Question about the things attached on payload fairing of the Soyuz launcher!

[ycs86]

Hi all,

Up till now I can't figure out what those things are on the payload fairing of a Soyuz launcher (pls see included picture). Can somebody please help me out? Also, in what situation will those things be used and how will it work? Thanks in advance! 

[Danderman]

Air brakes for the escape system.

[ycs86]

Air brakes for the escape system.

For aerobraking? For what use? Won't the soyuz spacecraft just slip out of the payload fairing??

[edkyle99]

Air brakes for the escape system.

And here's a link to a graphic that shows their function.

http://s88.photobucket.com/albums/k166/suzymchale/mars-center/soyuz-abort.gif

They basically act like fins on a model rocket to keep the escaping module/shroud section aerodynamically stable.  The crew module stays attached to the shroud for a few seconds before being jettisoned.

 - Ed Kyle

[ycs86]

And here's a link to a graphic that shows their function.

http://s88.photobucket.com/albums/k166/suzymchale/mars-center/soyuz-abort.gif

They basically act like fins on a model rocket to keep the escaping module section aerodynamically stable.

 - Ed Kyle

Thanks Ed, but why would they want to aerobrake the whole escape system during the booster failure scenario, if they want to pull the crew safely away from the explosion? You know what I mean, pulling and braking. It doesn't make sense.

[Stephan]

It's not for braking, but for aerodynamic stabilization.

[Stan Black]

aerodynamic stabilisers

N-1 rocket had something similiar

[ycs86]

It's not for braking, but for aerodynamic stabilization.

Many thanks to Stephan, now I get it. Thanks again! 

[ycs86]

aerodynamic stabilisers

N-1 rocket had something similiar

Thank u too, Stan! 

[ycs86]

One more question:

As opposed to Russians, why don't US launchers use "aerodynamic stabilisers" 

[edkyle99]

And here's a link to a graphic that shows their function.

http://s88.photobucket.com/albums/k166/suzymchale/mars-center/soyuz-abort.gif

They basically act like fins on a model rocket to keep the escaping module section aerodynamically stable.

 - Ed Kyle

Thanks Ed, but why would they want to aerobrake the whole escape system during the booster failure scenario, if they want to pull the crew safely away from the explosion? You know what I mean, pulling and braking. It doesn't make sense.

As the attached high resolution photo of Soyuz TMA-6 shows, the brakes look like "cheese graters".  They serve to move the center of air pressure back in a hurry, but don't actually block all of the air flow. These are used in some missles, where they are called "grid", or "lattice" fins. 

See, for example, http://viswiki.com/en/Grid_fin

 - Ed Kyle 

[ycs86]

As the attached high resolution photo of Soyuz TMA-6 shows, the brakes look like "cheese graters".  They serve to move the center of air pressure back in a hurry, but don't actually block all of the air flow. These are used in some missles, where they are called "grid", or "lattice" fins.

 - Ed Kyle 

Great explanation! Thanks again, Ed! Now I completely get this whole thing! The main goal is to make the projectile point constantly at the "target" (in this case predefined flight pad)

[Phillip Clark]

They are also seen on the payload shroud for the Zond/L-1 missions.

[Bernard de Go Mars]

Hi guys!

these "grid fins" work well as fins.

The problem is that one often thinks that they work as "air brakes", i.e. with their Drag, as they work producing a real normal lift.

And that's why, may be, you found  paradoxical that, at one side, rockets speed the Soyuz, while, at the other side, "air brakes" slow it !


That's why the name of "Lattice purposes" is preferable pedagogically.

As Stephan said, these lattice fins stabilize the Soyuz that is otherwise aerodynamically unstable (too heavy for its rear).


I spent a long study on this subject at the end of which I propose a simple method of calculating their Normal Lift (unfortunatly in French).

Friendly yours,

Bernard de Go Mars

[Nicolas PILLET]

I spent a long study on this subject at the end of which I propose a simple method of calculating their Normal Lift (unfortunatly in French).

Why do you say 'unfortunately' ?? 

[Bernard de Go Mars]

Hi Nicolas !
Thanks for your answer.

I wrote "unfortunately in French" because it is a kind of courtesy to the rest of the world (that is not supposed to speak French).

In fact, I used to write my text a majority of English texts.

This text can be download here :

http://inter.action.free.fr/tmp/gomars/PORTANCE_PANNEAUX_CELLULAIRES.pdf

I expect this text is something like 200 pages long !

Friendly,

Bernard de Go Mars

[Bernard de Go Mars]

Many people think that grid fins work as brakes. In fact this is not the case! : Grid fins really create a normal force which is quite simply calculable (at subsonic speed).

If gridfins functioned as brakes, the balance would be a disaster.

Friendly yours,

Bernard de Go Mars