SpaceX F9 : Starlink v1.0 Flight 3 : January 29, 2020 - Master Thread

[meekGee]

Usually the engines shut-off as the legs touch, and weight is transferred from engines to legs smoothly.

Here the rocket reaches zero velocity too high, the engines shut down (as they have no choice but to do), and the stage accelerates downwards before touching down.

Whether it used up all of the crush core or not is not clear.  It looks pretty rough.

Is is a known fact that leg contact with the deck is the only cue/signal for engine shutdown? It seems like it would also make sense to cue engine shutdown if the position information says th vehicle is your "zero" elevation, probably the nominal deck height above sea level, & the vehicle is also at zero vertical velocity.

When you look at the deck height vs. horizon, especially to the right side of the drone ship, you can see that the timing of the landing is during a downward trough.  It still looks to my eye that the landing was pretty good, if not nominal.

I can't imagine that it is..

The whole landing sequence including throttle control is constantly reevaluated and adjusted..  by the time the legs touch the deck, it's too late to make any further changes IMO.

[FutureSpaceTourist]

https://twitter.com/djsnm/status/1222563879269462016

By compositing vertical slices of the Falcon 9 landing video you can see the booster was going to come to a stop above the deck and had to cut power, resulting in a short, unpowered fall onto the legs. Crush cores did their job.

[FutureSpaceTourist]

https://twitter.com/erdayastronaut/status/1222563279299653632

Veritical video might be a sin... so consider me a sinner 😈 Is
 there such thing as too zoomed in? 😂 here’s a preview of #Starlink-3 at 5000mm, 4K - 120 FPS. More to come 👌 beautiful launch today!!! @SpaceX @elonmusk

[kevinof]

Noticed that - it was only at the start, then it came back on track.

The booster seemed to undershoot the target trajectory noticeably in the Mission Control Audio stream.

[RotoSequence]

Noticed that - it was only at the start, then it came back on track.

It's a little harder to be entirely sure with the in-flight zoom out, but the trajectory managed to not visibly diverge by the end of the booster's burn, which is good. 

[PreferToLurk]

Noticed that - it was only at the start, then it came back on track.

It's a little harder to be entirely sure with the in-flight zoom out, but the trajectory managed to not visibly diverge by the end of the booster's burn, which is good. 

I wonder if the trajectory issue (if there really was one) could also partially explain the landing as well.  If the core had to use extra prop to fix the trajectory, the landing sequence could have been squeezed on propellant margin, requiring a bit more aggressive hover-slam, resulting in crush core usage.   

Maybe?

[abaddon]

https://spacenews.com/spacex-launches-fourth-batch-of-starlink-satellites-tweaks-satellite-design/

The launch — SpaceX’s fourth for Starlink not counting two demonstration satellites launched in 2018 — carried an upgraded set of satellites designed for better spectral efficiency and throughput.

Also from the article:

SpaceX’s Starlink satellites launched Jan. 29 each weigh approximately 260 kilograms, an increase of 33 kilograms from the 60 satellites launched in May 2019.

A bit of a weird comparison going back to the pre 1.0 satellites; is 260 the 'normal' mass of 1.0 satellites or was there an increase somewhere?

SpaceX specified that the newest Starlink satellites have four phased array antennas. Previous satellites were described as having “multiple” phased array antennas.

Not sure if this was previously divulged...

[abaddon]

Mission broadcast

[woods170]

I don't think the engine bells are replaceable. From what I remember this was debunked several times on this forum.

I've not read that but I can see it being more expensive to repair/replace than it is just to replace the Merlin engine in its entirety.

On Merlin 1D the engine bells are welded to the throat of the combustion chamber. Replacing an engine bell means replacing the entire engine.
Once an engine bell is damaged the engine is basically written off. Components that can be reused, are salvaged and reused.

[AndrewRG10]

What is your source for this?  There is a big difference between using some of the margin you built in, and using ALL of the margin you built in.

Crush material is used/not used.  Use it at all, you have to replace it.  Doesn't matter how much you use or not.  This one looked to be one of the hardest successful landings I've seen.  I'm curious if the engine bells hit the deck or not.  They don't appear to be touching after everything stabilized, but there's always some rebound on touchdown.

To your point, it IS a successful landing.  Crush zones, engine bells, etc. are all replaceable parts.  So, a good day, but a day to learn as well.

Have a good one,
Mike

If the engine bells hit the deck that means the booster will fall over. Because the only way the engines can get 2 metres lower is if the legs collapse/snap. I honestly think it is the camera angle, it really isn't sitting much lower than normal and that'll be clear in 4 days.

[CJ]

I went back and looked at the recent JSCAT16 landing vid, because it uses the same camera angle and location, plus the legs ended up in a very similar (but not quite, there's a few degrees of rotation) orientation.

I made today's landing semi transparent, and overlayed it, trying to match at the left leg. The landing leg angle on the left looks pretty much the same between the two.

In the second pic, I lined up on the white areas where the stowed legs reside.

To me, it looks like a small difference in the leg angle and vehicle height, if any. So, my guess is, if there was any crush core usage, it was minimal, and the engines are fine (due to not impacting the deck).

[FutureSpaceTourist]

I love it when the remotes come in

twitter.com/johnkrausphotos/status/1222626169222287363

And now, I present your obligatory closeup view of today’s Falcon 9 launch of 60 Starlink satellites. Flight after flight, these Merlin 1D engines never fail to put on a spectacular show.

https://twitter.com/johnkrausphotos/status/1222627765029081090

Here’s another view of the Falcon 9’s Merlin 1D engines powering the rocket and 60 Starlink satellites to space.

It’s amazing how quickly first stage reuse has become seemingly routine.

Check out my full gallery of photos from this morning’s mission → johnkrausphotos.com/Launch-Galleri…

Edit to add:

https://twitter.com/nova_road/status/1222623094550024194

Rockets are awesome. Love seeing the details of the 9 Merlin 1D engines as they power the #Falcon9 off the launch pad! #SpaceX #Starlink

[SkyRate]

Usually the engines shut-off as the legs touch, and weight is transferred from engines to legs smoothly.

Here the rocket reaches zero velocity too high, the engines shut down (as they have no choice but to do), and the stage accelerates downwards before touching down.

Whether it used up all of the crush core or not is not clear.  It looks pretty rough.

Is is a known fact that leg contact with the deck is the only cue/signal for engine shutdown? It seems like it would also make sense to cue engine shutdown if the position information says the vehicle is your "zero" elevation, probably the nominal deck height above sea level, & the vehicle is also at zero vertical velocity.

Unlikely to be just contact.

1. Shutting down at velocity=0 has to result in the gentlest landing in all cases.

2. Shutting an engine down is not instantaneous. There will be residual thrust, so the shutdown has to be commanded on a prediction of v=0.

3. The Falcon has a radar altimeter. (EM said he'd been worried the two side boosters of FH would be confused by each others' radar returns.) GPS altitude would have too low precision.

The startup is not instantaneous either, so engine needs to start based on velocity+altitude. Question is whether they have tried to be clever, and adapt the throttle to the possibly changing solution, or kept it simple and always do the same burn, with timing being the only variable.

[FutureSpaceTourist]

SpaceX launch photos by Ben Cooper

[FutureSpaceTourist]

https://twitter.com/julia_bergeron/status/1222645576577298445

I'm taking a wild guess here, but I think we'll be seeing the old school jack stands and chains securing B1051.3 to the deck of OCISLY when they come to port. The fleet is still at the landing zone after she came in just a little harder than usual. #SpaceXFleet

Edit to add: a differing view

https://twitter.com/spacexfleet/status/1222647515461320705

7 - 8 hours is a fairly standard amount of time from booster landing to droneship moving. Weather and darkness can cause complications.

I'd expect to see them leave in the next few hours unless Octagrabber cannot operate after the rough landing.

[ChrisC]

This mission's thread was never split between updates and discussion. Is that a new thing, or just an oversight?

[FutureSpaceTourist]

https://twitter.com/spacexfleet/status/1222679738524872705

Ms. Tree and Ms. Chief have finished their work and are now departing the recovery zone. OCISLY remains at the booster LZ.

[Draggendrop]

This mission's thread was never split between updates and discussion. Is that a new thing, or just an oversight?

I hope that this format continues. With Starlink launches every 2 to 3 weeks, the mission section can be a bit messy at times.

[intelati]

This mission's thread was never split between updates and discussion. Is that a new thing, or just an oversight?

I hope that this format continues. With Starlink launches every 2 to 3 weeks, the mission section can be a bit messy at times.

1. It's a new thing
2. I don't think I saw an announcement of the change. Just noticed one day that the name was 'Master thread'
3. I mostly like the concept.
4. I sort of wish there was a general Master Starlink update thread. (No discussion...) Hard to make the bounds of the thread though. Something like Starlink Launch and tracking??

[JAFO]

-It also looks like it slowed it's descent and was translating L-R closer to the center when the engines cut off? They should put a windsock on the far side of the barge for a visual wind indicator. (I know, they have  anemometers telling them the wind, but it would be a nice graphical representation for space geeks watching.)

-A good landing is one you can walk away from. A great landing is one where you can use the airplane (or booster) again. We'll give it an Fair-2.




BTW, put me down as liking the old way with separate thread for Updates and Discussion. I like being able to log in and quickly skim the Update thread to see what's going on vs wading through a bunch of comments.  When I have time later I'll check out the discussion thread in a more leisurely fashion.