SPACEX’S APPROACH TO SPACE SUSTAINABILITY AND SAFETY

  • Designing and building highly reliable, maneuverable satellites that have demonstrated reliability of greater than 99%
  • Operating at low altitudes (below 600 km) to ensure no persistent debris, even in the unlikely event a satellite fails on orbit
  • Inserting satellites at an especially low altitude to verify health prior to raising into their on-station/operational orbit
  • Transparently sharing orbital information with other satellite owners/operators
  • Developed an advanced collision avoidance system to take effective action when encounter risks exceed safe thresholds

DESIGNING AND BUILDING SAFE, RELIABLE AND DEMISABLE SATELLITES

SpaceX satellites are designed and built for high reliability and redundancy in both supply chain and satellite design to successfully carry out their five-year design life. Rigorous part and system-level screening and testing enable us to reliably build and launch satellites at very high rates. We have the capacity to build up to 45 satellites per week, and we have launched up to 240 satellites in a single month. This is an unprecedented rate of deployment for a complex space system — and reflects SpaceX’s commitment to increase broadband accessibility around the world with Starlink as soon as feasible.

EXTREMELY LOW ORBIT INSERTION

In addition to SpaceX designing and building very reliable satellites, we further mitigate risks by deploying the satellites into extremely low orbits relative to industry standards. We deploy our satellites into low altitudes (❤50km) and use our state-of-the-art electric propulsion thruster to boost the satellites to the operational altitude of approximately 550 km to start their mission. We leverage SpaceX’s technical advancements to maintain controlled flight at these low altitudes. By deploying the satellites into such low altitudes, in the rare case where any SpaceX satellite does not pass initial system checkouts, it is quickly and actively deorbited using its thruster or passively by atmospheric drag. This approach is not without complexity or other challenges. This was best evidenced by the recent February 3rd Starlink launch, after which increased drag from a geomagnetic storm resulted in the premature deorbit of 38 satellites. Despite such challenges, SpaceX firmly believes that a low insertion altitude is key for ensuring responsible space operations.

OPERATING BELOW 600 KM

SpaceX operates its satellites at an altitude below 600 km because of the reduced natural orbit decay time relative to those above 600 km. Starlink operates in “self-cleaning” orbits, meaning that non-maneuverable satellites and debris will lose altitude and deorbit due to atmospheric drag within 5 to 6 years, and often sooner, see Fig. 1. This greatly reduces the risk of persistent orbital debris, and vastly exceeds the FCC and international standard of 25 years (which we believe is outdated and should be reduced). Natural deorbit from altitudes higher than 600 km poses significantly higher orbital debris risk for many years at all lower orbital altitudes as the satellite or debris deorbits. Several other commercial satellite constellations are designed to operate above 1,000 km, where it requires hundreds of years for spacecraft to naturally deorbit if they fail prior to deorbit or are not deorbited by active debris removal, as in Fig. 1. SpaceX invested considerable effort and expense in developing satellites that would fly at these lower altitudes, including investment in sophisticated attitude and propulsion systems. SpaceX is hopeful active debris removal technology will be developed in the near term, but this technology does not currently exist.

TRANSPARENCY AND DATA SHARING

SpaceX transparently and continuously shares the details of our Starlink network both with governments and other satellite owners/operators. We work to ensure accurate, relevant, and up-to-date information related to space safety, and space situational awareness is shared with all operators. SpaceX shares high fidelity future position and velocity prediction data (ephemerides) for all SpaceX satellites.

COLLISION AVOIDANCE SYSTEM

SpaceX has high fidelity location and prediction data for our satellites from deployment through end-of-life disposal, and we share this information continuously with the U.S. Space Force, LeoLabs and other operators for tracking and collision avoidance screening. SpaceX satellites regularly downlink accurate orbital information from onboard GPS. We use this orbital information, combined with planned maneuvers, to accurately predict future ephemerides, which are uploaded to Space-Track.org three times per day. LeoLabs downloads our ephemerides from Space-Track.org and along with the U.S. Space Force’s 18th Space Control Squadron screens these trajectories against other satellites and debris to predict any potential conjunctions. Such conjunctions are communicated back to SpaceX and other satellite owners/operators as Conjunction Data Messages (CDMs), which include satellite state vectors, position uncertainties, maneuverability status, and the owner/operator information. SpaceX uploads these CDMs to applicable SpaceX satellites.

--

--

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store