Did Apollo 15 need a plane change?

[tblaxland]

I guess what I'm asking is, how do I adapt the pitch, roll, and yaw values in the flight plan to attitude mfd.

Ah, OK. The answer is now: yes you can but not easily . First some background.

Attitude MFD only supports a limited number of reference attitudes:

1. Attitude (inertial reference frame aligned with Orbiter's global frame)
2. Velocity (rotating reference frame aligned with velocity vector and orbital angular momentum vector)
3. Target (rotating reference frame aligned with target vector and local horizon*)
4. Entry Interface (inertial reference frame aligned with the velocity vector at predicted entry interface and orbital angular momentum vector)

Apollo used a number of inertial reference frames called REFSMMATs (Reference to stable member matrix). These were typically aligned with the target spacecraft attitude at certain critical events. For example, at lift off they used a REFSMMAT that was aligned with the target orbital plane and the local horizontal at the targeted liftoff time. At LOI, the REFSMMAT was aligned with a retrograde attitude at the targeted LOI TIG. This made it easier for the crew to read off any attitude errors from the FDAIs. (Read more about REFSMMATs here: http://en.wikipedia.org/wiki/Refsmmat)

Apollo REFSMMATs can be simulated in Attitude MFD by going to Attitude mode. If you know what the orientation of the REFSMMAT is to the Orbiter global frame than you can enter that in for the attitude offsets (Set Pitch etc) in Orbiter and then read your attitude relative to that from the attitude errors lower down on the MFD page. TBH, I don't know of a source that lists the orientation of the Apollo REFSMMATS with regard to any particular inertial reference frame. I expect that it could be determined from the flight plans and the angles to the navigation stars. The Project Apollo guys would know more about that from their work with the Virtual AGC (you can do fully simulated REFSMMAT re-alignments with it). I've done it before and, if you are looking for immersion, I strongly recommend it. Very cool stuff.

HTH.

*Not 100% on this one since I have looked at that bit of code for a while, going from memory.

 

[ASCII]

Good Answer.

It would be a "nice to have" for sure.
I am not terribly concerned about automatically moving to the correct attitudes. It would just be nice to see out the windows the same thing that the astronauts saw.

I also have quite an interest in the flight plan and what events happened at one time.

 

[ASCII]

Ok next question

what was the typical PTC attitude?

I understand the concept of the BBQ roll, but which way was the stack pointed during the entire coast?

Was the stack normally oriented toward the earth for better communications acquisition?
Or broadside against the sun like a chicken on a spit.

I don't need to be exact. But in general, how was a PTC performed?

 

[tblaxland]

Ok next question

what was the typical PTC attitude?

I understand the concept of the BBQ roll, but which way was the stack pointed during the entire coast?

Was the stack normally oriented toward the earth for better communications acquisition?
Or broadside against the sun like a chicken on a spit.

I don't need to be exact. But in general, how was a PTC performed?

A bit of both. Broadside to the sun so that all critical parts of the vessel received approximately equal solar radiation. Also broadside to the Earth so that one the four omni-directional antennas on the side of the spacecraft was always pointing towards Earth. From the Apollo 15 flight journal:

The last P52 aligned the X-axis of the IMU platform with the ecliptic and at right angles to the Earth-Moon line; its Z-axis was aligned southward, perpendicular to the ecliptic. If the spacecraft were aligned to match the platform, it would have its longitudinal axis aligned with the ecliptic with the Earth and Moon to either side. By pitching 90°, as called for in the Flight Plan, the longitudinal axis of the spacecraft is brought perpendicular to the ecliptic which guarantees that the Sun (which is always in the plane of the ecliptic) will strike the spacecraft side on as it rotates.

I highly recommend the Apollo Flight Journals and Lunar Surface Journals if you have the time. There is some very interesting information in them.