RE-ENTRY, Apollo 13 style(SUCCESS)

[kirkmyster]

Have a quick question on this topic. I am trying to come back to earth like in Apollo 13 but I either burn up or I "...skip on the atmosphere" like Swaggart says. Have trouble going in to manual mode too, seems like the automatic is fighting me. Any ideas would be grateful. Thank you.

[peterbyrnes1]

Apollo 13's entry was pretty much like every other entry. They needed to hit the sweet spot of about 6.5 degrees. But if your heat shield is facing the entry, your angle matches up within 5 degrees of the line in the CDR's window by entry interface, you are doing fine. Make sure that your mode is set to free, and not Auto or Hold. Once you hit the atmosphere, your only real direction of control is roll. Also, make sure that roll is set to accel. And that matters because the mass of the CM is deliberately off-center. Rolling the CM affects the rate of descent, or even ascent. Because you are coming in at the direct entry at a 6.5 degree angle when returning from the moon, you are going to slam harder into the atmosphere than from an orbital entry, thus incurring more friction (i.e. heat) and more Gs as you slow. So if they order you to a head's-down orientation, make sure that's how you start. A head's-down orientation will tilt the CM to allow it to "surf" more on the atmosphere and give you a far gentler interface with it, and, after your initial interface, somewhat of an upward lift. So, once you have completed the initial interface, you will notice that the Gs drop, because the head's-down orientation gives you more of an upward push. Without properly controlling that, you will indeed skip off the atmosphere. So you have to quickly roll to a head's-up position. to allow a bit more of a downward force. As the Gs just start to increase again, I start rotating the CM back into a head's-down or partial head's-down orientation. And then I ride it out the rest of the way, as your drop in velocity guarantees that you can't skip off the atmosphere.

Just make certain that the Gs don't get too low. If they are getting too low, you may well be skipping off the atmosphere, which is death. If they get too high, you're literally toast. So use your rotation to moderate the Gs and you should be ok. But anticipate those changes with a careful eye on the EMS. If the graph appears to rise "up" (lower Gs), your altitude is likely doing the same thing after the initial interface. So turn to a head's up. If it appears to "drop" (higher Gs), pay close attention roll to a head's down if needed.

[kirkmyster]

@peterbyrnes1 - thanks for the info. That is what I was looking for. I will have to try that for my next attempt. Really do like that Apollo. Fun space craft. On a side note, once landed in the ocean did they depressurize the space craft? And if so what was the proceedure for that, is that in the checklist? Thanks for your help.

[ForceVector ∞]

peterbyrnes1 answer is spot on. I have modified and simplified many of the checklists, and weeded out some of the repetitive monitoring tasks that aren't critical or don't need doing. I know there's a way to contribute checklists and I will post a couple when they're completely edited, including re-entry and splashdown. The events peterbyrnes describe start happening VERY quickly following CM and SM separation, and it's good to have a quick-reference checklist you can click through rapidly.

As for the manual roll mode, the CM's autopilot should be in SCS Mode and Free, but don't attempt to make pitch or yaw inputs, just roll inputs like peterbyrnes says. Pitch will be controlled automatically by aerodynamic forces.

Cabin Pressurization: The CSM pilot moved both Cabin Press Relief levers to Boost/Entry, somewhere around Program 67 on the DSKY if I recall. Basically it allowed for a much faster cabin altitude change than when in NORMAL mode. These procedures are in the default checklists, but might be hard to find. About the time the mains deployed, or maybe a little sooner, the CSM pilot moves the relief levers to DUMP. This "dumps" any excess cabin pressure overboard and equalizes the pressure inside the CM with the ambient air outside. Then you might notice in the checklist they move the levers to CLOSE before dumping any residual propellants, since you don't want to let monomethylhydrazine and nitrogen tetroxide vapors through the relief valves and into the cockpit. And before splashdown, they move the levers to close so water won't get through.

[peterbyrnes1]

MAJOR CORRECTION. I edited my post above. I reversed head's up and head's down. Poor editing on my part. Just remember, the CM will tend to go in the direction of your feet.

[ForceVector ∞]

Originally posted by peterbyrnes1:

MAJOR CORRECTION. I edited my post above. I reversed head's up and head's down. Poor editing on my part. Just remember, the CM will tend to go in the direction of your feet.

Geez man, now you made me look like a fool for giving your answer a "head's up" (pun intended). Thanks, you owe me some astronaut rations. And cigarettes if you have any.

[kirkmyster]

I want to thank all for the information you have provided, interesting stuff. Think it is going to take awhile to pilot this Apollo, I try 5° and the 6.5° and burning up. I come down like a rock and can not even out. Gotta be something simple I am not seeing. I will work on it though

[peterbyrnes1]

Originally posted by ForceVector ∞:

Originally posted by peterbyrnes1:

MAJOR CORRECTION. I edited my post above. I reversed head's up and head's down. Poor editing on my part. Just remember, the CM will tend to go in the direction of your feet.

Geez man, now you made me look like a fool for giving your answer a "head's up" (pun intended). Thanks, you owe me some astronaut rations. And cigarettes if you have any.

But I did fix it, so now it works! And no cigarettes in a pure oxygen atmosphere, please.

That said, allow the CM to stay head's down until it begins its climb. That's the function of the CM having slowed, and now beginning to "surf. as soon as you see that, roll to head's up. It will still have a good deal of upward momentum, so ride it out until you see the Gs just beginning to pick up again. Don't give it a chance to pick up a full G. Flip it to head's down right away and leave it there. You will ride it out with moderate Gs. This gives you time to tansition into the procedures below 50K feet.

[kirkmyster]

@peterbynes1 and @ForceVector - Tried again - FAILED. It seems like my ROLL controls have no effect. Also it looks like when I seperate the service module from the command module the RCS jets are still firing on the service module. I slam into the atmosphere and have no control. Frustrating. Try again later.

[peterbyrnes1]

Are you following the Earth Orbit Entry Vehicle and the latter half (after the deorbit burn) of the SPS Deorbit and Entry checklists? As soon as the instructions pass the point of PRO-ing through the P40 burn in the latter checklist, you can follow it. Just make certain that before the separation, you turn on the A/C and B/C battery ties or you'll be in the dark. Just make certain that the mode is set to "Free" (you don't need Auto or Hold) and Roll to Accel. Ignore all instructions telling you which way to face after CM-SM sep. you want to face 180 & head's-down. Switch the ORDEAL to Earth and Orb Rate. Maintain that 180 and inverted orientation, and by the time you reach EI, a look out the CDR's upper window (F9) should show the earth's horizon very close to the line running across the window. Make sure Roll is to Accel. After that, the next thing you need to do is roll to head's up once you are losing Gs, and then back down when you start gaining them (even a little) again.

[ForceVector ∞]

Originally posted by kirkmyster:

@peterbynes1 and @ForceVector - Tried again - FAILED. It seems like my ROLL controls have no effect. Also it looks like when I seperate the service module from the command module the RCS jets are still firing on the service module. I slam into the atmosphere and have no control. Frustrating. Try again later.

Don't despair... I have some keyboard characters permanently etched into my forehead, from smacking it on said keyboard. Many many practice missions it takes... YES! I recently killed myself from the chutes failing to deploy simply because I messed around with 2 circuit breakers during an experiment and forgot to reset them.

Try pulling the SPS Pitch and Yaw circuit breakers (4 of them, Panel 8, second row from bottom), just before you separate from the SM. Also make sure you have pressurized the CM's RCS system, and the RCS Transfer switch (RCS TRNFR) is switched to CM. And to the right of those switches CM RCS PRPLNT switches must be turned on. See if that works to at least get you separated. After you separate, the DSKY should automatically advance to P63, but if it has not by the time you reach Earth Interface, you need to press PRO to exit P62 and go P63. Earth Interface is the yellow EI mark in Orbit View and it's small and easy to miss, so I always put my view focus to CM and zoom in a bit to catch it exactly. When the DSKY advances to P64, did you make sure to turn on EMS ROLL and .05G switches?

[kirkmyster]

This is dumb question and confusing, what do you mean by head up/down and what indicator shows that?

[peterbyrnes1]

It refers to your roll angle. Head's-down is 180. Head's-up is 0. For head's down, the astronauts' heads are down relative to the earth. Head's-up is the opposite. Head's down is an approach where the CM will tend to gain altitude as it presents a more oblique angle towards the atmosphere, allowing more air to pass beneath it than above it. Head's up points the back end at a more perpendicular angle to the atmosphere, so it will experience greater slowing and Gs. Check the arrow on the EMS to see your orientation, but I generally watch the FDAI. Not much difference.