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On the recent Iridium 1 launch the separation of the first and second stages can be seen at T+3:50. In the following screenshot we see the second stage burning at the lower left of the frame and the first stage dropping away at the upper right.

What are the two bright objects perceived between the first and second stages in the image?

enter image description here

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I think that's the fairing (the shell around the satellites on top of the second stage).

The fairing separates into 2 halves, those are the only objects large enough to be visible in this photo. At T+3:18 of that video, you can hear one of the technicians say "Fairing separation confirmed". Right after that, the first bright object separates from the second stage.

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They look like the fairing separating. It turns out that if you reuse the first stage, but throw away the fairing and second stage, the next most valuable thing that might be worth recovering is actually the fairing.

They are large, somewhat complex structures. Need to be light, strong and large. There has been speculation that they are attaching thrusters of some kind to the fairings to test different approaches to recovering the fairings from launch.

There has been speculation that one of the recovery ships, based on its location during ASDS operations is trying to recover the fairing if it made it back through the atmosphere.

The beauty of the SpaceX model is that with so many launches, they can keep trying different ideas until they get it just right. Their model includes the cost of the fairing in the launch already, so experimenting with it after separation can be a cheap way to test things that are very hard to test on the ground.

You can see this with their recovery of the first stage attempts, where they kept trying with minor tweaks (grid fins, more hydraulic fluid, better legs, 3 burns, 2 burns, 1 engine burns, 3 engine burns) until they got it right. Now they seem like it is odd that EcoStar 23 will be an expendable flight. Normal has become recovering the stage.

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  • $\begingroup$ "Normal has become recovering the stage." Really? Still seems pretty experimental to me. $\endgroup$
    – Lightness Races in Orbit
    Feb 2, 2017 at 16:27
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    $\begingroup$ @LightnessRacesinOrbit I guess that for SpaceX, "normal" and "experimental" aren't mutually exclusive. $\endgroup$
    – Maxander
    Feb 2, 2017 at 16:32
  • $\begingroup$ @Maxander: I suppose :) Now, I haven't been paying much attention, but haven't there been quite a few explosive recovery failures lately? More so than successes perhaps? $\endgroup$
    – Lightness Races in Orbit
    Feb 2, 2017 at 16:32
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    $\begingroup$ @LightnessRacesinOrbit perhaps Elon Musk is just playing Kerbal Space Program with regular rockets. In that case explosions are a part of the plan. $\endgroup$
    – John Dvorak
    Feb 2, 2017 at 17:33
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    $\begingroup$ @LightnessRacesinOrbit Two Loss of missions. CRS-9 was an upper stage issue so no landing attempt. Second was AMOS-6 during a wet test on the pad, not a launch attempt. Since Jason-3 (Jan 2016) all the recovery attempts have succeeded I think? They have 7 recovered cores right now I think. (1 on display outside factory in Hawthorne. One refurbed for SES-10 launch (CRS-8 stage), Thaicom-8 being refurbed to be Falcon Heavy side booster. JSAT-14 was test fired 10+ times. Orbcomm is still in LC39A HIF. (Last report I heard was 3 cores in the HIF, room for 5). $\endgroup$
    – geoffc
    Feb 2, 2017 at 18:25

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