Saturn V ascent guidance (simulation)

A while ago, I did a Saturn V ascent simulation in Matlab. The catering for drag, gravity and thrust vectors and mass depletion worked well, but I struggled to implement ascent guidance.

I duplicated roughly what I saw in the ascent profile - a gravity turn a little while after liftoff (I tinkered with this, but I recall it being about 1.5km-2.5km alt).

Where I ran into problems was trying to guide it to orbit, as I didn't have a good set of rules for this. Typically it would either not reach orbit at all, or it would have too steep an angle of attack on SIVB cutoff and it would fall back to earth...

I understand it isn't a simple question but I appreciate any pointers. I'm happy to share the Matlab code if this helps (as long as you don't laugh too hard).

• Great user name! – Organic Marble Sep 22 '17 at 12:12
• would you mind sharing your simulation with me? – Fawad Khan Aug 26 '19 at 16:20

Try comparing your simulation to the flight data at https://history.nasa.gov/SP-4029/Apollo_11d_Ascent_Phase.htm

Robert A. Braeunig used this data to generate a pitch program:

+------------+----------------+------------+
|    Time    |     Pitch      | Pitch Rate |
| (seconds)  |   (degrees)    | (degree/s) |
+------------+----------------+------------+
| 0.3 to 30  | 0              | 0          |
| 30 to 80   | 0 to 36.40     | 0.7280000  |
| 80 to 135  | 36.40 to 62.23 | 0.4696364  |
| 135 to 165 | 62.23 to 71.14 | 0.2970000  |
| 165 to 185 | 71.14 to 60.57 | -0.5285000 |
| 185 to 320 | 60.57 to 64.75 | 0.0309630  |
| 320 to 460 | 64.75 to 77.35 | 0.0900000  |
| 460 to 480 | 77.35 to 74.59 | -0.1380000 |
| 480 to 550 | 74.59 to 81.39 | 0.0971429  |
| 550 to 570 | 81.39 to 77.25 | -0.2070000 |
| 570 to 640 | 77.25 to 85.07 | 0.1117143  |
| 640 to 705 | 85.07 to 88.23 | 0.0486154  |
| over 705   | 88.23          | 0          |
+------------+----------------+------------+


• Braeunig's page has a lot of excellent information about his sim, which may be of use. – Russell Borogove Sep 22 '17 at 15:09
• Many thanks for the data. I haven't seen this previously. Having the pitch and rates will be enough for me to build guidance rules. It will depend on whether my drag & thrust models were right as well (we will see!) I will build the rules & advise how it goes. All the best , Stephen – refsmmat Sep 23 '17 at 10:45
• I don't like the hacky table formatting, it's not a terribly good general purpose answer. – JCRM Feb 27 '18 at 6:40