[FPSPACE] How to Keep a Venus Rover Cool
ljk4 at msn.com
Fri Nov 16 11:51:24 EST 2007
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
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
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