Soyuz / R-7 Strap-on Booster Sep

[Citabria]

A question that Korolev's team answered more than fifty years ago, but I have not seen a satisfactory answer: How do the R-7/Soyuz strap-on boosters separate in flight? Do they simply slip backward out of their forward sockets when thrust is cut off and the aft straps detach? (I saw a film once of a failed launch where one of the boosters lost thrust and slid downward and the rest of the rocket flew for some time before failing!) Does the release of LOX tank pressure push the boosters' noses away from the core? Are there pyrotechnics involved?

[DarthVader]

Hello Citabria,

AFAIK, you are correct on both accounts. Once the thrust of the strap-on starts to decay to the point that its lower than its weight, the strap which hold the strap-on at the base is cut (pyrotechnics) and the strap-on simply fall away, with some gentle push from a valve venting LOX (near the tip of the block), to make sure it rotate away from the core block.

Hope this help.

[Citabria]

Hi, Darth,

Thanks for replying again. Yes, it's me again with the same question I posted a few months ago and you answered back then. Do you know if there are any tech docs out there about this?

About the LOX vent push: Watching recent Soyuz launches on NASA-TV, even though the views were low magnification, I've seen the boosters tumble pretty quickly after sep. Could the vent push that hard? Or are aerodynamics helping the tumble?

[DarthVader]

Citabria - 25/3/2008  9:38 AM

Thanks for replying again. Yes, it's me again with the same question I posted a few months ago and you answered back then. Do you know if there are any tech docs out there about this?

No worries . As for the document(s), well no. I'd love to find any describing this in details, but there's nothing available that I know off.

About the LOX vent push: Watching recent Soyuz launches on NASA-TV, even though the views were low magnification, I've seen the boosters tumble pretty quickly after sep. Could the vent push that hard? Or are aerodynamics helping the tumble?

 

I'm no aerodynamics expert, but yeah I do believe that it will play a role as well as the decaying thrust which is likely offset from the strap-on center of gravity.

[Rusty_Barton]

The is a Soyuz users manual for payload planners:

http://www.starsem.com/services/images/soyuz_users_manual_190401.pdf

[DarthVader]

Rusty_Barton - 25/3/2008  10:33 AM

The is a Soyuz users manual for payload planners:

http://www.starsem.com/services/images/soyuz_users_manual_190401.pdf

That's right, but it doesn't go into much details regarding how the flight sequence goes, especially the question at hand.

[Rusty_Barton]

DarthVader - 25/3/2008  10:47 AM

Rusty_Barton - 25/3/2008  10:33 AM

There is a Soyuz users manual for payload planners:

http://www.starsem.com/services/images/soyuz_users_manual_190401.pdf

That's right, but it doesn't go into much details regarding how the flight sequence goes, especially the question at hand.

But it does have a lot of pretty pictures.

[Citabria]

Rusty_Barton - 25/3/2008  10:20 PM

DarthVader - 25/3/2008  10:47 AM

Rusty_Barton - 25/3/2008  10:33 AM

There is a Soyuz users manual for payload planners:

http://www.starsem.com/services/images/soyuz_users_manual_190401.pdf

That's right, but it doesn't go into much details regarding how the flight sequence goes, especially the question at hand.

But it does have a lot of pretty pictures.

And lots of other good info. Thanks. I knew they use H2O2 for the turbos (a la V2), but not that they use LN2 for pressurization.

[DarthVader]

Citabria - 26/3/2008  9:08 AM
And lots of other good info. Thanks. I knew they use H2O2 for the turbos (a la V2), but not that they use LN2 for pressurization.

Yep, the LN2 is converted to gaseous form by running trough the turbine exhaust.

[Citabria]

DarthVader - 26/3/2008  12:47 PM

Citabria - 26/3/2008  9:08 AM
And lots of other good info. Thanks. I knew they use H2O2 for the turbos (a la V2), but not that they use LN2 for pressurization.

Yep, the LN2 is converted to gaseous form by running trough the turbine exhaust.

Is that V2-tech too?

[DarthVader]

Citabria - 27/3/2008  10:24 AM
Is that V2-tech too?

Only partially I'll think, since the V-2 was carrying bottle of compressed N2, from which a part of it was used to pressurize the tanks (and maybe only the Alcohol), if I'm not mistaken. Please someone correct me on this.

[zerm]

Wow- this is the kind of information that we log onto NSF to read! THANK YOU both for the great question and the detailed answer!

[Citabria]

Last Soyuz launch on NASA TV had a nice, clear view of the "Korolev's Cross" booster sep, but the magnification was too small to see exactly what happens. NASA should lend them a nice tracking telescope!

The tumbling looked very fast. It was difficult to tell which way they tumbled because the view is nearly end-on. Right after sep I saw a white cloud at one end of each booster for less than one tumble. Would that be the GOX vent or residual fuel from the engines?

[Mark Dave]

It would be cool to have an onboard camera similar to those on the Shuttle ET/SRB looking down. It is a bit difficult to see exactly how it would visually look up close.  You know, too bad the strap on booster are junked. I read an article in a magazine of where they end up after use, simply destroyed upon impact and scrapped by locals that live near the impact area downrange from the launch site.  I think the boosters can be resused.

[clongton]

MarkD - 17/4/2008  4:37 PM

It would be cool to have an onboard camera similar to those on the Shuttle ET/SRB looking down. It is a bit difficult to see exactly how it would visually look up close.  You know, too bad the strap on booster are junked. I read an article in a magazine of where they end up after use, simply destroyed upon impact and scrapped by locals that live near the impact area downrange from the launch site.  I think the boosters can be reused.

Cheaper to build new. Let the locals have the scrap.

[eeergo]

Citabria - 15/4/2008  5:24 PM  Last Soyuz launch on NASA TV had a nice, clear view of the "Korolev's Cross" booster sep, but the magnification was too small to see exactly what happens. NASA should lend them a nice tracking telescope!  The tumbling looked very fast. It was difficult to tell which way they tumbled because the view is nearly end-on. Right after sep I saw a white cloud at one end of each booster for less than one tumble. Would that be the GOX vent or residual fuel from the engines?

Agreed, surprised no-one has put the funds to install a camera on any single Soyuz flight. I think the white cloud is just a condensation cloud because of the enormous decrease in pressure "behind" the spent boosters when they're tumbling and are face-on towards the air flow(although, on the other hand, that flow shouldn't be too substantial given the altitude... maybe it is some venting after all, though it somehow didn't look quite right to me) 

[anik]

The sequence of separation of lateral blocks of Soyuz rocket in flight was discussed on forum of Novosti kosmonavtiki magazine four years ago. I shall try to explain it here. Thanks to the user (Salo) from that forum, who has helped me to find the information there.

1. Control system sends simultaneously commands - the shutting off engine and the laceration of strap on the base of block.

2. Pyrobolts tear the strap on the base of block. The engine is still working (low thrust), so the bottom section of block deflects on few degrees and the lateral block begins to rotate around upper lock-socket till fixed angle.

3. The lateral block unhooks from the central block. Simultaneously the valve at the upper section opens for the venting of the pressurizing gas from the tank with liquid oxygen. This gas helps to separate the block from the second stage.

Image below is from http://bob-pot.narod.ru/dobr/rp4.jpg

[Citabria]

MarkD - 17/4/2008  4:37 PM
You know, too bad the strap on booster are junked. I read an article in a magazine of where they end up after use, simply destroyed upon impact and scrapped by locals that live near the impact area downrange from the launch site.

Check out these great photos:
http://todayspictures.slate.com/20060412/3.html

I'd love to have one of those unsmashed steering nozzles. Has anyone ever seen them on E-bay?

[Citabria]

anik - 20/4/2008  7:25 AM

The sequence of separation of lateral blocks of Soyuz rocket in flight was discussed on forum of Novosti kosmonavtiki magazine four years ago. I shall try to explain it here. Thanks to the user (Salo) from that forum, who has helped me to find the information there.

Thank you very much, Anik. That is exactly what I've been looking for. The explanation is consistent with all the bits of information I've seen about it, including the description in Siddiqi's book (quoted earlier by DarthVader). What confused me is which way they separate - nose-out or tail-out? Looks like it's both! They go tail-out first then venting turns them around nose-out. Interesting.

[clongton]

Citabria - 24/4/2008  1:27 PM

MarkD - 17/4/2008  4:37 PM
You know, too bad the strap on booster are junked. I read an article in a magazine of where they end up after use, simply destroyed upon impact and scrapped by locals that live near the impact area downrange from the launch site.

Check out these great photos:
http://todayspictures.slate.com/20060412/3.html

I'd love to have one of those unsmashed steering nozzles. Has anyone ever seen them on E-bay?

I looked over the pictures. There are 2 there that I find particularly disturbing.

1. A guy walking around a booster that fell into his back yard. The caption said this happens a lot. Have any fallen onto cars or homes?

2. A very pretty landscape with several dead cows lying there. The caption said that the soil is becoming polluted with rocket fuel from the dropped booster tanks.

This does not, in my mind, display the Russian program in a very good light. It's as if the people and their livelihoods are of no concern what-so-ever, like so much fodder to be disposed of. That’s just an opinion mind you. It’s the impression I get from these few photos.