What "weed need" is a space mission!

[kladner]

Originally Posted by chalsall

I am a huge fan of Dan Simmons, but when I read "Flashback" I realized what a racist red neck he is. Still love most of his work ("Drood" was a huge waste of time though!).

It doesn't look promising.
https://www.washingtonpost.com/enter...6lI_story.html
Sorry for the extended digression.

[only_human]

Originally Posted by Dubslow

It will be less than 55 minutes before they start streaming, because 55 minutes is the launch time.

Yeah, noted. The stream says that it's going live in 43 minutes now but it should start sooner.Streaming now

[only_human]

Originally Posted by only_human

Yeah, noted. The stream says that it's going live in 43 minutes now but it should start sooner.Streaming now

T - 11

[Mark Rose]

Bullseye!

[Dubslow]

Woo! No live video as yet but images of the landed rocket + operator callouts.

[only_human]

Single engine landing burn as opposed to three engines on previous GTO mission landings.

According to hosted comments it allows more time for maneuvers, is gentler and more tolerant of atmospheric winds -- I wasn't listening closely at the time so I might have gotten the gist slightly wrong.

PS
Webcast over; ended with a small shoutout to Kenny Baker from R2D2, RIP.

[Mark Rose]

Originally Posted by only_human

Single engine landing burn as opposed to three engines on previous GTO mission landings.

According to hosted comments it allows more time for maneuvers, is gentler and more tolerant of atmospheric winds -- I wasn't listening closely at the time so I might have gotten the gist slightly wrong.

Yes. A single engine burn does use more fuel, however, which is most likely why it wasn't done previously.

[Dubslow]

As always, a billion trade offs. Substantially easier from an operations and controls standpoint, at the expense of more fuel/delta V being wasted to gravity losses.

Given that JCSAT-16 is nearly identical to JCSAT-14 (rumored to be some 10s of kg less mass) [recall JCSAT-14 produced the "max damage" core being tested to near-destruction], it's kinda surprising that they have the extra margin. Besides switching back to the more costly single engine burn, the press release also listed stage 1 and stage 2 burn times a few seconds shorter each. It's possible they've introduced another minor uprating in Merlin thrust, which might explain the extra margin they apparently had.

[chalsall]

Originally Posted by only_human

Single engine landing burn as opposed to three engines on previous GTO mission landings.

I believe this was a single engine *rentry* burn rather than the previous three engine rentry burns. All landing burns have been single engine AFAIU.

Very happy to be corrected.

[only_human]

Originally Posted by chalsall

I believe this was a single engine *rentry* burn rather than the previous three engine rentry burns. All landing burns have been single engine AFAIU.

Very happy to be corrected.

Maybe only JCS14 used a three engine landing burn:

Elon Musk – Verified account ‏@elonmusk

Yeah, this was a three engine landing burn, so triple deceleration of last flight. That's important to minimize gravity losses.
10:51 PM - 5 May 2016

https://en.wikipedia.org/wiki/Falcon...om_GTO_mission

Pursuing their experiments to test the limits of the flight envelope, SpaceX opted for a shorter landing burn with three engines instead of the single-engine burns seen in earlier attempts; this approach consumes less fuel by leaving the stage in free fall as long as possible and decelerating more sharply, thereby minimizing the amount of energy expended to counter gravity.[75] Elon Musk indicated this first stage may not be flown again and will instead be used as a life leader for ground tests to confirm future first stage rockets are good.[76]

PS:
Reddit: Mathematical analysis of a three-engine hoverslam

[Dubslow]

Originally Posted by chalsall

I believe this was a single engine *rentry* burn rather than the previous three engine rentry burns. All landing burns have been single engine AFAIU.

Very happy to be corrected.

There's been multiple three engine landing burns for purposes of efficient use of extremely limited fuel.

Conversely, I can't think of a reason to do a single engine reentry burn (excepting the earlier instances where only one engine had reignition equipment, which hasn't been the case for several launches). For landing, less engines offers greater control, but for reentry the engines contribute little to none of the targeting control, they are merely brakes. (The grid fins are the primary control authority above subsonic speeds.)