Throughout history, wildfires have been prominent natural disasters that cause pollution, environmental damage and loss of lives. Local firefighting agencies and disaster response initiatives have typically managed to contain fires and limit damage to controllable levels. However, in recent times, due to climate change and human population growth, wildfire occurrences are becoming less predictable and result in greater cost and damage. Solutions employing new technologies and a more operations-oriented analysis, through system-of-systems (SoS), could be a promising way to combat further wildfire devastation. Designing new aircraft and strategies that can be used in human transport and firefighting is one of the goals of the COLOSSUS project. To enable international innovation, especially amongst young researchers, a student competition called the X-Challenge was released. This paper will deal with the overview of the challenge, breaking down its objectives, constraints, research contributions and outcomes. Following this paper, four different student teams will present their solutions, including innovative aircraft designs and SoS analysis methods. The knowledge gained, and successes and failures from the challenge, alongside outlook and recommendations for future challenges and SoS exploration, will be discussed in this paper.

Wildfire severity and frequency continue to increase worldwide, making effective aerial wildfire suppression a critical component of wildfire response. The COLOSSUS (Collaborative SoS) X-Challenge project established a system-of-systems (SoS) framework to design and evaluate next-generation firefighting capabilities and operational concepts. Building on this framework, this paper presents a simulation environment that jointly evaluates conventional fixed-wing and electric vertical takeoff and landing (eVTOL) firefighting aircraft concepts by integrating aircraft design, fleet-level coordination, and mission-level tactics into the unified SoS assessment, enabling performance-driven design exploration. The framework was expanded with new tactics, including a ridge-based drop method, and a flanking selection algorithm that leverages road networks to establish anchor points and construct fire lines. Simulations across three representative wildfire locations (Salamis, Pyrenees, and Palisades) demonstrate that combining purpose-built aircraft with adaptive tactics can significantly improve mission effectiveness.

Wildfire disasters are increasing in scale and severity, underscoring the need for more capable and coordinated aerial firefighting systems. This work presents a performance-based integrated aerial system framework that links the aircraft design tool RISPECT+ with the wildfire mission analysis tool SoSID Toolkit+ to evaluate and optimize system-level effectiveness. Incorporating terrain-specific wildfire characteristics, the framework identifies optimal aircraft configurations and deployment strategies that maximize integrated measurement of effectiveness across diverse regions. A unified surveillance platform strengthens the system of systems architecture and supports the operation of aerial firefighting aircraft. Results show enhanced system-oriented design and multi-agent coordination, with future work focused on optimal designs across diverse aircraft configurations and integrating operational environmental factors relevant to aerial firefighting.

The year 2025 saw the continuing trend of worsening wildfire severity and impact with escalating costs, burnt area and casualties. Subsequently, the capability for a rapid response operation is ever-growing, with aerial assets providing a key role in fulfilling this function. One problem with aerial suppression is the reliance on updated fire data and precise fire front information. Drones or other long-endurance vehicles are commonly used to assist in this matter, providing real-time data and imagery to the manned suppression bombers. The interactions and collaboration between these systems to achieve an improved wildfire suppression can be classified as a system-of-systems (SoS). To facilitate the design, interaction and communication of the surveillance drones and suppression aircraft, this paper develops a holistic framework using an agent-based simulation. The framework allows for the analysis of top-level drone design parameters and operational considerations with their communication and collaboration both with each other and the suppressive agents. The results showcase the importance of swath radius for better wildfire coverage and suppression, with radii less than 50 m preventing successful exploration of the fire. The importance of monitoring is highlighted by the observed greater reductions in burnt area and fleet energy usage when increasing the monitoring agent fleet size by 50% compared to the same increase in suppression agent fleet size.

Wildfires are increasing in frequency, intensity, and duration, driving up suppression and damage costs and motivating a more coordinated use of aerial firefighting assets. Within this context, we extend the COLOSSUS Project’s X-Challenge System-of-Systems (SoS) simulation toolkit with an integrated aircraft sizing and fleet assessment methodology that links conceptual aircraft design with tactic selection. Two platforms are sized under 2035 technology assumptions—a 2000 kg payload electric Vertical Takeoff Landing (eVTOL) and a 3000 kg payload Single Engine Air Tanker (SEAT) using physics-based performance and parametric cost models. A Design of Experiments (DoE) workflow coupled with the SoS toolkit evaluates mixed fleets and tactic assignments in three representative regions. Effectiveness is quantified via a weighted, normalized Measure of Effectiveness that aggregates burnt area, emissions, and cost metrics into a single scalar. Results show that acquisition cost dominates overall effectiveness and that location-specific fleet compositions can outperform a single fixed fleet without degrading suppression outcomes, motivating future work on adaptive, region-specific fleet design and sensitivity analyses.

This study documents the design, development, and evaluation of a purpose-built aerial firefighting fleet optimized for diverse wildfire suppression environments as part of the COLOSSUS project’s X-Challenge. The multidisciplinary effort encompassed aerodynamic design, propulsion system, systems integration, cost estimation, simulation, design of experiments, and fleet optimization. Key technical advancements include a conceptual hybrid electric Vertical Takeoff and Landing (eVTOL) aircraft design, and the integration of a series hybrid propulsion model into the System of Systems Inverse Design (SoSID) simulation toolkit, in which evaluation takes place at fleet level. Simulation results indicate that the proposed aircraft achieves competitive or superior effectiveness across all test scenarios, with the series hybrid configuration offering notable endurance and tactical adaptability.