Altspace & its physics
Much used, little talked of (beyond a hearty “It works very well, thank you very much”), the FTL method used in the Tears of the Stars universe does nonetheless have some extensive work put into on the backside.
In the universe
‘Altspace’ is a commonly used portmanteu for the much unwieldier ‘Alternating Magneto-Gravitic Quasispace’ and describes an inherent property of space-time, discovered by fleet scientists in 1981. It is currently hypothesized that a parallel universe or dimension intersects our universe – or at least large parts of it. Powerful magnetic and gravity fields can be used to manipulate altspace in a way that enables effective propulsion in space.
Today, the most common form of space propulsion in the human fleet are ‘Ensquares’ – Non-newtonian exoatmospheric drive systems. These propulsion units use high-temperature superconductors to project powerful magnetic and gravitational fields around them – the exact direction depends on the geometry of the coils and the drive system in question. Powering such a unit causes it to ‘latch on’ to altspace and drag whatever mass is attached along for the ride. The only difference between those engines and the FTL drives are the power consumption and size.
Small drive units are typically limited to about 2 to 3Gs of acceleration, achieveable with only a dozen or two kilowatts of electrical power on small craft – higher outputs create too steep a field gradient and start to rip open the space-time membrane to altspace, with all sorts of unpleasant gravity eddies forming around the rift.
Larger units, as used on capital ships or freighters, can spread out the effective propulsive field over a larger area of space and as such can both use more power to accelerate as well as netting higher acceleration levels.
Due to these drive units essentially generating a localized gravity field they are inherently unsuitable for usage in all but the most tenuous of atmospheres. The spatial distortion by the drives causes enormous turbulence which will shake apart even the most sturdy of airframes with superhurricane-level winds.
Altspace propulsion (FTL)
Basically only a minor alteration to the Ensquares, these drive units create a focused rift in space-time which allows a ship to ‘slip in’ between normalspace and altspace – sort of like crawling under a blanket on a bed. Much like with normalspace propulsion, the ship is pulled ‘along’ Altspace by the engines, while the powerful gravito-magnetic fields projected by the engines allow the ship to exist outside spacetime.
The mechanisms behind the FTL speeds are still poorly understood by Fleet scientists and the galaxy at large, though the two prevailing hypotheses conclude that the speed of light is simply a different one than in normal space – or that distances within Altspace are vastly compressed.
There are several practical limitations to Altspace travel. The maximum attainable velocity in relation to normal space varies by region, and is thought to be caused by varying levels of intersection between altspace and normal space – but suffice to say, even ‘slower’ areas still yield an effective FTL speed of 5.000c or above.
Second is the limitation on short-range FTL travel. Despite the high eventual speeds, all objects entering altspace have to initially punch through a space-time membrane that offers resistance – in essence, the universe trying to prevent itself from ‘leaking’. This inherent resistance is surprisingly constant and usually takes approximately 30 to 45 minutes to fully overcome with current engine technology.
Thirdly, and ostensibly the largest limitation on long-range flights is the buildup of heat. In normalspace, ships would radiate their excess heat via infrared radiation. While this heat radiation is still present in altspace, the infrared photons ‘pile up’ in the small bubble of normal space surrounding the ship – limiting stays in altspace to the heat production and heatsink capacities of the ship in question before it has to re-emerge in normal space to cool down.
The space-time membrane
This natural property of the universe is ever present and an immutable law. That being said, its actual strength depends on the location and is determined by a complex interplay of local gravity, magnetic fields and the realities of Altspace in the location in question. Star systems are most often ‘shielded’ from altspace by a magnetic and/or gravitic bubble, which makes it almost impossible to enter a star system from a random direction. While it is technically possible, the energy and time requirements to punch through the membrane there are prohibitive – as well as any arrival would shower the surroundings with exotic radiation spikes that are quick to pick up on any scanning system.
The best way to enter star systems is by one of four to six weak spots – typically at around 100 Astronomical units away from the star, in its equatorial plane. The exact location depends on the star in question and may come as close as 65 AU and go as far out as 190 AU. These are the simplest and energetically most prudent gateways to a star system, where short stopovers to radiate heat before one continues on into the deeper system are common.
Naturally these weak spots create a natural chokepoint for any fleet seeking objectives within the system, and in systems containing developed worlds or important assets these are usually jealously guarded with both fixed defenses and a sizable fleet.