FWIW, I asked on reddit, and the universal response was that atmospheric drag really can slow it down that much.

That really does have to be the answer. There really isn't anything else going on to slow it. Maybe the numbers flashing by were just messing me up.

Donger, if you want some more technical explanations...

https://www.reddit.com/r/spacex/comm...dates/dscgtet/

Yep, I get it. But again. I was surprised at the rate of deceleration due to just atmospheric "drag"

Rumblings that the payload for the Zuma mission did not achieve orbit. Possibly disinformation, of course.

It's definitely weird. The only official statement is that the F9 performed its duties fine. The payload is classified, so who knows if it ended up having an issue of its own or if it was some sort of test that didn't really require a true orbit. Or maybe it's up there just fine, and all of this secrecy is just to further conceal the mission's purpose.

I doubt we'll ever know, but it doesn't seem like SpaceX is reacting like anything went wrong at all. FH is rolling out for what is expected to be a Wednesday static fire, and there haven't been any rumblings at all about any other launches being delayed due to a failure.

In the meantime, this shot from the launch is really cool.

<a data-flickr-embed="true" data-context="true" href="https://www.flickr.com/photos/spacex/39585575631/" title="Zuma Mission"><img src="https://farm5.staticflickr.com/4603/39585575631_67ecc76b5d_c.jpg" width="800" height="534" alt="Zuma Mission"></a><script async src="//embedr.flickr.com/assets/client-code.js" charset="utf-8"></script>

The picture is interesting, I get the two lines where the first stage did it's burns, and the gap seen in the arc between MECO and the second stage starting up, the up-loop showing the back-burn of the first stage, but I don't get why the first burn of the first stage's reentry burn appears higher than where the first and second stages separated.

Just angles?

It definitely kicks up higher the during the boostback burn. Some of it's probably angles, but it probably starts the reentry burn in about the same spot as separation.

This illustration's not to scale or anything, but should give you the gist.

https://i.imgur.com/D9BdO86.png

Welp, this doesn't sound good.

Highly classified US spy satellite appears to be a total loss after SpaceX launch

That helps a lot. Thanks..

For what it's worth, here's Gwynne's official statement about Zuma:

So basically, it sounds like the satellite itself was a loss, but at least for now, it looks like the issue was that the connector to the F9 second stage didn't release properly. In this case, that connector wasn't designed by SpaceX, so it's not on them.

So good news: no delays to FH or the rest of SpaceX's manifest. Bad news: the U.S. appears to have lost a very expensive satellite.

That's just what they want you to think... :)

Misdirection is certainly a plausible answer here too. I don't think we'll ever know...