Author Topic: SpaceX Falcon 9 - Iridium NEXT Flight 1 DISCUSSION (Jan. 14 2017)  (Read 339440 times)

Offline Jarnis

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"Underway" could mean "has been going for some time" and the start wasn't specified but happened earlier. It's possible that whether or not the start has been moved, it may have started before then before anyways.

The start has been moved for sure. At previous F9 FT/v1.2 launches, T-38 was the go/no-go poll before prop load.

Now it is T-78 minutes. (1h 18min)

Offline yokem55

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"Underway" could mean "has been going for some time" and the start wasn't specified but happened earlier. It's possible that whether or not the start has been moved, it may have started before then before anyways.

The start has been moved for sure. At previous F9 FT/v1.2 launches, T-38 was the go/no-go poll before prop load.

Now it is T-78 minutes. (1h 18min)
On the SES-9 pad abort, I'm wondering if the the saturated helium was only in the mix because the vehicle had pressed for flight in the previous count (wayward boat). With an instantaneous launch, it might be possible to stretch out the countdown and tanking as the HE won't be pressing the stage until the last minutes before launch.
« Last Edit: 01/14/2017 01:43 PM by yokem55 »

Offline Rocket Science

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WX still looks good for today, about 40% chance of winds violation...
"The laws of physics are unforgiving"
~Rob: Physics instructor, Aviator, Vintage auto racer

Offline kaiser

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I assume that the Northern/larger hazard area is for the ASDS landing.  What is the narrow hazard zone immediately to the south?  Fairings?  And the hazard area is huge I guess it includes certain failure modes.

It might not be fair to characterize all the dispersion as occurring only in failure mode cases. As regards the larger (presumably ASDS) zone, returning stage flight through a box that big might be the result of uncertainties about the boostback burn. Sepculating about the long thin (presumably fairing) zone, it could indicate SpaceX does not believe the fairing descent will be purely ballistic in nature, i.e. aerodynamics might play a part.
Fair point.  I'm curious how they determine hazard zones.

1e-X risk of a piece of debris Y size hitting an aircraft, and 1e-Q risk of a piece of debris R size hitting a boat. All based upon instantaneous energy available -- velocity, height, fuel on board for kaboom.

Offline meekGee

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I assume that the Northern/larger hazard area is for the ASDS landing.  What is the narrow hazard zone immediately to the south?  Fairings?  And the hazard area is huge I guess it includes certain failure modes.

It might not be fair to characterize all the dispersion as occurring only in failure mode cases. As regards the larger (presumably ASDS) zone, returning stage flight through a box that big might be the result of uncertainties about the boostback burn. Sepculating about the long thin (presumably fairing) zone, it could indicate SpaceX does not believe the fairing descent will be purely ballistic in nature, i.e. aerodynamics might play a part.
Fair point.  I'm curious how they determine hazard zones.

1e-X risk of a piece of debris Y size hitting an aircraft, and 1e-Q risk of a piece of debris R size hitting a boat. All based upon instantaneous energy available -- velocity, height, fuel on board for kaboom.
How do they know how many pieces are generated by the hypothetical explosion? 
ABCD - Always Be Counting Down

Offline toruonu

Well the fact that a few have blown up might help the modeling ;)

Offline meekGee

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Well the fact that a few have blown up might help the modeling ;)
How many of the pieces (not mass fraction) were recovered?  And would an in-flight explosion of unknown mechanism be similar to a pad explosion?
ABCD - Always Be Counting Down

Offline deltaV

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Does anyone know when the webcast is supposed to start? The YouTube technical version of the webcast is showing a counter that's counting down to 9:54:00 local, i.e. less than a minute before liftoff. I'm assuming they'll show us more of the countdown than that.

Offline old_sellsword

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Does anyone know when the webcast is supposed to start? The YouTube technical version of the webcast is showing a counter that's counting down to 9:54:00 local, i.e. less than a minute before liftoff. I'm assuming they'll show us more of the countdown than that.

They generally start at T-20 minutes, but the YouTube countdown timer is set to T-0.

Online launchwatcher

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Does anyone know when the webcast is supposed to start? The YouTube technical version of the webcast is showing a counter that's counting down to 9:54:00 local, i.e. less than a minute before liftoff. I'm assuming they'll show us more of the countdown than that.
Press kit PDF at http://www.spacex.com/sites/spacex/files/spacex_iridium1_press_kit.pdf says:
Quote
WEBCAST | Launch webcast will be live about 20 minutes before launch at spacex.com/webcast

Online Lar

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Well the fact that a few have blown up might help the modeling ;)
How many of the pieces (not mass fraction) were recovered?  And would an in-flight explosion of unknown mechanism be similar to a pad explosion?
I would think they'd just do worst case assumptions, informed by experience.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline meekGee

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Well the fact that a few have blown up might help the modeling ;)
How many of the pieces (not mass fraction) were recovered?  And would an in-flight explosion of unknown mechanism be similar to a pad explosion?
I would think they'd just do worst case assumptions, informed by experience.
I'd hate to belabor the point, but how?

Over-water failures don't help.  Different rockets have different structures. Different failures produce wildly different numbers of debris.

What I'm saying is - it's probably not a 1e-x thing, but simply "maximum range a piece of debris can travel".  That's easier to calculate.  (Big pieces travel further, but are shot out slower...)

Which will make the odds of being hit very low indeed.
ABCD - Always Be Counting Down

Online leovinus

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Is there a picture somewhere that shows the flight path out of Vandenberg?

Online Kosmos2001

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Offline Paul_G


Offline kaiser

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Well the fact that a few have blown up might help the modeling ;)
How many of the pieces (not mass fraction) were recovered?  And would an in-flight explosion of unknown mechanism be similar to a pad explosion?

You can pretty much assume all sizes in the statistical analysis. Big pieces are draggy and don't go far. Little pieces don't go too far either. It's really the medium to medium small sized stuff that usually makes the edge conditions from what I've seen.

Online Brovane

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Beautiful weather for a launch.  It is like a Tesla meet up out here at Ocean.
"Look at that! If anybody ever said, "you'll be sitting in a spacecraft naked with a 134-pound backpack on your knees charging it", I'd have said "Aw, get serious". - John Young - Apollo-16

Online Prettz

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https://www.flightclub.io/world/?code=IRD1&view=space gives a visualisation of the launch track.

Paul
So it takes off like an airplane then does a 90 degree turn? Interesting.

Offline Pete

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If you want to watch either the Hosted Webcast or the Technical Webcast on YouTube, both of them start at 17:20 UTC (9:20 AM local).

In other words, the countdown will be at T-34 minutes at the time the webcasts begin.

Thanx for the info, i was wondering why the webcasts were dry, yet the update board was full of detail.


Was afraid I would miss the whole thing, like that time I logged in AT the time webcast said it would begin, only to see the Falcon already ascending off the pad. (they sometimes make the "time" of the webcast be liftoff time, and sometimes its start-of-transmission time....)

Offline Paul_G

https://www.flightclub.io/world/?code=IRD1&view=space gives a visualisation of the launch track.

Paul
So it takes off like an airplane then does a 90 degree turn? Interesting.

I think there are some 'glitches' with it. I just noticed that, mashed some buttons, dragged the view around a bit, and it suddenly looks more like a rocket launch and not a plane departure.
« Last Edit: 01/14/2017 06:41 PM by Lar »

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