NASA Designed a Low-Tech Rover to Survive Venus
wired.com
wired.com
When the rover starts to run out of coolant it would inflate the airbag, rise up to about the one atmosphere level (50km?), use solar power to replace the coolant, then descend again for another ground mission. And since the venusian atmosphere is about 5% nitrogen, nitrogen seems like the ideal coolant, and, on top of that, it's probably the ideal lift gas for Venus as well. This is because pure gaseous nitrogen is considerably less dense than gaseous carbon dioxide.
That sounds like a horrible idea.
NASA's proposal:
https://en.m.wikipedia.org/wiki/High_Altitude_Venus_Operatio...
I am fond of the name HAVOC.
> Thermal inertia and the transfer of heat by winds in the lower atmosphere mean that the temperature of Venus's surface does not vary significantly between the night and day sides, despite Venus's extremely slow rotation. Winds at the surface are slow, moving at a few kilometres per hour, but because of the high density of the atmosphere at the surface, they exert a significant amount of force against obstructions, and transport dust and small stones across the surface. This alone would make it difficult for a human to walk through, even if the heat, pressure, and lack of oxygen were not a problem.
...
> The only appreciable variation in temperature occurs with altitude. The highest point on Venus, Maxwell Montes, is therefore the coolest point on Venus, with a temperature of about 655 K (380 °C; 715 °F) and an atmospheric pressure of about 4.5 MPa (45 bar).
...
> Strong 300 km/h (185 mph) winds at the cloud tops go around Venus about every four to five Earth days.
https://en.wikipedia.org/wiki/Venus#Atmosphere_and_climate
Given the thickness of the atmosphere, maybe the most sensible form of locomotion on the surface is to just let the wind carry you along...
That got me curious how slow Venus rotates and apparently it takes 243 Earth days for a single day to pass there. Which is even more amazing considering it takes Venus only 224 Earth days to orbit Sun - a single day there takes more than 1 year! Developing inter-planetary software would have interesting surprises...
https://www.nasa.gov/feature/jpl/a-clockwork-rover-for-venus
The WIRED article has errors. They got the PI's name wrong. They also say this about communications:
"the Venus rover will use a simple optical reflector to transmit its data to orbiting satellites by flashing radar light like morse code"
This is misleading in a couple of ways. The rover in the link above appears to use radar targets which turn on wheels; an orbiter would bounce radio off the target to determine their configuration.
http://news.uark.edu/articles/39133/ozark-integrated-circuit... http://www.ozarkic.com/our-services/high-temperature/
Really? Is that counterintuitive? If you talk to car or motorcycle overland travellers who traverse deserts and remote mountains, you'll find a preference for simple designs that minimize part counts and electronics (for fuel pump, ABS, suspension...) to improve reliability, often at the cost of performance and efficiency.
https://en.wikipedia.org/wiki/Venera#Venera_camera_successes...
> The Venera 9 and 10 landers had two cameras each. Only one functioned because the lens covers failed to separate from the second camera on each lander. The design was changed for Venera 11 and 12, but this change made the problem worse and all cameras failed on those missions. Venera 13 and 14 were the only landers on which all cameras worked properly; although unfortunately, the titanium lens cap on Venera 14 landed precisely on the area which was targeted by the soil compression probe.
They attempted to over-engineer the thing further by adding explosive bolts to it. That also ended in failure (explosives failed to explode as they decomposed long before they were fired).
Finally, a dumb solution was devised: to make the cap to fit inside the bezel and be made from titanium. That finally solved the issue.
As the aluminium bezel expanded, the cap loosened up, falling out under its own weight.
But that didn't account for another instrument sampling area being right under the camera, where the cap were to fall.
Curiously, the earliest out-of-lab digital photography that I'm aware of was from that Russian probe to Venus in the 70's, which lasted less than an hour in the hostile atmosphere.
Photos: https://nssdc.gsfc.nasa.gov/imgcat/html/mission_page/VN_Vene...
Put all of them in a single strong container instead of using lots of fragile glass in a high pressure environment. And you won't need to heat the emitter, saving weight.
If there are, it might feel completely at home on Venus.
Google "Exhaust heat riser"
A spring that provides many years of useful service when exposed to high temperatures isn't a very exotic part. NASA probably isn't trying to make it go 5yr/50,000mi without failing so they can probably come up with something that works well for the duration of the mission.
That said, a bit of searching did find Iconel 718 springs which are good up to 1000 degrees. Not a lot of margin but probably workable. Since people has developed techniques for 3D printing Iconel 718 it seems like that problem at least is workable.
This seems odd to me - Venus has high wind speeds in the upper atmosphere, but on the surface the winds are only one or two m/s. Is that enough to wind a spring?
> Savonius turbines are used whenever cost or reliability is much more important than efficiency.
The German article is a bit more detailed and claims that Savonius tubines are effective at speeds as low as 2m/s and produce high torque even then. Maybe the high pressure on Venus increases this effect?
All the samples you need, with only a part of the pressure and none of the toxic atmosphere?
I know it would not make scenic photos- and take forever to get anywhere- but it would last.
Also that still leaves dealing with the tailings.