FAILURE: Soyuz-2.1b/Fregat-M – Meteor-M 2-1 et al. – Vostochny - Nov 28, 2017

[russianhalo117]

I've got to say that it would have taken extraordinary evidence to point a finger at the Soyuz-2. From all accounts, the mission was running nominally right up to the point Fregat was in free flight and apparently had some kind of electronic nervous breakdown.

Separation malfunction or some unexpected rotation rate prior to separation could certainly have been a contributing factor (I'm not suggesting this was the case).  There's no requirement that failures are single point.

that has pretty much been ruled out at this point. The data from Fregat-M on the flight clearly points to the inertial guidance system trying to align the upper stack to the correct orientation for the first burn but the flight computer overrode the IGS and sent additional commands to continue the rotation at which point the 2 sets of gyros experienced full gyro lock and an control was lost before the burn even started. That much is known at this point.

Ben, the guy I was replying to, was saying that it would have taken "extraordinary evidence" to implicate Soyuz, I was just pointing out that there were plenty of ways in which it was theoretically possible for Soyuz to have been involved in the failure.  I wasn't suggesting that any of them were true in this particular.  Based on released data and statements it seems that none of them apply, but I'm sure they were all investigated prior to "clearing" Soyuz.  Thanks for clarification anyways.

Well if we go back to the roots R-7 and R-7A were originally designed to be deployed all over the Soviet motherland although this never ended up being carried out. If data and capability was in fact transferred to each successive generation of R-7 based launcher then launch sites inside Russia would not be of issue.

[pargoo]

Best launch pic I've found so far.

[Liss]

The 2 Gyro platforms are aligned before liftoff just like an airplanes INU's . The 2 gyro platforms do not interact with each other upon liftoff until the Soyuz third stage triggers its shutdown and separation auto-command sequence and hands command and control over to Fregats Gyro Platform and Main computer.

You haven't answer any of my questions.
What is azimuth in this context? Why it is 174 degrees for Vostochny and less then 140 degrees for Baykonur for example?
When is Soyuz gyro platform rotated from 174 degrees back to a zero position and why?
Is this rotation related to the rocket body roll for somewhat like 180 degrees soon after liftoff which is observed in video?
What does the Fregat gyro platform do at the same time as the Soyuz gyro platform rotates?

[AncientU]

I've got to say that it would have taken extraordinary evidence to point a finger at the Soyuz-2. From all accounts, the mission was running nominally right up to the point Fregat was in free flight and apparently had some kind of electronic nervous breakdown.

Separation malfunction or some unexpected rotation rate prior to separation could certainly have been a contributing factor (I'm not suggesting this was the case).  There's no requirement that failures are single point.

that has pretty much been ruled out at this point. The data from Fregat-M on the flight clearly points to the inertial guidance system trying to align the upper stack to the correct orientation for the first burn but the flight computer overrode the IGS and sent additional commands to continue the rotation at which point the 2 sets of gyros experienced full gyro lock and an control was lost before the burn even started. That much is known at this point.

Ben, the guy I was replying to, was saying that it would have taken "extraordinary evidence" to implicate Soyuz, I was just pointing out that there were plenty of ways in which it was theoretically possible for Soyuz to have been involved in the failure.  I wasn't suggesting that any of them were true in this particular.  Based on released data and statements it seems that none of them apply, but I'm sure they were all investigated prior to "clearing" Soyuz.  Thanks for clarification anyways.

How did they 'clear' the pre-flight quality control?
Maybe they assume it cannot (or need not) be improved...

Astounding that they plan to continue launches straight away.

[koshvv]

I hope I recall it right. Corrections are welcome.

What is azimuth in this context?

It's the angle between launch direction and direction "bottom" block is facing, as depicted on attached images.

Why it is 174 degrees for Vostochny and less then 140 degrees for Baykonur for example?

Look at attached schemes.

When is Soyuz gyro platform rotated from 174 degrees back to a zero position and why?

Rocket rotates shortly after liftoff. Control system works in such way that rocket must have orientation with particular side booster facing launch direction. Then it will face ground as rocket pitches.
Only Soyuz 2 can do this. Older Souyz needs turning launch pad at required angle. Baikonur launch pads have rotating tables for this.

Is this rotation related to the rocket body roll for somewhat like 180 degrees soon after liftoff which is observed in video

This is it.

Edit: removed irrelevant scheme.

[Liss]

koshvv, thank you very much for clarification.
So, when Soyuz rolls 174° counterclockwise (to the right) its gyro platform changes position from 174° to 0°, is it correct?
In this case I assume that at the same time, in the same roll Fregat gyro platform changes position from 184° to 10°, is it correct?

[koshvv]

So, when Soyuz rolls 174° counterclockwise (to the right) its gyro platform changes position from 174° to 0°, is it correct?

Yes.

In this case I assume that at the same time, in the same roll Fregat gyro platform changes position from 184° to 10°, is it correct?

I don't really know about Fregat.

[Stan Black]

Trying to get my head around this. The Soyuz roll from Baikonur is opposite to the other launch sites? Problem with Vostochny is that the Fregat requires a roll of 184°? Soyuz provides 174° of roll. The Fregat expects that to happen in the opposite direction?

[russianhalo117]

Trying to get my head around this. The Soyuz roll from Baikonur is opposite to the other launch sites? Problem with Vostochny is that the Fregat requires a roll of 184°? Soyuz provides 174° of roll. The Fregat expects that to happen in the opposite direction?

I believe that fregat gyro platform can accept either which is a problem for Fregat Main Computer which overrode the gyros and initiated a further 360 degree roll because the main computer wanted to reach 0 degrees first because It did not want to sit go via 360 degrees. This resulted in the complete stalling and loss of the Gyro Platform because one of the gyros rings cannot rotate a full 360 degrees rapidly. This is related to Briz US Family as the Gyros I think are from the same manufacturer.

[Danderman]

I have the feeling that there is some confusion between roll and yaw in this discussion.  If the Fregat control system failed due to excessive roll, the engine would still be pointed in the correct direction. If Fregat failed due to excess yaw, then no, the engine would be pointed in the wrong direction at the time of failure, most likely.

[Sam Ho]

Trying to get my head around this. The Soyuz roll from Baikonur is opposite to the other launch sites? Problem with Vostochny is that the Fregat requires a roll of 184°? Soyuz provides 174° of roll. The Fregat expects that to happen in the opposite direction?

I believe that fregat gyro platform can accept either which is a problem for Fregat Main Computer which overrode the gyros and initiated a further 360 degree roll because the main computer wanted to reach 0 degrees first because It did not want to sit go via 360 degrees. This resulted in the complete stalling and loss of the Gyro Platform because one of the gyros rings cannot rotate a full 360 degrees rapidly. This is related to Briz US Family as the Gyros I think are from the same manufacturer.

Not knowing any details of how the Soyuz and Fregat guidance software is written, it sounds like for a launch from Vostochny to SSO, the Soyuz requires a post-launch roll program of 174°.  Meanwhile, the Fregat IMU is clocked 10° off from Soyuz, so it has a roll angle of 10° on the pad and a roll target of 184°, which it translated to -176°.  The Fregat flight software is in monitoring mode until stage separation, propagating its state vector, and adds the 174° roll flown by Soyuz to its initial roll angle of 10°.  At separation, the Fregat notes its roll angle of 184°, compares it to the -176° target, and commands a -360° roll, which results in gyro lockup and loss of attitude reference.

[koshvv]

Trying to get my head around this. The Soyuz roll from Baikonur is opposite to the other launch sites?

Sorry, I should have mention Soyuz 2 was never actually launched from Site 1. It's theoretical situation.
Site 31 was used for all Soyuz 2 launches from Baikonur.

Problem with Vostochny is that the Fregat requires a roll of 184°? Soyuz provides 174° of roll. The Fregat expects that to happen in the opposite direction?

Anatoly Zak seems to say this. I fail to understand what happened.
What we can see, however, is when launching due North from Vostochny site, angles may be over 180 for Fregat and under 180 for Soyuz, while for all other sites both angles should be either over or under 180 degrees.   

Here also is Plesetsk Site 43 https://www.google.ru/maps/@62.9277848,40.454042,469m/data=!3m1!1e3?hl=en
Flame ducts on pads are oriented North like Kourou and NW like Baikonur Site 31.

I too can't understand how this peculiarity of Vostochny pad caused trouble, if it did at all.

[koshvv]

Not knowing any details of how the Soyuz and Fregat guidance software is written, it sounds like for a launch from Vostochny to SSO, the Soyuz requires a post-launch roll program of 174°

[Danderman]

I guess everyone has forgotten that at stage separation, it is not usual for some roll to be imparted, and so if the upper stage avionics cannot compensate for some "unexpected" roll, there will be lots of failures. Same with pitch and yaw.

[Sam Ho]

I guess everyone has forgotten that at stage separation, it is not usual for some roll to be imparted, and so if the upper stage avionics cannot compensate for some "unexpected" roll, there will be lots of failures. Same with pitch and yaw.

The theory Anatoly Zak's sources and others are discussing is not about tip-off rates induced at separation.  Rather, it is about Fregat attempting to null out a fictitious 360° roll angle error.

[Liss]

I guess everyone has forgotten that at stage separation, it is not usual for some roll to be imparted, and so if the upper stage avionics cannot compensate for some "unexpected" roll, there will be lots of failures. Same with pitch and yaw.

The theory Anatoly Zak's sources and others are discussing is not about tip-off rates induced at separation.  Rather, it is about Fregat attempting to null out a fictitious 360° roll angle error.

While I believe the story of Fregat trying to roll into correct position via long way (close but less than 360°) is true I think the explanation of this event by Anatoliy Zak is wrong. 

[YzeStudent]

...

When is Soyuz gyro platform rotated from 174 degrees back to a zero position and why?....

Just to be correct in terms… The gyro platform is not rotated. The IMU provides to the LV the inertial coordinate system fixed at liftoff. LV itself performs rotation relative to this coordinate system.

[Arch Admiral]

The diagrams by koshvv seem to assume that all launch azimuths are due north, wheras most Soyuz pads have launched into many different orbital inclinations, each of which requires a different launch azimuth. The exception is the one at Kourou, which always launches a little south of due east even though the launch complex is oriented N-S (Why?).

The part of the story which really makes no sense is having the zero angle in any coordinate different for the two guidance systems.
This is just asking for trouble.

[Liss]

The diagrams by koshvv seem to assume that all launch azimuths are due north, wheras most Soyuz pads have launched into many different orbital inclinations, each of which requires a different launch azimuth. The exception is the one at Kourou, which always launches a little south of due east even though the launch complex is oriented N-S (Why?).

The part of the story which really makes no sense is having the zero angle in any coordinate different for the two guidance systems.
This is just asking for trouble.

1. At least three different launch azimuths have been used in Kourou -- for GTO, Galileo and SSO orbits.
2. In this picture from Soyuz manual we see that axes of Soyuz and Fregat are parallel.

[koshvv]

The diagrams by koshvv seem to assume that all launch azimuths are due north

There are no assumptions. It's merely an illustration on how you measure angle of post-liftoff roll. Failed launch was to SSO, so roughly North was better fitting for purpose of illustration.

, wheras most Soyuz pads have launched into many different orbital inclinations, each of which requires a different launch azimuth.

You can draw any other launch azimuth and measure angle in a way depicted - between launch azimuth and Block B orientation. For Kourou it will be difference between 135 degrees clockwise (SE) and launch azimuth.

The exception is the one at Kourou, which always launches a little south of due east even though the launch complex is oriented N-S (Why?).

No, not always. Look at Sentinel-1A or Pleiades launch. You can't reach SSO launching East, you must launch almost due North. If you need to reach GTO orbit, launch East. Launch roughly NE if you delivering Galileo sats.