Kessler@home is a volunteer computing project studying the long-term stability of low Earth orbit. In 1978, NASA scientists Donald Kessler and Burton Cour-Palais described how collisions between objects in orbit could create debris faster than the atmosphere removes it, setting off a self-sustaining cascade now known as the Kessler syndrome.

Your computer will simulate complete 200-year futures of the orbital environment: launches, satellite failures, collisions, and the debris clouds they produce. Running hundreds of these futures for each of more than 200,000 scenarios, covering launch traffic, the planned megaconstellations, disposal reliability, debris removal and the changing atmosphere, lets us estimate how likely a runaway cascade is and when it would come, not just what the average future looks like.

The Kessler syndrome

In 1978 Donald J. Kessler and Burton G. Cour-Palais of NASA showed that once the density of objects in low Earth orbit passes a threshold, collisions between them generate fragments faster than atmospheric drag removes them. The resulting chain of collisions, now called the Kessler syndrome, unfolds over decades to centuries rather than as a single sudden event.

Space agencies run long-term evolutionary models of the debris environment (NASA LEGEND, ESA DELTA, UKSA DAMAGE, JAXA LEODEEM and others). A comparison study by the Inter-Agency Space Debris Coordination Committee found that their 200-year forecasts broadly agree, and that parts of low Earth orbit, notably around 800 to 1,000 km altitude, are already unstable even with no further launches.

What is different about Kessler@home

Each simulated future is a random draw: which objects collide, how each collision breaks apart, which satellites fail to dispose of themselves. Most published studies use on the order of a hundred such draws per scenario, which is enough to estimate the average future but not the probability of the rare, runaway ones. Kessler@home uses volunteer computers to run hundreds of draws per scenario, and thousands where the outcome is in doubt, across a sweep of eleven variables covering launch traffic, the planned megaconstellations, post-mission disposal, how deadly small debris is to a working satellite, debris removal, solar activity and the slow thinning of the upper atmosphere from carbon dioxide: 233,280 scenarios and about 130 million simulated futures in all.

The result we are working towards is an open, published probability map of low Earth orbit stability: for which combinations of traffic and behavior each orbital shell stays stable with high confidence, and where it tips into runaway. Every scenario assumes operators carry on as planned whatever happens, so the map answers "what if nothing is done", which is the question that has to be answered first.

Status

The simulation application is written and is being checked: it reproduces the agencies' 2009 comparison study, has been compared with ESA's MASTER model and MIT's MOCAT model, and follows the decay of six real debris clouds (see The science). The scenario sweep is defined. The BOINC side, which hands out work and collects results, comes last and is not yet running, so no work is being distributed. Creating an account now means your computer will receive work as soon as the application is released. Progress is posted under News.

Who runs it

Kessler@home is an independent project. We aim to work with established debris-modeling groups and will credit collaborators here as the project develops. Questions are welcome on the message boards or via the contact page.