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Skywatching

Spinning in space

Long sojourns by astronauts on the International Space Station have shown us that people can recover from extended periods of being weightless under free fall.

However, it would be nicer if those effects could be avoided. When astronauts arrive home, they are often lifted from the spacecraft.

It is very unlikely that when we arrive at a distant world after a long space journey there will be friendly aliens waiting to help us disembark.

The astronauts need to experience gravity during the trip, or something like it.

Weightlessness is what we experience when we are in free fall, moving only under the force of gravity. This applies not only when we are falling off something here on Earth, but also when we are in transfer orbits between worlds, with the engines shut down and purely moving in response to the gravity of nearby bodies.

The obvious thing would be to avoid being in free fall. For example, if we kept the spacecraft engines running so that we were adding 9.8 metres per second to our speed every second, we would feel just the same as we do on the surface of the Earth, with our usual weight.

We would run the engines for about half the journey, shut them down, turn the ship end over end and start them again. Our spacecraft would start decelerating, slowing the ship by 9.8 metres per second every second, so that by the time we arrive at our destination, we would be going slowly enough to go into orbit or land.

Unfortunately, as yet we have only two sorts of space propulsion. We have engines that can produce enormous thrusts for short periods, as needed to get from the surface of the Earth into orbit.

The other kinds are plasma engines that produce tiny thrusts, which can be run more or less indefinitely because they consume their fuel very economically.

However, they are not capable of giving the thrust required to keep our astronauts comfortable. We need engines giving a moderate thrust that can be kept going for long periods.

Decades ago, science fiction writers came up with another approach, namely to spin the spacecraft.

My family and I had a direct experience of this in an amusement park ride some years ago. The ride looked like a landed flying saucer, mounted so that it could spin around at high speed. Inside, attached to the outside wall of the "spaceship" were almost vertical benches.

We were instructed to lean against these benches. There were no windows, so we could not sense the moment we started spinning.

However, as the spin accelerated, we were pulled more and more strongly toward the wall, onto the benches, until the down direction was in the direction of the wall, which had now become the floor, and the original floor a vertical wall near our feet.

We can spin a real spacecraft in exactly the same way, so the astronauts would be pulled to the outside wall, experiencing something that feels like exactly like gravity. There have been science fiction stories of huge, hollow cylinders with large space colonies living in farms, villages and towns attached to the inside wall.

Arthur C. Clark's book Rendezvous with Rama features such a space ship. An alternative is a big, spinning wheel, like the space station in 2001, A Space Odyssey. In this case the passengers will be standing on the inside of the ring's outer wall.

Another concept is a vehicle consisting of two spheres connected by a long tube. By spinning this end over end, like a cheerleader's baton, passengers in the spheres would experience the same sort of pseudogravity.

There are technical challenges to building spinning spacecraft. One is the problem of stabilization. As people and other things move around onboard, the centre of gravity will shift slightly and the spin would wobble.

However, at the moment, spinning spacecraft seem the best option for arriving at distant planets and being able to walk off the ship.

  • Jupiter dominates the southern sky overnight.
  • Saturn rises around 10 p.m.
  • The moon will be full on the 16th and reaches last quarter on the 24th.

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About the Author

Ken Tapping is an astronomer born in the U.K. He has been with the National Research Council since 1975 and moved to the Okanagan in 1990.  

He plays guitar with a couple of local jazz bands and has written weekly astronomy articles since 1992. 

Tapping has a doctorate from the University of Utrecht in The Netherlands.

[email protected]



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The views expressed are strictly those of the author and not necessarily those of Castanet. Castanet does not warrant the contents.

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