Quote from: Garrett on 12/02/2013 03:38 pmQuote from: Blackstar on 12/02/2013 02:41 pm...how do you assure that the rover drives only out onto the ramp and does not fall off the end? Seriously? One wonders if they were that incompetent how'd they mangage to launch a rocket in the first place.You seem to have assumed that I'm not asking questions because I want to know the answers and that I must be either stupid or assuming that the Chinese are dumb. I assure you that is not the case.I note that you didn't provide any answers.Note that getting a rover off a lander is a non-trivial piece of engineering, as JPL has demonstrated over two decades.
Quote from: Blackstar on 12/02/2013 02:41 pm...how do you assure that the rover drives only out onto the ramp and does not fall off the end? Seriously? One wonders if they were that incompetent how'd they mangage to launch a rocket in the first place.
...how do you assure that the rover drives only out onto the ramp and does not fall off the end?
Actually i rechecked the video, you'll see that the ramp surface shown is "perforated" which presumably is designed so that wheels can engage with these like gears.What i'm wondering is if they can open that ramp to two sides, or one only. Mechanically it would be just slightly more complicated to design it - probably dont even need an extra servo.If it opens to one side only, they must trust their descent camera and autonomous hazard avoidance a lot - and if that works that would be a pretty big engineering achievement on its own.
The landing site is probably chosen, among other factors, so as to have a low probability of hazards for the off-ramp. That will require a bit of luck, but a very calculated luck.
Yes, I presumed that you were assuming the Chinese are dumb.
-is there any way to compensate for tilt? For instance, can the ramps be moved side to side to correct for tilt?
-what if there is a large rock blocking lowering of the ramp? Is there any way to compensate? Note that JPL has struggled with the issue of rover deployment on Mars,
Consider that they can effectively have a human in the loop in the landing sequence, confirming or making the final selection between potential spots - that only requires a few more seconds of hovering time.
Quote from: savuporo on 12/02/2013 07:45 pmConsider that they can effectively have a human in the loop in the landing sequence, confirming or making the final selection between potential spots - that only requires a few more seconds of hovering time.That's a fascinating suggestion! Have there been indications they might attempt this?
Quote from: Garrett on 12/02/2013 04:17 pmYes, I presumed that you were assuming the Chinese are dumb.Well, you were certainly wrong there, weren't you?
The few articles I've read suggested that the entire sequence is fully automated..
Quote from: Blackstar on 12/02/2013 07:38 pm-is there any way to compensate for tilt? For instance, can the ramps be moved side to side to correct for tilt?Pure guess but they probably drive the lowering mechanism with a regular servo, so i would think they can extend it to 100%, but also to 80% and 120% deployment positions
An interesting and previously-unknown (at least by me) fact: study of the lunar exosphere's disturbance by Chang'e 3's landing is expected to be performed by LADEE. Unforeseen space cooperation between China and the US!
Some people may be interested in how the United States could respond to the Chang'e-3 mission. Here are some possibilities.http://thespacereview.com/article/2413/1Red Moon, Blue Moonby Dwayne DayMonday, December 2, 2013Yesterday China launched Chang’e-3 on its way to the Moon, with landing scheduled for December 14. If it succeeds, it will be the first spacecraft to make a soft landing on the Moon in nearly four decades. Although the lander and rover have a modest scientific instrument suite, they are headed for a previously unexplored region of the Moon and will therefore return new and undoubtedly interesting data. Chang’e-3 will not be alone. NASA currently has two spacecraft—Lunar Reconnaissance Orbiter and LADEE—circling the Moon. But although NASA also has several other possible lunar lander missions that it could start building within the next decade, it is unlikely that a NASA spacecraft will join the Chinese on the lunar surface for many years to come.NASA divides its planetary missions into three classes: flagship (large), New Frontiers (medium), and Discovery (small). The agency uses the planetary science decadal survey to select science goals for the first two categories. But NASA can also fly robotic missions in support of its human space exploration goals, and those missions are chosen by agency officials based upon their perceived requirements. In the past decade, the agency has flown lunar science missions to support the goals of President Bush’s Vision for Space Exploration, specifically the goal of sending humans to the Moon. Although the Vision for Space Exploration no longer guides NASA policy, some aspects of that previous policy continue to influence current NASA studies and plans.
Looking at Chang'e-3 compared to the Lunokhods, the rover is much higher up and has smaller wheels and a smaller wheel base. The Lunokhods did not have a high center of gravity to worry about.Then again, lookit this: