Organic Marble's answer to a previous question about Apollo abort limits clarified that the figure of concern was the product of dynamic pressure (Q) and angle of attack (alpha), with the 100% level apparently being the expected structural-breakup limit of the launcher.

What is the actual limit value for Qɑ for the Saturn V/Apollo stack?

What was the maximum Qɑ reached in nominal launches?

I'm looking for a value in psi•degrees or kPa•radians or some dimensionally equivalent pressure-times-angle units, not a normalized percentage-of-abort-limit value. Answers for other launchers are of interest as well.

I'm curious because the guidance equations in my launch simulator do produce some significant angle-of-attack, and I want to know if the trajectories I'm flying would be likely to wreck a Saturn V.


2 Answers 2


I have not yet found the abort limit figure.

According to Saturn V AS-507 "G" Mission Launch Vehicle Operational Flight Trajectory - September Launch Month (a trajectory planning document for Apollo 12), the peak Qɑ for a nominal flight would be between 18 and 22 kNº/m^2 (= kPaº):

Graph of Q-alpha product versus mission time for pre-launch simulation of Apollo 12. Three tracks are shown corresponding to three different launch azimuths (presumably for three different launch dates). The tracks peak sharply around T = 72 seconds at approximately 18.5, 20.0, and 21.5 thousand newton degrees per meter squared.

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    $\begingroup$ I'm kinda stunned that it's in metric units! $\endgroup$ Commented Nov 15, 2019 at 12:17

Edit: I stumbled upon the limit.

The maximum angle-of-attack dynamic pressure sensed by a redundant Q-ball mounted atop the escape tower was 0.28 N/cm2 (0.4 psid) between 89 and 91 seconds. This pressure was only 12.5 percent of the EDS abort limit of 2.2 N/cm2 (3.2 psid).

Source: Saturn V Launch Vehicle Flight Evaluation AS-506 page 15-1

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    $\begingroup$ Good find! That helps me a lot. Unfortunately my max payload Saturn INT-21 sim run is hitting 44 kPaº, which is neither definitely over-limit nor definitely under-limit. XD $\endgroup$ Commented Nov 18, 2019 at 1:36
  • $\begingroup$ @RussellBorogove You don't simulate any winds, do you? If not, then your alphas / betas are probably too big by a {handwaving} amount. Cause a good wind would push you over the limit. $\endgroup$ Commented Nov 18, 2019 at 2:16
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    $\begingroup$ "just add wind to your sim", he said breezily $\endgroup$ Commented Nov 18, 2019 at 3:10
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    $\begingroup$ You could have a lookup table of the wind speed vs altitude - it looks like they only applied it to head/tail, no side wind - then modify alpha by the wind velocity component. The wind is basically just going to change alpha a little and therefore change q*alpha. $\endgroup$ Commented Nov 18, 2019 at 3:28
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    $\begingroup$ Huh, weird. If I add wind at all I'm doing it in all directions, heh. $\endgroup$ Commented Nov 18, 2019 at 4:53

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