Why don't we have a Venus rover by now?

[Kerbart]

Simply as the title states? We have rovers on the Moon and Mars... Why not Venus? I know there is extreme temperatures and crushing pressures, but this is the 21st century.

Despite this being the 21st century, the laws of physics have not changed. Materials start to melt and if not simply lose their strength at temperatures of 450°C (850°F). Which is inconvenient at a pressure we find here in oceans at around 1000m (3000' give or take) below sea level. Unless you opt for an "open" construction but then you have to deal with abrasive gasses (and keep in mind chemical processes, including corrosion, speed up with higher temperatures, and it's HOT).

Unlike the moon and mars, lifetime of Venus surface probes is measured in hours, not months. You simply get much more research for the same money if you send your probes to somewhere else than Venus.

[PhaserArray]

Simply as the title states? We have rovers on the Moon and Mars... Why not Venus? I know there is extreme temperatures and crushing pressures, but this is the 21st century. I am pretty sure it could be overcome.

It is not only the crushing pressures and heat, it is also the sulfuric acid in the atmosphere that makes is hard (read: harder) to get there and rove around on the surface.

Edited February 14, 2014 by PhaserArray

[lajoswinkler]

It is not only the crushing pressures and heat, it is also the acid in the atmosphere that makes is hard (read: harder) to get there and rove around on the surface.

Corrosion on the surface of Venus isn't a problem because that acid never reaches it. It's in the cloud cover high up. There are traces of corrosive gases on the surface, but all they can do is passivate the surface of construction metals.

You basically have around 450-470°C, 92 atm CO2 environment. That will melt zinc and is on the verge of red hot glow of steel.

Pressure is not a problem. Heat management is.

If you want a machine to work, you need to dump its waste heat. Heat won't spontaneously flow towards a hotter object. If you can keep the electronics working at the environmental temperature, and the energy producing unit is even hotter, you've got yourself a working machine.

Unfortunatelly, none of our electronics can work in such high temperatures. Venera probes were colder than Venus, and they were working until enough heat creeped inside.

What could (scientifically speaking) be done is to use a really hot RTG to run a refrigerator. I don't know if that would be technologically viable. I suspect you'd need a really powerful RTG unit to generate extreme heat and thus use the atmosphere as a heat sink, dumping lots of heat into it to ensure a small inside part of the probe is kept cooler, let's say 200°C.

I'm also not sure what to use as a heat exchanging fluid. I doubt cooling via passive radiators would be enough.

A large probe with a nuclear reactor could work just fine.

[Kerbart]

What could (scientifically speaking) be done is to use a really hot RTG to run a refrigerator. I don't know if that would be technologically viable. I suspect you'd need a really powerful RTG unit to generate extreme heat and thus use the atmosphere as a heat sink, dumping lots of heat into it to ensure a small inside part of the probe is kept cooler, let's say 200°C.

I'm also not sure what to use as a heat exchanging fluid. I doubt cooling via passive radiators would be enough.

I didn't think of that. PCB's are going to be a problem because all the solder on it will melt right off. Would embedding the electronics in a block of resin with coolant-filled pipes running through it work? The coolant still needs to dump its heat, but it's an alternative to putting them inside a refrigerated cabinet (with all the pressure issues that come with it)

[Nuke]

we have thermodynamic processes that can actively cool the components. i imagine keeping everything in a low pressure freezer. id actually take advantage of the thick atmosphere and not use a rover at all. put the whole thing on a quad copter platform. this could hover for sample collection. high temperature brushless motors (replacing copper with high temperature alloys with good conductivity and corrosion resistence) on "air" bearings should put up to the punishment. to take samples you would need to land, and then cool the samples, bring them into the cold zone for analysis.

problem is i dont see this rig being very light. the pressure chamber alone would be the bulk of the weight. and refrigeration hardware isnt light either. you would probibly need a nuclear reactor to power the refrigeration cycle, as well as the motors, and good luck cooling that. so this is going to have to hold out for better power tech, especially ones that can work in a hot zone.

this would have the advantage of being able to retreat to a colder altitude if neccisary. so only small duration hit and run sample grabs would be possible.

[DonLorenzo]

I just read this: http://beyondearthlyskies.blogspot.com/2013/05/cooling-venus-rover.html

I think they reference the 50 day rover mentioned before, they speak of putting the electronics in a 10cm sphere insulated by ceramics and actively cooled. Power comes from 7x 250W RTGs (problem 1: not enough plutonium left to do that) mated to stirling engines, the temperature gradient would then be 1200C to 500C (helium as working fluid) and that shakes out to 400-480W of available electrical power. 100W of which would be used for operations (driving, electrics, etc.) and the rest for cooling that electronics-sphere. They would cool it down to 300C.

It all sounds awesomely out of this world, I'd love to see it happen

[Nuke]

7 rtgs? damn. at that point just build a nuclear reactor.

and refrigeration is well understood. its the same technology that keeps my beer cold

[jwenting]

I'm also not sure what to use as a heat exchanging fluid. I doubt cooling via passive radiators would be enough.

I'm thinking Mercury...

Or sodium, like they use as a heat exchange medium in some nuclear powered submarines (haven't checked if it's solid or liquid at the temperatures we're talking about, but something like that).

[MBobrik]

7 rtgs? damn. at that point just build a nuclear reactor.

and refrigeration is well understood. its the same technology that keeps my beer cold

Driving the refrigerator with a wind turbine would be much simpler. the wind never stops there.

[Seret]

Driving the refrigerator with a wind turbine would be much simpler. the wind never stops there.

Might be difficult to make one durable enough. We're having trouble making tidal stream turbines tough enough to handle being immersed in moving water. Keeping it together in that hot soupy atmosphere would be a considerable engineering challenge.

Over and over it keeps coming down to the extreme heat. It speeds up corrosion, things creep, normal lubricants would be useless, electronics hate it, etc, etc.

[MBobrik]

We're having trouble making tidal stream turbines tough enough to handle being immersed in moving water.

lolwut ? We are making jet turbines that can work almost indefinitely at 1400 C immersed in reactive oxidizing exhaust. We have steam turbines in power plants that work at similar temperatures and pressures for decades. No we have no trouble whatsoever building turbines that can deal with moving water. At least not we, humans on Earth in *this* universe. Not sure about yours, though...

Edited February 14, 2014 by MBobrik

[Space Viking]

Given current technology, the biggest challenge behind constructing a surface rover for Venus is electronics. There's microprocessors that can withstand nearly 500°C under development, but until then, the best we got is operating reliably at a maximum of around 300°C. Aside from developing this heat-resistant electronics, we would with current technology either need to research an active cooling system or somehow house the computer system inside a relaying aerial drone. Sensors would also require development.

When it comes to power generation, a typical RTG could work on Venus, albeit limited to a electric production of 30W (as opposed to Curiosity's 120W). Therefore, it would be ideal researching a radioisotope generator using Stirling conversion. With a theoretical output of almost 500W, it could cool down the rover's interior to a workable 250°C. The only real problem left would the shortage on plutonium.

For more information check out this link: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090001338_2008047211.pdf

[AngelLestat]

There is already a design that can last more than 50days on the surface.

In fact there is more than one.

Video:

Design: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090001338_2008047211.pdf

Another missions under develope:

http://www.lpi.usra.edu/vexag/meetings/archive/vexag_9th/augSept11/presentations/ClimateMission.pdf

http://vfm.jpl.nasa.gov/files/Venus+Flagship+Mission+Study+090501-compressed.pdf

Wind rover concept:

Video:

Design: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130010972_2013010229.pdf

It use the low speed (but very dense) winds on the surfuce to move the rover. In this way you can use all the energy at cooling.

High temperature electronics in a few years would not be a problem.

Carbon nanotubes like conductors and uranium oxides like semiconductors is all what we need.

EDIT: spaceviking already post one of my links

[lajoswinkler]

I didn't think of that. PCB's are going to be a problem because all the solder on it will melt right off. Would embedding the electronics in a block of resin with coolant-filled pipes running through it work? The coolant still needs to dump its heat, but it's an alternative to putting them inside a refrigerated cabinet (with all the pressure issues that come with it)

I'm sure alternatives would be made so that no lead-tin solder is used. The problem is with microprocessors.

All they need is a refrigerator that would keep the temperature at some 200°C, it doesn't need to go way down.

I just read this: http://beyondearthlyskies.blogspot.com/2013/05/cooling-venus-rover.html

I think they reference the 50 day rover mentioned before, they speak of putting the electronics in a 10cm sphere insulated by ceramics and actively cooled. Power comes from 7x 250W RTGs (problem 1: not enough plutonium left to do that) mated to stirling engines, the temperature gradient would then be 1200C to 500C (helium as working fluid) and that shakes out to 400-480W of available electrical power. 100W of which would be used for operations (driving, electrics, etc.) and the rest for cooling that electronics-sphere. They would cool it down to 300C.

It all sounds awesomely out of this world, I'd love to see it happen

Wow, I guess it is possible.

Honestly, I was just speculating and never really searched for these things online.

All that would be heavy, though.

I'm thinking Mercury...

Or sodium, like they use as a heat exchange medium in some nuclear powered submarines (haven't checked if it's solid or liquid at the temperatures we're talking about, but something like that).

Sodium would be molten, but instead of sodium, NaK alloy is used.

Might be difficult to make one durable enough. We're having trouble making tidal stream turbines tough enough to handle being immersed in moving water. Keeping it together in that hot soupy atmosphere would be a considerable engineering challenge.

Over and over it keeps coming down to the extreme heat. It speeds up corrosion, things creep, normal lubricants would be useless, electronics hate it, etc, etc.

I expect no corrosion on the surface of Venus. There really isn't a scenario where corrosion plays any role.

Venera probes would stop functioning because they would get into thermal equilibrium with the atmosphere. That's it.

It's funny, but those probes still contain molten metals inside. Solder, zinc... The plastics are probably all charred right now.

[theend3r]

Better ask yourself why don't we have cars that can withstand an average temperature of ca 460 °C, a pressure of 93 atmospheres and drive though lava?

[J.Random]

lolwut ? We are making jet turbines that can work almost indefinitely at 1400 C immersed in reactive oxidizing exhaust. We have steam turbines in power plants that work at similar temperatures and pressures for decades. No we have no trouble whatsoever building turbines that can deal with moving water. At least not we, humans on Earth in *this* universe. Not sure about yours, though...

Yeah, only when Eyjafjallajokull was active, noone risked to send an airplane at that route. Because that's what happens when these turbines get into volcanic ash cloud:

And there should be all kind of crap flying in Venus atmosphere because of 300km/h strong winds, which is stronger than most of Earth tornadoes.

[Kryten]

Yeah, only when Eyjafjallajokull was active, noone risked to send an airplane at that route. Because that's what happens when these turbines get into volcanic ash cloud:

And this would be relevant to a power-generating turbine because...

[MBobrik]

Yeah, only when Eyjafjallajokull was active, noone risked to send an airplane at that route. Because that's what happens when these turbines get into volcanic ash cloud:

Volcanic ash damages jet engines by melting and sticking to the turbine blades. This has nothing to do with my original idea of driving a refrigerator keeping the rover insides cool by a wind turbine

And there should be all kind of crap flying in Venus atmosphere because of 300km/h strong winds, which is stronger than most of Earth tornadoes.

Such high winds are only high up in the superrotating atmosphere. Down on the surface it is just a few km/h.

Edited February 14, 2014 by MBobrik

[lajoswinkler]

And there should be all kind of crap flying in Venus atmosphere because of 300km/h strong winds, which is stronger than most of Earth tornadoes.

300 km/h or 2000 km/h (Neptune) doesn't matter. The probe is carried by the wind so it experiences only a fragment of the relative speed. It's not a tower fixed to the ground which has to endure the whole speed difference.

[AngelLestat]

Volcanic ash damages jet engines by melting and sticking to the turbine blades. This has nothing to do with my original idea of driving a refrigerator keeping the rover insides cool by a wind turbine

Such high winds are only high up in the superrotating atmosphere. Down on the surface it is just a few km/h.

First, it use an electric motor. So no problem with ashes.

Second, Ashes no reach that height. The airplane I guess would fly at 45 km to 55 Km altitude area.

Wind speed is not a problem, becouse you are moving with the wind. And they are pretty constant.

[Blue]

An idea I had was having a "dumb" rover that drives on the surface, which would be controlled by a computerized probe platform blimp/balloon, which would sit in a high point in the atmosphere, tethered to the ground or directly to the rover. The platform would then be able to perform all the necessary operations to keep the rover "thinking" and relaying control instructions from orbit down to the rover, without having to bathe itself in incredibly high temperatures and pressures.

The electronic components that do the "thinking" such as memory or processors are the ones which have comparatively little temperature tolerance, whereas "dumb" parts like motors and transistors could manage the simple tasks of moving the rover around and drilling things without being seriously encumbered by the heat. This way, a rover could operate as long as its parts were functioning, rather than being a temporary device which decisively fails after its computer or motor can take the heat no longer. The biggest limitations would be the logistics of the blimp: whether or not it is or could be tethered, and if it was tethered, how light could one make (possibly several) 50-km guy-wires, deployed from high in the atmosphere.

Edited February 14, 2014 by Blue

[Seret]

lolwut ? We are making jet turbines that can work almost indefinitely at 1400 C immersed in reactive oxidizing exhaust. We have steam turbines in power plants that work at similar temperatures and pressures for decades.

Just because something is ubiquitous, doesn't mean it isn't operating at the edge of what's possible. Gas turbines are continually (and deliberately) operating right on the edge of what the materials will withstand. The technology required (such as single crystal casting and the surface engineering on the blades) is not trivial, it's cutting edge. No, they cannot operate continuously, creep is a huge problem, they're regularly maintained and parts have a very finite life.

No we have no trouble whatsoever building turbines that can deal with moving water. At least not we, humans on Earth in *this* universe. Not sure about yours, though...

I assume from this comment that you don't have any actual experience with tidal stream turbines? They're still under heavy and active development. There's a reason why even countries with enormous tidal resources are still only tentatively deploying experimental systems. A quick search of a decent library (or even Google) for subjects like cavitation and erosion corrosion in tidal stream turbines would show you that yes, in fact, we do have large problems with them. I've seen a turbine pulled up with the blades damn near shredded to stumps after only a couple of months underwater.

We have mastered turbines for hydro (where flow is very tightly controlled) and wind, but you can't just extrapolate from those to soupier fluids. Sorry if you thought we could, but we can't. We're still working on making them durable enough, the problem has proved more difficult than we thought.

As for opearting a wind turbine on Venus, while the atmosphere is somewhere between that faced by a wind or tidal stream turbine in terms of the fluid, the heat is a hugely complicating factor. How exactly would you make a bearing that could operate at 450C? Or a generator? Or the power electronics? This is a non-trivial problem.

[rkman]

An idea I had was having a "dumb" rover that drives on the surface, which would be controlled by a computerized probe platform blimp/balloon,

That's also mentioned in the NASA paper that contains the image of the rover in the Op, the paper is linked in the "terraforming Venus" thread.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090001338_2008047211.pdf

[MBobrik]

No, they cannot operate continuously, creep is a huge problem, they're regularly maintained and parts have a very finite life.

... of 50 000+ hours. which is for space exploration purposes practically indefinitely.

I assume from this comment that you don't have any actual experience with tidal stream turbines? They're still under heavy and active development. There's a reason why even countries with enormous tidal resources are still only tentatively deploying experimental systems. A quick search of a decent library (or even Google) for subjects like cavitation and erosion corrosion in tidal stream turbines would show you that yes, in fact, we do have large problems with them. I've seen a turbine pulled up with the blades damn near shredded to stumps after only a couple of months underwater.

I assume from your comments, that you have a vast experience with seeing problems and roadblocks everywhere at any costs instead of seeking for solutions. Otherwise you would immediately realize that the challenge of tidal stream turbines is how to build huge, up to multi megawatt turbines that can convert weak water currents to electricity efficiently while still being cheap enough to be economically viable. If you had to produce only a few hundred watt, had no price ceiling, and free choice of all possible resistant materials the mankind ever developed... well... let's say this would be one of the technologically less challenging parts of the venus rover.

How exactly would you make a bearing that could operate at 450C? Or a generator? Or the power electronics? This is a non-trivial problem.

That is the difference between us. you are only seeing problems. I am seeking for solutions. So you won't notice that steam turbines work at the same temperature and pressure ranges and similar (reductive, oxygen free ) conditions right now. So bearing design was solved long ago. And the rest, the generator, compressor and gearbox could be inside the low temperature compartment and thus have no temperature problems. But they don't have to be. Stainless steel creep threshold is 565 C so they would do fine even at ambient temperature.

Edited February 15, 2014 by MBobrik

[Seret]

... of 50 000+ hours. which is for space exploration purposes practically indefinitely.

No gas turbine runs that long between overhauls. You're normally looking at somewhere between 1500-5000 hours. At one point due to some issues we were having with Viper 680s we were actually pulling engines every 100 hours. That was a pain in the arse.

I assume from your comments, that you have a vast experience with seeing problems and roadblocks everywhere at any costs instead of seeking for solutions.

Lol, I make no apologies for that, it's a ludicrously common trait amongst engineers. I would go as far to say it's the default setting. Identifying your constraints is a legitimate way to explore a problem space. Non-engineers often find this a very "negative" trait, but that's because they don't recognise that it can be positive too. Ideally any team will have a mix of personality types, but in my experience you probably get about 70% "problem focussed" people on engineering teams.

So bearing design was solved long ago. And the rest, the generator, compressor and gearbox could be inside the low temperature compartment and thus have no temperature problems.

Bearings are fine if they can be cooled. That's problematic in those ambient temperatures, you'd need active cooling. That incurs a power supply, weight and complexity penalty. All of this adds up quickly into a rover that is a considerably more challenging design problem than anything that's been attempted before. Personally I suspect an iteration of current rover designs probably wouldn't work, I'd be inclined to look for something completely novel.

Stainless steel creep threshold is 565 C so they would do fine even at ambient temperature.

Sure, but you can't make everything out of stainless, and some of your rover is necessarily going to be at temps above ambient. What about lubricants? Seals? Insulators? We don't routinely design vehicles to operate at those ambient temps, so I think you're probably underestimating how much of a learning curve is involved.