Providing Nanosatellite Triaxial Gravitational Orientation Using Magnetic Actuators

Three-axis gravity stabilization of 3U CubeSat is achieved due to selection of the nanosatellite moments of inertia at the design stage, as well as special modes included in the algorithm to provide stabilization of CubeSat relative to each motion channel separately. In this paper, we propose a modified algorithm based on the magnetic stabilization algorithm B-dot. The modified algorithm provides three modes intended to damp the initial angular velocity to the value of the orbital angular velocity, to keep the angular velocity at a value close to that of the orbital angular velocity, and to provide the nanosatellite gravitational triaxial stabilization by using one magnetic coil located on the axis with the transversal moment of inertia, which is possible due to the small angle between the magnetic field line and the satellite's trajectory. We propose two modifications for forming a control loop for orientation and stabilization of the 3U CubeSat: the first one uses measurements from magnetometers and angular rate sensors as feedback, and the second one, only magnetometers. The efficiency of the two modifications of modifications was studied by means of statistical modeling.

Transient Attitude Motion of TNS-0#2 Nanosatellite during Atmosphere Re-Entry

Attitude motion reconstruction of the Technological NanoSatellite TNS-0 #2 during the last month of its mission is presented in the paper. The satellite was designed to test the performance of the data transmission via the Globalstar communication system. This system successfully provided telemetry (even during its atmosphere re-entry) up to an altitude of 156 km. Satellite attitude data for this phase is analyzed in the paper. The nominal satellite attitude represents its passive stabilization along a geomagnetic field induction vector. The satellite was equipped with a permanent magnet and hysteresis dampers. The permanent magnet axis tracked the local geomagnetic field direction with an accuracy of about 15 degrees for almost two years of the mission. Rapid altitude decay during the last month of operation resulted in the transition from the magnetic stabilization to the aerodynamic stabilization of the satellite. The details of the initial tumbling motion after the launch, magnetic stabilization, transition phase prior to the aerodynamic stabilization, and subsequent satellite motion in the aerodynamic stabilization mode are presented.

Attitude Analysis of Small Satellites Using Model-Based Simulation

CubeSats, and small satellites in general, being small and relatively light, are sensitive to disturbance torques in the orbital environment. We developed a simulation tool that includes models of the major environmental torques and small satellite experiences in low Earth orbit, which allows users to study the attitude response for a given spacecraft and assist in the design of attitude control systems, such as selecting the magnet strength when using passive magnetic stabilization or designing the shape of the spacecraft when using aerodynamic attitude stabilization. The simulation tool named the Smart Nanosatellite Attitude Propagator (SNAP) has been public in precompiled form and widely used since 2010; this paper accompanies the release of SNAP’s source code with the inclusion of new models for aerodynamic torque and other new features. Details on internal models are described, including the models for orbit propagation, Earth’s magnetic field, gravity gradient torque, spacecraft shape modelling and aerodynamic torque, permanent magnetic dipole torque, and magnetic hysteresis. A discussion is presented on the significance of aerodynamic torque and magnetic hysteresis on a magnetically stabilized 3-unit CubeSat in the orbit of the International Space Station, from which many small satellites are deployed.

Design and Numerical Validation of an Algorithm for the Detumbling and Angular Rate Determination of a CubeSat Using Only Three-Axis Magnetometer Data

A detumbling algorithm is developed to yield three-axis magnetic stabilization of a CubeSat deployed with unknown RAAN, orbit phase angle, inclination, attitude, and angular rate. Data from a three-axis magnetometer are the only input to determine both the control torque and the angular rate of the spacecraft. The algorithm is designed to produce a magnetic dipole moment which is constantly orthogonal to the geomagnetic field vector, independently of both the attitude and the angular rate of the rigid spacecraft. The angular rates are calculated in real time from magnetometer data, and the use of a second-order low-pass filter allows to rapidly reduce the measurement error within ±0.2 deg/sec. Numerical validation of the algorithm is performed, and a variety of feasible scenarios is simulated assuming the CubeSat to operate in low Earth orbit. The robustness of the algorithm, with respect to unknown deployment conditions, different sampling rates, and uncertainties on the moments of inertia of the CubeSat, is verified.

Effect of a homogeneous magnetic field on the electrospraying characteristics of sulfolane ferrofluids

We explore the effect of an applied homogeneous magnetic field on the electrospraying characteristics of a ferrofluid in the cone-jet mode. A sulfolane-based ferrofluid mixed with the ionic liquid ethyl ammonium nitrate has been synthesized. These mixtures have negligible volatility under ambient conditions and remain stable under a very wide range of electrical conductivities $K$. Magnetized Taylor cones spray with the same current emission characteristics as their non-magnetized counterparts in the shared voltage and flow rate parameter space. However, the magnetized Taylor cones studied remained stable at voltages 23 % lower than the non-magnetized spray; they also access flow rates 30 % and 40 % lower in ferrofluids with $K=0.3$ and $0.01~\text{S}~\text{m}^{-1}$. In the lower voltage ranges available only to magnetized tips, unusually long stable cones are observed. The magnetic stabilization mechanism responsible for these two effects remains unclear. It is noteworthy that these strong effects arise even when the tip curvature of the strictly magnetized liquid is orders of magnitude smaller than that for the strictly electrified liquid.

High-Performance Microchannels Development Using Magnetic Stabilization

Creating a large surface area from a packed bed of particles is a necessary step for many packing, chemical, and heat transfer applications. However, the excessive pressure drop across the packed bed is not desirable in many of these applications. This problem can be addressed by using microchannels instead of the packed bed of particles, providing a high heat transfer rate at the acceptable pressure drop range. Microchannels offer a reduced amount of pressure drop due to their ability to introduce a low resistance flow passage while still providing the large surface area for heat and mass transfer. In this study, a magnetic stabilization process was developed to fabricate microchannels from the fine ferrite particles. The experimental hydrodynamic performance evaluation of such structures is described in this paper. This unique microchannel fabrication method can significantly improve thermal and hydrodynamic performance, while providing additional flexibility to control the porosity of the packed bed of particles.