Venus rovers?

[lpetrich]

Of the Earth's two neighboring planets, Venus has not been explored nearly as much as Mars has, despite the two planets having similar accessibility: close amounts of delta-V needed to get there (a few km/s) and close travel time (6 months vs. 9 months for a minimum-energy orbit). Though Mars is not very habitable by human standards, its surface conditions are easily tolerated by space-capable hardware. Venus is another story. The planet has a superthick atmosphere that is superhot at the planet's surface: pressure = 93 bar, temperature = 450 C / 840 F, composition = 96.5% CO2, 3.5% N2, much smaller amounts of other gases.

The longest that any spacecraft has been active there is 127 minutes, by Venera 13.


A Clockwork Rover for Venus | NASA -- proposing a mostly-mechanical rover with a mechanical control computer instead of an electronic one. It would have parallelogram-shaped tank treads much like WWI tanks, it would be powered by a Savonius wind turbine, and it would move some radar targets on top of it for an orbiter to observe with radar.

Windsurfing on a Wicked World | NASA -- a rover with a sail.

But one part of the Landis NIAC study is focused on using wind force on Venus as a propulsive nudge. While the winds at the surface of Venus are low (under one meter per second, or just a little over two miles per hour), at Venus pressure, even low wind speeds develop significant force, he explains.

"A sail rover would be extraordinary for Venus. The sail has only two moving parts-just to set the sail and set the steering position-and that doesn't require a lot of power. There's no power required to actually drive," says Landis.

 

[lpetrich]

Though mechanical components are not much of a problem, I think that a purely mechanical rover would be impractical. Being mechanical would severely limit what data that it could return. One needs electronic components for a lot of data, especially imaging. So we must consider electronic components.

It would be difficult to run a refrigerator, so one must consider components that can survive Venusian temperatures. From High-Temperature Electronics Pose Design and Reliability Challenges | Analog Devices and Extreme-Temperature Electronics (Tutorial - Part 1), most electronic components can tolerate temperatures up to 150 - 200 C. But from the tutorial:

On the high end, "laboratory" operation of discrete semiconductor devices has been reported at temperatures as high as about +700°C (for a diamond Schottky diode) and 650°C (for a SiC MOSFET). Integrated circuits based on Si and GaAs have operated to +400−500°C. Si ICs have been reported to operate at +300°C for 1000 hours or longer.

But NASA is working on silicon carbide (SiC) electronics components: Silicon Carbide Electronics and Sensors With results like Demonstration of 4H-SiC Digital Integrated Circuits Above 800 °C - IEEE Journals & Magazine and NASA Demonstrates Electronics for Longer Venus Surface Missions | NASA.

 

[barbos]

Yes, I thought about SiC too. Mechanical "electronics" is insane idea.
SiC is ceramic with very large bandgap and can be used in space without any cooling or protection and on earth it is limited by material of the packaging.

 

[skepticalbip]

I would think that going back to vacuum tube circuitry would make it more hearty at those temperatures.

And then wasn't there talk at one time about a probe that floated in the atmosphere at an altitude where it would be much cooler? It could give us information about the atmosphere and sample for signs of life in the atmosphere.

 

[lpetrich]

I would think that going back to vacuum tube circuitry would make it more hearty at those temperatures.

A big problem is the electricity consumption of their filaments. That makes them unusable for low-power duty.

And then wasn't there talk at one time about a probe that floated in the atmosphere at an altitude where it would be much cooler? It could give us information about the atmosphere and sample for signs of life in the atmosphere.

Venus Balloons Overview -- several Venusian balloon missions have been proposed and two have been flown:  Vega program,  Aerobot. One of the balloons lasted for nearly two days until its batteries died.

 

[bilby]

I would think that going back to vacuum tube circuitry would make it more hearty at those temperatures.

Good luck designing a lightweight tube that can sustain a decent vacuum against a 93 bar external pressure.

 

[skepticalbip]

I would think that going back to vacuum tube circuitry would make it more hearty at those temperatures.

Good luck designing a lightweight tube that can sustain a decent vacuum against a 93 bar external pressure.

I wouldn't think weight would be that much of a problem. The Mars rover has a mass of almost a metric ton. A five or even ten Kg electronics package added shouldn't be that big a problem. I think lpetrich pointed out a more serious problem with the idea, power consumption.

 

[Loren Pechtel]

I would think that going back to vacuum tube circuitry would make it more hearty at those temperatures.

Good luck designing a lightweight tube that can sustain a decent vacuum against a 93 bar external pressure.

Long ago they build tubes that could withstand 15,000g accelerations.

 

[DBT]

The atmosphere should be investigated, given that there is a possibility of microbial life at 50 km altitude;

''But there’s another possibility. High up in the atmosphere of Venus, at an altitude of 50 km, the air pressure and temperature get to the point that they’re very similar to Earth. In fact, at this altitude, it’s the most Earthlike place in the whole Solar System. Some scientists think that there could be microbial life high up in the atmosphere of Venus.''

 

[lpetrich]

That's an interesting possibility, but it has a very serious difficulty, if the one known example of a biota is any guide. Dependence on minerals, as they are commonly called in human nutrition. These are elements without geochemically plausible volatile compounds, elements like phosphorus and several metals, though they all occur in oxidized form. Elements like Na, K, Mg, Ca, V, Mn, Fe, Co, Ni, Cu, Zn, Mo, etc. Of these, iron is involved in redox metabolism, alternating between Fe++ and Fe+++.

Venus's atmosphere has C, O, N, S, H, Cl, F, and noble gases He, Ne, Ar.

One might be able to substitute sulfates or carboxylic acids for phosphates, and amines for metal ions, but I don't know how well that might work.

Most organic acids are carboxylic acids, and the best-known one of them is acetic acid, the vinegar acid.

 

[DBT]

It seems unlikely for the reasons you give, but there is at least some evidence;

''The new paper makes a strong case for that scenario, analyzing the conditions in the planet’s sky and finding them hospitable to biology. The first two boxes for sustaining life—tolerable temperature and pressure—are easily checked. Thirty miles above ground, Venus’s air pressure is roughly equivalent to the 15 pounds per square inch on the ground on Earth. The temperature, meantime, is a hot but survivable 140° F (60° C).

The chemistry of Venus’ atmosphere is decidedly different from Earth’s: Principally sulfuric acid, carbon dioxide and water droplets. But different is not necessarily deadly.

“On Earth, we know that life can thrive in very acidic conditions, can feed on carbon dioxide, and produce sulfuric acid,” said Rakesh Mogul, a co-author of the paper and a professor of biological chemistry at California State Polytechnic University, Pomona, in a statement that accompanied the paper’s release. Indeed, if life on Earth has proven anything, it’s that it can survive in exceedingly unlikely places—in boiling hot springs and hydrothermal vents, and locked in permafrost. All of those organisms can serve for models for extraterrestrial life.

Even more compelling, argue the authors, are dark patches in Venus’s atmosphere that change shape, size and position over time, but never disappear completely. Discovered in the early part of the 20th century, the patches had long been a mystery, but modern-day analyses have shown them to be made principally of particles that closely match the size of common Earthly bacteria. What’s more, the spectra of light the Venusian particles absorb closely match the spectra absorbed by those bacteria. Mogul and lead author Sanjay Limaye, of the University of Wisconsin, Madison, compare the atmospheric blooms to algae blooms in the oceans on Earth, arguing that they could be just as biologically robust.''