SpaceX F9 : SES-10 with reuse of CRS-8 Booster SN/1021 : 2017-03-30 : DISCUSSION

[Robotbeat]

I see a geyser of LOx during part of the launch procedures, which I can only assume is this happening.

This is GOX/LOX vented from the strongback, not the vehicle and it was happening on v1.1 launches as well.

Why is the strongback squirting LOx?

[Jim]

I see a geyser of LOx during part of the launch procedures, which I can only assume is this happening.

This is GOX/LOX vented from the strongback, not the vehicle and it was happening on v1.1 launches as well.

Why is the strongback squirting LOx?

because the fill and drain valve on the vehicle has been closed and the trapped liquid in the lines needs to be vented/drained.

[Robotbeat]

Thanks.

[Herb Schaltegger]

That said, there is also a specific set of costs associated with booster recover and SpaceX could easily have decided it's not worth it for an older Block booster that will already have flown twice, especially with their experience recovering (and trying to recover) others from GTO missions last year, when recovery is so close to the margins on this Block.

SpaceX filed paperwork with the FCC less than a week ago saying they are sending out the ASDS for this flight.  I'm going to interpret that as meaning they intend to try recovering the SES-10 booster.

Hasn't Elon recently tweeted that this flight will be expendable?

[old_sellsword]

That said, there is also a specific set of costs associated with booster recover and SpaceX could easily have decided it's not worth it for an older Block booster that will already have flown twice, especially with their experience recovering (and trying to recover) others from GTO missions last year, when recovery is so close to the margins on this Block.

SpaceX filed paperwork with the FCC less than a week ago saying they are sending out the ASDS for this flight.  I'm going to interpret that as meaning they intend to try recovering the SES-10 booster.

Hasn't Elon recently tweeted that this flight will be expendable?

No, he was tweeting about EchoStar 23.

[Johnnyhinbos]

This is true, but I think this is only at the point where the strongback is retracted and fuel ops have concluded. However there is a second, earlier event - around T-11:40 - where there is obviously a LOX purge activity. Even those watching the livestream commented on that as it was unexpected. This, I believe, is an example of the venting and retopping and can be seen on the technical webcast at T-11:40 (7:57 into the video).



This I believe is an example of the purging of warmed LOX and replenishment of GSE cold LOX

[old_sellsword]

This is true, but I think this is only at the point where the strongback is retracted and fuel ops have concluded. However there is a second, earlier event - around T-11:40 - where there is obviously a LOX purge activity. Even those watching the livestream commented on that as it was unexpected. This, I believe, is an example of the venting and retopping and can be seen on the technical webcast at T-11:40 (7:57 into the video).



This I believe is an example of the purging of warmed LOX and replenishment of GSE cold LOX

LOX filling is not a continuous process under the new procedures they implemented with that flight, so Jim's explanation still holds.

[mn]

This is true, but I think this is only at the point where the strongback is retracted and fuel ops have concluded. However there is a second, earlier event - around T-11:40 - where there is obviously a LOX purge activity. Even those watching the livestream commented on that as it was unexpected. This, I believe, is an example of the venting and retopping and can be seen on the technical webcast at T-11:40 (7:57 into the video).



This I believe is an example of the purging of warmed LOX and replenishment of GSE cold LOX

Obviously some of the LOX will warm up to the GOX and be vented, but that would be just the top layer of LOX. The bulk of the supercooled LOX is still warming slightly AND IS NOT VENTING, no way are they pouring LOX out of the GOX vent. (IANARS but it seems like a really bad idea).

edit: fix LOX/GOX in last sentence.

[Herb Schaltegger]

That said, there is also a specific set of costs associated with booster recover and SpaceX could easily have decided it's not worth it for an older Block booster that will already have flown twice, especially with their experience recovering (and trying to recover) others from GTO missions last year, when recovery is so close to the margins on this Block.

SpaceX filed paperwork with the FCC less than a week ago saying they are sending out the ASDS for this flight.  I'm going to interpret that as meaning they intend to try recovering the SES-10 booster.

Hasn't Elon recently tweeted that this flight will be expendable?

No, he was tweeting about EchoStar 23.

Oops. I was conflating two things, then.

I guess objectively it's a good thing that there are so many upcoming flights that they're running together in my head.

[FutureSpaceTourist]

That said, there is also a specific set of costs associated with booster recover and SpaceX could easily have decided it's not worth it for an older Block booster that will already have flown twice [...]

I think the value in recovering it is not because they may want to fly it a third time, but rather to inspect and find out just how good or bad its condition is after a 2nd flight. To persuade more customers that re-use isn't risky will surely be easier with the evidence from a re-used booster? If the condition isn't great in any respect then SpaceX learn very valuable lesson and can talk to customers about the steps they are taking to address it.

[abaddon]

I don't think 200kg is enough of a net difference to account for the fact that this will be an expendable mission. Rather, I am increasingly convinced that the return to slower propellant and helium loading procedures has cut nominal performance enough to eat into the nominal ~15% performance margin typically reserved for landing.

Or maybe they decided getting a half-cooked stage back on a three-engine landing burn that endangers the ASDS to recover a soon-to-be-obsolete booster wasn't worth the hassle.

[EDIT] I see you said something similar to this later.

[CyndyC]

However there is a second, earlier event - around T-11:40 - where there is obviously a LOX purge activity. Even those watching the livestream commented on that as it was unexpected. This, I believe, is an example of the venting and retopping and can be seen on the technical webcast at T-11:40 (7:57 into the video).

This I believe is an example of the purging of warmed LOX and replenishment of GSE cold LOX

T-11:40 (7:57 video) is almost exactly one minute after John Insprucker says at T-12:39 (6:58 in the hosted video), "[liquid oxygen] loading is currently paused as we are loading the last of the helium into the storage vessels." So maybe a minute later oxygen loading was resumed, but that still could mean the purging was from the lines to clear them of buildup before resuming.

[CyndyC]

Recall that the SES-9 launch that tore up OCISLY so badly had been sent to a higher than previously planned orbit, to make up for some of the delay during the CRS-7 investigation by saving the payload some time getting to its final target on its own at a slower pace.

That cost to fuel margin must have been greater than the cost of the revised loading procedures, because SpaceX can't maintain their new goals for launch & landing frequency with OCISLY out of commission for several weeks like it was before.

[CraigLieb]

Recall that the SES-9 launch that tore up OCISLY so badly had been sent to a higher than previously planned orbit, to make up for some of the delay during the CRS-7 investigation by saving the payload some time getting to its final target on its own at a slower pace.

That cost to fuel margin must have been greater than the cost of the revised loading procedures, because SpaceX can't maintain their new goals for launch & landing frequency with OCISLY out of commission for several weeks like it was before.

Didn't they perform an upgrade on the deck plating on the ASDS? I know they had to do repairs after the 'robust landing', but recently I thought they brought in more deck plating also during the hiatus in flight. Not sure of my "facts" here, so please correct me if I am wrong.

[ClayJar]

Didn't they perform an upgrade on the deck plating on the ASDS? I know they had to do repairs after the 'robust landing', but recently I thought they brought in more deck plating also during the hiatus in flight. Not sure of my "facts" here, so please correct me if I am wrong.

It certainly looked like they were doing something to the center, as shown in the photo on this post in the ASDS thread:

Taken Saturday, Dec 3, 2016, about 4:30p

[cscott]

That cost to fuel margin must have been greater than the cost of the revised loading procedures, because SpaceX can't maintain their new goals for launch & landing frequency with OCISLY out of commission for several weeks like it was before.

Pretty sure that with their current backlog and the upcoming arrival of block 5 they'd do "water landings" or skip recovery altogether if something were to happen to OCISLY.

[Johnnyhinbos]

I would think with the performance enhancement envisioned with Block 5 that some manifested launches slated for ASDS under < Block 5 could manage a RTLS with Block 5.

[hrissan]

This is true, but I think this is only at the point where the strongback is retracted and fuel ops have concluded. However there is a second, earlier event - around T-11:40 - where there is obviously a LOX purge activity. Even those watching the livestream commented on that as it was unexpected. This, I believe, is an example of the venting and retopping and can be seen on the technical webcast at T-11:40 (7:57 into the video).



This I believe is an example of the purging of warmed LOX and replenishment of GSE cold LOX

That would work if warm LOX ended up at the top of the tank. But as the heat influx is from tank walls, the warmer LOX would start its long travel up, that motion would definitely include intermixing with inner layers of colder LOX. So IMHO the right way to summarize process is "all volume of LOX in the tank is gradually warming up".

And the only way to substantially cool it back is replacing almost all LOX in a tank.

I'm afraid other "creative" ideas like creating vacuum in the tank (and keeping it at reduced boiling temperature) or installing large and heavy heat exchanger are out of question

[IanThePineapple]

I would think with the performance enhancement envisioned with Block 5 that some manifested launches slated for ASDS under < Block 5 could manage a RTLS with Block 5.

With the enhancement I think most LEO missions' landings would be RTLS, with a few being ASDS.

[Orbiter]

SES-10 first stage (AKA CRS-8 core) firing on the test stand in McGregor from SpaceX's Twitter feed.