SpaceX F9 : Starlink 6 (v1.0 L5) : Mar. 18, 2020 - Discussion

[oiorionsbelt]

I also thought it interesting that the engines seemed to be gimbaling just before the first failure and that this might have been around the time of throttle-down.

I believe this is standard behavior in preparation for MECO, nulling out angle of attack to minimize drag-induced torque for stage separation. Prior to that it can fly a noticeable angle of attack, depending on mission trajectory. Some say the angle of attack increase after max-Q is trajectory shaping for gravity losses, others say it also produces aerodynamic lift, but it's not at all common for a F9 launch.

Common or uncommon. Sounds like you used the wrong word or am I reading this wrong?

[ugordan]

I also thought it interesting that the engines seemed to be gimbaling just before the first failure and that this might have been around the time of throttle-down.

I believe this is standard behavior in preparation for MECO, nulling out angle of attack to minimize drag-induced torque for stage separation. Prior to that it can fly a noticeable angle of attack, depending on mission trajectory. Some say the angle of attack increase after max-Q is trajectory shaping for gravity losses, others say it also produces aerodynamic lift, but it's not at all common for a F9 launch.

Common or uncommon. Sounds like you used the wrong word or am I reading this wrong?

Uncommon. You're right, typo. I'll edit the original post.

[gongora]

https://twitter.com/Free_Space/status/1242447475459395584

NASA reps from Commercial Crew program join @SpaceX investigation into premature shutdown of one of the 9 Merlin engines on the Falcon 9 that launched 3/18 on Starlink-6 mission.

From NASA: According to the CCtCap contracts, SpaceX is required to make available to NASA all data and resulting reports. SpaceX, with NASA’s concurrence, would need to implement any corrective actions found during the investigation related to its commercial crew work prior to its flight test with astronauts to the International Space Station. NASA and SpaceX are holding the current mid-to-late May launch timeframe, and would adjust the date based on review of the data, if appropriate.

[Vettedrmr]

With Starlink 7 coming up, did anyone hear anything about the cause behind 6's engine failure?

TIA, and have a good one,
Mike

[georgegassaway]

The stated design goal of 10 flights per booster was going to test the limits of the hardware at some point.

IIRC, the actual stated design goal was 100 flights, not 10.

With the actual stated design goal of 10 flights without major refurbishment.

[wannamoonbase]

The stated design goal of 10 flights per booster was going to test the limits of the hardware at some point.

IIRC, the actual stated design goal was 100 flights, not 10.

With the actual stated design goal of 10 flights without major refurbishment.

I assumed 'major refurbishment' meant new engines.

[Robotbeat]

The stated design goal of 10 flights per booster was going to test the limits of the hardware at some point.

IIRC, the actual stated design goal was 100 flights, not 10.

With the actual stated design goal of 10 flights without major refurbishment.

I assumed 'major refurbishment' meant new engines.

Poor assumption. Rehaul of the engines and a refurb of the TPS. Like what was done every flight for Shuttle.

[Lars-J]

The stated design goal of 10 flights per booster was going to test the limits of the hardware at some point.

IIRC, the actual stated design goal was 100 flights, not 10.

With the actual stated design goal of 10 flights without major refurbishment.

Citation please.

[Vettedrmr]

The stated design goal of 10 flights per booster was going to test the limits of the hardware at some point.

IIRC, the actual stated design goal was 100 flights, not 10.

With the actual stated design goal of 10 flights without major refurbishment.

Citation please.

https://spaceflightnow.com/2017/04/04/musk-previews-busy-year-ahead-for-spacex/

[georgegassaway]

Thanks, Vettedrmr for posting that link to the story that said this about block 5 three years ago. 
  How soon people forget. Now talking like 5 flights is about all SpaceX wants out of F9 anyway. Not true.

https://spaceflightnow.com/2017/04/04/musk-previews-busy-year-ahead-for-spacex/

SpaceX’s goal is to launch each Falcon 9 first stage 10 times with only inspections.

“Then, with moderate refurbishment that doesn’t have a significant effect on the cost, it can be reflown at least 100 times,” Musk said.

[marsbase]

Thanks, Vettedrmr for posting that link to the story that said this about block 5 three years ago. 
  How soon people forget. Now talking like 5 flights is about all SpaceX wants out of F9 anyway. Not true.

https://spaceflightnow.com/2017/04/04/musk-previews-busy-year-ahead-for-spacex/

SpaceX’s goal is to launch each Falcon 9 first stage 10 times with only inspections.

“Then, with moderate refurbishment that doesn’t have a significant effect on the cost, it can be reflown at least 100 times,” Musk said.

But note that Gwynne Shotwell said recently that it would not be necessary to fly more than 10 times since some customers required new boosters for their missions. 

[Robotbeat]

Typical for SpaceX to shoot for a really ambitious goal no one thinks is possible then end up only being able to do something less, but still dramatically better than the status quo.

[Paul_G]

https://twitter.com/raul74cz/status/1249715981842333696

Complete map of LHAs for #Starlink v1.0-L6 from LC-39A for Apr 16-21. Direct inject orbit, booster landing and expected fairing recovery location as last Starlink mission. Stage2 deorbit on the first orbit to same Debris Reentry Area in Eastern Pacific. bit.do/LHA11

Did I remember the previous 2 launches Placing the Starlink says (and stage 2) in an elliptical orbit, so that any failed sats (and stage 2)  re-entered quickly? If stage 2 is de-orbiting itself on the first orbit in the Pacific, this seems to imply a different launch profile?

[edkyle99]

Did I remember the previous 2 launches Placing the Starlink says (and stage 2) in an elliptical orbit, so that any failed sats (and stage 2)  re-entered quickly? If stage 2 is de-orbiting itself on the first orbit in the Pacific, this seems to imply a different launch profile?

Yes, the past two Starlink launches have used single burn direct ascents to slightly elliptical orbits with no deorbit burn following.  Presumably, this launch returns to the original 2-burn ascent plus deorbit burn?  Note that they failed to recover either of the direct-ascent first stages, though for differing reasons.

 - Ed Kyle

[Hummy]

Did I remember the previous 2 launches Placing the Starlink says (and stage 2) in an elliptical orbit, so that any failed sats (and stage 2)  re-entered quickly? If stage 2 is de-orbiting itself on the first orbit in the Pacific, this seems to imply a different launch profile?

Yes, the past two Starlink launches have used single burn direct ascents to slightly elliptical orbits with no deorbit burn following.  Presumably, this launch returns to the original 2-burn ascent plus deorbit burn?  Note that they failed to recover either of the direct-ascent first stages, though for differing reasons.

L5 booster second stage was de-orbited soon after the deployment. If it wasn't it would be the catalog. They injected L5 about 10 km lower than L4:

[scr00chy]

Small amount of isopropyl alcohol (cleaning fluid) was trapped in a sensor dead leg & ignited in flight

https://twitter.com/elonmusk/status/1252985622219960327

What the heck does he mean by "sensor dead leg"?

[OnWithTheShow]

What the heck does he mean by "sensor dead leg"?

Most likely a length of plumbing that splits off the main flow path and terminates in a sensor plug of some kind.

[Vettedrmr]

Small amount of isopropyl alcohol (cleaning fluid) was trapped in a sensor dead leg & ignited in flight

https://twitter.com/elonmusk/status/1252985622219960327

What the heck does he mean by "sensor dead leg"?

In pneumatic systems that I've worked on/with a "dead leg" is a length of pipe that is normally capped that can have a pressure sensor tapped into it, or remove the plug to drain condensation, etc.

Obviously not rocketry, but hopefully some concept of it.

And, apparently, a process failure, not a wear failure.

Have a good one,
Mike

[LouScheffer]

Small amount of isopropyl alcohol (cleaning fluid) was trapped in a sensor dead leg & ignited in flight

https://twitter.com/elonmusk/status/1252985622219960327

Presumably this must have been on the LOX side.  Seems unlikely alcohol could cause a fire when mixed with kerosine.

[DigitalMan]

Small amount of isopropyl alcohol (cleaning fluid) was trapped in a sensor dead leg & ignited in flight

https://twitter.com/elonmusk/status/1252985622219960327

What the heck does he mean by "sensor dead leg"?

In pneumatic systems that I've worked on/with a "dead leg" is a length of pipe that is normally capped that can have a pressure sensor tapped into it, or remove the plug to drain condensation, etc.

Obviously not rocketry, but hopefully some concept of it.

And, apparently, a process failure, not a wear failure.

Have a good one,
Mike

When I was a kid I sometimes worked with my dad doing new construction.  On water pipes running to a sink he used a tee to run a short length upwards from the point where it would branch off to the sink and cap it off so that there would be some cushion to stop pipes from banging when the water is shut off at the sink.