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[–]0hmyscience 10 points11 points  (14 children)

So what's going on here?

  1. The arch on the left, I assume, is the rocket launching.
  2. Where the arch ends, it turns blue, goes off, but them it seems to briefly re-ignite on the opposite direction? Is that right?
  3. The bottom "pillar", I assume that's the rocket landing. But which part is this? The other vertical "pillar" up in the air, or the same part from the arch?
  4. Where did the "pillar" on the top come from? Also, is it going upwards or downwards?
  5. I see other small horizontal-ish lines there... are those just star trails?

[–]jardeon[S] 15 points16 points  (5 children)

You've basically got it!

The arc on the left is liftoff, the first stage of the rocket carrying the payload off the ground.

That arc ends about 2.5 minutes in flight, as the main engine shuts down (the transition from yellow to red to blue). The second stage of the rocket separates and ignites, while the first stage pitches around and relights its engines to put it on a trajectory back towards Cape Canaveral (the bluish hook near the top of the arc).

The second stage is using just one engine, while the first stage uses nine, plus it's farther away, so its streak appears fainter.

That "boostback" by the first stage is the first of three burns that ultimately end with the landing.

The vertical pillar near the top is the second burn, the "re-entry" burn, which slows the rocket down from supersonic speeds to ensure it doesn't break apart when re-entering the thicker portions of the Earth's atmosphere. In this picture, you can actually see the transition points where the rocket was using one, then three, then finally one engine again, note on that vertical pillar where it gets thicker near the middle and thinner at the ends. The rocket is traveling "top to bottom" in the photo.

The pillar on the right is the landing burn, the third and final time the engines are re-lit on the first stage, as the rocket touches down gently at LZ-1, Cape Canaveral Air Force Station.

And yes, the other, fainter lines are star trails, recorded for nearly eight minutes while the shutter was open.

[–]0hmyscience 4 points5 points  (0 children)

you can actually see the transition points where the rocket was using one, then three, then finally one engine again,

Wow that's awesome, definitely didn't notice that the first time.

Thanks for the detailed explanation! It makes this picture even cooler!

[–]Cryogenicist 0 points1 point  (1 child)

How fast is it moving when the first stage turns around? I find it amazing that the first stage rockets can turn around, decelerate, and then return to the launch site.

[–]jardeon[S] 1 point2 points  (0 children)

From the SpaceX launch webcast, stage 1 is moving at over 4,000km/h when stage separation occurs.

[–]night_of_knee 0 points1 point  (1 child)

[–]jardeon[S] 1 point2 points  (0 children)

Mostly; the blue streaks in the upper right are star trails, not the exhaust from the rocket. I think the first stage follows a "loopier" path on boostback, without the hard turn at the top of the arc.

[–]AskMeForADadJoke 4 points5 points  (7 children)

Heres an animation of how it all works.

Its not the exact rocket (this one has two first stages) but the idea is there.

And here is the actual launch/landing

[–]codeByNumber 1 point2 points  (1 child)

It’s honestly still just mind blowing to me.

[–]AskMeForADadJoke 0 points1 point  (0 children)

Completely agree

[–]shakexjake 0 points1 point  (4 children)

Asking here because I'm not sure who else to ask: What was slowing down Stage 1 between the entry and landing burns? Did it really slow down about 2k kph just from air resistance?

I'd also like to ask you for a dad joke.

[–]AskMeForADadJoke 1 point2 points  (2 children)

Asking here because I'm not sure who else to ask: What was slowing down Stage 1 between the entry and landing burns? Did it really slow down about 2k kph just from air resistance?

No idea. I would think so, but I have zero credentials to answer.

I'd also like to ask you for a dad joke.

Why was the poor man selling yeast?

He kneaded to raise some dough.

[–]shakexjake 1 point2 points  (1 child)

Thank you for answering both of my requests!

[–]AskMeForADadJoke 0 points1 point  (0 children)

Of course :)

I would ask r/spacex or r/askscience

[–]quarkman 1 point2 points  (0 children)

Yes, the 2k kph slowdown is entirely air resistance. Terminal velocity is only around 500kph max, so that's quite a bit slower than the 3k kph it was starting out after the initial reentry burn.

Note that they initially didn't have the first reentry burn and the rocket came in too hot.