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#960
by
CyndyC
on 10 Jan, 2018 22:02
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Someone mentioned that the new frequencies are on amateur radio bands? I wonder if they are for the payload. "Tesla to mars, playing David Bowie's Space Oddity." Someone's got to be able to hear it...
Exactly my first reaction [
edit: the idea aligns with the Elon Musk/SpaceX sense of humor]. The earlier quote you referred to is below
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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#961
by
llanitedave
on 10 Jan, 2018 22:49
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reddit user jdnz82 said that KSC officials were given a notice of a (gasp) 15 second firing!
The resident alligators are not going to be happy!
I remember the larger alligators during a Saturn-V launch coming to the surface and bellowing, similar to a grunting. It has been speculated (I stress that) that the vibrations of the launch felt similar to the gators as a mating call. All I can tell you is that I could feel it pounding inside my chest as all that thunder rose into the sky.
That's kind of what it felt like to me, too. Not that the female gators were actually cooperating...
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#962
by
groknull
on 10 Jan, 2018 23:07
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Someone mentioned that the new frequencies on in amature radio bands? I wonder if they are for the payload. "Tesla to mars, playing David Bowie's Space Oddity." Someone's got to be able to hear it...
The frequencies are not in the Amateur Radio bands. Close, but not in. See below.
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.
2232.5 and 2272.5 MHz are in a frequency range allocated to space related activities. The next higher frequency range includes Amateur Radio allocations. Radio receivers can often tune to higher or lower frequencies than strictly needed for the service.
avollhar is correct. "Well within the capabilities of amateur radio..." means that an Amateur Radio receiver or transceiver that is capable of operating in the 13cm band will likely be able to tune down to 2232.5 and 2272.5 MHz.
See the following PDF for frequency allocations. Note that ITU Region 2 includes the Americas (and thus, the United States), but there may be additional permissions and restrictions added by the FCC. Those are called out in the right hand columns under "United States Table".
https://transition.fcc.gov/oet/spectrum/table/fcctable.pdfSee page 38 for the applicable space allocations, and pages 38 and 39 for the adjacent Amateur allocations.
Edit: cleaned up quotes
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#963
by
RocketLover0119
on 10 Jan, 2018 23:18
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#964
by
FutureMartian97
on 11 Jan, 2018 00:23
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A reddit user (who has eyes on FH from the SFN webcam) claims that venting was visible from it... WDR??
https://www.reddit.com/r/spacex/comments/7ph9e2/comment/dshowsb
It would make sense. I didn't really understand how they were going to do a WDR, verify the data, and THEN static fire without the fuel warming up to much.
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#965
by
Lar
on 11 Jan, 2018 02:38
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A reddit user (who has eyes on FH from the SFN webcam) claims that venting was visible from it... WDR??
https://www.reddit.com/r/spacex/comments/7ph9e2/comment/dshowsb
It would make sense. I didn't really understand how they were going to do a WDR, verify the data, and THEN static fire without the fuel warming up to much.
Depends on what "verify" means. If algorithmic checks? could be done in seconds. If humans, a few minutes one would think at the least....
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#966
by
RoboGoofers
on 11 Jan, 2018 03:01
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A reddit user (who has eyes on FH from the SFN webcam) claims that venting was visible from it... WDR??
https://www.reddit.com/r/spacex/comments/7ph9e2/comment/dshowsb
It would make sense. I didn't really understand how they were going to do a WDR, verify the data, and THEN static fire without the fuel warming up to much.
It's also a good idea to test de-tanking.
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#967
by
loki
on 11 Jan, 2018 08:27
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A reddit user (who has eyes on FH from the SFN webcam) claims that venting was visible from it... WDR??
https://www.reddit.com/r/spacex/comments/7ph9e2/comment/dshowsb
It would make sense. I didn't really understand how they were going to do a WDR, verify the data, and THEN static fire without the fuel warming up to much.
It's also a good idea to test de-tanking.
I believe de-tanking must be tested for the new designed rocket per KSC safety rules.
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#968
by
luinil
on 11 Jan, 2018 09:30
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As the static fire will consume only a small part of the propellent they will have to de-tank anyway, not sure that's an issue
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#969
by
Ben the Space Brit
on 11 Jan, 2018 09:35
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They'll want to have at least fill/drain cycle to make sure that the tanks and plumbing are good before risking the engines (and, frankly, the entire vehicle) with a live fire.
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#970
by
loki
on 11 Jan, 2018 11:06
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It has been a lot of discussions about engines start sequence on this thread.
Today is probably “The Day”, so here is my opinion.
A staggered start sequence is applied to avoid impact overload on engines support structure. Minimum pause between starts of engines or group of engines fairing is defined as a needed time for support construction to make a couple natural oscillations for that load case (Spacex’s designers will probably choose more conservative value for the first static fire). For Falcon Heavy case, with three boosters strapped together, engines have to be started symmetrically with respect to XZ plane of central core, to avoid twisting of the rocket assembly. One of possible start sequences could be like this:
1. Simultaneously start of four engines, two per each side booster (engines on the same booster are opposite to each other, in plane parallel with XZ plane and both groups are symmetrical with respect to XZ plane of central core), pause, followed by start of four engines on central core, pause.
2. Again simultaneously start of four engines, two per each side booster (engines on the same booster are opposite to each other, in plane parallel with XZ plane and both groups are symmetrical with respect to XZ plane of central core), pause, followed now by two engines on central core, pause .
3. Simultaneously start of four engines, two per each side booster (engines on the same booster are opposite to each other, in plane parallel with XZ plane and both groups are symmetrical with respect to XZ plane of central core, pause.
4. Than we have the last nine engines, which are in XY plane, to be lit, simultaneously starting four engines, two per each side booster (engines on the same booster are opposite to each other, in XY plane and both group are symmetrical with respect to XZ plane of central core), pause, followed by two engines on central core (opposite to each other, in XY plane), pause.
5. And finally, simultaneously start of all three central engines.
Will be a long day…
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#971
by
AncientU
on 11 Jan, 2018 11:17
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You've got a second or two... get on with it.
Only timing mentioned AFAIK was 120ms between starts...
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#972
by
loki
on 11 Jan, 2018 11:52
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Maybe, for the first static fire, they choose more conservative timing of 200 msec between starts...
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#973
by
eriblo
on 11 Jan, 2018 11:55
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You've got a second or two... get on with it.
Only timing mentioned AFAIK was 120ms between starts...
...which is just a mention of the staggering of the SSME's. I don't think we have heard any numbers for FH.
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#974
by
EngrDavid
on 11 Jan, 2018 12:52
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Quick question....does the LOX get dumped into the atmosphere during unloading of the tank after WDR? How long does it take to replenish the LOX farm?
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#975
by
jjyach
on 11 Jan, 2018 13:23
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Quick question....does the LOX get dumped into the atmosphere during unloading of the tank after WDR? How long does it take to replenish the LOX farm?
It gets detanked back to the Lox farm. There is usually enough Lox around for 3-4 attempts on a given day, but if they max out attempts I believe it takes at least a day for the whole system to cool it down enough to be ready to be able to re-attempt.
For FH I would assume they may have more on hand, but I can easily see how there may be only one attempt per day
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#976
by
Jim
on 11 Jan, 2018 14:06
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It gets detanked back to the Lox farm. There is usually enough Lox around for 3-4 attempts on a given day,
one attempt with sub cooled LOX
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#977
by
jjyach
on 11 Jan, 2018 14:26
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It gets detanked back to the Lox farm. There is usually enough Lox around for 3-4 attempts on a given day,
one attempt with sub cooled LOX
Well once they start a LOX fill they are committed to one T-0, but if they scrub after LOX loading they have a 90 min recycle, so they are able to do multiple in a day, if they have multiple opportunities. I've been in the rehearsals where they have done this scenario with subcooled LOX.
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#978
by
mn
on 11 Jan, 2018 14:38
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It has been a lot of discussions about engines start sequence on this thread.
Today is probably “The Day”, so here is my opinion.
A staggered start sequence is applied to avoid impact overload on engines support structure. Minimum pause between starts of engines or group of engines fairing is defined as a needed time for support construction to make a couple natural oscillations for that load case (Spacex’s designers will probably choose more conservative value for the first static fire). For Falcon Heavy case, with three boosters strapped together, engines have to be started symmetrically with respect to XZ plane of central core, to avoid twisting of the rocket assembly. One of possible start sequences could be like this:
1. Simultaneously start of four engines, two per each side booster (engines on the same booster are opposite to each other, in plane parallel with XZ plane and both groups are symmetrical with respect to XZ plane of central core), pause, followed by start of four engines on central core, pause.
2. Again simultaneously start of four engines, two per each side booster (engines on the same booster are opposite to each other, in plane parallel with XZ plane and both groups are symmetrical with respect to XZ plane of central core), pause, followed now by two engines on central core, pause .
3. Simultaneously start of four engines, two per each side booster (engines on the same booster are opposite to each other, in plane parallel with XZ plane and both groups are symmetrical with respect to XZ plane of central core, pause.
4. Than we have the last nine engines, which are in XY plane, to be lit, simultaneously starting four engines, two per each side booster (engines on the same booster are opposite to each other, in XY plane and both group are symmetrical with respect to XZ plane of central core), pause, followed by two engines on central core (opposite to each other, in XY plane), pause.
5. And finally, simultaneously start of all three central engines.
Will be a long day…
Interesting theory, it's just that Chris G already said
"For Falcon Heavy, it is understood that two engines will be lit simultaneously followed by the next two… and so on until all 27 are up and running. The timing of this ignition sequence will be such that it will look simultaneous to the naked eye"
https://www.nasaspaceflight.com/2018/01/spacex-static-fire-falcon-heavy-1/I'm going to assume he didn't make it up.
We'll know the answer soon enough, hopefully later today.
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#979
by
Johnnyhinbos
on 11 Jan, 2018 14:46
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When was the last time this much energy has been (deliberately) unleashed at the Cape?
I have tremendous new respect for the reaction frame, and its attachment points to terra firma, for holding onto this beast, even for a small collection of seconds. How much weight is shed during a 12 second burn, with a best guess at staggered engine start?