China's Space Program News Thread

[chuck731]

As an interesting aside, latest research suggests one of the two soviet lunahod rovers paradoxically died of overheating. Lunahod appearently still used old style electronics that consumed much power and put out a lot of waste heat. The rover actually had a cooling system with radiators to help the rover keep cool during the day. Appearently lunahod accidentally brushed hard against a large rock during its travels, which dislodged a large load of lunar soil that had been on the rock. The soil fell on the lunahod, covered its radiator, and the rover died of a heat stroke.

Now back to Chinese space program.

 

[Quickie]

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.



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.

With proper insulation, the Mars probes/rovers could retain enough heat through the shorter Martian night without having to depend too much on additional heat provided by a nuclear source. A moon night is about 14*24/11 = 30 times longer than that on Mars in addition to the moon's colder night temperature (-233 degree C) so that the heat energy required may be approximately 60 times as much.

 

[chuck731]

With proper insulation, the Mars probes/rovers could retain enough heat through the shorter Martian night without having to depend too much on additional heat provided by a nuclear source. A moon night is about 14*24/11 = 30 times longer than that on Mars in addition to the moon's colder night temperature (-233 degree C) so that the heat energy required may be approximately 60 times as much.

Since rate of heat loss by radiation is approximately equal to the 4th power of temperature difference between emitter and absorber, the heat energy required to make up for heat loss while maintaining same temperature on the moon for a given length of time is likely to be many times higher than that required on mars. So factoring in length of lunar night being 30 times longer than Martian night, the amount of heat energy required to keep a probe on the moon alive over a lunar night is likely to be many hundreds of times what it would take to do so over a Martian night. That could easily explain why the Chinese didn't simply use a battery operated heater, charged during the day from solar panels, to allow the probe to survive as many nights as other aspects of the rover remain viable.

I am interested in knowing just how big the radio thermal heat source on Yutu is. I would not be surprised if it needed to be fairly large just to keep the rover alive for 3 nights. The amount of the stuff needed to keep the probe alive for just three lunar nights might be a reason why they didn't design the probe for longer life. Either that or an even larger thermal source needed for longer life would generate so much heat initially that it would overheat the probe during the day, or would require radiator and other weights to keep rover temperature under control during the day.

 

[xiabonan]

My guess is that the solar panels couldn't properly unfold and thus will be exposed to the harsh conditions of the lunar night, which it isn't designed to. Hence Yutu's Weibo said ".....maybe I couldn't make it through this lunar night" (Yutu's official weibo are all posted using first person pronoun).

I want to share it's latest weibo here, if you guys don't mind.

"The Sun has set here, and temperature is dropping fast. I've said a lot today, but nonetheless I still feel it's not enough. Hey I want to tell you guys a secret: actually I don't feel extremely sad. I, just like many other protagonists, experienced some problems in my own journey, my own adventure story. Thanks to @POCKN for making this picture, which again reminds me, even if that I can't go to sleep properly, hey, at least, for the first time and last time, I can enjoy the magnificent view of an earth-rise!"

 

[Jeff Head]

With proper insulation, the Mars probes/rovers could retain enough heat through the shorter Martian night without having to depend too much on additional heat provided by a nuclear source.

The only source is the plutonium source. The sole source of heat and electricity for the Mars Viking 1 and Viking 2, and the Curiosity are their RTGs and the Plutonium in them. Without them, their would be no electricity and no heat. None.

As to the Yutu, my understanding is that the absolute major source of power are the solar panels and that the supplemental Plutonium power source is very small and is only meant to keep the powered down components from falling below negative 40 degrees C during the lunar night so they can be revived once the lunar night is over.

You may want to check me on that...but that is my understanding.

 

[Quickie]

Really, I haven't read much about the Yutu. Just want to add that having to endure a temperature variation of between -40 degrees C and > 100 degrees C between night and day will have big negative impact on the reliability of its systems, for example the electronics. The reason why they didn't reduce the temperature variation further could be because doing so would require too big of a power source that's reasonably possible and, instead of fighting the extreme low temperature during moon night (which by the way is not that bad on Mars) , they end up going along with it and opting for hibernating at a lower temperature of about -40 degree C, compromising the rover systems reliability in the longer term.

 

[Engineer]

Whilte it is more difficult to get to Mars, it is much more difficult to survive on the Moon. In terms of temperature, being on Mars is not so different than being on Antaratica. On the Moon however, the temperature range doubles that on Mars. The extreme duration of lunar day and night makes things even worse. Then there are other factors on the Moon like extreme radiation, and the extreme fine dust that would just get inside anything even with seals.

 

[Blackstone]

Deleted.

 

[TerraN_EmpirE]

Wrong thread Blackstone.

 

[solarz]

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China says its first lunar rover is experiencing mechanical problems, a setback for its burgeoning space program that in recent years has conducted space walks and placed a space station in orbit.

The six-wheeled Yutu vehicle began operating last month after making the first soft landing on the moon by a space probe in 37 years. It was designed to roam the lunar surface for three months while surveying for natural resources and sending back data, along with its stationary lander, Chang'e 3.

The mission has been a popular success for China's space program and the rover has attracted more than 150,000 followers on its microblog. It last posted on Saturday saying repairs were underway and hope was not lost.

"Sorry to make you all sad. The engineers and I haven't given up yet," the posting said.

News of the rover's troubles were splashed across newspapers on Monday and even featured at the Foreign Ministry's daily briefing, with spokesman Qin Gang expressing hope that Yutu could "return to normal."

The mechanical problems appeared to be related to the solar-powered probe's process for shutting down for the lunar night, which lasts more than two weeks. The temperature during that time drops to minus 180 degrees Celsius.

The probe had survived its first lunar night shutdown, during which it is unable to generate energy from its solar panels and relies on a radioactive power source to keep its delicate sensors and other equipment intact.

The 140-kilogram rover was traversing a relatively flat part of the moon known as Sinus Iridum, or the Bay of Rainbows, at a speed of 200 metres per hour. The landing vehicle, which has already shut down for the lunar night, is designed to conduct scientific examinations for one year.

Online speculation focused on the possibility of lunar dust having blocked one of the solar panels from folding inward, leaving equipment exposed to the dangerously low temperatures. It won't be known if the probe is able to function again until after the two-week break.

China's space program has made steady progress since the country launched its first manned spacecraft in 2003. It has launched a lunar orbiter, conducted space walks, and put into orbit a prototype space station, to be replaced by a permanent station at the end of the decade.

Already a source of enormous national pride, the space program has increasingly sought to connect with the public through social media and educational outreach. China's second woman in space, Wang Yaping, conducted China's first space classroom to students nationwide from the prototype space station, the Tiangong.

"Yutu, or "Jade Rabbit," is named after a mythological Chinese animal said to live on the moon.

This is the most objective article I could find. Some of the other articles on this subject were almost oozing giddiness.