What are the classes of vehicles?

There are several classes of flying vehicles used in the books, and some never enter the atmosphere!

An airplane is any flying vehicle with fixed wings that takes off and lands conventionally.

An aeroplane is a distinct class of air vehicle, one that is capable of taking off and landing vertically. There is considerable overlap with the next category.

The smallest spacecraft are birds, which tend to be space-capable airplanes or aeroplanes with jet turbines for in-atmosphere flight and vacuum thrusters that take over when the air thins out.

The next largest category is spaceship. This encompasses anything that does not have wings but is still designed to enter a planet’s atmosphere and land, usually on a prepared surface.

Starship is a vast category containing any vessel equipped with a bridge generator or designed for repeated gateway travel.

Capital Ship is technically a variant of starship. It is usually only applied to the largest warships or the mega-yachts flown by the heads of dynastic corporations.

How is conventional spaceflight achieved?

Astrodynamics applies to all ships. The vehicles and vessels of the Apeilous make use of efficient fuels and thrusters but are still beholden to navigation within the established laws of physics, whether in a bridge or in orbit around a planet.

Any ship designed for both space and atmospheric flight will have both vacuum ion thrusters and either jet turbines or liquid fuel rockets. Small to medium size combat ships may have liquid fuel rockets specifically to increase acceleration beyond what an ion thruster can achieve.

What is a powered orbit?

If thrust gravity is required while a ship is in orbit around a celestial body, and enough fuel is on hand, a powered orbit is employed. To achieve this, a ship is typically pointed inward to the planet and accelerated both in the circumferential and radial directions into an orbit far faster than a standard free-fall orbit. Entering a powered orbit requires a ramped attitude change and continuous thrust during and following the maneuver.

While an equal amount of fuel would be burned by slowing the ship down and maintaining altitude, this is a rare occurrence. The rationale is the consequence of a loss of thrust. In an exoatmospheric hover, system failure would put the ship into a freefall into the atmosphere. In a powered orbit, system failure results in, at best, a sudden course change to a large elliptical orbit. At worst, the ship is put on an extrasolar path. In both cases, the crew has time to remedy the error or be intercepted by emergency services.

How do ships travel between star systems?

Bridges (also called tunnels, gateways, or jumps) are essentially shortcuts, constructed wormholes that link two locations defined by the energy of the creation process. A ship’s kinetic energy, the mass of the bridge seed, the energy it puts into the initial crushing of the bridge seed, and the energy put into the final opening phase all combine to determine both the real-space reach of the wormhole and its short-space length. The output location is determined entirely by the real-space length of the wormhole and the orientation of the construction process.

Errors in energy and orientation compound with distance; it is challenging to make an accurate bridge into a solar system from more than 10 light years away. Regulations require all ship-generated bridges to capital systems be done from less than 2 lightyears for the sake of arrival within specified time and location windows. Gateways (pre-established bridges) are the preferred method of travel.

See the deep dive into how a bridge is created after the next section.

How is fast long-distance communication achieved?

Bridges are inherently noisy phenomena. Radio signals rarely make it through a bridge intact, so long-distance communication is done by sending data on message rockets through small and fast bridges. With no organic payload, a message rocket can accelerate at its maximum possible thrust all the way through a bridge, arriving far faster than a crewed ship in an identical bridge. Due to their small size, message rockets can use smaller bridges. More energy can be diverted into making the short-space distance shorter or the real-space distance longer.

For example, a message rocket from the Outer Rim can reach the capital system of Leros in as little as half a day, provided waypoint stations are prepared. It would take an average crewed starship a week to make the same journey.

Let’s take a closer look at bridge travel

In the universe of the SVF series, long-distance travel is achieved by way of an artificial wormhole colloquially referred to as a bridge (or a jump, tunnel, gateway). No spacecraft has ever achieved a speed that could be considered a significant fraction of the speed of light. The highest speed recorded by a human-made object is about 20 % lightspeed, achieved by the warhead of the so-called Paris Weapon. Nearly all manned spacecraft travel at less than 500 kilometers per second (0.2 % the speed of light)—most space travel clocks in at less than 50 km/s.

A bridge can shorten the distance between two points, creating a detour through higher-dimensional space that can be any distance, in theory. In practice, the real-space and short-space length of a bridge is dictated by a long list of factors corresponding to the stages of making a bridge:

First, we need a bridge seed. A tungsten sphere is the most common form of a seed, though any metallic material can theoretically be used. Tungsten is used because of its density and relative abundance compared to other dense metals; it takes up less space for the same mass.

As a permanent installation, an orbital gateway will store bridge seeds in discrete sizes on board for use in pre-planned routes. A starship will store spheroids on board and machine them to the correct size once a bridge is planned.

The mass of a bridge seed determines the size of the wormhole. You can, in theory, squeeze a capital ship into a wormhole sized to a small shuttle, but it’s probably going to break up trying to enter or exit said wormhole. Regulations mandate a 1.5:1 ratio for bridge diameter to the maximum dimension of your ship. Wormholes are spheres, so this rule also applies to ship length.

Second, the bridge seed is placed at the center of the aperture of the magnetic array. On a gateway station, this is the very center of the ring. On a starship, the array is usually cylindrical, and the bridge seed is held about at the center, maybe offset to the open end.

The magnetic array is a collection of semi-toroidal soft magnetic cores wrapped in superconducting coils. Hundreds of Tesla of oscillating magnetic field is produced to crush the bridge seed to below its critical radius, the radius at which it becomes a black hole whose size and density are based on the mass of the bridge seed and the energy put into crushing it.

Wait, I said wormhole earlier; what are we doing with black holes? And won’t a black hole made from a basketball-sized tungsten sphere be very small? Yes and yes. For now, note that wormholes are far less dense than black holes.

Third, we now have an exceptionally small black hole located very close to our space station or starship. There is little time to act to achieve the next step. If we are too slow, the black hole will… fizzle out and disappear—dud bridge, as they say in the Navy. Let’s say everything went well, and the magnetic array successfully crushed the bridge seed past its critical radius at the exact moment the computer predicted it would. Now, we need to start feeding the teeny tiny black hole to transform it into a traversable wormhole.

The energy put into the transformation comes from a variety of sources: the magnetic field, the plasma we feed directly in, and the speed of the spacecraft through space (not just planetary orbital, but system orbital, cluster orbital, and galactic orbital, speed of galaxy through space, rate of expansion of space, etc.).

Over the next few moments, the black hole must be fed in an asymmetric 4D manner (in the direction we want to go but adjusted to account for the +1 dimension). This is hard to visualize, but luckily math doesn’t care how many dimensions we use in the calculation, so the computer handles this for us. Plasma is injected in from whichever directions the computer dictates.

Fourth, if we put enough directional energy in quickly enough, the black hole will transform into a wormhole. Recall that the wormhole’s size is based on the bridge seed mass and the energy to crush it (the starting state of the black hole). So where does all that energy we added go? The directional energy we fed into the black-hole-turned-wormhole determines its short-space length (i.e., how long the wormhole will be inside).

So far, we are just tunneling (backward?) through 4D space, with no end in sight. Once the short-space length is set, energy can be fed into the wormhole in the opposite direction (in 4D, that is). Consider the curve associated with exponential decay for all these energy injections. Short-space energy relates to distance by A^x -B while real-space energy relates to distance via A^(-x) - B. Making a short short-space wormhole requires a lot of energy, and making a long real-space wormhole also requires a lot of energy.

Fifth, we now have a wormhole with set lengths, but it is still contained within the magnetic field of the array used to create it. If we are at a gateway station, this is fine since the array is at the edge of the ring-shaped station, out of harm’s way. There are no further steps at this point. However, if we are on a starship, the wormhole is likely still in the cylindrical array and needs to be pushed out in front of the ship and allowed to expand fully. A quick reshaping of the magnetic field does this with ease, though this is often accompanied by a jolt to the ship’s occupants. The wormhole is moving through space with the ship, but it still has mass, and pushing against it, well, it pushes back.

Sixth, we’re done! Mostly. Wormholes are by nature unstable, especially if they’re empty, so we should get a move on and enter the bridge. Once the ship enters, the wormhole collapses behind it. This is not a complete collapse, as the entrance remains present, but shrunk down to the size of the original black hole, likely mere microns in diameter and un-enterable. Likewise, the exit is small, at least until the mass traversing the wormhole nears it, at which point the exit erupts into a white sphere, similar to the entrance during the opening.

Note on risk: A wormhole can collapse entirely (completely disintegrate). This usually drops the ship out into real space at a proportional distance to its destination. Any bridge planned through the Interplanetary Travel Administration (ITA) that does not result in a successful arrival will automatically trigger an investigation. Bridge drops are rare, typically occurring less than a dozen times a year. Despite this low probability, a ship dropped from a bridge in the government-run gateway network is usually located and its passengers or cargo retrieved within 36 hours.