I'm working on a shortish story set couple hundred years in the future, stumbling from one dead end to another since every scifi aspect must check out, and at one point there's a global catastrophe that I'd like to submit to you guys for critical analysis :-]
Story background
There's a planet central to the story arc. Mostly desert, with minimal polar ice caps, but large oceans in the equatorial area, with oases of water scattered further away. Every water body is surrounded by vegetation, and major urban centers are next to water as well. Only very few cities are inland.
One day a particularly sinister group of Rubber Forehead Aliens calling themselves "Nexus" decides it's about time to put an end to this human paradise, however since their military assets are preoccupied at the time they are forced to improvise. They mass up a huge fleet of automatic mining ships, high-impulse tugs and other industrial hardware and set off to the star system that our little planet resides in. They need to perform this in secrecy, without major military movement, so that other factions remain oblivious of their actions and their military assets remain free for defensive operations.
They begin what seems to be a harmless mining operation on a large asteroid body (inclined well over 50° from the ecliptic), while in fact they're merely disassembling the rock into smaller pieces. Using mass drivers they create an elongated cloud of space dust several thousand kilometers in diameter and about 2 million km long. Using an elaborate array of solar sails and gravity attractors they slowly bring this huge cloud closer and closer to the orbit of our planet.
Centuries pass, the indigenous civilization evolves from a steam-era society into a global space-faring one. Lunar colonies, space ports, near-space infrastructure and so on. A dim noodle of light in the night sky has its own traditional cult following, with annual celebrations and rituals.
The cloud is ultimately detected when only few days remain until the collision. No local spacecraft is capable of sustained observation since the delta-v is decades from their propulsive capabilities. Beautiful and intensive show of light is predicted by science and indeed, when the first particles contact the atmosphere this prediction is fulfilled. However only minutes later the intensity increases, turning twilight into full noon, increasing the temperature to that of a hot summer. Several minutes pass when forests together with buildings ignite. All the kinetic energy of a major asteroid is being slowly, relentlessly and efficiently converted into pure heat. Metal parts of structures begin to melt. The ground itself starts glowing with heat. As the planet rotates, a wide belt of total annihilation is burned around the equator. All major cities are almost completely obliterated, together with the proud people who built them.
A series of storms of incredible power sweep the surface. Most of the human civilization now resides on the two moons, only thousands are alive planetside. Out of billions.
Months later the planet, barren and devoid of higher life, cools down. Nexus colony ships are expected to arrive soon. They never come.
Physics
Assume there's an asteroid body that's just right. Density 3000 kg/m³, diameter 30 km, with an inclination high enough to produce a terminal impact velocity of 22 km/s. This works out to an energy of about 2.5 billion megatons of TNT, which spread out over one planetary rotation gives over 118 EW of destructive power. That's more than 28,000 Mt/s in TNT equivalent, or even better - about 567 Tsar bombs per second. In order to make the cloud the Nexus would have to dispatch 100,000 heavy mining units, each able to extract a 40cm chunk of the asteroid in roughly two seconds. It would take a generation short of 300 years to finish the process.
My question is... do you find this plausible? What defenses would you consider against this form of threat, assuming you had 1, 10 or 100 years notice? Would the effects of the impact resemble my description and rendering?
Thanks
Story background
There's a planet central to the story arc. Mostly desert, with minimal polar ice caps, but large oceans in the equatorial area, with oases of water scattered further away. Every water body is surrounded by vegetation, and major urban centers are next to water as well. Only very few cities are inland.
One day a particularly sinister group of Rubber Forehead Aliens calling themselves "Nexus" decides it's about time to put an end to this human paradise, however since their military assets are preoccupied at the time they are forced to improvise. They mass up a huge fleet of automatic mining ships, high-impulse tugs and other industrial hardware and set off to the star system that our little planet resides in. They need to perform this in secrecy, without major military movement, so that other factions remain oblivious of their actions and their military assets remain free for defensive operations.
They begin what seems to be a harmless mining operation on a large asteroid body (inclined well over 50° from the ecliptic), while in fact they're merely disassembling the rock into smaller pieces. Using mass drivers they create an elongated cloud of space dust several thousand kilometers in diameter and about 2 million km long. Using an elaborate array of solar sails and gravity attractors they slowly bring this huge cloud closer and closer to the orbit of our planet.
Centuries pass, the indigenous civilization evolves from a steam-era society into a global space-faring one. Lunar colonies, space ports, near-space infrastructure and so on. A dim noodle of light in the night sky has its own traditional cult following, with annual celebrations and rituals.
The cloud is ultimately detected when only few days remain until the collision. No local spacecraft is capable of sustained observation since the delta-v is decades from their propulsive capabilities. Beautiful and intensive show of light is predicted by science and indeed, when the first particles contact the atmosphere this prediction is fulfilled. However only minutes later the intensity increases, turning twilight into full noon, increasing the temperature to that of a hot summer. Several minutes pass when forests together with buildings ignite. All the kinetic energy of a major asteroid is being slowly, relentlessly and efficiently converted into pure heat. Metal parts of structures begin to melt. The ground itself starts glowing with heat. As the planet rotates, a wide belt of total annihilation is burned around the equator. All major cities are almost completely obliterated, together with the proud people who built them.
A series of storms of incredible power sweep the surface. Most of the human civilization now resides on the two moons, only thousands are alive planetside. Out of billions.
Months later the planet, barren and devoid of higher life, cools down. Nexus colony ships are expected to arrive soon. They never come.
Physics
Assume there's an asteroid body that's just right. Density 3000 kg/m³, diameter 30 km, with an inclination high enough to produce a terminal impact velocity of 22 km/s. This works out to an energy of about 2.5 billion megatons of TNT, which spread out over one planetary rotation gives over 118 EW of destructive power. That's more than 28,000 Mt/s in TNT equivalent, or even better - about 567 Tsar bombs per second. In order to make the cloud the Nexus would have to dispatch 100,000 heavy mining units, each able to extract a 40cm chunk of the asteroid in roughly two seconds. It would take a generation short of 300 years to finish the process.
My question is... do you find this plausible? What defenses would you consider against this form of threat, assuming you had 1, 10 or 100 years notice? Would the effects of the impact resemble my description and rendering?
Thanks
