The plan for a Golden Dome missile defence system in the United States looks technologically feasible but nonetheless raises doubts around factors such as its strategic benefits and affordability.

The program, which US President Donald Trump announced on 20 May, nonetheless may be attractive to US allies, including Australia, as building it could demonstrate to Washington the continued benefits of strategic partnerships. Australia and other allies may also directly benefit from welcoming and participating in the program.

There is little doubt that the world is going through a period of heightened international conflict, and nuclear deterrence has traditionally helped to prevent great powers getting into shooting wars with each other. But this deterrence is increasingly uncertain due to a rapid growth in some countries’ nuclear arsenals as well as a near-total lack of effort on nuclear arms control and in associated areas of global governance, such as outer space. Defensive measures are looking increasingly important.

The Golden Dome idea is not new. A week after Trump took office, he spoke about the urgent need to develop and deploy an effective missile defence shield. He referred to Ronald Reagan’s efforts to prevent nuclear attacks in the 1980s and to George W Bush’s push for a defence shield against threats from rogue nations and from accidental or unauthorised missile launches by others. But he also noted the limitations of defences, highlighting that those plans had never taken off and could provide only limited homeland missile defence.

While they build on previous efforts, Trump’s plans appear to focus on developing a shield against a broader range of threats. These include ballistic, hypersonic and advanced cruise missiles, as well as other next-generation aerial attacks from peer, near-peer and rogue adversaries. According to a White House statement, Trump’s missile defence system will also include ‘development and deployment of capabilities to defeat missile attacks prior to launch and in the boost phase’, suggesting that the US may even be leaning towards pre-emptive strikes.

However, the plan’s push to develop space-based missile defence architecture, including space-based interceptors that can intercept ballistic missiles in their boost phase, could trigger accelerated weaponisation of space. Russia and China have already begun weaponising outer space and are likely to use the US’s plans to further justify their efforts.

This won’t be the only challenge. The US administration has reportedly allocated $25 billion for the Golden Dome in the upcoming federal budget, which will come up for approval in the Congress in the coming weeks. The Congressional Budget Office expects that ‘deploying and operating just the space-based interceptors’ will cost anywhere from $161 billion to $542 billion over the next 20 years. Trump said it would cost $175 billion, though he provided no detail on the figure. Knowing how much developing technologies and new programs can cost, we should assume that the actual cost of the program will be much higher.

The question of cost should nonetheless be kept in context: if China and Russia take the lead in this area, the consequences for the US and its allies will be worse than any monetary cost. However, finances are finite, and there are other needs for precious defence dollars. For example, if the Golden Dome will come at the expense of US commitments and deployments in the Indo-Pacific, it will have potentially negative consequences for the region.

Set against these costs are the potential benefits of such a program. For one, it will indicate that the US and its allies are finally waking up to the challenge of Russia’s and China’s creeping weaponisation of space. Until now, the only response has been lackadaisical discussions under various United Nations forums that have led to no results, as existing space governance mechanisms slowly dissolve. The Golden Dome program will not only allow the US and the West to catch up; it may also generate some momentum for space governance talks as China and Russia grow increasingly threatened.

The program could also lead to a new era of technological investment and development. China has been catching up to, and in some cases overtaking, the US and the West technologically. This doesn’t bode well for international peace and security, considering that China is a revisionist power that is seemingly willing to use force. Moreover, technologically advanced countries such as Australia can benefit from this wave of progress if they participate in the program.

The program will also afford US allies an opportunity to demonstrate to the US the necessity of having partners and allies across the world. In addition to technological cooperation, the Golden Dome system will likely require partners to provide ground facilities within their territories. Both Canada and Australia host important US early warning and space support sites. The Golden Dome system will require further and deeper cooperation, which will help integrate the US with its allies. The program may therefore force Trump and his followers to recognise that the US cannot defend itself on its own: it relies on support from international partners.