The Space Debris Hazard

1. The Legal Implications of Improved Space Situation Awareness and other Developments in Space TechnologyDr Stuart Eves, SSTL

2. The Space Debris Hazard • Total mass of debris in Earth orbit is currently ~6,800 tonnes • Close conjunctions occur frequently • The OneWeb mega-constellation will operate at 1200 km altitude specifically to avoid the debris in Low Earth Orbit (LEO) • Satellites should deorbit within 25 years >20,000 debris objects larger than 10 cm in Earth orbit Debris vs altitude OneWeb constellation TDS-1 before and after drag-sail deployment

3. Improved Space Situation Awareness • The new US Space Fence will detect smaller objects down to <5cm (perhaps 500,000) • It will provide improved cueing for high accuracy sensors • Better STC requires routine recording of ballistic coefficient, albedo, radar cross section etc. • Also, spectral sensors are required to determine the material composition of the debris • And we will also need sensors capable of observing object motion • Encouragingly, commercial SSA is developing Space fence coverage Commercial STC entities

4. Debris Removal • A variety of technologies, including Mass drivers; Adhesives; Harpoons; Lasers; Tethers; Nets; Grapplers; Propulsion plumes; Slingsats; and De-orbit sails have been suggested to remove large, long-lived debris objects • All these concepts are technically immature and look like anti-satellite weapons in the wrong hands • It’s unclear how these concepts would be financed, and the politics is hard too Harpoon concept Mass driver concept Adhesive concept Propulsion plume concept Laser concept Tether concept Grappler concept Net concept Slingsat concept De-orbit sail concept

5. Space Debris As Fuel • But supposing that we could use space debris as a propellant…….. • A team in Australia is developing a thruster that works by ionising metals (and carbon) and accelerating them • Mass-drivers have also been suggested, which can utilise almost any type of debris • Space debris becomes an on-orbit resource • Space Traffic Control (STC) data on the location of suitable pieces of debris suddenly increases in value Electric propulsion concept Mass-driver concept

6. Necropolis Concept • Technical Requirements: • Trackable and manoeuvrable • Serviceable – the Necropolis will need fuel • Able to manage charging • Able to passivate satellites arriving • Able to process materials delivered to it Satellite Disposal Facility in Orbit • Benefits: • Significantly less satellite de-orbit propellant • Lighter constellations – fewer rockets required • Less risky constellation disposal • Potential for refuelling subsequent missions using recycled materials • Metals and/or carbon

7. Legal Implications • Need agreement that disposing of satellites in an approved necropolis is both “legal” and a “responsible use of space” • Need agreement on the legal status of “unclaimed” debris • Need agreement on whether “owned” debris can be salvaged and traded • Need consensus on the potential transfer of legal responsibility if debris objects are “salvaged” Space Salvage

8. Thank You