to RTGs to remove heat as it passed and still not very efficient. RTGs work great in the dead cold of space, at a very high temperature one has to wonder how long a thermocouple will last.

Even if the thermodynamics of the model worked, think about the fact that the surface temperature of venus is 462 °C which is above not only the vaporization point of oil required to lubricate the engine, but is at the denaturation temperature of oil molecules themselves.

This design uses a Stirling RTG, which replaces the thermocouple with a heat engine. This is several times more efficient than a conventional RTG, but they aren't normally used because they're more complex than a conventional RTG, and normally spacecraft don't need high power densities anyway. Oil vaporizing wouldn't be a concern either: the vehicle could use a dry lubricant. These are already used on spacecraft because in a vacuum oils vaporize even at temperatures encountered in LEO, and can also freeze. Dry lubricants can also operate at Venus's surface temperature without problems.

The main concern I see is getting rid of the heat from the RTGs during interplanetary cruise; unlike a nuclear reactor an RTG can't be throttled or shut off. A fairly complex cooling system might be required.

Also, 50 gallons of water would weigh as much as one of the Mars Exploration rovers, and would probably only last a few days at best. By comparison, this design has the potential to function for months, or even years.

[vger]

I will look more seriously how to use the kinetic energy of the wind to move the rover and produce energy.

I wonder if it's even worth it to use a rover?

As weird as it sounds to do such a thing in an atmosphere instead of a fluid, the air there is so thick, why not? One of the big ideas for Venus right now is a blimp of sorts that can chill in the upper atmosphere almost indefinitely. Could a 'submarine' of sorts work with that, using ballast tanks to adjust for altitude? Something that could land, but then when the temperature becomes too great, empty the ballast tanks to climb higher until it cools down. Rinse and repeat.

[0111narwhalz]

I've been looking into RT/SGs lately, and it seems that an RSG that operates at... half again the needed capacity would go for about half a half-life, more than enough with most fuels. An intriguing alternative is a sort of "rechargable RSG," using halfnium. Ship an inert block of halfnium-whatsit, charge it with PV in LVO, and drop it onto Venus. I think the elevated state of halfnium has a pretty impressive energy density, too.

[ChrisSpace]

Sees title of thread... MEGA FACEPALM

[peadar1987]

The RTG is not efficient, it gets less so as the differential decreases, and it has to get rid of waste heat. I would be cheaper to carry 50 gallons of water, insulate the hell out of the thing, place the RTG well away from the ship, and a drip of water to create steam and cool the ship down to whatever the boiling point of water is at Venus pressure. You could run the exhaust steam passed to RTGs to remove heat as it passed and still not very efficient. RTGs work great in the dead cold of space, at a very high temperature one has to wonder how long a thermocouple will last.

Even if the thermodynamics of the model worked, think about the fact that the surface temperature of venus is 462 °C which is above not only the vaporization point of oil required to lubricate the engine, but is at the denaturation temperature of oil molecules themselves.

Water boils at 300 celsius at Venusian surface pressure. Just for information purposes

[lajoswinkler]

I wonder if it's even worth it to use a rover?

As weird as it sounds to do such a thing in an atmosphere instead of a fluid, the air there is so thick, why not? One of the big ideas for Venus right now is a blimp of sorts that can chill in the upper atmosphere almost indefinitely. Could a 'submarine' of sorts work with that, using ballast tanks to adjust for altitude? Something that could land, but then when the temperature becomes too great, empty the ballast tanks to climb higher until it cools down. Rinse and repeat.

Most of the surface, if not all of it (perhaps the mountain tops aren't) is immersed in a supercritical fluid carbon(IV) oxide. Blimping around is hypothetically possible.

Sees title of thread... MEGA FACEPALM

Why is that?

Water boils at 300 celsius at Venusian surface pressure. Just for information purposes

Indeed, that's about the correct temperature.

[Tex_NL]

To power a Venusian rover what about microwave radiation? A satellite in orbit could collect all the solar power it needs and beam down a focussed beam of microwaves towards the rover. This bean can be converted into usable energy.

To survive the hazardous atmosphere a rover would have to be heavily shielded anyway, the additional microwaves would not hurt it. And you don't have to bother about accidentally frying indigenous life as there isn't any. (And if there happens to be life it's safe to assume it's well used to the harsh conditions and the radiation doesn't harm it.)

[ComradeWolfe]

Windmill-powered refrigeration, anyone? Low wind speeds should be offset by high atmospheric density.

[shynung]

The main concern I see is getting rid of the heat from the RTGs during interplanetary cruise; unlike a nuclear reactor an RTG can't be throttled or shut off. A fairly complex cooling system might be required.

Huge radiator panels on the interplanetary cruise stage could be used. Just before Venusian atmospheric entry, these could be staged off along with the cruise stage.

[Armchair Rocket Scientist]

I wonder if it's even worth it to use a rover?

As weird as it sounds to do such a thing in an atmosphere instead of a fluid, the air there is so thick, why not? One of the big ideas for Venus right now is a blimp of sorts that can chill in the upper atmosphere almost indefinitely. Could a 'submarine' of sorts work with that, using ballast tanks to adjust for altitude? Something that could land, but then when the temperature becomes too great, empty the ballast tanks to climb higher until it cools down. Rinse and repeat.

There are a few things to consider there:

1. How long does it take your vehicle to ascend and descend from an altitude where it can cool down? You might have to go 30 km up to reach an air temperature of 200 *C. On Earth, a weather balloon can cover this in about an hour. However, on Venus the denser air means drag will be much higher (with no lift or updrafts, the equilibrium speed of an ascending or descending balloon has drag equal to the net buoyancy). It could take days for the probe to change altitude, meaning the time spent at unsafe altitudes is so long that you'd need a cooling system anyway, which makes the blimp concept kind of pointless.

2. What material are you planning to use for your envelope? It needs to be flexible enough to be inflated, strong enough to store your lifting gas (probably something like nitrogen) at a fairly large pressure difference (zero-pressure envelopes run out of gas after a few cycles), and finally it must be able to withstand Venusian surface temperatures without melting. You might be able to cool your electronics, but your envelope will quickly reach ambient temperature. 400+ degrees celsius is pushing the limits of even high-temperature polymers like kevlar.

3. The repeated changes in temperature and pressure could give your materials some fatigue problems they wouldn't experience if they just stayed on the surface.

[AngelLestat]

I wonder if it's even worth it to use a rover?

As weird as it sounds to do such a thing in an atmosphere instead of a fluid, the air there is so thick, why not? One of the big ideas for Venus right now is a blimp of sorts that can chill in the upper atmosphere almost indefinitely. Could a 'submarine' of sorts work with that, using ballast tanks to adjust for altitude? Something that could land, but then when the temperature becomes too great, empty the ballast tanks to climb higher until it cools down. Rinse and repeat.

I called rover because the chip was designed for this vehicle:

Of course in my idea would not be a rover.

That is a good design but you need a smooth terrain, venera 10 show that the terrain is very smooth, but venera9 show a very different case:

Now I read that the sail rover will have an emergency small ballon that will inflate (to float) in case is stuck.

I guess the sail rover has electric motor in their 2 back wheels, which can use it as generators when it moves with the sail.

But about include PV or RTG, doesn´t looks as the most efficient way to achieve the mission.

About a "submarine" to explore venus from 50km layer to surface... is hard but possible.

You need to allow the ballon contract and expand a lot. Different fluids as water or amoniac can help to passive height control, because they boil at different temperatures and you may keep the desired pressure inside to counter the outside pressure using the venus heat.

The good of this approach, that you dont need cooling device, if your temperature start to reach the chip, then the prove rise height and cool it.

But it will be much easier to make a airship that can float between 5 km to surface.

The only problem is how you generate energy? If you dont have an anchor, you cant generate energy from the wind.

If we have stones is easy to desing an anchor, but if the soil is like in the first picture, then we are in trouble.

To power a Venusian rover what about microwave radiation? A satellite in orbit could collect all the solar power it needs and beam down a focussed beam of microwaves towards the rover. This bean can be converted into usable energy.

To survive the hazardous atmosphere a rover would have to be heavily shielded anyway, the additional microwaves would not hurt it. And you don't have to bother about accidentally frying indigenous life as there isn't any. (And if there happens to be life it's safe to assume it's well used to the harsh conditions and the radiation doesn't harm it.)

The focus point of that energy in the ground will be very large (5 km diameter), so you are wasting a lot of energy.

Windmill-powered refrigeration, anyone? Low wind speeds should be offset by high atmospheric density.

Is the same thing we are talking about.

Huge radiator panels on the interplanetary cruise stage could be used. Just before Venusian atmospheric entry, these could be staged off along with the cruise stage.

But look how much extra mass you need to add a RTG... it really worth it?

1. How long does it take your vehicle to ascend and descend from an altitude where it can cool down? You might have to go 30 km up to reach an air temperature of 200 *C. On Earth, a weather balloon can cover this in about an hour. However, on Venus the denser air means drag will be much higher (with no lift or updrafts, the equilibrium speed of an ascending or descending balloon has drag equal to the net buoyancy). It could take days for the probe to change altitude, meaning the time spent at unsafe altitudes is so long that you'd need a cooling system anyway, which makes the blimp concept kind of pointless.

yeah, is a good point, but it depends on your heat insulation, also if your heat insultation is good, then you dont need to extract much heat. But not sure the efficiency to extract heat from a 250c source to a 450c

2. What material are you planning to use for your envelope? It needs to be flexible enough to be inflated, strong enough to store your lifting gas (probably something like nitrogen) at a fairly large pressure difference (zero-pressure envelopes run out of gas after a few cycles), and finally it must be able to withstand Venusian surface temperatures without melting. You might be able to cool your electronics, but your envelope will quickly reach ambient temperature. 400+ degrees celsius is pushing the limits of even high-temperature polymers like kevlar.

It can be rigid, using tantalum paint.

With a dirigible shape which center cilinders expand or contract until form an ellipsoid.

3. The repeated changes in temperature and pressure could give your materials some fatigue problems they wouldn't experience if they just stayed on the surface.

I guess we can have a better alternative to the sail rover, I have some ideas how to solve mostly all issues, but not sure yet the anchor issue to extract energy from the wind.

[shynung]

But look how much extra mass you need to add a RTG... it really worth it?

The RTG problem I was responding to concerned a Stirling RTG, which can be several times more efficient than a typical RTG.

In a thick Venusian atmosphere, where solar panels might not generate much electricity, a self-contained power source such as an RTG is definitely worth sticking a radiator on the cruise stage.

Plus, if one can get a liquid droplet radiator, the cooling system mass just went down considerably.

Edited August 8, 2015 by shynung