APOD: Launch and Landing (2018 Jan 13)

Comments and questions about the APOD on the main view screen.
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APOD Robot
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APOD: Launch and Landing (2018 Jan 13)

Post by APOD Robot » Sat Jan 13, 2018 5:05 am

Image Launch and Landing

Explanation: A composite of three consecutive exposures, this night skyscape follows the January 7 launch and first stage landing of a Falcon 9 rocket from a beach on planet Earth's space coast. With the launch from Cape Canaveral Air Force Station, the bright streak beginning farthest left traces the initial phase of the rocket's flight. A visible upward hook marks the first stage beginning its return trajectory with a "boostback burn" near the top of the arc, while the second stage separates and continues toward orbit. Above the top of the launch arc due to perspective, a bright streak shows the returning first stage slowing and descending toward the Cape. Centered below, the streak at the horizon is a 17 second burn finally slowing the first stage to a successful vertical landing about 8 minutes after launch at Landing Zone 1. During the scene's effective long exposure time, the background stars leave short trails in the night sky of the rotating planet.

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heehaw

Re: APOD: Launch and Landing (2018 Jan 13)

Post by heehaw » Sat Jan 13, 2018 10:37 am

What a marvelous photograph!

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orin stepanek
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Re: APOD: Launch and Landing (2018 Jan 13)

Post by orin stepanek » Sat Jan 13, 2018 11:49 am

Landing like old sifi! Reminds me of Buck Rogers and Flash Gordon! :wink: Or Abbot & Costello go to Venus!
Orin

Smile today; tomorrow's another day!

heehaw

Re: APOD: Launch and Landing (2018 Jan 13)

Post by heehaw » Sat Jan 13, 2018 2:08 pm

orin stepanek wrote:Landing like old sifi! Reminds me of Buck Rogers and Flash Gordon! :wink: Or Abbot & Costello go to Venus!
You nailed it!

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Re: APOD: Launch and Landing (2018 Jan 13)

Post by neolefty » Sat Jan 13, 2018 9:30 pm

I love this photo! And that it was taken by an 18-year-old. There's a great discussion of the photo on r/spacex: https://www.reddit.com/r/spacex/comment ... yload_and/

About the boostback burn: I think it is immediately after stage separation, vectored horizontally back towards land. That seems like the most efficient approach. It's kind of dim in the photo because it's facing away from the camera.

asmacarthur

Re: APOD: Launch and Landing (2018 Jan 13)

Post by asmacarthur » Sun Jan 14, 2018 3:06 am

The description is very difficult to follow and appears inaccurate to me as a result. I could have benefitted from a labeled approach as "(1) stage one boost back burn" type description. Stage one appears to be associated with the three brightest lines. The "hook"? etc are where you lose me. The only thing that appears as not stage one to me is the faint line continuing to the right.

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MarkBour
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Re: APOD: Launch and Landing (2018 Jan 13)

Post by MarkBour » Sun Jan 14, 2018 7:38 am

What a beautiful sequence in this image !

The photographer has a lot of lovely work on his website (http://www.johnkraussphotos.com, as credited in the corner of the photo) which also shows he has been perfecting this shot, with similar images taken on December 21, 2015 and July 18, 2016 there in his blog sequence. This one is particularly nice, capturing the entire sequence in a relatively cloudless sky. As the caption states, it must be an 8-minute time exposure, overall.
asmacarthur wrote:The description is very difficult to follow and appears inaccurate to me as a result. I could have benefitted from a labeled approach as "(1) stage one boost back burn" type description. Stage one appears to be associated with the three brightest lines. The "hook"? etc are where you lose me. The only thing that appears as not stage one to me is the faint line continuing to the right.
If you can see this link, it is annotated for you: https://i.imgur.com/ldKPQib.jpg .

In the reddit discussion that neolefty kindly linked above, I see that some posters have explained some of the details that might not be apparent on first viewing the image. The photographer also gave some helpful info. Quoting him:
  • Spacing was roughly as follows. 00:00 is liftoff.
    • Exposure 1: 00:00 -> 3:13
      Exposure 2: ~3:15 -> ~5:15
      Exposure 3: ~6:00 -> ~8:00
This explains a small gap in the trails, as the camera was not rolling from 5:15 to 6:00. The largest gap in the parabolic launch arc, though, would be around stage separation where there is simply no burning taking place. I am guessing the camera was set differently for the middle exposure, as an explanation for why the middle part looks bluer, and the middle parts of the star trails look brighter.

As reddit posters pointed out, during the re-entry burn, you can see that it starts with 1 engine, then changes to 3 engines, then ends with just 1 engine. And in the final landing burn, it appears that the booster passed through two places in the atmosphere (with increased moisture content?) that produced a flare-out of condensation from the descent path.
Mark Goldfain