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by llbbdd 63 days ago
Would this capsule had been been able to communicate if it was integrated with starlink or is the size more important? I'd imagine if they could have achieved communication via Starlink they would have done it, but just curious.
3 comments
rufo 63 days ago
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.
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albumen 63 days ago
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.
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m4rtink 63 days ago
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."

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llbbdd 63 days ago
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.
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Culonavirus 63 days ago
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

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