Did Apollo 15 need a plane change?

[joeybigO]

I was doing a bit of math, however jacked up my math was. After I figured where they launched and then the heading, then the inclination to intercept. Then I found my math was about 10 degrees off.

Does anyone know if Apollo 15 did a plane correction?

 

[Urwumpe]

No plane correction, the J-missions even had a much lower park orbit as the previous missions for transporting more payload to the moon.

 

[caningo]

No plane correction, the J-missions even had a much lower park orbit as the previous missions for transporting more payload to the moon.

Eh.. according to the official NASA time-line there was indeed a CSM plane change maneuver. It was done at 165:11:32.74 GET and ended at 165:11:51.05 GET.

You can check here if you want: http://history.nasa.gov/SP-4029/Apollo_15i_Timeline.htm


Peace

 

[to be]

Well, the CSM did a plane change so the LM would be able to launch directly in to orbit to meet it. (The CSM's orbit had precessed a bit since the LM landed)

 

[pattersoncr]

Eh.. according to the official NASA time-line there was indeed a CSM plane change maneuver. It was done at 165:11:32.74 GET and ended at 165:11:51.05 GET.

You can check here if you want: http://history.nasa.gov/SP-4029/Apollo_15i_Timeline.htm


Peace

I believe the OP was about a possible plane change between launch and TLI. there wasn't one.

 

[caningo]

I believe the OP was about a possible plane change between launch and TLI. there wasn't one.

Ahhh ok. He didn't really specify if it was the CSM or the Saturn V hence my confusion. :lol:

But to be true to the historic facts, the CSM did do a plane change in order for the LM to intercept it in the proper orbit.

 

[Urwumpe]

But to be true to the historic facts, the CSM did do a plane change in order for the LM to intercept it in the proper orbit.

Yes - but I did not think about this plane change, as all missions had to do this plane change before return, if my memory of orbital mechanics is not completely wrong.

Well, have to research this at home. I remember that the first landings used many burns for the LM to ascent, while later missions used a direct ascent.

 

[to be]

Well, have to research this at home. I remember that the first landings used many burns for the LM to ascent, while later missions used a direct ascent.

I was under the impression that the LM engine was not restartable or throttleable, and that all the orbital adjustments after it was shut down were done with the RCS. I suppose you could still call those burns.

 

[Urwumpe]

I was under the impression that the LM engine was not restartable or throttleable, and that all the orbital adjustments after it was shut down were done with the RCS. I suppose you could still call those burns.

The ascent engine was at least restartable - it uses storeable propellants which ignite on contact and don't require a special ignition system.

 

[jarmonik]

Apollo 12 and 14 made a minor mid-course correction of 20-22m/s
and Apollo 15, 16 and 17 made a course correction about 1-3 m/s. I suppose that is more like correction of navigation and guidance errors rather than making a scheduled maneuver.

 

[FordPrefect]

The given burn attitude in the TLI pad of e.g. Apollo 15 was 180, 045, 001 in Pitch, Roll and Yaw respectively. Although it may be small, the Yaw number indicates an out of plane orientation which together with a burn time of almost 6 minutes may add up to a plane change value not to be neglected, no?

 

[pattersoncr]

The given burn attitude in the TLI pad of e.g. Apollo 15 was 180, 045, 001 in Pitch, Roll and Yaw respectively. Although it may be small, the Yaw number indicates an out of plane orientation which together with a burn time of almost 6 minutes may add up to a plane change value not to be neglected, no?

Roll, pitch, yaw (180 roll = heads down)

 

[FordPrefect]

Roll, pitch, yaw (180 roll = heads down)

What do you mean with that? I mean in respect to what I was pointing out?

 

[Urwumpe]

Apollo's coordinate systems are not easy to be understood. The coordinates are given relative to the current IMU stable member orientation. And this orientation depends on the mission phase and available reference stars.

 

[pattersoncr]

What do you mean with that? I mean in respect to what I was pointing out?

you said 180, 045, 001 in Pitch, Roll and Yaw respectively
i.e.
P - 180
R - 045
Y - 001

I think you meant
R - 180
P - 045
Y - 001

180 pitch would indicate a retrograde burn (assuming either a Pad or preferred REFSMMAT). 180 Roll would indicate heads down ("top" of the CSM facing the Earth) besides, every Apollo orientation I've seen has been given as Roll, Pitch, Yaw.

Am I nitpicking? Probably

 

[tblaxland]

What do you mean with that? I mean in respect to what I was pointing out?

Apollo attitudes (at least for the PADs) were given in the order roll, pitch, yaw, instead of the order pitch, roll, yaw that you nominated. So the Apollo 15 TLI burn attitude is roll=180°, pitch=45°, yaw=1°.

Apollo's coordinate systems are not easy to be understood. The coordinates are given relative to the current IMU stable member orientation. And this orientation depends on the mission phase and available reference stars.

This true and means that a fully prograde burn could have a yaw angle of say 45° (or any other number you care to pick), depending on the orientation of the REFSMMAT. That said, the REFSMMAT used for TLI was the same as that set on the launch pad so a yaw of 1° indicates that there was an off-plane component to the burn. This is expected given that you can't launch directly from KSC (lat ~28.608) into the moon's orbital plane (inc ~18.294 to ~28.584). This off-plane component was used to setup an off-plane transfer, ie, the orbital plane of the CSM post-TLI was neither that of the launch nor that of the moon, but somewhere in between.

Regarding plane changes in lunar orbit, there were two times when these would typically occur:

1. During the LM landed phase the CSM would do a plane change to account for the precession of its orbit (due to the rotation of the moon) relative to the LM position. Apollo 11 didn't do this maneuvoure due to the short amount of time the LM was on the surface.

2. During rendezvous, a plane change by the LM could be done, either as a separate maneuvoure or as part of a larger phasing burn.

 

[FordPrefect]

...
I think you meant
R - 180
P - 045
Y - 001

Apollo attitudes (at least for the PADs) were given in the order roll, pitch, yaw, instead of the order pitch, roll, yaw that you nominated. So the Apollo 15 TLI burn attitude is roll=180°, pitch=45°, yaw=1°.

Ack! Sorry guys, didn't spot my error there. My mistake:fool: I meant Roll, Pitch and Yaw of course.

 

[ASCII]

A tad off topic but a good thread to ask in.

Is it possible to follow the apollo flight plans perfectly using only the flight plans and attitude mfd?

 

[tblaxland]

Is it possible to follow the apollo flight plans perfectly using only the flight plans and attitude mfd?

No. Orbiter does not model the Moon's position, nor the gravity field of the Earth and the Moon, with sufficient accuracy. No simulator does, that is why, amongst other reasons, they still use midcourse corrections in real life. You need a navigation tool, like IMFD or TransX to plan these corrections.

 

[ASCII]

No. Orbiter does not model the Moon's position, nor the gravity field of the Earth and the Moon, with sufficient accuracy. No simulator does, that is why, amongst other reasons, they still use midcourse corrections in real life. You need a navigation tool, like IMFD or TransX to plan these corrections.

I think I put that the wrong way.
I usually use IMFD for the burns, but I like to try to reproduce the same gimbal angles that are depicted in the flight plan for things like the SIVB sep maneuvers and coast phases.

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