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 especially captivating example is the formation of glowing clouds, which often appear in intricate spiral shapes, created during upper-stage rocket fuel releases. In recent years, this phenomenon has caught many skywatchers by surprise. Its surreal, almost ethereal appearance can inspire awe, curiosity, and even confusion among those encountering it without prior knowledge.

These events usually take place in the final moments of an orbital mission, when a rocket — more 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, resulting in striking visuals against the night sky.

This phenomenon has become increasingly recognizable thanks to Falcon 9 launches by SpaceX. When the conditions are just right — usually shortly after sunset or just before sunrise — these glowing spirals become visible from Earth, often captivating viewers and being mistaken for unidentified flying objects or unusual atmospheric displays.

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 drew the attention of people on the ground. At first, it resembled an ordinary aircraft contrail. However, over the next few minutes, the shape began to expand and twist, gradually forming a delicate spiral that evolved 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, the event became clearly visible. I managed to capture the moment in Photo 1, which shows the luminous spiral suspended just above the southwestern horizon.

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Photo 1

The entire spectacle lasted approximately two to three minutes. Its structure continuously shifted, 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’s upper stage 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 Polish time. The rocket lifted off from Cape Canaveral Space Force Station (CCSFS), Launch Complex 40, and the booster touched down successfully at Landing Zone 1. This marked the 475th Falcon launch and the second flight of booster B1092.2.

Although details of the payload 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, carried out in collaboration with the U.S. Space Force. The mission’s purpose was to deploy a satellite in support of national defense operations.

Soon after completing its main objective, the upper stage conducted a standard deorbit burn. The luminous spiral seen in the sky was a direct result of this maneuver, caused by the release of residual fuel into space. As orbital activity continues to increase, and with commercial spaceflight becoming ever more active, such events are likely to become more common — and eventually better understood by the general public.

Weird Science