Question Soyuz (spacecraft) questions

[IronRain]

Hi everyone!

I have some questions about the Soyuz spacecraft.

De-orbit burn
I've heard a couple of versions but which is the real one?

• Is the orbital module jettisoned before or after the De-orbit burn.

• When the orbital module and the service module jettison, does it take the thermal blanket form the decent module, or does the blanket burn away in the atmosphere?

Landing
When the capsule is landed, is the parachute being released or does it remain attached? I have a diary from Frank de Winne and he said that the parachute is being released after landing but on the photos it always seems that the chute is still attached.

Thanks in advance!

Derk

 

[Urwumpe]

Hi everyone!

I have some questions about the Soyuz spacecraft.

De-orbit burn
I've heard a couple of versions but which is the real one?

• Is the orbital module jettisoned before or after the De-orbit burn.

You had both versions in history - because separating the orbital module before deorbit caused some problems, if the deorbit burn failed, it is no longer done.

• When the orbital module and the service module jettison, does it take the thermal blanket form the decent module, or does the blanket burn away in the atmosphere?

Is jettisoned with the other modules, the blankets are held in place by the other modules, with rings that are released on separation.

Landing
When the capsule is landed, is the parachute being released or does it remain attached? I have a diary from Frank de Winne and he said that the parachute is being released after landing but on the photos it always seems that the chute is still attached.

The parachute is of course released, otherwise wind would cause a lot of trouble - and it in fact does if the separation failed or happens too late.

 

[Thorton]

Is jettisoned with the other modules, the blankets are held in place by the other modules, with rings that are released on separation.

I actually was unable to find solid confirmation about blankets detachment process, do you have any links to confirm this?
As far as i know, there is no connection between thermal blankets on SA and blankets on PAO and BO, they attached to SA directly.

 

[SiberianTiger]

Landing
When the capsule is landed, is the parachute being released or does it remain attached? I have a diary from Frank de Winne and he said that the parachute is being released after landing but on the photos it always seems that the chute is still attached.

Just to add to the replies above, it's controllable from inside, and the capsule's CDR has three options what to do after landing with the parachute: release completely (what he must do in a high wind conditions), blow away one attachment point of two, or have the parachute attached (the latter can come espesially useful if, for instance, a Soyuz lands on a steep slope and its parachute gets hooked on trees).

 

[Urwumpe]

I actually was unable to find solid confirmation about blankets detachment process, do you have any links to confirm this?
As far as i know, there is no connection between thermal blankets on SA and blankets on PAO and BO, they attached to SA directly.

You can find information about it in the story about the repairs, when one of the blanket petals became loose - Soyuz TM-9 (The Shayler book, page 336p).

They write about about using spare pins to reattach the blankets to the PAO ring, or fold them to the BO for preventing that the blankets again block the sensors, or cut them completely away. Eventually, they folded the blankets away to the BO.

 

[Orbinaut Pete]

• Is the orbital module jettisoned before or after the De-orbit burn.

As Urwumpe said, both methods have been used.

In the past, the orbital module (BO) was jettisoned prior to the de-orbit burn, in order to reduce mass & improve engine efficiency. However, during one mission (I forget which one), the BO was jettisoned, and then the engine failed to light! The crew was stuck in orbit for a whole day until the problem was resolved, during which time they had no toilet, and barely enough room to move!

Nowadays, the BO is jettisoned after the de-orbit burn. However, the problem with this approach is that if the BO fails to separate, then you're in real trouble as you've already done the de-orbit burn. This actually happened on two Soyuz flights a few years back. The Soyuz had to go into a special attitude that enabled atmospheric heating to "melt" the modules apart. This however caused the Soyuz to go into a ballistic re-entry, during which the crew pulled upwards of 8.5G!

 

[DaveS]

Nowadays, the BO is jettisoned after the de-orbit burn. However, the problem with this approach is that if the BO fails to separate, then you're in real trouble as you've already done the de-orbit burn. This actually happened on two Soyuz flights a few years back. The Soyuz had to go into a special attitude that enabled atmospheric heating to "melt" the modules apart. This however caused the Soyuz to go into a ballistic re-entry, during which the crew pulled upwards of 8.5G!

The BO separated cleanly but not the PAO. Actually, the attitude change came after as result of these ballistic entries. Prior to those, the Soyuz assumed the standard entry attitude.

 

[Urwumpe]

During Soyuz 5, the mission in which the PAO failed to separate, the spacecraft did not assume standard reentry attitude, but actually depleted all SA RCS propellants trying to get to reentry attitude. The PAO was already dead at that this point, since the cable connections between SA and PAO had already been severed.

The BO was only separated before deorbit burn to permit 100 kg more cargo or a third astronaut. This was also only possible for Soyuz T and Soyuz TM.