Why aren't SpaceX controllers allowed to abort during the final 10 seconds?

Question

During yesterday's aborted SpaceX launch, someone was giving instructions to the controllers about abort procedures:

To abort the launch, a controller will say 'abort, abort, abort'.... controllers will not call an abort in the final ten seconds of launch.

^{Paraphrased from memory}

In fact, the forcefulness with which this was announced provoked this tweet:

The dude giving abort instructions for #SpaceX #Falcon9 #SES8 kinda sounds like he is reciting the rules for Fight Club.

^{Tweeted by Pillownaut on November 28, 2013 at 10:30 PM}

My question is this: Why aren't controllers allowed to call an abort in the final ten seconds? It seems that if I were a controller and I found something that was going to cause something to blow up, it would be preferrable for others to know - even if in the last ten seconds.

What is the rationale behind this rule?

Answer 1

It seems the most likely reason is that at T-10 seconds, anything that is a serious enough issue to abort should be caught by the computer, and aborting mid-stream could cause larger issues. Take a look at this video of the last 10 seconds. Here's what I can see happen:

• T-6 Water comes out for sound suppression on surface
• T-3 Engine ignites

The last seconds, essentially everything is on auto. The automatic aborts have been tested, in fact, this is at least the second Falcon rocket to abort automatically right before launch. A manual abort would need to be tested further along in the system. I suspect an abort could still fairly easily happen at T-8, but at T-6, it could potentially only be partially aborted, which could be quite a bit more dangerous than automatically aborting. Give a couple of seconds to react, and the fact that it's just easier to remember 10 than 8, and that's probably why an abort can't be called at the last second.