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I am very new to space exploration by humans (was always much more interested in astronomy) and have just begun looking at rocket launches in the 1960s because my little four year old is interested in them, and I was 4 years old when Apollo 8 launched.

There seems always to be a very clear and emphatic statement "We have cleared the tower" when this event happens in the Apollo missions and earlier ones. I am not even sure who makes this statement, but it is always very noticeable.

My question is this:

Does the point of having cleared the tower signal a procedural shift: e.g. defining measures for various staff to take in an emergency and therefore something that everyone would need to know about?

My understanding is that before clearing the tower, there was very little anyone could do but hope that the launch vehicle actually clears the tower, and after that time there may be some hope of a successful escape with the escape rockets (I'm specifically talking about Apollo here, although my recollection is that there were escape rockets even for Mercury). Or is this kind of obvious statement perhaps just for the general public as a kind of exuberant "this really is IT!"?

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  • $\begingroup$ As far as I am aware, there is no procedural change. That would occur at lift-off. "Cleared the tower" does mean that unusual lateral movement would be less of a problem. $\endgroup$ – tl8 Nov 3 '14 at 6:03
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Yes, there is a procedural change, at least with NASA launches. In NASA, launches are controlled by the Launch Control Center (LCC) until the rocket clears the tower, and then are handed over to the Mission Control Center (MCC). I'm not sure how other organizations do it.

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    $\begingroup$ And starting in the latter half of the 1960's Mission Control was in Houston, not Florida, so it was a rather substantial shift. $\endgroup$ – paul Nov 3 '14 at 11:51
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    $\begingroup$ Some of the early missions were controlled from Huntsville IIRC, although I'm not 100% sure on that. If anyone's interested Chris Kraft wrote a great book called Flight about setting up the first mission control center. $\endgroup$ – GdD Nov 3 '14 at 12:29
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    $\begingroup$ Even the Apollo 13 dramatization movie got this right. "Houston, we've cleared the tower at 13:13." "Okay guys, you got it." $\endgroup$ – a CVn Nov 3 '14 at 14:51
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    $\begingroup$ Was this handoff present in Armageddon? I'm told it's the go-to movie for how space exploration really works. $\endgroup$ – corsiKa Nov 3 '14 at 18:50
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    $\begingroup$ I <Cough> wouldn't <splutter> <vomit> know! $\endgroup$ – GdD Nov 3 '14 at 19:05
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In a documentary, one astronaut mentioned that it took 12 seconds for Apollo to clear the tower; until that point, all 5 engines of the 1st stage needed to function 100%, but after the first 12 seconds or when it cleared the tower, the rocket had used enough fuel and was now light enough that if 1 main engine failed, the rocket could continue to fly with 4 engines running. I think that may be the reason why it was so critical that it cleared the tower.

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    $\begingroup$ Welcome to Space Exploration! If you can find and add a link to this documentary, or more information about it, it would be much appreciated. $\endgroup$ – Nathan Tuggy Feb 21 '17 at 4:54

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