The Aether: T-ReX (Thermal Re-entry eXperiment) mission is an educational and technological initiative developed by Aetherspace, a student team connected to the Technovation postgraduate program at KU Leuven in Belgium. The mission's goal is to make space research more accessible by developing a low-cost re-entry CubeSat platform capable of returning scientific payloads and experimental samples back to Earth.
Today, returning material from space is a complex and expensive process, often dependent on missions to the International Space Station. With Aether: T-ReX, the team aims to demonstrate a new pathway: using the CubeSat standard as a compact and affordable platform for re-entry missions. The current mission is the first iteration of this concept – a 3U CubeSat-based demonstrator designed to survive suborbital flight and atmospheric re-entry after being launched aboard a REXUS sounding rocket.
The Aetherspace team currently consists of 8 full-time student members, more than 10 part-time contributors, 2 PhD researchers, 2 coaches, and a growing network of alumni. Beyond engineering, the project also focuses heavily on education, outreach, and interdisciplinary innovation by combining aerospace engineering, embedded electronics, software development, systems engineering, and project management within a student-driven environment.
The team has been supported throughout the development process by Eurocircuits, whose PCB manufacturing services are used across nearly every subsystem of the mission — from power electronics and communication systems to RF boards and camera interfaces. As the project enters its integration and testing phase, reliable PCB production has become increasingly critical for ensuring mission success under the extreme environmental conditions of launch and re-entry.
The Aether: T-ReX mission
The Aether: T-ReX mission consists of two major elements: a Rocket Mounted Unit (RMU) that remains attached to the rocket and a Free Falling Unit (FFU), which acts as the actual re-entry CubeSat demonstrator.
During the mission, the REXUS rocket will carry the experiment to an altitude of approximately 80-90 km. At a predefined point in the flight timeline, the RMU deploys the FFU from the rocket nose cone using a custom deployment system inspired by CubeSat P-Pod mechanisms. After ejection, the FFU begins an autonomous free-fall trajectory back toward Earth.
One of the mission's most important technological demonstrations is the inflatable heat shield system. Shortly after deployment, a dedicated Inflation System activates cool gas generators that inflate a torus structure around the vehicle. This structure deploys and stabilizes the heat shield, which protects the CubeSat during atmospheric descent.
The mission is designed to gather extensive flight data during all phases of the trajectory. The team measures:
- Heat shield temperatures using embedded thermocouples.
- Pressure at the stagnation point.
- Ambient atmospheric pressure and temperature.
- Vehicle acceleration and spin behavior.
- GNSS position and trajectory data.
- Internal torus pressure during inflation and descent.
The collected data will allow the team to compare real-world flight behavior with simulations and validate whether the heat shield system can reliably protect a CubeSat-scale re-entry platform.
Subsystem architecture
The Aether: T-ReX CubeSat follows a highly modular subsystem architecture. Every major subsystem has its own custom PCB following the PC104 CubeSat stacking standard. All subsystems communicate through a CAN bus routed over the PC104 connector stack.
The platform uses multiple STM32L4 microcontrollers, with each subsystem operating its own independent controller for maximum modularity and fault isolation.
The major subsystems onboard the FFU include:
- Electrical Power System (EPS)
- On-Board Computer (OBC)
- SATCOM and GNSS system
- Inflation System (IFS)
- Camera System
- UHF communications subsystem (UHFCOM)
The system architecture was designed around reliability and redundancy. Multiple redundant power converters are used throughout the platform, and individual subsystem power rails can be enabled or disabled independently by the EPS.
Electrical Power System
The Electrical Power System acts as the central power distribution unit of the CubeSat. The EPS uses a LiFePO4 battery architecture combined with redundant 5V and 3.3V power converters to improve reliability during flight.
Each subsystem receives its own dedicated power rail through the PC104 stack. The EPS also integrates battery monitoring and protection circuitry capable of tracking voltage, current consumption, and battery temperature throughout the mission.
Designing the EPS presented significant thermal and mechanical challenges. Due to the low-pressure environment at high altitude, convective cooling becomes extremely limited, requiring careful optimization of converter efficiency and power dissipation. At the same time, the system must withstand launch loads of up to 20 g while operating reliably inside the spinning rocket environment.
Inflation System
The Inflation System (IFS) is one of the mission's most critical subsystems, as it is responsible for deploying the inflatable heat shield after the Free Falling Unit is ejected from the rocket.
Using dedicated cool gas generators, the system inflates a torus structure that deploys and stabilizes the heat shield during descent. The subsystem also monitors torus pressure, controls the parachute burn wires, and logs acceleration data throughout the flight.
The IFS uses its own STM32L476RTG6 microcontroller and communicates with the rest of the CubeSat through the CAN-based PC104 architecture.
Because the subsystem controls irreversible flight events and high-current actuators, reliability was a key design focus. The electronics must remain operational under strong vibration, low-pressure conditions, high temperatures, and the rocket's 4 Hz spin during ascent.
On-Board Computer and SATCOM subsystem
The On-Board Computer is responsible for collecting telemetry from every subsystem and coordinating mission operations throughout the flight.
The OBC interfaces with:
- The CAN bus backbone.
- A Septentrio GNSS receiver.
- An Iridium satellite modem.
- Multiple SD card storage systems.
To improve robustness and reduce software overhead, the team implemented direct sector-based SD card writing without a traditional filesystem for mission-critical telemetry storage.
The software stack is built around FreeRTOS and written entirely in C. Communication between subsystems is handled through a custom-designed message protocol optimized for the mission's telemetry requirements.
The Iridium modem enables global satellite communication, while the dedicated UHFCOM subsystem provides direct telemetry and video transmission over the 868 MHz ISM band toward the ground station.
UHFCOM and RF design
The UHFCOM subsystem is responsible for direct radio communication between the FFU and the ground station. Telemetry data is transmitted toward a ground-based Yagi antenna system.
RF performance was one of the major PCB design challenges of the project. Several boards – particularly the UHFCOM board, turnstile antenna interfaces, and the combined OBC/GNSS/SATCOM board – required controlled impedance PCB layouts to ensure reliable high-frequency signal integrity.
The compact dimensions of the 3U CubeSat introduced additional routing complexity due to fine-pitch components, dense interconnects, and strict mechanical constraints.
Camera system
The Camera System provides visual monitoring of both the inflatable heat shield deployment and the descent trajectory.
The subsystem uses a Raspberry Pi Compute Module 4 combined with two OV4657 cameras equipped with 140-degree field-of-view optics. The camera streams are combined into a single output image and encoded into two separate H264 video streams:
- A high-quality onboard recording stored locally on SD card.
- A low-bandwidth telemetry stream transmitted to the ground station.
In addition to the onboard FFU cameras, the Rocket Mounted Unit also integrates a RunCam Split 4 V2 camera that records the ejection event directly from inside the rocket nose cone.
The Rocket Mounted Unit
The Rocket Mounted Unit acts as the interface between the experiment and the REXUS rocket system. It remains inside the rocket after deployment and performs several critical functions before and during ejection.
The RMU receives ~28V power directly from the rocket service module, isolates it and converts it into multiple regulated voltage rails using high-efficiency DC-DC converters, including:
- 5V rails using parallel converter architectures.
- 3.3V rails derived through LDO regulation.
- 18V rail to charge the battery.
Power is transferred to the FFU through pogo-pin interfaces while the CubeSat remains mounted inside the RMU.
The RMU also interfaces with the rocket through RS-422 communication lines and receives several timeline-based trigger signals used to synchronize experiment events. Because the team's experiment is positioned inside the rocket nose cone, the electronics must survive elevated temperatures approaching 150°C during ascent, in addition to the rocket's approximately 4 Hz spin and high vibration environment.
One of the major design goals of the RMU electronics was limiting inrush current toward the rocket service module while maintaining electrical isolation between rocket and CubeSat grounds.
Engineering challenges and redesigns
As with many aerospace projects, the Aether: T-ReX platform underwent multiple redesign iterations during development.
Several PCB layouts were updated to reduce reliance on QFN packages, making component replacement easier during integration and launch preparations. Power OR-ing circuits were redesigned to reduce voltage drop and improve transient response behavior. The battery management architecture was also revised following changes in battery configuration.
Other redesign decisions were driven by manufacturability and reliability concerns, including:
- Selecting larger components for improved solderability.
- Improving thermal margins on power converters.
- Simplifying assembly procedures.
- Optimizing PCB layouts for vibration resistance.
The inflatable heat shield remains the mission's most technically challenging subsystem and the key enabling technology behind the entire re-entry concept. Its successful deployment and thermal performance will ultimately determine the outcome of the mission.
Ground systems and testing
To support integration and operations, the team developed its own custom ground station capable of receiving live telemetry and a video stream.
The project also relies heavily on simulation and hardware validation tools, including LTSpice and extensive real-world subsystem testing.
Over the coming months, the integrated system will undergo:
- Vibration testing.
- Thermal testing.
- Thermal vacuum testing (TVAC).
- EMI/EMC validation.
- Drop testing.
Unlike many space missions, the project operates with a single flight vehicle rather than separate qualification and flight models. Individual subsystem PCBs can still be reproduced and replaced following environmental testing, allowing the final integrated vehicle to contain freshly assembled hardware before launch.
Educational mission
Beyond the technical mission itself, Aetherspace strongly focuses on education and outreach.
The team regularly organizes STEM workshops for primary and secondary school students and participates in engineering and career fairs to encourage young students to pursue technical studies and aerospace engineering.
One of the flagship outreach activities is the annual “Engineering in Space” event hosted at Campus Group T in Leuven. The event brings together students, alumni, researchers, and aerospace industry professionals for lectures, networking, and technical discussions focused on the future of space technology in Belgium.
For many students, Aetherspace provides a first opportunity to apply theoretical engineering knowledge to a real aerospace mission with genuine operational constraints, deadlines, budgets, and industry partnerships.
Mission outlook
The Aether: T-ReX mission is currently preparing for its final integration and environmental testing campaigns ahead of launch in March 2027 from Esrange Space Center.
Following launch, the team hopes to validate the behavior of the inflatable heat shield system and compare the recorded trajectory data against mission simulations. The results will play an important role in evaluating the feasibility of low-cost CubeSat re-entry systems for future scientific applications.
Long-term, Aetherspace aims to evolve the T-ReX concept toward a fully orbital re-entry mission capable of returning experimental payloads from space through a standardized and accessible CubeSat platform.
The REXUS/BEXUS program is realized under a bilateral Agency Agreement between the German Space Agency at DLR and the Swedish National Space Agency (SNSA). The Swedish share of the payload has been made available to students from other European countries through a collaboration with the European Space Agency (ESA). The Aether: T-ReX team is participating in the REXUS 37/38 project of the REXUS/BEXUS program.
For more information please visit the Aetherspace website.
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