P11 Saturn Takeover

[Thespacer]

Hi again

Using the latest modules, I was trying to switch from IU to CMC control, and then to manual control. After launching Apollo 8, I switch LV Guidance switch to CMC, key V46E, and switch to SCS. My control inputs are reflected in movement of the attitude error needles, but the saturn appears to continue on its predetermined trajectory.

Any ideas? Is it confirmed to be working? I was using the most recent launch scenarios.

Tony

 

[indy91]

The first mission that supported Saturn takeover during launch was Apollo 10. Also, the takeover during powered flight only works, if an IU platform failure has been detected. So it won't work with Apollo 8, I believe the AGC software doesn't even support it yet.

If you want to try it take e.g. the "Apollo 11 - 02 - Before Launch T-30sec" scenario and you will need to add a line there to schedule the IU platform failure (I have it on my todo list to make enabling random and scheduling failures easier and more accessible through the PAMFD). There you need to add the line:

PLATFAIL 60.0

if you want to have a failure at T+60 seconds. Best add this line below "FAILUREMULTIPLIER 1.000000000000", almost at the beginning of the scenario. And then you also need to enable failures in general in the Orbiter launchpad under Parameters, "Damage and failure simulation".

Then you should get the failure at the specified time. You will get at least the LV GUID light and when you got it you can (finally) switch over to CMC takeover mode.

 

[Thespacer]

Thanks again Indy. Works as advertised. Some observations:

- Under LVDC guidance, the FDAI error needles (mainly the pitch needle) seem aligned to the polynomial path and therefore follow the trajectory. Yet after SIC sep, the LVDC and the CMC (FDAI) monitoring diverge - is that expected?

- Under CMC guidance, I understand that, during SIC boost, the CMC provides polynomial guidance, and during SII boost it provides fixed attitude. So far so good. But since the attitude error needles do not provide meaningful guidance during manual control, how does the pilot navigate? I had a couple of practice runs, referring to launch cue cards available online and I can see with a bit more practice that they can be useful - was that the primary reference?

- On the topic of launch cue cards, I note that they refer to Theta - is that Theta as displayed on R3 of V83? Or is it just pitch attitude via FDAI. Comparing the A12 cue card with the LVDC A11 launch, it appears that Theta is in fact pitch attitude.

Grateful for any thoughts. Amazing software.

Tony

 

[indy91]

- Under LVDC guidance, the FDAI error needles (mainly the pitch needle) seem aligned to the polynomial path and therefore follow the trajectory. Yet after SIC sep, the LVDC and the CMC (FDAI) monitoring diverge - is that expected?

Yeah, I think the needles are not showing anything meaningful under automatic CMC control after staging. When you switch to manual control (V46E) then it will show the same as your RHC inputs of course.

- Under CMC guidance, I understand that, during SIC boost, the CMC provides polynomial guidance, and during SII boost it provides fixed attitude. So far so good. But since the attitude error needles do not provide meaningful guidance during manual control, how does the pilot navigate? I had a couple of practice runs, referring to launch cue cards available online and I can see with a bit more practice that they can be useful - was that the primary reference?

Yeah, I think the boost cue card was the primary reference.

- On the topic of launch cue cards, I note that they refer to Theta - is that Theta as displayed on R3 of V83? Or is it just pitch attitude via FDAI. Comparing the A12 cue card with the LVDC A11 launch, it appears that Theta is in fact pitch attitude.

Yep, it's the IMU pitch angle, as on the FDAI. In my experience following that pitch profile works the best, and then do corrections based on the actual vs. expected altitude and altitude rate. As you said, with a bit of practice it's quite possible to reach useful parking orbits.

 

[meik84]

Yeah, I think the needles are not showing anything meaningful under automatic CMC control after staging.

Shouldn't it disable (and null) the error needles after staging? There was an EMEM value for that when I remember right...