3
$\begingroup$

In the movie "Alien" by Ridley Scott, there's a Drinking Bird which, presumably, the crew activated when entering stasis, and which is still going after they emerge. However anyone who has had one of these birds will know that they don't last long at all. But it made me curios to know if there are better examples of perpetual motion style machines that could actually last years or maybe even decades in a spacecraft, given vacuum and micro-gravity?

The only one I can think of is a spinning sphere or disc suspended in a vacuum. Should last a very long time, but it's not very flashy or interesting. Any ideas?

Edit: To clarify, I'm looking for a device that could fit inside a spacecraft and provide the same symbolism for a real space flight crew as the Drinking Bird does in Alien. Something you can set off, and wake up to still moving years later.

$\endgroup$
  • $\begingroup$ A flywheel was my first idea, too. $\endgroup$ – a CVn Mar 19 '16 at 23:13
  • 1
    $\begingroup$ The Drinking Bird isn't a perpetual motion machine. It's a heat engine, but it depends on the water being cooler than the surrounding air. $\endgroup$ – Howard Miller Mar 20 '16 at 1:47
  • 1
    $\begingroup$ The drinking bird needs gravity to work. $\endgroup$ – Wirewrap Mar 20 '16 at 8:18
  • 1
    $\begingroup$ @Wirewrap Actually, it would only need a spring. Conversely gravity makes a pretty good spring, if you don't have one. $\endgroup$ – Howard Miller Mar 22 '16 at 2:22
  • $\begingroup$ The drinking birds tend not to last because they're not very well made. If you had a skilled artisan to make one it might cost thousands of dollars, but it would last for centuries. $\endgroup$ – Howard Miller Apr 13 '16 at 12:51
5
$\begingroup$

The Earth's been going around the Sun for 4 and a half billion years. It's still not a perpetual motion machine, but it's doing a good imitation.

$\endgroup$
4
$\begingroup$

"Solar fan" - a turbine with one side of the blades reflective (white) and the other absorptive (black). The differential in light pressure would keep its spin accelerating. Sure it would also drift, but there are a plenty of ways to counteract it, or just neglect the drift.

For deep space counterpart you could exploit cosmic background radiation by selectively shielding or exposing areas of the propeller with large enough block of absorptive material.

$\endgroup$
  • 2
    $\begingroup$ I used to have a Crooke's Radiometer. It has four triangular vanes in an evacuated bulb. Each vane is white on one side and covered with lamp black on the other. The remaining air in the bulb tends to stick to the black side of the vanes, but light causes the vanes to warm up, and the air molecules 'pop' off, causing the vanes to turn. $\endgroup$ – Howard Miller Mar 20 '16 at 2:02
  • 2
    $\begingroup$ @HowardMiller is correct, it's not the photons that cause the motion, it's the gas inside the bulb. Also, when I think "perpetual motion", I think a requirement is motion without any external energy added - which is exactly what those photons are introducing to the system. $\endgroup$ – Steve Apr 12 '16 at 19:18
  • $\begingroup$ @Steve The second law of thermodynamics prevents perpetual motion. $\endgroup$ – Howard Miller Apr 13 '16 at 0:36
  • $\begingroup$ @HowardMiller I understand that ... Re-reading the question I see "closest to perpetual motion", so I guess I have to give a little slack in the interpretation. $\endgroup$ – Steve Apr 13 '16 at 12:18
1
$\begingroup$

This sounds a lot like this:

http://100yenshopping.com/wp-content/uploads/2016/06/SolarPoweredSwingingLuckyCat-FrontView.jpg

(CC picture coming later)

It needs a bit of sun, and can sustain a similar semi perpetual motion.

Of course a plastic one would'nt last centuries, but this is just an engineering issue.

$\endgroup$
0
$\begingroup$

Assuming you don't get too near any stars, it is pretty easy to travel in temperatures that will support Super Conductors. Also assuming you can shield the heat of your ship from the device...

Build a carousal that will spin on a super conductor. Put it it outside in the cool vacuum of space. Cover it with something to protect from micrometeorite impacts. Point a camera at it. Start it spinning.

Other then the initial push there is no outside energy impacting the perpetual motion machine.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.