[Scenario] Aphrodite 4 mission.

[Souper]

In the year 2117, governments were open books who conveyed any and all major information to everyone. While humanity has learned to put violence aside, they also have RAMPED up their game in the field of space travel.

An anomalous object at the bottom of the deepest cave of Venus emits VERY strong signals that can be heard all the way from Earth that need pure, alive, meaty humans in order to be investigated (because robotic craft can't receive signals from inside a cave).

so, how can this go down?

22ND CENTURY TECHNOLOGY:

super alloy called Rendium (it can withstand 3000 C temperature for 8 hours before finally melting)

crystal-clear melting proof pressure-resistant glass (originally devised for military use)

all near-future tech you've ever heard of

[xenomorph555]

In the year 2117, governments were open books who conveyed any and all major information to everyone. While humanity has learned to put violence aside, they also have RAMPED up their game in the field of space travel.

An anomalous object at the bottom of the deepest cave of Venus emits VERY strong signals that can be heard all the way from Earth that need pure, alive, meaty humans in order to be investigated (because robotic craft can't receive signals from inside a cave).

so, how can this go down?

22ND CENTURY TECHNOLOGY:

super alloy called Rendium (it can withstand 3000 C temperature for 8 hours before finally melting)

crystal-clear melting proof pressure-resistant glass (originally devised for military use)

all near-future tech you've ever heard of

Please take this back to the fan fiction thread.

[Nibb31]

all near-future tech you've ever heard of

Scotty builds super interplanetary transporter and beams R2D2 to the surface of Venus to study the wreck of the Nostromo.

Why did you put this in Science Labs ?

[Souper]

Because, i need excuses to put people on Venus.

[Idobox]

Titanium, fused quartz glass and PTFE are perfectly good materials to build a Venus lander that would survive for years, no need for unobtainium.

You keep the humans in orbit, and send a robotic probe down there.

Structural parts will pose no problem, electronics might require some cooling, all power electronics can be done with vacuum tubes and will have no problem with the heat.

For power, the best would probably to use fuel cells. Chemical batteries usually don't like high temperatures too much, RTGs get crappy efficiency in hot atmospheres, beta and alphavoltaics just don't have the power density. With today's technology, I would store fuel as metal hydride and for oxygen I would use a gas generator. The ISS uses lithium perchlorate that decomposes around 400°C, so that would be unsuitable, but there is more stable stuff. You could also imagine a fuel cell reacting with atmospheric CO2 or sulphuric acid (more reactive, a lot less concentrated).

Even better, you could develop a aluminium/H2SO4 fuel cell on the model of air-metal batteries, using molten salt or something as the electrolyte.

To deal with pressure, the best way would be to keep the bare minimum in a pressure vessel, and coat everything else in PTFE or metal fluoride: the pressure can't crush you if it is equalized, and superhot sulphuric acid is not the worst chemical we deal with on industrial scales.

Electric motors could not use permanent magnets with the temperature, but once again, copper, titanium and PTFE and perfectly fine in these conditions, and PTFE is an excellent insulator, and also has extremely low friction coefficient, so you could have excellent induction or switched motors.

The last issue is the many sensors. But once again, 500°C corrosive and high pressure atmosphere might sound like hell, but many industrial processes have it worse. And if you need some stuff that cannot be done to survive the conditions, you can always encase it and actively cool it.

Edited December 20, 2014 by Idobox

[Idobox]

Actually, we could have Venus rovers with today's technology, only limited by power supply (probably very little sunlight at the bottom, and RTGs won't be very good there). So why doesn't anybody send some? It doesn't have to be as complex and expensive as curiosity.

Also, there is supposedly a lot of wind on Venus, which given the density would be more comparable to strong water currents. I suppose wind power would be an option. I want windmill powered, PTFE coated titanium rovers on Venus.

[NERVAfan]

Actually, we could have Venus rovers with today's technology, only limited by power supply (probably very little sunlight at the bottom, and RTGs won't be very good there). So why doesn't anybody send some? It doesn't have to be as complex and expensive as curiosity.

Because there isn't really all that much interest in Venus compared to Mars, and a Venus rover would have an extremely short lifetime and wouldn't be cost effective (it wouldn't last long enough to use the ability to "rove"). It's not just power limitations but surviving the temperature.

[lajoswinkler]

Two things people need to learn:

1. heat =/= temperature

2. object on Venus surface is not subjected to corrosive atmosphere because acids are high up and never reaching ground; surface is extremely dry fluid (not liquid!) made of mostly carbon dioxide in a supercritical fluid state

92 atmospheres of pressure is not much. The difficulty Venus represents is that you can't cool down your machinery as the environment is so hot. If you want a refrigeration system that would use the atmosphere as a cold sink, your primary heat source needs to be way hotter.

[Idobox]

The temperature is less than 500°C. Sure it's hot, but not crazy hot, most parts of a well built probe can perfectly deal with that. Old dumb steel and copper can, many plastics can, glass can, ceramics won't even notice the difference. Transistors can be made to work at those temperatures, but it would be very difficult to dump heat, which is why I suggest thermionic devices for power applications.

The only parts that really need cooling are microelectronics, and maybe some sensors. Keeping them cool with a heat pump is totally feasible.

Lajoswinkler, are you suggesting a heat machine as the power source? RTGs, which are the only such power source used for probes, won't have a good efficiency, which is why I spent some time proposing other power sources that won't mind the temperature.

[K^2]

Lajoswinkler, are you suggesting a heat machine as the power source?

There aren't a lot of options. Batteries won't last that long. Solar isn't available. The only power source we have that will work on Venus and isn't technically a heat machine is a fuel cell. But that still has all the same problems. It needs to operate in a certain temperature range and produces considerable waste heat that you have to get rid of.

[NERVAfan]

2. object on Venus surface is not subjected to corrosive atmosphere because acids are high up and never reaching ground; surface is extremely dry fluid (not liquid!) made of mostly carbon dioxide in a supercritical fluid state

Right

92 atmospheres of pressure is not much.

Yeah, undersea machines deal with pressures like that (1 atm is about 10m underwater, so that's about what you'd get 1km down in the ocean).

The difficulty Venus represents is that you can't cool down your machinery as the environment is so hot. If you want a refrigeration system that would use the atmosphere as a cold sink, your primary heat source needs to be way hotter.

Exactly.

There aren't a lot of options. Batteries won't last that long. Solar isn't available. The only power source we have that will work on Venus and isn't technically a heat machine is a fuel cell. But that still has all the same problems. It needs to operate in a certain temperature range and produces considerable waste heat that you have to get rid of.

Well, there was a recent wind power proposal for Venus rovers. Wind speed at Venus's surface is low but the high density of the atmosphere means it has significant force.

[Idobox]

There aren't a lot of options. Batteries won't last that long. Solar isn't available. The only power source we have that will work on Venus and isn't technically a heat machine is a fuel cell. But that still has all the same problems. It needs to operate in a certain temperature range and produces considerable waste heat that you have to get rid of.

On the contrary. Solid Oxide Fuel Cells have typical operating temperatures between 800-1000°C, molten carbonate fuel cells work at 650°C, so the 470°C superfluid CO2 would be an excellent cold sink for one. Actually, you could even slap a Peltier elements around the fuel cell to get a few more percent of efficiency.

By the way, while looking for fuel cell operating temperatures, I found a bit (but not much) on carbon fuel cells. Apparently, you can use carbon or carbon rich materials in either SOFC and MCFC, which makes fuel storage much easier. I haven't checked, but it might be possible to use with other oxidizers than O2.

And then, there's wind.

[lajoswinkler]

The temperature is less than 500°C. Sure it's hot, but not crazy hot, most parts of a well built probe can perfectly deal with that. Old dumb steel and copper can, many plastics can, glass can, ceramics won't even notice the difference. Transistors can be made to work at those temperatures, but it would be very difficult to dump heat, which is why I suggest thermionic devices for power applications.

The only parts that really need cooling are microelectronics, and maybe some sensors. Keeping them cool with a heat pump is totally feasible.

Lajoswinkler, are you suggesting a heat machine as the power source? RTGs, which are the only such power source used for probes, won't have a good efficiency, which is why I spent some time proposing other power sources that won't mind the temperature.

Any machine will heat itself up and unless that heat is being carried away, it will build up and finally cause a failure. For example a blender in Earth's atmosphere readily dissipates heat because the atmosphere is cold enough and the heat output of the machine is sufficiently low.

When you have >450 °C highly thermally conducting supercritical atmosphere and strong thermal insulators encasing the probe, usual heat outputs of machines will quickly become a huge problem because it can't get out.

The only two approaches are either building the microprocessor technology from the scratch so it could work at temperatures slightly above those, which is insanely expensive, or building a refrigeration system. That means a hot tank a lot hotter than the atmosphere, but not only that - it also needs to be able to supply enough heat so it would do enough work to dump the heat creeping in the probe. That would be very, very difficult. An RTG would be too weak for such operation. An actual nuclear fission reactor tolerable of using such hot atmosphere as a cold sink would have to be made.

A huge engineering problem, obviously.