China's Space Program News Thread

[Equation]

Here is some specs on the Chinese Lunar-based Ultraviolet Telescope

The Lunar-based Ultraviolet Telescope (LUT) is a funded lunar-based ultraviolet telescope dedicated to continuously monitoring variable stars for as long as dozens of days and performing low Galactic latitude sky surveys. The slow and smooth spin of the Moon makes its step by step pointing strategy possible. A flat mirror mounted on a gimbal mount is configured to enlarge the sky coverage of the LUT. A Ritchey-Chrétien telescope with a Nasmyth focus configuration is adopted to reduce the total length of the system. A UV enhanced back illuminated AIMO CCD 47-20 chip together with the low noise electric design will minimize the instrumental influence on the system. The preliminary proposal for astrometric calibration and photometric calibration are also presented.

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[chuck731]

One can test it in a large deep pool that can control the water currents like NASA has done for many of it's space projects. A model of the rover and landing can be made water proof for certain testings and control measurements.

What NASA did in the pool was to train astronauts for zero G extra-vehicular activity. I don't think they were testing space going equipment per se.

 

[broadsword]

Pool is more suitable for testing weightlessness as in space rather than ground vehicles.

 

[escobar]

Visit at Beijing Aerospace Command and Control Center

[video=youtube;ilmDvNW4gao]http://www.youtube.com/watch?v=ilmDvNW4gao#t=162[/video]

The new 65m Radio Telescope at shanghai pick up CE-3 signal

[video=youtube;rPYmoQq85oo]http://www.youtube.com/watch?v=rPYmoQq85oo#t=0[/video]

 

[Engineer]

Then the answer based on the reaction latency would be unfounded, if the lander has significant amount of hover time, say 30 seconds to 1 minute.

The keyword is "if". Realistically, carrying that much fuel isn't doable. To carry more fuel, you need a bigger lander, which means more weight. More weight means more fuel is needed, and more fuel means even more weight. With the launch mass increased, the rocket will also need to carry more fuel. So, the rocket will have to be bigger and heavier, a rocket that China doesn't have.

Also, the point of the mission isn't hovering, but to put a lander with instruments on the moon. It is actually more desirable to have less hover time, as this means less fuel is needed or an increase of payload capacity.

 

[broadsword]

From a height of a few hundred feet, visibility of rocks or holes may not be clear and by the time they are, the two second lapse becomes insufficient. But with its own on-board, whether it is 3-D imaging or 2-D, it can do better on its own since a generally safe spot has been chosen.

 

[chuck731]

The most important point of the mission for the decision makers in china is to not fail and embarrass china. Based on history of Apollo lunar landing, there is substantial chance, at least. 1/6 or 17%, where 30 seconds - 1 minute of hovering fuel for the lander spelled the difference between success and failure. During Apollo 11 landing, the initial landing target site was seen to be boulder strewn during final stages of descent. Neil Armstrong Had to manually steer the eagle lander around for 30 seconds to look for a more suitable landing spot. When he actually found the suitable spot and landed he had burned almost all of the lander's hover fuel reserve, and had virtually no more margin to abort or make any correction upon his final descent.

It was only revealed years later that if Armstrong had taken just a couple of more seconds to find a suitable spot, Eagle would have ran out if fuel before setting down, and would have made a hard landing that would in all likelihood at least precluded successful firing of return stage, if not killed the 2 astronauts on impact.

So depending on the risk tolerance policy governing a lunar landing mission, it may well be advisable to include added fuel for diversion to alternate landing sites.

Buzz Aldrian, Neil armstrong's companion on Apollo 11, specifically observed when interviewed about Yutu that the Chinese lander carrying Yutu appears significantly larger than would be required to deliver a rover of Yutu size. He speculated the lander was not a custom job, but a test article for a standardized design meant to later deliver much larger articles to the moon. This also suggest the lander has plenty of surplus fuel for a significant amount of hovering since it is carrying significantly less payload than it is designed to.

 

[Engineer]

The most important point of the mission for the decision makers in china is to not fail and embarrass china.

That is clearly not the case, and such statement reflects your lack of knowledge as to what are important to China and what are important in a space mission.

The project could have been a lot simpler if the entire mission is just to put a lander on the moon. That way, the lander could carry 100% fuel and takes all the time it needs to find a suitable spot. Success is immediately achieved as soon as the lander touches down. Yet, Chinese engineers chose to take on a lot more risks by deploying a rover, making that rover autonomous in navigating and performing scientific experiments, as well as making that rover robust enough to survive for months. Such mission is very hard to achieve success as there are a lot of things that can fail in the mission. The sophistication of the mission itself is an unequivocal proof that decision makers in China prefer scientific success rather than a pointless political success.

Based on history of Apollo lunar landing, there is substantial chance, at least. 1/6 or 17%, where 30 seconds - 1 minute of hovering fuel for the lander spelled the difference between success and failure. During Apollo 11 landing, the initial landing target site was seen to be boulder strewn during final stages of descent. Neil Armstrong Had to manually steer the eagle lander around for 30 seconds to look for a more suitable landing spot. When he actually found the suitable spot and landed he had burned almost all of the lander's hover fuel reserve, and had virtually no more margin to abort or make any correction upon his final descent.

It was only revealed years later that if Armstrong had taken just a couple of more seconds to find a suitable spot, Eagle would have ran out if fuel before setting down, and would have made a hard landing that would in all likelihood at least precluded successful firing of return stage, if not killed the 2 astronauts on impact.

So depending on the risk tolerance policy governing a lunar landing mission, it may well be advisable to include added fuel for diversion to alternate landing sites.

Buzz Aldrian, Neil armstrong's companion on Apollo 11, specifically observed when interviewed about Yutu that the Chinese lander carrying Yutu appears significantly larger than would be required to deliver a rover of Yutu size. He speculated the lander was not a custom job, but a test article for a standardized design meant to later deliver much larger articles to the moon. This also suggest the lander has plenty of surplus fuel for a significant amount of hovering since it is carrying significantly less payload than it is designed to.

All these don't invalidate what I have said. Carrying that much more fuel remains something not worthwhile. It is also not doable on the relatively small Chinese lander using China's existing launch vehicles. Beside, the Chang'e lander is a robot whereas Apollo is a crewed lander. A computer does not need an extra 30~60 seconds that a human may require.

I also disagree with you on your view that 30~60 seconds would make a big difference. The fact is it makes no difference at all, because no mission failed due to running out fuel for the retrorockets. The one mission that failed has nothing to do with running out of fuel. Your point on how almost all the fuel for hovering on Apollo 11 was used up is a testimony as to how perfect the lander was designed and how perfect the crew was trained -- nearly nothing was wasted.

 

[chuck731]

On the contrary, if there was not a 30-60 second hover fuel reserve, Apollo 11 would have failed by landing in a field of boulders. The fact that no landing mission during the whole of Apollo program failed was a testament to the critical importance of the margin 30-60 seconds of hover fuel provided.

 

[broadsword]

It seems both arguments have merit.

According to

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Chang’e-3 is equipped with technologies that would help it to hover over any obstacles for a safe soft-landing.

And most likely without requiring any intervention from Earth.

According to

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, the Lunar Lander to be launched by ESA in 2018 has this landing technology

In order to avoid landing on unsafe terrain, an autonomous Hazard Detection and Avoidance (HDA) system is employed. The system is composed of a LIDAR and a camera, which generate 2D and 3D images of the surface, and by the on-board computer, which uses these images to characterise the landscape underneath the lander during the final descend. If the area is deemed unsafe, the system orders a retargeting to a safe landing area, compatibly with the propellant left.

That kind of technology China already has.