[FPSPACE] How to Keep a Venus Rover Cool

[LARRY KLAES]

http://www.universetoday.com/2007/11/15/how-to-keep-a-venus-rover-cool/

How to Keep a Venus Rover Cool

Written by Nicholos Wethington

In comparison to a mission to Venus, missions to Mars or the Moon are a 
cakewalk. With temperatures exceeding 450ºC (840ºF) and pressures over 92 
times that of the surface of the Earth, landing a rover on the surface of 
Venus is quite a feat. This, however, is exactly what a research and 
development team at the NASA John Glenn Research Center hopes to accomplish.

Venus has been explored by a number of different missions, but there is a 
lot of science yet to be done on the planet.

"Understanding the atmosphere, climate, geology, and history of Venus could 
shed considerable light on our understanding of our own home planet. Yet the 
surface of Venus is the most hostile operating environment of any of the 
solid-surface planets in the solar system," wrote Dr. Geoffrey Landis of the 
NASA John Glenn Research Center.

The extreme conditions on Venus make traditional rover technology 
impossible: the heat and pressure combined wreak havoc on any electronic 
components, and the atmosphere of Venus, mostly composed of carbon dioxide 
and sulfuric acid, is highly corrosive on metal parts. And if this weren't 
enough, the thick atmosphere makes the light conditions on the surface like 
a rainy day on Earth, which limits the potential of solar energy.

To solve the problem of putting electronics on the surface, the team will 
split the mission into two: a rover that will have limited electronic 
components in pressurized chamber cooled to under 300ºC (570ºF), and an 
airplane that will fly in the middle atmosphere of the planet, where the 
temperature is more moderate and the pressure not as great. The airplane 
will contain most of the more sensitive electrical components like 
computers, and will assist in relaying all the information back to Earth.

The Russian Venera lander to last the longest on the surface of Venus 
operated for a mere two hours before being crushed, but the rover for this 
mission will be designed to last more than 50 days.

Extreme conditions call for extreme technology; the team analyzed the 
possibility of using a number of different sources of energy, from solar to 
nuclear to microwave beaming. Solar power just can't provide the energy 
necessary to run the rover and cool everything down, and microwave beaming 
energy from the airplane – which would collect solar energy – isn't feasible 
because of how new the technology is.

This leaves nuclear power, something that has been used in past missions 
such as Galileo, Voyager, the current Cassini probe. To power the rover with 
nuclear energy, though, there is a twist: the heat produced by bricks of 
Plutonium will power a Stirling engine, an engine that uses the pressure 
difference between two chambers to produce mechanical energy with very high 
efficiency. This mechanical energy can be used to power the wheels directly, 
or transferred to electrical energy for the electrical and cooling systems, 
and the technology is being adapted to work on Venus.

"We've been working on Stirling technology for many years. The project 
reported was a project to design a Stirling specifically for Venus – which 
makes for a very different design in some ways; notably in that the heat 
rejection temperature is extremely hot – but we are building from existing 
technology, not developing it from scratch," wrote Dr. Landis

The airplane would study the atmospheric conditions and Venus' electric 
field, while the rover would place seismic stations and study surface 
conditions. A camera is almost definite on the airplane, and while it would 
be difficult to put a camera on the rover, it is not entirely out of the 
question.

When can you expect to see images of the surface, or hear more about the 
sulfuric acid clouds that envelop the planet?

"It's a mission concept study so far, not a funded mission, so it's not 
actually scheduled to take place. However, there's a lot of interest in 
flying it in the 2015-2020 time frame," said Dr. Landis.

Source: Acta Astronautica