I know all you Battlestar Galactica fans are not going to want to hear it, but looking from a cost/benefit analysis, space fighter craft do not make any sense. Go to the Future War Stories blog and read the post Hard Science Space Fighters.
And before you rage at me for taking away your cherised X-Wing you might want to review the section on Respecting Science.
Ken Burnside tells it like it is:
Why is there a constant stream of media science fiction featuring space fighters, readily available for new fans to imprint on? I suspect what Charles Stross calls "Second Artist Effect." The first artist sees a landscape and paints what they see; the second artist sees the first artist's work and paints that, instead of a real landscape. In this case the first artist is George Lucas in 1977 with his World War 2 X-Wings and T.I.E. Fighters.
But it might be a bit more complicated. Here's my reasoning:
It seems to me that the space fighter is nothing more that people taking a dramatic and comfortable metaphor (sea-going aircraft carriers and combat fighter aircraft) and transporting it intact into the outer space environment. But if you think about it, interplanetary combat is highly unlikely to be like anything that has occurred before.
Here's an analogy: Imagine a speculative fiction writer back in the Victorian era, such as Jules Verne. Say they wanted to write a novel about the far future, when heavier than air flight had been invented, and the age of Aerial Combat had arrived.
They might take the dramatic and comfortable metaphor of sea-going frigates and battleships and transporting it intact into the aerial environment. Held aloft by dozens of helicopter blades, the battleships of the air would ponderously maneuver, trying to "cross the T" with the enemy aerial dreadnoughts.
See how silly it sounds? Well, combat spacecraft behaving like fighter aircraft is just as silly. In both cases a metaphor is being forced into a situation where it does not work.
In reality, when the Wright brothers invented heavier-than-air flight and Fokker Triplanes started dog-fighting Sopwith Camels, it was totally unlike anything that had occurred before. Biplanes never ever tried to cross the T, and a sea-going battleship had never ever performed an Immelmann turn.
Therefore, by analogy, when interplanetary combat arrives, it too will be totally unlike anything that has occurred before.
As Ken Burnside puts it:
While space fighters in general are pretty worthless, it is possible for an author to establish a specialized situation making them practical.
As Ken Burnside said: "What do fighters do better than, or exclusively related to, larger ships? Answer this, and you get a reason for fighters in a setting."
If the author has already allowed handwaving faster-than-light travel into their literary universe, it should be straightforward enough to tweak it such to allow the existence of spacefighters. TV Tropes says just use Applied Phlebotinum or Minovsky Physics.
One example using handwaving faster-than-light starships is the Traveller Battle-Rider.
Another example are the fighter starship of William H. Keith's Star Carrier series. They use a handwaving carrot-on-a-stick drive, accelerating at 50,000 g and reaching relativistic velocity in about ten minutes flat. So sorry, huge capital ships and carriers cannot use this marvelous propulsion system, so they cannot act like fighters. Sadly while the carrot drive's gravity gradient across a twenty meter fighter is negligible, it will rip apart a one kilometer battleship with tidal forces.
However, culture only goes so far. Currently (2012) in Afghanistan, the US Air Force is used to attack partisan forces. But more and more the attacks are carried out by remotely piloted drones, not by valiant Top Gun piloted fighter aircraft.
The Air Force pilots are quite angry about this. They are angry that their role is shrinking, they are angry that their chances of flying exciting missions grow slim, they are angry that fat-bottomed desk-jockys controlling a drone from an office in New Mexico are called "fighter pilots" just like them, they are just angry.
But culture or no, in 2011 the Air Force said it trained more drone pilots than fighter and bomber pilots combined.
In 2016 things got worse for human fighter pilots. Researchers developed software that (in computer simulations) reliably defeated human pilots. So instead of being replace by a fat-bottomed desk-jocky, they are being replaced by a computer.
If you just can't live without your T.I.E. fighter (or if you are an author pandering to your audience) you might as well get the rest of the science correct anyway. Think up some justification to allow space fighters to exist, then try to live within the draconian constraints.
Keep in mind that even if you have space fighters, they are not going to fly like winged fighters in an atmosphere. I don't care how the X-wing and Viper space fighters maneuvered. It is impossible to make swooping maneuvers without an atmosphere and wings.
No such thing as space dog fighting with banking turns. Not yours.
You also cannot turn on a dime. The faster the ship is moving, the wider your turns will be. Your spacecraft will NOT move like an airplane, it will act more like a heavily loaded 18-wheeler truck moving at high speed on a huge sheet of black ice.
And another thing: if you maneuver, you are NOT going to be slammed into walls by high gee forces like a NASCAR race car driver. It doesn't work that way unless you have an atmosphere and wings. The only thing you will feel is a force in the same direction that the rocket exhaust is shooting, which will be equal to magnitude to the acceleration the engine is producing. Since Rockets Are Not Boats, the force generally be in the direction the crew considers as "down", as defined by the rocket's design. It will never be "sideways" (except under silly situations, like occupying a spinning centrifugal gravity ring while the rocket is accelerating).
It doesn't matter if you are thrusting in some other direction that the rocket's direction of travel (see Rockets Are Not Arrows) nor does it matter the rocket's current velocity (relative to what?). If the rocket engine cannot provide more than 0.5 gs of acceleration, the crew is never going to feel more than 0.5 gs of acceleration. Even if the ship is moving at a large fraction of the speed of light.
In the 1970's, DARPA was looking into a crude spacecraft called the "High Performance Spaceplane" that looked suspiciously like a space fighter, you can read about the details here and here. However, it was more like a manned missile than it was a Viper from Battlestar Galactica.
The above was written in 1985. Alas no "space fighters" have made an appearance. And unfortunately with current technological advances, it seems more likely that a space fighter developed today will be an unmanned drone, not a Starfury.
This paper was written using the following assumptions as a baseline.
1. Physical laws:
The laws of physics as we know them still apply. This means that spacecraft move in a Newtonian (or Einsteinian, though this realm is outside the scope of the paper) manner, using reaction drives or other physically-plausible systems (such as solar sails) for propulsion. Thermodynamics dictate that all spacecraft must radiate waste heat, and lasers obey diffraction. The only exception is FTL, which will be included in some scenarios.
The technological background is less constrained. If a system is physically plausible, the engineering details can be ignored, or at most subject to only minor scrutiny. The paper will examine a spectrum of technology backgrounds, but will focus on near to mid-future scenarios, where the general performance and operation of the technology can be predicted with at least a little accuracy. A common term used to describe this era is PMF, which stands for Plausible Mid-Future. This term (coined by Rick Robinson) is difficult to define, but it assumes significant improvements in technologies we have today, such as nuclear-electric drives, fading into those we don’t, such as fusion torches.
This paper will attempt to examine a wide variety of environments in which space combat might occur. However, it will make no attempt to examine all of them, and the scenarios described will conform to several principles.
First, this is a general theory. Any scenario that is dependent on a one-shot tactic or highly specific circumstance will likely not be included, except during the discussion of the beginnings of space warfare, or to demonstrate why it is impractical in the long run. The recommendations made are not optimal for all circumstances, nor is such a thing possible. They are instead what the author believes would be best for a realistic military based on the likely missions and constraints. Picking highly unlikely and specific sets of circumstances under which they are not optimal is best answered with a quote from the author about one such scenario, posting on the Rocketpunk Manifesto topic Space Warfare XIII: “You need a blockade, a hijacking (innocents aboard a vessel trying to break the blockade), and a high-thrust booster on the hijacked ship. Two stretch the limits of plausibility. The third is ridiculous. Claiming that this justifies humans [
onboard warships, see Section 2] is like claiming that because warships sometimes run aground, we should install huge external tires on all of them to help get them off.”
Second, no attempt will be made to include the effects of aliens or alien technology, because to do so would be sheer uninformed speculation.
Third, the default scenario, unless otherwise noted, is deep-space combat between two fleets. Other scenarios will be addressed, but will be clearly noted as such.
Space fighters are a controversial topic in hard sci-fi space warfare discussions. The consensus among the community is that they are not practical in the way they are depicted by Hollywood, nor in most other ways imagined, and that is a view the author shares. However, this consensus is continually challenged, and the purpose of this section is to collect most of the rebuttals to those objections.
What exactly is a space fighter? That varies depending on the context of the discussion, but the average person would probably point at an X-wing or TIE fighter. A 10-20 m long spacecraft with a one or two man crew and a few hours of endurance. In other words, something much like an atmospheric fighter, but in space. Others would expand the definition to include any small, low-endurance combat craft, particularly those carried by other vessels. Some would broaden the definition even more, to the point where it bears no resemblance at all to a classical space fighter. Many of these proposals for “fighters” suffer problems which render them marginally effective or ineffective, and those that don’t are the ones that bear the least resemblance to the visions of Hollywood. In the interest of accuracy, any vessel carried and deployed (that is to say, not merely shipped to a destination) by another vessel will be referred to as a parasite, leaving fighter to describe Hollywood-type combat parasites.
The origin of the space fighter is obvious. It was developed out of an analogy to wet navy combat, specifically the aircraft carrier and its fighters. Even the serious space warfare community often engages in wet navy analogies, so it appears to make sense to expand it to include carriers and fighters. This suffers one critical flaw. Aircraft carriers are effective primarily because aircraft work in a different environment then do ships. A carrier can stay on station for months, but can only go at around 30 knots, while a fighter can make Mach 2, but only has a few hours endurance. In space, a fighter will have no environmental advantage over its carrier. Both obey the same rules, so any advantage must come from size and design. A much better analogy is that of large and small warships, such as destroyers and Fast Attack Craft.
The naval analogies that underlie the basic concept of the space fighter deserve closer examination. Before the late 1800s, small craft did not have the ability to threaten larger ones while the larger ship was not at anchor. This changed with the invention of the torpedo. For a time, many, most prominently the French Jeune Ecole, believed that the torpedo boat spelled the end of the battleship. While this obviously did not happen, many navies experimented with various ways to use torpedo boats, including building torpedo boat carriers. During the Russo-Turkish war of 1877, the Russians converted several vessels to carry torpedo boats, and a torpedo boat operating from the tender Veliky Knyaz Konstantin became the first vessel to sink another with a self-propelled torpedo. In the 1880s, the Royal Navy built HMS Vulcan, while the French Navy produced Foudre, both cruiser-type vessels, meant to travel with the fleet and deploy 8 or 10 small torpedo boats against the enemy. Both remained in service for about two decades, before being converted to other roles. There has been occasional discussion by various powers about building more such ships, including by the US in WWII, but nothing came of it. In fact, despite the presence of LSDs (Land Ship Dock) in the fleet, including for carrying PT boats to the front lines, there are no records of PT boats being launched into action from LSDs. The total failure of this idea renders dubious the prospect of a similar vessel in space.
These are the next major issues. One often-noted advantage is that a fighter only has to carry a few people and a few days’ worth of life support, which gives it superior performance to a larger ship. This makes sense at first glance, but several factors conspire to defeat it. First, how much of that performance is really useful? Second, how does the fighter in question actually kill its target? Third, how much money is being spent on all of this, anyway? Fourth, do we need people aboard at all?
Maneuverability is a common explanation for fighters. The logic is that a ship that has a higher acceleration is better, so cutting out as much dead weight as possible is good. However, to what extent is this statement true when balanced against other factors. A fighter by definition is of limited operating endurance. Most proposals run from hours to a week or two. Within that time, it must return to its base, generally a carrier, to restock. A ship’s maneuverability is furthermore defined by two factors, delta-V and acceleration. While a fighter would have superior acceleration, that must be balanced against its generally more limited delta-V.
One salient fact to keep in mind is that ships that maneuver in combat using the same drive they cruise under are not maneuverable in combat. Given the amount of time spent under thrust, generally measured in days if not weeks, ships will be unable to change the tactical geometry in a meaningful way during a few hours, let alone a few minutes. This does not apply if the ship fights under a different engine then it maneuvers with. Attack Vector: Tactical uses this approach, with engines having a high-efficiency, low-thrust cruise mode and a high-thrust low-efficiency combat mode. However, this seems somewhat unlikely given currently foreseeable technology. Mass-injected fusion drives could work this way (as they do in AV:T), but they are at the limits of the technology under consideration in this paper.
The limited endurance of a fighter presents two problems. The first is that, as mentioned above, a ship that uses the same, or even a similar (within about an order of magnitude in terms of thrust/delta-V) drive in combat as in cruise will not be able to change the tactical geometry in a meaningful way during combat. This applies to parasites as well. The parasite’s cruise drive is that of the carrier, which means that it must have a significantly higher-thrust drive then the carrier does. However, given that both operate in the same environment, the parasite will likely have to mount an entirely different type of drive. This is a common fictional explanation, but there is no reason to believe that a small ship will be able to use drives that a larger ship could not also mount. One could install a chemical or nuclear-thermal engine, which are not likely to be used by interplanetary vessels, but both of those have limited delta-V, which, when combined with the next issue, renders that proposal extremely questionable for deep-space combat.
An interesting solution to the different drive problem is an “antimatter afterburner”. This involves the use of small amounts of antimatter in a fighter engine of some type as the name implies. The originator of the idea suggested that expense and danger would prevent similar technology from being used on larger vessels. The use of antimatter in large quantities removes the idea from the realm of the PMF, and the author believes that danger can be handled with proper engineering. Expense is an open question, but the other problems with fighters are likely significant enough to torpedo the idea.
A parasite must return to its carrier before its endurance is exhausted. While that statement is obvious, it places severe limitations on tactical flexibility. First and foremost, a parasite will need four times its average transit velocity relative to the carrier in delta-V. To state it another way, a parasite will have an average transit velocity of at best one-fourth of delta-V. Maneuvering the fighter will reduce the transit velocity available. If a parasite is using a high-thrust, low-ISP drive, the low delta-V achievable will limit transit velocity, and maximum range from the carrier (assuming the carrier does not accelerate during the mission) can be defined as transit velocity times one-half of endurance. For any reasonable ranges, endurance will have to be large, or transit velocity very high, implying fusion drives or similar technology, and raising the question of the advantage of fighters over conventional ships again.
Note that the maximum range for a given endurance and delta-V will only occur when the delta-V used for the outbound and return legs is equal. Any other distribution will result in a lower average transit velocity, and thus reduced range. This distribution also corresponds to the highest average transit velocity possible for a mission of a given range, which could be of great importance if the fighter is to be recovered and reused during a given battle. Table 1 shows how the distribution of delta-V affects transit velocity for a given endurance and total transit time for a given range. Note that these numbers only apply in flat space and if the carrier is not accelerating during the mission. Because the fighters start at rest relative to the carrier, and must return to it, any velocity the carrier initially possesses is irrelevant. Flat space should be a reasonable approximation for deep-space engagements, and near-orbital space will be dealt with later. Also, it is assumed that the burns are short relative to the total transit time, which is a good approximation for most cases, although not necessarily high-end ones.
Table 1 High Leg
0.5 0.5 1.0000 0.25 1.00 0.6 0.4 1.0417 0.24 0.96 0.7 0.3 1.1905 0.21 0.84 0.8 0.2 1.5625 0.16 0.64 0.9 0.1 2.7778 0.09 0.36
If the carrier maneuvers during the mission, it sets off a complex interplay of carrier delta-V expenditure, fighter delta-V expenditure, and transit time changes, leaving aside the tactical effects of the carrier’s maneuvers, which fall outside the scope of this section. In the most extreme case, a fighter might expend its entire transit delta-V in a single burn to intercept the target, and then allow the carrier to match velocities and catch it. This would require massive delta-V from the carrier, and significant time, particularly if the carrier’s drive is low-thrust. Also, the tactical and orbital effects are likely to be severe. A more practical situation might be for the fighters to expend all of their delta-V on the outbound leg, and wait for the carrier to reach them at the target. This takes less delta-V from the carrier, and significantly less time, but does leave the fighters vulnerable if things go wrong. Moving the carrier towards the target is also potentially problematic. If the carrier simply accelerates and decelerates to rest relative to its initial velocity, the transit time is reduced somewhat at a cost in delta-V. If it does not decelerate, the fighters will have to expend additional delta-V to match velocities. Likewise, after reaching the target, the fighters could expend all of their delta-V on start of the return leg, and the carrier could match velocities. The effect of all of these must be evaluated on a case-by-case basis, although the analysis itself is quite simple once the parameters are established.
Once the fighter has reached the target, it must still kill it. Plausible space warfare weapons break down into three main categories: beams, projectors, and missiles. Beams, which include both EM and particle beams, travel at close to the speed of light, but fall off with distance. Projectors cover any weapon that fires mass at a target, where most of the velocity is imparted by a device on the ship itself. Cannon, railguns, and coilguns are all examples of this. Velocities achievable are likely to be limited to less than 100 km/s. Missiles are any kinetic weapons released from a vessel which gain their velocity from some combination of the velocity of the launching ship and an internal engine.
Beams and cannon are not good candidates for fighter weapons. Lasers scale significantly with size (see Section 7), which generally means that the vessel with the largest laser wins. Particle beams and launchers also scale with size, though probably not as strongly, which puts any fighter mounting them at a disadvantage. That leaves missiles.
Missiles make sense. Put some missiles on a fighter, send it to within range of the enemy, and shoot them off. The problem is that, in space, missiles don’t have range. A missile will likely coast for much of its flight anyway. There is no reason to use a fighter to launch a missile. Put on another stage, and remove the fighter entirely. More of these missiles can be fit into the space formerly occupied by the fighters, which increases firepower, and probably cuts costs in the long run, as a fighter has to decelerate to a stop, then come back, burning remass the whole way, not to mention the cost of support facilities for the fighter.
But what if money can be saved by using the fighter for all of the missile’s primary delta-V? The fighter simply tosses them out, leaving them to guide their way in. This vessel is generally referred to as a Lancer. The problem is, again, delta-V. A lancer would have to stop, and return to its carrier after launching the missiles. It might not have to have four times the projectile velocity in delta-V, as it can return to the carrier at a lower velocity then it launched from, but something on the order of three times launch velocity is probably the minimum practical delta-V. If the lancer and a self-propelled missile are using broadly similar engines (similar ISP) the lancer would have to have at least three times the fuel fraction for the same impact velocity, if not significantly more.
The only situation where this would be a generally viable tactic is if, for some reason, the missile cannot use a drive that is within the same ISP range as the lancer’s, probably for cost reasons. This might be the case when, say, fusion drives are new. The cost of the drive is high enough that it is a requirement to reuse it. Conventional missiles are impractical, because chemfuel simply can’t generate enough delta-V to be viable against fusion-powered vessels. Thus, a lancer is developed. This is a fairly specific set of circumstances, and should not be generalized to most situations.
Note that the rejection of beam-armed fighters is based upon the beam weapons in question scaling with size. If this is not the case, (Dr. Device from Ender’s Game is the only example which springs to mind here, although the description in Ender’s Shadow casts doubt on if this is actually what’s going on) there are advantages to having as many platforms in action as possible, and fighters become an option again. Another case in which fighters (or combat parasites in general) might become practical, also illustrated by Ender’s Game, involves an interplanetary propulsion system that for some reason cannot be fitted to individual combat craft. This could be for any number of reasons, including expense, minimum size of the systems, or simple rarity of the drive. In any of these cases, it would be logical to use parasites to fight, and leaving the drive spacecraft in the role of command ship.
One option for parasites is a type of missile defense drone. The purpose of this drone is to bypass the armor of incoming missiles. It is not armed with conventional weapons, but instead contains a pair of linked telescopes. One of these receives a beam from a larger vessel in the main fleet, while the other redirects it to a missile. Conventional missiles are only armored on the front, so a laser from beside or behind them would be highly effective. While this tactic is not impossible to counter, mostly by spreading the armor more evenly across the missile, doing so will reduce the armor thickness or increase the mass, and thus the cost of the missile. Either means is a win for the defender, which makes this category of parasite potentially quite useful. One thing should be noted about this type of craft, though. It operates at short ranges from the fleet, and can use a rather low transit delta-V, which removes a lot of the problems of other parasites.
One common claim for the superiority of fighters is that they are cheaper than an equivalent amount of firepower in larger vessels. On the surface, this claim is true. Fighters, not being required to have long-term living quarters and the like, do seem to deliver high firepower per dollar (or credit or yuan or what have you). The economics become much less robust, however, when the cost of the carrier is factored in. Before delving into that, a discussion of carriers themselves is in order.
Carriers can be of several different types. The simplest is to strap parasites to the hull of a ship, and detach them for battle. This design promises low cost, but limits the utility of fighters, as they likely can’t be rearmed or refueled, and maintenance is very difficult. More complex designs have specialized docks, which allow easy rearming and refueling, but limit access to the outside of the parasite in question. This works better with gunboat-type parasites, which have significant capability for independent operation, and should be capable of being serviced from the inside. They would also provide some living quarters and support for the crew. The final step is a full carrier with pressurized fighter bays, which is the type usually seen on TV. These are mass-intensive, but allow classical fighter operations, with external maintenance and the like. The crews are housed onboard, and all support gear is on the carrier.
The first option is obviously the cheapest, but suffers from the fact that it more resembles the British Catapult-Armed Merchant ships of World War II then a proper carrier. The fighters are one-use, and probably can’t be maintained terribly well. While they can be recovered after battle, they are helpless until a tender of some sort is reached. The second option requires a dedicated ship, but, apart from magazines and remass tanks, is not terribly mass-intensive, and probably no more than 25% of the mass of the carried craft is required in clamps and docking systems and such. The full carrier is, however, highly mass-intensive. At best, a ratio of 100% of parasite mass to docking facility mass might be achievable. However, this is probably optimistic. All quarters and such must be duplicated, and the bays themselves are going to be large, if mostly empty when unoccupied. There are actually two options for hangar arrangement. The first, and most obvious, is to dock each fighter in individual bays, or place a few fighters in each bay. The alternative involves a large central hangar and the use of airlocks to move fighters in and out. This approach is probably more efficient in terms of mass, volume, and ease of maintenance, particularly for large numbers of parasites, but will launch and recover its parasites more slowly than if they were in individual bays.
Why is mass so important to determine cost? It’s not weapons and electronics, which are expensive, is it? The problem is that for a given vessel performance (delta-V and acceleration), cost will tend to scale with mass. More mass means bigger fuel tanks, bigger engine, and more structure. A conventional vessel of the same weapons cost as a carrier and fighters will almost certainly be considerably cheaper overall. It does not require duplicate engines, duplicate quarters, pressurized fighter bays, extra remass tanks, or any of the other sundries that a fighter squadron would require.
The actual mechanics of carrier operations is an interesting issue as well. Numerous different methods for operating small craft off of bigger craft have been proposed, some more viable than others. For the first two types of carriers, the chosen method of recovery, namely simple docking, is quite obvious. This is also a potential method for a hangar-type carrier. In that case, the fighter would probably dock on some form of movable attachment, and then be moved inside. This attachment could range from a simple extendable arm for a bay-style carrier to a “tractor” for a lock-style carrier. An alternative is the use of an arm to recover (and launch) fighters. This draws on the experience with the Candararm on the Space Shuttle and ISS. The advantage is that it requires less skill on the part of the pilot, and is generally more versatile, as well as potentially simplifying handling.
One interesting alternative is the use of an actual deck, probably on a lock-style carrier. This is most useful with aerospace fighters, which have landing gear that might simplify handling and operations. The biggest problem is that there is no gravity to keep the fighter on the deck, necessitating either some sort of physical hold-down, or the use of magnets to keep the fighter on the deck. The use of a deck was originally proposed in conjunction with the use of arrestor wires, much like how aircraft are recovered by aircraft carriers. There are, however, numerous problems with this approach. The dynamics of recovery are significantly different from those of a naval carrier, mostly due to the fact that the wire must both stop the fighter and hold it on the deck. Even at the proposed approach speed of somewhere below 1 m/s, there are serious questions about the actual viability of hitting such a small target with a hook without snagging one of the wheels, or bouncing off the deck into space. More problems would be caused in handling the aircraft on the deck, as the original proposal involved using the wires and a magnetically-attached tractor to move the fighter onto the elevator before strapping it down. In total, this is not a viable solution to the problem, and would not be seriously considered by any competent aerospace engineer. A better alternative if a proper deck must be used is based on the Canadian Beartrap system for helicopter recovery. In this, a cable attaches the fighter to the carrier, and the fighter is simply winched down at low speed. This is more space-efficient, safer, and easier to implement. The biggest problem with it, and a serious problem with the wires, is the need to open holes in the heat shield of the fighter. While the conventional landing gear would indeed need such holes, opening them unnecessarily increases the chances of something going wrong, as does cutting extra holes for the hook or beartrap system. All in all, it appears that either a probe or an arm system would be the most effective.
The only situation in which a fighter-like vessel would be useful as a major combat craft is during planetary defense. This scenario plays to the advantage of short-endurance craft (low cost per unit firepower). However, there is no reason to suppose that conventional fighters will dominate this field. It is entirely possible that full-sized warships could be constructed with limited endurance specifically for planetary defense missions. The best analog for these vessels are the coastal defense ships of the first half of the 20th century.
This concept is covered in more detail in Section 6.
The last question is the one that nobody wants to ask. Do we even need people aboard these things? As Rick Robinson points out, there are only three missions for space fighters:
- Fighting each other, which is not a reason to exist.
- Destroying battle stations, which are only vulnerable to fighters for some reason.
- “To give prominent roles to young males in their early twenties, so they can display their swagger, coolness, and fast moves on any attractive female of an Interbreedable species.”
To seriously look at this, we first need to establish one principle of spaceflight. Spacecraft are the ultimate in fly-by-wire controls. There is no need to have people stuffing photons into the lasers, or laying the coilguns by hand. There are no stokers throwing uranium into the reactor, and no lookouts in the crow’s nest watching for the enemy. Almost all roles aboard a ship are those of bridge crew, or maintenance. Why is this important? The computer doesn’t care if it gets its orders from onboard control stations or by tight-beam laser from a mothership a light-second away. This makes automation very easy. Fighters almost by definition have no maintenance onboard, leaving only the pilot. But why have a pilot onboard? He only adds mass, and lots of it. For a few hours to a day or so, he can probably get by on a ton or two. After that, habitation demands start to render the “fighter” indistinguishable from a normal ship. This neglects the added costs of the hab itself. That mass can be a significant fraction of the total vessel mass, which will either drive up vessel mass and cost for equal performance, or reduce performance. All of this indicates that any form of fighter, or combat parasite in general, is likely to be unmanned.
All of the above discusses the usefulness (or lack therof) of fighters to a deep-space fleet engagement, and combat will obviously not be limited to that environment. Orbital combat is often suggested as an ideal environment for fighters, and on the surface, it has much to recommend it. The superior acceleration of the fighter allows it to change orbit more quickly than a larger vessel, and the fact that it’s in orbit keeps it close to the carrier. At the same time, a larger vessel is more vulnerable to surface-based defenses and less maneuverable. The problem is lack of role. There is no particular reason that a vessel would need to venture into low orbit for battle. A laserstar should be able to stay well out of range and fire into low orbit, and the fact that the vessel in question is the attacker allows it to force the faster opponent to give battle. While some sort of spotting drone might be required, there is no reason for it to be manned or armed.
The most likely use of manned parasite craft is for carrying people, either for landing or boarding missions. These are not terribly common during battle, but occur more frequently on patrol missions. Patrol missions are where parasites are likely to come into their own. First, patrol is not used to speak of a ship making a loop to check on a colony. The concept involved is more akin to the Asiatic Stations of the beginning of the 20th century. The proposed “Patrol Carrier” would be semi-permanently stationed at a potential crisis area, most likely a gas giant, and carry a variety of small craft. The carrier has the responsibility of dealing with any minor crises in the area, similar to the manner in which carrier battlegroups are deployed by the US today. The technological imbalance involved makes several things feasible, including lancers. The lancers operate in a low-threat environment, but might be used regularly. One problem with lancers that most people miss is the fact that they require frequent use to be cost-effective. Given the expected rarity of major battles, lancers make little sense for the main fleet. However, a patrol carrier in an active region would need to make frequent use of them, making them more useful.
An interesting suggestion for such a vessel is to make use of the same drives for both lancers and manned patrol/inspection missions. This would have advantages in logistics, but might require significant design compromises. First off, the payload sizes are likely to be somewhat dissimilar. A manned inspection pod is likely to be somewhere above 10 tons, which is quite large for a typical lancer payload. It is possible that multiple sizes would be used, but that reduces the logistical advantages.
Another type of fighter that has been suggested is the aerospace fighter. It, as the name suggests, operates both in the atmosphere and in space. This is somewhat more plausible, as deep-space craft will almost certainly be incapable of atmospheric flight. Aerospace fighters can be divided into four categories: dual-role, ground-launch space, space-launch air, and space-drop air.
Dual-role aerospace fighters are designed to fight both in the atmosphere and in space. This type is actually the classic Hollywood “Space Fighter”, but is extremely unlikely in reality. Both aircraft and spacecraft suffer significant performance penalties for excess mass. The requirements of combat in the air and in space are vastly different, which means that the mass penalties pile up quickly. Add to that the fact that the dual-role has to cross a third environment (atmosphere-to-orbit and back) and the resulting design will be expensive, underperforming, and probably a maintenance nightmare to boot. There is virtually no commonality between the requirements of the different roles. The only common weapon would be some form of gun, and a conventional gun is unlikely to be of much use in space due to its low muzzle velocity, while high-velocity guns used in space might well have problems functioning in an atmosphere. Missiles for the two environments will be completely different (although it might be possible to make a dual-purpose missile at a moderate penalty in size/cost/performance), and the use of lasers on an atmospheric fighter is dubious at best, particularly lasers with sufficient range for space use. Theoretically, two sets of optics could be used, one for space and the other for atmospheric combat, but mass again dictates against this. The airframe and atmospheric engine are virtually useless in space, and the fact that it must also have a heat shield and be an SSTO seal the verdict. The only situation in which one of these might see use would be for overawing primitive natives, particularly those that understand the design tradeoffs involved.
Ground-launched space fighters are entirely different. As the name suggests, they only fight in space. Besides not having to deal with the mass of the atmospheric combat systems, this has other advantages. It does not strictly have to be an SSTO, and for very early space combat could be the dominant warcraft. An example of this would be the Dyna-Soar spaceplane, which was to be launched by a Titan III. The weapons fit would probably be limited, and on-orbit time minimized, possibly to the point of taking the SpaceShip One approach and not going into orbit at all. The biggest question for this design is operational. What advantage does it have over putting another stage on a missile? Basing is non-trivial unless one accepts the design headaches of VTOL, and there is probably only a small marginal cost savings, easily erased if the opponent destroys the fighter on even a small proportion of missions. The only advantage the author can think of is the ability to use vacuum-frequency lasers. Aerodynamic limitations would restrict mirror size, and mass would restrict both that and laser generator mass, which then raises the option of making a bigger ground-based laser instead.
Space-launch air fighters are the opposite of ground-launches. They have the advantage over dual-roles of not needing space combat capability, and would in fact probably be designed with the minimum possible space operational capability in mind, only barely getting into orbit after a mission, and relying on the carrier for pickup. This would of course restrict their use when the opponent still has significant orbital defense capability due to the risk to the carriers. However, the need to have SSTO capability would still place them at a significant disadvantage compared to conventional atmospheric fighters. The question again is operational. It has been suggested that this type of fighter could be used to destroy heavily-defended targets during a planetary invasion. The author is skeptical of that for a variety of reasons. To begin with, kinetic bombardment should be more than adequate for almost any target. The author cannot see any situation in which an airstrike is superior to a kinetic bombardment for a given target. If for some reason, an airstrike is an absolute necessity, cruise missiles are a far better option. While they might cost more than a fighter’s payload, they are expendable and do not face the design constraints of having to return to orbit. Secondly, defending against an in-atmosphere assault is quite easy. The fighters entering the atmosphere are vulnerable to ABM-type defenses (discussed in Section 4). These weapons will probably have ranges on the order of 1000 km, giving the opponent plenty of warning, or inflicting heavy casualties on the attackers. Not only that, the fighters are in fact more vulnerable than kinetics because they must be almost at rest at the end of atmospheric entry, instead of trying to maintain speed. After reaching the lower atmosphere, fighters are vulnerable to the diverse array of anti-air weapons that have been developed, many of which are quite cheap compared to spacecraft and planetary defenses. Thirdly, the cost of the fighters is likely to be quite high, as is attrition. None of the points above suggest that losses per mission will be low, but low losses are required for the reusability touted by proponents of this concept to give significant savings. The added vulnerability of the fighter returning to orbit is another significant problem. The defender will keep shooting if for no other reason than to prevent it being sent back tomorrow. The only situation in which this concept would be practical is one of overwhelming technological advantage, which is mostly outside the scope of this paper.
In fairness, it would be a fairly trivial matter to equip a missile-armed space-launched air fighter to serve as a dual-role fighter. While the missiles would have to be different, only minor changes would be required to the rest of the vessel. The problem is that the air mission mass would be a significant penalty, and the expense of the fighters, not to mention the general lack of utility of fighters in orbital combat, renders operational use of the concept dubious.
The last concept, space-dropped air fighters, is the most practical. Instead of launching a fighter capable of returning to orbit, an invading power fits a more-or-less conventional atmospheric fighter with a heat shield and some modifications to allow air-starting, and drops it into the atmosphere in support of an invasion. The practicality of planetary invasions aside, the main problems are logistical. There is only a minor performance penalty, and air cover would be quite useful for a beachhead. Fuel and (to a lesser extent) ordinance are likely to be the killers here. A nuclear-powered laser-armed fighter, though a bit far-out, would be the most logical way of solving this problem. Though undoubtedly more expensive than a conventional fighter, the logistical savings might make up for it. It is even conceivable that such a craft might be capable of SSTO performance, although the penalties for doing so would be significant. VTOL offers another option, combined with lots of planning to ensure availability of supplies and weapons.
Another application of this general concept is expendable drone fighters. In this case, the fighter is written off after use, but avoids the need to return to orbit. The practicality of this approach depends on how the debate over manned combat aircraft turns out, a subject which lies outside the scope of this paper.
A one man fighter spacecraft would be a more effective weapon if you removed the fighter pilot, their life support, and their acceleration limits, and then replaced them with a computer. You would basically be converting the fighter spacecraft into a roving missile bus, and removing the logical justification for the existence of fighter spacecraft altogether. But it would be overwhelmingly more effective. Even over and above the fact you can send them on the equivalent of a suicide mission, since nobody living is onboard.
In other words, hard-science stories are far more likely to have drones in lieu of manned fighters.
If you are an author, try not to think about Burnside's Zeroth Law.
3D artist Scott Halls has made an amazing website illustrating technical information about Peter F. Hamilton's Night's Dawn trilogy. Above are the "Combat Wasps", which are a sort of armed drone. Left to right are the Kinetic Harpoon, Electronic Warfare, Fusion Torpedo, and Particle Beam Cannon Wasps. You can read all the details here.