# What was the actual Q-alpha limit for Saturn/Apollo launches, and what was the typical max Q-alpha?

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.

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):

• I'm kinda stunned that it's in metric units! 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

• 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 Commented Nov 18, 2019 at 1:36
• @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. Commented Nov 18, 2019 at 2:16
• "just add wind to your sim", he said breezily Commented Nov 18, 2019 at 3:10
• 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. Commented Nov 18, 2019 at 3:28
• Huh, weird. If I add wind at all I'm doing it in all directions, heh. Commented Nov 18, 2019 at 4:53