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#1300
by
tobi453
on 21 Dec, 2015 18:03
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Fairing sep at T+12 minutes??? Must either be a big typo or they really need all the ballast they can get... 
Maybe SpaceX is doing a new experiment with the fairing, that we do not yet know. And there is more than enough performance on this flight.
Maybe they could have launched yesterday with an earlier fairing separation.
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#1301
by
InfraNut2
on 21 Dec, 2015 18:04
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A third theory is that the FAA is unwilling to interfere with holiday airplane traffic any more than absolutely necessary.
To those thinking about technological reasons for the short launch window:
Remember that the original windows was longer. That means previously known (i.e. a large majority of) tech reasons are unlikely.
That leaves (a) non-tech reasons like the above and (b) newly-discovered or newly-relevant reasons as the primary suspects.
In some ways a pity for the large part of the people here that are tech fans like me and love discussing that stuff, unless we find possible new tech reasons...
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#1302
by
ejb749
on 21 Dec, 2015 18:08
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Has Elon given any of his famous odds for a successful landing? I believe the last attempt was given 50/50.
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#1303
by
edkyle99
on 21 Dec, 2015 18:19
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Fairing sep at T+12 minutes??? Must either be a big typo or they really need all the ballast they can get...
Maybe SpaceX is doing a new experiment with the fairing, that we do not yet know. And there is more than enough performance on this flight.
Maybe they could have launched yesterday with an earlier fairing separation.
Sep at 12 minutes would put the fairing into orbit.
- Ed Kyle
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#1304
by
ugordan
on 21 Dec, 2015 18:23
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That fairing sep timing has to be a typo and mean something like T+3or4 min 12 seconds instead.
I mean, payloads have pretty strict center-of-mass considerations for stage controllability reasons, a fairing would throw that off significantly. I don't think the two halves are completely symmetrical mass-distribution wise.
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#1305
by
ZachS09
on 21 Dec, 2015 18:38
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I hope SpaceX added enough hydraulic fluid to the grid fins and fixed the stuck throttle valve. I also hope that the first stage doesn't have too much lateral velocity upon touchdown.
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#1306
by
LouScheffer
on 21 Dec, 2015 18:47
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How do you suppose the accomplish the super-cooling of the LOX? Maybe use LN2? Perhaps they needed to replenish their LN2 supply?
When NASA did this experiment, they used 2 stages of LN2 cooling. They first used LN2 at room pressure to lower the LOX to 77K, using a heat exchanger. Then they used a pump to pull a vacuum of about 1/5 atm above the nitrogen, which cools it to 66K, which then cools the LOX via another heat exchanger.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050203875.pdfNASA's setup could cool about 13 kg/sec to 66K. SpaceX must be slower if they are still cooling LOX two days after the static file. They might be using a different method, have limited LN2, smaller heat exchangers, or other limitation.
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#1307
by
geza
on 21 Dec, 2015 18:50
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It is interesting to see that boost-back and landing at T+00:10:00 is an integral part of the mission time-line in the press kit. Am I right, that this is the first case? At the earlier occasions the secondary nature of the landing experiment was stressed, instead. It may indicate a stronger confidence in a successful landing this time. Fairing sep comes after SECO, i.e., in orbit, is surprising, but cannot be just a typo, because the events are listed in order.
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#1308
by
Rocket Science
on 21 Dec, 2015 18:54
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Having a look for tonight's WX.
Winds 12-13 kts. gusting to 17-18 kts. Pretty sporty for a landing if they try... 
That's probably a little high given the evening launch time... I'd say more 9-14kts.
I'll take your estimate as it's your area of expertise. Mine was for at the Cape shoreline near the skid strip.
I like your numbers better!
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#1309
by
Chris Bergin
on 21 Dec, 2015 19:01
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#1310
by
Almurray1958
on 21 Dec, 2015 19:09
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Fairing jettison time has been corrected:
00:03 Fairing deployment
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#1311
by
NovaSilisko
on 21 Dec, 2015 19:14
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Fairing jettison time has been corrected:
00:03 Fairing deployment
Where are you seeing that? It's still listed as 12, for me.See JamesH's post below V
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#1312
by
Kaputnik
on 21 Dec, 2015 19:15
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It is interesting to see that boost-back and landing at T+00:10:00 is an integral part of the mission time-line in the press kit. Am I right, that this is the first case? At the earlier occasions the secondary nature of the landing experiment was stressed, instead. It may indicate a stronger confidence in a successful landing this time. Fairing sep comes after SECO, i.e., in orbit, is surprising, but cannot be just a typo, because the events are listed in order.
I'm seeing it read Fairing Deployment at 03:00 which sounds much more likely than 12:00
Has the press kit been edited?
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#1313
by
JamesH
on 21 Dec, 2015 19:20
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#1314
by
Comga
on 21 Dec, 2015 20:02
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New PDF posted
http://www.spacex.com/sites/spacex/files/spacex_orbcomm_press_kit_final2.pdf
Interesting timeline
There are only four seconds between 1st stage MECO and separation.
Perhaps the pusher allows them to ignore the engines burping a la F1 Flight 3.
There isn't much resolution, but 1st stage MECO is at 2:40 and the boost-back burn stats at minute 4.
It seems it will take over a minute to flip over the 1st stage
There is a reentry burn.
Landing and SECO occur close together. Lots of activity to watch.
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#1315
by
Lars-J
on 21 Dec, 2015 20:14
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#1316
by
rocx
on 21 Dec, 2015 20:16
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Landing and SECO occur close together. Lots of activity to watch.
Maybe SpaceX will provide a split-screen so we can watch both at the same time.
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#1317
by
photonic
on 21 Dec, 2015 20:30
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SpaceX tweeted a close-up of the stretched interstage, stretched upper stage, and fairing: https://twitter.com/SpaceX/status/679039057180024832
(note the grid fins now lack a fairing, as we were told by a source earlier)
Is it the lighting, or does the inter-stage really look so dirty? Almost looks like someone painted it over hastily. Just curious, what matters is obviously that it launches and lands in one piece ...
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#1318
by
Johnnyhinbos
on 21 Dec, 2015 21:09
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SpaceX tweeted a close-up of the stretched interstage, stretched upper stage, and fairing: https://twitter.com/SpaceX/status/679039057180024832
(note the grid fins now lack a fairing, as we were told by a source earlier)
Is it the lighting, or does the inter-stage really look so dirty? Almost looks like someone painted it over hastily. Just curious, what matters is obviously that it launches and lands in one piece ...
That's been driving me nuts too. It's more than just dirt. It fully looks patched. There has to be a better reason than cryo cooling. Look at the attached pic (credit Jeff Seibert). That area above the SpaceX logo looks like they peeled off duct tape and left a clean spot behind...
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#1319
by
averagespacejoe
on 21 Dec, 2015 21:15
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I was looking at the press kit, and thought maybe they should put an asterisk next to the words official SpaceX patch *only official if successful, but if this is a failure this patch will be hidden from the world.
Not even sure why they bother posting a picture of it...
