Renewable energy generation is not as robust in the face of enemy attack as it looks. Nuclear power, even though it would probably be concentrated in a few large generating stations, should in fact be a little more dependable in wartime.

This warrants careful consideration, because an enemy may choose incapacitation of electricity supply to pressure Australia into cease fighting, just as Russia has repeatedly attacked Ukraine’s power generation and distribution system.

Yes, solar and wind electricity generation is dispersed into many units of modest output, each relatively uneconomical to attack, as Chris Douglas points out in an article in The Strategist. But supply-firming installations, such as batteries and peak-demand generators, are not as numerous and can be targeted instead. Moreover, renewable generation is just as reliant on a limited number of key transmission lines and substations in the distribution grid as big power stations are.

Also, whether an enemy would take the huge step of attacking nuclear power stations is doubtful.

How easily an enemy could cripple electricity supply can be analysed in terms of the criticality of points in the system, their vulnerability and their recuperability.

Consider a hypothetical but plausible case in which seven nuclear power stations have a combined capacity of 11 gigawatts. Each is critical, because losing its output would cause great economic disruption. But the same applies to supply-firming installations that back up renewables. Australia’s eight largest planned firming installations have a capacity of about 11 gigawatts, so the concentration of supply in critical assets is quite comparable in the nuclear-generation and renewables-generation scenarios.

As for vulnerability, concentration of generation capacity in nuclear stations would simplify protection with air and missile defences. In the all-renewables scenario, defences would instead cover the largest firming assets, but we would have to accept risk with the remainder.

If an enemy overcomes air and missile defences and scores hits, nuclear power stations may actually be less vulnerable than the equivalent firming assets, because they are necessarily built with impressive, passive defensive and protection measures. To achieve a high probability of kill our adversary would likely need to increase the volume or yield of the missile attack.

Now, penetration of the containment building is likely to knock out the station out regardless of damage to the reactor, because cooling systems, heat exchangers or condensers will likely be damaged. But a catastrophic release of radiation is less likely. And in fact the more vulnerable part of the station is the adjacent turbine hall. But it would be no more vulnerable than firming installations—gas or hydro power stations or large lithium batteries.

Then there’s the question of recuperability—how quickly installations can be brought back on line after damage. In the nuclear-generation scenario, reactor damage would be catastrophic and take months to years to recuperate. But, as noted above, it would be improbable, and the more likely problem would be damage to ancillary systems, turbines or the station’s transformers. They could be fixed or replaced in about as much time as the turbines or transformers of firming installations could be, and possibly faster than an array of large lithium batteries. Note that replacing ancillary systems, turbines and transformers would not be far from current Australian manufacturing capabilities.

So, in both nuclear-generation and renewable-generation scenarios there is risk in concentrated sources of electricity, but on balance the nuclear set-up is not appreciably worse and may even be better.

Regardless of the means of generation, the main vulnerability is in the distribution network. While renewable generation assets are numerous, they are also functionally useless in isolation: the system works only if networked together so that when the sun isn’t shining in Queensland, for example, the South Australian wind can take up the slack.

There are about 305 substations across the National Electricity Market, and destruction or disablement of only the four main interconnector transmission lines is likely sufficient to splinter the system. Destruction of only eight substations is likely to isolate the main generating regions from the capital cities, regardless of how much renewable capacity there is.

Substations, being compact and not particularly robust, are also much more vulnerable to attack. Vulnerability will rise in the renewable-generation scenario. Because renewables capacity is often built far from demand, the distribution grid grows, increasing the area to be protected, and relying more on internet enabled control systems. This increases vulnerability to additional attack vectors, including cyber and sabotage. The protection against this may be far more draining on limited national capabilities.

The distribution network would be relatively recuperable, because replacing a transformer is a simpler task than repairing a turbine or pressure vessel. US experience tells us that the job typically takes eight to 35 days. But the sheer ease of re-attack and quantity of targets may exhaust our stock of repair or replacement components quickly. Similarly, trying to protect each node with surface-to-air systems would exhaust our available forces.

Lastly, it should be pointed out that targeting nuclear power stations has been deliberately avoided by both sides in the Ukraine war, and it is beyond dispute that attacks on nuclear facilities in any conflict would be regarded as escalatory. While non-binding common practice should not be used as a mitigation in its own right, it adds a degree of complication to the enemy assessment.

Nuclear power stations may actually be the safest, and most defendable part of the electrical system.

There’s renewed interest of late in the US Navy’s electromagnetic railgun. Plans to perform at-sea weapon testing appear to have been delayed in favour of further research. So, while development will probably continue, there are still two major problems holding the railgun back. The first is meeting the weapon’s massive power requirements at sea. The second is demonstrating that it’ll be ‘better’ than existing weapons.

The railgun launches rounds using electromagnetic force rather than explosive propellant. The USN prototype has 100MJ of pulse-power capacitors and a 25MW powerplant for recharging. The capacitors release their stored charge into the railgun barrel in a hundredth of a second, accelerating the projectile to about Mach 6. The USN’s goal is to fire ten rounds per minute, so the capacitors need to be recharged to fire every 6 seconds.

Few warships have the spare electrical capacity the weapon requires. The strongest candidate is the USN’s Zumwalt-class destroyer, whose 78MW integrated power system can dynamically distribute power between propulsion and on-board systems. It should have about 58MW of reserve power while steaming at 20 knots. By comparison, the Arleigh Burke-class destroyer has only 7.5MW for on-board systems.

The USN previously had several nuclear-powered cruisers, but the last were decommissioned in the 1990s. A new class of nuclear-powered warships could host multiple railguns (or other power-hungry weapons). But before the USN commits the kind of money required, it has to prove that the weapon is worth the investment.

There are three main roles envisaged for the railgun. The first is naval surface fire support—essentially artillery support for land operations. The Zumwalt’s 155mm Advanced Gun System (AGS) is also optimised for this role, using the rocket-assisted long-range land attack projectile (LRLAP).

The LRLAP is almost ten times the cost of a railgun hypervelocity projectile (HVP), but doesn’t match the railgun’s expected range. The HVP can also be made compatible with both the AGS and the 5-inch guns on USN’s cruisers and destroyers. Table 1 shows the estimated outcomes of this effort, although it doesn’t take into account the terminal effect of the munitions.

Table 1: Comparison of possible naval gun combinations

Gun system	Ammunition	$US per round	Range (km)	Rounds/min.
AGS	LRLAP	400,000	116	10
AGS	HVP	50,000	74	10
5-inch	Conventional	2,000	24	20
5-inch	HVP	50,000	74	20
Railgun	HVP	50,000	185	10

Sources: US Navy Budget 2017 and CRS report: Navy Lasers, Railgun, and Hypervelocity Projectile

The HVP is a 10kg kinetic energy round, which means that the damage it does depends on its impact speed. A Tomahawk land-attack cruise missile packs a 450kg high explosive warhead, has a range in excess of 1,500km and costs about US$1.1m apiece. The USN has plenty of Tomahawks and efforts are underway to make them anti-ship capable. As well, the USN’s new-generation anti-ship cruise missile (LRASM) is stealthier than a Tomahawk, has a ship-penetrating warhead, and still has a range in excess of 900km.

That’s bad news for the railgun, since its second envisaged role is as an anti-ship weapon. The railgun’s range is only useful in anti-surface warfare insofar as it can actually hit a moving target, and the HVP needs to hit with sufficient kinetic energy to do real damage. By comparison, a single LRASM is probably enough to at least mission kill most targets.

If hitting a moving ship wasn’t tricky enough, the USN is also hoping that the railgun will be able to defensively shoot down anti-ship missiles. The USN has surface-to-air missiles capable of intercepting both anti-ship cruise missiles (using SM-2 and SM-6) and ballistic missiles (SM-6 and SM-3). Closer in, the ESSM protects against missiles and aircraft within 50km, and the Phalanx Gatling gun is a close-range weapon of last resort (possibly augmented by lasers in the future).

Even if the railgun is capable of fulfilling this third role, it’ll probably be as a mid-tier weapon after SAMs. And a new project called the Hypervelocity Gun Weapon System [paywalled] is investigating the possibility that even 5-inch cannons will be able to shoot down missiles using the HVP. By the time the railgun is actually operational, it might be less of a game changer and more of an incremental upgrade.

Railgun technology could also be adapted to other purposes. For example, the electromagnetic launch system being installed in the next generation aircraft carrier operates on the same principle—it’s just bigger and slower. Perhaps an electromagnetic missile launcher could combine the launch speed of railguns with the range and accuracy of missiles.

The railgun’s prohibitive power requirements and stiff capability competition from missiles make it difficult to justify integrating it onto existing warships. If further development shows that it can perform better than existing naval weapons, USN will probably accelerate its operationalisation. But based on currently available information, it’ll probably be quite a while before we see an operational navy railgun.