Science Fiction has long written about this communication technique in vacuum: Astronauts touch their helmet against another astronaut's helmet, so that sound will transmit through that physical connection and they can to talk to each other without needing electronic communication devices (Example screencap from The Expanse). But is there a source that real astronauts have ever done this?

Googling "astronauts touching helmets" and "astronaut helmet-to-helmet" mostly yields verifications that it is indeed possible. The only real world mention I could find is from the US Navy diving manual: "The two divers need only touch helmets to talk with each other".

Edit: To clarify why I asked: Multiple Redditors claimed that this has happened in real life, but of course this is all hearsay: Comment 1, Comment 2

  • $\begingroup$ Unless there was an emergency situation, such a communication method would not be required inside a space craft during a mission. This then reduces the question to how many times have multiple astronauts conducted an EVA, or EVA conditions such as an open cargo area on the Space Shuttle, at the same time & were they in close proximity to one another be able to communicate in such a manner. $\endgroup$
    – Fred
    2 days ago
  • 1
    $\begingroup$ @Fred there would be no reason to use this method unless the EVA radio comm failed, and at least on US missions, I don't think it ever has. Also on most US EVAs the helmets have thermal / protective fabric or other structures over a large part of the helmet which might prevent this from working. My guess is that this has never been done on a US EVA but it would be an enormous task to prove that... $\endgroup$ yesterday
  • 3
    $\begingroup$ Was this solid-borne sound transfer ever tested in a vacuum chamber on Earth? $\endgroup$
    – Uwe
  • 1
    $\begingroup$ If this has ever been tested it would have been as a backup communication method, I suspect. Proving a negative is hard, however... $\endgroup$
    – PearsonArtPhoto
    4 hours ago
  • 1
    $\begingroup$ @Uwe vacuum might not be necessary for the test. If they can't hear each other before touching and suddenly they can hear each other when touching, then it works and air vs vacuum outside doesn't matter. The only time that vacuum would be necessary is if they could already hear each other before touching. $\endgroup$
    – uhoh
    2 hours ago


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