Author Topic: Soyuz Q & A  (Read 32774 times)

Offline Danderman

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Soyuz Q & A
« on: 12/11/2009 09:10 PM »
I ran some numbers, and was surprised to find that the Soyuz launch vehicle is relatively insensitive to payload mass increases for very low orbits. By this I mean that if, for example, the mass of a Soyuz spacecraft were to be increased from the normal 7200 kg to, say, 8000 kg, with the resulting injection orbit accordingly lowered, the amount of propellant that the Soyuz spacecraft would have to use to make up the difference would be relatively trivial. This would result in an additional 800 kg of "free" payload (note that this works for Progress and Shenzhou, as well).

Let's assume that the initial orbit for Soyuz averages 220 km (its actually more like 190 x 245, which is significant and I will go into that shortly). What if added mass is provided to Soyuz so that it can't attain a 220 km orbit, but is instead only capable of reaching 185 km? For the Soyuz spacecraft to transfer from 185 km to 220, even with a total mass of 8000 kg, would cost 56 kg. Note that 56 kg cost results in 8000 kg additional payload mass.  Even taking into account that the additional 800 kg would then have to be transported from 220 km to the ISS 375 km orbit, the amount of prop expended for such maneuvers is relatively small.

Its turns out that the Shuttle launch architecture is pretty efficient at maximizing payload, and adds the safety feature that the OMS must work to get the Shuttle into a stable orbit; otherwise, if the Shuttle were injected into, say, a 220 x 220 km orbit, and the OMS were to fail to start, it would be a bit of wait for the Shuttle to get back to Earth (this is the case with Soyuz today, if the engines were to suffer infant mortality syndrome and not work at all, the Soyuz would require a decay time of at least half a week to get the crew back to Earth).

So, what if the Soyuz (assuming a mass of 8000 kg) were released from its launch vehicle some 50 m/s short of the current injection orbit? Once again, the amount of extra prop to get the Soyuz into the nominal orbit would be some 136 kg. Once that were burned, and Soyuz were back in a 220 km orbit, Soyuz would have a mass of 7864 kg, and the amount of prop to raise the orbit to ISS would only be about 235 kg.
In this case, prop would be very limited for maneuvers at ISS, which brings me to the next point: Soyuz could carry a rear prop tank, back where the ancient avionic torus tank used to be located. A rear prop tank would help considerably with controlability of Soyuz (with some additional 800 kg payload in the front); conversely, if this were not possible (due to lack of room in the back, or problems with a connecting a rear tank), another alternative would be to modernize the avionics compartment (ie empty it of all those ancient electronic) and put the resulting tiny boxes in the front (either the descent module or the orbital module) or simply shrink the compartment to the size of a shoebox, leaving an entire 2.2 wide area for an extra prop section behind the descent module.

If my math is correct, it would seem that Soyuz has enormous growth potential, if a new launch architecture were used, and if Soyuz electronics were modernized. In any event, significant electronics modernization that resulted in shrinkage of the avionics compartment mass would cause controlability problems even if nothing else were changed.

Now for the last point: using the 300 kg thrust Soyuz main engine for orbital injection rather than the launch vehicle final stage has another great benefit: as the Soyuz main engine burns prop at a lower rate than the rocket engine, the final orbit perigee would be much higher than in the current architecture, as the Soyuz rocket 3rd stage burns out about 190 km high (orbit perigee is a function of how high the vehicle is when the engines stop burning). This low perigee results in a very elliptical orbit, which is not a Good Thing. So, using the smaller Soyuz spacecraft engine for the final orbital burn would provide for a more circular injection orbit.

Last note on the Goodness of using the Soyuz main engine to achieve the initial orbit is that there is no reason not to utilize a higher initial orbit (since the Soyuz main engine can burn longer, and the fear of infant mortality syndrome sticking the crew into an orbit they can't get back from would not be a factor), so the Soyuz could be injected into say, a 250 km initial orbit, which would make tracking it from Russian territory during the early stages of flight much easier.

Having said all that, there are a boatload of technical issues, which is why this is in the Q & A:

A heavier Soyuz spacecraft would result in a slight movement of launch vehicle drop zones, to the west; how much I don't know. Its possible that the additional 800 kg would not affect the first and second stage drop zones much.

The Soyuz main engine would have to fire immediately upon separation from the 3rd stage, such a maneuver has been done, but only in a launch abort. I would imagine that its possible to program this burn with some confidence, but perhaps I am missing something. To wit:

to transfer from an injection trajectory some 20 m/s short of the current nominal orbit, the 300 kg Soyuz main engine (300 sec ISP) would have to burn for 20 seconds (someone here could do a sanity check on this calculation); if the burn were a few seconds short or long, or there was some start up delay, the result would still put the spacecraft into a functional orbit, and the likely dispersions are probably not that different from Soyuz launch vehicle dispersions for the nominal orbit anyway. However, the question of whether the Soyuz spacecraft has an adequate guidance system to "know" how long to burn, or to "know" if the launch vehicle under or overperformed, that is a good question. Without a "smart" flight computer with the appropriate sensors, its possible that the mission planners would have to rely on a simple timed burn for orbital injection (which begs the question as to how smart the Shuttle computers are, or whether the injection burn by OMS is simply pre-programmed).

In either architecture, the current one, or this alternative trajectory, Soyuz would conduct orbital trim burns on the 3rd/4th orbits to make up for any dispersions, and to get higher to avoid decay.

So apart from If It Ain't Broke, Don't Fix It, what the holes in this analysis?  Why doesn't Soyuz use the Shuttle launch architecture? Or Shenzhou?



« Last Edit: 12/11/2009 09:12 PM by Danderman »

Offline AlexInOklahoma

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Re: Soyuz Q & A
« Reply #1 on: 12/20/2009 05:12 PM »
A question concerning Soyuz launches and a listing of event sequences from today's 'Live Coverage' of TMA-17...

Regarding this portion: "L- 20 sec:   Ignition of 1st, 2nd stage engines at intermediate thrust level"

1st and 2nd stage is referring to the four 'boosters' as 1st and the inner 'core' as 2nd stage, right?  I see 'stages' named differently at different sites and am just clarifying terms used.  ~Same as saying Stage 0 and Stage 1 as well?  And the inner/centrally-located engine, which stays at ~'intermediate power' while boosters are lit (right?) becomes Stage Two (second Stage, per se) once the lateral boosters (and SAS 'abort things') are done/dropped and that inner engine *then* goes ~full-power, right?

Basically correct?  I searched around a bit and did not see anything specific on this, fwiw  :)

Alex

Offline Art LeBrun

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Re: Soyuz Q & A
« Reply #2 on: 12/20/2009 05:26 PM »
A question concerning Soyuz launches and a listing of event sequences from today's 'Live Coverage' of TMA-17...

Regarding this portion: "L- 20 sec:   Ignition of 1st, 2nd stage engines at intermediate thrust level"

1st and 2nd stage is referring to the four 'boosters' as 1st and the inner 'core' as 2nd stage, right?  I see 'stages' named differently at different sites and am just clarifying terms used.  ~Same as saying Stage 0 and Stage 1 as well?  And the inner/centrally-located engine, which stays at ~'intermediate power' while boosters are lit (right?) becomes Stage Two (second Stage, per se) once the lateral boosters (and SAS 'abort things') are done/dropped and that inner engine *then* goes ~full-power, right?

Basically correct?  I searched around a bit and did not see anything specific on this, fwiw  :)

Alex

The 4 strap ons are stage 1 and the center core is stage 2. I assume center core is at full thrust at liftoff since older technology did not ramp up thrust after liftoff.
1958 launch vehicle highlights: Vanguard TV-4 and Atlas 12B

Offline hop

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Re: Soyuz Q & A
« Reply #3 on: 12/20/2009 07:03 PM »
Many details of the Soyuz engines, include a description of the start sequence can be found at http://www.lpre.de/energomash/RD-107/index.htm (in russian, but google translate gets the gist)

Unrelated but perhaps of interest, here's an image of the TMA control panel, found VIA one TJ Creamers twitter followers:
http://img190.imageshack.us/img190/6874/soyuzinsidepanel.jpg

someone asked TJ about the "critical commands" section
"there are 22 cmds, so e.g.: Jettison BO; open depress valve of BO; Separation; Shut down Orbital Engine, Depress, etc..."

Offline Art LeBrun

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Re: Soyuz Q & A
« Reply #4 on: 12/20/2009 07:47 PM »
Thanks for the 107/108 link. Unfortunately the ENG button does not work.
1958 launch vehicle highlights: Vanguard TV-4 and Atlas 12B

Offline hop

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Re: Soyuz Q & A
« Reply #5 on: 12/20/2009 07:58 PM »
You can get the gist with http://translate.google.com/translate?js=y&prev=_t&hl=en&ie=UTF-8&layout=1&eotf=1&u=http%3A%2F%2Fwww.lpre.de%2Fenergomash%2FRD-107%2Findex.htm&sl=ru&tl=en

If the whole page doesn't translate, hitting refresh seems to get more of it. Of course, machine translation leaves a lot to be desired:
"Vomit explosive bolts in the oxidizer valve (controlled by the contacts)." ;)

Offline Art LeBrun

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Re: Soyuz Q & A
« Reply #6 on: 12/20/2009 08:10 PM »
That works much better. Thanks for your time.
1958 launch vehicle highlights: Vanguard TV-4 and Atlas 12B

Offline Danderman

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Re: Soyuz Q & A
« Reply #7 on: 12/25/2009 06:32 PM »
Reading the Soyuz LV Users Guide for Kourou, I noticed that the Fregat orbital transponder operates at 2860 Mhz, whereas the Ariane V transmits at 2200 MHz. Since I doubt that the existing Ariane V ground stations can adapt to 2860 Mhz, does this mean that Fregat's orbit determination system will be modified to transmit at 2200 Mhz? Such a change may have significant ramifications for the future, since it would allow European, commercial and Russian orbit determination systems to be unified.


Offline Jim

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Re: Soyuz Q & A
« Reply #8 on: 12/25/2009 07:22 PM »
Reading the Soyuz LV Users Guide for Kourou, I noticed that the Fregat orbital transponder operates at 2860 Mhz, whereas the Ariane V transmits at 2200 MHz. Since I doubt that the existing Ariane V ground stations can adapt to 2860 Mhz, does this mean that Fregat's orbit determination system will be modified to transmit at 2200 Mhz? Such a change may have significant ramifications for the future, since it would allow European, commercial and Russian orbit determination systems to be unified.


Ground stations are very adaptable.  The same stations support Atlas, Delta II, Pegasus, Ariane, etc. 

Offline Danderman

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Re: Soyuz Q & A
« Reply #9 on: 12/25/2009 08:53 PM »
Reading the Soyuz LV Users Guide for Kourou, I noticed that the Fregat orbital transponder operates at 2860 Mhz, whereas the Ariane V transmits at 2200 MHz. Since I doubt that the existing Ariane V ground stations can adapt to 2860 Mhz, does this mean that Fregat's orbit determination system will be modified to transmit at 2200 Mhz? Such a change may have significant ramifications for the future, since it would allow European, commercial and Russian orbit determination systems to be unified.


Ground stations are very adaptable.  The same stations support Atlas, Delta II, Pegasus, Ariane, etc. 

All of the western LVs listed above have transponders operating at 2200 Mhz, whereas Soyuz Fregat operates at 2860 Mhz, so I am not sure if the adaptation by a ground station is that trivial or even possible, compared to adapting the Fregat transponder.  I'm not a radio guy, so I don't know which is the easiest approach.

Offline NavySpaceFan

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Re: Soyuz Q & A
« Reply #10 on: 12/29/2009 01:06 PM »
Some questions re: Soyuz call signs, 1) when did the use of astronomical terms (Altair, Pulsar, etc.) start, 2) are they associated with a particular cosmonaut (I recall that Oleg Kotov used the same call sign during TMA-10 as he did during TMA-17), and 3) would the use of a name (i.e. GAGARIN or LEONOV) ever be considered?  Thanks!
<----First launch of DISCOVERY, STS-41D!!!!

Offline Jim

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Re: Soyuz Q & A
« Reply #11 on: 12/29/2009 03:18 PM »

All of the western LVs listed above have transponders operating at 2200 Mhz, whereas Soyuz Fregat operates at 2860 Mhz, so I am not sure if the adaptation by a ground station is that trivial or even possible, compared to adapting the Fregat transponder.  I'm not a radio guy, so I don't know which is the easiest approach.


The various launch vehicles use various methods to downlink data, analog, digital, PCM, etc.  They are very adaptable.

The same ground stations also receive spacecraft downlinks

Offline Danderman

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Re: Soyuz Q & A
« Reply #12 on: 12/29/2009 06:43 PM »
The various launch vehicles use various methods to downlink data, analog, digital, PCM, etc.  They are very adaptable.

The same ground stations also receive spacecraft downlinks

Most of the European ground stations that will be used for Soyuz LV launches use the Stella 43 antenna, which has a reception of 2200 - 2300 Mhz. I still don't know if the Fregat's transmission system will be revised to meet Stella 43 requirements, or exactly what is the plan.

Offline Danderman

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Re: Soyuz Q & A
« Reply #13 on: 01/04/2010 05:32 PM »
I figured it out all by myself. Fregat carries multiple telemetry and radar transponder systems. For operations in relatively low Earth orbit, Fregat uses the standard S-band frequencies around 2200 - 2300 Mhz, compatible with the CNES tracking network. Once Fregat raises its orbit so that it is in view of RSA ground stations, it uses the Russian ~ 2800 Mhz frequency for tracking, up to about 8000 km altitude. After that, it seems to use GPS and a "satellite navigation receiver" for position location.

AFAIK, Fregat has no uplink command capability, so there is no receiver required at high altitudes.

Offline Nicolas PILLET

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Re: Soyuz Q & A
« Reply #14 on: 02/11/2010 08:21 PM »
I have a question dealing with the Soyuz spacecraft.
In his book, translated by Asif Siddiqi, Boris Tchertok wrote a very interesting chapter on the Cosmos 133 mission (the very first flight of the Soyuz).

Page 606 :

Quote
Someone from among the thermal mode specialists came to the conclusion
that the hot jets of gas from the DPO nozzles would blow on the solar array
panels. They reported to Feoktistov. Without giving it much thought, he
proposed that they turn them on their support bracket 180 degrees about their
axis, so as not to undertake a complex modification of the spacecraft and look
for other sites to install the engines.

Do someone understand the past configuration of the DPO engines ? I don't understand how a 180-turn could prevent the engines from damaging the solar panels ?

Thanks !
Nicolas PILLET
Kosmonavtika : The French site on Russian Space

Offline TJL

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Re: Soyuz Q & A
« Reply #15 on: 02/24/2010 12:11 AM »
This September the new Soyuz TMA 01M is scheduled to fly on its first flight.

Why are they still flying the standard Soyuz TMA (20 and 21) after validating the new version, and once again (Soyuz TMA 22) after Soyuz TMA 02M?

Thank you.

Offline anik

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Re: Soyuz Q & A
« Reply #16 on: 02/24/2010 05:38 PM »
Why are they still flying the standard Soyuz TMA (20 and 21) after validating the new version, and once again (Soyuz TMA 22) after Soyuz TMA 02M?

Soyuz TMA-20 is back-up spacecraft for Soyuz TMA-01M. Soyuz TMA-22 is back-up spacecraft for Soyuz TMA-02M. As in past Progress M-66 was back-up cargo ship for Progress M-01M and Progress M-67 was back-up cargo ship for Progress M-02M. The first two flights of spacecrafts of new modifications are test flights, so there will be back-up spacecrafts.

Offline Danderman

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Re: Soyuz Q & A
« Reply #17 on: 02/24/2010 06:09 PM »
To explain it a different way, the Russian practice with a new spacecraft variant is to fly the new modification, but then fly the old model a couple of times more, to give the designers a little time to evaluate the performance of the new model before committing the new model to being the new standard.

« Last Edit: 02/24/2010 06:09 PM by Danderman »

Offline TJL

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Re: Soyuz Q & A
« Reply #18 on: 03/10/2010 12:20 AM »
Was wondering why the back up crew for next months Soyuz TMA 18 crew is comprised of crew members of two different prime crews?

Offline Nicolas PILLET

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Re: Soyuz Q & A
« Reply #19 on: 03/24/2010 08:22 PM »
Found in ISS Status Report of 18th march :

Quote
Tri-module separation occurred at 6:57am. 16 sec after the separation command, software pitched the PAO instrumentation/propulsion module in the rear to a specific angle (-78.5 deg from reference axis) which, if the PAO would have remained connected to the SA/Descent Module, would have resulted in enough heating on the connecting truss to melt it, thus ensuring separation.

Is it a new procedure, or an old one I did't know about ??
Nicolas PILLET
Kosmonavtika : The French site on Russian Space

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