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

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1 Microgravity and the ‘vomit comet’

There are several ways of describing the apparent absence of gravity. You may have heard of ‘weightlessness’ where there seems to be no weight, or a ‘zero g’ environment where gravity (g) doesn’t seem to be acting. What about ‘microgravity’ though? Do these terms mean the same thing?

Watch Video 1 which introduces ‘microgravity’ environments. Then complete Activity 1.

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Transcript: Video 1 What is microgravity?

NARRATOR:
60 Second Adventures in Microgravity. Number 1, What Is Microgravity? Gravity is pretty useful. It keeps our feet on the ground, ensures the Earth orbits the Sun, and shapes the whole universe. But sometimes it would be really handy if it wasn't there, because when gravity acts on something, there is always an effect, usually from the other forces counteracting it-- like the ground pushing back on us, which we perceive as weight.
So to understand many physical and biological processes, it would be better to take gravity out of the equation. But that's impossible. So instead, we create an environment on Earth in which, as far as possible, all these other forces are balanced out so the thing we're studying appears to be weightless. We call this environment microgravity.
There are many ways to achieve microgravity, but one of the simplest is by using something called a drop tower, which is, well, a tower you drop things off. So relative to each other, objects become weightless and are in an environment of microgravity, but only for a few seconds, until they're back down to Earth with a bang.
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Activity 1 What is microgravity?

Timing: Allow approximately 15 minutes

Complete the following statements, based on what you learned in Video 1.

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Now watch Video 2, which discusses parabolic flights and how they can create a microgravity environment. This video also discusses how it is thought planets are formed. Then complete Activity 2.

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Transcript: Video 2 The ‘vomit comet’

NARRATOR:
60 Second Adventures in Microgravity. Number Two, The Vomit Comet. When you're on a roller coaster and you feel your stomach being left behind, for that tiny moment, you're experiencing microgravity. And we can use microgravity to study how planets like the Earth are formed when tiny ice and dust particles collide and somehow stick together in space.
To test how this happens, the particles have to be thrown together very gently or else they break up. But at that speed on Earth, gravity acts on them and they don't even reach each other, like a really pathetic snowball fight. So scientists head off on something called a parabolic flight, where a plane travels in a series of huge parabolas, or curves. As it goes over the top of the curve, the pilots adjust the plane's speed to counteract the effect of gravity inside. And for about 22 seconds, we can create a microgravity environment to test these planet-building collisions, just like a four-hour roller-coaster ride, which is why they call it the ‘vomit comet.’
[RETCHING]
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Activity 2 Microgravity environments

Timing: Allow approximately 15 minutes

Study Figure 1, which shows the parabolic flight pattern in more detail. Then select the answer to the questions below, based on this figure and Video 2.

An image entitled the ‘parabolic flight of an aircraft’.
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Figure 1 Parabolic flight of an aircraft.
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This image is entitled the ‘parabolic flight of an aircraft’. It shows a graph where the vertical axis is labelled with altitude and has units of feet from 24 000 to 34 000 in increments of 2000 feet. The horizontal axis is labelled as manoeuvre time and has units of seconds from zero to 65 in increments of 20 seconds, 45 seconds and 65 seconds. A parabolic curve starts from the time of zero seconds and an altitude of 24 000 feet. This curve increases to a maximum of an altitude of 32 000 feet at a time between 20 and 45 seconds. The curve then decreases to a minimum at a time of 65 seconds to an altitude of 24 000 feet. For the first stage of the flight, between a time of zero seconds and 20 seconds, this area of the graph is labelled with 1.8g. Between the times of 20 seconds and 45 seconds, this area of the graph is labelled with zero g. For the final part of the graph, between 45 seconds and 65 seconds, the area of the graph is labelled with 1.8g. Before the zero g part of the graph, the plane’s trajectory is 45 degrees nose high; after this zero g part of the graph, the plane’s trajectory is 45 degrees nose low.

Figure 1 Parabolic flight of an aircraft.

1. What height does the aircraft need to achieve to start the experiment? (Hint: look at the top of the curve in Figure 1 and draw a line from this to the vertical axis.)

a. 

32 000 feet


b. 

24 000 feet


c. 

34 000 feet


d. 

28 000 feet


e. 

26 000 feet


The correct answer is a.

2. Roughly how long does the microgravity environment last?

a. 

22 seconds


b. 

0 seconds


c. 

45 seconds


d. 

10 seconds


e. 

65 seconds


The correct answer is a.

3. Which part of the parabolic flight curve can create a microgravity environment?

a. 

In the top portion of the curve


b. 

On the way up.


c. 

On the way down.


d. 

On the bottom portion of the curve.


e. 

Nowhere.


The correct answer is a.

4. How are planets formed? (Hint: this was discussed in Video 2.)

a. 

Tiny ice and dust particles collide gently and stick together in space.


b. 

Large ice and dust particles collide hard and bounce off each other in space.


c. 

Tiny ice and dust particles collide hard and stick together in space.


d. 

Large ice and dust particles collide gently and stick together in space.


e. 

Tiny ice and dust particles collide gently and bounce off each other in space.


The correct answer is a.

Moving on from parabolic motion and planetary formation, next you will consider the physics behind the orbit of the International Space Station (ISS).