Many folks would like to see us back on the Moon and developing its resources.

Tuesday, December 31, 2013

Chang’e 3's landing cushion technology employs superplastic materials.

When Apollo 11 landed on the Moon there was a need to provide a way to cushion the landing and a crushable aluminum-honeycomb cartridge was used.

Now I see the term 'superplastic' used in relation to the cushion technology for Chang'e 3 lander. 

Wasn't familiar with the term and still a bit confused as the immediate information seems to be about being able to form materials.  

Superplastic, sounds so simple, just maybe some stretchy thing, but what really?  

Stretch, crush, either way, a lot of testing.  Landing your egg on the Moon without breaking the shell. What would you design?
- LRK -

Landing System
In its ambitious landing sequence, the Chang’e 3 lander is dropped from an altitude of 4 meters which required a cushioning landing system on the lander to create a fairly soft landing. The system also has to support the Rover release that is performed after landing. A “cantilever-type” design has been selected for Chang’e 3.

The landing system utilizes four primary landing legs that are equipped with footpads to avoid sinking into the surface. The Chinese used previous lander designs and knowledge on the properties of the lunar dust to develop a landing system that minimizes mass while maximizing stability.

The primary landing struts facilitate bumpers with interior buffer elements to provide shock-absorbing capabilities. The legs are installed at a 30° angle to the lander structure. Multi-functional and single-functional secondary struts are attached to the landing legs to provide additional attach points to the lander body. 
Two secondary struts are attached to each of the landing legs. Those also provide flexibility and shock-absorbing capabilities. Chang’e 3's landing cushion technology employs superplastic materials.  [emphases mine - LRK -]

Porous and Cellular Materials for Structural Applications - 318 pages PDF - 
You may not be up to reading 318 pages but a look at the table of contents might be informative.
- LRK -

  1. [PDF]

    Porous and Cellular Materials for Structural Applications - Defense ... 

    by DS Schwartz - 1998 - Cited by 43 - Related articles
    Superplastic Foaming of Titanium and Ti-6AI-4V 231 ..... Volume 532—Silicon Front-End Technology—Materials Processing and Modelling, N.E.B. ..... the collapse stress, oc*, is important in the design of cushions for shock or impact ...... employed to analyze the effect of indenting geometry on the Brinell hardness of sintered  ...
Still not seeing what was done.
- LRK -

In materials sciencesuperplasticity is a state in which solid crystalline material is deformed well beyond its usual breaking point, usually over about 200% during tensile deformation. Such a state is usually achieved at high homologous temperature, typically half the absolute melting point. Examples of superplastic materials are some fine-grained metals and ceramics. Other non-crystalline materials (amorphous) such as silica glass ("molten glass") and polymers also deform similarly, but are not called superplastic, because they are not crystalline; rather, their deformation is often described as Newtonian flow. Superplastically deformed material gets thinner in a very uniform manner, rather than forming a "neck" (a local narrowing) that leads to fracture.[1] Also, the formation of microvoids, which is another cause of early fracture, is inhibited.[citation needed]
In metals and ceramics, requirements for it being superplastic include a fine grain size (less than approximately 20 micrometres) and a fine dispersion of thermally stable particles, which act to pin the grain boundaries and maintain the fine grain structure at the high temperatures and Existence of Two Phases required for superplastic deformation. Those materials that meet these parameters must still have a strain rate sensitivity (a measurement of the way the stress on a material reacts to changes in strain rate) of >0.3 to be considered superplastic.
The mechanisms of superplasticity in metals are still under debate—many believe it relies on atomic diffusion and the sliding of grains past each other. Also, when metals are cycled around their phase transformation, internal stresses are produced and superplastic-like behaviour develops. Recently high-temperature superplastic behaviour has also been observed in iron aluminides with coarse grain structures. It is claimed that this is due to recovery and dynamic recrystallization.[2]
  1. ^ G. E. Dieter, Mechanical Metallurgy, Third Edition, McGraw-Hill Inc., 1986, p. 299–301 and 452–453, ISBN 0-07-016893-8.
  2. ^ Sharma, Garima; Kishore, R.; Sundararaman, M.; Ramanujan, R.V. (15 March 2006). "Superplastic deformation studies in Fe-28Al-3Cr intermetallic alloy"Materials Science and Engineering: A 419 (1–2): 144–147. doi:10.1016/j.msea.2005.12.015.
  3. ^ T. G. Nieh, J. Wadsworth and O. D. Sherby (1997). Superplasticity in metals and ceramics. Cambridge University Press. pp. 240–246. ISBN 978-0-521-56105-....

Could something like this be used?
- LRK -

The Ministry of Science and Technology 
People's Republic of China 

No. 470
March 3 0,2007
Super Plastic Bulk Metallic Glasses 
A research team, led by WANG Weihua at the Institute of Physics, part of the 
Chinese Academy of Sciences, has successfully worked out super plastic bulk 
metallic glasses at room temperature, through binding the seemingly unbinding 
properties. The finding was published in a recent issue of journal Science. 
In contrast to the poor plasticity that is usually observed in bulk metallic glasses, 
super plasticity is achieved at room temperature in ZrCuNiAl synthesized 
through the appropriate choice of its composition by controlling elastic moduli. 
Microstructures analysis indicates that the super plastic bulk metallic glasses are 
composed of hard regions surrounded by soft regions, which enable the glasses 
to undergo true strains. This finding is suggestive of a solution to the problem of 
brittleness in, and has implications for understanding the deformation 
mechanism of metallic glasses. 
As the elements used in the new metallic glasses are popular metals that can be 
procured at a reasonable price, the new finding has created an important 
scientific and application perspective for the material. 

Well I didn't see a definitive answer to exactly what was used to cushion the Chang'e 3 lander.
Maybe you saw something I missed.
Superplastic, nice sound, hmmmm.
- LRK -

Thanks for looking up with me. 
- LRK -
Lunar Reconnaissance Orbiter spies Chang'e 3 and Yutu

Posted by Emily Lakdawalla

2013/12/30 04:36 CST

Topics: pretty pictures, pics of spacecraft in space, Lunar Reconnaissance Orbiter, the Moon, Chang'E program

As promised, Lunar Reconnaissance Orbiter's sharp eyes spotted the Chang'e 3 lander and Yutu rover on the lunar surface on December 25. The hardware shows up as a few bright pixels throwing long, dark shadows, clearly visible in a before-and-after comparison. The lander is the bigger blob, the rover a much smaller one.
Chang'e 3 update with lots of pictures: Yutu begins lunar journey

Posted by Emily Lakdawalla

2013/12/23 02:54 CST

Topics: pretty pictures, pics of spacecraft in space, mission status, the Moon, Chang'E program

There was a lot of action on Chang'e 3 over the weekend! The first thing I want to share with you is this cool little video of the rover rolling, evidently shot on the Moon. I took it from this news report on Youtube. It was a television camera recording of a video monitor, so the color is all washed out, but you are looking at video of a rover making tracks on the dusty surface of another world. Tremendous.



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