CAPE CANAVERAL, July 7 — The thousands of small satellites blanketing the sky in the name of global internet connectivity are, by design, disposable. When a Starlink satellite reaches the end of its operational life, SpaceX engineers do not simply leave it to drift as space junk. They command it to kill itself, burning up in a controlled fall through Earth’s atmosphere.
The process is methodical. Each satellite carries its own ion thrusters, and when the decision is made to decommission one, those thrusters fire to lower the craft’s perigee — the lowest point in its orbit — to roughly 200 kilometers, or about 124 miles.
At that altitude, the thin wisps of atmosphere that still exist create enough drag to pull the satellite down faster and faster. The descent from that point is no longer a matter of propulsion but of physics, and it accelerates until the satellite hits the thicker air below. What happens next is violent.
During reentry, the satellite is subjected to temperatures that exceed 1,600 degrees Celsius — that is 2,912 degrees Fahrenheit. At those extremes, most of the satellite’s components vaporize.
SpaceX has designed these spacecraft to be fully demisable, meaning the company’s stated goal is that nothing survives the fall. No debris should reach the ground. That controlled approach stands in contrast to the uncontrolled reentries of defunct satellites that have, in the past, raised concerns about debris striking populated areas.
SpaceX has said its procedures ensure that risk is eliminated. But the question of what happens to all that vaporized material is a separate matter entirely.
A deliberate burn, but not a clean one
The satellites normally operate in orbits that range between 340 and 550 kilometers above Earth — that is 211 to 342 miles. When a satellite is decommissioned, the entire deorbit process, from the first thruster firing to the final burn-up in the atmosphere, typically takes several months. It is not an instant disposal.
It is a slow, controlled descent. But scientists have noted that not every material inside a satellite may burn completely.
While the structure is designed to disintegrate, the metals that make up the satellite’s components — aluminum, titanium, copper — do not simply vanish. They vaporize, and those vaporized metals can persist in the upper atmosphere. The concern is not about a single satellite.
It is about the cumulative effect of thousands of them burning up over time. SpaceX has stated that its controlled deorbit procedures ensure no debris reaches the ground.
That claim addresses the risk to people and property on the surface. It does not address the environmental question of what the vaporized metals are doing to the chemistry of the upper atmosphere. That is a different kind of risk, one that does not involve a satellite crashing through a roof but rather the slow, invisible accumulation of exotic materials in a layer of the atmosphere that scientists are still working to understand.
What the burn leaves behind
The distinction between a controlled deorbit and an uncontrolled reentry is important for public safety. An uncontrolled reentry of a defunct satellite can pose risks to populated areas because the point of impact cannot be predicted with certainty. SpaceX’s method eliminates that uncertainty.
The company brings the satellite down over a remote area of ocean, or at least ensures that any surviving fragments — if there were any — would fall harmlessly. But the environmental concerns that have been raised focus not on the fragments that might reach the ground, but on the materials that do not.
When a satellite experiences temperatures exceeding 1,600 degrees Celsius, most of its components vaporize. The aluminum, the titanium, the copper — these metals are turned into a fine, hot gas that mixes with the air at altitudes where the atmosphere is already thin. The question that scientists are asking is what happens when that process is repeated thousands of times, year after year.
The satellites are designed to be fully demisable. That is a design choice aimed at preventing ground debris.
It is not a design choice aimed at preventing atmospheric contamination. Those are two different problems, and the current design solves only one of them.
A slow, methodical descent
The process itself is straightforward. The satellite’s onboard ion thrusters fire to lower its altitude. The lower the satellite goes, the more atmospheric drag it encounters.
That drag accelerates its descent, pulling it deeper into the atmosphere until the friction of the air itself generates enough heat to destroy it. The satellite does not crash.
It burns. SpaceX operates a constellation of satellites that provide internet connectivity to users around the world. The satellites are not designed to last forever.
When one reaches the end of its useful life, or when it malfunctions, the company deorbits it. The decision to deorbit triggers a sequence that takes months to complete.
It is not a sudden event. It is a planned, gradual process.
For the families of people who rely on Starlink for internet access — and there are many, in rural areas and remote locations where traditional broadband is not available — the deorbiting of individual satellites is invisible. The service
