Spiral in the Sky: A Fuel Dump in Low Earth Orbit

Polish version is here

While most sights in the night sky originate from natural atmospheric or astronomical phenomena, some rare and unexpected events are caused by human activity in space. One particularly captivating example is the formation of glowing clouds that often take on intricate spiral shapes, created during upper-stage rocket fuel releases. In recent years, this phenomenon has taken many skywatchers by surprise. Its surreal, almost ethereal appearance can evoke awe, curiosity, and even confusion among those who witness it without prior knowledge.

These events usually occur in the final moments of an orbital mission, when a rocket, specifically its second stage, performs a deorbit burn. During this maneuver, any remaining fuel and oxidizer, typically RP-1 kerosene and liquid oxygen, are vented into space to prevent the risk of explosion during atmospheric reentry. In the vacuum of space, these gases expand rapidly and dramatically, producing bright, translucent plumes that drift across the upper atmosphere. Although the ground below may already be in darkness, the clouds can still catch sunlight, creating striking visual displays against the night sky.

This phenomenon has become increasingly recognizable thanks to SpaceX Falcon 9 launches. When conditions are just right, usually shortly after sunset or just before sunrise, these glowing spirals become visible from Earth, often mesmerizing observers and sometimes being mistaken for unidentified flying objects or rare atmospheric phenomena.

Observations

March 24, 2025, around 9:00 PM – Katowice (Poland)

urban conditions, high level of light pollution

Shortly after sunset, a bright streak drifting slowly across the sky caught the attention of people on the ground. At first, it looked like an ordinary aircraft contrail. However, over the next few minutes, the shape began to expand and twist, gradually forming a delicate spiral that transformed into a glowing cloud. Witnessing such a spectacle over the heart of Upper Silesia seemed unlikely, yet thanks to favorable orbital parameters and just the right lighting conditions, the event became clearly visible. I managed to capture the moment in Photo 1, which shows the luminous spiral hanging just above the southwestern horizon.

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Photo 1

The entire spectacle lasted approximately two to three minutes. Its structure changed constantly, and the slow, graceful rotation of the spiral’s inner section was clearly visible. What we observed was a cloud of vaporized propellant released during the deorbit procedure of the Falcon 9 upper stage, carried out as part of the classified NROL-69 mission.

Mission Background

SpaceX launched the NROL-69 mission on March 24, 2025, at 6:48 PM local time in Poland. The rocket lifted off from Cape Canaveral Space Force Station (CCSFS), Launch Complex 40, and the booster landed successfully at Landing Zone 1. This was the 475th Falcon launch and the second flight of booster B1092.2.

Although the payload details remain classified, the mission was commissioned by the National Reconnaissance Office (NRO), the U.S. intelligence agency responsible for managing reconnaissance satellites. It was part of the National Security Space Launch (NSSL) program, conducted in collaboration with the U.S. Space Force. The mission’s goal was to deploy a satellite in support of national defense operations.

Soon after completing its primary objective, the upper stage performed a standard deorbit burn. The luminous spiral observed in the sky was a direct result of this maneuver, caused by the release of residual propellant into space. As orbital activity continues to increase and commercial spaceflight becomes more frequent, such events are likely to occur more often and eventually become better understood by the general public.

Weird Science