Author Topic: OA-6 Atlas V anomaly discussion and updates  (Read 101645 times)

Offline Chris Bergin

Re: OA-6 Atlas V anomaly discussion and updates
« Reply #100 on: 04/29/2016 01:02 pm »
Update from ULA - I'll write it up:

Centennial, Colo., (April 29, 2016) -- ULA successfully delivered the OA-6 Cygnus spacecraft to its precise orbit as planned on March 22. During the launch, the system experienced a premature first stage shutdown. Atlas is a robust system. The Centaur upper stage compensated for the first stage anomaly, delivering Cygnus to a precise orbit, well within the required accuracy. The ULA engineering team has reviewed the data and has determined an anomaly with the RD-180 Mixture Ratio Control Valve (MRCV) assembly caused a reduction in fuel flow during the boost phase of the flight. In addition to analysis and testing, all RD-180 engines are being inspected.

 

Last Friday, in preparation for the MUOS-5 launch, the Atlas V completed the Launch Vehicle on Stand (LVOS) operation, erecting the Atlas V into the Vertical Integration Facility at Cape Canaveral Air Force Station. LVOS will allow configuration of the vehicle to support RD-180 engine inspections and confirm all engine components are ready for launch. The Atlas V MUOS-5 launch is targeted for early summer; a new launch date has not been secured on the Eastern Range. The impact to the remainder of the Atlas V manifest is in review with new launch dates being coordinated with our customers. All missions manifested for 2016 are expected to be successfully executed by the end of the year, including OSIRIS-REx, which will remain in early September to support its critical science window.
« Last Edit: 04/29/2016 01:09 pm by Chris Bergin »
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Offline yokem55

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #101 on: 04/29/2016 01:30 pm »
Update from ULA - I'll write it up:

Centennial, Colo., (April 29, 2016) -- ULA successfully delivered the OA-6 Cygnus spacecraft to its precise orbit as planned on March 22. During the launch, the system experienced a premature first stage shutdown. Atlas is a robust system. The Centaur upper stage compensated for the first stage anomaly, delivering Cygnus to a precise orbit, well within the required accuracy. The ULA engineering team has reviewed the data and has determined an anomaly with the RD-180 Mixture Ratio Control Valve (MRCV) assembly caused a reduction in fuel flow during the boost phase of the flight. In addition to analysis and testing, all RD-180 engines are being inspected.

 

Last Friday, in preparation for the MUOS-5 launch, the Atlas V completed the Launch Vehicle on Stand (LVOS) operation, erecting the Atlas V into the Vertical Integration Facility at Cape Canaveral Air Force Station. LVOS will allow configuration of the vehicle to support RD-180 engine inspections and confirm all engine components are ready for launch. The Atlas V MUOS-5 launch is targeted for early summer; a new launch date has not been secured on the Eastern Range. The impact to the remainder of the Atlas V manifest is in review with new launch dates being coordinated with our customers. All missions manifested for 2016 are expected to be successfully executed by the end of the year, including OSIRIS-REx, which will remain in early September to support its critical science window.
I know its a press release, but this isn't much of a description of a root cause. I hope we get more info.

Offline cscott

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #102 on: 04/29/2016 02:28 pm »
In particular, everyone seems to want to know: is this a Russian or an American problem?  ULA's press release makes it seem like a problem with the Russian side, but it's possible that foreign body ingestion or some issue during integration was the root cause.  I wouldn't be too surprised to see dueling press releases forthcoming.

Offline Chris Bergin

Re: OA-6 Atlas V anomaly discussion and updates
« Reply #103 on: 04/29/2016 02:40 pm »
And the article for the latest (based on the above, but has to be covered).

https://www.nasaspaceflight.com/2016/04/oa-6-atlas-v-booster-mrcv-anomoly/
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Offline baldusi

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #104 on: 04/29/2016 02:50 pm »
I'm pretty sure ITAR greatly simplifies the communications for solving this sort of anomalies.

Offline Lar

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #105 on: 04/29/2016 02:59 pm »
I'm pretty sure ITAR greatly simplifies the communications for solving this sort of anomalies.

I'm pretty sure your Sarcasm Ratio Control Valve (SRCV) is not working right...

Hats off to ULA, for sharing the info they have and for working to correct the problem, and for committing to maintain launches for all their 2016 customers, including a very key science payload, in the face of what must have been a very perplexing failure tree to analyse... (and that's 100% sincere)
« Last Edit: 04/29/2016 03:00 pm by Lar »
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Offline Lar

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #106 on: 04/29/2016 03:05 pm »
Centaur used, and maybe still uses, capacitance probes to detect propellant in its propellant utilization system.  Such probes provide a continuous reading, rather than a point result.  Early Atlas (the original Atlas) PU systems used an array of point sensors.  I'm not sure what Atlas 5 CCB uses.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680027035.pdf

A mixture ratio valve is visible in the attached RD-180 schematic.  Atlas "owns" the sensors, but all of the actual PU controls are part of the RD-180.

 - Ed Kyle
Ed (or others) I stared at that diagram for a while (awesome diagram by the way, nice find) and I can't find the MRCV, is it the thing marked MR Control EHA ???
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Offline oldAtlas_Eguy

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #107 on: 04/29/2016 03:12 pm »
The basic item is now Aerospace Corporation (AC) AF "advisers" get to make their recommendations to the AF as to whether the proposed correction is sufficient. Just for myself having been on the AF end of LV hardware procurement, this problem raises a ? on the accuracy of the data package from Russia on the engines from a QC standpoint. Another problem with the engines and the trusted quality of the engines by AC and the AF will go from current high to low.

It becomes another ? as to whether this inspection would even be able to detect the problem that had occurred. For any assurance as to the capability of an inspection to catch the problem the confidence level of the root cause of the anomaly must be very high >80%.

The next launch is NET late June and could easily be delayed until July. The range is busy during this summer and adding a new launch in may be very difficult. Launch assignment by the range eats a 5-7 day swath. First come first served. Meaning when you have a significant delay you have to take what is available, no bumping.

Offline Kabloona

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #108 on: 04/29/2016 03:20 pm »
Centaur used, and maybe still uses, capacitance probes to detect propellant in its propellant utilization system.  Such probes provide a continuous reading, rather than a point result.  Early Atlas (the original Atlas) PU systems used an array of point sensors.  I'm not sure what Atlas 5 CCB uses.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680027035.pdf

A mixture ratio valve is visible in the attached RD-180 schematic.  Atlas "owns" the sensors, but all of the actual PU controls are part of the RD-180.

 - Ed Kyle
Ed (or others) I stared at that diagram for a while (awesome diagram by the way, nice find) and I can't find the MRCV, is it the thing marked MR Control EHA ???

Yes, mixture ratio electro-hydraulic actuator (EHA) valve. See Section A. Engine Heritage and Description:

http://www.ulalaunch.com/uploads/docs/Published_Papers/Supporting_Technologies/Incorporation_of_RD-180_Failure_Response_Features_in_the_Atlas_V_Booster_Emergency_Detection_System_2011.pdf

Quote
It becomes another ? as to whether this inspection would even be able to detect the problem that had occurred. For any assurance as to the capability of an inspection to catch the problem the confidence level of the root cause of the anomaly must be very high >80%.

According to the paper above, the mixture ratio control electro-hydraulic valve is part of a closed hydraulic system that is exercised during hot fire acceptance test and expected to be relatively immune from contamination after the test firing since the hydraulic system is closed. So the valve would presumably have been tested at the component level, then tested again during the hot fire, presumably successfully both times. The paper says that the hot fire runs through mixture ratio extremes, so the valve would have been run through a range of operational settings.

So it sounds like a rigorous QA process in which the suspect valve would have been well-exercised before flight.
« Last Edit: 04/29/2016 04:08 pm by Kabloona »

Offline Star One

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« Last Edit: 04/29/2016 03:59 pm by Star One »

Offline oldAtlas_Eguy

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #110 on: 04/29/2016 04:25 pm »
Centaur used, and maybe still uses, capacitance probes to detect propellant in its propellant utilization system.  Such probes provide a continuous reading, rather than a point result.  Early Atlas (the original Atlas) PU systems used an array of point sensors.  I'm not sure what Atlas 5 CCB uses.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680027035.pdf

A mixture ratio valve is visible in the attached RD-180 schematic.  Atlas "owns" the sensors, but all of the actual PU controls are part of the RD-180.

 - Ed Kyle
Ed (or others) I stared at that diagram for a while (awesome diagram by the way, nice find) and I can't find the MRCV, is it the thing marked MR Control EHA ???

Yes, mixture ratio electro-hydraulic actuator (EHA) valve. See Section A. Engine Heritage and Description:

http://www.ulalaunch.com/uploads/docs/Published_Papers/Supporting_Technologies/Incorporation_of_RD-180_Failure_Response_Features_in_the_Atlas_V_Booster_Emergency_Detection_System_2011.pdf

Quote
It becomes another ? as to whether this inspection would even be able to detect the problem that had occurred. For any assurance as to the capability of an inspection to catch the problem the confidence level of the root cause of the anomaly must be very high >80%.

According to the paper above, the mixture ratio control electro-hydraulic valve is part of a closed hydraulic system that is exercised during hot fire acceptance test and expected to be relatively immune from contamination after the test firing since the hydraulic system is closed. So the valve would presumably have been tested at the component level, then tested again during the hot fire, presumably successfully both times. The paper says that the hot fire runs through mixture ratio extremes, so the valve would have been run through a range of operational settings.

So it sounds like a rigorous QA process in which the suspect valve would have been well-exercised before flight.
That only increases my anxiety over an inspection and the reliability of the test data.

Offline starsilk

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #111 on: 04/29/2016 04:48 pm »
funny. I just finished reading the thread on spacex's financial arrangements and I thought to myself - ahh, time for bad news from ULA.

or perhaps I'm just too cynical about politics.

Offline Lar

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #112 on: 04/29/2016 05:04 pm »
Maybe it's just me, but this seems like good news rather than bad. They moved from "we aren't sure" to "we know what it was" and they announced they are going to contain all of the 2016 launches. When's the last time SpaceX made a committment like that? :)
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Offline Lee Jay

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #113 on: 04/29/2016 05:08 pm »
Maybe it's just me, but this seems like good news rather than bad. They moved from "we aren't sure" to "we know what it was" and they announced they are going to contain all of the 2016 launches. When's the last time SpaceX made a committment like that? :)

I agree.

- An in-flight failure resulted in full mission success.
- Root cause has been identified.
- They are working to ensure the same failure doesn't happen again.
- They are planning to launch all their scheduled launches for this year, this year, and their one with a critical timing window on time.

Where's the bad news?

Offline FutureSpaceTourist

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #114 on: 04/29/2016 05:21 pm »
Determining an anomaly isn't necessarily a root cause, but I assume ULA wouldn't be making the press release unless they had the root cause and can thus make the commitment to not defer launches to next year?

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #115 on: 04/29/2016 05:26 pm »
I know its a press release, but this isn't much of a description of a root cause. I hope we get more info.
If/when they determine root cause they may or may not share it.  ULA got really lucky on this mission.  Had engine shut off a little earlier, would not have gotten to correct orbit.  Had it kept burning a little longer, could have possibly blown up the engine.

Offline MarekCyzio

Re: OA-6 Atlas V anomaly discussion and updates
« Reply #116 on: 04/29/2016 05:51 pm »
Where's the bad news?

Valve issue can be caused by either quality control or design failure. Quality control failure means ULA may no longer trust RD-180's - what else could have slipped through cracks? Design failure means RD-180 needs to have something (valve? hydraulic pump?) redesigned before it can fly again. And it may take a while.

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #117 on: 04/29/2016 06:02 pm »
Exactly. I don't understand how this can be viewed as particularly good news. The narrowing-down of the fault to the engine also comes at a bad time politically as it might give more ammo to certain politicians who want to dump the RD-180 as soon as yesterday. "See, the engine is unreliable anyway!"

Offline Lar

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #118 on: 04/29/2016 06:10 pm »
Exactly. I don't understand how this can be viewed as particularly good news. The narrowing-down of the fault to the engine also comes at a bad time politically as it might give more ammo to certain politicians who want to dump the RD-180 as soon as yesterday. "See, the engine is unreliable anyway!"
I don't believe there has ever been a perfect engine yet (with any kind of service history). Even when you factor out initial development failures. Even after this anomaly the RD-180 is a reliable engine. I'm not a fan of it, but that's not why.

 And I guess the best news would have been if this never happened, but I still think finding the cause is better news than ULA announcing "we still don't know the cause and we are no longer willing to commit to OSIRIS-REX launching on time and the rest of 2016 is also at risk"

YMMV of course. And I'm bemused that I'm defending ULA here :)...
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Offline Rocket Science

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Re: OA-6 Atlas V anomaly discussion and updates
« Reply #119 on: 04/29/2016 06:17 pm »
I'm curious about the history of these engines with anomalies... Were they produced in the same time frame and if so when?
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