Apollo 11 PDI Inverts and hits the moon

[redberon2003]

Made it through to this point, only to point straight towards destruction. at pitchover instead of pitching up im going straight into the moon.

can anyone take a look at this for me? where am I going wrong :lol:

scenario was too big to attach to the forum so i put it on google drive.

https://drive.google.com/open?id=1SpLAGpNYHdVRCiVCEB2bmZUyiged5X59

 

[jalexb88]

Is the LM spinning to heads-down towards the moon with full thrust? I don’t have access to my PC unfortunately so I can’t check the scenario, but I may know what is happening based on your description. Did you remember to set your joysticks throttle at 0 before PDI? If you forget this it will override the LGC’s automatic control of DPS thrust causing the issue you are having. IE Throttle-down won’t occur and thrust is too high so the LGC will invert the LM to correct the trajectory.

 

[redberon2003]

Thats exactly the behavior. It pitches so im thrusting at the moon and thats the end of that. It'll be a few days before i can try it but ill unplug the joystick on the next try

 

[redberon2003]

Unfortunately after checking the Joystick I'm still seeing the same behavior.

One thing I've noticed during PDI is engine Command reaches 100% but actual thrust never passes the 50 mark. is this normal behavior?

 

[indy91]

Ah, so you are getting the exact opposite issue from what Alex was suspecting. If the throttle is stuck at 100% due to some joystick setting then the LM will also invert its attitude at a certain point after throttle down is desired.

What you are getting is probably that the DPS propellant section isn't properly pressurized. The actual thrust should be the same as the commanded thrust throughout the descent. So before PDI, make sure you have opened all the right valves, including the explosive ones. You probably missed a step or so. Make sure one or both of the ED logic power circuit breakers are closed. Then set Master Arm to On and put the He Press - Des Start switch up momentarily. That is probably what was missing. Also make sure Descent Helium Regulator 1 is open (grey talkback).

EDIT: Looked at your scenario and the set of valves that haven't been opened are the DPS propellant isolation valves. The switch for that is also on panel 8. This procedure is normally done shortly before undocking. Simply:

-MASTER ARM ON
-DES PRPLNT ISOL VLV - FIRE
-MASTER ARM OFF

And then, using the PRPLNT TEMP/PRSS MON switch, check that the DPS pressure is 242-254 psi.

 

[redberon2003]

Indy, threw the switches and that was the Magic bullet. Lack of thrust was my failure. After 2 attemps at a successful landing, and 3 more attempts at randezvous. And a little time acceleration on the way back home made a good splashdown. Thank you guys for all the work you put into this.as a long time lover of flightsims. NASSP is a project on a level all its own