Introduction

Space as a domain presents unique and powerful operational advantages. Orbital systems enable military forces unrivalled reach, persistence, endurance, observation, and responsiveness (United States Space Force, 2020). They are used extensively in modern military operations across the full spectrum of conflict.

Space systems are also uniquely vulnerable to attack, with spacecraft being far easier to destroy than defend. As the barriers of both access to space and the technological sophistication required to strike targets in orbit reduce, the Australian Defence Force (ADF) must consider the developing exoatmospheric threat picture, and how best to defend its assets in orbit.

Scope

Space capabilities extend their influence into every domain; similarly, threats to space systems manifest from within every domain. A cyberattack can inflict permanent damage on a satellite, ground-based lasers can blind them, and ground stations are vulnerable to physical intrusion or attack. This series; however, will focus specifically on direct kinetic threats to space-borne objects, by both state and non-state actors. These are, technically, the most difficult to achieve, and if executed, carry the highest potential cost and irreversibility.

How to prevent a war in space

Part one – holding the high ground

“Who controls low-Earth orbit controls near-Earth space. Who controls near-Earth space dominates Terra. Who dominates Terra determines the destiny of humankind.”
– Everett Dolman, Professor of Military Strategy, USAF ACSC

Background

Space utilisation is a significant force multiplier in modern military operations. The effects exerted within this domain are codified in ADF doctrine within the ADDP 3.18 Operational Employment of Space as “space enablers to terrestrial operations” (Australian Defence Force, 2016).

Orbiting surveillance satellites allow persistent and legal oversight of the most restricted locations on Earth. Satellite communications enable near-instantaneous information flow on a global scale. The Global Positioning System (GPS), one of multiple PNT (position, navigation, timing) constellations, provides military and civilian capabilities that have no viable terrestrial match. Every military function is enabled and enhanced by the unique capabilities space access provides; and the mass investment of intellectual and financial capital known collectively as the Second Space Age is likely to produce greater capability still (Harrison, et al., 2017).

Space systems are also vulnerable. No true protection for crewed or uncrewed spacecraft exists beyond the technological sophistication required to track and strike a target in orbit – a bar that is rapidly lowering. The space domain uniquely favours the offensive; it is an order of magnitude easier to disable a satellite than to defend one. There is no forward edge of the battle area behind which spacecraft can reconstitute, nor terrain to shield them. The ongoing revolution in access to space will rapidly reduce the financial and technological bar required to threaten objects in orbit, potentially leading to a proliferation of anti-satellite (ASAT) capabilities to a range of state and non-state actors (Hitchens, 2009).

Anti-Satellite Weapons

Space systems are used extensively across the whole spectrum of conflict, from small-unit grey-zone operations to major theatre war. The United States and its allies, including Australia, have a clear quantitative and qualitative lead in military space systems, and this asymmetry makes them an obvious target for an enemy to disrupt, degrade, or destroy in a conflict.

Existing space weapons are categorized as Earth-to-Space, Space-to-Space, and Space-to-Earth; then further as kinetic physical (K-ASAT), non-kinetic physical, electromagnetic, and cyber. Attacks are distinguished by their effect, including potential collateral or environmental damage, reversibility, and ability of the victim to attribute the source of the attack (Harrison, et al., 2020). A laser may temporarily dazzle a satellite, for example, or permanently blind it.

A co-orbital weapon may grab and de-orbit a target satellite, or it may blow it to pieces, generating a storm of hazardous space debris. Both state and non-state actors of varying levels of technological sophistication have demonstrated ASAT capabilities within one or more of these categorisations.

Kinetic Anti-Satellite Weapons

The primary example of Earth-to-Space ASAT weapons are K-ASAT direct-ascent missiles. These involve an air or ground-launched missile interdicting a satellite in orbit. To date, only the United States, Russia, China, and India have demonstrated K-ASAT capability; however, close technical similarities with more prolific anti-ballistic missile (ABM) systems mean even modestly armed states could possess a ‘turn-key’ K-ASAT capability. The United States’ RIM-161 SM-3, for example, is a surface-to-air ABM that was successfully tested against a satellite by modifying its sophisticated kinetic kill vehicle to target a satellite instead of an incoming missile warhead.

The complexity required to strike an orbiting target is high, increasing as a function of its altitude. To date, K-ASAT testing has only been prosecuted against targets in Low-Earth Orbit (LEO). Targets in medium or geocentric orbits require much larger multi-stage missiles resembling full-scale space launch vehicles, increasing both deployment times and the risk of these missiles being intercepted (Harrison, et al., 2017).

The key value of K-ASAT weapons is the assurance of their intended effect. For a military planner seeking to permanently neutralise a high-value space target, a successful K-ASAT strike would guarantee mission success; unlike lasers or other weapons, which can be hardened against or potentially recovered from, a kinetic impact guarantees mission success. As there is no free lunch in warfare, it also requires tolerating the risk of collateral damage to one’s own spacecraft.

Kinetic destruction of a satellite is a catastrophic and unpredictable event. K-ASAT tests have measured impacts at closing velocities of as high as 37,000km/h; three and a half times faster than the fastest confirmed hypersonic missile (Missile Defense Advocacy Alliance, 2022). Shrapnel scatters at extreme speeds in all directions from the impact area, spreading throughout the orbital path. Impacts with other satellites or junk could create a self-propagating cascade effect, known as Kessler Syndrome (Kessler & Cour-Palais, 1978), with the quantity of shrapnel and size of the threatened area increasing exponentially.

If the generation of new debris outpaces the orbital decay rate of the old debris, safe space operations would become impossible, with a long-lived ‘storm of steel’ presenting extreme hazard for any vehicle in orbit. While debris in LEO would decay relatively rapidly, debris in Medium Earth Orbit (MEO) – the domain of the militarily significant GPS constellation – could remain for as long as 200 years, and geocentric debris – the orbital height shared by geosynchronous communications and imaging satellites – could remain effectively permanently (Jenkin, et al., 2013). This indiscriminate effect endangers all satellites sharing the orbit, including that of the attacker. This has led to spacefaring actors seeking more discriminate and close-range methods to physically disable satellites, including the development of co-orbital ASATs.

Co-orbital ASATs

A co-orbital ASAT is a Space-to-Space weapon, a spacecraft designed to attack another spacecraft. These range from small, simple space ‘mines’ that intercept another satellite and destroy it with an explosive charge or collision, to electronic attack satellites equipped with lasers and radio frequency jammers, up to larger and more complicated satellites with robotic appendages that can physically manipulate or deorbit another satellite (Harrison, et al., 2020).

These weapons can be deployed alongside routine launches and remain silent in orbit indefinitely until triggered, minimising the time available to react to an attack. They are difficult to identify as weapons, potentially performing legitimate peacetime functions and unmasking themselves only when they manoeuvre to approach other satellites (Secure World Foundation, 2022). Such weapons were the chosen counterspace focus of the Soviet Union during the Cold War, with the Istrebel Sputnikov and Naryad programs, and live on today with the Russian Federation’s Burevestnik program and the People’s Republic of China’s (PRC’s) Shijian satellites.

Co-orbital satellites have all the great counterspace flavour with fewer calories. K-ASAT testing is universally condemned as gravely irresponsible, with any test drawing international attention and public anger (West, 2019). Co-orbital testing, meanwhile, is far easier to conceal. It is threatening in a nebulous, non-specific way. Satellites of the PRC’s Shijian fleet have been observed performing ‘rendezvous and proximity operations’ (RPO) with other satellites, such as close passes, docking, and towing (Burke, 2021).

To the military observer, the anti-satellite potential of such manoeuvres is obvious. For the tried-and-true geopolitical strategy of confusion and obfuscation; however, such activities can be – and, indeed, have been – explained away as responsible debris removal, inspections, and repair and refuelling operations (Pollpeter, et al., 2015). Co-orbital satellites can also be built as ‘dual-use’ spacecraft, performing routine and unremarkable space operations while awaiting the command to attack. The result is there is no way to know how many of these weapons are currently in orbit, although multiple candidates have been identified through observed RPO tests.

Defending against co-orbital satellites also presents a dilemma to a commander on the ground. The simplest countermeasure is to shoot them out of the sky once hostile intent is identified; but in doing so, the defender risks transforming the attacking satellite into that storm of space debris that places entire orbital paths at risk. Manoeuvring the threatened spacecraft away from an attacker is another option, but this assumes adequate advance warning, and sufficient propellant to both evade an attacker and return itself to a safe orbit (Wright, et al., 2005). This problem remains unresolved; as earlier noted, the defence of spacecraft has no ready solution.

Counterspace Proliferation

Anti-satellite weapons do not have to be unusually technically sophisticated. A normal satellite can, either through deliberate owner action or hijacking, be commanded to ram another satellite. It could also carry a small, non-sophisticated payload, such as steel pellets ejected by gas into the orbital path of another satellite (Canavan,1993). While military satellites conducting tests of RPO manoeuvres can be identified and tracked, a commercial satellite with such capabilities, deployed by a malicious non-state actor, may not be discovered until it is used. The rapid democratisation of space access enabled by the growth of the commercial space industry may likewise democratise the ability of malicious actors to target objects in space.

Conclusion

Part One of How to Prevent a War in Space has served as an introduction to the weapons that threaten military space platforms, and the potentially dire consequences of kinetic action in space. Part Two investigates the increasing, and under-looked potential for non-state actors to directly threaten space systems.