Weapons: AKVs and Effectors.

In the last couple of blogs I have considered some of the weapons available to spacecraft in TS. I have even suggested some new systems. All of these weapons have been relatively short-ranged. One of the features of space warfare will be that the enemy will often be visible at very great ranges.

An modern astronomical infra-red sensitive telescope can see a heat source equivalent to the space shuttle’s main engines out at the orbit of Pluto (about 40 AU). We can assume a future space warship will carry telescopes at least equal to the best used by modern astronomers. Such instruments will cover a large slice of the electromagnetic spectrum including visible, infra-red and ultraviolet light as well as radio, gamma and X-rays. A spaceship using its engines will be visible to anywhere in the solar system where there is a clear line of sight. How far away will a ship be visible if it is coasting? My sources differ on this but this estimate suggests 4% of an AU, or about 20 light-seconds. If the spaceship is moving at 1% of light speed it will take just over half an hour to travel this distance. At 11km/s it will take over 6 days. In other words, an enemy has plenty of time to prepare for an approaching ship. Detection range of a coasting spaceship may be even greater than the 20 light-seconds one source suggests.

 If, by some wondrous means, your ship was totally non-reflective it is still likely to appear as a darkspot at some wavelength range as it passes before stars and other objects. The same problem occurs if you could somehow cool one face of your ship to ambient temperature.

Stealth requires something to hide in or behind. In the vacuum of space there is nothing, so there is no stealth in space. While space is very big, it is also very empty and cold, making a ship or any other object visible if you look for it in the right place. Any spacecraft is going to appear warmer than its background. Even if a ship was perfectly insulated it would have the problem of finding a way to shed the heat its systems and crew will naturally produce.

An engine flare observed 40 AU away is actually an event that happened more than five hours ago. This is the time it will take visible light, infra-red or other electromagnetic radiation to travel this distance. There may be considerable difference between where a ship actually is now and where it was observed.

The vast volume of space will probably mean that active sensor systems such as radar will only be useful if you already have a pretty good idea where the enemy is. Transmitting radar pulses over a wide area will be a pretty good way to let the enemy know where you are so the active systems used will probably be highly directional tight-beam radar, lidar or maser systems. There may be no true stealth in space, but drawing attention to yourself and telling the enemy exactly where you are is still not prudent. It is likely a warship will deploy a sensor drone for any active detection duties.

Passive systems such as multispectral high-power telescopes and detectors will probably the primary means of initially locating the enemy. Computers will process images and look for objects with unnatural behaviour.

While full stealth is not possible ships will probably attempt to minimise their signature over as broad range of the spectrum as possible, making it harder for weapons to lock onto them.

Whilst detection cannot be avoided strategies such as misdirection and deception will be used to avoid identification and targeting. Their behaviour may try to mimic natural celestial bodies, so if they are seen they will be mistaken for objects such as wandering asteroids or friendly craft. In some science-fiction systems small ships use planetoids as heat sinks or hide in the space junk accumulated at the Lagranian points. Courses that pass behind celestial bodies or in front of strong EM sources like the sun may also be used where practical. An enemy will not see you if he does not bother to look in your direction.

Spacecraft may detect enemy targets hours, days or even weeks distant. The short ranged energy and projectile weapons described previously in this blog cannot be used to engage such targets. Some form of long-range missile will be needed.

One analogy for space combat describes it as resembling two nuclear submarines on opposite sides of the ocean duelling with ballistic missiles. The important caveat here is that a submarine’s primary defence is its ability to hide, which is not generally an option for spacecraft.

Below: Wasp Drones from Silent Phoenix.

The space combat missile is likely to be a very sophisticated device. The distinction between a missile and a drone becomes blurred here and essentially the terms become interchangeable. In Transhuman Space the major weapon systems for spacecraft are the Autonomous Kill Vehicles (AKV). AKVs are unmanned spacecraft armed with laser and/or coilguns that use these weapons to engage enemy vessels at close range. AKVs will also ram targets if necessary. Rogue AKVs left over from a war years before pose a hazard to shipping, attacking vessels their outdated IFF does not recognize. These rogue AKVs are sophisticated enough to maintain and supply themselves by salvaging other spacecraft.

TS AKVs vary from 30-300 tons mass, with 100 tons being typical. Where the number of AKVs carried by a larger craft is given in sourcebooks it is usually only three or four. Other entries do not specify the number carried but describe hanger bays of only 200-1,ooo tons capacity. Large TS spacecraft do not seem particularly well equipped for sustained combat. Obviously it is in a commander’s best interests to conserve and reuse his AKVs if possible. An AKV would need to retain at least half of its delta-V for a possible return trip. If it is decided to sacrifice the AKV the excess delta-V can be used to boost ramming speed.

It seems logical that the AKVs be supplemented by lesser forms of long-range missile. I will call these “effectors”.

The missiles that we are most familiar with are long aerodynamic shapes that generally fly towards their target until their fuel burns out. A typical effector drone is a barrel-shaped object that may be the size of a small car or bigger than a bus. Its shape makes it easier to store and handle within the warship. Conical and spherical variants are also known. In space combat an effector may take hours or even days to reach its target and may fly sophisticated courses, exploiting local conditions for sling-shot orbits or cover. Essentially the effector is a robot spacecraft on a one-way trip. The missile has several advantages over a manned craft. It will have a greater G tolerance so can use manoeuvres and tolerate accelerations that a manned craft cannot. Unlike the larger and more expensive AKVs it is not expected to be reused and a warship can carry a useful quantity. It also does not need to save fuel for the return trip and needs no life support resources so can be smaller and faster.

Effectors do not generally have launchers or missile tubes. Drones are stored in any available unpressurized cargo hold or hanger. When it is time to fire a drone the cargo handling system simply carries one to the nearest hatch and releases it. The effector’s secondary propulsors push it away from the hull until it is far enough away to activate its main drive. As it accelerates away it will unfold like a flower to reveal sensor masts, radiator wings and tower-mounted attitude jets. Since a target may be hours or even days away this seemingly leisurely way of launching is not a significant delay. For larger effectors might be carried clamped to the outside of the hull, as some AKVs are carried.

Once the effector has reached and located its target it must find some way to harm it. The simplest option is to simply crash into the target.

"An object impacting at 3 km/sec delivers kinetic energy equal to its mass in TNT."

When the velocity of an object reaches 3km/sec its kinetic energy becomes equal to the explosive energy of an equal mass of TNT. This is an exponential relationship in that at double this speed the object will have four times the energy, at triple nine times and so on. An object moving at 7 miles per second Earth escape velocity has about the energy of the explosion of fourteen times its mass in TNT so any impact will have a considerable effect. Kinetic energy continues to increase with increases in relative velocity. At relative speeds of over 190km/sec kinetic energy of two objects impacting begins to exceed that of a nuclear weapon of equivalent mass. The problem here is that of actually hitting the target given the speeds of the objects involved. Doubtless, however, if its other offensive systems fail an effector or AKV will attempt to crash into a target.

Nuclear warheads are an obvious choice for a missile, although combatants in TS are wary of escalating to the use of nuclear weapons. The absence of atmosphere in space means that the blast effects of a nuclear weapon will be greatly reduced and the majority of the warhead’s energy will be converted into X-rays and gamma rays. A nuclear explosion in space has been described as being a momentarily brief, very bright flash without the fireball and billowing clouds so beloved by special effects departments. The damage range of a nuclear explosion in space is likely to only be about a kilometre in radius. Within this distance the damage will be considerable but getting a warhead to within a kilometre of a target moving at interplanetary velocities may be problematic. Since an explosion is a spherical event increasing the size of the warhead only offers limited returns. A warhead ten times more powerful only increases the effect area by about two and a half times. More practical may be to fire a number of smaller warheads in a pattern and hope one will get close enough.

The lack of atmosphere will also greatly reduce the potency of conventional explosive warheads too. An explosive warhead that makes contact with a target or penetrates the hull will do considerable damage but proximity detonations will have only limited effects.

The effector or AKV may have its own laser systems and other directed energy weapons that it can use to fire on the target from relatively close range. Effectors are well suited to the application of “bomb-pumped laser” systems. These are weapons that use the detonation of a nuclear or non-nuclear device to provide power for a brief, intense burst of directed energy such as an X-ray laser. Transhuman calls these “Teller mines” after the physicist Edward Teller. The X-ray Laser Munition Pack (XLMP) fired from an AKV or larger ship’s coilgun consist of a number of these devices with a total mass of 9.5 tons.

“The exception is the X-ray laser warhead (“Teller mine”), a stand-off weapon which detonates a nuclear bomb and uses its radiation to energize multiple coherent X-ray beams. The bombs are kicked out a few miles from the firing craft by electromagnetic coilguns. coordinated by communications lasers. and directed using the main vessel’s sensors. where they deliver a short-ranged but lethal one-time punch.” [TS 3e p.10]

A bomb-pumped laser device will destroy the firing platform but this is not a concern if the system is mounted on a disposable drone or missile. Included in this class of weapon is the shaped nuclear charge, a weapon that focuses the majority of its energy into a cone-shaped discharge of X-rays and plasma that is aimed at the target. An effector might carry a number of sub-munitions armed with bomb-pumped DEWs. During the final attack phase these would spread out and fire upon the target from several directions at once. Possibly the sub-munitions would use communication lasers or some other system to coordinate their attack between themselves.

An interesting variant of the above is idea is to use Lithium Deuteride in a projectile and the energy of a high velocity impact used to compress it into an exothermic reaction. I like to think this might have been what the “Nuclear Pellet Launcher” mentioned in the TTA series of books was.

Electromagnetic pulse weapons are another attack option, although for these to be useful they must have a wider effect area than a conventional nuclear weapon. An EMP weapon could be used to blind or disrupt a target’s systems so they would be are most useful if used to soften the target up for more destructive attack systems.

One of the most cost-effective means of attacking spacecraft might be a Victorian idea, the shrapnel warhead. As stated above, at relative speeds exceeding 3km/sec a solid object has greater kinetic energy than the explosion of the equivalent weight of TNT. A shrapnel warhead may contain a small bursting charge and a mass of solid projectiles such as 2"/ 3lb cast iron balls. Cast iron balls seem the sort of thing that could easily be manufactured in a free-fall environment from an asteroid or scrap. One can easily envision a large spacecraft manufacturing its own.

An exploding shrapnel warhead would create a cloud of shot over a large area, which may exceed the effect area of a nuclear weapon in volume. The effect area would also be more persistent. Warheads could be detonated so that the sub-projectiles either hit the target or the target flies into them. The small size and number of balls would make it difficult for a laser defence system to destroy them all. A laser system would have to vaporize each ball since they would still be a threat if molten or broken up. An interesting idea would be to pack the balls in sand or carbon dust to form a cloud that would interfere with laser fire. The shrapnel warhead itself would be rather robust. A nuclear explosion is a complicated event to initiate and relatively minor damage to the nuclear device might render it inert. The shrapnel warhead is mainly inert metal so would be more tolerant to damage from defensive fire. If the warhead is broken up or detonated the scattered shot would still pose a hazard to the defender.

The tungsten pellet Kinetic-Kill Munitions Packs (KKMP) used by AKVs and larger ships in TS are similar in principle to the shrapnel warhead but on a larger scale. The ten-shot KKMP needs to be launched from a coilgun, has a total mass of 9.5 tons, and occupies 250 cubic feet. Each shot therefore launches nearly a ton of tungsten pellets. [TS 3e p.188 and 197]

The shrapnel warhead and KKMP are not the only forms of kinetic weapon possible, of course. The effector may pack a number of larger short-range kinetic kill missiles, effectively the offensive equivalent of Kirklin mines. These might be designed so that if hit by a defensive laser they break into large fragments and/or release smaller “child” KE missiles so continue to be a hazard to the defender. 

Probably an attacking effector or AKV will use a mixture of offensive systems, releasing a number of sub-munition warheads of various types while attacking with directed energy and jamming systems. Larger models of drone or AKVs may also utilize railguns as armament, allowing them to attack if they pass within a few kilometres of their target

Typically an AKV can only carry a single, ten-shot munition pack and launch it from a coilgun mounted to be forward firing. A railgun is a much lighter system and can be turret-mounted. The railgun gives the AKV the capability to engage multiple targets. Railguns are capable of accelerating a projectile at phenomenal speeds. A railgun round that penetrates a ship’s hull is likely to perforate a number of internal compartments as well, possibly punching out the other side of the vessel. Smaller targets hit by a railgun will be shattered, pulverized or even vaporized. A hit from a railgun can be devastating but in a vacuum a miss of a few inches will have negligible effect on the target.

A railgun round may be accelerated at 20,000 to 60,000g and such forces pose considerable problems in creating guidance systems suitable for a railgun rounds. Whether these challenges will be solved by the TS-era, or will actually need to be addressed remains to be seen.  It can be assumed the majority of railguns use unguided rounds. Acceleration forces also make it problematic to use unstable compounds such as explosives in railgun rounds. When a projectile’s velocity exceeds 3km/s the need for an explosive component is debatable. Railguns generally use solid shot or “slugs”, either of hardened steel or steel with a tungsten or depleted uranium core. A 3" calibre railgun slug or shot for a 5" (127mm) railgun masses about 33 lb. Each round is acutely pointed but this point is covered by a cap of softer material (above) that reduces the chance of a round glancing off armour. AKV railguns use the same ammunition as other railguns but tend to be simpler than other models since they are likely to only be used for a short duration. Waste heat production and excessive wear are less of consideration on such models. A railgun can be refurbished if the AKV survives its mission. Instead of the 5" railgun some AKVs and smaller vessels mount a 3" railgun that fires a 57mm projectile of 15 lb mass. The 3" railgun permits more rounds to be carried within a given volume.

Below is a tentative proposal for such railguns, based on the rules in Spaceships (4e). Railguns are typically turret mounted. 

Weapon	d-Damage	sAcc	Range	RoF	Shots	Rcl	WPS	Notes
3" Railgun	6d x 2(2) x V	-7	S	[p.58]	50	3	15lb 1/133t	[1, 2]
5" Railgun	3d x 7(2) x V	-7	S	[p.58]	150	3	33lb 1/60t	[1, 2]

[1] d-Damage is multiplied by relative velocity (V) of combatants and subject to an armour modifier of (2). Minimum relative velocity for these railguns is 3 mps.

 [2] Rof value varies with turn length and weapon type. See p.58 of Spaceships (4e) for Rof.

The enemy may be well aware that an effector or AKV is on its way and have several days to prepare. He may launch an effector or AKV of his own to destroy the incoming threat. This suggests that the attacking vessel may have their own defensive systems and the defensive vessel counters to these. The effectors and AKVs will doubtless use ablative armour, evasion and other defensive methods to increase its chances of reaching the target.

An effector will have to be a fairly sophisticated robot spacecraft in its own right and it is highly likely that some may be retasked spacecraft. In this article on “Killer Buses” commercial, obsolete or surplus spacecraft are used as missiles, echoing the use of fireships and hellburners during the age of sail and the use of explosive-packed ships in later conflicts. As has been explained already, such a ship does not even need to be filled with explosives to make it a weapon. Its mass and velocity will make it lethal enough and even if it is destroyed the fragments produced may remain a hazard to the target. It is feasible that such a ship will contain sub-munitions and interception counter-measures. The distinction between ship and missile becomes increasingly blurred as we consider space warfare. One can envision a captain desperately launching his lifeboats and shuttles to destroy an incoming threat           

Particle Accelerators and Coilguns.

Many of the space warships in Transhuman Space (TS) include neutral particle accelerators as part of their armament.

 In TS 3e ship-building rules particle accelerators were brought in 50 foot increments, the longest known example being 400 ft long. One of the reasons for the popularity of cylindrical hulls was that a linear particle accelerator could be installed running down most of the longitudinal length of the hull. This arrangement only allows the particle weapon to fire into the ship’s forward arc. Spaceships 8 design rules represent this by treating particle weapons as fixed mounts on the forward hull. While the weapon extends most of the length of the vessel it is generally not massive enough to count as a spinal mount. If you had a ship that expected to get chased a lot it might be prudent to build a vessel with a rearward firing particle weapon! The Archangel-class SDV [Spaceships 8 p.29] design has a pair of particle beams but both are mounted for forward fire. Legally only warships are permitted to mount particle accelerators. In Spaceship 8 rules particle beams can only be mounted on ships of SM+8 or larger and must be major, medium, or spinal batteries, installed as fixed mounts (a +2 to hit) with either the rapid fire or very rapid fire options. The Salahudin Samboja [Spaceships 8, p.31] appears to be an exception, mounting a 3GJ weapon, the maximum size of non-rapid major battery weapon for the SM+10 hull.

The Atomic Rockets webpage has some interesting discussion of the real word strengths and limitations of particle beams as weapons. Particle beams cannot be focused as tightly as a laser, giving them less range than a laser of equivalent power. On the plus side the particle beam has greater penetration. A laser beam stops on the surface of a target and attempts to burn through. A particle beam will penetrate deeper, causing local heating and also producing levels of radiation dangerous to both electronic and biological systems. In Transhuman Space laser weapons are limited to 300MJ or less. Particle beams are available in the GJ range.

The requirement for a forward mounting raises some interesting questions. The spacecraft can only fire its particle beam at a target the hull is pointing towards. Of course, in space combat a ship can point in a different direction to the one that it is travelling in. Most of the ships in TS appear to be “tailburners”. They have one large engine at the end of the vessel. Presumably they decelerate by pointing the drive forward and change course by orientating the drive in the appropriate direction. Suppose such a ship is heading “north” and wants to head “east”. The ship would reorientate so that its drive is pointing “northwest”. Thrust from the drive would cancel the northward motion and move the ship eastward. It should be obvious that during this process the forward-firing systems of the ship can only engage targets to the “south-east”. The ship cannot fire and manoeuvre at the same time! This is why I have proposed designs of military spaceship with multiple major thrust ports, permitting changes of direction or speed without reorientation.

Another consideration for the fixed mount is one of accuracy. When a target is thousands of miles distant the margin of error will be in terms of fractions of a degree. It seems unlikely that a ship hull of 10,000 to 30,000 tons can be orientated with sufficient finesse. The particle weapon itself will weigh 20-40 tons for every 50ft of length, [TS (3e) p.182] so sufficiently fine movement of this mass is unlikely to be practical either. The spaceship will need some mechanism to influence the path of the beam magnetically. The particle beam is neutralized just before it leaves the “muzzle”. Beam trajectory will need to be set while the beam is still in its charged state.

Coilguns are another weapon found on some large TS spacecraft. In TS 3e all coilguns were 333mm [p.181] and fired “munition packs”. A Kinetic Kill Munition Pack (KKMP) held several canisters of tungsten pellets. A X-ray Laser Munitions Pack (XLMP) had canisters holding several nuclear bomb-pumped X-ray laser weapons [TS 3e p.102, p.188]. Both types of munition pack massed 9.5 tons, occupied 250 cubic feet and held 10 shots [p197]. (This implies each coilgun round is more than 26ft/8m long! Perhaps each shot is a fusillade of smaller canisters.)

In Spaceships 8 coilguns are considered to be equivalent to electromagnetic guns and their power varies. AKVs carry coilguns equivalent to 10cm or 12cm guns. Larger vessels carry guns of 14 to 24cm equivalence, representing that larger vessels can mount more powerful coilguns that can fire the same munition packs at greater velocities. Potentially a coilgun as long as the ship could be created. These may in fact be the systems represented by fixed forward mounts of medium size or greater. Despite this, coilguns are relatively low velocity weapons in the context of space warfare and are thus limited to shorter range engagements. Minimum relative velocity modifier is 2 mps. See Spaceships 4e [p.58, p.68] for effects of 10-24cm electromagnetic guns and space combat. (Note that the p.68 table is subject to a correction in Spaceships Errata. dDamage for 10cm-24cm is actually 3dx5 - 6dx6)  Spaceships 8 [p.9] has rules for X-ray laser munitions. KKMPs are treated as conventional 10-24cm rounds for damaging purposes with no armour modifier. Each coilgun bay contains one munition pack giving 10 shots. It is up to the GM as to whether a coilgun bay can be reloaded during a combat. Given that each munitions pack weights nearly 10 tons this will only be practical on larger spaceships if allowed.

Defensive Weapons for Military Spacecraft.

In my previous post I commented that a large military spaceship was more likely to look like the Graf Zeppelin than the USS Missouri. Another reason for this statement is that the spaceship will not be brisling with gun turrets and long-barrelled guns.

The actual laser weapons will be mounted deep inside the ship where they are better protected and can be more easily maintained. The external turrets on the ship’s surface are in fact gimbal-mounted reflectors. The reflectors are linked to the laser weapons by a system of light ducts and mirrors that transmits the laser beam to them for final focusing and direction. It has been suggested that a ship only really needs a single laser weapon connected to two turrets, one of each side. One can fire while the other acquires a new target. For a large spacecraft some redundancy is prudent. The larger ship designs I have illustrated below have two or three internal laser batteries attached to eight turrets, one on each corner of the ship. By such an arrangement at least four turrets are engage targets at once in any direction. This is also consistent with the options given in Spaceships (4e) and Spaceships 8. The two to eight main laser turrets will be supplemented by smaller, shorter-ranged rapid fire and very-rapid fire laser systems. It is quite possible that laser-generators of differing outputs could share reflectors.

 

 

Lasers and other directed energy weapons are limited in range and their primary function is defensive. Even if a laser or other directed energy weapon can destroy a target at long range the complications of actually hitting the target are going to limit the practical range of such a weapon to a light-second or less. In the Transhuman Space (3e) p.102 it is stated that the maximum practical size for a laser mirror is 9 feet giving a practical focusing range of 5,000 miles. Even at these ranges the reflector turrets will need to make adjustments of fractions of a degree in accuracy. This is another reason why laser batteries are internally mounted to keep the mass of the turrets low.

A ship’s laser systems might be complimented by other weapon systems such as Kinetic Anti-Drone Missiles or KADM. These are also known as Kinetic Defence Missiles (KDM). Each KADM is about the size and shape of a football so they are spoken of figuratively as “cannon balls”, “pinballs” or “bowling balls”. The term “carronade” is also often used for the launch system for the KADMs. KADMs are compact, low-cost weapons and a warship may have several magazines containing hundreds of KADMs. The ship may include facilities for manufacturing KADMs.

 The KADM magazines are connected to ports on the ship’s surface by magnetic tracks which to some are reminiscent of those on a pinball table or bowling alley. The last section of the track is a linear accelerator system that launches each KADM at a very high velocity. Each KADM is a chemically-fuelled guided missile capable of manoeuvre and further acceleration. The KADMs speed and mass give it a tremendous quantity of kinetic energy and a single hit can easily vaporize an attack drone or many larger craft. Carronades and their rounds are also known as “smashers”. KADMs are also sometimes used offensively. When in low orbit KADMs are fired in an orbital path to engage ships hidden by the planet’s horizon.

Carronade KADMs may be supplemented by larger, longer ranged and more sophisticated anti-missile missiles along the lines of the Kirklin mines proposed here.

KADMs and Kirklin mines are not official TS space warfare weapons, but worth considering for TS or other hard science space settings.

Some TS spacecraft mount coilguns or electromagnetic guns. The railgun described next is a related but distinct weapon and recommended if you want a real gun turret on your spacecraft!

Railguns are another potential defensive weapon for spacecraft. The railgun fires “shot” rather than X-ray or tungsten-pellet munition packs. Railguns are capable of accelerating a projectile at phenomenal speeds. A railgun round that penetrates a ship’s hull is likely to perforate a number of internal compartments as well, possibly punching out the other side of the vessel. Smaller targets hit by a railgun will be shattered, pulverised or even vaporized. A hit from a railgun can be devastating but in a vacuum a miss of a few inches will have negligible effect on the target.

A railgun round may be accelerated at 20,000 to 60,000g and such forces pose considerable problems in creating guidance systems suitable for a railgun rounds. The majority of railguns therefore use unguided rounds. Acceleration forces also make it problematic to use unstable compounds such as explosives in railgun rounds. When a projectile’s velocity exceeds 3km/s the need for an explosive component is debatable since its kinetic energy already exceeds the energy of an equivalent weight of TNT. Railguns generally use solid shot, either of hardened steel or steel with a tungsten or depleted uranium core. Such rounds are relatively easy to fabricate with shipboard facilities. A 3” calibre railgun “slug” or “shot” for a 5” railgun masses about 33lb. Each round is acutely pointed to improve penetration but this point is covered by a cap of softer material (above) that reduces the chance of a round glancing off armour. Reflecting their naval ancestry, most railguns have a calibre of 5”/ 127mm. The “Aliens: Colonial Marines Technical Manual” suggests an incendiary railgun round where an inert material is vaporized by impact to form a directional plasma. Waste heat production and excessive wear are other factors the railgun designer needs to address. Instead of the 5” railgun some AKVs and smaller vessels mount a 3” railgun that fires a 57mm projectile of 15lb mass. The 3” railgun permits more rounds to be carried within a given volume.

As an unguided, slower than light weapon the railgun round has a very short effective range against fast-moving targets. Aliens: Colonial Marines Technical Manual claims an effective range of just 100km for the Sulaco’s railguns. In TS the railgun is often one of the last lines of defence. While some capital ships mount railguns they are more common on smaller vessels such as frigates and gunboats. Railguns are useful as ground attack weapons and against slower, larger targets. The railgun may become an icon of future gunboat diplomacy. It is one of the few spaceship weapons that can be visibly trained on an enemy to intimidate them. It is also one of the most practical means to put a warning shot across the enemy’s bows. Laser and particle beams are invisible in a vacuum while drones are a resource not to be squandered.

Below is a tentative proposal for such railguns, based on the rules in Spaceships (4e). Railguns are typically turret mounted.

Weapon	d-Damage	sAcc	Range	RoF	Shots	Rcl	WPS	Notes
3” Railgun	6d x 2(2) x V	-7	S	[p.58]	50	3	15lb 1/133t	[1, 2]
5” Railgun	3d x 7(2) x V	-7	S	[p.58]	150	3	33lb 1/60t	[1, 2]

[1] d-Damage is multiplied by relative velocity of combatants and subject to an armour modifier of (2). Minimum relative velocity for these railguns is 3 mps.

 [2] Rof value varies with turn length and weapon type. See p.58 of Spaceships (4e) for Rof.

Thoughts on Military Spacecraft: Part One.

Any discussion of military spacecraft assumes there will be some reason or need to project military force off-world. In science-fiction we often see spacecraft engaged in great space battles or conducting planetary invasions. I suspect that both of these situations will in reality be rather unlikely.

One reason for this is military spacecraft are likely to be very expensive. Currently even the richest nations can only field a handful of aircraft carriers. How many large spacecraft a future power can field will depend on how important space warfare is to them and the resources they have but it seems likely the numbers will be in the dozens rather than the hundreds or thousands. The great space armadas we see on the movie screen seem unlikely. Space battles are likely to be more intimate affairs, if the capital ship is to be risked at all. As an aside, the variety and cost of equipment any spacecraft would need on board is staggering! Even a relatively simple asteroid belt craft may need a mortgage of several generations to pay for it.

For easy visualization let us consider a capital ship the size of a Nimitz class aircraft carrier. The Nimitz is just over 1,000ft or 330m long (a sonic second!). In GURPS Spaceship (4e) terms this would be SM+13, massing 300,000 tons. The Nimitz can carry 5,000-6,000 personnel and around 90 aircraft. The capital spacecraft will probably need a greater proportion of its capacity devoted to propulsion, life support and storage. On the other hand it will have a greater degree of automation and probably need less crew members to actually run it. A generous but reasonable estimate would be a ship that can accommodate about 3,000 personnel in addition to the crew. That sounds a lot but in military terms that is only three or four battalions of ground troops. That is not a very big force to invade a reasonably populated planet, no matter how advanced your weapons are. Troops are also going to need vehicles, engineering equipment, artillery, support and transport aircraft/spacecraft and a whole host of other stuff that is going to take up space in the capital ship. A handful of Nimitz-sized ships with a few thousand men in each will not be enough. Invading a planet will probably require hundreds and possibly thousands of such ships, resources that most combatants are unlikely to have. The planet being invaded will also have a home team advantage. Its forces will be many times larger. If it is a reasonably advanced civilisation it can build surface to orbit weapons far more powerful than anything that is mounted on the invading ships.

The spaceships available to the major powers in Transhuman space are only about half the length of the Nimitz-sized craft described above. In game terms they are Sm+10 or SM+11, 300-450ft long or less and mass 10,000-30,000 tons. We are told that Space Control Vehicles (SCV) carry between a battalion and a platoon of troops and Space Dominance Vehicles (SDV) less than a platoon. Of course, in TS many of the infantry will be cybershells that require less accommodation and resources than human/ parahuman/ bioroid soldiers. An SDV or SCV may have more ground combat capability than the number of soldiers carried would at first imply. Large scale invasions still seem relatively unlikely, even when this factor is considered.

A more likely application of military power in space will be of various types of raiding. A small fleet of ships might be used to deliver a punitive strike or conduct a commando raid to acquire materials or information. Enemy merchant shipping may be a target for such actions. The days of gunboat diplomacy and privateering may return on the high frontier.

Another military mission for the military in space might be termed “order enforcement”. Ships will need to be inspected for contraband and distant outposts will need to policed for illegal activities. A law enforcement officer or inspector will need something to back-up his authority and this is likely to be a military unit. Many of these operations will require “boots on the ground” and face to face interaction so it is likely that infantry-trained personnel will be an important part of many future space operations.

In the space operas warships bristle with turrets and gun emplacements. In reality the space warship may look much more like a cargo ship for a very simple reason. Much of its capacity will be devoted to cargo space. The ship will look more like the Graf Zeppelin than the USS Missouri. There may in fact appear to be little difference between a space warship and a merchant ship. This will be particularly true if it is seen necessary to provide freighters with some defensive armament of their own. The distinction blurs further when we consider that military vessels might be used to transport high value cargos. SCVs and SDVs may be supplemented by a third class of large military vessel, the Space Exploitation Vessel (SEV). The SEV features multiple cargo bays, and its mission can be varied by changing the contents of those bays.

GURPS Spaceships has the supplies needed for 500 man-days in space as massing one ton. When we start considering that spacecraft in TS may make voyages of several months duration it becomes apparent that even a single-person deep space ship will have to be quite large to accommodate all the needed supplies. A deep space war vessel is likely to be very large.

A spacecraft may need to operate away from base for weeks or even months of time. For long voyages the ship’s cargo space will be used for supplies and replacement parts. On a more aggressive mission many of the cargo bays will be loaded with ammunition instead. For a raiding mission many cargo bays will be filled with ground troops, cybershells, equipment and shuttle craft. Bays might also be loaded with fuel or reaction mass.

The cargo spaces of a spaceship may be used to carry large volumes of ice and water. As well as serving as a reaction mass water can be used as a heat sink. This suggests that a ship may include an extensive plumbing system to redistribute and circulate water as needed.

For many of their possible roles cargo bays will need hatches to the exterior. It follows that provision may be needed to pressurize or depressurize individual bays as required. In effect many of the cargo holds will be large-volume airlocks. Depending on their contents and role many of the cargo holds will spend much of their time depressurized. For a hold used as a magazine for attack drones it is logical to have the hold at ambient conditions with the exterior. This also minimizes the likelihood of fire or atmosphere loss if that hold takes battle damage. Holds containing perishables may also be kept in a vacuum and unheated.

The greater the cost of a military system the greater the incentive to make it perform multiple roles. Large spacecraft will be very expensive! The difference between an SDV and an SCV may in reality be more one of cargo than actual design.

The crew compliment for these ships would be surprisingly small for a ship so large. When each crewman or passenger needs months of supplies and life support it is more efficient to use automated systems whenever possible. In THS the Salahudin Samboja-class SDV is fully automated. For many other military spacecraft the role of the crew may be more along the lines of directing or advising the ship’s AI rather than actually operating the systems.

In Transhuman Space the sphere configuration of spacecraft is mainly used for unmanned defence satellites and AKVs. Larger spherical ships are known but relatively rare. I believe a sphere would be a useful shape for a military spacecraft. Ball-shaped spaceships are relatively rare in fiction. Heinlein’s “torchships” were shaped like a top: a hemisphere joined to a cone with the drive at the point.

One possible configuration for a spherical ship would have the engines being built in the centre of the sphere and four exhausts radiating outward in a tetrahedral arrangement. By using the exhausts in varying combinations the ship can change direction without needing to reorient. Construction of such a ship in orbit would be relatively simple. You position the engine and then build outward in every direction.

Below: Spherical ship with retractable radiator arrays from the game "Silent Phoenix".

A sphere has a number of other advantages. A compact shape like a sphere takes less energy to reorient than an elongated one. Its ratio of surface area to volume is low so its surface will absorb less heat from attacks such as lasers. On the negative side the shape loses built up heat less readily. The surface area ratio also means you can have a thicker layer of armour or shielding for a given mass. The armour layer can also be more uniform, with a lesser chance of weaker areas.

Generally in science fiction it is assumed the crew quarters should as far from the drive/ reactors as possible so a cylindrical shape is a more common configuration. The long length of the cylinders is also used in TS to facilitate the mounting of very long neutral particle accelerator (NPB) weapons. Another feature of the Transhuman Space cylindrical craft is that some of them are “spikes”. They have pointed noses to increase the chance of incoming fire being deflected. Like a Mediterranean war galley the ship attempts to keep its nose towards the enemy while preferring to land attacks on its enemy’s flanks. As well as spheres, spikes, tops and cylinders there are a number of other possible shapes for warcraft. Cones might be suitable for smaller vessels such as attack drones. Rhomboids, trulloids and ovoids are also possible.

Below: Frigate ship from the game "Frontiers".

The positioning of the control room also needs some thought. Does it really need to be at the front of the ship, the region most likely to be exposed to enemy fire? Protection of the crew from radiation seems a more important priority. This suggests the control room should be deep within the ship’s body. It also suggests that the control room is located close to the living quarters and sickbay to make the most efficient use of radiation shielding.

Depending on the drive system used you may want the engines as far away from the crew as possible. Spaceships in films tend to place gigantic engines at one end of the ship. These all seem to thrust in one direction so if the ship wants to slow down it would have to flip over and point its engines “forward”. This is the mechanism used in TS, which would obviously cause problems when it came to aligning the forward firing particle beam weapons with a target. An alternate configuration would be to give the engine a cluster of nozzles in a variety of directions including forward. Such an arrangement could pull the ship as readily as it could push it and the ship might spend half its time moving engines first. Using such an arrangement would mean not having to yaw the main body more than 45 degrees for any course change. While I have drawn the illustration with rocket nozzles this configuration could use other systems such as a cluster of pusher plates.

A variation of this concept might resemble a medieval mace in appearance. The “head” would be the drive module with thrust ports orientated in various directions and the “shaft” would be a cylindrical body for the rest of the ship. The illustration shows a large radiation shield placed between the drive module and the main body.

The illustration below combes the concept described above with the concept of a spherical hull. The smaller sphere is the drive module and three of the thrust ports are visible. The red spots on the main sphere represent the positions of laser weapon reflectors. The geodesic construction would allow for easy repair of battle damage from standard components.

Transport-Bombers.

Sometime after the First World War the roles of transport and bomber began to be met by differing designs of aircraft. There were exceptions to this general trend, of course. The Bristol Bombay was designed with a dual-role in mind. Some Ju-52 transport aircraft were fitted with bomb-bays so they could serve as interim bombers. It was found the bomb-bays were also useful for loading or dropping certain cargos too! In general, however, transports and bombers were different aircraft designs and the use of transports as bombers was usually an expedient.

During the Vietnam war the two bloodlines began to merge again. Many transport aircraft were now fitted with large rear ramps that could be opened in flight. This allowed aircraft such as the C-130 to drop bombs such as the “Daisy Cutter” which were far too large for conventional bombers. Smaller bombs could be loaded onto pallets and pushed out the rear ramp. A C-130 could accommodate eighteen 1,000lb bombs or twenty-four 750lb. The increasing use of guided bombs and stand-off weapons increased the potential of transport aircraft as bombers.

Another product of the Vietnam war are transport aircraft used as gunships. Modern examples use a combination of direct-fire, guided missiles and free-fall ordinance. Some even have an air-refuelling role too.

The Russian AN-72 transport aircraft is also used in a patrol role. Bomb racks are fitted to the cargo area ceiling, above the retractable ramp. Gunpacks and rocket pods are also fitted to the exterior. Il-76s have also been fitted with bombs, the stated intention being that the bombs can be used to clear overgrown airfields so the aircraft can land.

This is a trend that is likely to continue into the world of TS. Military aircraft are expensive so it is attractive to make them as multi-role as practical. Airdrop capability is an attractive option for some civilian missions too, allowing much needed supplies to be delivered to inaccessible areas. During an emergency such as a forest fire it is obviously an asset if many of the locally available aircraft can be pressed into service as water-bombers.

Advances in technology have also had an effect. Many weapons systems have quite sophisticated guidance systems and therefore can use relatively simple delivery systems. A transport-bomber only needs to fly to the right location and release its cargo. Often this will not need to be particularly close to the intended target. Keeping to commercial flight paths and mimicking civilian traffic will be a common strategy. The load delivered may not be a conventional bomb or missile. Small, robust cybershells that can be packed in a 2000lb glide-bomb body [THS3e p.101] or dropped directly from aircraft [Deep Beyond p.119, Shell-tech4e p.18] are available to many militaries and can be used for missions such as surveillance, reconnaissance, sabotage or assassination. Such units can be re-supplied with bomb containers filled with munitions and other equipment. An aircraft that can serve as a water-bomber can also deliver other chemicals or materials.

The line between what is a military transport aircraft and a civilian one will have become increasingly blurred. Superficially at least the same basic design may be used for both. The ability to land in unprepared areas or small spaces is as useful in some commercial applications as it is to the military.

The smaller aircraft will most likely be UAVs of around the size of a M-28 Skytruck or Avecen Jetpod. Rear doors and a ramp will be a standard fitting and an easily-fitted module will convert the aircraft for passenger transportation or a bulk liquid transport/ tanker role .

Some larger military aircraft will be based on civilian airliners/transports. As well as decreasing costs this permits an element of mimesis to be exploited.