China's Space Program News Thread
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So far very little details have been provided.
Well, I hope they fix it too. Hope it is just software and something they can fix remotely. They have been providing some outstanding pictures, and I know they probably have a lot of experiments yet to perform.
Okay, then, continuing on with the Chinese space program.
Here's an outstanding picture of the Chinese Yutu rover, heading south from the Chang 3 lander.
It will be very interesting to see what type of longevity the Yutu has. For example, will it still be working and transmitting and performing experiments ten years from now like the NASA Opportunity Rover on Mars is after that long on the Martian surface? Time will tell.
The lunar environment is much harsher than that Martian environment in terms of hard radiation, temperature extreme, and prevalence and abrasiveness of static electrically levitates dust. I doubt either opportunity or yutu could last very long on the moon.
Yes, the Lunar environment is a harsh environment.
Which makes the operation of the Russian Lunokhod I rover all the more amazing in 1970-1971.
During its 322 days of operations, it travelled 10,540 meters or over 6 1/2 miles. It sent back over 20,000 images and over 200 high-resolution panoramas. It performed 25 lunar soil analyses with its RIFMA x-ray fluorescence spectrometer and used its penetrometer at 500 different locations, before it finally went silent on September 14, 1971. It holds the longevity record on the moon to this day...and it was the first rover to land on the moon.
Of course, this also does not detract from the amazing record of the NASA rover Opportunity on Mars, which has been going for an astonishing ten years and it still functioning. Despite a not as harsh environment, it is still a very difficult environment and the equipment has been operating far, far beyond what it was expected to operate, or designed for.
We can only hope that the Yutu's current issue gets resolved and that it then goes on to break the current record on the moon. I honestly hope it does.
Well, Chuck, Opportunity was not designed for the moon, so of course it would not last long there.
But Yutu was designed for the lunar environment, and is currently on the moon. So I expect if they overcome the current glitch, that there is every reason to hope it will last for a good while in the environment it was designed for.
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Rovers can often function with mechanical abnormalities. I will guess a wheel motor is the most likely place for a mechanical fault to develop. It is close to lunar surface subject to the extremely abrasive and extremely fine dust being thrown up onto it while driving.
Since yutu wheels are driven individually by separate motors, if the fault is with one or two wheel motor it need not stop the mission.
I wonder if the Chinese has an engineering copy of the yutu somewhere on earth for use in trying to create conditions leading to duplication if actual telemetry readings from the real yutu, in order to better analyze any issue arising in the course of the rover operation on lunar surface.
Yutu, unlike rovers on mars, needs to expend nonreplenishable consumables - plutonium - to survive extreme low temperatures in lunar night. The engineers designed the rover to survive 3 nights. I am guessing that's how long the plutonium will take to decay to a point where it can no longer keep the rover electronics within survivable temperature ranges at night.
Uh, Chuck, actually the Viking 1 and Viking 2 landers from the 1970s, and the current Curiosity Rover which landed in August 2012 on Mars, also use Plutonium.
Curiosity is powered by what is known as a radioisotope thermoelectric generator (RTG), just like the successful Viking 1 and Viking 2 Mars rovers in 1976, albeit newer and more advanced than those older models.
These generators produce electricity from the decay of non-fissile isotopes of plutonium-238. Heat given off by the decay of this isotope is converted into electricity by thermocouples, which provides constant power during all seasons and through the day and night. Waste heat is used via pipes to warm the rover's systems, freeing electrical power to run the vehicle itself and its instrumentation. Curiosity's is fueled by 11 pounds of plutonium-238 dioxide which was supplied to NASA by the U.S. Department of Energy.
The Opportunity and Spirit rovers which landed in January 2004, on the other hand, were (in Spirit's case), and are (in Opportunity's case) powered by Solar arrays during the Martian day while rechargeable lithium ion batteries store energy for use during the Martian night.
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No one is disputing radio thermal batteries are used to generate electrical power for landers and one probe on mars. The key is rovers are mars clearly do not need to use radioactive thermal source to provide the heat needed to keep electronics within survivable temperature ranges in Martian night, which, due to Martian night being only 11 hours long and Martian atmosphere still having some heat retaining capability, never gets nearly as cold as it does on the moon, where the night is 14 days long, and there is effectively no atmosphere, and little else but thermal inertia and possibly earthshine, to keep surface temperatures from steadily equilibrating with cosmic back ground radiation.
So all lunar probes designed to survive lunar nights needs a internal heat source to keep its electronics from being destroyed by the cold during each 14 day long lunar night.
Yutu's expected life is explicitly given in terms numbers of lunar nights - 3. This suggests that's how long the internal plutonium heat sources can last.
Actually, they do. At the Curiosity landing site, and in the area where it operates the swing in atmospheric temperatures vary from -3º Celsius (26º Fahrenheit) in the day to -96º Celsius (-140º Fahrenheit) at night, which would negatively impact its electronics without the use of heating protection provided by systems onboard the Curiosity.
Anyhow, my comment was simply in response to you statement.
Chuck said:
The fact is, the Viking I, the Viking 2, and the Curioisity, all of which operate on Mars, use nonreplenishable Plutonium to power them and to provide the waste heat they need to warm their systems so they can survive, night and day on Mars. That's all.
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