SpaceX Falcon 9 FT - ORBCOMM-2 - Dec. 21, 2015 (Return To Flight) DISCUSSION

[meekGee]

Classic.  The "it ain't proven yet" line starts at the top.

If it were his own company, he might have worried about the possibility that it might actually work instead of clinging to the hope that it won't.

A Arianespace factory worker has less to worry about in near term from the F9 recovery than SpaceX factory worker. Every recovered booster is one less that SpaceX needs to produce and SpaceX are not known for carrying surplus workers.

That's 100% correct.

Do you want to advance spaceflight and go to Mars, or do you want a jobs program?

[philw1776]

OK! So....I've been told there is amazing footage - that will hopefully be released - of the Falcon 9 OG2 S1 external camera view of the stage sep, boost back, reentry burn and landing!

Let's hope SpaceX release it (no I've not seen it myself).

Could someone please report this guy to the mods here for teasing us time & again?

[abaddon]

I had the reentry burn at 20 seconds based on the various spectator YouTube videos now out there.  The landing burn came in at perhaps 32-34 seconds from the same sources.

Thanks; using 20 seconds for the reentry burn and 33 seconds for the landing burn gives us:

1314/1487=88.37% (86.73%)
90/1487=6.05% (5.94%)
60/1487=4.03% (5.54%)
23/1487=1.55% (1.78%)

So, not too different.

One of the reasons I wanted to do this was to see what eliminating the boostback burn does.  Based on these calculations it is less than I would have imagined and that makes me think I am doing something wrong.  SpaceX characterizes the barge landing as -15% of performance and RTLS as -30% of performance.  If you allocated the 90 merlin-seconds of burn used for boost-back to the first stage you'd end up with another 30s of burn time though, which could be pretty substantial I suppose.

[Lars-J]

Classic.  The "it ain't proven yet" line starts at the top.

If it were his own company, he might have worried about the possibility that it might actually work instead of clinging to the hope that it won't.

A Arianespace factory worker has less to worry about in near term from the F9 recovery than SpaceX factory worker. Every recovered booster is one less that SpaceX needs to produce and SpaceX are not known for carrying surplus workers.

I wouldn't worry about SpaceX factory workers. They still need to churn out upper stages that are built on the same assembly line. If they can lower costs and fly more often (or lower costs by flying more often) they still need to build a lot of hardware.

[Semmel]

I had the reentry burn at 20 seconds based on the various spectator YouTube videos now out there.  The landing burn came in at perhaps 32-34 seconds from the same sources.

Thanks; using 20 seconds for the reentry burn and 33 seconds for the landing burn gives us:

1314/1487=88.37% (86.73%)
90/1487=6.05% (5.94%)
60/1487=4.03% (5.54%)
23/1487=1.55% (1.78%)

So, not too different.

One of the reasons I wanted to do this was to see what eliminating the boostback burn does.  Based on these calculations it is less than I would have imagined and that makes me think I am doing something wrong.  SpaceX characterizes the barge landing as -15% of performance and RTLS as -30% of performance.  If you allocated the 90 merlin-seconds of burn used for boost-back to the first stage you'd end up with another 30s of burn time though, which could be pretty substantial I suppose.

I am not sure, but I thought the re-entry burn was with just one engine instead of three?

[Norm Hartnett]

Step 1 - Check

[ugordan]

I am not sure, but I thought the re-entry burn was with just one engine instead of three?

Boostback and reentry burns are on 3 engines with (at least the reentry burn) a staggered shutdown, first the outer 2 and then center one. Landing burn is on a single engine.

[Johnnyhinbos]

Last nights launch is being talked about on NPR right now. Great tidbits...

[abaddon]

If you allocated the 90 merlin-seconds of burn used for boost-back to the first stage you'd end up with another 30s of burn time though, which could be pretty substantial I suppose.

Thinking about this some more, that's 30s of extra burn time as the stack approaches its lowest mass, which means the dV will be at its highest.  So, maybe that 30s of extra burn that is reserved for the boostback could account for a -15% performance decrease to orbit after all.

I know there are some very smart folks who model this stuff lurking around...

[Chris Bergin]

OK! So....I've been told there is amazing footage - that will hopefully be released - of the Falcon 9 OG2 S1 external camera view of the stage sep, boost back, reentry burn and landing!

Let's hope SpaceX release it (no I've not seen it myself).

Could someone please report this guy to the mods here for teasing us time & again?

I've just warned him about it. I looked a bit silly wagging my finger at the mirror, I must admit.

[abaddon]

Last nights launch is being talked about on NPR right now. Great tidbits...

I heard it on NPR last night, but the NPR local station reporter identified the head of SpaceX as Jeff Bezos.  Oy vei!

[Johnnyhinbos]

Last nights launch is being talked about on NPR right now. Great tidbits...

I heard it on NPR last night, but the NPR local station reporter identified the head of SpaceX as Jeff Bezos.  Oy vei!

Oh that's not good! They talked about Bezos' Twitter jab on this. And played a bit of Elon's con call. I'll see if I can find a link...

[cwr]

I had the reentry burn at 20 seconds based on the various spectator YouTube videos now out there.  The landing burn came in at perhaps 32-34 seconds from the same sources.

Thanks; using 20 seconds for the reentry burn and 33 seconds for the landing burn gives us:

1314/1487=88.37% (86.73%)
90/1487=6.05% (5.94%)
60/1487=4.03% (5.54%)
23/1487=1.55% (1.78%)

So, not too different.

One of the reasons I wanted to do this was to see what eliminating the boostback burn does.  Based on these calculations it is less than I would have imagined and that makes me think I am doing something wrong.  SpaceX characterizes the barge landing as -15% of performance and RTLS as -30% of performance.  If you allocated the 90 merlin-seconds of burn used for boost-back to the first stage you'd end up with another 30s of burn time though, which could be pretty substantial I suppose.

Maybe I don't understand what you're saying, but wouldn't 90 merlin-seconds of burn
spread across the 9 merlin engines in the 1st stage mean that the 1st stage would get
10 seconds of extra burn time by giving up the boost-back burn?
Since the 1st stage burns for approximately 2 minutes, 10 seconds is a 10% increase
in burn time [very approximately].

Carl

[oiorionsbelt]

Classic.  The "it ain't proven yet" line starts at the top.

If it were his own company, he might have worried about the possibility that it might actually work instead of clinging to the hope that it won't.

A Arianespace factory worker has less to worry about in near term from the F9 recovery than SpaceX factory worker. Every recovered booster is one less that SpaceX needs to produce and SpaceX are not known for carrying surplus workers.

That's 100% correct.

Do you want to advance spaceflight and go to Mars, or do you want a jobs program?

IMO SpaceX's work force will continue to increase not decrease. This is after all just the beginning.

[king1999]

Classic.  The "it ain't proven yet" line starts at the top.

If it were his own company, he might have worried about the possibility that it might actually work instead of clinging to the hope that it won't.

A Arianespace factory worker has less to worry about in near term from the F9 recovery than SpaceX factory worker. Every recovered booster is one less that SpaceX needs to produce and SpaceX are not known for carrying surplus workers.

Wait, don't they need more workers for the MCT and BFR? Also the 4000+ satellites too?

[LouScheffer]

If you allocated the 90 merlin-seconds of burn used for boost-back to the first stage you'd end up with another 30s of burn time though, which could be pretty substantial I suppose.

Thinking about this some more, that's 30s of extra burn time as the stack approaches its lowest mass, which means the dV will be at its highest.  So, maybe that 30s of extra burn that is reserved for the boostback could account for a -15% performance decrease to orbit after all.

Well, here's at least a crude model from the SES-9 thread:

We can form a pretty good guess of what barge recovery costs in terms of delta-V.  The rocket used to hold 396 t of fuel.  Now say it's 420t, a 6% improvement.  The empty stage + legs is guessed at about 30t, and the fuel needed for a (non-return) landing is also about 30 t (this is full thrust on 3 engines for 30 seconds for the retro burn, then 30 seconds on one engine for the landing burn).  Using Musk's figure of 125 t for the upper stage,  the theoretical no-recovery delta-V of the first stage is 311*9.8*ln((420+30+125)/(30+125)) = 3995 m/s.  With recovery, the final mass is 30 t more, so the delta V is 3456 m/s.   So making the reasonable assumption that the lower atmosphere ISP, drag, and gravity losses are similar, we find that barge recovery (compared to no recovery) costs about 540 m/s.   

[abaddon]

Maybe I don't understand what you're saying, but wouldn't 90 merlin-seconds of burn
spread across the 9 merlin engines in the 1st stage mean that the 1st stage would get
10 seconds of extra burn time by giving up the boost-back burn

Doh!  You're right; 10s not 30s.  Was being hasty/careless.  Thanks for the correction.

[wannamoonbase]

OK! So....I've been told there is amazing footage - that will hopefully be released - of the Falcon 9 OG2 S1 external camera view of the stage sep, boost back, reentry burn and landing!

Let's hope SpaceX release it (no I've not seen it myself).

Could someone please report this guy to the mods here for teasing us time & again?

I've just warned him about it. I looked a bit silly wagging my finger at the mirror, I must admit.

That mirror has seen a lot of silly things because of this site.

[macpacheco]

Don't forget that the landing burn happen at lowest possible thrust.

[DecoLV]

Last nights launch is being talked about on NPR right now. Great tidbits...

I heard it on NPR last night, but the NPR local station reporter identified the head of SpaceX as Jeff Bezos.  Oy vei!

Actually, I've seen a good bit of 2nd Gen media today. Its funny...they're all just waking up to the story.

Did anybody see Mass on CNN? I was in a cafe with the Tv sound off when I saw him.