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    A challenging high-end data acquisition system in a harsh wind tunnel environment at high rotational speed
    (3AF, 2023) Bardet, S.M. ; Zutphen, W.J.C.M. van ; Fontaine, F.M. ; Faasse, P.R.
    NLR developed an advanced, high-performance data acquisition system for a generic engine test rig. The test rig is intended for wind tunnel use. The RDAS and MDAS subsystems are bespoke developments, supporting a total of 120 rotating and almost 700 stationary measurement channels. All measurements are made under harsh environmental conditions: wide temperature range and high vibration levels. The rotating section tolerates rotation up to 16,000 rpm.
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    A Crosstalk Sensitivity Analysis on Bundles of Twisted Wire Pairs
    (IEEE, 2018) Lansink Rotgerink, J.H.G.J. ; Leferink, F.
    Uncertainties in the geometry of complex cable bundles highly complicate crosstalk predictions. A change in for instance the position or the twist rate of individual cables in a bundle might have an impact on crosstalk levels. Application of sensitivity analyses can indicate which model parameters are most sensitive, and in which cabling configurations. In this paper, the efficient Stochastic Reduced Order Models (SROM) method is used to perform such a sensitivity analysis. It is applied to two cable bundles with two and seven twisted wire pairs, respectively. Monte Carlo simulations are performed to determine the accuracy of the SROM method. The sensitivity of parameters like inter-pair and intra-pair separation distance and the twist rate is determined in two different cases. Moreover, the effects of bundle twist and cable meandering to parameter sensitivities is investigated.
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    A Heat Pump for Space Applications
    ( 2015) Gerner, H.J. van ; Donk, G. van ; Pauw, A. ; Es, J. van ; Lapensée, S.
    In commercial communication satellites, waste heat (5-10kW) has to be radiated into space by radiators. These radiators determine the size of the spacecraft, and a further increase in radiator size (and therefore spacecraft size) to increase the heat rejection capacity is not practical. A heat pump can be used to raise the radiator temperature above the temperature of the equipment, which results in a higher heat rejecting capacity without increasing the size of the radiators. A heat pump also provides the opportunity to use East/West radiators, which become almost as effective as North/South radiators when the temperature is elevated to 100°C. The heat pump works with the vapour compression cycle and requires a compressor. However, commercially available compressors have a high mass (40 kg for 10kW cooling capacity), cause excessive vibrations, and are intended for much lower temperatures (maximum 65°C) than what is required for the space heat pump application (100°C). Dedicated aerospace compressors have been developed with a lower mass (19 kg) and for higher temperatures, but these compressors have a lower efficiency. For this reason, an electrically-driven, high-speed (200,000 RPM), centrifugal compressor system has been developed in a project funded by the European Space Agency (ESA). This novel 3-stage compressor system has a mass of just 2 kg and a higher efficiency than existing aerospace compressors. The compressor system has been incorporated in a heat pump demonstrator, which uses isopentane (R601a) as refrigerant. Due to the exposure of isopentane to radiation in a space application, other substances will form. However, a literature study shows that the amounts of the formed substances are so small, that no significant influence on the performance of the heat pump is expected. Tests were carried out with the heat pump, and at the target setting (saturation temperature of 45°C at the evaporator, 100°C at the condenser, and a payload heat input of 5 kW), the measured COP is 2.3, which is higher than the original requirement of 2.
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    A Literature Review and Proposal Towards the Futher Integration of Haptics in Aviation
    (Springer, 2024) Lange, R.D. de
    Flight simulator training is essential for aircraft pilots to learn and maintain the ability to fly specific aircraft for both commercial and defence purposes. With recent advances in extended reality, the implementation thereof has made its way into proposed simulated flight training protocols. In conjunction to the advent of extended reality, research into the use of haptics or the sense of touch within VEs has accelerated. A few challenges persist within simulation training including training effectiveness, level of immersiveness, and the manageable exposure duration per training run. Extended reality experiences face similar challenges. The field of haptics might provide solutions for these challenges. Thus, this paper reviews the state-of-the-art of haptics, current challenges, and possible future applications within aviation simulation and training. It is found that research with respect to the integration of haptics in aviation training and simulation is not yet mature. A lot of potential exists for research into the improvement of training effectiveness, performance and immersiveness within extended reality based simulation for flight training and maintenance engineering purposes via haptics. Based thereupon future work is suggested to look into 1) decreasing simulator sickness by simulating and synchronizing expected real life perturbations within flight simulation via haptic wearables 2) simulating a sense of physical flight within a static simulator set-up by leveraging self-motion 3) enabling physical interaction of aircraft parts digital twins for improving extended reality based maintenance engineering performance by utilizing haptic wearables.
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    A Review on Education and Training Needs for Military Space Operations
    (NTSA, 2024) Caso, S. ; Tanis, T.P. ; Kleef, A.J.P. van
    Space is a dynamic and rapidly evolving domain, driven by the increased engagement across the commercial, scientific, governmental and military sectors. Particularly, operations in low Earth orbit (LEO), medium Earth orbit (MEO) and geostationary Earth orbit (GEO) play a vital role in sustaining infrastructures for daily on-Earth activities, e.g., global positioning system (GPS) and 5G. In 2019, a significant milestone was reached with the adoption of NATO’s Space Policy, officially recognizing space as a distinct operational domain alongside land, air, sea and cyberspace. This integration positioned space capabilities as an integral part to military strategies, supplying vital information for secure operations. Due to the growing dependency of space infrastructures, military personnel must be trained to be able to effectively operate space assets and to be prepared for hostile or environmental calamities. This paper conducted a state-of-the-art analysis of military training needs in the realm of space. A literature review was made, encompassing the current scientific literature in space training, with the latest topics from several space agendas outlined by relevant organizations and countries. In addition, interviews were conducted, complemented by surveys, in order to identify the current training gaps and areas for improvement. The findings identified several research gaps and needs related to training and education tools, with a specific emphasis on the Space Situational Awareness (SSA) and Space Traffic Management (STM) topics. These recommendations were particularly addressed to the recognizing and mitigating of potential calamities, a concern heightened by the dense presence of satellites in the Earth's orbit. Additionally, a training gap was identified within the use of satellite images for Intelligence, Surveillance & Reconnaissance (ISR) activities. These activities play a vital role in supporting military operations with their decision-making processes, by improving situational awareness on land, in air, and at sea. Finally, suggestions were made regarding the use of the latest technological tools.
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    A systematic literature review of low-cost 3D mapping solutions
    (Elsevier, 2025) Balado Frias, J. ; Garozzo, R. ; Winiwarter, L. ; Tilon, S.M.
    In "low-cost" solutions, ensuring economic accessibility and democratizing the availability of emerging technologies stand as pivotal considerations. This study undertakes a systematic literature review of low-cost 3D mapping solutions. Leveraging SCOPUS as the primary database, a comprehensive bibliometric analysis encompassing 1380 publications was conducted, subsequently narrowing the focus to 87 recent publications for detailed review. This research endeavors to delineate the defining characteristics of low-cost systems, elucidate their principal applications and preferred platforms, assess accessibility level, gauge the extent of innovation in both hardware and software development, explore the contributions of Deep Learning and data fusion, evaluate the consideration of data quality, and examine the contemporary relevance of photogrammetry within low-cost context. The findings demonstrate that many authors subjectively use the term low-cost to highlight qualities of a technology, methodology or sensor, but challenges arise from data quality comparisons with high-cost systems.
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    Acoustic Lucky Imaging for microphone phased arrays
    (Elsevier, 2023) Biesheuvel, J. ; Tuinstra, M. ; Santana, L.D. de ; Venner, C.H.
    Acoustic imaging methods are used to detect and quantify aerodynamic noise sources in aeroacoustic experiments. In wind tunnels with an open jet test section the sound wave propagating from an aeroacoustic source to a microphone array is distorted by the shear layer in the propagation path. The velocity fluctuations caused by the turbulence in the shear layer continuously alter the propagation time between source and observer causing reduction of the coherence between two microphone signals. The reduction in coherence is stochastic and dependents on the relative position between source and microphone. This leads to blurred acoustic source images with reduced peak Sound Pressure Level. This paper presents the Acoustic Lucky Imaging methodology, based on a methodology in astronomy to correct for image distortion due to turbulence present in Earth’s atmosphere. Furthermore, a model for coherence loss is derived to explain the loss of acoustic image resolution and allow for a-priori estimates on acoustic image blurring. The methodology is applied to an acoustic data set obtained in the open jet of a large industrial wind tunnel. It is shown that the presented methodology can restore a loss of 6 dB peak Sound Pressure Level by 3 dB and increase the resolution of the acoustic image at 8 kHz, a wind tunnel speed of 34 m s−1, and a shear layer thickness of ~1 m.
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    Advanced landing gear fibre Bragg grating sensing and monitoring system
    ( 2022) Grooteman, F.P. ; Goutagny, R. ; Davies, C. ; Leest, T. van ; Platt, I. ; Symons, J.
    In this paper an advanced optical-based landing gear load sensing and monitoring system is presented. The system measures strains using fibre Bragg grating sensor that are converted into loads and torque at the landing gear wheels and provides this data for use by the aircraft systems for integration with aircraft health monitoring, hard landing detection, flight management, flight controls and ground controls. A complete sensing system was developed in the European Union Clean Sky 2 Joint Technology Initiative Advanced Landing Gear Sensing and Monitoring (ALGeSMo), described herein. This involved: the integration of optical fibres into a composite structure, the development of an optical harness (cabling and connectors) meeting aircraft installation requirements, the readout of the optical fibre sensors with state-of-the-art miniature optoelectronics and the processing and communication of the data. Apart from specific tests on the various components, a bespoke test rig was developed to rigorously test the whole sensing and monitoring system on an A320 main landing gear slider tube to validate the performance of the system. The system-level tests performed on the test rig showed a very good correlation with applied actuator loads and additional conventional strain and temperature sensors. It demonstrates that loads along all three axis of the landing gear and the torque about the wheel axle can be accurately measured. Tests performed at cold and elevated temperatures, however, revealed that the generally applied one-dimensional temperature compensation equation is not accurate enough for this application, due to the non-uniform non-stationary temperature field. The ALGeSMo research activities have advanced the state of the art in several key areas for the deployment of optical sensing systems for safety-critical applications, such as integration of optical fibres into composite material, robust optical connections, avionic-compliant optical interrogator and landing gear load measurement up to technology readiness level technology readiness level 5.
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    Advanced models for the transfer impedance of metal braids in cable harnesses
    (IEEE, 2018) Verpoorte, J. ; Schippers, H. ; Lansink Rotgerink, J.H.G.J.
    Since the development of the model for transfer impedance of metal braids by E.F. Vance, a large number of authors have tried to improve this model in order to make it more accurate and more reliable. The improvements were based on a more accurate physical or electromagnetic description, or on empirical data of a large number of transfer impedance measurements. This paper provides an overview of the specific models for diffusion, hole inductance and braid inductance. In addition to the general overview, a preferred combination of models for the calculation of transfer impedance is presented.
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    Advancing safety in organisations: application via the Luton Safety stack
    (MATEC Web of Conferences, 2019) Smeltink, J. ; Stroeve, S. ; Kirwan, B.
    Controlling and improving safety in organisations is achieved using a Safety Management System (SMS). Notwithstanding the variety of components considered in SMS standards, including human factors and safety culture, safety management systems are sometimes observed by those at the ‘sharp end’ as being bureaucratic, distinct from actual operations, and being too focused on the prevention of deviations from procedures, rather than on the effective support of safety in the real operational context. The soft parts of advancing safety in organisations, such as the multitude of interrelations and the informal aspects in an organisation that influence safety, are only considered to a limited extent in traditional safety management systems. The research in Future Sky Safety Project 5 (FSS P5) focused on improving these human-related, informal organisational aspects. Since every organisation is unique, in the operations it conducts, its history, and its organisational culture, there cannot be a one-size-fits-all standard for advancing safety in organisations. Rather, this needs to be based on the organisation at hand, leading to tailored solutions. This has been applied to a safety culture assessment and enhancement approach applied for six key organisations at London Luton Airport, and the approach has become known as the Luton Safety Stack. The six organisations decided to share the detailed results of their individual safety culture assessments. They formed a group that holds quarterly meetings, which always include a workshop element. From this approach, the organisations were stimulated to develop harmonised procedures for all ground-handling operators at Luton, and for each operation, creating a simple one-page procedure with diagrams, to keep it simple and safe. The Luton Safety Stack shows that when organisations share a place, such as at an airport, they need the opportunity to meet to discuss both potential safety threats, and opportunities to advance safety, because even through organisations are interdependent, safety issues in one organisation often have implications for others.
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    Aircraft Level Thermal Management Analysis for Early Design Stages of Future Aircraft: Integration of Systems and Compartments into an Interacting Generic Approach
    (MDPI, 2025) Muijden, J. van ; Aalbers, V.J.E.
    For future commercial aircraft having hybrid electric drivetrains, the impact of electrical power generation and distribution on heat production and required heat rejection is of a larger magnitude than for conventional aircraft. The thermal management system (TMS) to control component and compartment temperatures may require dedicated solutions. The impact of TMS on top-level aircraft requirements (TLARs), e.g., weight and drag penalties, should become clear in the early stages of design for integration in the configuration. To assess this impact, a generic approach is presented to support aircraft level thermal management analysis and design based on global aircraft parameters.
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    An Assessment of STPA as Applied to the Scaled Flight Demonstrator Test Program
    (SFTE, 2024) MacCafferty, J.P. ; Bumgardner, W.R.
    Systems Theoretic Process Analysis (STPA) is a methodology for system development and safety assessment which builds on the System-Theoretic Accident Model and Processes (STAMP) causality model which approaches safety as a dynamic control problem. The STPA methodology addresses system analysis and safety assessment for systems that involve complex human interactions and high degrees of coupling. The purpose of this paper is to demonstrate the application of STPA to the remotely piloted Scaled Flight Demonstrator (SFD) aircraft test program, and assess the effectiveness for test planning and risk assessment relative to the traditional Test Hazards Analysis (THA) process. The SFD aircraft is a 1:8.5 scaled model of the Airbus A320 which has been modified into a distributed electric propulsion (DEP) configuration. The aircraft was developed in collaboration with members of the Clean Sky 2 program: The Royal Netherlands Aerospace Centre (NLR), Technische Universiteit Delft (TU Delft), The Office national d'études et de recherches aérospatiales (ONERA), Centro Italiano Ricerche Aerospaziali (CIRA), Airbus, and Orange Aerospace. This effort identifies multiple benefits for flight testers when applying STPA to a highly complex system, including: increased knowledge of the system under test, forced collaboration between the test team and system experts, and identification of risks and mitigations that may otherwise be missed. The team also identifies some drawbacks to applying STPA, including: the time investment required to learn and apply the process, and the challenge in identifying specific hardware or software failure modes. Lessons learned and recommendations are presented to help other flight test professionals determine how and when STPA can best be applied to their programs in the future.
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    Assessing Fatigue Risk and Mitigation Strategies for Air Traffic Controllers in European Air Traffic Service Providers
    (Elsevier, 2025) Vrancken, P ; Cabon, P. ; Frantz, B. ; Somvang, V. ; Drongelen, A. van ; Marsman, L.A.
    Air Traffic Controllers face numerous fatigue-related challenges due to irregular working hours and demanding workload. In response to European regulations aimed at preventing fatigue and stress, a scientific evaluation funded by the European Union Aviation Safety Agency was undertaken across member states. The objective of this study, as one of the most comprehensive to date in Europe, is to assess fatigue risk levels and identify contributing factors within current operations. The research methodology combined various data collection methods across European Air Traffic Service Providers, including an evaluation of current scheduling practices and fatigue management alongside a field data collection in representative entities. Sleep, fatigue, and workload data of 216 volunteers were collected and validated by sleep actigraphy measurements. Statistical analysis of fatigue data on fatigue risk exposure revealed that 5.6% of analyzed duties were associated with critical levels of fatigue. The top five factors contributing to these critical levels are night shifts, challenging weather conditions, monotonous traffic situations, accumulated sleep debt, and extended working hours without breaks. Several recommendations were elaborated to improve fatigue prevention and mitigation at predictive, proactive and reactive levels, encompassing improvements to the rostering process, enhanced fatigue monitoring mechanisms, and practical interventions within organizations.
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    Assessment of the cooperation between driver and vehicle automation: A framework
    (Elsevier, 2023) Tinga, A.M. ; Petermeijer, S.M. ; Reus, A.J.C. de ; Jansen, R.J. ; Waterschoot, B.M. van
    As long as the human driver is responsible for part(s) of the driving task during automated driving, the driver and automated driving system are sharing the driving task. Such a shared task is characterized by shared control, in which cooperation between the driver and vehicle automation is essential. However, means to holistically assess the quality of this cooperation are currently lacking. This work addresses how cooperation between driver and vehicle automation can be operationalized and assessed to gain insight into the quality of the shared driving task. Quality indicators and measurement methods are identified across seven dimensions reflective of the quality of cooperation between driver and automation. Based on previous empirical and theoretical studies a total of 34 quality indicators are identified. The methods to measure these quality indicators fall into four categories: 1) Subjective (such as questionnaires); 2) behavioral (such as reaction times, steering response); 3) neurophysiological (such as heart rate and pupil size); and 4) heuristic evaluation. The result is a first step in the development of a framework for the quantitative assessment of cooperation in the shared driving task. Yet, important knowledge gaps remain. For instance, the exact contribution of each quality indicator and their exact interrelationship are currently unclear. Moreover, all quality indicators reflect a requirement that should be met. Further research is needed to define exactly when each requirement is met. Additionally, it should be established to what degree each measurement method can validly and reliably provide insight into their quality indicator. Therefore, to ultimately ensure valid and reliable application of the framework in practice, the framework should continue to be developed and improved upon in future work.
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    Attention Guidance for Tower ATC using Augmented Reality Devices
    (IEEE, 2022) Teutsch, J. ; Bos, T.J.J. ; Apeldoorn, M.C. van ; Camara, L.
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    ATTILA Tiltrotor Whirl Flutter Code-to-Test Correlation
    (Vertical Flight Society, 2025) Hoff, S.C. van 't ; Fonte, F. ; Velo, A. ; Vita, P. de ; Cassoni, G. ; Masarati, P.
    This paper presents the results of an ongoing correlation study performed using three different comprehensive rotorcraft codes and data obtained from the Advanced Testbed for TILtrotor Aeroelastics (ATTILA) tiltrotor whirl flutter wind tunnel test campaign. The ATTILA testbed consists of a 1:5 scale semi-span wing with a powered, tip-mounted proprotor reflecting the proprietary design of the Next Generation Civil TiltRotor (NGCTR). Experimental dynamic characterization of the testbed has revealed non-negligible structural nonlinearities. Post-test efforts have focused on refining the damping trends extracted from the test data, and correlating the experimental results with numerical predictions. The objective of this paper is to assess the modelling fidelity required and afforded by modern comprehensive aeromechanics codes to predict tiltrotor whirl flutter instability given an industry-representative design that exhibits structural nonlinearities. Baseline numerical flutter models fail to predict some of the observed experimental damping behaviour, but the inclusion of higher fidelity aerodynamics and exploratory friction models improves prediction accuracy. Ongoing modelling and dynamic characterization efforts aim to further clarify the mechanisms influencing the whirl flutter stability of the ATTILA testbed and enhance the predictive capabilities of the numerical methods employed.
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    Augmented Intelligence for Instructional Systems in Simulation-Based Training
    (Springer, 2024) Oijen, J. van
    Augmented Intelligence is a design pattern for a human-centered collaboration model of people and artificial intelligence (AI), where machines assist humans in tasks such as data analysis, information retrieval, decision-making, and task execution. In this study, the concept of Augmented Intelligence is applied within the context of an instructional system for simulation-based training. Here, the collaboration between human and machine is focused on the role of the instructor, which is to guide the learning process of one or more trainees toward some learning objective. We identify different levels of machine support to assist an instructor in this role during an adaptive training cycle. Additionally, two design aspects are discussed that contribute to increased levels of intelligence, namely the challenge of domain alignment to empower automation capabilities, and the benefits of simulation-based task environments to deliver AI-enabled approaches. Examples are discussed in the context of military training.
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    Beamforming in an annular duct with swirling flow
    (AIAA, 2023) Sijtsma, P. ; Brouwer, H. ; Snellen, M.
    The fan-stator stage of turbofan engines is one of the main regions of broadband noise generation. The trend of increasing bypass ratios will make fan-stator broadband noise even more significant, as jet noise will decrease and nacelles will become shorter, thus leaving less space for liners. Within the fan-stator stage there are several aerodynamic phenomena that can cause broadband noise. However, techniques for experimental identification and quantification (and thus classification) of these broadband noise sources are still immature. Beamforming using in-duct microphones is feasible, but a major challenge is the strong rotational component of the flow that needs to be accounted for in the steering vectors. This paper proposes a solution for that challenge, based on a fast ray tracing approach. With synthesized microphone array data, calculated with an approximate method for the Green’s function in a ducted swirling flow, it is demonstrated that detection of acoustic sources is possible.
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    Braking Capabilities on Flooded Runways: Flight Test Results Obtained with a Business Jet
    (AIAA, 2017) Es, G.W.H. van
    Statistics show that the likelihood of a runway excursion during takeoff or landing is much higher on flooded runways than on dry runways. Extreme loss of tyre braking can occur during rejected takeoffs and landings on flooded runways. As a result the stopping distance increases significantly and could exceed the available runway length. Most research in the past has focused on the braking capabilities of aircraft on wet runways instead of flooded runways. Most of the knowledge of aircraft braking performance on flooded runways was gained with older aircraft designs. This knowledge is still used to determine the takeoff and landing performance of today’s modern aircraft. During the development of the European Action Plan for the Prevention of Runway Excursions it was recognised that current aircraft designs may act differently when braking on water flooded runways from aircraft tested earlier, due to new tyres and anti-skid system designs. Also the water depths during these earlier tests were often just above the wet-flooded runway threshold. Flight tests with more modern aircraft designs were therefore scheduled as part of a research project under EU’s Horizon 2020 Research and Innovation Programme. This paper summarises the flight tests conducted with a Cessna Citation II aircraft on a flooded runway. Unbraked and braked tests were conducted in a specially constructed water pond at different ground speeds. Numerous parameters were recorded during each test run including accelerations, speeds, engine performance, etc. From the test data, effective braking friction for different grounds speeds were derived, contamination drag levels were established, and insight into the hydroplaning characteristics under unbraked and braked conditions were obtained.
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    Breadboard Testing of a HiPeR Inflatable Radiator (HiPeR INFRA)
    (49th International Conference on Environmental Systems, 2019) Groot, T. de ; Schwieters, B. ; Benthem, R.C. van ; Pauw, A. ; Es, J. van
    With a twenty times higher thermal conductivity per unit mass than aluminium, pyrolytic graphite (PG) offers great potential in the application to spacecraft thermal control systems. Over the last years, Airbus Defence and Space Netherlands (Airbus DS NL) has been developing thermal control applications for this material. The patented High Performance Radiator (HiPeR) uses the PG to efficiently spread the heat from a heat source over a large radiative area. Recently, Airbus DS NL and the Royal Netherlands Aerospace Centre (NLR) have been working on a HiPeR Inflatable Radiator (INFRA) application. This concept consists of a HiPeR radiator and a single phase fluid loop. Flexible tubing enables the radiator to be rolled up to a small stowed volume. Once in orbit, the system pressure is increased, triggering the radiator to unroll and maintain its shape over the mission lifetime. Heat is supplied via the same fluid tube that gives the radiator its shape, making use of a dedicated mini-pump. To validate the functional design, a breadboard model has been made. Deployment and thermal performance have been tested successfully. Based on the measured data, the thermal performance of an INFRA system operating at a 45 °C root temperature in a space environment with a sink temperature of -270 °C would be approximately 300-325 W/m2, corresponding to a radiator efficiency of approximately 60%. This performance is deemed to be competitive, especially considering the mass-to-power (expected <10 kg / kW after a design iteration) and small stowed volume of such a system. Additionally, a small-scale breadboard test of protection measures against micro-meteoroids and orbital debris (MMOD) has yielded promising results. The revised design includes MMOD shielding in the form of bi-stable metal strips with a resulting probability of no penetration of the kapton fluid tubing of 0,9 over a lifetime of 15 years.