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It's a function of the shape. On a capsule-sized spacecraft, the ionized plasma completely surrounds the craft, so no radio communications can get in or out. For an oblong-shaped spacecraft, like the Space Shuttle or Starship, the descent tends to be angled such that you have a "hole" in the plasma you can get a signal through.

by albumen21 hours ago|

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No, the plasma forms a teardrop shape around small craft like Orion, completely cutting off radio comms. Larger craft like starship or the shuttle which have a roughly cylindrical shape (vs Orion’s circular cross section) aren’t fully enclosed by the plasma. The shuttle had a transmitter attached to its tail for later flights, which could send back telemetry during re-entry.

by m4rtink18 hours ago|

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Well, provided you had a 30 MW microwave transmitter on board, you could punch through the plasma just fine, it has been done:

https://en.wikipedia.org/wiki/Sprint_(missile)

"Sprint accelerated at 100 g, reaching a speed of Mach 10 (12,000 km/h; 7,600 mph) in 5 seconds. Such a high velocity at relatively low altitudes created skin temperatures up to 6,200 °F (3,400 °C), requiring an ablative shield to dissipate the heat. The high temperature caused a plasma to form around the missile, requiring extremely powerful radio signals to reach it for guidance. The missile glowed bright white as it flew."

by llbbdd21 hours ago|

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Awesome, thank you! I wonder if some kind of very long-tethered deployed antenna could enable this for the capsule or if the ratio of long-enough-to-work vs thick-enough-to-not-burn-off-completely just doesn't work. Time to read about the shuttle.

by Culonavirus21 hours ago|

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It's the shape and size.

Also Orion and other capsules fall like a rock (steep reentry profile ) compared to shuttle/starship, which intentionally slow down the reentry and kinda glide (ballpark 10min with capsules compared to 30min with shuttle/starship).

tl;dr: capsules get fully enveloped in plasma due to their shape, size and reentry profile