Hunters in the Great Dark, Part 1: A Hard-Science Look at Deep-Space Warfare

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Paul Lucas

Issue: 6 June 2005

According to popular movie lore, George Lucas modeled many of his on-screen battles in Star Wars on World War Two film footage. X-wing Fighters swoop through space in tight formation and dive-bomb, gigantic capital ships sluggishly exchange broadsides, and the enemy is engaged only at naked-eye distances.

This makes for wonderfully fun images in a classic popcorn fantasy. But how accurately does this model reflect the probable shape of future space warfare?

Judging by such factors as the evolution of modern weapon systems, the harsh realities of space as an environment, and the foreseeable capabilities of space travel, the Star Wars model looks to be, well . . . dead wrong.

In this two-part article we'll take a more realistic, hard-science approach to what it will take to fight and win a battle in deep space, away from planetary bodies. Part One deals with the environment of space and combat strategies necessary to succeed in it. Part Two, appearing in next week's Strange Horizons, will address offensive and defensive weapon systems.

A Note On Technical Assumptions

This article assumes a level of technology for our hypothetical combatants consistent with that needed for commonplace deep-space travel. This is pretty much the technological level of a "typical" space opera civilization minus the technologies without a solid theoretical basis in real science. The tactical impact of fanciful technologies such as faster-than-light travel, force screens, reactionless drives, etc., won't be discussed here. However, more hard-science speculative devices, such as fusion rockets, X-ray lasers, and near-sentient artificial intelligence, will be assumed to be routine for such cultures.

Space: The Ultimate Wilderness

Space is vast. Just how vast is hard for us humans to visualize intuitively. We can crunch the numbers, bandy about terms like astronomical units and light years, but our limited analog brains have a hard time really comprehending the scale of space. We're just not evolved for that kind of mental imaging.

Here's a little exercise that might help. Take a tiny bit of paper and tear and roll it until it's about the size of the period at the end of this sentence. This represents our solar system. Stand in the middle of a hallway or a gymnasium and hold it up. Now have a friend take a similar piece of paper and hold it up about 11 meters (about 35 feet) away. This represents Proxima Centauri, the nearest star to our own, 4.2 light years away.

Now imagine the hallway or gym is completely empty except for the tiny bits of paper—no furniture, no fixtures, no one holding them up, just the floating bits of paper. That's what space is: an enormous volume of nothing, dozens of cubic light years of near-absolute emptiness surrounding us in every direction.

Even within the solar system, the scale of things is still hard to visualize. Putting Earth and Mars on the same period-sized scale as above, the planets would never be closer than about four meters at closest approach. And between the tiny speck that contains everyone we know and love and the other tiny speck we occasionally send robots to, there is nothing but billions of cubic miles of empty void.

All this space provides the perfect hiding spot for even the most gigantic of ships seen in our favorite galaxy-spanning space operas. Even a vessel kilometers across would simply be swallowed up in the sheer immensity of the nothingness out there, like a microbe in an ocean.

This brings us to the first, and most vital, consideration for deep-space combat: finding the enemy.

Dust Motes In The Infinite

You have to know where to shoot before you can launch an attack. This is one of the great truisms of warfare throughout history. The most powerful weapons ever developed mean absolutely nothing unless you know where to aim them.

In the void, finding an enemy that wants to hide can prove very difficult. It doesn't matter if we're talking about a single ship or a fleet of thousands; against the scale of space, both are equally insignificant in size. Think of how modern astronomers struggle to detect objects even kilometers across in our own solar system: over many nights of observations, poring over data by hand or by computer, looking for small glitches against the background stars that might point to movement. Now imagine trying to find something that size or smaller that's trying its best to hide, and having to find it as quickly as possible before it kills you.

To make matters worse, while you're trying to find your foe, he's trying to find you. Obviously, the side that finds its target first while remaining hidden itself will gain a great tactical advantage over the other. This is why sensors and intelligence are so important in this theater of warfare, even more so than in the traditional battlefield. If all else is equal, a ship with mediocre weapons and highly advanced sensors is more likely to emerge victorious against a ship with insanely powerful weapons and primitive sensors. Battles in deep space will most likely feel like a cat-and-mouse game, where both sides hunt for each other across the immense nothingness while at the same time attempting to stay hidden. Passive sensing systems, like thermal scanners, broad-spectrum electromagnetic sensors, neutrino detectors, and mass detectors would sweep through slice after slice of the Great Dark, looking for anomalies that could point to an enemy ship. Active sensors such as radar and lidar may only be used when a ship has already been revealed and it has nothing more to gain by continued stealth.

Complicating this is the fact that while space is mostly devoid of matter, it is seething with radiation. While the enemy ship will most likely be emitting heat and electromagnetic radiation, the main trick is distinguishing its signature from the background. Ships may try to cloak themselves further by blocking or masking their radiative signatures. So forget about space warships gleaming with silvery hulls and bristling with big pointy guns; space-borne battlecraft will more likely be matte black and have oblique-angled hulls to deflect radar and other active sensors—all the better to blend into the void.

A historic parallel to this type of conflict does exist: submarine warfare. In fact, many scenes in submarine movies that show the action on the bridge—many sensor operators working in close clusters, calling out new contacts and status reports—can easily be reimagined as the reality on a spacegoing battleship.

Volleys Across The Void

In any number of on-screen science fiction sagas, once the enemy is detected, ships will scream at full power to within visual range of each other in order to use weapons of equally limited reach. This makes for great visual drama, but is it really the smartest course of action?

Closing the distance means using the ship's main engines extensively, which will blaze in the enemy's sensors like a star. Also, one questions the wisdom of placing oneself at point-blank range of all the enemy's guns. For most feasible types of space drives, reaching the target may take many hours or even days at full thrust, a heck of a long time to leave your ship vulnerable to easy detection and counterattack.

If you can hit the enemy at a distance without exposing yourself for too long, all the better. Again, we see a parallel to classic submarine warfare. A WWII-era submarine surfaces, launches its torpedoes, then quickly slinks back under the waves, to maneuver around without detection for the next attack. In the deep-space corollary, a ship will ping its target with active sensors for a quick sensor lock, fire its weapons, then quickly go back into stealth mode to cloak itself in the deeps of the void.

Once you know where your enemy is, you still have to hit him. Given the distances involved, you will need weapons that can travel thousands or millions of kilometers and still do significant damage.

Missiles and drones will most likely be of more pratical use than direct-fire beam weapons. Though some beam weapons can be calibrated to reach that far and still do damage, one still has to deal with the major problem of precision fire control. Shooting a target a million miles distant would require targeting accuracy on a par with a sharpshooter hitting a flea from orbit. Since beam weapon systems with the power to cover the ranges needed will most likely be immense, getting such huge machinery to make the minute movements necessary for such greater-than-pinpoint-accuracy would prove a major engineering feat.

A detailed discussion of specific weapon systems will be included in Part Two of this article.

The Best Defense Is A Good Engine

After sensors, drives are the most important aspect of deep-space combat. Like in most other types of armed conflict, how fast you can move and maneuver will often mean the difference between life and death. Again, the mightiest weapons in the universe don't mean anything unless they can hit their target. The faster you can move, the harder it will be for the enemy to hit you, and the more quickly you will be able to bring your primary weapon systems to bear on the target.

Of course, speed has its problems too. Most feasible types of space drives sport engine exhaust that can glow like a star to an enemy's sensors. In the seek-and-detect phase of a battle, main engines may be used sparingly, if at all, lest one tip the enemy to one's current location.

But once it becomes apparent that you've been found, either when the enemy uses active sensors to pinpoint your location or you detect incoming ordnance zeroing in on your position, engine power and your ability to become a moving target become paramount. The idea perpetuated by on-screen science fiction that two capital ships would just float in one spot and slug it out is ludicrous. Why take the shot when you can move out of its way altogether? In three-dimensional space there are many more options for maneuvering than on a planetary surface, making vessels with good engines far more "slippery" and difficult to hit than slower-moving ships.

Space Drives And Combat

Because engine power is so important, a brief list of probable varieties of space drives and their effects on combat is provided below. More detailed descriptions of these technologies can be found in the links at the end of this article.

Chemical Rockets: Enormous fuel requirements, relative unreliability, and short endurance make these engines impractical for a ship's main drive. However, they are useful for short bursts of high acceleration, making them practical as engines for short-range missiles.

Ion Engines: Large arrays of ion engines make for a very fuel-efficient, long-endurance space drive, but one capable only of very modest accelerations compared to other drives. However, while their exhaust is still hot (ion engines currently used on space probes have exhaust temperatures of about 300 C), it is colder than the thousands of degrees of most other types of rocket exhaust and thus would be harder to detect by a distant enemy. This makes them useful to a ship, missile, or drone aiming to reduce its chances of discovery. A ship may have another type of drive for normal operations and specialized ion engines for stealth maneuvers.

Plasma, Nuclear, and Antimatter Rockets: Much more fuel efficient than chemical rockets and capable of much more powerful accelerations, these are probably the drives of choice for any ship in the midst of an ongoing space battle. Their exhaust is highly energetic and often radioactive, making it near-impossible to miss a ship equipped with one of these drives even millions of kilometers off. This type of rocket exhaust also remains dangerous and radioactive many kilometers behind the ship, making it potentially useful as a short-range defensive weapon.

Bussard Ramjet: Theoretically capable of near light speed, this very powerful drive also employs a potent magnetic-field scoop that can extend for tens of thousands of kilometers ahead of the ship. This scoop field is powerful enough to be used as a weapon, potentially destroying any electronics, computers, and unshielded living organisms it encounters. As the ramjet is basically a highly advanced fusion rocket, its exhaust also has potential defensive weapon use.

The Myth Of The Space Fighter

Fighter aircraft form part of the backbone of today's armed forces, harking back to the era of the First World War. In an atmosphere, it makes sense that smaller craft are faster and more maneuverable; both gravity and air resistance work against larger craft.

However, in space, neither of these are a factor, so it makes less sense that space combat be so dependent on small-scale fighters. In fact, capital ships in science fiction are often shown as having enormous engines well in keeping with their scale. Yet if their engines are larger and far more powerful than that of the smaller ships, why are they always portrayed as much slower and more ponderous than the supposedly quick and nimble fighters? Think of a model airplane and a real, full-scale prop-driven aircraft. Both use propeller-driven engines to fly, but there's no question which would win in a race.

Engine power plays far more important a role in spacecraft speed than the size of the ship. Assuming an equal level of technology, since the larger ships have larger and more powerful engines it's logical that they would be capable of far greater speed and acceleration than smaller vessels. In other words, those Imperial Star Destroyers should have been zipping past the TIE fighters, not the other way around!

While smaller vessels would have some maneuverability advantages such as tighter turning radii, a ship with a bigger engine can move faster and thus would be less likely to be hit in battle.

Fighters also require a cockpit, a manual control surface, and life support for the human pilot. Since the fighter could spend hours or days en route to the target, the life-support systems would have be fairly extensive. Fighters also need special pressurized bays for access and maintenance. Finally, in order to preserve the pilot, accelerations will have to be limited to what humans can endure.

Missiles and drones have no such limitations. They can accelerate at hundreds or even thousands of g's, depending on how they're designed. Without the bulky life-support systems and other features required by a human pilot, they can be made smaller and more cheaply, stored on board in greater numbers, and deployed much faster. And, of course, missiles are more expendable than humans.

But perhaps most significantly, human pilots would not be able to match the split-second, minutely calibrated course corrections and targeting resolutions advanced artificial intelligences would be capable of making many times a second. If a civilization is advanced enough that deep-space travel is an everyday occurrence, it should be safe to assume that its computer systems have reached a point where they can outperform any human pilot.

Manned space fighters, while embodying much of the romance of the classic space opera, would prove imminently outmatched on all counts by the larger, faster battleships and their cheaper, more numerous, and far more capable AI missiles.

This is not to say that manned subcraft would have no place in space conflicts. The Traveller RPG contemplated the existence of battle riders, enormous capital ships that would house the bulk of an interstellar drive and act as carriers for smaller ships with less features. But these subcraft would be fully equipped battleships in their own right, not skimpy pseudoaircraft. As it is assumed here humans will make most of the strategic and broad tactical decisions, a ship may deploy a heavily stealthed manned subcraft to direct a fleet of drones or missiles in one area of the battle while the main ship departs for another.

Light-Speed Lags

If multiple ships are deployed by the same side, we run into another major hurdle of space combat: communication and sensor lags dictated by the speed of light. Ships in a single battle group may be deployed many millions of kilometers apart, resulting in communication delays that could stretch minutes or even hours. This makes coordinating efforts among major battle elements problematic at best.

Of course, communication lags were a common hurdle to most armed conflicts before the twentieth century and can be handled much the same way. Individual ships must be allowed a great deal of flexibility and autonomy, with a pre-established doctrine to follow in most foreseeable circumstances.

However, this communications lag combined with the supreme need for stealth in space combat can lead to problems, not the least of which is trying to distinguish a potential enemy from an ally in the heat of battle. Tightbeam radio communication can help with this, but there is the problem of signal leakage and losing track of an ally due to unexpected maneuvering.

Lightspeed lag also plays a major role in hunting for an enemy. When one finds an enemy ship, the data of its position may already be seconds, if not minutes, old. Rather than pinpointing where a ship is, usually the best information that scanner operators can provide is where the ship was and probabilities of where the ship went after that. In other words, when you are plotting a targeting solution to fire your weapons, you are aiming at a sphere of possible ship positions as opposed to the ship itself.

Racing Relativity

Combat at near light speeds carries a number of special challenges. Relativistic effects can greatly alter the nature of a conflict. As speed carries so much importance in combat, ships will edge as close to light speed as possible, if they have the capacity to do so. However, the closer one gets to the velocity of light, the more problematic the phenomenon of time dilation becomes. Those ships moving at significant fractions of light speed will experience the passage of time at a much slower pace than those moving at more normal speeds, creating even more of an information lag between attacker and target and making coordination among fleet elements much more difficult. Calculating and compensating for the differing temporal frames of reference would be essential to ships capable of near-luminal speed.

Also, relativistic effects can greatly extend the length of a battle. At large fractions of light speed, millions of miles can be eaten away quickly, light-speed lags mount up, and time dilation can stretch a battle significantly to those observing it from a "normal" frame of reference. Stories by both Larry Niven and Stephen Baxter have explored this situation in the extreme, as combatants chased each other across the galaxy and engaged each other at speeds a hairsbreadth away from the speed of light. These battles spanned tens of thousands of years, outlasting the civilizations that originally built the ships, yet to the crews only weeks had passed.

Grading Sci-Fi Space Combat

Now that we know more about how warfare in space will be fought, how do various science fiction properties compare? The following is a brief summary of how realistically or not science fiction television shows and movies portray space combat. This is not a reflection of their overall entertainment or storytelling quality, but simply a brief technical analysis.

Star Wars, et al.: D-. Basically WWII naval combat taken to space. Exhilarating to watch, but ultimately unrealistic.

Stargate: SG-1: D-. Large nonmoving capital ships slugging it out at eyeball-range.

Battlestar Galactica (classic): F. Based on the Star Wars model, with even worse science. Since I haven't seen the newer version, I can't comment on it specifically.

Star Trek (original series): C. Given its advanced technical assumptions (ships moving at significant fractions of light speed, shooting at each other across thousands of kilometers), it actually portrayed battles semirealistically despite (or perhaps thanks to) its more primitive special effects.

Star Trek: The Next Generation: D. Capital ships just sat on screen exchanging shots. Does get some points for some episodes that hearken back to the original series model, plus important role of ship detection and sensors.

Star Trek (later series): C-. The capital ships begin to move, at least in most cases. But except for a few tantalizing examples (e.g. the Voyager episode "Equinox"), the franchise is still too mired in the Star Wars model.

Andromeda: B. Semirealistic given its superscience technical assumptions. Ranges are measured in light-seconds, missiles and projectiles are used for long-range shots, sensors play an important role. Loses some points for overdependence on manned fighters in later episodes.

Babylon 5: C. Space combat based largely on the Star Wars model, but stuck somewhat more closely to realistic technical assumptions. Loses points for too many eyeball-range battles and dependence on manned fighters.

Grade A's

There are few works in science fiction that portray deep-space combat with a realistic basis in science. I've listed a few below.

Traveller RPG: The most realistic space combat is not found on-screen or in fiction but in one of the seminal table-top role-playing and strategy games. Earlier editions of the Traveller RPG in particular took the sheer immensity of space seriously and even had vector-based movement for their tactical spacecraft simulations. Even though the game borrowed much of its ship-design philosophy from Star Wars, space combat was fought over many game-hours or days, as the vessels hunted each other across tens of thousands of kilometers of space, desperate to get the first weapons-lock. High Guard, the original space-combat expansion for the game, now well over twenty years old, still stands as the hard-SF fan's definitive representation of "realistic" combat in deep space.

Orion's Arm: An online shared world-building and creative writing project, this hard science approach to far-future science fiction contains very well thought-out essays on the nature of future warfare.

Known Space: Larry Niven's "Known Space" books encompass something like three dozen novels, short stories, and shared-world anthologies. One of the hallmarks of Niven's work is his meticulous attention to hard-science detail. His work shows some serious thought on combat at relativistic velocities and the large time scales that may be involved.

A Fire upon the Deep and A Deepness in the Sky by Vernor Vinge: These related novels both show Vinge's grasp of the complexity and scale of deep-space battles, including harrowing conflicts fought with swarms of missiles and drones.

Singularity Sky by Charles Stross: One of the most hard-science looks at space warfare, as a human fleet attempts to take on a post-Singularity civilization.

Conclusions

As humanity moves out into the universe, we will take our nobility, our curiosity, and our courage with us. But so too will we take our capacity for war and destruction.

Space offers a battlefield unlike any in history, with unique obstacles that will challenge human ingenuity to the utmost. Rather than blazing beams and swooping dive-bombers, victory in such an environment, as we have seen, will depend much more on stealth, cunning, and smart tactics.

[Editor's Note: The second part of this article, "Hunters in the Great Dark: The Weapons of Deep-Space Warfare," appeared in the following week's edition of Strange Horizons. Read it here.]