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I'm curious about the use of stethoscopes as a backup communication source. This would be used between two spacecrafts, such as 2 astronauts in spacesuits, and help bridge the vacuum between them.

  • Would it work ? If not, what would it take to make it work ?
  • Has it ever been envisaged ?
  • Has it been done ?

The idea would be to either put the "receiver" part on the helmet and transmit the vibration through it or to have a dedicated vibration port somewhere on he spacesuits.

Bonus: If you used it on the skin of a spacecraft, would you be able to makeup some of the noises from the inside ?

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  • $\begingroup$ In some sci-fi novel or short story there was a scene about touching the helmets (iirc visor to visor) and yelling to transfer voice. But no idea what story or author it is (Clarke or Heinlein would be my first guess) $\endgroup$ – jkavalik Mar 27 '18 at 6:15
  • $\begingroup$ I think I saw that, maybe in Gravity ? $\endgroup$ – Antzi Mar 27 '18 at 6:29
  • $\begingroup$ Did not watch that yet so should be elsewhere too. $\endgroup$ – jkavalik Mar 27 '18 at 6:47
  • $\begingroup$ I wish I could give a definitive answer, but I can only speculate: It should work… you're describing a kind of tin can telephone. $\endgroup$ – DarkDust Mar 27 '18 at 7:34
  • $\begingroup$ @Antzi groups.google.com/d/topic/rec.arts.sf.written/wliV_eqYJAA/… for some stories using it :) (thanks to SciFi SE user14111 for providing the link) $\endgroup$ – jkavalik Mar 27 '18 at 7:44
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A real stethoscope has some features that make it useful in normal use, but would be a hindrance in your scenario.

  • The sound conductance medium is the air column in the tube, not the tube itself. Between ships or spacesuits, the air column would not be present. The flexible material of the tube is a poor sound conductor.

  • The ear pieces help to direct the pressure waves to an eardrum. They will couple poorly to anything flat like a ship.

Based on no evidence, I'd assume a rubber/plastic stethoscope would be almost useless. They're also pretty short. If you're close enough to use one, you'd probably be close enough to be in direct contact which should help.

If I needed to construct some sort of "tin-can" system, then I'd want it to be rigid to reduce losses, and to couple better with rigid exteriors (like a panel or faceplate). It would be nice if it had some flexibility so that you don't risk poking a hole in things. My first thought is modifying something like a cheap curtain rod or a telescoping radio antenna. It has rigid tubes that will transmit sound. The tubes can pass by each other so that the length isn't fixed. Adding a cone or disc shape to the ends to increase the contact area would probably help.

The utility from such a device seems very low. I can't imagine too many situations where every it would be useful and less risky than other means of communicating.

Whether it could be used on the skin of a spacecraft depends on the makeup of the craft. The more insulation and separation between the skin and the inner walls, the greater difficulty this will have.

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  • $\begingroup$ I could imagine a "stick on microphone" connected by wires to a robot probe or the users spacesuit could be useful for contacting someone in a spacecraft or suit whose radios had all failed. $\endgroup$ – Steve Linton Mar 27 '18 at 14:45
  • $\begingroup$ The most simple way of communicating without radio is probably either using hand/arm gestures (think sephamore) or pushing the visors or faceplates of the suits together and yelling. $\endgroup$ – Dragongeek Mar 27 '18 at 21:06
  • $\begingroup$ An electronic stethoscope may be build without gas filled tubes using a special microphone for noise in solids, an amplifier and headphones. $\endgroup$ – Uwe Mar 28 '18 at 8:15
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Wireless voice communications have been around for more than a century by now. It's technology that has been improved and ruggedized in civil and military applications for 9 decades now.

I'll venture to say that almost any other electronic system in your spacesuit is far more likely to fail than voice comms. Including life-critical systems. Considering pretty much all that you need to bridge would be a couple meters of literal free-space loss, the devices needed to successfully communicate would be the size and weight of a thumbtack, maybe of two pennies if including a backup battery for a couple of minutes of comms during a power failure.

So, I'm pretty convinced you're solving a problem of least concern.

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