SpaceX Falcon 9 : Iridium NEXT Flight 2 (June 25, 2017) : Discussion

[flyright]

Very nice. New fins took re-entry like a champ.

I wonder if the new fins contributed to the onboard camera not getting covered during reentry?  I always thought it was engine soot blowing back on the camera but maybe some of it was the ablative coating from the old grid fins.  Camera gave a nice clean view all the way down this time.

Edit: Ninjad by Herb on the soot.

Yep! No ablative material on the camera from the grid fins this time.

[John.bender]

Ok, thanks. Can watch these all day long.

[JamesH65]

Looks like S1 is a bit lower on the legs than usual, I wonder if they used up a  bit of crush core in the apparent  drop to the deck. Did look like engine shut of, then a bit less than a  second later the legs splayed out a bit, which seems it  indicate a drop. Understandable given the wave state.

[Pete]

Concur with those that observed it seemed to reach 0 velocity a few feet above the deck and drop the last couple feet after cut off.

Much better for it to come to a stop a few feet above the deck, than a few feet *under* the deck.

[jimbowman]

Some pics from the second stage over Antarctica would be cool

[Survtech]

I didn't think there was a boost back burn as they are landing on the drone.

I thought that too but the announcer said "The first stage boostback burn is underway" at T+3:01 but I didn't see any indication there were any Merlins firing. Weird!

[Rocket Science]

My impression is that there is no ablator material on the fins at all...

[HVM]

My impression is that there is no ablator material on the fins at all...

Elon Musk‏Verified account @elonmusk 1h1 hour ago

"Closeup of the titanium grid fins. Not painted, as they glow red hot during a fast reentry."

[ugordan]

I didn't think there was a boost back burn as they are landing on the drone.

I thought that too but the announcer said "The first stage boostback burn is underway" at T+3:01 but I didn't see any indication there were any Merlins firing.

Boostback plume is never prominently visible, the soot is more noticeable in forward-scattered light which was not the case today and also the sunlit interstage area brought the camera exposure down.

[kevinof]

Elon Musk ✔ @elonmusk
New titanium grid fins worked even better than expected. Should be capable of an indefinite number of flights with no service.
4:56 PM - 25 Jun 2017

[mvpel]

Here's a paper on numerical modeling of locally-swept fin geometry:

https://www.sto.nato.int/publications/STO%20Meeting%20Proceedings/RTO-MP-AVT-135/MP-AVT-135-35.pdf


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[satwatcher]

Some additional reasoning for having the boostback burn:

1. Reduce downrange location of the ASDS; quicker return to port, minimizing chances of bad weather.
2. Ability locate the ASDS away from the flight path, thereby greatly increasing possible locations for the ASDS, minimizing impact of weather on the launch.

[Lars-J]

Concur with those that observed it seemed to reach 0 velocity a few feet above the deck and drop the last couple feet after cut off.

Impressive sleuthing from a terrible angle. :p Don't quit your day jobs, people.

[tea monster]

Dragon waves hello and goodbye to Cthulhu as she zooms over Antarctica.

[Arb]

Is it just me, or was the boostback burn... invisible?
Also, those are some impressive bow waves being thrown up by JRTI. Wouldn't fancy being out there today!

There was a glimpse of its startup from the S2 camera just before it (S1) disappeared out of shot.

[Callezetter]

[georgegassaway]

How long before we get the first 3x flown booster?!

Probably after they have made two flights on a booster without one of them being a "Hot" reentry.  AFAIK, none of the boosters that have survived a hot re-entry with 3-engine landing, have been slated for a reflight. Perhaps as simple as just reflying the ones that are easier to refurbish more quickly , or perhaps such serious heat effects they are not viable to fly again.

Interestingly, both of the reflown boosters have had hot re-entries on their second flights.

I mean, if SpaceX had a near-term goal of flying some specific existing booster 5 times, they'd want to do the first 4 with gentler reentries, not do any hot ones.

 Of course with Block 5 on the way, they may not have as much incentive to refly many of the existing landed boosters if there are major issues with any potential revised Block 5 pad interface or whatever, and Block 5 is supposed to have better heat protection and be easier to refurbish.

[vanoord]

Concur with those that observed it seemed to reach 0 velocity a few feet above the deck and drop the last couple feet after cut off.

Impressive sleuthing from a terrible angle. :p Don't quit your day jobs, people.

Pause the YouTube video (<space>), then advance slowly with > (go back with >) and you'll see the engine glow stop about 0.5 seconds before the legs move on impact with the deck.

[vanoord]

I mean, if SpaceX had a near-term goal of flying some specific existing booster 5 times, they'd want to do the first 4 with gentler reentries, not do any hot ones.

 Of course with Block 5 on the way, they may not have as much incentive to refly many of the existing landed boosters if there are major issues with pad interface or whatever, and Block 5 is supposed to have better heat protection and be easier to refurbish.

My suspicion is we'll see them starting to drop re-flown boosters into the sea, i.e. the expendable missions will be pushed towards reused cores.

Arguably no point in recovering cores they're not going to have to re-use, but for the sake of just getting the engines back, it will probably prove financially preferable.

[rpapo]

Dragon waves hello and goodbye to Cthulhu as she zooms over Antarctica.

What, did a Dragon stow away on this flight?