Academics have started working on guidelines for war in outer space.

Space and legal experts from Australia, the UK and the United States are collaborating on a new project investigating how Earth-bound laws could be applied in times of armed conflict in space.

“Conflict in outer space is not a case of ‘if’ but ‘when’,” says Professor Melissa de Zwart, dean of law at the University of Adelaide.

“However, the legal regime that governs the use of force and actual armed conflict in outer space is currently very unclear,” she told the ABC.

Prof de Zwart is part of an international group working on the ‘Woomera Manual’ (PDF); a document intended to become the definitive text for applying on military and security law to space-based scenarios.

The document should be completed by 2020.

Space is already key to modern communications, surveillance, early warning, and navigation systems, and so will become a critical security and conflict domain.

“Such extensive use of space by military forces has produced a growing awareness that space-based assets are becoming particularly vulnerable to adverse actions by potential competitors,” says Professor Rob McLaughlin, an expert in military and security law.

In 2017, US secretary of the Air Force, Heather Wilson, declared America must prepare for armed conflict in outer space.

US President Donald Trump has called for a US military space force to be created.

“My new national strategy for space recognises that space is a war-fighting domain, just like the land, air and sea,” President Trump said in March.

“We have the Air Force, we'll have the space force.”

Former legal adviser to the Royal Australian Air Force, Duncan Blake, says early steps have already been taken.

“The Chinese tested an anti-satellite missile in 2007 against one of their own weather satellites — it caused a lot of space debris,” he told reporters.

“The Russians, they've tested an anti-satellite missile as well, and it's a capability that the US clearly possesses.”