The Cyndor Belt

This is a write up of the Cyndor Belt, an asteroid belt in the Galen Alpha planetary system, a setting for the Tyranny of the Daleks scenario, using the Second Edition of the Doctor Who Roleplaying Game from Cubicle 7.

THE CYNDOR BELT

Astera, largest of the asteroids in the Cyndor Belt, with Galen Alpha visible in the distance

The Cyndor Belt is a mature, metal-poor asteroid belt and the innermost of the two belts found in the Galen Alpha system.  It formed from a relatively small reservoir of silicate and carbonaceous material, resulting in a sparse population dominated by a handful of major bodies. It has relatively little metallic iron and nickel. The belt has evolved over billions of years through collisions, fragmentation and gravitational interactions with the planets, leaving a depleted and dynamically structured population of surviving bodies.

It is found between 1.8 and 2.7 AU from Galen Alpha, between the orbits of the planets Karvtal and Thandor. It is a broad, relatively thin toroidal region, with most bodies orbiting close to the system's principal orbital plane but with a significant range of inclinations.

The total mass of the belt’s material is around 1.86 x 10^20 kg, around 6% of the Solar System’s asteroid belt.  

The belt is widely dispersed, with large distances between significant bodies.  No object within it is large enough to be classified as a dwarf planet. It is unusually top-heavy, with approximately 77% of its surviving mass concentrated in four major asteroids.

The four largest asteroids are as follows:

Astera, with a diameter of 380 kilometers and a mass of 7.8 x 10^19 kg.  It comprises approximately 42% of the belt’s total mass and is predominantly of carbonaceous rock, hydrated minerals and volatile-rich material, with substantial quantities of water ice preserved beneath its surface. Its mean orbit around Galen Alpha is 2.52 AU.

Thalia, a silicate-rich rubble pile roughly 290 kilometres in diameter and 4.3 x 10^19 kg in mass. It constitutes approximately 23% of the belt’s total mass. It orbits at an average of 1.99 AU and so is the innermost of the four largest asteroids.

Nysa is roughly 220 kilometres on its longest axis, with a mass of 1.7 x 10^19 kg. It makes up approximately 9% of the belt’s mass and is composed of primitive carbonaceous material. It orbits at 2.59 AU and is the outermost of the four largest asteroids.

Nysa

Corvus is around 170 kilometres in its longest axis, and has 6.2 x 10^18 kg in mass.  It makes up about 3% of the belt’s mass.  It is a porous, mostly silicate body, with trace minerals. It orbits at an average of 2.18 AU around Galen Alpha.

None of these are nearly-perfectly spherical as they are not large enough, but Astera is roughly spherical in shape, Thalia less so and Nysa is a rather lumpy, almost rectangular cuboid shape. 

The remaining 23% of the belt’s mass is divided amongst a much larger population of smaller bodies. These consist of six large asteroids of between fifty and 120 kilometres diameter, around fifty medium asteroids with diameters of between ten and fifty kilometres, and several thousand small asteroids with typical diameters of between one and ten kilometres. The remaining mass is distributed among tens of millions of smaller fragments, boulders and rubble particles, with the population becoming progressively more numerous at smaller sizes.

The belt is not uniformly populated and contains clusters, mostly formed by collision debris.  This includes the following:

• the Astera Region, a relatively stable, navigationally well-charted region surrounding the largest body.
• The Nysa Debris Family , a dispersed swarm of fragments originating from an ancient collision involving Nysa.
• The Corvus Fragments, a region containing unusually dense concentrations of small and fine rocky debris.

In addition, several prominent asteroid families are known within the Cyndor Belt, consisting of fragments produced by ancient catastrophic impacts. Their members share similar orbital characteristics and broadly similar mineralogical signatures. Some families are believed to be several billion years old, while others represent much more recent collisions.

The belt is is structured by gravitational resonances, collisional families and variations in composition with orbital distance. The inner regions are relatively richer in silicate material, while carbonaceous and volatile-bearing bodies become increasingly common towards the outer belt.

The Cyndorian Bombardment

The Cyndor Belt is now only a remnant of a substantially more massive primordial asteroid population. During the early evolution of the Galen Alpha system, gravitational interactions between the developing planets destabilised large quantities of material. Some was incorporated into the planets, some was scattered into the outer system, and some was ejected altogether. A significant fraction of carbonaceous material is believed to have been delivered to Thandor during this period.

In addition, some in the inner part of the belt fell onto Karvtal and Velnara, in some cases leaving impact craters that can be seen to this day.  This period during the early evolution of the Galen Alpha system is known as the Cyndorian Bombardment and planetologists estimate it occurred between 2.9 and 2.5 billion years ago. The surviving belt is therefore unusually sparse and strongly depleted compared with its original state.

A spacecraft entering the Cyndor Belt would not encounter the dense field of tumbling rocks often depicted in science fiction films. Instead, the region would consist primarily of vast empty distances punctuated by very occasional asteroids.

Navigational charts focus on:

• The four dominant asteroids, which serve as the primary landmarks in the belt.
• A dozen or so secondary bodies large enough to support mining operations or scientific stations.
• Numerous smaller asteroids and debris clusters produced by ancient collisions.
• Extensive empty space between significant objects.

Flying a spaceship safely through the Cyndor Belt is normally an Easy difficulty Coordination + Transport roll.