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.
On its backside, PanelSat can dock different modules // such as SOLAR SAILS, DRAG SAILS, Robot Modules/ or DATACENTER UNITS.
PanelSat Satellite Platform
The Platform consists of two Ringstructures, each with a central case for electronics, motors, motordrivers.The Ringstructures are connected through a central Pipe and sidewards through actor units or brackets. At the Front-Ringstructure are the Panels and the Panelmotors mounted for energy capture and attitude control. In this case you see sidewards mounted micro actuators which allow momentum transfer through mass shifting.
PanelSat Platform with Robotic Module
Other than humans PanelSat doesn't need life support in space and can use the suns unlimited energy supply for continued operation. The fuelfree attitude control options will be helpful as well for an orbital construction, repair and maintenance Robot. The robotic module consists of a central electronics case, Two Robot Arms with human like hands, two cameras for binocular vision, a laser pointer to set marks with sourrounding illumination, a display for self expression,to show videos, fotos, drawings.
PanelSat Docking Demonstration with an Orbital Data Module
Click image to start docking animation
This animation shows PanelSat approaching a rotating datacenter module until docking.
Click the preview image to start.
This animation shows PanelSat approaching a rotating datacenter module until docking.
Here, PanelSat is primarily intended to serve as a steering and control module for the datacenter itself, providing functions that are required in any case.
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.
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.
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.
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
PanelSat® at ISSS2025
At the International Symposium on Solar Sailing ISSS2025 at TU Delft
hosted by TU Delft, I had the opportunity to present my latest PanelSat® demonstrator model. This model – about 1 meter in diameter – was physically shown during the symposium and is now permanently donated to TU Delft for future research and academic reference.
In addition to the physical model, I also exhibited two posters that summarize key aspects of the PanelSat® concept. These posters were displayed during the event and are available for download here:
