Author Topic: SpaceX Falcon 9 : Iridium NEXT Flight 2 (June 25, 2017) : Discussion  (Read 162077 times)

Offline JAFO

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Based on some oversimplified assumptions for some calculations, it looks like that stage may have dropped 2-4 meters before hitting the deck. Does that sound right?

Any landing you can walk away from...

It will be interesting to see the deckside camera footage of the landing when it becomes available.  Both today and Friday may have been "interesting" landings, and both should make for some good discussions once the video is out.

What the ASDS needs is a Paddles.
"Falcon 9, ball, 2.5." (in a R2D2 chirp)
"Roger Falcon, slightly left of centerline, I see you correcting, the deck is slightly heaving, don't chase the ball."
Anyone can do the job when things are going right. In this business we play for keeps.
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Offline Johnnyhinbos

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A ship at sea will rise and fall with the average swell of its cross-section. In heavy seas, swells can easily reach several meters and have periods of seconds to minutes. The rocket starts its landing burn and throttles to achieve 0 m/s at what it hopes will be the deck of the ASDS. If level off is achieved and the deck has heaved 2 - 4 meters below, the results must be engine shutdown and a hope for the best. Impact in this case seemed to provide a short bounce, but no particularly noticeable ill effects.
I think the booster has an radar altimeter and should be able to measure rate of approach. It wouldn't even be that hard a piece of software to figure vertical barge movements into the decent if they were regular. Problem is of course, barge movement from swells isn't always a smooth oscillation and can be erratic, and different parts of the deck move at different rates depending on how the barge is pivoting. They could ballast the barge before landing to reduce movement, but you'd have to balance that against the risk of waves washing over the deck. And discharging ballast at sea has it's own complications and would add time to the operation.
 They're going to have a less than optimal landing eventually, and I can't help but think they really need a spare ASDS to keep the schedule up. There are too may reasons one might not be available for a launch, and that would mean underwater boosters until it was back online.
Nomadd, the ASDS is already ballasted. These converted Marmac 304 barges have flood-able tanks to allow it to be "in ballast".  http://truesouthmarine.com/uncategorized/the-spacex-autonomous-spaceport-drone-ship/
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Offline Nomadd

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Nomadd, the ASDS is already ballasted. These converted Marmac 304 barges have flood-able tanks to allow it to be "in ballast".  http://truesouthmarine.com/uncategorized/the-spacex-autonomous-spaceport-drone-ship/
Having tanks doesn't mean it has ballast, and I was talking about degree. You can ballast those barges until the deck is a foot off the water if you want, but you wouldn't want to tow it home that way.
« Last Edit: 06/27/2017 03:20 am by Nomadd »
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Offline Lars-J

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I'm expecting grid fins to be reused more often than booster cores, just due to the elimination of refurbishment. 

Someone made a comment on SpaceflightNow that was funny but partly true. He said SpaceX will only need one set of titanium grid fins. Let's say 3, one for each launch site.

Someone forgot about FH it seems.  :)

Offline rpapo

I'm expecting grid fins to be reused more often than booster cores, just due to the elimination of refurbishment. 

Someone made a comment on SpaceflightNow that was funny but partly true. He said SpaceX will only need one set of titanium grid fins. Let's say 3, one for each launch site.

Someone forgot about FH it seems.  :)
At least until they are flying every other day or so, and you don't have the time to grab the fins off the previous booster and mount them on the next.
Following the space program since before Apollo 8.

Offline CyndyC

I'm expecting grid fins to be reused more often than booster cores, just due to the elimination of refurbishment. 

Someone made a comment on SpaceflightNow that was funny but partly true. He said SpaceX will only need one set of titanium grid fins. Let's say 3, one for each launch site.

Someone forgot about FH it seems.  :)

At least until they are flying every other day or so, and you don't have the time to grab the fins off the previous booster and mount them on the next.

I realized later I forgot about FH, but not before I realized I forgot they will soon have 2 launch pads running at the Cape. I added Vandenberg and Boca Chica to one at the Cape.

If you weren't exaggerating to say they'll someday be flying every other day, that won't even be enough time for the drone ship to return with the fins. Nice thought though. 
"Either lead, follow, or get out of the way." -- quote of debatable origin tweeted by Ted Turner and previously seen on his desk

Offline docmordrid

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With 2 pads shooting and the potential for several launches a week, ISTM they're going to need either more ASDS's or a much faster platform equipped ship/catamaran/?..? - or two.
« Last Edit: 06/28/2017 07:48 am by docmordrid »
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Offline launchwatcher

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With 2 pads shooting and the potential for several launches a week, ISTM they're going to need either more ASDS's or a much faster platform equipped ship/catamaran/?..? - or two.
There has been sporadic discussion of other options on the Autonomous Spaceport Drone Ship Discussion Threads.   Might be worth a thread of its own.

Offline Lars-J

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With 2 pads shooting and the potential for several launches a week, ISTM they're going to need either more ASDS's or a much faster platform equipped ship/catamaran/?..? - or two.

Or RTLS. Block 5 may allow RTLS for Iridium NEXT launches. (speculation)

Offline abaddon

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Or RTLS. Block 5 may allow RTLS for Iridium NEXT launches. (speculation)
Iridium launches don't seem that much heavier than Dragon launches, although they are going to higher orbit (~600km vs ~200km) and require a PLF where Dragon does not.  I would guess that RTLS will be possible, given that RTLS of CRS missions is within Block 3 capabilities.  But it might be a close shave.

Offline baldusi

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Or RTLS. Block 5 may allow RTLS for Iridium NEXT launches. (speculation)
Iridium launches don't seem that much heavier than Dragon launches, although they are going to higher orbit (~600km vs ~200km) and require a PLF where Dragon does not.  I would guess that RTLS will be possible, given that RTLS of CRS missions is within Block 3 capabilities.  But it might be a close shave.
According to NASA NLS site, the Falcon 9 from Vandemberg loses 26% of performance if it has to RTLS vs ASDS. To go to ISS orbit from the Cape, they quote an even higher loss of 28%. They don't quote the performance for expendable.

Offline gongora

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Or RTLS. Block 5 may allow RTLS for Iridium NEXT launches. (speculation)
Iridium launches don't seem that much heavier than Dragon launches, although they are going to higher orbit (~600km vs ~200km) and require a PLF where Dragon does not.  I would guess that RTLS will be possible, given that RTLS of CRS missions is within Block 3 capabilities.  But it might be a close shave.

The only figure I've ever seen (and I can't remember the exact number now, it was a tweet from Stephen Clark) I think was around 8600kg for a fully loaded Dragon?  I don't know exactly what that included.  If it included the trunk then Iridium is quite a bit heavier, especially before the fairing is dropped.

Offline abaddon

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The only figure I've ever seen (and I can't remember the exact number now, it was a tweet from Stephen Clark) I think was around 8600kg for a fully loaded Dragon?  I don't know exactly what that included.  If it included the trunk then Iridium is quite a bit heavier, especially before the fairing is dropped.
Iridium Next launches are 860kg x10 plus 1000kg for the adapter, or 9600kg.  Of course, you do have to add the PLF for some of that, but I wouldn't really call it "quite a bit heavier".  We have no idea what kind of margin there is for RTLS of a Dragon-launching core, either.

All in all, I think it definitely seems possible that Iridium flights might fall within the RTLS envelope when using Block 5, but certainly not a guarantee.
« Last Edit: 06/28/2017 08:51 pm by abaddon »

Offline Formica

https://m.imgur.com/a/is1bZ

Album of JRTI coming into port. 1036 seems to be riding very low - only a few feet between the engine bells and the deck.

Offline rpapo

Next to no discoloration above the grid fins this time.
Following the space program since before Apollo 8.

Offline Jcc

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No Roomba either.

Offline Herb Schaltegger

No Roomba either.

Wrong coast.  Wrong ASDS. :)
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Offline Lars-J

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It's neat that the hand-written "s/n 003" is still visible on the left grid fin, as well as the tiny core number "36" just below the central grid fin. (Image from the update thread)
« Last Edit: 06/30/2017 06:19 am by Lars-J »

Offline Robotbeat

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With 2 pads shooting and the potential for several launches a week, ISTM they're going to need either more ASDS's or a much faster platform equipped ship/catamaran/?..? - or two.

Or RTLS. Block 5 may allow RTLS for Iridium NEXT launches. (speculation)
Theyre not going to sustain over a hundred launches per year before ITS or similar.
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Offline JamesH65

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With 2 pads shooting and the potential for several launches a week, ISTM they're going to need either more ASDS's or a much faster platform equipped ship/catamaran/?..? - or two.

Or RTLS. Block 5 may allow RTLS for Iridium NEXT launches. (speculation)
Theyre not going to sustain over a hundred launches per year before ITS or similar.

Why not? 100 launches approx two per week. They will have three launch pads (plus Boca Chica to make 4). That's just over a week per pad per launch. They are not far of that now. They'll probably need another drone ship though.

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