Ikkoh Funaki

• Japan Aerospace Exploration Agency

Hollow cathodes are widely used as electron sources in electric propulsion systems owing to their high electron generation efficiency. Research findings allude to the significant impact of the temperature and plasma characteristics of the emitter region of a hollow cathode, which supplies thermionic electrons, on its operation. However, these chara...

This paper explores the innovative direction control of rotating detonation waves in rotating detonation engines (RDEs) by adjusting the ignition location and employing helical combustors with a sinusoidal cross section. In our experimental setup, we conducted 25 combustion tests using two distinct combustor geometries, each featuring different hel...

This study measured the two-dimensional orifice plate surface temperature of a 20-A-class LaB6 hollow cathode using a near-infrared two-color radiation thermometer. The thermometer technique resolved the orifice plate temperature with an accuracy of approximately 166 ℃. With this technique, the surface temperature of the orifice plate was found nea...

Space sails are a continuum of lightweight, thin, large-area, deployable technologies which are pushing forward new frontiers in space mobility and exploration. They encompass solar sails, laser-driven sails, drag sails, magnetic sails, electric sails, deployable membrane reflectors, deployable membrane antennas, and solar power sails. Some have be...

A coupled cylindrical rotating detonation engine (RDE) with two cylindrical RDEs (both combustors had a combustor inner diameter of 23 mm and an axial length of 30 mm) placed next to each other was tested for rocket clustering application. The objective of the experiment was to achieve two-engine synchronized initiation with a single igniter. Exper...

This study measured the two-dimensional orifice surface temperature of a 20-A-class LaB 6 hollow cathode using a near-infrared two-color radiation thermometer. The thermometer technique resolved the orifice plate temperature with an accuracy of approximately 123 ℃. With this technique, the surface temperature of the orifice was found nearly uniform...

There are few experimental studies on rotating detonation engines (RDEs) with liquid propellants. This study reveals the static thrust performance of a cylindrical RDE with ethanol and liquid nitrous oxide as propellants under atmospheric pressure. This RDE had an inner diameter of 40 mm, a maximum combustor length of 230 mm, a nozzle contraction r...

This review deals with the selection of the electric propulsion system (EPS) for the internationally developed and designed, primary nuclear-electric space tug International Nuclear Power and Propulsion System (INPPS). INPPS is scheduled for interplanetary missions to Mars and Jupiter moon Europa missions by the end of decade 2020. Regarding specif...

Magsail is a space propulsion system using the interactions between the solar wind and the magnetic field generated by the onboard coils. Magnetoplasma sail is a propulsion system that increases thrust by expanding the magnetosphere through plasma injection from the spacecraft. There are two mechanisms on the magnetospheric inflation: method using...

Rotating detonation engines (RDEs) have been actively researched around the world for application to next-generation aerospace propulsion systems because detonation combustion has theoretically higher thermal efficiency than conventional combustion. Moreover, because cylindrical RDEs have simpler combustors, further miniaturization of conventional...

This paper presents a control algorithm for ensuring the stable operation of a 6 kW Hall thruster. The Japan Aerospace Exploration Agency is developing a “wide-range” power processing unit (PPU) to power a 6 kW Hall thruster system, a candidate for all-electric satellites. The PPU provides discharge oscillation, power, and discharge current control...

The inner flow containing the ignition process of a throatless and diverging (constant diverging angle α=5 deg) rotating detonation engine (RDE) was experimentally investigated by both optical observation and pressure measurement. An RDE that had an acrylic engine wall with a length of 70 mm and an inlet diameter of 20 mm was tested under a low bac...

To create a new flyable detonation propulsion system, a detonation engine system (DES) that can be stowed in sounding rocket S-520-31 has been developed. This paper focused on the first flight demonstration in the space environment of a DES-integrated rotating detonation engine (RDE) using S-520-31. The flight result was compared with ground-test d...

A detonation engine system is successfully demonstrated for the first time in space using sounding rocket S-520-31 of the Japan Aerospace Exploration Agency/Institute of Space Astronautical Science. Detailed flight results of an S-shaped pulse detonation engine (PDE) installed in the rocket are presented herein. The flight is conducted to confirm t...

This paper presents a control algorithm for ensuring the stable operation of a 6 kW Hall thruster. The Japan Aerospace Exploration Agency is developing a “wide-range” power processing unit (PPU) to power a 6 kW Hall thruster system, a candidate for all-electric satellites. The PPU provides discharge oscillation, power, and discharge current control...

View Video Presentation: https://doi.org/10.2514/6.2022-4143.vid Rotating detonation combustor (RDC) is one of the combustors using detonation waves, which are hypersonic combustion waves, and is expected to simplify the system and improve thermal efficiency due to their hypersonic combustion and compression performance by shock waves. Most of thes...

Converging–diverging nozzles are common in rocket engine systems to increase the exhaust velocity and improve thrust performance. In this study, we focused on the acceleration of subsonic burned gas without a structural throat via detonation to realize a simple and compact engine. We developed and tested a rotating detonation engine (RDE) without a...

This paper presents the results of an S-shaped pulse detonation engine (PDE) ground firing test in the form of a detonation engine system. The world’s first technology demonstration of PDE in space using a sounding rocket is planned, and the aim is to control the rocket spin rate in the axial direction using pulsed detonation. The PDE operation at...

View Video Presentation: https://doi.org/10.2514/6.2022-1454.vid Rotating detonation combustion was successfully tested for liquid ethanol and gaseous oxygen heterogeneous mixture in cylindrical combustor for the first time. The rotating detonation combustor (RDC) we operated has a diameter of 20 mm and variable lengths of 60, 210 mm. Pure ethanol...

View Video Presentation: https://doi.org/10.2514/6.2022-0230.vid Detonation engines exert various characteristics and high propulsion performance depending on their operation modes. Our group has conducted the demonstration of the integrated RDE/PDE system (Detonation Engine System, DES) in outer-space environment using a sounding rocket named S-52...

View Video Presentation: https://doi.org/10.2514/6.2022-0232.vid To create a new flyable propulsion system, Detonation Engine System (DES) has developed which can be stowed in the sounding rocket S-520-31. This paper focused on the first flight demonstration of RDE in space environment, which is integrated into DES, using S-520-31. The flight resul...

View Video Presentation: https://doi.org/10.2514/6.2022-0233.vid A research team of Nagoya University, Keio University, Muroran Institute of Technology, and Institute of Space and Astronautical Science (ISAS) at Japan Aerospace Exploration Agency (JAXA) successfully conducted a space demonstration of the detonation engine system (DES) using the S-5...

View Video Presentation: https://doi.org/10.2514/6.2022-0229.vid A research group at Nagoya University, in collaboration with Keio University, the Muroran Institute of Technology, and Institute of Space and Astronautical Science at the Japan Aerospace Exploration Agency (ISAS/JAXA), has successfully demonstrated world’s first operation of Detonatio...

View Video Presentation: https://doi.org/10.2514/6.2022-0231.vid A joint project team of Nagoya University, Keio University, Muroran Institute of Technology, and Institute of Space and Astronautical Science at Japan Aerospace Exploration Agency developed Detonation Engine System (DES) toward an in-space flight demonstration on a sounding rocket S-5...

The ion energy angle distribution and its relationship to plasma parameters for spot and plume modes are elucidated for a LaB6 hollow cathode with a radiative heater. Measurements were conducted using a retarding potential analyzer (RPA) and a single Langmuir probe. The ion energy distribution function (IEDF) characteristics showed different tenden...

INPPS Flagship Structure & Subsystems, Ground Based Tests, Pure NEP, International Electric Thrusters, Humans Internationally To Mars

A cylindrical rotating detonation engine (24 mm diameter) with multiple injector holes on the combustor side wall for both propellant injection and cooling by injector gas flow was designed and tested. As each set of injectors created its own detonations, the synchronized detonation waves propagated along the three injector rows. From the axial vie...

In this study, a 2D two-color pyrometer was developed to measure the cathode surface temperature distribution of a high-power hydrogen magnetoplasmadynamic thruster. The developed measurement system consists of an object lens, a beam splitter, bandpass filters, and two cameras. Wavelengths of 950 and 980 nm were selected to achieve a high signal-to...

In order to improve ion engine's performance, the neutralization performance with two field emission cathodes in an ion engine is investigated. The neutralization performance is evaluated by the potential difference between cathode and ground, using a 100μN class ion thruster developed at Kyushu University and two 50×50mm² field emission cathodes w...

The Japan Aerospace Exploration Agency (JAXA) has developed a power processing unit (PPU) for a 6 kW Hall thruster system. The PPU is a candidate for future mission applications, such as all-electric satellites, exploration vehicles, and orbital transfer services. The PPU has to be small and still provide a wide output range of outputs, consider th...

For rotating detonation engines, the high-pressure region behind the detonation causes backflow into the plenum, making it difficult to properly design injectors to achieve the target pressure balance due to blockage of a part of the injector area during engine operation. In this paper, we present the pressure and thrust measurement of a rotating d...

A rotating detonation engine (RDE) generates a continuous thrust with one or more rotating detonation waves. Because of the velocity on the order of kilometers/second, the reaction zone is relatively small. Therefore, the RDE realizes a short combustion chamber length. However, the detonation waves induce an azimuthal motion of propellant, resultin...

View Video Presentation: https://doi.org/10.2514/6.2021-3657.vid This study focused on acceleration of propellant to supersonic speed with a compact engine. Increase in the exhaust velocity of a rocket engine leads to improvement of the thrust performance. Several combustion tests were conducted for a small rotating detonation engine (RDE) whose ch...

View Video Presentation: https://doi.org/10.2514/6.2021-3650.vid A cylindrical RDE with a propellant injection cooling system with an injector on the entire wall surface of the combustor has been tested and demonstrated. In this study, in order to search the optimum flow balance between the side and the bottom, the experiment was conducted under a...

View Video Presentation: https://doi.org/10.2514/6.2021-3388.vid The relationship between the magnetic field strength and the plasma parameters of a hollow cathode was investigated experimentally. The ion energies, discharge currents, and ion currents were measured under a magnetic field, ranging from 0 mT to 12 mT of the magnetic field strength. W...

The first non-human INPPS (International Nuclear Power and Propulsion System) flagship flight with orbits Earth-Mars-Earth-Jupiter/Europa (after 2025) is the most maximal space qualification test of INPPS flagship to carry out the second INPPS flagship flight to Mars with humans (in the 2030th). This high power space transportation tug is realistic...

2020/2021 orbit calculations (DLR Bremen + MAI Moscow): 3 Orbits for one non-human MARS/EUROPA-INPPS flagship 1. Orbit Earth (11 Oct 2026) => Mars (28 Jan 2028); 2. Orbit Mars (22 Sept 2028) => Earth (29 Jul 2029); 3. Orbit Earth (12 Oct 2031) => Jupiter / Europa (6 Dec 2035) 22 ETs (for the INPPS flagship CET): example - gridded CET plate with com...

Rotating detonation Engine (RDE) is highly expected for the future propulsion systems due to its more compact structure than conventional internal combustion engines. It is because detonation waves circling in the order of km/s compress propellant instead of the mechanical complex compressor. Of interest on RDE, the torque around the z axis is impo...

An engine cooling concept for cylindrical rotating detonation engine which had an injector surface on the combustor side wall has been tested with three combustor length of 21, 30, and 6 mm. Thrust measurement of the cylindrical RDE (24-mm-diameter) was conducted with monitoring K-type thermocouples inserted in combustor wall. Single rotating deton...

This Paper presents the results of a rotating detonation engine rocket sled test demonstration on a 127 mm gauge rail at 100 m long high-speed running track test equipment to evaluate the thrust performance of a stand-alone rotating detonation engine propulsion system. The developed sled test demonstrator contained all onboard subsystems, including...

A detonation is a combustion wave that propagates at a supersonic speed (2-3 km/s) in a combustible mixture. There are many fundamental studies of detonation waves and detonation engine systems. The detonation cycle has a higher thermal efficiency than a conventional constant-pressure combustion cycle.

This Paper explores keeper ignition and discharge characteristic of a hollow cathode center mounted on a Hall thruster to discuss the optimum startup sequence. A strong magnetic field along the hollow cathode in the center-mount configuration is considered to play an important role in the ignition and discharge; however, the characteristics in this...

Multi-pole magnetosphere has complex magnetic fields and current distribution. We focused on the structure for the thrust performance improvement of the magnetic sail. Magnetic sail is a propulsion system using the solar winds and artificial magnetic fields on the coil mounted on spacecrafts. We made the multipole coil, it generates complex magneti...

An engine cooling concept for cylindrical rotating detonation engine which had an injector surface on the combustor side wall has been tested and demonstrated. Thrust measurement of the cylindrical RDE (24-mm-diameter) was conducted with monitoring K-type thermocouples inserted in combustor wall. Single rotating detonation wave was observed in the...

The internal flow structures of detonation wave were experimentally analyzed in an optically accessible hollow rotating detonation combustor with multiple chamber lengths. The cylindrical RDC has a glass chamber wall, 20 mm in diameter, which allowed us to capture the combustion self-luminescence. A chamber 70 mm in length was first tested using C2...

This study evaluated the propulsion performance of a nozzleless, cylindrical rotating detonation engine (RDE). Using a C2H4–O2 mixture, the RDE was tested in a low-back-pressure environment at propellant mass flow rates of 8–45 g/s. In high-speed imaging of the self-luminescence within the combustor, rotating luminous regions were observed at mass...

A 2-kW-class magnetically shielded Hall thruster was developed, and its performance was evaluated. Additionally, the effects of the discharge channel length, thruster body potential, anode dielectric coating, and vacuum facility on its performance were investigated. A low discharge channel erosion rate of the thruster configuration with a normalize...

It is described the interplanetary INPPS flagship for Mars and Europa space exploration - without and with humans. INPPS - the International Nuclear Power and Propulsion System - fulfill all necessary UN regulations for NPS (Nuclear Power Source) in space: orbiting small satellites and the flagship itself will be equipped with particle and gamma ra...

To meet the growing demand for all-electric propulsion satellite, a 6-kW-class Hall thruster was newly fabricated and tested in laboratory. A Hall thruster that has an annular ceramic channel in 150-mm effective diameter and a centered hollow cathode was designed to optimize thrust performance with an appropriate channel-geometry and magnetic-field...

This paper describes the results of the European-Russian DEMOCRITOS and MEGAHIT projects related to the electric thrusters on board the International Nuclear Power and Propulsion System (INPPS) flagship. INPPS flagship is a high power space transportation hybrid tug (power supply primary by nuclear power, by auxiliary solar power ring and chemical...

This paper explicitly explains INPPS (International Nuclear Power and Propulsion System) flagship subsystems like nuclear reactor, shielding, power conversion, boom, radiators, building blocks for tanks / payload basket / PPU / cluster of electric thrusters as well as additional solar power ring electricity and real time radiation detectors. Differ...

This presentation addresses iBOSS (intelligent Building Blocks for On-Orbit Satellite Servicing and Assembly) as building blocks for non-nuclear sub-systems in INPPS (International Nuclear Power and Propulsion System) flagship. iBOSS are ideal mechanical, thermal, fluidic and data standardized building blocks to be used in autonomous robotic in-spa...

The presentation summarizes INPPS (International Nuclear Power and Propulsion System) flagship non-human (2020th) and human (2030th) Mars exploration missions. The 2020th first flagship space flight is the complex, complete test mission for the second flagship towards Mars with humans (2030th). The most efficient approach is the completely tested f...

R＆D of Hall thruster for all-electric satellite is in progress at Japan Aerospace Exploration Agency. Design, fabrication and testing of breadboard model (BBM) Hall thrusters were conducted for the flight experiment onboard Engineering Test Satellite 9 (ETS-9). Performance evaluations of BBM4 thruster obtained an Isp of 1,900s at a discharge voltag...

The plasma flow of a LaB6 hollow cathode was simulated using hybrid-PIC (Particle In Cell) model, and was compared with the experimental data measured along the center axis with a Langmuir probe. As an anomalous resistivity model, IAT (Ion Acoustic Turbulence) growth model was used not to overestimate the anomalous effect. In the numerical model, t...

A detonation is a combustion wave that propagates at supersonic speed (2∼3 km/s) in a combustible mixture. There are many fundamental studies of detonation waves and detonation engine systems. The detonation cycle has a higher thermal efficiency than a conventional constant-pressure combustion cycle. Therefore, it is expected that a high-efficiency...

The development of new propulsion system for exploring the moon and other planets in the solar system or deep space is necessary to achieve short mission term and large payload ratio. In recent years, magnetic nozzle is focused on as the candidate system to attain above objectives. Magnetic nozzle is the system which generates the thrust by convert...

Detonation engines have higher thermal efficiency than conventional engines. It is capable of shortening the combustor since the combustion process of detonation completes in quite a short time. Therefore, many researches on detonation engines have been conducted around the world. An RDE can be used as a kick rocket motor for deep-space exploration...

A lanthanum hexaboride (LaB6) hollow cathode with radiatice heater has been developed for high power Hall thruster neutralzier. The influences of orifice and keeper shapes on the performance of the hollow cathode and on its operating characteristics are investigated by measuring the discharge voltage and current. Six different orifice shapes are us...

This paper discusses a transfer system between the Earth and Mars orbit using electric propulsion under the assumption of launching the H-IIA launch vehicle on a one-way trip. The spacecraft was assumed to be launched into the geocentric orbit, then transferred to the Earth’s heliocentric orbit using electric propulsion or a kick motor, and further...

Numerical simulation of plasma flow and the self-heating characteristics of a LaB6 hollow cathode were performed using a hybrid-PIC model. For a discharge current of 30 A and mass flow rate of 3 mg/s, the influences of an emitter temperature profile and model parameter included in an anomalous resistivity model on the plasma flow and energy flux we...

A 1,000-hours preliminary life test of a 6-kW-class xenon Hall thruster for Engineering Test Satellite-9 (ETS-9) was conducted by using a bread board model thruster. Thrust degraded by approximately 2% before and after the test, which is mainly attributed to erosion and contamination of discharge channel made of boron nitride. The thruster was disa...

For a self-field magnetoplasmadynamic (MPD) thruster using hydrogen propellant, plasma flows were numerically simulated with a model including the ion-slip effect. To clarify the thruster behavior near the critical current, the discharge current and the propellant mass flow rate were set to 5 or 10 kA (critical current) and 0.4 g/s, respectively. A...

Geometric throats are commonly applied to rocket combustors to increase pressure and specific impulse. This paper presents the results from thrust measurements of an ethylene/gas-oxygen rotating detonation engine with various throat geometries in a vacuum chamber to simulate varied backpressure conditions in a range of 1.1–104 kPa. For the throatle...

Measurements in the infrared wavelength domain allow direct assessment of the physical state and energy balance of cool matter in space, enabling the detailed study of the processes that govern the formation and evolution of stars and planetary systems in galaxies over cosmic time. Previous infrared missions revealed a great deal about the obscured...

We attempted to test suitability of a commercial precision balance as a simple alternative sub-miliNewton resolution continuous thrust stand on a vertically oriented 300W-class Hall thruster. Measured thrust data was in the range of 1-10 mN with a maximum error of 0.1 mN. The performance of the precision balance was compared to the performance of a...

We describe the critical condition necessary for the inner cylinder radius of a rotating detonation engine (RDE) used for in-space rocket propulsion to sustain adequate thruster performance. Using gaseous C2H4 and O2 as the propellant, we measured thrust and impulse of the RDE experimentally, varying in the inner cylinder radius r i from 31 mm (typ...