Miniature Water Ion Thruster; 1 km/s-class Delta-V for a 6U CubeSat

A propulsion system gives CubeSats the capacity to change their orbit on their own, and in terms of achieving a large delta-V, electric propulsion has an advantage. Installing the electric propulsion on CubeSats has difficulties such as a high-pressure gas system, electrical components, and the drop of the efficiency because of the miniaturization. To clear these problems, the water ion thruster is proposed as a candidate for the CubeSats’ electric propulsion. Water has an absolute advantage of applying for CubeSats’ propulsion system in the point of safety. In addition, water is a liquid phase at room temperature and atmospheric pressure, and it makes easy to store and handle it. The thrust measurement and the improvement of the thruster based on experiments were conducted. The thrust and the specific impulse were estimated as 226 ± 19 μN and 384 ± 33 s at the highest performance point with 36.5 W power consumption of all system. It achieved a delta-V of 504 ± 43 m/s with the 1 kg of propellant for an 8 kg and 6U CubeSat

Pre-Flight Testing Results of Multiple Water Propulsion Systems - Resistojet and Ion Thruster for SmallSats

This paper described re-flight flight testing results of the miniature water propulsion system combined an ion thruster and resistojet thrusters which is to be demonstrated on-orbit by JAXA’s program named Innovative Satellite Technology Demonstration-3. The unified propulsion system has a huge potential to expand micro/nano-spacecraft utilization and decrease the risk of debris

Multiple Water Propulsion Systems: All Propulsive Capabilities for CubeSats From LEO to Deep Space

The proposal is a multiple water propulsion system which combines a water resistojet and water ion thruster

Infrared and hard X-ray diagnostics of AGN identification from the Swift/BAT and AKARI all-sky surveys

We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10keV) properties for local active galactic nuclei (AGN). The Swift/Burst Alert Telescope all-sky survey provides an unbiased, flux-limited selection of hard X-ray detected AGN. Cross-correlating the 22-month hard X-ray survey with the AKARI all-sky survey, we studied 158 AGN detected by the AKARI instruments. We find a strong correlation for most AGN between the infrared (9, 18, and 90 micron) and hard X-ray (14-195 keV) luminosities, and quantify the correlation for various subsamples of AGN. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution. The correlation for radio galaxies has a slope and normalization identical to that for Seyfert 1s, implying similar hard X-ray/infrared emission processes in both. In contrast, Compton-thick sources show a large deficit in the hard X-ray band, because high gas column densities diminish even their hard X-ray luminosities. We propose two photometric diagnostics for source classification: one is an X-ray luminosity vs. infrared color diagram, in which type 1 radio-loud AGN are well isolated from the others in the sample. The other uses the X-ray vs. infrared color as a useful redshift-independent indicator for identifying Compton-thick AGN. Importantly, Compton-thick AGN and starburst galaxies in composite systems can also be differentiated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new and upcoming surveys such as WISE and NuSTAR.Comment: 17 pages, 5 figures, 5 tables. Accepted for publication in the Astrophysical Journa

Development of Water Gridded Ion Thruster for Small Satellites: Toward On-Orbit Demonstration

Water as a propellant has many advantages and does not require a pressure vessel for storage. Its high safety level can reduce development cost and time. It is also a resource tightly tied to human spaceflight and found in-situ in the upcoming moon missions. Stored in its liquid state in our thrusters, it is then vaporized at room temperature and low pressure. The resulted steam is then injected in the discharge chambers where it is transformed into plasma. Plasma generation is achieved through flight-proven microwave discharge using Electron Cyclotron Resonance

Superconductivity protected by spin-valley locking in ion-gated MoS2

Symmetry-breaking has been known to play a key role in noncentrosymmetric superconductors with strong spin-orbit-interaction (SOI). The studies, however, have been so far mainly focused on a particular type of SOI, known as Rashba SOI, whereby the electron spin is locked to its momentum at a right-angle, thereby leading to an in-planar helical spin texture. Here we discuss electric-field-induced superconductivity in molybdenum disulphide (MoS2), which exhibits a fundamentally different type of intrinsic SOI manifested by an out-of-plane Zeeman-type spin polarization of energy valleys. We find an upper critical field of approximately 52 T at 1.5 K, which indicates an enhancement of the Pauli limit by a factor of four as compared to that in centrosymmetric conventional superconductors. Using realistic tight-binding calculations, we reveal that this unusual behaviour is due to an inter-valley pairing that is symmetrically protected by Zeeman-type spin-valley locking against external magnetic fields. Our study sheds a new light on the interplay of inversion asymmetry with SOI in confined geometries, and its unprecedented role in superconductivity.Comment: 37 pages, 11 figures, http://meetings.aps.org/Meeting/MAR15/Session/G11.1

On-Orbit Demonstration of the Water Resistojet Propulsion System on Commercial 6U-Sat SPHERE-1 EYE

SPHERE-1 EYE, a 6U CubeSat developed by Sony Group Corporation, was launched at the beginning of 2023. The satellite included a water resistojet propulsion system, which is designed for orbit raising after the initial checkout. The water resistojet propulsion system consists of a tank, a vaporizer, nozzles, a control board, and a power processing unit. The form factor of the propulsion system is 1.25 U, the wet mass is 1.4 kg, and the achievable total impulse of the system is 170 Ns or higher. A unique design of the water propulsion system is a vaporization chamber generating steam at room temperature and low pressure, under 10 kPa. The performance measured on the ground shows a thrust of 2.7 mN, and a specific impulse of 60 s. A qualification test campaign including vibration, shock, thermal, throughput, and system performance tests was conducted, followed by acceptance tests. On-orbit demonstration was conducted on March 3rd and 16th for all four nozzles and the thrust generation was confirmed. The estimated thrust on orbit was 6.1 - 7.2 mN. Comparison between the on-orbit results and the ground tests demonstrated the functionality of the system as anticipated