Flight Question Soyuz reentry

[rgargente]

Hi all.
I am new to the forums but I have some experience with Orbiter already. I'm trying to do a precise reentry with Soyuz TMA (the one with ISS v3.2). I'm confused about what should I do after the de orbit burn. I have several questions:
- The most important is attitude. I do the burn retrograde, of course. Should I maintain retrograde after the burn? When should I disable the autopilot?
- When should I jettison the modules? This doesn't seem to have a great effect but I'd like to know how it's done.
- I have use the recomended procedure of the manual (ApA 380km to PeA 60 km at 167º) and also tried with BaseSyncMFD, which gives different parameters. I'd like to stick to the realistic parameters, which are right?
- I use controlled reentry and G goes to 8 or 9 every time. The manual says it should go to 4. What am I doing wrong? How should I maneuver the capsule, should I try to keep pitch to 0 or something else?

Thank you very much. I have been trying to find info on this issues but I haven't. I hope this is not a duplicate.

 

[N_Molson]

- The most important is attitude. I do the burn retrograde, of course. Should I maintain retrograde after the burn? When should I disable the autopilot?

From the ISS, aim a PeA of 50-60 km, that should do it. Thorton's AP begins to control pitch and yaw at 120 km (more and more agressively as you enter the atmosphere). Don't try to fight it and disable Orbiter's APs from this point. Keep a roughly retrograde orientation, the AP should be able to deal with it.

When should I jettison the modules? This doesn't seem to have a great effect but I'd like to know how it's done.

A couple of minutes before entering atmosphere, meaning around 200-150 km. Once upon a time, they flew in a "Zond" config (no BO) for a few orbits, but there was once a problem with the reentry, the crew had to loiter for hours in the very tight SA, it was very uncomfortable, and now BO and PAO are jettisoned in sequence. It seems a good idea to orient the Soyuz in an normal/radial position relatively to your orbit, because if you jettison in retrograde position, there is the (non-simulated) risk of the melting PAO ramming into your heatshield during reentry !

I use controlled reentry and G goes to 8 or 9 every time. The manual says it should go to 4. What am I doing wrong? How should I maneuver the capsule, should I try to keep pitch to 0 or something else ?

8-9G load is typical from a ballistic (uncontrolled) reentry. Make sure the "BALLISTIC" line in the scenario file is deleted. Also, you can't control the pitch and yaw channels, but you can control the roll (bank) channel. See the capsule as a space shuttle reentering backwards. Roll on the side and the vertical lift becomes horizontal lift (useful for fine-tuning the landing point). Roll upside down and you get negative vertical lift (if you think you are going to overshoot the landing zone). In any case, the AP (and the aerodynamics) will keep the pitch within safe parameters, heat-shield first. What you can change is the entry profile and then the G-load and downrange distance.

 

[rgargente]

Thank you, that was helpful!
I have verified I'm on controlled mode reentry: no ballistic line in the scenario file, no ballistic label on hud, and AP progressively more aggressive as you said.
However, I still get 9G. I've been playing with AeroBrakeMFD and it also predicts 9G. If I don't touch anything usually I get 9G, but sometimes more, even 12G. If I change roll during the entry and fight against de AP to reduce G I can reenter with about 4G, so I think the AP is on but it's working fine.
Maybe it has something to do with orbiter beta version, or some other addon...
Anyways, thanks for your help!

 

[sorindafabico]

AerobrakeMFD has a weird behaviour with this Soyuz. It's good only to fine-tune the landing site.

Keep zero bank and don't fight the AP - you'll start to get some lift around alt = 50km. I always get maxG = 4 doing this.

 

[rgargente]

Thanks, I was not keeping 0 bank.

 

[nicusX]

... Also, you can't control the pitch and yaw channels, but you can control the roll (bank) channel.

Sorry for the stupid question, but how I control attitude during re-entry?
After separating BO and PAO I see no RCS available, and RCS keys don't work.