SpaceX FH: STP-2 : LC-39A : June 25, 2019 - DISCUSSION

[JimO]

Yes, prior to any ignition. That GOX/LOX is dumped overboard during chilldown but it looks visually different than this and it's continuous venting for a while.

Were we seeing the GOX/LOX dumps for the trans-Mars burn observed from SW US?

FH [falcon heavy] escape burn to Mars Feb 06, 2018 observed from SW USA 
http://satobs.org/seesat_ref/misc/180206_fh_s2_burn3_d2.pdf

[Kabloona]

That's if they get "A Shortfall Of Gravitas" ready for that mission.

"A Shortfall Of Gravitas" seems to be like Schrodinger's cat, existing in some people's minds while not existing in other's. Shortly after Elon announced that ASoG was in the works, a reliable source involved in SpaceX marine operations talked to some of the SpaceX recovery guys, and they swore there was no other ASDS in the works, and they didn't know why Elon was saying publicly that there was.

Some of us on the ASDS thread also did our own sleuthing trying to locate any other shipyards that might be working on an ASoG, since the source said McDonough Marine, owner of the Marmacs, had no knowledge of an ASoG project either, and we came up completely empty. Nobody knew anything about it.

One possibility is that shortly after Elon announced ASoG, SpaceX changed plans and decided not to proceed. JRtI is seriously under-utilized at VAFB, and perhaps they decided to consider moving JRtI back to the Cape. Or they just decided that one ASDS per coast was enough. There's also the Super Heavy/Starship factor, and SpaceX may have decided they want to transition away from Falcon Heavy as soon as possible, meaning no more need for dual-ASDS missions to catch the FH side boosters.

The other possiblity is that ASoG construction has been proceeding somewhere extremely well hidden during the 16 months since Elon announced it, with no photos, no leaks, no tweets, no nothing.

My money is on option #1, that plans for ASoG were quietly dropped.

[cscott]

If Vandenberg is going to be shut down in favor of using the excess performance available w/ FH to run dogleg routes to polar orbits from the Cape, then it certainly would make sense to relocate JRtI.

[Orbiter]

A few shots from my end.

[edkyle99]

Four starts over a 3.5 hour mission for a LOX/kerosene engine.  A long record of successful performance leading up to this flight, including several long-coast to restart tests.  Rugged, simple engine cycle yet still throttleable and efficient. 

Is Merlin 1D Vacuum the best rocket engine yet flown?  It must be compared with the likes of RL10, AJ10, Bell 8096, J-2, the LM engines, etc.

 - Ed Kyle

[scr00chy]

One possibility is that shortly after Elon announced ASoG, SpaceX changed plans and decided not to proceed. JRtI is seriously under-utilized at VAFB, and perhaps they decided to consider moving JRtI back to the Cape. Or they just decided that one ASDS per coast was enough.

Elon mentioned ASOG twice. First time it was during the FH Demo press conference in February 2018 and then again on Twitter 6 months later where he even said ASOG would be ready in summer 2019. It could have been cancelled since then, of course, but it doesn't seem to me like it was a spur of the moment kind of thing.

https://twitter.com/elonmusk/status/1023073822080098304

As for SpaceX moving JRTI to Florida, I had the same idea recently and posted my thoughts on Reddit. But it's hard argue one way or the other because it depends a lot on ASOG being available (if and when).

[Kabloona]

One possibility is that shortly after Elon announced ASoG, SpaceX changed plans and decided not to proceed. JRtI is seriously under-utilized at VAFB, and perhaps they decided to consider moving JRtI back to the Cape. Or they just decided that one ASDS per coast was enough.

Elon mentioned ASOG twice. First time it was during the FH Demo press conference in February 2018 and then again on Twitter 6 months later where he even said ASOG would be ready in summer 2019. It could have been cancelled since then, of course, but it doesn't seem to me like it was a spur of the moment kind of thing.

https://twitter.com/elonmusk/status/1023073822080098304

As for SpaceX moving JRTI to Florida, I had the same idea recently and posted my thoughts on Reddit. But it's hard argue one way or the other because it depends a lot on ASOG being available (if and when).

Re Elon's later tweet in July 2018, I forgot to mention that, several months after this *second* public mention of ASoG, his own director of recovery ops said he didn't know anything about a third ASDS. He may have been obfuscating, but why bother? It would be easier, and maybe less embarrassing to say, oh yeah, we're building a third one just like Elon said. Instead, he claimed total ignorance.

Weird tea leaves.

[Alexphysics]

Ok so to clarify. The original FCC position was just an error, that was not the initially planned landing point, in fact it was quite surprising considering the many burns the second stage needed. The very original plan, obviously, was to expend everything because it was all v1.0. When landings started to be a thing the plan changed to sides ASDS and center core expended. Back then the mission included a 5th burn to deorbit the stage but SpaceX clearly wanted to spare the center core (now they might regret that hehe). The Block 5 performance is huge so they could do boosters RTLS and they asked USAF to drop that last burn to recover the center core. This is info that not only I have heard before but also quite a few others have told me similar things. Maybe it's not 100% the total picture of how things have gone but it's what I understand to a high degree of confidence. The plan of double droneship landing was still on until late last year, now think about why Elon said ASoG would be ready by this year's summer 

Re:AFSPC-52 orbit. As far as I know the target orbit is GEO, not GTO. 6 tons to GEO means expendable center core. They might be able to RTLS the boosters but considering the second stage then has to be thrown to a graveyard orbit and perform another burn and being the DoD... I'm skeptical. As I always say: let's see and enjoy 

[codav]

Re:AFSPC-52 orbit. As far as I know the target orbit is GEO, not GTO. 6 tons to GEO means expendable center core.

The only public information I could find everywhere about the target insertion orbit - which SpaceX might choose to supersede - is that GTO. It was specified in the Instructions to Offerors (page 18 section 10.1.1.1) published by the USAF. If there is any updated/contrary information available, I'm quite interested in it. L2 link via PM if it's been mentioned there

[Alexphysics]

Re:AFSPC-52 orbit. As far as I know the target orbit is GEO, not GTO. 6 tons to GEO means expendable center core.

The only public information I could find everywhere about the target insertion orbit - which SpaceX might choose to supersede - is that GTO. It was specified in the Instructions to Offerors (page 18 section 10.1.1.1) published by the USAF. If there is any updated/contrary information available, I'm quite interested in it. L2 link via PM if it's been mentioned there

I think I know from where my error came. I read the wrong document back then and now I'm realizing it is not even for the same mission. I'm stupid 

[WannaWalnetto]

What happened to the spent second stage?  There is no mention of it’s final disposition in the press kit:  https://www.spacex.com/sites/spacex/files/stp-2_press_kit.pdf

[Orbiter]

Re:AFSPC-52 orbit. As far as I know the target orbit is GEO, not GTO. 6 tons to GEO means expendable center core. They might be able to RTLS the boosters but considering the second stage then has to be thrown to a graveyard orbit and perform another burn and being the DoD... I'm skeptical. As I always say: let's see and enjoy 

They can do 6k to GEO and RTLS the side boosters based on the performance calculations I've seen. 8k and beyond is when RTLS becomes impossible.

[Kabloona]

What happened to the spent second stage?  There is no mention of it’s final disposition in the press kit:  https://www.spacex.com/sites/spacex/files/stp-2_press_kit.pdf

Per the SpaceX mission animation, the stage did a "propulsive passivation," presumably  to move away from the DSX orbit, leaving it in MEO (?)

https://forum.nasaspaceflight.com/index.php?topic=48325.msg1955315#msg1955315

[Alexphysics]

What happened to the spent second stage?  There is no mention of it’s final disposition in the press kit:  https://www.spacex.com/sites/spacex/files/stp-2_press_kit.pdf

Propulsive depassivation and it has been left out in a graveyard orbit.

[envy887]

Hard to tell, but did all 4 legs deploy properly? I could see it aborting if a leg didn't come down and lock.

We're going to have to see. Could be a throttle issue, could be legs, could be a sensor issue. Most likely cause is the hot entry, but I don't think we are going to hear anything more until Elon tweets

If it wasn't a deliberate evasive burn due to too much vertical velocity (it didn't really look to me that it was going to lawn-dart OCISLY, though), I'm wondering if it was a center engine gimbal failure.

Agreed. Looks to me like a TVC issue resulting in the tip-over. Since it was lined up correctly in the first place, maybe it throttled up on purpose to get away from OCISLY.

And Elon confirmed it was a TVC failure.

https://twitter.com/elonmusk/status/1143690145255841797

[mn]

Hard to tell, but did all 4 legs deploy properly? I could see it aborting if a leg didn't come down and lock.

We're going to have to see. Could be a throttle issue, could be legs, could be a sensor issue. Most likely cause is the hot entry, but I don't think we are going to hear anything more until Elon tweets

If it wasn't a deliberate evasive burn due to too much vertical velocity (it didn't really look to me that it was going to lawn-dart OCISLY, though), I'm wondering if it was a center engine gimbal failure.

Agreed. Looks to me like a TVC issue resulting in the tip-over. Since it was lined up correctly in the first place, maybe it throttled up on purpose to get away from OCISLY.

And Elon confirmed it was a TVC failure.

https://twitter.com/elonmusk/status/1143690145255841797

If the TVC failed, how did the computer intentionally divert?

[ClayJar]

If the TVC failed, how did the computer intentionally divert?

The center engine TVC failed, but it was not a single-engine landing.

[VDD1991]

Finally, SpaceX is picking up the pace with scheduled Falcon Heavy launches, considering that the STP-2 launch was originally scheduled for October 2016. With the last scheduled launch of single-stick Delta IV coming next month, who knows when the next Falcon Heavy launch will be, given that Delta IV Heavy will share the American heavy-lift spotlight with Falcon Heavy.

[mn]

If the TVC failed, how did the computer intentionally divert?

The center engine TVC failed, but it was not a single-engine landing.

I'll rephrase my question: if you are lined up with the asds why divert? Just continue regulating thrust. If not lined up then you can't call that intentionally diverted.

[Norm38]

I would love to see a dramatic style CGI video of the center core divert burn. It got flat horizontal. Must have looked damn cool from certain angles.