There is movie called, " First Man (2018), which is about Apollo 11 mission. CAPCOM-APOLLO 11 speaks to Apollo 11 crew:

CAPCOM-APOLLO 11: Apollo 11, now entering lunar orbit. Your roll should give you a good view in about two minutes. Over. When you have a free minute, could you give us your onboard readout of N2 tank Bravo, please?

What is the meaning of Bravo?


It means "B" in military/aviation phonetic alphabets.

Over a noisy radio link, many letters are hard to distinguish: "bee" (B), "see" (C), "dee" (D), "vee" (V), etc. The phonetic alphabet uses distinct words for each letter in order to avoid errors.

There are multiple nitrogen tanks on the spacecraft, designated A, B... and in this case Capcom is asking for a check on the "B" tank.

You'll see frequent use of "Alpha", "Bravo", "Charlie", and "Delta" throughout the Apollo mission transcripts.

Oddly, Aldrin substitutes "Cocoa" for "Charlie" at one point:

71:14:49 Aldrin: Roger. And our readouts on board are Alpha is 82, Bravo is 84, Cocoa is 84, and Delta is 87.

Cocoa (or Coco) was used in a 1947 Latin American standard; it's possible that Aldrin picked it up during his basic flight training in Florida in 1951-1952.

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    $\begingroup$ But the Apollo LM and SM used helium gas for pressurization. There were oxidizer tanks filled with nitrogen tetroxide. Bravo was not used every time: 55:55:35 - Lovell: "Houston, we've had a problem. We've had a main B bus undervolt." $\endgroup$ – Uwe Feb 18 '19 at 17:19
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    $\begingroup$ There were nitrogen tanks used for pressurizing the fuel cells. ibiblio.org/apollo/ApolloProjectOnline/Documents/… p.17 $\endgroup$ – Organic Marble Feb 18 '19 at 17:30
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    $\begingroup$ @Uwe - When there are only two choices, A and B, the non-phonetic choices are so dissimilar that using military terms is unnecessary. So, A Bus and B Bus would be used. $\endgroup$ – WhatRoughBeast Feb 18 '19 at 18:26
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    $\begingroup$ I think (correct me if I'm wrong!) that there was only a Main Bus A and a Main Bus B to supply electricity in the CSM. In which case the phonetic similarities between B, C, D, V aren't as problematic. Just a guess why Lovell didn't bother with Bravo. $\endgroup$ – user2705196 Feb 18 '19 at 18:27
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    $\begingroup$ Even when there are more than just A and B, the crews aren't consistent in their use of the phonetic alphabet. Sometimes you'll get Capcom referring to things by letter, and flight crews reading back using the phonetic for confirmation, or vice versa (cf Haise & Lousma at 057:10:14 in the Apollo 13 transcript ). $\endgroup$ – Russell Borogove Feb 18 '19 at 22:07

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