ULA almost Kerbals it on Cygnus launch

[Vanamonde]

Man, with that many problems they should have just reverted to launch and started the whole thing over. 

[KerikBalm]

Any news on the reason the lower stage cut off 6 seconds early?

[wumpus]

On 3/30/2016 at 10:31 PM, Mitchz95 said:

I'm pretty sure that if the same thing happened to a Falcon 9, we would be calling an Almost Fail just as we are now.

And if ULA were the ones trying to land rocket stages, we would be cheering on every Almost Success just as we are now.

Anyway, the fact that Atlas V was able to recover from this says a lot about the quality of their rocket.

I haven't heard a peep about the Spacex January 6, 2014 launch that had "unacceptable margins for USAF launches" (this was a launch for Thaicom, but didn't help spacex  get any US DoD contracts).  Spaceflight looks pretty binary to outside observers, either everything works or you pick up pieces.

[Mitchz95]

10 minutes ago, wumpus said:

I haven't heard a peep about the Spacex January 6, 2014 launch that had "unacceptable margins for USAF launches" (this was a launch for Thaicom, but didn't help spacex  get any US DoD contracts).  Spaceflight looks pretty binary to outside observers, either everything works or you pick up pieces.

Probably because it was two years ago. I doubt anybody will be talking about this particular ULA mission in 2018, at least not in video game forums.

[sevenperforce]

3 hours ago, KerikBalm said:

Any news on the reason the lower stage cut off 6 seconds early?

Apparently they were adjusting the mixture ratio mid-ascent -- I'm not sure why -- and ran out of oxidizer 5.4 seconds earlier than planned. Not sure whether it flamed out or if the computer automatically triggered BECO due to a low LOX volume message. I'll see whether the launch videos are available online...if so, comparing this launch to the prior launch should show a noticeable difference at BECO if it was a flameout...probably a hot fuel-rich flare.

Does SpaceX use tighter margins? Yes. But with reusable first stages (or at least planned-reuse first stages), this would never happen; they have a comparably high volume of extra propellant left over for their landing attempt, so a launch anomaly can be compensated for with relative ease at the expense of narrower landing margins.

[Mazon Del]

http://news.yahoo.com/probe-ula-rocket-engine-early-215155316.html

So it IS getting a review done. The Air Force wasn't too happy about how close things came so they are participating.

[GeneCash]

From http://spaceflight101.com/ula-narrows-down-cause-of-atlas-v-performance-anomaly-in-recent-cygnus-launch

Quote

An interesting observation made in reviews of the video of last week’s launch is a sudden change in the shape and color of the first stage’s exhaust plume approximately 30 seconds prior to the premature Booster Engine Cutoff

So it sounds (to me) like yes, that was a mixture ratio change significant enough to show up as a change in the plume.

I'd think that's a pretty hefty mixture change since they don't usually show up like that. SWAG, of course.

I wonder if the computer went "oh sh*t, we're running out of O2! do something!"

And yes, the US Navy pretty much instantly asked for an investigation and delayed the MUOS-5 launch at least a week until it's figured out. The USAF is participating because they've got all the range data and telemetry.

[sevenperforce]

3 hours ago, GeneCash said:

From http://spaceflight101.com/ula-narrows-down-cause-of-atlas-v-performance-anomaly-in-recent-cygnus-launch

So it sounds (to me) like yes, that was a mixture ratio change significant enough to show up as a change in the plume.

I'd think that's a pretty hefty mixture change since they don't usually show up like that. SWAG, of course.

I wonder if the computer went "oh sh*t, we're running out of O2! do something!"

And yes, the US Navy pretty much instantly asked for an investigation and delayed the MUOS-5 launch at least a week until it's figured out. The USAF is participating because they've got all the range data and telemetry.

Crap. I was looking at the videos to see the moment of BECO to try and figure out whether it was a flame out or a planned cut off. Didn't think about looking earlier. 

[wumpus]

16 hours ago, GeneCash said:

From http://spaceflight101.com/ula-narrows-down-cause-of-atlas-v-performance-anomaly-in-recent-cygnus-launch

So it sounds (to me) like yes, that was a mixture ratio change significant enough to show up as a change in the plume.

I'd think that's a pretty hefty mixture change since they don't usually show up like that. SWAG, of course.

I wonder if the computer went "oh sh*t, we're running out of O2! do something!"

And yes, the US Navy pretty much instantly asked for an investigation and delayed the MUOS-5 launch at least a week until it's figured out. The USAF is participating because they've got all the range data and telemetry.

That screams sensor failure to me, but there must be a ton of other possibilities (turbo pumps not pumping enough (possibly due to their own control failures).  Software issue misreading the controls (or outputting the wrong values).  Amazing they could recover with a failure like that.

[StrandedonEarth]

On 3/31/2016 at 8:14 AM, sevenperforce said:

Not sure whether it flamed out or if the computer automatically triggered BECO due to a low LOX volume message

I don't know if the Atlas engines are the same as the SSME's, but as I understand it, allowing a rocket engine to run dry will result in a RUD, probably due to the turbopumps over-speeding. I remember the Shuttle had a lengthy delay when they had issues with the ECO (engine cut-off) sensors in the ET not reading properly. So the computers would have shut down the Atlas engines when the LOX was almost out, rather than let it run dry.

[Matuchkin]

Quote

Man, with that many problems they should have just reverted to launch and started the whole thing over. 

I told the staff dangit wasn't a good idea. They couldn't revert, they were playing career.

Edited April 2, 2016 by Matuchkin

[GeneCash]

7 hours ago, wumpus said:

Amazing they could recover with a failure like that.

I think it survived because basically the Atlas V/Centaur does indeed have a buttload of extra ΔV lofting the Cygnus to ISS... In this case, they just used it all. Remember how much ULA boasts about having a full hour launch window.

I think anything else, including the Falcon 9, would have reached "ocean-synchronous orbit" instead.

[fredinno]

35 minutes ago, GeneCash said:

I think it survived because basically the Atlas V/Centaur does indeed have a buttload of extra ΔV lofting the Cygnus to ISS... In this case, they just used it all. Remember how much ULA boasts about having a full hour launch window.

I think anything else, including the Falcon 9, would have reached "ocean-synchronous orbit" instead.

Falcon 9 would have more than enough Delta V for Dragon, it's very oversized for it. HOWEVER, a GEO sat launch would not be fine if it was exactly the same kind of failure, since all the extra Delta V is in the 1st stage, instead the 2nd stage, like on the Atlas V.

[GeneCash]

24 minutes ago, fredinno said:

Falcon 9 would have more than enough Delta V for Dragon, it's very oversized for it. HOWEVER, a GEO sat launch would not be fine if it was exactly the same kind of failure, since all the extra Delta V is in the 1st stage, instead the 2nd stage, like on the Atlas V.

Hm. Really good point... I didn't think about that. I guess the differences between launch vehicle manufacturers are a lot like the differences between KSP players!

[Mazon Del]

And indeed, even if the Falcon 9 flubbed the launch, it now has the capability to emergency eject the payload and activate the chutes during launch. I hope we don't need an "unplanned live test" of that capability anytime soon, but I also would love it if it worked that first time.

[sevenperforce]

1 hour ago, Mazon Del said:

And indeed, even if the Falcon 9 flubbed the launch, it now has the capability to emergency eject the payload and activate the chutes during launch. I hope we don't need an "unplanned live test" of that capability anytime soon, but I also would love it if it worked that first time.

You mean if either of the stages experience RUD, the Dragon V1 will now decouple and deploy chutes? Or are you talking about a suborbital injection?

[StrandedonEarth]

47 minutes ago, sevenperforce said:

You mean if either of the stages experience RUD, the Dragon V1 will now decouple and deploy chutes? Or are you talking about a suborbital injection?

As in when the Falcon 9 second stage failed (believed to be due to a substandard strut) during the first stage burn of a CRS launch last year, the Dragon could/should have been saved if only the computers had been programmed to deploy 'chutes during that contingency. That programming change has since been made. I wonder if they could have sent commands from the ground to save the Dragon.

Anyways, that was getting off topic. I wonder if ULA has figured out where their LOX went yet? Or why it burned so much at the end?

[fredinno]

11 hours ago, Mazon Del said:

And indeed, even if the Falcon 9 flubbed the launch, it now has the capability to emergency eject the payload and activate the chutes during launch. I hope we don't need an "unplanned live test" of that capability anytime soon, but I also would love it if it worked that first time.

Only for Dragons- which are payload-dependent, so that doesn't really count. If Dragon was on Atlas, it would probably be able to do the same thing too.

[GeneCash]

On 4/3/2016 at 0:01 PM, StrandedonEarth said:

I wonder if ULA has figured out where their LOX went yet? Or why it burned so much at the end?

Apparently not... The next Atlas V launch (MUOS-5) has been put on indefinite hold until they figure it out.

http://www.spaceflightinsider.com/organizations/ula/muos-5-mission-delayed-indefinitely-due-problems-encountered-oa-6-mission/

[GeneCash]

And apparently it's a "mixture ratio control valve that had Total Inability To Support Usual Performance (TITSUP) http://spaceflight101.com/cygnus-oa6/atlas-v-mrcv-valve-cuplrit-in-oa6-anomaly/

From what they say, it mostly shut off the fuel flow.

[fredinno]

4 hours ago, GeneCash said:

And apparently it's a "mixture ratio control valve that had Total Inability To Support Usual Performance (TITSUP) http://spaceflight101.com/cygnus-oa6/atlas-v-mrcv-valve-cuplrit-in-oa6-anomaly/

From what they say, it mostly shut off the fuel flow.

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