SpaceX reports significant broadband satellite progress

SpaceX may be approaching debris detection as a machine-learning problem in which the entire constellation, not individual satellites, is learning to avoid collisions.

Starlink size comparison -- novel packaging accomodates
60 satellites in a single launch. (Source)

SpaceX delayed last Wednesdays Starlink launch due to high winds and on Thursday they decided to do a software update and postpone the launch until next week, but they revealed significant progress in their Starlink mission press release and in tweets by and a media call with Elon Musk.

The mission press release said SpaceX has significantly reduced the size and weight of their satellites. Their initial November 2016 FCC filing specified 386 kg satellites that measured 4 x 1.8 x 1.2 meters. In February 2018, they launched two Internet-service test satellites -- TinTin A and B -- that measured only 1.1 x .7 x .7 meters with a total mass of approximately 400 kg. The mass of the Starlink satellites will be only 227 kg, about 43% that of the test satellites. (They are still heavier than OneWeb's 147.4 kg test satellites)

As far as I know, SpaceX has not previously commented on the number of satellites that might be launched at once, but the number was generally estimated as 25-30 after considering constraints on mass, volume, and numbers of satellites per orbital plane. As shown here, they will be launching a surprising 60 flat-packed satellites. Launching 60 satellites also demonstrates continued progress in rocket capability -- this will be the heaviest SpaceX payload ever.

The speed and density of satellites in
low-earth orbit increase the likelihood
of a cascading debris collision. Source

The current and planned proliferation of low-earth orbit satellites increases the likelihood of a Kessler Syndrome event -- a cascade of collisions between satellites and the ensuing debris. The satellites will be equipped with krypton powered thrusters that will enable them to autonomously avoid collisions with on-orbit debris that is large enough to track. The thrusters will also be used to de-orbit obsolete satellites causing 95 percent of all components to quickly burn in the atmosphere.

But, what about small, untracked objects? Low-earth orbit satellites move very fast and even if a satellite had the resolution and pattern-recognition capability to "see" debris in its path, it would not be able to maneuver quickly enough to avoid a collision. That point was raised in this online discussion and a possible solution suggested -- the entire constellation could dynamically pool and share data from each satellite as well as use NORAD tracking data, which Musk mentioned during the media call.

SpaceX may be approaching this as a machine-learning problem in which the entire constellation, not individual satellites, is learning to avoid collisions using its shared data as well as data from other sources like NORAD. One can imagine sharing such data with competitors like OneWeb and Telesat or even with Russia, China or India. (Elon Musk is known to read science fiction -- this speculation is reminiscent of Azimov's Gaia or Teilhard de Chardin's noosphere).

The prospect of launching 60 satellites at once and a shared-data approach to collision avoidance have grabbed my attention, but Musk's tweets and media call were also highly informative -- a few examples:

• There's a lot of new technology in the satellites -- things could go wrong.
• The initial constellation will not have inter-satellite links.
• Each Starlink costs more to launch than it does to make.
• They will partner with telephone companies in sparsely populated regions.
• Six more launches of 60 sats needed for minor coverage, 12 for moderate.
• We have sufficient capital to build an operational constellation.

All that and they have yet to launch the satellites -- stay tuned.