In the original 3e Transhuman Space book (p.100) we are told:
“Conventional over the horizon artillery support is provided by rapid-fire. high-velocity electromagnetic cannon. as slower, indirect-lire rockets and missiles are vulnerable to point-defense weapons. Artillery rounds typically have satellite guidance or homing submunitions though dumb shells are also used in intense electronic-warfare environments.”
This is the first instance where the ideas on this blog may stray from what is canon (pun intended).
While an electromagnetic weapon might be able to fire projectiles at a higher velocity than a conventional gun or launcher, it is debatable as to whether this is an advantage for an over the horizon weapon.
The higher the velocity, the flatter the trajectory, which is not such a useful property for a round you want to drop over the horizon onto a distant target. Higher velocity will also make it harder to alter the trajectory and requires a faster, more sophisticated guidance system.
As was implied by my brief description of airstrike systems in a previous post, other systems may continue to be used, particularly for targets beyond that range of electromagnetic field guns.
Another post may deal with tactical battlefield systems.
Today I will restrict myself to description of a deep strike system.
A variety of systems may be available and other systems will be described in later posts.
One strategy to avoid air defences is to fly low, exploiting nap of the earth (NOE) techniques. This is particularly effective against line of sight systems such as lasers. Possibly the defender may use an airborne laser system for a “look-down, shoot down” defence but such aircraft will in turn be vulnerable to an attacker’s anti-aircraft systems.
On THS Earth, low-level penetration attacks are conducted by cruise-UCAVs.
As we will often find in THS, the cruise-UCAV is a mixture of familiar and different. A typical cruise UCAV at first glance does not seem that different from modern cruise missiles.
Low level flight places some practical restrictions on the design of an aircraft. Unless flying over the sea or very flat terrain, the undulations of the ground make speeds of more than 570 mph impractical.
There is little point in designing a cruise missile with supersonic capability since it cannot use it!
Subsonic speeds also help contribute to the stealth of the aircraft.
Low-level air is denser than at higher altitudes and this favours an aircraft with a smaller wing area to give a smoother flight. This is why cruise missiles have small stub-wings and can fly using body lift.
The cruise-UCAV not only looks like a modern cruise missile but is of a similar size. It is about 20 ft long and under 2 ft in width, allowing it to be launched from the various systems that were already in service.
Thus, other than a little more attention to stealth features, the THS cruise-UCAV looks very similar to contemporary  cruise missiles.
Internally the UCAV has a much more sophisticated guidance and sensor system and will probably be piloted by a LAI.
It may use ramjet propulsion rather than a turbojet.
Rather than a fixed warhead, the UCAV has an internal weapon-bay capable of carrying a wide variety of missiles or submunitions. The weapon bay can carry other systems such as reconnaissance packs, EW devices, cyberswarms, surveillance fluff/ dust, less-lethal weapons, chemicals and so on.
Fitted with air to air missiles, it can engage airborne targets.
The UCAV is designed to release its payload close to the target(s) and return to friendly airspace if possible. Most modern cruise missiles are seldom used at their full potential range so a device that can attack its target and then return for reuse is a logical progression.
Like a manned aircraft, the cruise-UCAV gives the option of aborting or redirecting an attack right up to the moment that the weapons are released.
The weapon-bay makes the cruise-UCAV a very versatile system.
It can fly down a road column, dropping a bomb on each vehicle it passes over. Over a clustered target such as a staging area, it can release all of its munitions at once.
In a previous post, I mentioned that robot combat systems can be hard landed by a glide-bomb type capsule.
A cruise-UCAV attack could bomb a target then deploy robot combat systems to mop-up, assess damage and hinder repair efforts.
The UCAV’s own sensors can also assess attack effects and use this information to customize follow-up attacks.
Ideally, the cruise-UCAV releases its weapons from outside laser engagement range but some mission profiles do not allow this.
Cruise-UCAVs have ablative surfaces to provide some protection from point defence lasers.
Cruise-UCAVs are launched from standard launching tubes mounted on ships, submarines or ground vehicles. Alternately they are dropped from larger aircraft.
Landing system varies with different designs. Some simply cut engine and deploy a parachute. Other designs land conventionally on a skid or belly-land on water or a special landing surface. Mid-air recovery by cargo aircraft is also practiced.
Cruise Missile Stealth Features
The cruise-UCAV can be modelled as a smarter, reusable version of a modern cruise missile. Based on contemporary examples, the weapons-bay can be assumed to have a capacity of 1,000 lbs and 28 cubic feet. Improvements in engine and avionics technology may free up more space inside a THS cruise-UCAV so the GM may allow capacity to be increased by 50%.