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 futures of the orbital environment up to 200 years long, stopping early only once a runaway cascade is unmistakable: 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 is now called the Kessler syndrome.

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: with launches continuing at the 2001 to 2009 rate, 90% of satellites and rocket bodies disposed of within 25 years and no explosions, the population of objects 10 cm and larger still grows by about 30% over 200 years, with a catastrophic collision every 5 to 9 years, mostly around 700 to 1,000 km altitude. The growth is slow, over decades to centuries, not a single sudden event.

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: 302,400 scenarios and about 170 million simulated futures in all.

The result we are working toward 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 main sweep started on 6 November 2026. The work generator takes the 302,400 scenarios one after another, in a fixed random order, and sends out 400 workunits of each, one per seed, so results arrive scenario by scenario, and the scenarios finished at any time are a random sample of the whole map. Two beta tests earlier in November ran 50,800 workunits on volunteers' computers (see Results).

Before any work went out, the simulation was checked against the space agencies' comparison study, ESA's MASTER and NASA's ORDEM models, MIT's MOCAT model and the decay of six real debris clouds (see Model Validation). To take part, create an account and attach the BOINC client to the project. 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.