SpaceX Falcon 9 : Iridium NEXT Flight 3 : Oct 9, 2017: DISCUSSION

[guckyfan]

With the barge landing, why was there a boost back burn?  I thought boost back was only for RTLS.

If you've got the fuel to spare, and don't really want to send the barge a few hundred miles further out...

Seems they are not worried about another burn.

[envy887]

For some reason the liftoff looked "slow" to me.  (I am not saying anything was off nominal - just conveying my impression at the moment of liftoff).  I imagine it had to do with nighttime viewing conditions.  But I really did have several heartbeats where I was thinking "Oh CRUD, it's gonna do a big RUD before liftoff and blow the pad to bits and pieces!"  I was very  happy to see it move up and away.

Iridium launches are the heaviest payload F9 has launched, IIRC, so the TWR might be visibly lower than for a GTO mission.

A loaded F9 weighs almost 600 tonnes, while the difference between a GTO sat and the Iridium stack is only about 4 tonnes. Doubt the difference is at all noticeable (roughly 0.08 m/s^2 difference in acceleration at liftoff).

[kevin-rf]

With the barge landing, why was there a boost back burn?  I thought boost back was only for RTLS.

If you've got the fuel to spare, and don't really want to send the barge a few hundred miles further out...

Also, the more forward speed you can kill, the lower the thermal loads (and damage) on the recovered stage.

[ugordan]

FWIW, liftoff didn't seem any slower than usual for me.

[dawei]

FWIW, liftoff didn't seem any slower than usual for me.

I'm sure your are right.  Just my very adrenaline filled impression at the moment of liftoff.

[dawei]

Anybody know the timing of the deorbit burn?  Any guesses on burn duration from all you amateur rocket scientists out there?  Professional rocket scientists are also welcome to weigh in

[Kaputnik]

Was concerned about the long apparent leak, but it was cleared up, "solid oxygen", not a concern.

Any more info on this? What source is there for O2 other than a leak?

[Pete]

The 12:37 bus to the Iridium dorms has completed its route.
Bus has returned to depot for routine maintenance.
No events, no incidents.
.
Next bus leaves in 2 days time.
Just another routine day in a routine job.

[Pete]

Was concerned about the long apparent leak, but it was cleared up, "solid oxygen", not a concern.

Any more info on this? What source is there for O2 other than a leak?

I would not be surprised at all if this is exactly as intended.
You want to avoid the formation of either gaseous bubbles or solid ice in the O2 lines, the easiest way (by far) to achieve this is to allow a minute trickle of O2 to flow through, thus maintaining the lines at the temperature of the main tank, rather than worrying about exact thermal environment, shade vs. sunlight, etc...

[Robotbeat]

LOx is gonna boil off, and venting also can help settle propellant. Totally nominal.

[ugordan]

Block 4 stages, presumably.  Hope we learn more about post-landing situation (mention of post-landing fire upthread).

It was never explicitly stated that the fire was on the droneship. My initial guess, given that LC was addressed/called it, made me think it was actually a fire at SLC-4E.

[nacnud]

With the post landing fire was the camera working in IR? It was rather dark out in the Pacific.

[Johnnyhinbos]

With the post landing fire was the camera working in IR? It was rather dark out in the Pacific.

The ASDS' are festooned with all kinds of lights.

[mme]

A surprisingly nice view, 100 miles from the site.


(1:20 for the sighting)

Many congrats to everyone involved for the successful conclusion of yet another launch campaign.

Check out the interacting S1/S2 exhaust plumes at about 2:50.

[mvpel]

For some reason the liftoff looked "slow" to me.  (I am not saying anything was off nominal - just conveying my impression at the moment of liftoff).  I imagine it had to do with nighttime viewing conditions.  But I really did have several heartbeats where I was thinking "Oh CRUD, it's gonna do a big RUD before liftoff and blow the pad to bits and pieces!"  I was very  happy to see it move up and away.

I wish somebody had gotten a picture of me when I was watching CRS-8 lift off, the first and so far only launch I've seen in person. I must have looked like Kevin from Home Alone as I struggled to grasp the impossible sight of this immense machine the size of a building slowly claw its way skyward on a blazing shard of sunlight. I had exactly the same thought you did, too.

[haywoodfloyd]

Was it me or did the YouTube feed seem "jerky". Seems there was lot of buffering going on.

[techdude06]

Was it me or did the YouTube feed seem "jerky". Seems there was lot of buffering going on.

YouTube stream was just fine for me.

Sent from my SM-G935V using Tapatalk

[mme]

Was concerned about the long apparent leak, but it was cleared up, "solid oxygen", not a concern.

They pre-chill by venting LOX through the system.  It's not a leak, it's intentional.

Engine Chilldown

[woods170]

Block 4 stages, presumably.  Hope we learn more about post-landing situation (mention of post-landing fire upthread).

 - Ed Kyle

There was no such as a post-landing fire. What was seen in the post-landing footage was the usual burning-off of residual propellant from the center engine. It stopped less than 15 seconds after touch-down. No fire after that. This burning-off of residual propellants happens on all landings. It is completely nominal. The only reason it was seen this clearly is because of the night-time conditions. Had this landing been witnessed in bright daylight the burning-off would have hardly been visible.

[ChrisC]

Here's another video I stumbled across zoomed in on stage separation and boostback:

Going to quote this closeup video into here for further discussion.  Absolutely astonishing!