Author Topic: Dnepr question: Upperstage flying "backwards"  (Read 5299 times)

Offline Skyrocket

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Dnepr question: Upperstage flying "backwards"
« on: 08/05/2009 11:35 AM »
Is there any advantage by using the upperstage "backwards" - i.e. having the upperstage pulling the payload instead of pushing it as usual?

http://www.kosmotras.ru/en/shema_polet/

Has probably something to do with its past as an ICBM post boost stage.

BZW, are ther any other ICBMs with such kind of post boost module / upper stage?

Offline edkyle99

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #1 on: 08/05/2009 02:25 PM »
Is there any advantage by using the upperstage "backwards" - i.e. having the upperstage pulling the payload instead of pushing it as usual?

http://www.kosmotras.ru/en/shema_polet/

Has probably something to do with its past as an ICBM post boost stage.

BZW, are ther any other ICBMs with such kind of post boost module / upper stage?

My guess would be stability, to improve precision pointing for RV injection, with the center of gravity forward to reduce yaw/pitch rates, etc..  It acts like a tractor rocket, like Goddard's first rocket, or Faget's Mercury escape rocket, etc.

 - Ed Kyle
« Last Edit: 08/05/2009 02:25 PM by edkyle99 »

Offline Danderman

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #2 on: 08/05/2009 03:11 PM »
This allows the upper stage to drop off individual payloads while the engines are still firing, with the requirement for some sort of propulsion for the payloads (which would affect their final trajectory). This would be very useful for a mission where some 10 individual payloads would have to be precisely targeted. Gee, I wonder what kind of mission that would be?

The former USSR developed such capabilities for their MIRV program. The Strela launcher also has a MIRV bus for an upper stage, although Strela has not flown into orbit for a very long time.  The problem with these MIRV buses for orbital launch is that they are very inefficient, for example, the Dnepr is virtually a Saturn I class LV, based on its first stage performance, but usually injects less than 400 kg into orbit (although its max performance is around 4,000 kg). If Dnepr featured a Centaur class upper stage, it would rival the EELV for GEO missions.

Offline Danderman

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #3 on: 08/05/2009 03:12 PM »
BTW, flying backwards into orbit requires the Dnepr to cover the cargo with a Gas Dynamic Shield, which is jettisoned just before the payloads are released. This further degrades performance of Dnepr.

Offline Nicolas PILLET

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #4 on: 07/10/2014 08:26 PM »
Since there is no thread dedicated to Dnepr launcher, I will post here.

In the 2013 annual report of NPO Energomach, it is written that RD-263 engines for Dnepr's first stage is produced in Dnepropetrovsk ! A fact that I was completely unaware !

Quote
Из 156 ЖРД разработки НПО Энергомаш - 11 шт. (РД171М, РД-180 и РД-191) было произведено в НПО Энергомаш, а остальные на серийных заводах в г. Самара (75 шт. - 11Д511, 11Д512, 14Д22, 14Д21), г. Пермь (60 шт. - РД-276) и на Украине в г. Днепропетровск (2 шт. - РД-120, 8 шт. - РД-263).
Nicolas PILLET
Kosmonavtika : The French site on Russian Space

Offline baldusi

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #5 on: 07/11/2014 02:07 AM »
After this thread necromancy, I'll try to add some speculation. I had heard that the stage flies "backwards" because when it acts as an ICBM, the stage is actually used to slow down the payload. this allows it to have a higher maximum speed and thus a lower trip time, which is critical for minimizing the response window. Btw, I had always understood that this was an Ukrainian rocket, mostly.

Offline Danderman

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #6 on: 07/11/2014 05:47 AM »
After this thread necromancy, I'll try to add some speculation. I had heard that the stage flies "backwards" because when it acts as an ICBM, the stage is actually used to slow down the payload. this allows it to have a higher maximum speed and thus a lower trip time, which is critical for minimizing the response window. Btw, I had always understood that this was an Ukrainian rocket, mostly.

This cannot be a real explanation.

The Dnepr final stage only operates during the launch phase, within 8 minutes or so, the stage is dead. Therefore, it cannot be used just before entry into the atmosphere to slow the payloads down.

BTW, why would the Russian military want to slow the payloads down prior to atmospheric entry?


Offline osiossim

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #7 on: 07/11/2014 06:50 AM »
The attached Bulava image must be self-explanatory. The trajectory and backward flight technology is inherited from SS-20 aka Dnepr.
« Last Edit: 07/11/2014 06:52 AM by osiossim »

Offline pippin

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #8 on: 07/11/2014 07:19 AM »

BTW, why would the Russian military want to slow the payloads down prior to atmospheric entry?

Doing that allows you to fly a much lower and faster trajectory.
You fly with almost orbital speed that would make the warheads overshoot the target when ballistic but you then slow them down.
It's also much harder to predict the actual target from the early trajectory

Online owais.usmani

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #9 on: 07/11/2014 07:49 AM »
Since there is no thread dedicated to Dnepr launcher, I will post here.

In the 2013 annual report of NPO Energomach, it is written that RD-263 engines for Dnepr's first stage is produced in Dnepropetrovsk ! A fact that I was completely unaware !

Quote
Из 156 ЖРД разработки НПО Энергомаш - 11 шт. (РД171М, РД-180 и РД-191) было произведено в НПО Энергомаш, а остальные на серийных заводах в г. Самара (75 шт. - 11Д511, 11Д512, 14Д22, 14Д21), г. Пермь (60 шт. - РД-276) и на Украине в г. Днепропетровск (2 шт. - РД-120, 8 шт. - РД-263).

But why do they need to produce RD-263 anymore? When was the last R-36 manufactured, 1990?

Offline GClark

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #10 on: 07/11/2014 08:02 AM »
The attached Bulava image must be self-explanatory. The trajectory and backward flight technology is inherited from SS-20 aka Dnepr.

A gentle correction, sir...

R-36M Dnepr is designated SS-18 Satan.

SS-20 was the designation for the Temp-2S.

Respectfully,

Offline baldusi

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #11 on: 07/11/2014 01:11 PM »

Since there is no thread dedicated to Dnepr launcher, I will post here.

In the 2013 annual report of NPO Energomach, it is written that RD-263 engines for Dnepr's first stage is produced in Dnepropetrovsk ! A fact that I was completely unaware !

Quote
Из 156 ЖРД разработки НПО Энергомаш - 11 шт. (РД171М, РД-180 и РД-191) было произведено в НПО Энергомаш, а остальные на серийных заводах в г. Самара (75 шт. - 11Д511, 11Д512, 14Д22, 14Д21), г. Пермь (60 шт. - РД-276) и на Украине в г. Днепропетровск (2 шт. - РД-120, 8 шт. - РД-263).

But why do they need to produce RD-263 anymore? When was the last R-36 manufactured, 1990?
Tsyklon-4, perhaps?

Offline Skyrocket

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Re: Dnepr question: Upperstage flying "backwards"
« Reply #12 on: 07/11/2014 01:35 PM »

Since there is no thread dedicated to Dnepr launcher, I will post here.

In the 2013 annual report of NPO Energomach, it is written that RD-263 engines for Dnepr's first stage is produced in Dnepropetrovsk ! A fact that I was completely unaware !

Quote
Из 156 ЖРД разработки НПО Энергомаш - 11 шт. (РД171М, РД-180 и РД-191) было произведено в НПО Энергомаш, а остальные на серийных заводах в г. Самара (75 шт. - 11Д511, 11Д512, 14Д22, 14Д21), г. Пермь (60 шт. - РД-276) и на Украине в г. Днепропетровск (2 шт. - РД-120, 8 шт. - РД-263).

But why do they need to produce RD-263 anymore? When was the last R-36 manufactured, 1990?
Tsyklon-4, perhaps?

Tsikon-4 does not use the RD-263, but uses the RD-261, which is a completely different engine.

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