A random positioning machine, or RPM, rotates biological samples along two independent axes to change their orientation in space in complex ways and so eliminate the effect of
gravity
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
.
[Jack J.W.A. van Loon (2007). Some history and use of the random positioning machine, RPM, in gravity related research. Advances in Space Research 39: 1161-1165]
Description
The RPM is a more sophisticated development of the single-axis
clinostat
A clinostat is a device which uses rotation to negate the effects of gravitational pull on plant growth (gravitropism) and development ( gravimorphism). It has also been used to study the effects of microgravity on cell cultures, animal embryo ...
. RPMs usually consist of two independently rotating frames. One frame is positioned inside the other giving a very complex net change of orientation to a biological sample mounted in the middle. The RPM is sometimes wrongly referred to as the "3-D clinostat" (which rotates both axis in the same direction, i.e. both clockwise). It is a microweight ('
micro-gravity
The term micro-g environment (also μg, often referred to by the term microgravity) is more or less synonymous with the terms ''weightlessness'' and ''zero-g'', but emphasising that g-forces are never exactly zero—just very small (on the ...
') simulator that is based on the principle of 'gravity-vector-averaging'. RPM provides a functional volume which is 'exposed' to simulated microweight.
[A. G. Borst, J.J.W. A. van Loon. Technology and Developments for the Random Positioning Machine, RPM. Microgravity Sci. Technol., 2008. DOI 10.1007/s12217-008-9043-2]
.
Simulated micro-, partial, and hyper gravity
The concept of 'random' positioning has been used to simulate a micro-gravity environment through the nullification of gravity. This is accomplished by disorientating the target model, or as "vector-averaging". Through the use of a centrifuge, a '
hyper-gravity' gravity can be simulated, as the model will get exposed to a continued accelerated force. In the circumstances of hyper-gravity within a micro-gravity environment, a partial 'Earth' gravity is created. Hyper-gravity simulation is also achieved through the use of larger centrifuges, such as the
Large diameter Centrifuge (LDC) at the European Space Agency. The LDC simulated up to twenty times the Earth's gravitational strength. A system developed by Airbus uses an algorithm to simulate partial-gravity through a not fully randomly vector-averaging. The vector-averaging by Airbus' algorithm doesn't average out the vector to null but to a percentage representing simulated partial-gravity.
See also
*
Gravitropism
Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general featu ...
References
External links
* ETH Space Biolog
''Random Positioning Machine''* DESC VU Amsterda
*Manufacturer's Website
yuri GmbH
Laboratory equipment
Gravitational instruments
Positioning instruments
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