PanelSat®, Scaleable Agile Satellite, Fuel Free 9-axis acs

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This site covers PanelSat®, an agile satellite, which uses it's thin film solar cell panels for both - harvesting energy and for fuel free pointing, steering and attitude control.

Actually in development, PanelSat® will use the solar radiation pressure (srp) to turn it into and keep it in the desired direction. A second fuel free control option is to move masses through Mass Switching Units (MSU) and with them the mass center (cm) of the spacecraft.

While the operation in orbit will mainly be fuel free, thruster propulsion is also available through double thruster units (DTU) for reaching the intended orbit after launch, changing orbit or deorbiting the satellite at the end of life.

larger photo

The photo shows a small, 50 cm diameter PanelSat® printout model. The smallest PanelSat® base version will be about 100 cm . As it is scale able, the spacecraft size could reach nearly the diameter of the launcher. Those larger models would allow the next generation satellites with more electric and turning power, while the mass stays low compared to satellites with the same panel area.

larger photo

This photo shows our prototype base model body hanging on a thin thread before doing a first rotation test. The panels are not yet mounted. Diameter about 1m, mass about 4,5 kg.

Take a look onto our PanelSat Rotation Test

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🔹 MP4 version (approx. 480 MB) This file is just for those interested in the rotational dynamics of the model.

For those who don’t have the patience to watch a 11-minute video showing a satellite model suspended from a thread and set into rotation by hand – here’s a brief summary:
The video shows a manual test of the rotational dynamics of a PanelSat model, approximately 1 meter in diameter and weighing about 4.5 kg.

Without speaking, I demonstrate the two operating modes of the PanelSat-MSU units (Mass Switching Units): first, synchronized mass motion, then opposing mass motion. I then set the model into rotation – mimicking what two MSUs would do in orbit when shifting their internal masses in opposite directions.

What happens next even surprised me:
The thin suspension thread (approx. 2 m long, 2 mm in diameter) – without any electronics or active control – not only stops the rotation, but reverses it completely. And it does so repeatedly. If the camera hadn’t stopped recording at 4.3 GB, the video would have continued even longer.

Just for context: Back at ISSS2019, my earlier aluminum model with 5 V motors could barely lift its panels against Earth’s gravity. Now, the restoring torque of a simple thread is enough to rotate a much larger and heavier model around its central axis.
Attitude control through mass displacement proves stable – even without power, sensors, or software. In my eyes, the MSU concept works but I am keen on your opinion.

To everyone attending ISSS2025 at TU Delft in Delft – see you there.

Open Invention, Mai 3, 2025, defensive publication - thread axis

Can gravity become a reference axis for satellite attitude control – without any reaction wheels? In the PanelSat concept, we explore a method of mass shifting based on a virtual line to the local gravitational center – a “thread axis” as shown in the video that serves as a reference for internal mass displacement. Initial tests show that rotation and stabilization of the satellite body can be achieved using this method alone.
I’m making this idea publicly available for use in open research and development – no patents, no restrictions.

Let’s rethink how we stabilize spacecraft Mass shifting isn’t weak – it just needs the right axis. If internal masses are displaced along an axis that points toward the nearest dominant gravitational center, even small mass movements can generate significant torque – without reaction wheels, and potentially without jitter. A thin thread, only 2mm diameter turns a much larger satellite model. Think of the short lever this thread has in relation to the model.

The idea of a virtual “thread axis” is more than a metaphor: it can serve as a universal reference for attitude control. Whether the center of gravity lies within Earth, the Moon, the Sun, or even at the galactic core – this imagined axis always exists.

By aligning internal mass displacement (e.g., through MSUs) along this virtual line, spacecraft can achieve efficient, reactionless rotation – even for large structures. This may mark the beginning of a new control philosophy in spaceflight. hashtag#MassShifting hashtag#AttitudeControl hashtag#PanelSat hashtag#SpaceInnovation hashtag#OpenScience