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The Expanse | ‘CQB’ and the Brutal Science of a Space Battle

The Expanse won acclaim for its scientific accuracy and nowhere was this more brutally evident than the attack on MCRN Donnager in ‘CQB‘.

Warning: This article contains spoilers for The Expanse episode ‘CQB’ (S1, Ep4). Proceed with caution.

Space combat has always been tenuously portrayed in science fiction; often as if the ships were operating in atmosphere. This is partly due to the popularity of Star Wars, where X-Wings and TIE Fighters soar through space in quasi-Second World War dogfights. Whilst there have been notable exceptions, most spacecraft in science fiction appear to operate like aircraft. That was until The Expanse came along.

Thanks in part to the steady guidance of executive producer Naren Shankar (who has a Ph.D. in applied physics and electrical engineering), The Expanse quickly earned respect for its realistic portrayal of life in space. This was exemplified early in the second episode, ‘The Big Empty’ (S1, Ep2), where water spiraled due to the Coriolis effect from the space station’s artificial gravity, generated by rotation. Although the effect was only shown briefly, it demonstrated that life in space is radically different from living in gravity.

An animated gif of liquid leaving a decanter in a curved spiral.
Detective Miller (Thomas Jane) demonstrates the Coriolis effect on Ceres in The Expanse episode ‘The Big Empty’ (S1, Ep2). The station’s centrifugal forces allow the liquid to be poured, whilst the Coriolis force spins the liquid in the opposite direction to the station. | Syfy, 2015.

The Expanse episode ‘CQB’ (S1, Ep4) – military parlance meaning Close Quarter Battle – portrayed one of the most realistic space battles in science fiction. The survivors of the ice hauler Canterbury had been rescued by the Mars Congressional Republic Navy (MCRN) battleship Donnager, as an unidentified spacecraft approached.

The actions throughout the engagement were logical and made tactical sense.  As soon as Donnager detected their presence, the unidentified spacecraft jammed all communications, thus preventing the Donnager from calling for help. The unidentified craft then separated into six stealth ships and commenced their attack.

Missiles and Railguns in ‘CQB’

It is telling that The Expanse does not rely on energy weapons. Instead of lasers and ‘deadly’ bolts of light, every weapon is based on conventional technology, well within the scope of contemporary science.

When the stealth ships are closing with Donnager, they launch a volley of missiles. Donnager responds in kind. All of the missiles are passively ejected from their respective ships before the missiles’ drives ignite.

This mimics missiles launched from fighter jets, which are dropped prior to activation, to prevent aircraft spin. This concept is even more important in space, as an environment free of any atmospheric drag means that any type of propulsion will alter a ship’s trajectory.

Missiles are typically used for long-range engagements, as they can change course according to the target’s position. Additionally, given the lack of gravitational effects and the absence of atmosphere, any blast from a close-range missile in space would result in an ever-expanding debris field that could cripple both ships.

The other key weapons used in ‘CQB’ are the railguns. These are weapons that use electromagnetic forces to launch high-velocity projectiles. Rather than using an explosive warhead, railguns rely on high-velocity impacts to cause damage.

An animated gif of the MCRN Donnager firing its railgun and hitting one of the stealth craft.
MCRN Donnager fires its VX-12 Foehammer railgun in The Expanse episode ‘CQB’ (S1, Ep4). The first working model railgun was demonstrated as early as 1917 but has always struggled to overcome the enormous energy consumption that would be required. | Syfy, 2015.

Railguns require massive amounts of energy to enable the projectile to reach a sufficient velocity to be effective. When Donnager’s railguns are charging, non-essential systems go offline; lights dim and surveillance cameras stop working.

For creating these powerful magnetic fields, the railgun’s rails would need to contain a highly conductive material.  The best conductive element is silver, but it tarnishes easily and is therefore not ideal. Copper is also an excellent conductor of electricity and is widely used in electronics today. However, it is possible that a superconducting material would be used for this application, such as niobium-titanium or yttrium barium copper oxide (YBCO).

The rails of the railgun would need to withstand the forces of a rapidly accelerating projectile. The conductive material would also need to be cooled (by a significant amount if superconductors are used). This would present an interesting engineering challenge, as many common structural materials become brittle at low temperatures.

Railguns have been in development for over ten years, with an operational prototype proving they are feasible.  However, railguns have numerous engineering challenges. The parallel rails, or conductors, are subjected to massive electric currents and magnetic forces. A normal gun can be fired about 600 times before the barrel must be refurbished, but a railgun prototype was replaced after nearly two dozen shots.

A side effect of railguns is the massive amounts of heat generated. This can cause equipment to melt, as well as enable detection by enemy forces due to their thermal signature. Although the temperature of the region between Mars and Jupiter, where the battle takes place, is typically between -73 °C to -108 °C, it’s a perfectly insulating vacuum which means the immense heat being generated has no means by which it can naturally dissipate. It’s not directly addressed in the show, but James S.A. Corey’s novels reference liquid helium used to bleed off Rocinante’s excess heat.

Although a railgun was at one point to be mounted on one of the US Navy’s Zumwalt-class destroyers, real-world development of rail guns has currently stalled. Instead, research has shifted to hypervelocity projectiles. Liquid helium, meanwhile, has been used as a coolant for space flight and satellites since the 1980s.

Defensive Systems in ‘CQB’

Instead of relying on the science fiction staple of energy shields, the only defenses against missiles in The Expanse are armor plating, stealth systems, and point defense cannons (PDCs).

PDCs are similar to conventional close-in weapon systems (CIWS), which are point-defense systems for targeting incoming missiles and enemy aircraft at short range. The Phalanx System is a real-world example that is currently in use. It is essentially a 20mm Vulcan autocannon with computer targeting, enabling it to swiftly aim and fire at incoming missiles.

However, PDCs operate in space. The recoil caused by a rapid-fire burst from a CIWS will have little impact on a massive naval destroyer’s speed or direction. However, the same burst from a PDC would send a spacecraft into an uncontrolled spin. This is why, as Donnager’s PDCs fire, short bursts can be seen from the back of the PDC in time with the weapon’s fire, allowing them to compensate for the recoil.

MCRN Donnager’s point defense cannon in action in The Expanse episode ‘CQB’ (S1, Ep4). Point defense is not a fictional concept, and refers to a relatively short-ranged weapon charged with protecting a specific structure or vessel against air attack. | Syfy, 2015.

It is interesting to note how radar is used in The Expanse, as that remains one of the best ways to inform situational awareness by detecting objects. Radar works particularly well in space, as there are no objects to obstruct detection (such as mountains and tall buildings) and no atmospheric interference.

Stealth systems are likewise already in use today but are still in their infancy. The angular design and matte black finish of the attacking stealth ships echo the existing Lockheed F-117 Nighthawk stealth aircraft. Stealth aircraft are designed to limit their radar signature, as their skins are made from polymer-based materials that absorb radar. Since radar works by signals bouncing off objects and being returned to the emitter, anything that absorbs the radar signal will remain undetected.

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