Microgravity: living on the International Space Station
Microgravity: living on the International Space Station

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Microgravity: living on the International Space Station

4 Random positioning machines

Random positioning machines or RPMs (Figure 4) are used for research into:

  • cell biology
  • microbiology
  • regenerative medicine
  • tissue engineering and stem cells
  • experimenting with bacteria in a microgravity environment.
A coloured photograph of a random positioning machine.
Figure 4 A random positioning machine (RPM).

An RPM simulates microgravity by rotating with random speeds in all directions. This makes the sample experience gravity from every direction. Over a period of time, the average acceleration due to gravity is zero. The RPM can also provide a different value of gravity where organisms or cells can change.

An RPM can simulate the numerical values of gravity different from Earth’s gravity g (9.81 m/s2). In the case of Mars, this is equivalent to 0.38 g. In the case of the Moon, this is equivalent to 0.18 g.

Now, using these values, complete Activity 5.

Activity 5 RPM and values of gravity

Timing: Allow approximately 15 minutes

Answer the following questions by choosing one correct option.

1. What is the numerical value of the acceleration due to gravity on the Moon?


3.54 m/s2


2.77 m/s2


0.77 m/s2


1.77 m/s2


177 m/s2

The correct answer is d.

2. What is the numerical value of the acceleration due to gravity on Mars?


3.73 m/s2


7.46 m/s2


37.3 m/s2


373 m/s2


0.373 m/s2

The correct answer is a.

3. In Week 1, you calculated the weight of an object with the same mass on different planets. Which unit for gravitational field strength did you use?











The correct answer is c.

You will now look at the survivability of microbes in extreme physical conditions on Earth and elsewhere in the Universe.


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