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What are the particular reasons that the Dragon Capsule is not communicating via Starlink, or that it seems that the audio and video downlinks from the Dragon Capsule are on separate streams?

Dagelf
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    Can you mention what it is that leads you to believe 1) "...Dragon Capsule isn't communicating via Starlink...", 2) "...audio and video downlinks from the Dragon Capsule are separate...", and 3) "...there is an ancient hand-held walkie-talkie style radio..." and mention what a "beamforming microphone" is? You can add a link to a video and mention a time within it and/or link to something you've read. Thanks! – uhoh Sep 18 '21 at 00:46
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    BTW, if you have three questions, it is much better to ask three questions, not one question. E.g. I have an answer to question #1, but I cannot post it here because it does not answer the question. – Jörg W Mittag Sep 18 '21 at 11:35
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    @JörgWMittag removed the 2nd part – Dagelf Sep 20 '21 at 18:21
  • @Dagelf - I noticed that during the YouTube livestream with the Inspiration 4 crew, the audio and video was quite noticeably out of sync, and the picture quality was not great - pretty grainy. Crew interaction starts at about 10:17 at https://www.youtube.com/watch?v=E71ffwc13y4 If that is what you are referring to, perhaps you can edit that into your question. – Nathan Sep 20 '21 at 19:48
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    Unfortunately, I still cannot post an answer because you are asking two questions, and I only have an answer to one of those two, therefore, by the rules of this site, my answer does not answer the question you asked. Sorry. – Jörg W Mittag Sep 20 '21 at 20:17
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    @JörgWMittag where are these "rules of this site"? I've never seen them. – uhoh Sep 22 '21 at 03:07
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    @uhuh: An answer must answer the question. Since the question contains two questions, and I only have an answer for one of them, my answer doesn't answer the question. – Jörg W Mittag Sep 22 '21 at 07:26
  • "Must answer the question" does not specify which of the questions... neither does it say "all of the questions". :-p An answer with one answer, I am sure would be acceptable to most rational human beings... – Dagelf Oct 15 '21 at 10:24

2 Answers2

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What are the particular reasons that the Dragon Capsule is not communicating via Starlink...

As @JörgWMittag points out the capsule orbited at an altitude higher than the Starlink satellites.

The Starlinks currently have three types of internet-related communication:

  1. downwards with customers fixed on the Earth's surface below the satellites (except an occasional individual exception one can read about)
  2. sideways with other nearby Starlink satellites
  3. downwards with Starlink ground stations for connecting to the internet.

They just don't have the hardware to talk upwards to spacecraft orbiting above them, and they might not be able to maintain communication with something below them moving at orbital velocity. It's not that it wouldn't be possible, it's just that it would require different and more complicated operation than talking to fixed points on Earth's surface registered to known customers.

...or that it seems that the audio and video downlinks from the Dragon Capsule are on separate streams?

It is most likely that for the purposes of the live broadcast the far lower bandwidth audio is transmitted over a different and more reliable channel than the video so that if the video link drops out the audio (and therefore the program) can continue and a frozen image will still appear.

It's common/normal to process audio and video separately, thus we still use those clapperboards or some facsimile thereof even in the 21st century to synchronize separate audio and image channels.

Man with a clapperboard as a scene is ready to be filmed. Production shot from KUHT-TV's Doctors in Space program with Drs. John Rider (center) and Hubertus Strughold (right)

Man with a clapperboard as a scene is ready to be filmed. Production shot from KUHT-TV's Doctors in Space program with Drs. John Rider (center) and Hubertus Strughold (right).

uhoh
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    The question doesn't specifically state Inspiration 4, maybe relevant: from https://www.inverse.com/innovation/spacex-crew-dragon-upgrade, "For Inspiration4, NASA provided communications between the ground and capsule through the Near Space Network...NASA’s network uses ground stations to offer line-of-sight communications with missions. It also uses relay satellites, placed in geosynchronous orbit, ...the crew only had limited opportunities to use the network, remarking that they only had so many ground station passes to transmit video because NASA and other agencies had priority." – Nathan Sep 22 '21 at 04:26
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    Musk's Twitter feed also mentions future Dragon to Starlink connectivity https://mobile.twitter.com/elonmusk/status/1439035515517509636 "Elon Musk Sep 17 ...Dragon will have a food warmer & free wifi next time :) Everyday Astronaut Sep 17 Will Starlink be able to provide service for vehicles below AND above them? ... Elon Musk Yeah. We’d use our Ka parabolics or laser links for Dragon, Starship or other spacecraft as soon as they got above cloud level." – Nathan Sep 22 '21 at 04:36
  • @Nathan I think you have enough for an excellent answer! – uhoh Sep 22 '21 at 14:20
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    OMW!!! So that's what a clapperboard is, and is for!!! Thank you! :-D – Dagelf Oct 15 '21 at 10:26
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Why audio/video on the Dragon Capsule are on separate streams / limited bandwidth?

@uhoh's answer gives insight into the practical reasons for separating audio and video streams.

An apparent example of these broadcast characteristics can be seen in the Inspiration 4 live orbit broadcast starting at about 10:17

I have not seen enough Dragon live orbit transmissions to know how that broadcast compares with more "typical" missions, and note that Inspiration 4 also had lower priority than other missions on the NASA Near Space Network.

From https://www.inverse.com/innovation/spacex-crew-dragon-upgrade

For Inspiration4, NASA provided communications between the ground and capsule through the Near Space Network. This connects missions with various agencies and commercial entities up to two million kilometers (1.24 million miles) away from Earth. This network brings down around 30 terabytes of data per day.

NASA’s network uses ground stations to offer line-of-sight communications with missions. It also uses relay satellites, placed in geosynchronous orbit, that can help provide continuous communications.

Jared Isaacman, the missions’ funder and a passenger on board, explained on Twitter that the crew only had limited opportunities to use the network, remarking that they only had so many ground station passes to transmit video because NASA and other agencies had priority....

Why doesn't dragon communicate via Starlink

Starlink was not a priority - Dragon was built for working with NASA so designed for its communication networks.

@uhoh's answer also points out that Starlink's design is not primarily oriented around communicating "upwards" to a space craft.

However, shortly after the Inspiration 4 mission landed, Musk indicated that Dragon to Starlink communication is likely in the future - https://mobile.twitter.com/elonmusk/status/1439035515517509636: Elon Musk Sep 17 ...Dragon will have a food warmer & free wifi next time :) | Everyday Astronaut Sep 17 Will Starlink be able to provide service for vehicles below AND above them? ... | Elon Musk Yeah. We’d use our Ka parabolics or laser links for Dragon, Starship or other spacecraft as soon as they got above cloud level.

Nathan
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  • The use of the word "cloud" leads me to think he ignored the above part of the question... – BrendanLuke15 Sep 23 '21 at 12:02
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    @BrendanLuke15 - the whole context of the tweet is orbital - you wouldn't care much about the food warmer and Wi-Fi on your way up. The tweet was also in response to this " Inspiration4 inspiration4x · Sep 17 “Can’t believe we’re eating cold pizza in space. It’s extraordinary!” – Nathan Sep 23 '21 at 14:54