This article is the third in a three-part series on How to Prevent a War in Space. Part One presented a primer on military space capabilities, and the state-level weapons that threaten them. Part Two investigated non-state kinetic threats, such as the risk of extremist or criminal groups putting a satellite into orbit. Finally, Part Three discusses the concept of deterrence, and how it could be applied to the defence of ADF spacecraft.

“A world of routine interference with satellites would be extremely unstable. By limiting insight into the actions of competitors, such interference would open the door to dangerous arms races, increase the risk of misperception, and provide strong incentives to strike an enemy first.”
– M. Markley, J. Pearl, B. Bahney – How Satellites Can Save Arms Control, Foreign Affairs, 05 August 2020

Deterrence in a Nutshell

A strategy of deterrence should be pursued as the most effective method of safeguarding ADF’s space assets. Deterrence, in a nutshell, is the art of convincing an enemy that the costs associated with an action outweigh the potential benefit. The variables of this equation are the payoff gained by a given action, and the level of risk or punishment an actor must accept in turn.

Different methods of deterrence target each variable. Deterrence by denial, which seeks to reduce an action’s payoff value to an adversary, can be achieved in space by increasing the survivability of space capabilities, or by convincing an adversary that military operations can persist without space support. Deterrence by retaliation, meanwhile, threatens unacceptable cost as punishment for action (Koplow, 2020).

Both methods are not equally applicable to Australia’s defensive posture. The capability gap in space systems overwhelmingly favours the US and its allies. This diminishes the credibility of threats to accept a retaliatory, tit-for-tat war in space; one side simply has more to lose. Australia also has no kinetic anti-satellite weapons of its own, nor should it pursue them; declaring an intent to acquire ASATs would escalate geopolitical tension and could create incentives for aggressive behaviour (Steer, 2022).

Deterrence by denial, meanwhile, is a non-escalatory method – able to be actioned at the national level – increasing the capability, security, and economic viability of space systems and the holistic capability of the ADF.

This article gives a brief history of deterrence in space and evaluate deterrence by denial as a defensive strategy for Australia’s growing space presence.

Thinking about Counterforce

Spacecraft and the weapons to kill them evolved together. Sputnik 1 became the Earth’s first artificial satellite in October 1957. The United States tested its first rudimentary anti-satellite missile, the Bold Orion, in May 1958, barely seven months later. The development of the Soviet Kontakt K-ASAT system and Naryad co-orbital program in the 1980s coincided with the development of the US Space Shuttle, which itself the Soviets suspected of being a space weapon (Podvig, 2017). It wasn’t a lack of technical capability that prevented the battlefield use of anti-satellite weapons. It was instead the risk of triggering nuclear war.

Around 70% of all satellites launched from Sputnik’s launch to the end of the Cold War in 1991 were military satellites, all built anticipating superpower conflict (Harrison, et al., 2017). These satellites maintained the delicate nuclear balance by enabling persistent observation of each side’s stockpiles, reporting the thermal signature of rocket engines and the distinctive ‘double flash’ of above-ground nuclear tests. They also would have, had the Cold War gone hot, have provided the earliest possible warning of hostile intercontinental ballistic missile launches and maintained persistent C4ISR structures during a general nuclear war. These systems provided the mutual transparency that set the foundation for more ambitious arms limitation agreements (Markey, et al., 2020).

If a state was to initiate a nuclear strike against another nuclear-armed nation, it would employ a ‘counterforce’ strategy, seeking to destroy as much of the others’ arsenal as possible to limit the damage of the inevitable countervalue (anti-city) retaliation (Builder, 1978). The success of a counterforce strike relies on the strategic principle of surprise, minimising the time an adversary has to respond to a pre-emptive strike. By identifying a hostile nuclear launch as it occurred, a forewarned victim could release a retaliatory second strike before the first strike hit, eliminating the value of a pre-emptive attack. Early-warning satellites, such as the US Defense Support Program and Soviet Oko constellation, formed the backbone of the anti-first-strike capabilities of both superpowers.

It followed in the minds of nuclear strategists, who spent their entire careers immersed in the use and counter-use of nuclear weapons, that the destruction of military satellites could only be a preliminary action to general thermonuclear war (Parlikowski, et al., 2012). Testing of anti-satellite weaponry was, therefore, intimately tied to the threat of first-strike preparations. Non-interference with satellites therefore became a key principle of the Strategic Arms Limitation Talks (SALT) and the Anti-Ballistic Missile Treaty and it has formed a component of every major arms agreement since (Markey, et al., 2020). The same deterrence that prevented the Cold War from going nuclear also prevented war in space.

Shielding satellites under the nuclear umbrella is no longer feasible. Military satellites once dedicated to nuclear missions now see routine use in conventional warfighting, eating away at the protection they have enjoyed since 1957 (Harrison, et al., 2017). Despite the military’s increasing reliance on space support, no viable method to defend satellites from physical threats yet exists, while the weapons that threaten them become ever more capable and proliferated. The only feasible way to protect spacecraft continues to be ensuring they are not attacked in the first place. The principle of non-interference should continue outside of nuclear agreements. But as during the Cold War, non-interference must be built on a foundation of deterrence.

Denial by Dispersion

A strategy of deterrence-by-denial in space can be implemented with three key actions.

First is the decentralisation and dispersion of space support capabilities across multiple systems and orbits, making individual satellites harder to attack and ensuring a given capability can persist under enemy action. A key space capability is position, navigation, and timing (PNT) data. This data, which the ADF draws primarily from the Global Positioning System (GPS), sees military application across all services: navigation, blue-dot tracking, communications, precision-guided weapons, search and rescue, drones, and countless others.

The space component of GPS is a constellation of 31 large satellites in Medium-Earth Orbit (MEO). Virtually every conversation about anti-satellite warfare begins with the destruction of the GPS constellation, leading to great military interest in ensuring PNT continuity in a future conflict. Using existing communications constellations in Low-Earth Orbit (LEO) as a GPS substitute has shown early promise (Khalife, et al., 2022). A layered, multi-orbital architecture can confer additional benefits; PNT satellites orbiting at lower altitude deliver a stronger downlink signal, making them harder to jam or spoof. They do, however, experience faster rates of orbital decay, shortening operational lifespan and creating the impetus to regularly upgrade aging hardware. Satellites in MEO, meanwhile, orbiting some 50 times more distant, are much harder to attack from the Earth. The advantages of each orbit cover the shortfalls of the other.

Destroying another nation’s spacecraft would be a highly escalatory event and needs to present a correspondingly high payoff for an aggressor to consider it a worthwhile action. A layered, multi-orbital regime increases the resilience and utility of a space system while reducing the individual payoff value of each satellite (Raytheon Intelligence & Space, 2021). This impacts the risk/reward calculations of an adversary, who is forced to commit greater resources to an effective space attack. It can also effectively deter space aggression by non-state actors by denying them a target of sufficient commercial value to extract a worthwhile reward. The use of large numbers of smaller, cheaper satellites would also aid in rapid reconstitution of a constellation under attack.

Denial by Reconstitution

The second action is to develop the ability to rapidly restore space capabilities lost in a conflict. Current military satellites are highly capable, complex, and staggeringly expensive. WGS-10, the latest in the Wideband Global SATCOM military communications network, cost $USD 424 million and took seven years to fly (SpaceNews, 2019). Large, bespoke satellites derive little benefit from economies of scale; it would cost at least the same half billion to replace WGS-10 if it were lost, and more if it were needed quickly. This has prompted the U.S Space Force to pursue a program of ‘operational responsive launch’; a system combining modular off-the-shelf satellites, rapid turnaround launch vehicles, and efficient processes that tie them together (Vasen, 2018).

Commercial space providers are actively developing responsive launch programs to fill military demand (Rocket Lab, 2022). By combining domestic production of satellites with local launch capabilities, the time and cost required to replace satellites lost in a future conflict can be compressed, making them less attractive targets (Beaumont, 2020).

Decreasing the payoff value of space targets by minimising the window of advantage derived from destroying military satellites could tip an enemy’s risk/reward calculations into unprofitable. It would also further reduce the commercial value of individual satellites, reducing the potential reward for a non-state actor.

Denial by Devaluation

The third action is to demonstrate the ability to maintain military operations without space support. THe ADF's space support currently enjoyed on operations is not assured in a future major conflict. Terrestrial alternatives to space functions have become increasingly feasible due to advances in computing and sensors. Ground-based PNT systems as a GPS substitute have already seen small-scale field testing (Lee, 2017). Persistent high-altitude UAS fleets can compensate for space-based ISR and communications systems, and are in active development for military application (Airbus, 2022). Aggressive pursuit of terrestrial alternatives to space support functions decreases the battlefield advantage an enemy could gain from attacking space systems.

Fusing these three actions into a holistic strategy of deterrence by denial would increase the resilience, utility, and economic efficiency of space support systems while making them less attractive targets.

All the Above Could Be Wrong

Deterrence is not a magic bullet. There are strategically significant differences in how different actors perceive aggression in the space domain. If a conflict between spacefaring nations appears inevitable, an adversary may conclude that the strategic, psychological, or political shock of a pre-emptive strike to space systems is advantageous. Chinese People’s Liberation Army (PLA) reporting demonstrates an organisational belief that space supremacy is an essential condition for military operations, that denial of space support is required to create overmatch against a near-peer adversary, and that war in space is thus inevitable (Stone, 2016).

PLA Air Force publications argue that limited K-ASAT strikes on US satellites would be a “de-escalatory and stabilising action in a naval encounter” (Zenko, 2014). The US, which has little respect for ‘escalate-to-deescalate’ strategies, would likely consider an attack on its space systems a highly escalatory action. This gap in thinking on space could lead to inadvertent escalation in a future conflict between spacefaring powers.

Deterrence-by-denial treats this risk by dispersal of space capabilities into layered multi-orbital structures and maintaining the ability to rapidly replenish them if lost. This forces an enemy to commit more resources to an effective space strike, lessening the appetite to strike space targets at lower levels of the conflict spectrum. It would also provide the deterrent foundation, without undue escalation, to pursue mutual non-interference agreements – establishing a shared code of conduct for space behaviour in a future conflict. While far from bulletproof, this is the best path today to prevent a war in space.


This series has provided an overview of current destructive counterspace weapons in national arsenals, and the methods and motivations for non-state actors to attack spacecraft. It has also argued the merits of a deterrence strategy to prevent a war in space.

As space-based systems become more ingrained in modern military operations, the ADF must remain cognisant of current and future threats to space assets. While attention is heavily directed to the counterspace operations of other military powers, the potentially graver risks posed by terrorist and criminal activity in space must also be considered. A strategy of deterrence by denial is a suitable and achievable policy for Australia as it builds its national presence in space, presenting an effective and non-escalatory method to deter both state and non-state actions against ADF spacecraft.