Author Topic: SpaceX Falcon 9 - Iridium NEXT Flight 1 DISCUSSION (Jan. 14 2017)  (Read 336317 times)

Offline Jim

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What do most second stages use for position and orientation IMUs and a star tracker?

Launch vehicles don't use star trackers.  The IMU's are aligned before launch

Online LouScheffer

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What do most second stages use for position and orientation IMUs and a star tracker?
Launch vehicles don't use star trackers.  The IMU's are aligned before launch
Part of the pre-launch checks is making sure the IMUs can detect the rotation of the Earth.  This means they are using an inertial reference frame already, which is exactly what they need for yaw steering.  So no extra work (from the nav system) is needed for this.  The control system, of course, still needs to get the right coordinates as efficiently as possible, while respecting aero loads, ground track, etc.  That's where the extra work is, not in the position measurement.


Online Chris Bergin

I wonder if there's a link that shows that new NOTAM anywhere?

Online jpo234

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I wonder if there's a link that shows that new NOTAM anywhere?

Searching for "SPACE OPERATIONS" type NOTAMS on http://tfr.faa.gov draws a blank.
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Online envy887

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https://pilotweb.nas.faa.gov/PilotWeb/ doesn't show any launch-related NOTAMs for Vandenberg (location VBG) as of 17:00 UTC

Online Robotbeat

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F9 is vertical and going for an attempt today.

Will update again if we hear of a firing. HOWEVER, as per usual, only SpaceX (or Iridium as the customer) can declare a good static fire, usually via Twitter. Then it'll be data review and LRR.

Are they doing the static fire with the payload attached? :'D
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Online Flying Beaver

F9 is vertical and going for an attempt today.

Will update again if we hear of a firing. HOWEVER, as per usual, only SpaceX (or Iridium as the customer) can declare a good static fire, usually via Twitter. Then it'll be data review and LRR.

Are they doing the static fire with the payload attached? :'D

It's been talked about extensively, and confirmed by the Iriduim CEO. No...
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Online Chris Bergin

F9 is vertical and going for an attempt today.

Will update again if we hear of a firing. HOWEVER, as per usual, only SpaceX (or Iridium as the customer) can declare a good static fire, usually via Twitter. Then it'll be data review and LRR.

Are they doing the static fire with the payload attached? :'D


Offline zubenelgenubi

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Are they doing the static fire with the payload attached? :'D
:D Stirring the pot? ;D
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Online KaiFarrimond

Do you have any idea of the time that the static fire could occur? Or is it just wait and see? Thanks
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Online launchwatcher

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The hardware seems like it should be capable of doing this,

Based on what?  Do you know the avionics architecture?
It seems this would be a software limitation, not a hardware one, right?
Seems more like a feature that SpaceX deprioritized because it competes with their long-term goals - they clearly prefer to put excess launch vehicle performance towards recovery in order to enable reuse..

Online Chris Bergin

Do you have any idea of the time that the static fire could occur? Or is it just wait and see? Thanks

Now then Kai. Static Fire's have long windows, very unlikely a launch attempt. They do have target T-0s, but just class this one as potentially happening soon, knowing they could go anytime between now-ish and the next several hours....or not at all.

Offline Jim

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Seems more like a feature that SpaceX deprioritized because it competes with their long-term goals - they clearly prefer to put excess launch vehicle performance towards recovery in order to enable reuse..

Not really.  There have been many missions with excess performance even with taking into account recovery.

Online mn

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I think it's worth requoting, there's been much discussion about whether or not the hardware/software can or cannot do this, totally ignoring what seems like a very good reason why it likely doesn't matter to them at this point.

Implementing yaw steering might be a low priority for SpaceX since steering gets expensive once your time from optimum exceeds a few minutes.  And if I remember right, it takes SpaceX about 10 minutes to recycle the count.  By that time the needed yaw steering would only be practical for missions with lots of extra performance.  Also, yaw steering would throw yet another wrinkle into recovery of the first stage.  So maybe they decided to stick with instantaneous windows for now.

Does anyone really think SpaceX can't do it if they wanted to?

Whether or not the 'vehicle' (trying to avoid hardware or software ;)) can do it today is not that important of a question IMHO. I think if they are not doing it it's because they decided it's not worth the effort as Lou explained.

Offline Jim

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And if I remember right, it takes SpaceX about 10 minutes to recycle the count.  By that time the needed yaw steering would only be practical for missions with lots of extra performance. 


It doesn't have to be a recycle.  It could help when picking up the terminal count late.

  Also, yaw steering would throw yet another wrinkle into recovery of the first stage. 


Not really, the boost back could take care of it.

Online mn

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It doesn't have to be a recycle.  It could help when picking up the terminal count late.


How many F9 launches did we have a situation where you can see 10 minutes in advance that you would like to move the T0 by a few minutes to get a better odds of a GO - trying to fly between the clouds...? Was there ever a F9 launch scrubbed because the weather was RED at T0 but they could have gotten a GREEN had they been able to adjust the T0 10 minutes in advance? I think the point is that such a scenario is so rare that it's not worth the effort at this time.

Offline Jim

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1.  How many F9 launches did we have a situation where you can see 10 minutes in advance that you would like to move the T0 by a few minutes to get a better odds of a GO - trying to fly between the clouds...?

2. Was there ever a F9 launch scrubbed because the weather was RED at T0 but they could have gotten a GREEN had they been able to adjust the T0 10 minutes in advance?


1.  Boat in the box, bad weather, range problem, GSE problem, etc.  Many things that could clear up in few minutes instead of scrub for an instantaneous window.

2.  yes.

Offline Star One

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Elon Musk Verified account ‏@elonmusk

Hold-down firing of @SpaceX Falcon 9 at Vandenberg Air Force completed. All systems are go for launch next week.

https://mobile.twitter.com/elonmusk/status/817123579343028227
« Last Edit: 01/05/2017 08:52 PM by Star One »

Online Robotbeat

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This is the discussion thread, y'all. :)
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