SpaceX Falcon 9 : CRS-11 : June 3, 2017 : DISCUSSION

[sevenperforce]

Watching the onboard video it appears they restart the 1st stage during the re orientation flip not after it. is this just me seeing things? I remember watching the NROL launch being impressed at how fast they flipped and restarted but this seemed faster and more aggressive.

It's not just you seeing things. It might just be that due to the trajectory requirement to do RTLS, starting the burn while reorienting is actually helping by combining maneuvers and thus gives them more margin.

Absolutely. I do this all the time in KSP; as long as you've got a good engine gimbal, you can start your burn any time you're generally pointed in the right direction and let the engine kick you into the right place.

[Machdiamond]

Wow, these guys were practically under the landing rocket:

https://www.instagram.com/p/BU5JNxkg6rS/

(NSF language, but cool video)

To give this one justice, you need to crank up volume to the max.

[John Alan]

Wow, these guys were practically under the landing rocket:

https://www.instagram.com/p/BU5JNxkg6rS/

(NSF language, but cool video)

To give this one justice, you need to crank up volume to the max.

Agreed... I pulled it up on the big screen with sub woofers... volume cranked... OMG... 

[tvg98]

Now this is incredible... you can even see dragon firing its thursters too...

[ChrisC]

(almost posted this in the updates thread, whoops)

On Sunday night, with Cygnus moving away from ISS and Dragon moving towards it, we will have the rare opportunity to spot three objects in the sky, chasing each other.

I expect that Dragon will be approaching from behind, and by Sunday night (US ET) should be very close.  Does anyone know which direction Cygnus will be departing in, and how fast the SS John Glenn will move away from ISS?

If there another NSF thread where this is being discussed, please point me to it

[JimO]

Can anybody locate the actual time-of-ignition [and duration] of the stage-2 deorbit burn?

[ppb]

Watching the onboard video it appears they restart the 1st stage during the re orientation flip not after it. is this just me seeing things? I remember watching the NROL launch being impressed at how fast they flipped and restarted but this seemed faster and more aggressive.

It's not just you seeing things. It might just be that due to the trajectory requirement to do RTLS, starting the burn while reorienting is actually helping by combining maneuvers and thus gives them more margin.

Absolutely. I do this all the time in KSP; as long as you've got a good engine gimbal, you can start your burn any time you're generally pointed in the right direction and let the engine kick you into the right place.

Correct. Much more attitude control authority with the main engine gimbals compared to the N2 reaction thrusters.

[georgegassaway]

Any idea what that was? It looks like a bird, but 59 km is a bit too high for them.

Pretty sure that was ice. Noticed on a previous flight in the last 2 months, 2nd stage re-ignition, ice that had formed above the engine (after cut-off), shook loose and drifted off. Same process would likely occur on the first stage booster too, and the early phase of re-entry caused some ice to start to melt off or break free.

Relative velocity of the piece  probably nowhere near as fast as it may seem (or as big as it may have been close to the camera), and grid fins would have shattered it.

 Saw this same thing with two pieces flying past the booster camera a month or so back. At the time someone thought it was some sort of incredible coincidence that something all by itself was in the path of the booster as it descended, rather than considering it could have been from the tail of the booster. IIRC those two pieces were much lighter in color. So if this was indeed ice again, the darker color may be related to soot from the RP-1 exhaust.

As for the "Weather Balloon Identification Chart", here's one regarding airline pilots identifying "Drones".



Sadly, too much truth to it. A year ago, huge world news about a British Airways airliner that hit a drone while landing at Heathrow. The pilots KNEW they'd hit one, because of a "thump" they heard.  Two weeks, later, the Air Ministry announced the airliner had hit a plastic bag that winds had picked up. But that update was not carried by most of the news outlets that reported the "airliner  / drone collision".

[Jdeshetler]

Now this is incredible... you can even see dragon firing its thrusters too...

This is really a good hand held shot so it was stabilized and posted on YouTube, first one is at normal speed and the 2nd is speed up by a factor of 4x.

[nacnud]

Now this is incredible... you can even see dragon firing its thrusters too...

Thanks for that, that is exactly what I saw too. It was almost perfect seeing conditions here, just after sunset and extremely clear and still sky.

[darkenfast]

Hard to tell, but from the pic and video I think that the mystery piece was a bit of an insulation blanket that surrounds the engines at the base of the stage.

[gospacex]

Watching the onboard video it appears they restart the 1st stage during the re orientation flip not after it. is this just me seeing things? I remember watching the NROL launch being impressed at how fast they flipped and restarted but this seemed faster and more aggressive.

It's not just you seeing things. It might just be that due to the trajectory requirement to do RTLS, starting the burn while reorienting is actually helping by combining maneuvers and thus gives them more margin.

At boostback, every second before S1 is not yet thrusting, it gains about one more kilometer of distance away from LZ. Currently, flips take more than 10 seconds - that's 10 more kms to fly back. Therefore they look into ways to minimize this pause: start the flip as early as possible, flip faster, ignite Merlins even before flip is over - that sort of thing.

[ugordan]

The part I found neat about this launch is the shock interaction between the MVac plume and the ACS thrusters on the 1st stage. The technical webcast had both stage cameras on at that point and they were well synched up, at 22:38 into the webcast:


Also, yeah, as far as I could tell all the fast flips and boostbacks so far had the center engine light up before the stage completely turned around.

[geza]

Judging from the  updates from Planet imaging on May 31st , the LZ-1 pad might be black in the center when they land (although they might have painted it white since)

From https://www.planet.com/explorer

It has remained black according to the landing picture. This is probably the radio reflexive paint Elon tweeted about:
https://twitter.com/elonmusk/status/871228411494014976

[Dante80]

It has remained black according to the landing picture. This is probably the radio reflexive paint Elon tweeted about:
https://twitter.com/elonmusk/status/871228411494014976

I was under the impression that SpaceX used a simpler approach to landing, by just running the GPS LZ-1 coords through the navigation unit. In the case of DPL campaigns, the same happened with the stage AND the barge (barge ordered to keep its station, S1 calculated a 0-0 touchdown on the given coords before launch).

Now they are using active radar?

[macpacheco]

It has remained black according to the landing picture. This is probably the radio reflexive paint Elon tweeted about:
https://twitter.com/elonmusk/status/871228411494014976

I was under the impression that SpaceX used a simpler approach to landing, by just running the GPS LZ-1 coords through the navigation unit. In the case of DPL campaigns, the same happened with the stage AND the barge (barge ordered to keep its station, S1 calculated a 0-0 touchdown on the given coords before launch).

Now they are using active radar?

Nothing changed vs what has been speculated all along. GPS for navigation in general, radar altimeter used for low altitude readings, where its more accurate and lower latency to obtain readings (and it measures altitude to ASDS including waves instead of to sea level + normal ASDS elevation).

Radar for civil navigation is always active. Passive radar is (pretty much) a military only thing when vehicles use enemy's radar emissions to find/target them.

Radar altimeter was already used. Just LZ improvements to make its job more precise.

[Lars-J]

It did seem like the most gentle touchdown yet, so perhaps the radar reflective paint helped with that.

[Paul_G]

I was under the impression that SpaceX used a simpler approach to landing, by just running the GPS LZ-1 coords through the navigation unit. In the case of DPL campaigns, the same happened with the stage AND the barge (barge ordered to keep its station, S1 calculated a 0-0 touchdown on the given coords before launch).

Now they are using active radar?

GPS would give you accurate X and Y coordinates of LZ-1 but could the reflective paint and radar give a more accurate Z? Didn't we hear of some radar tests bring conducted at Hawthorne and The Vandenberg pad recently - perhaps this radar reflective paint is one of the results of those tests.

[su27k]

Any idea what that was? It looks like a bird, but 59 km is a bit too high for them.

We had almost exactly the same thing happen a few landings ago.  At about the same altitude and speed.

Yes, that's why I'm surprised. Do you remember which landing it was?

http://forum.nasaspaceflight.com/index.php?topic=40815.msg1644552#msg1644552

I think the general consensus was that it's a piece of TPS

[Norm38]

The NROL-76 reentry burn was called out as 25 seconds long. This one was significantly shorter. Are they continuing to optimize fuel usage, or is that due to different trajectories?