Today, the commercial exploitation of outer space appears to be a growth area. Barely a week goes by without a satellite launch somewhere on the planet. SpaceX has a gigantic order book and a contract to ferry astronauts to the ISS, probably starting in 2018; United Launch Alliance have a similar manned space taxi under development, and there are multiple competing projects under way to fill low earth orbit with constellations of hundreds of small data relay satellites to bring internet connectivity to the entire planet. For the first time since the 1960s it's beginning to look as if human activity beyond low earth orbit is a distinct possibility within the next decade.
But there's a fly in the ointment.
Kessler Syndrome, or collisional cascading, is a nightmare scenario for space activity. Proposed by NASA scientist Donald Kessler in 1978, it proposes that at a certain critical density, orbiting debris shed by satellites and launch vehicles will begin to impact on and shatter other satellites, producing a cascade of more debris, so that the probability of any given satellite being hit rises, leading to a chain reaction that effectively renders access to low earth orbit unacceptably hazardous.
This isn't just fantasy. There are an estimated 300,000 pieces of debris already in orbit; a satellite is destroyed every year by an impact event. Even a fleck of shed paint a tenth of a millimeter across carries as much kinetic energy as a rifle bullet when it's traveling at orbital velocity, and the majority of this crud is clustered in low orbit, with a secondary belt of bits in geosychronous orbit as well. The ISS carries patch kits in case of a micro-particle impact and periodically has to expend fuel to dodge dead satellites drifting into its orbit; on occasion the US space shuttles suffered windscreen impacts that necessitated ground repairs.
If a Kessler cascade erupts in low earth orbit, launching new satellites or manned spacecraft will become very hazardous, equivalent to running across a field under beaten fire from a machine gun with an infinite ammunition supply. Sooner or later you'll be hit. And the debris stays in orbit for a very long time, typically years to decades (centuries or millennia for the particles in higher orbits). Solar flares might mitigate the worst of the effect by causing the earth's ionosphere to bulge—it was added drag resulting from a solar event that took down Skylab prematurely in the 1970s—but it could still deny access to low orbit for long enough to kill the viability of any commercial launch business. And then there's the nightmare scenario: a Kessler cascade in geosynchronous orbit. The crud up there will take centuries to disperse, mostly due to radiation degradation and the solar wind gradually blowing it into higher orbits.
So here's my question.
Postulate a runaway Kessler syndrome kicks off around 2030, at a point when there are thousands of small comsats (and a couple of big space stations), ranging from very low orbits to a couple of thousand kilometers up. Human access to space is completely restricted; any launch at all becomes a game of Russian roulette. (You can't carry enough armor plating to protect a manned capsule against a Kesseler cascade—larger bits of debris, and by "large" I mean with masses in the 0.1-10 gram range—carry as much kinetic energy as an armor-piercing anti-tank projectile.) Unmanned satellites are possible, but risk adding to the cascade.So basically we completely lose access to orbit.
There are some proposals to mitigate the risk of Kessler Syndrome by using microsats to recover and deorbit larger bits of debris, and lasers to evaporate smaller particles, but let's ignore these for now: whether or not they work, they don't work unless we start using them before Kessler syndrome kicks in.
So, suppose that with the exception of already-on-orbit GPS clusters and high altitude comsats, we can't launch anything else for a century. What effect does it have on society and geopolitics when the sky goes dark?
But there's a fly in the ointment.
Kessler Syndrome, or collisional cascading, is a nightmare scenario for space activity. Proposed by NASA scientist Donald Kessler in 1978, it proposes that at a certain critical density, orbiting debris shed by satellites and launch vehicles will begin to impact on and shatter other satellites, producing a cascade of more debris, so that the probability of any given satellite being hit rises, leading to a chain reaction that effectively renders access to low earth orbit unacceptably hazardous.This isn't just fantasy. There are an estimated 300,000 pieces of debris already in orbit; a satellite is destroyed every year by an impact event. Even a fleck of shed paint a tenth of a millimeter across carries as much kinetic energy as a rifle bullet when it's traveling at orbital velocity, and the majority of this crud is clustered in low orbit, with a secondary belt of bits in geosychronous orbit as well. The ISS carries patch kits in case of a micro-particle impact and periodically has to expend fuel to dodge dead satellites drifting into its orbit; on occasion the US space shuttles suffered windscreen impacts that necessitated ground repairs.
If a Kessler cascade erupts in low earth orbit, launching new satellites or manned spacecraft will become very hazardous, equivalent to running across a field under beaten fire from a machine gun with an infinite ammunition supply. Sooner or later you'll be hit. And the debris stays in orbit for a very long time, typically years to decades (centuries or millennia for the particles in higher orbits). Solar flares might mitigate the worst of the effect by causing the earth's ionosphere to bulge—it was added drag resulting from a solar event that took down Skylab prematurely in the 1970s—but it could still deny access to low orbit for long enough to kill the viability of any commercial launch business. And then there's the nightmare scenario: a Kessler cascade in geosynchronous orbit. The crud up there will take centuries to disperse, mostly due to radiation degradation and the solar wind gradually blowing it into higher orbits.
So here's my question.
Postulate a runaway Kessler syndrome kicks off around 2030, at a point when there are thousands of small comsats (and a couple of big space stations), ranging from very low orbits to a couple of thousand kilometers up. Human access to space is completely restricted; any launch at all becomes a game of Russian roulette. (You can't carry enough armor plating to protect a manned capsule against a Kesseler cascade—larger bits of debris, and by "large" I mean with masses in the 0.1-10 gram range—carry as much kinetic energy as an armor-piercing anti-tank projectile.) Unmanned satellites are possible, but risk adding to the cascade.So basically we completely lose access to orbit.
There are some proposals to mitigate the risk of Kessler Syndrome by using microsats to recover and deorbit larger bits of debris, and lasers to evaporate smaller particles, but let's ignore these for now: whether or not they work, they don't work unless we start using them before Kessler syndrome kicks in.
So, suppose that with the exception of already-on-orbit GPS clusters and high altitude comsats, we can't launch anything else for a century. What effect does it have on society and geopolitics when the sky goes dark?
by Charlie Stross, Charlie's Diary | Read more:
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