I'm sure we're all familiar with the go/no go standard phrasing for reporting whether something is OK or not. Having a standard phrasing clearly makes comprehension easier and more reliable, especially in an international field where not everyone speaks the same languages, and especially when mistakes can be very costly.

But it seems like these two phrases in particular are the worst possible choice. If it's hard to hear the speaker and you don't hear the first syllable of "no go", it just sounds like "go". And even if you hear the first syllable but not the second, it still sounds enough like "go" to be easily misinterpreted.

It seems like the only advantage of go/no go is that the two phrases are different lengths, so that if you can hear the stress but the sounds themselves are indistinct, you can still tell them apart.

Whose idea was go/no go, and why did those phrases catch on, instead of two more distinguishable ones, such as "go" and "not good"?

  • $\begingroup$ Do you have examples of the phrases being used for direction in critical noisy environments? In my experience (*and per Wikipedia *) it testing criteria, generally documented. $\endgroup$ Commented Apr 18, 2014 at 18:35
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    $\begingroup$ 'such as "go" and "not good"' I'd prefer direct opposites "go" & "stop" or "run" & "stand". Surely 'main ignition is stop' sounds a little odd (I don't think it is correct grammar) but clarity is more important than grammar here. $\endgroup$ Commented Apr 23, 2014 at 2:26
  • $\begingroup$ @AndrewThompson and, to be fair, "main ignition is go" and "...is no go" are also grammatically flawed $\endgroup$ Commented Feb 10, 2015 at 19:35

2 Answers 2


To add to @aramis' excellent explanation on clarity and ability to discern the go/no-go launch status check polling, these seem to have been introduced to NASA's (and U.S. in general) launch terminology during the first manned spaceflights of Project Mercury. I wasn't able to find a good example for Project Mercury launches, but I did find this video of Gemini 5 launch, where the CBS commentator already adopted this terminology (from Gemini launch command) and says several times that the launch status is "go", spacecraft status is "go", and so on.

Before manned spaceflight, this "go/no-go" polling was used in military aviation as "go/no-go for liftoff", especially in the U.S. navy with aircraft carrier pilots and likely also test pilots, where status of several complex systems has to be coordinated between stations before they can be cleared for takeoff. Since first astronauts came from those aviators, it is no wonder that this military aviation terminology found its way into the spaceflight terminology, where station polling makes just as much sense.

One other thing to note is that these statuses of such complex systems are not communicated verbally alone, but also signalised visually. First manned spaceflights coincided with the advent of computing with first computer networks soon to follow (like SAGE and SABRE), and mission controllers could have other centralized means of checking the status of individual stations before computer networks, for example with light switchboards in their mission command / launch control center. The status of individual stations would thus be called out via radio, as well as entered into the centralized system.

So not everything depends on verbal commands alone, and several layers of control are used with station polling to avoid any miscommunication errors.


Having worked mission communications in CAP for live Search and Rescue operations, on the radio, go/no-go is VERY clear. It's one syllable versus two. (Three is the interrogative.)

The longer "affirmative" "negative" are 4 and 3, and not as clear, and further, subject to more interference due to length.

Note that this usage parallels the morse use of C (-.-.) and N (-.) in mode, tho' 1 repeat being negative in morse, and in modern use, the question mark (..--..) being used for interrogative mode.

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    $\begingroup$ Length is significant, especially for the expected positive response, but presumably there are also cognitive factors that may make confusion more likely. "go/bad-val" may be audibly clearer and less likely to be confused even with less attentive listening or (less likely) speaking, but actual research could probably find something better. Historical legacy and adequacy of go/no-go may explain its use. $\endgroup$
    – user56
    Commented Apr 19, 2014 at 18:48

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