Updates SpaceX Falcon 9 F5 CRS SpX-2 through CRS SpX-12 Updates

[Thunder Chicken]

What exactly is the stage using for landing guidance? A beacon on the pad, visual targeting, etc? It sure looks like it was chasing some oscillation and couldn't quite catch it.

 

[Ripley]

I don't think this was posted yet, a longer version of the "landing"...

After watching this video, I think that the 1st stage really missed a firm landing (barging?) just for a tiny little bit.
Sure it does look to be coming down a bit too fast for my taste, but I guess SpaceX knows its business better than I do.

Anyway (not knowing the forces in play), I also had this silly thought:
can the thrust/exhaust from 1st stage's engine directly on the deck have the side-effect of "pushing it down" and making the barge sink just a little bit, exactly in the very moment when 1st stage would need to find firm "ground" under its feet?

 

[fraxudemspas]

Sure it does look to be coming down a bit too fast for my taste, but I guess SpaceX knows its business better than I do.

Even on a single engine, the near-empty first stage can't throttle down below 1g. It pretty much has to fall all the way down and brake at the last moment.

 

[Thunder Chicken]

Even on a single engine, the near-empty first stage can't throttle down below 1g. It pretty much has to fall all the way down and brake at the last moment.

I think they call it the "hover slam". The empty stage needs to keep sufficient downward momentum to overcome the thrust. The intent is that the sudden braking deceleration results in zero vertical velocity at zero altitude.

 

[Kyle]

I think they call it the "hover slam". The empty stage needs to keep sufficient downward momentum to overcome the thrust. The intent is that the sudden braking deceleration results in zero vertical velocity at zero altitude.

They called it a "Falcon Punch" :thumbup:

 

[Thunder Chicken]

Anyway (not knowing the forces in play), I also had this silly thought:
can the thrust/exhaust from 1st stage's engine directly on the deck have the side-effect of "pushing it down" and making the barge sink just a little bit, exactly in the very moment when 1st stage would need to find firm "ground" under its feet?

For a 300 ft by 100 ft barge, a 100,000 lbf (50 ton) thrust force would require less than an inch of additional displacement in sea water. The thrust could possibly get the barge to rock a bit, but in less than the amount of time required to get that big barge to move the rocket would already be down. It's a big barge - American football field sized. Swells are probably a bigger issue.

 

[C3PO]

After watching this video, I think that the 1st stage really missed a firm landing (barging?) just for a tiny little bit.
Sure it does look to be coming down a bit too fast for my taste, but I guess SpaceX knows its business better than I do.

IMHO it looks like they got the vertical speed spot on. It was the lateral movement that tipped it over. It looks like the oscillation is getting worse. That usually means that the control loop is too slow or the settings are too 'powerful'. Maybe fuel-slosh played a part here, but I bet SpaceX has a ton of data to go through now. That is after all the whole point of the exercise.

---------- Post added at 02:32 AM ---------- Previous post was at 02:21 AM ----------

Wow, using game footage to report the news. I can't tell if this is epic for KSP or a complete journalism fail.

The reporter saying that the cost of engines is "exorberant" leads me to the second.

Install MechJeb, problem solved! :lol:

How about "Falcon 9 is currently en route to rendezvous with the ISS" or "It landed but it had a little bit extra vertical thrust". :huh:

 

[Andy44]

Not to mention how much it would cost to ship it back FROM Africa.

Just launch it again, this time land in East Asia.

Then launch it again, and land in California.

Then launch it again, and land in Florida.

Easy.:tiphat:

 

[Michkov]

I may be making this up but isn't the final plan to launch from Texas and land the first stage at KSC?

 

[IronRain]

An enhanced and close up video:

 

[Urwumpe]

What exactly is the stage using for landing guidance? A beacon on the pad, visual targeting, etc? It sure looks like it was chasing some oscillation and couldn't quite catch it.

I think they just use DGPS + Inertial. Not sure if some assisting system had been installed on the barge as well.

 

[BrianJ]

The whole final targeting phase before powered descent has to be more precise. And/or the powered descent has to start earlier to allow compensating problems without exceeding control stability limits.

Sure it does look to be coming down a bit too fast for my taste, but I guess SpaceX knows its business better than I do.

That was my thought when watching the video - the stage is coming down really fast! I know they're trying to minimise fuel consumption, but with even a little bit more fuel for the final burn you get a slower, much more manageable final descent (in Orbiter anyway!).

Better luck next time, SpaceX!

 

[Thunder Chicken]

I may be making this up but isn't the final plan to launch from Texas and land the first stage at KSC?

The 1st stage downrange distance isn't anywhere near that far, couple hundred miles at most. Even so, doing this would only be possible for certain launch inclinations.

 

[fraxudemspas]

That was my thought when watching the video - the stage is coming down really fast! I know they're trying to minimise fuel consumption, but with even a little bit more fuel for the final burn you get a slower, much more manageable final descent (in Orbiter anyway!).

Better luck next time, SpaceX!

Unless they can modify the engine to throttle down more, that's not an option - with a near-empty stage, its minimal acceleration is above 1g.

 

[Donamy]

It's all in the timing with altitude and engine cut-off.

 

[Urwumpe]

It's all in the timing with altitude and engine cut-off.

And engine start profile.

Even if the Merlin engine is very simple, it still has, in the context of the landing, a very long delay until it reaches mainstage and can be throttled faster.

The large number of variables there makes it very complicated even without the environment messing things up.

I really wonder, if it would be smarter to add some simple pressure fed vernier thrusters to the stage, so it can be stabilized before and during engine start as final kick.

 

[MaverickSawyer]

Either that, or add some smaller engines just for landing. More complicated? Sure, but also less of an issue with TWR at minimum throttle.

 

[N_Molson]

They get better at fireworks.

A gust of wind at the wrong moment is enough to spoil everything. And sea isn't a laboratory. So I'd say that a lot of water will flow under the barges until "they" get any return on investment on this...

 

[Hlynkacg]

Barge eye view...

https://vid.me/e/i6o5

edit: pos HTML interface wont let me post video, see link.

 

[MaverickSawyer]

Barge eye view...

https://vid.me/e/i6o5

edit: pos HTML interface wont let me post video, see link.

Aw, they had it SO close.... Next time, guys.