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The Expanse | 'CQB' - The Brutal Science of a Space Battle

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“Whoever they are, and whatever they’ve come to do, it’s just become a suicide mission.”

Captain Theresa Yao, ‘CQB’ – S1, Ep4

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 gracefully soar through space. 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 PhD in applied physics and electrical engineering), The Expanse quickly earned respect for its realistic portrayal of life in space. This was exemplified 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.

[See also: Podcast | Brad Wright’s Conversations in Sci-Fi With Naren Shankar]

The episode ‘CQB’ – S1, Ep4 – (which stands for 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.

Hostile Engagement

“Who would be insane enough to take on the Donnager in CQB?”

Alex Kamal, ‘CQB’ – S1, Ep4

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 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.

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 current 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. Fortunately for the MCRN, space is very cold. The temperature of the region between Mars and Jupiter, where the battle takes place, is typically between -73 °C to -108 °C, which would cool railguns and prolong their usability if mounted externally.  However, the radiating heat would increase their thermal signature, but by the time you’re firing a railgun, your secret’s out so perhaps it’s a moot point.

Although a railgun is planned to be mounted on one of the US Navy’s Zumwalt-class destroyers, real-world development of rail guns has currently stalled, as research has shifted to hypervelocity projectiles.  

Edit: Twitter user @ToughSF pointed out that whilst space is heckin’ cold, its effect on the heat generated by Donnager’s railgun would be the opposite:

Space is a perfectly insulating vacuum. The only way to get rid of heat is radiating it away, so those railgun rails would either become white-hot and melt before they get rid of their heat, or rely on heatsinks to dump it elsewhere.

We’re always happy to be challenged and corrected 🙂

Defence Systems

Yao: You look nervous.
Holden: I get that way when missiles are flying at me.
Yao: Don’t worry. It’s nothing our guns can’t handle.

‘CQB’ – S1, Ep4.

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 an 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 the Donnager’s PDCs fire, short bursts can be seen from the back of the PDC in time with the weapons fire, allowing them to compensate for the recoil.

Donnager’s point defense cannon in action. | 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 stealth ships echo the 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.

Electronic countermeasures (ECM) – jamming as it is more commonly known – is another form of stealth. Rather than passively absorbing radar, it overloads the sensors. Whilst this alerts the enemy to their presence, it also means that they are unable to accurately target them.

[See also: Marvel | So, You Want to Build an Iron Man Suit? by Peter Ray Allison]


Souther: We can’t tell who they’re fighting.  There’s massive LADAR and RADAR jamming, we can’t resolve the drive signatures or make any visual IDs.
Avasarala: They took our people hostage. We have to get a ship there.
Souther: The Orinoco’s en route at best possible speed, but they’re still two days out.

‘CQB’ – S1, Ep4.

The distance between Earth and Mars, our nearest planetary neighbor, is approximately 140 million miles on average, whilst the distance between Mars and Jupiter is approximately 342 million miles.

The vast distances between planetary bodies mean ambushes are difficult unless there is a convenient planet or moon to hide behind. Hence, most battles in space would take place over vast distances, rather than in close proximity. The nearest allied ship was said to be over two days away from Donnager.

Space is also an incredibly hostile environment. This is why one of the key factors in starship design is preserving a ship’s atmosphere. When a breach occurs, air will immediately rush out of the compartment, endangering the crew.

Donnager’s Command Information Centre (CIC), where Captain Theresa Yao (Jean Yoon) and her officers control the ship, is a compartment within a larger one. Critical ship functions are separated into self-sealing sections. If the hull is breached, this allows them to keep functioning even with large areas in a vacuum. Similar compartmentalization is used in modern submarine design, where sections of a vessel can be sealed using bulkheads in the event of a breach.

CIC aboard MCRN Donnager. | Syfy, 2015.

When railgun projectiles pierce Donnager’s hull, going straight through the cell where the survivors of the Canterbury are held, everything suddenly goes silent. As sound requires a medium through which to travel, when the cell is exposed to vacuum there will be no sound. Blood is seen to be flowing up and out through a hole in the hull.

However, the time required for the survivors to seal both holes appears to take longer than the time for which their blood would be oxygenated. They would have to exhale as soon as depressurization occurred, to prevent their lungs from bursting, which would further limit their oxygen. Any exposed fluids would also instantly vaporize, injuring their eyes and tongues, which was not shown.

Operating outside the atmosphere also presents several tactical issues. Rather than relying on aerofoils for flying, spacecraft use their core engines for propulsion and maneuvering thrusters for changing course. Aircraft can change direction using tail rudders and flaps. However, for a spaceship, the absence of atmosphere means that changing direction requires thrust. This is typically achieved using maneuvering thrusters, as in modern spacecraft.  Just as the main engines are used for launching, maneuvering thrusters rotate the spacecraft in the new direction, before the main engines are ignited again.

Cant’s medic comes between a railgun and its target. | Syfy, 2015.

There is no need for engines to be continuously active just to maintain speed, as there is almost no inertial drag in space, so spacecraft will continue traveling at the same speed. Acceleration could be used for artificial gravity, thereby mimicking the effects of gravity by accelerating at a constant 9.81m/s (the equivalent acceleration due to gravity). However, this is not a viable solution for traveling interplanetary distances.  Not only is it inefficient (constantly burning fuel), but a few months’ worth of acceleration would result in traveling at a significant fraction of the speed of light, which is where things become really strange. Instead, artificial gravity could be induced through axial rotation, akin to a von Braun wheel, or astronauts would just have to cope with zero-gravity for a while.

Zero-gravity is realistically portrayed throughout The Expanse, with objects floating if they are not held down.  At one point James Holden (Steven Strait) tethers himself to Naomi Nagata (Dominique Tipper), before pushing against her to propel himself to the catwalk, at which point he turns on his magnetic boots and reels in Nagata.

Echoes of the Past

“Their torps’ guidance systems are really good. Better than anything we ever simmed against. They’re pushing our PDCs to the limit.”

Comms Officer, ‘CQB’ – S1, Ep4.

It may seem odd that six frigates can attack a battleship, even with their stealth systems, but it is not without historical precedent. In 1967, the aging Second World War-era Israeli destroyer INS Eilat – 362.7 ft long, 1,710-ton water displacement, with a crew of 187, nine guns, and eight torpedo tubes – was sunk by two significantly smaller but more sophisticated Egyptian Komar-class missile boats – 83.4 ft long, 66.5-ton water displacement, a crew of 17, two guns, and two missile launchers – using the latest Soviet-made P-15 Termit anti-ship missiles.

In the Falklands War of 1982, the otherwise superior British Royal Navy proved equally vulnerable to the most sophisticated missiles of their generation when French-made AM39 Exocet anti-ship missiles fired from the air sank the destroyer HMS Sheffield and transport ship SS Atlantic Conveyor.

Yao’s comment that “The only combat most of my officers have seen is in simulators,” echoes military training at the height of the Cold War. During this time there were endless military exercises combined with a technological arms race, but most soldiers rarely had real-world combat experience.

Self-destruct systems are a classic science-fiction trope, but scuttling remains a viable tactic to prevent a vessel from falling into enemy hands (or for more benign purposes, like creating an artificial reef.) There’s no self-destruct button, however, and the process requires explosives to be placed at vital points in the ship’s superstructure to ensure it takes its secrets to the seabed.

[See also: Dune | Flap Battle – A History of Ornithopters on Screen by Clint Worthington]

Science in the Story

“I didn’t think we could lose.”

Captain Theresa Yao, ‘CQB’ – S1, Ep4.

The Expanse’s adherence to realism has proved that excellent storytelling does not have to compromise the laws of physics.  This has been exemplified in ‘CQB’, which presented one of the most realistic portrayals of space combat.  There were no lasers or shields, just missiles and projectile weaponry in the harsh environment of space.

Embedding science in the story also presents further opportunities for rich storytelling.  When a ship is hit, rather than impacts being absorbed by ‘shields’, the crew are forced to deal with hull breaches, further adding to the drama of the moment.

Suddenly, enlisting in the US Space Force seems a lot less fun…

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After ten years designing drainage systems, Peter Ray Allison finally realized sewers were full of crap. Rather than having a midlife crisis, he became a freelance journalist specializing in technology and science fiction and was once called a ‘blessed geek’ by Virginia Hey. Peter’s work has been published by the BBC, The Guardian, and The Independent, amongst others. Peter is also a regular podcaster for Geek Pride.

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