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#920
by
clongton
on 09 Jan, 2018 11:55
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Every time Soyuz launches it ignites 20 main engines and 12 verniers - 32 engines all ignited for liftoff...
Soyuz ground lights five engines with, in total, 32 nozzles. I suppose you could call it 32 ignition events? Still only five engines though.
You guys are technically correct. I should have indicated 32 separate ignition events.
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#921
by
dnavas
on 09 Jan, 2018 15:49
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So is the pad taking a well-deserved day off today? It was my assumption that Monday would be on (I assumed a pad review post-launch in AM), and then a deferred weekend, and then a Thursday attempt, so I guess I'm happy to see Wednesday for my own selfish reasons, but I hope the folks over there are getting a day off?
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#922
by
cscott
on 09 Jan, 2018 16:32
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The FH was raised to vertical late last night, so it seems at least some employees are working late nights, not taking a break.
More likely today is for further fit checks (perhaps off whatever might have been found awry during the last fit check), propellant conditioning, dry runs, etc. Three times the cores = three times the propellant to deliver and then cool, three times the pre-fire checks to run, etc.
IIRC the LOX dome is still filled by individual tanker deliveries?
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#923
by
eeergo
on 09 Jan, 2018 16:37
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Every time Soyuz launches it ignites 20 main engines and 12 verniers - 32 engines all ignited for liftoff...
Soyuz ground lights five engines with, in total, 32 nozzles. I suppose you could call it 32 ignition events? Still only five engines though.
You guys are technically correct. I should have indicated 32 separate ignition events.
Still quite a different beast IMO: RD-107's main nozzles are about half of the Merlin's diameter (~0.7 vs ~1.1 m) and they're either ignited externally or with a cross-fed autoignition system using the rocket's propellants, as opposed to the separate TEA-TEB system in Merlin-1D. Correction of combustion instabilities was a major driver in upgrading the original RD-107/108 to their variants, and indeed motivated the very engines' development from the failed RD-105/106 (see
http://www.lpre.de/energomash/ED/index.htm#RD-105).
I agree though that the "complexity of lighting 27 engines" is probably overblown compared to many other potential sources of trouble for the FH. Indeed Soyuz (for example, but also STS and others) uses several throttle settings during its ignition sequence (four: start-up, preliminary, intermediate and main), with staggered starts between the side blocks and the block A, at least in part in order to limit overpressures.
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#924
by
FutureMartian97
on 09 Jan, 2018 16:56
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According to the NSF article FH will undergo a WDR and will only proceed with the static fire if everything looks good. How will they be able to perform the WDR and static fire in the same window?
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#925
by
old_sellsword
on 09 Jan, 2018 17:02
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According to the NSF article FH will undergo a WDR and will only proceed with the static fire if everything looks good. How will they be able to perform the WDR and static fire in the same window?
By lighting the engines at the end of the WDR?
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#926
by
mheney
on 09 Jan, 2018 17:04
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According to the NSF article FH will undergo a WDR and will only proceed with the static fire if everything looks good. How will they be able to perform the WDR and static fire in the same window?
A WDR (Wet Dress Rehearsal) means going through the launch sequence just up to the point of igniting the engines. A static fire means you
do all the WDR steps, then fire the engines up - keeping the hold-down clamps in place - then shutting the engines down after a few seconds.
So the "end" of a WDR leaves you on the cusp of a static fire - mere seconds away. You don't need to drain the tanks from the WDR and then restart the process from scratch; you just verify that everything is as expected, and light the candle.
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#927
by
gongora
on 10 Jan, 2018 01:09
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SpaceX filed for a
modification of the FCC permit for the launch vehicle communications on this mission:
Please explain the purpose of operation: Launch vehicle communications for mission launching from Kennedy Space Center. We are increasing bandwidth on two frequencies from original application approved under: 1259-EX-ST-2017.
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#928
by
IanThePineapple
on 10 Jan, 2018 01:13
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I wonder how long the static fire will be, does anyone know? I'd guess 7 seconds rather than 3.5 to get lots more data.
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#929
by
AC in NC
on 10 Jan, 2018 02:16
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I wonder how long the static fire will be, does anyone know? I'd guess 7 seconds rather than 3.5 to get lots more data.
Any chance they'd do a significantly longer one, perhaps even full length? Or a reason why they couldn't?
Given all the talk about 3 cores being more complicated than expected, I'd be surprised if there wasn't some value to a full length static fire. Although perhaps the hold down eliminates a lot of the interplay that complicated the 3 core system and thus doesn't provide more insight than a short test.
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#930
by
georgegassaway
on 10 Jan, 2018 02:35
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Pad not built to be able to keep cool long enough for a "full burn". The available amount of water in the big storage tank is not enough to support a really long burn being just one of the problems (Long burn static firings are done at McGregor, where the stands are designed to take it for minutes, not seconds). There are likely to be other practical issues for pad components that don't get sprayed with water in any case.
IIRC, the rare shuttle FRF's were about 20 seconds long, but that does not mean that 39A's rebuild for launching FH bears any relevance to that. I'd be surprised if they did a burn as long as 10 seconds, and perhaps no more than 5 seconds. IIRC they did do one "longer than normal" Static Test of an F9 on LC-40 a couple of years back, but it was around 4 to 5 seconds (or planned for 5 but cut to 3 to 3.5..... something like that).
For what they are looking to find out for FH, they only need a few seconds - the staggered ignition being the newest thing to test for, plus getting readings on vibrations and acoustics, etc. that will be different for a 27 engine new booster than a regular F9, and how all the pad components handle it.
Question - Suggestions for the most likely source for seeing any live video of the FH Static Firing?
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#931
by
docmordrid
on 10 Jan, 2018 02:51
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#932
by
wannamoonbase
on 10 Jan, 2018 04:03
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The SpaceX video on the cover article is amazing. It shows the FH in all its glory and does the best job showing it’s scale.
I’m getting more than a little excited.
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#933
by
avollhar
on 10 Jan, 2018 08:35
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SpaceX filed for a modification of the FCC permit for the launch vehicle communications on this mission:
The interesting bit are the transmitter frequencies of stage 2: 2232.5 and 2272.5 MHz. Well within the capabilities of amateur radio tracking stations worldwide. Now we would just need some coarse trajectory to point the antennas to..
We can hope for a launch into the ecliptic plane (direction) and from the launch telemetry on the webcast (speed) should it all go well, we might be able to set up a trajectory model with crude orbital elements.
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#934
by
SimonFD
on 10 Jan, 2018 10:03
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SpaceX filed for a modification of the FCC permit for the launch vehicle communications on this mission:
Please explain the purpose of operation: Launch vehicle communications for mission launching from Kennedy Space Center. We are increasing bandwidth on two frequencies from original application approved under: 1259-EX-ST-2017.
Can this tell us anything about what they might do with increased bandwidth? Does it mean the stage can be communicated with for longer as it starts on it's way to Mars orbit? If so, why?
Intriguing
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#935
by
tvg98
on 10 Jan, 2018 11:14
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#936
by
A12
on 10 Jan, 2018 11:50
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SpaceX filed for a modification of the FCC permit for the launch vehicle communications on this mission:
Please explain the purpose of operation: Launch vehicle communications for mission launching from Kennedy Space Center. We are increasing bandwidth on two frequencies from original application approved under: 1259-EX-ST-2017.
Can this tell us anything about what they might do with increased bandwidth? Does it mean the stage can be communicated with for longer as it starts on it's way to Mars orbit? If so, why?
Intriguing
Perhaps just because they need three video/telemetry channels, one for each booster.
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#937
by
loki
on 10 Jan, 2018 12:07
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We should be a little bit more patient, waiting for static fire. For a new rocket, the first “Wet Dress Rehearsal” is always finished with emptying fuel tanks, among other procedures, as exercise for an emergency. It is enough for a working day. If everything is perfect (always are needed small corrections), only then we will see static fire next day.
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#938
by
Oersted
on 10 Jan, 2018 12:33
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The 'mission' is basically to clear a series of milestones and thus I don't think that you can really talk about 'mission success' beyond 'getting the upper stage into LEO parking orbit'. Everything else is very much 'learning experience' and, optimistically 'Hey! It worked!'
Agreed, and that's why I phrased the options in the poll the way I did.
If you haven't voted yet, let's hear from you!
What can we expect when the Falcon Heavy launches? (Poll)https://forum.nasaspaceflight.com/index.php?topic=44559.0
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#939
by
loki
on 10 Jan, 2018 12:49
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Done. Have not enough time recently to read every NSF Spacex related topics. The probability for successful launch, by my opinion, is higher than 95%. Will elaborate later.
