Typically the F9 first stage and the drone ship each lose the video connection once during landing:

  1. F9 first stage during entry burn
  2. Drone ship during F9 first stage touch down (see here and here)

While item #2 has been discussed at length, my question is focusing on bullet #1.

In this video of the June 13 Starlink mission you can see the beginning of the entry burn.

Immediately on it the satellite connection regularly fails (signal loss, also visible in video). What is the reason for losing the live signal during entry burn?

The commentator says "We did lose the live signal of the first stage as expected" - why?

  • 1
    $\begingroup$ @uhoh: Those two questions target on the signal loss during touch down on the droneship. My question, however, targets on the signal loss during entry burn (which could also be reasoned by vibrations, but who knows?). $\endgroup$ – Dave Jun 13 at 23:12
  • $\begingroup$ I see that you'd linked one of them already. I made a small edit, how does it look? $\endgroup$ – uhoh Jun 13 at 23:21
  • $\begingroup$ Uninformed guess would be something akin to en.wikipedia.org/wiki/…. Going up the ideal nozzle design leaves exhaust stream at low relative velocity to the atmosphere. For the entry burn the exhaust will be interacting with the atmosphere at much higher velocity/energy and more likely to do have exotic chemistry going on. Unsure what the relevant search terms would be for this though. $\endgroup$ – GremlinWranger Jun 14 at 1:10

Almost certainly this is a combination of two things.

  1. The rocket when thrusting is more prone to vibrations.
  2. The rocket is going through its own exhaust, which is a plasma soup.

My guess is the second is the primary cause, that going through the exhaust increases the RF noise, making it difficult to be understood. This was a well known problem, RF blackouts often happen during reentry, and only have been resolved by adding in satellites. But that plasma isn't caused by rocket exhaust, which is making things even more difficult.

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