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A couple weeks back, a debris object was catalogued in a 210x540km orbit following the deorbit burn of the Falcon 9 second stage that launched CRS-22:

Hmm... possible that CRS-22's stage 2 made its deorbit burn in the wrong direction? Object 48832 / 2021-048B cataloged in a 210 x 540 km orbit, looks like it departed the CRS-22 insertion orbit around 1815 UTC.
Unclear for now if it's actually stage 2 or a small bit that came off

— Jonathan McDowell (@planet4589) June 4, 2021

While initial speculation focused on the idea that the second stage somehow performed the deorbit burn in the wrong direction, this was debunked soon after. To me though, that only created a more interesting question, of how debris could have come loose from a deorbiting second stage and ended up in a higher orbit.

One thought I had was that perhaps an object came loose from the stage and entered the exhaust plume of the engine, which then accelerated it into the elliptical orbit it was catalogued in.

Is this theory physically possible, or am I misunderstanding things?

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It's theoretically possible; the velocity of the exhaust plume is around 3000 m/s (pretty close to what you'd need for a translunar injection!) and the mass flow rate is ~270 kg/s, so if a small piece of debris fell off the stage into the plume, it could get quite a boost.

It seems a little unlikely that a piece big enough to track would get kicked up in this way, though.

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    $\begingroup$ Something like a thin piece of sheet metal might be; flat enough to receive a lot of the energy from the exhaust plume, and also an efficient radar reflector to be feasibly tracked. $\endgroup$ – Skyler Jun 21 at 14:04
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Not sure on the timings (or the sizes of the pieces), but the larger piece could have had more atmospheric drag on it than the smaller pieces. Thus the larger pieces are in a lower orbit than the small pieces.

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