Miniature Spacecraft Research Articles

Optical-Propulsion Metastructures.

Pulsed laser micropropulsion (PLMP) offers a promising avenue for miniature space craft, yet conventional propellants face challenges in balancing efficiency and stability. An optical-propulsion metastructure strategy using metal-organic frameworks (MOFs) is presented to generate graphene-metal metastructures (GMM), specifically GMM-(HKUST-1), which significantly enhances PLMP performance. This novel approach leverages the unique interaction between pulsed lasers and the precisely engineered GMMs-comprising optimized metal nanoparticle size, graphene layers, and inter-particle gaps-to boost both propulsion efficiency and stability. Experimental and numerical analyses reveal that GMM-(HKUST-1) achieves aspecific impulse of 1072.94 s, ablation efficiency of 51.22%, and impulse thrust per mass of 105.15 µN µg-1, surpassing traditional propellants. With an average particle size of ≈12 nm and a density of 0.958gcm-3, these metastructures exhibit 99% light absorption efficiency and maintain stability under atmospheric and humid conditions. The graphene nanolayer efficiently absorbs and converts laser energy, while the metal nanostructures enhance light-matter interactions, promoting energy transfer and material stability. These findings suggest that this GMM-based optical-propulsion strategy can revolutionize microspacecraft propulsion and energy systems, offering significant advancements across various domains.

Broadband, High-Reflectivity Dielectric Mirrors at Wafer Scale: Combining Photonic Crystal and Metasurface Architectures for Advanced Lightsails.

Highly ambitious initiatives aspire to propel a miniature spacecraft to a neighboring star within a human generation, leveraging the radiation pressure of lasers for propulsion. One major challenge for this enormous feat is to build a meter-scale, ultralow mass lightsail with broadband reflectivity. In this work, we present the design and fabrication of a lightsail composed of two distinct dielectric layers with photonic crystal/metasurface structure covering a 4" wafer. We achieved broadband reflection of >70% spanning over the full Doppler-shifted laser wavelength range during spacecraft acceleration with a low total mass in the range of a few grams when scaled up to meter size. Furthermore, we find new paths to reliably fabricate these subwavelength structures over macroscopic areas and then systematically characterize their optical performance, confirming their suitability for future lightsail applications. Our innovative device and precise nanofabrication approaches represent a significant leap toward interstellar exploration.

Design of a Low-Cost Air Bearing Testbed for Nano CMG Maneuvers

In this paper, a low-cost, miniature spacecraft attitude control simulator is presented for testing miniature actuators such as Nano Control Moment Gyroscopes (CMGs) for simple maneuvers. The experimental setup is composed by an attitude control system (ACS) that mainly consists of a four-CMG cluster in a pyramid configuration and a custom-made air bearing. The one-degree-of-freedom (DoF) air bearing is fabricated to reproduce the frictionless conditions of a nano-satellite in orbit. The ACS is made exclusively using low-cost commercial-off-the-shelf (COTS) components, whilst the air bearing is made using 3D-printed parts. Both hardware and software implementations are described in detail and the performance of the developed simulator is evaluated by two maneuver experiments. Despite the manufacturing imperfections, the ACS is capable of providing higher angular velocities than previously presented in the literature while following the theoretical or simulation data. The results indicate that it is possible to manufacture a low-cost, miniature actuator such as a CMG, using COTS components to demonstrate the operation of an agile nano-satellite. Any deviations from the theoretical values are addressed and several improvements are discussed to further enhance the performance of the air bearing testing platform.

Designing Spacecraft to Explore Extreme Environments Within the Solar System

In the next few decades, upcoming technological advances will offer unprecedented opportunities to explore the solar system – both with autonomous robots, and through manned missions. Dr Jekan Thanga and the Space and Terrestrial Robotic Exploration (SpaceTREx) Laboratory at University of Arizona are at the forefront of efforts to design miniature spacecraft that will allow us to reach these distant worlds, and navigate their rugged, unfamiliar terrains. In the future, his team’s research could pave the way for the establishment of long-term, off-world human settlements, and the discovery of life in extreme, yet potentially habitable environments.

A brief review of the cubic star on structural design, applications, and future perspective

With the increasing diversification of space missions, the cube star, as a standard module-based miniature spacecraft, has gradually become increasing research interest and development in the field of aviation based on its low cost, high integration, and short development cycle. This paper reviews the design, application, and prospect of cube star, which analyzes the standardized structural design, attitude system, power system, communication measurement, and control design. It is focused on the application areas of cube star in demodulation of satellite signals, space exploration, and discovery technology verification, earth observation, communication interruption, etc. Finally, the development trend of future cube star technology is analyzed.

Parametric Analysis of High-Delta-V CubeSat Missions with a Miniature Ion Thruster

The increasing capabilities of the CubeSat platform have led to growing interest in performing more complex commercial and science missions with these miniature spacecraft. In particular, electric propulsion provides unprecedented mission and enables ambitious but low-cost Earth missions as well as lunar, asteroid, and interplanetary exploration. As a case study, a 6 U (where U represents a “unit”) CubeSat using the Miniature Xenon Ion Thruster was designed for a notional mission with a 2 kg, 1.6 U payload, resulting in a spacecraft wet mass of 11.9 kg and a burn duration of 15 months. This spacecraft is capable of up to for a 0.5 U payload, as well as for a 2 U payload. Parametric analyses with generalized electric thruster properties show that mission performance is sensitive to thruster and total efficiency , with a 10% increase in efficiency resulting in a 16% decrease in burn time. This decrease in burn time is also possible by decreasing , but it incurs mass and payload volume penalties. Parametric studies of neutralizer cathode properties show that neutralizer cathode selection is critical, and that such cathodes should be designed to require low power, low to zero flow rate, and long life for high- missions.

Capabilities for Probing of Upper Atmosphere Density Variations and Seismic-Orbital Effects Using Small-Size Spacecraft

The miniature spacecraft have a high ballistic coefficient, which is advantageous for the resolution of sensing the density of the upper atmosphere. The purpose of this work is to show new features of the "falling spheres method" based on the miniaturization of the Spacecraft. The "falling spheres method" is used to probe variations in the density of the upper atmosphere.A technical solution for diagnostics of orbital sections with abnormal changes in the speed and acceleration of spacecraft equipped with onboard navigation receivers and micro-accelerometers is considered.The technical result of the proposed development is the efficiency and cost – effectiveness of sounding variations in the density of the upper atmosphere, seismic-orbital effects-variations in the density of the atmosphere over earthquake-regions and the seismic hazard.

Effect of heat transfer and geometry on micro-thruster performance

Coupled Navier-Stokes and Direct Simulation Monte Carlo (NS-DSMC) simulations of gas flow in micro-nozzles for various wall thermal conditions and geometrical aspects are presented. Micro-thrusters employed in miniature spacecraft and microsatellites experience substantial changes in wall thermal conditions. This can influence the internal boundary layer development and the exit plume structure of a micro-nozzle. These changes in flow physics differ with the nozzle divergence angle and the proximity of a similar nozzle in the cluster. Continuum solvers often fail to analyze the micro-nozzles operating in vacuum conditions as the flow in micro-nozzles experiences continuum, transitional, and rarefied regimes. Coupled NS-DSMC solver is an effective alternative that can simulate the non-equilibrium effects in a micro-nozzle flow field. A steady solution of the entire flow field has been obtained using a non-linear Harten-Lax-van Leer-Contact (HLLC) scheme based finite volume solver with a higher order slip boundary condition. Continuum breakdown regions are identified based on the gradient-length local (GLL) Knudsen number condition. This initial steady solution on the flow transition boundary is implemented in the DSMC solver as a Dirichlet boundary condition. The present computations are useful in calibrating micro-propulsion controllers to adapt to the substantial momentum changes associated with various nozzle wall thermal conditions and the proximity of similar nozzles in the cluster.

Ion emission from solid electrolyte CsAg4Br2.68I2.32 film deposited on Ag-tip: Characteristics and applications

We have developed a solid electrolyte ion source (SEIS) with CsAg4Br2.68I2.32 film deposited on a silver tip. In the paper, Ag+ ion emission was significantly enhanced and the ion current of 1.6 μA was obtained at 168 °C temperature and 20 kV accelerating voltage. I-T and I-U characteristics were well described by the field evaporation (FEV) model, and the surface potential barrier was estimated to be 0.19 eV. Experimental investigations of the Ag+ ion emission mechanisms revealed that the solid electrolyte film plays an important role of ion-transport system, and the emitted Ag+ ions were compensated by the ions diffusing from the silver reservoir (Ag-tip). The developed SEIS was exploited for the synthesis of Ag nanoparticles on Si surface. The average size of these nanoparticles was estimated 15.5 ± 0.3 nm, and the projected range Rp of the low-energy high-dose Ag+ ions implanted Si sample was found to be less than 5 nm using TOF-SIMS depth profiling. The future application of SEISs in ion propulsion systems of miniature spacecraft with limited on-board payloads was discussed, and the thrust was estimated within μN range.

Fault-tolerant attitude control of miniature satellites using reaction wheels

An adaptive fault-tolerant nonlinear control scheme is proposed for precise 3-axis attitude tracking of miniature spacecraft in the presence of control input saturation, model uncertainties, external disturbances, and reaction wheel faults. Two configurations of reaction wheel assembly are examined in this paper, (A1) Traditional four wheel setup where three reaction wheels are in orthogonal configuration along with one oblique wheel; and (A2) Four wheels in a pyramid configuration. Multiplicative reaction wheel faults are considered along with complete failure of one wheel (A1) and two wheels (A2). The proposed control algorithm does not require an explicit fault detection and isolation mechanism and therefore failure time instants, patterns, and values of actuator failures remain unknown to the designer. The stability conditions for robustness against model uncertainties and external disturbances are derived using Lyapunov stability theory to establish the regions of asymptotic stabilization. The benefits of the proposed control methodology are analytically authenticated and also validated using hardware-in-the-loop simulations. The experimental results clearly establish the robustness of the proposed autonomous control algorithm for precise attitude tracking in the event of reaction wheel faults and failures.

Instruments for spacecraft orientation with respect to the Sun based on active-pixel detector arrays

We describe two instruments for orientation with respect to the Sun based on active-pixel detector arrays: the 347K static high-precision instrument for orientation with respect to the Sun and the MSD miniature Sun sensor developed for small and miniature spacecraft. We describe the basic characteristics and functional operating modes of these instruments, as well as the results from ground-based and flight tests of the 347K instrument, which confirm that two coordinates of orientation can be determined within a total error of 1′.

The Little Rocket Engine That Could

This paper highlights advancements of a research team in the field of miniature spacecrafts and development and advantages of CubeStats. CubeSats are space age hitchhikers, that is, miniature spacecraft that fly into orbit aboard rockets whose primary payloads are full-size satellites. Paulo Lozano and his team at MIT’s Space Propulsion Lab have developed a unique kind of rocket engine for these microsatellites. The trick to building a successful ion electrospray propulsion system is to increase thrust density by jamming together as many emitters as possible. Electrospray engines also differ greatly from another form of ion propulsion, plasma ion, which also eschews chemical combustion for the efficiency of the electron. A big advantage, when asking for permission to hitchhike a ride into orbit, is that ion electrospray propulsion engines cannot explode and destroy a rocket’s primary payload. A second advantage of ion engines is their modularity and, consequently, scalability.

Dressed to kill: 50 years of the spacewalk

The ISS has the equipment necessary to support controlled decompression. Future human missions to the moon or Mars, using smaller spacecraft, may have to dispense with it. Suits and ships alike will have to operate at the same pressure. The problem of ballooning will be overcome by a suit design that, at first glance, seems a retrograde development. NASA's latest prototype, known as the Z-suit, looks like an armoured robot from 1950s science fiction. Recent publicity photos show an astronaut wearing a white Z-suit uncannily like Buzz Lightyear's, but the outer fabric is a superficial layer of micrometeorite protection. Inside, there's a shell of hard composites tough enough to withstand contact with jagged rocks and abrasive surface dust on the moon and Mars. Whenever an astronaut on a planetary mission climbs out of a suit, there will be a danger of inhaling potentially toxic dust particles from outside the lander or habitat. The simple solution is to never expose astronauts to the suit's mucky exterior. Actually, this is easier than it sounds. The rear of the Z-suit features an airlock. When not in use, the entire thing is stored on the outside of a rover, docked to a 'suit portal'. Essentially a Z-suit is like a miniature spacecraft in its own right. Astronauts can swap at will between the suit and the airlock areas of a habitat or rover without waiting for the pressures to equalise. Ballooning is eliminated by pushing the rigidity of the suit to the logical extreme, until its fabric has no flexibility at all, except in the gloves and at the limb joints.

Aviation Flight Attitude Control Technology

This paper presents a range of two miniature spacecraft attitude Fuzzy Neural Network Sliding adaptive controller, using a weighting factor to combine indirect and direct fuzzy neural network controller fuzzy neural network controller. Interval two free parameters of fuzzy neural network adaptive sliding mode controller via output feedback control law and adaptive law be adjusted online. Simulation results show that after joining 10db Gaussian white noise, and in order to reduce the impact of external interference and noise training data, a controller with respect to the range of large amount of control type II generated by the controller. Overall adaptive scheme guarantees the global stability of the closed-loop system, all signals involved are bounded in some way, and also showed a high level of tracking performance.

Enhancing ground communication of distributed space systems

The functionality of a distributed system can be significantly enhanced by exploring non-traditional approaches that leverage on inherent aspects of distributed systems in space. Till now, the benefit of distributed systems in space has been limited to enhancing coverage, multipoint sensing, creating virtual baselines (e.g. interferometry) or to enhance redundancy. The list of benefits can be further expanded by understanding the nature of distributed systems and by productively incorporating it into mission and spacecraft design. For example, prior knowledge of the spatial evolution of such systems can lead to innovative communication architectures for these distributed systems. In this paper, different communication scenarios are investigated that can enhance the communication link between the distributed system and ground.The increasing trend towards highly miniaturized spacecraft (nano- to femto-satellites) and proposals to launch hundreds or even thousands of them in massively distributed space missions have expanded the interest in distributed systems with miniature spacecraft. It is important to understand how and which, functionalities and systems, scale with size and number. Scalable systems are defined and addressed at a basic level and the utility of scaling rules and trends in identifying optimal configurations of distributed systems is explored.In this paper we focus on the communication capability and identify methods to enhance the communication link between a distributed space segment, consisting of a number of simplistic, resource limited femto-satellites, and earth. As an example, the concept of forming a dynamic phased array in space with the elements of a distributed space system in low-earth orbit is investigated. At the ground receiver, the signals from different satellites forming the array should not differ in phase by more than one-third the transmission wavelength, to ensure constructive superposition. Realizing such a phased array places strict accuracy requirements on time synchronization and knowledge of relative separation between the satellites with respect to the ground receiver. These constraints are derived and discussed.

Attitude control of miniature spacecraft under the gravitational effect using a hub-bimorph mechanism

This paper presents the attitude control of miniature spacecraft using a hub-bimorph mechanism, which is simplified from a so-called pseudowheel. A nonlinear mathematical model for the spacecraft coupled by the hub-bimorph mechanism is developed. The proposed model includes not only the inverse piezoelectric effect of the mechanism but also the gravitational effect. This paper also presents three controller designs – the pole assignment method, the linear quadratic regulator, and the time-delay control – which demonstrate the feasibility of spacecraft attitude control using the hub-bimorph mechanism.

Open-loop and closed-loop attitude dynamics and controls of miniature spacecraft using pseudowheels

This paper presents open-loop and closed-loop attitude control strategies of miniature spacecraft using pseudowheels, which are composed of multiple bimorphs and are mounted on the three principal axes of the spacecraft. Due to the conservation of angular momentum, the vibrations of the bimorph excited by applied voltages can rotate the spacecraft. By applying a sequence of rotations along the three axes, the attitude of the spacecraft can be changed. The modeling of the spacecraft–pseudowheel system includes the inverse piezoelectric effect and the gravity gradient torques. Since one cannot guarantee that a solution will be found for every rotation sequence, this paper proposes an approach to solve this problem. In addition, the voltages applied to the bimorphs are reduced to meet the specifications of the voltage amplifiers. Furthermore, a closed-loop attitude control strategy is presented to reduce the applied voltages and to compensate the attitude error caused by the gravity gradient torques.

Chips in space

This paper discusses about how satellites the size of chips could revolutionize the way we explore space. It mainly deals with exploring the potential of miniature spacecraft.

Open-loop optimal attitude control of miniature spacecraft using MEMS actuators

A novel attitude control method based on micro-electro-mechanical systems (MEMS) actuators, developed by Li et al. Each actuator (called pseudowheel) comprises four small beams of electro-thermal materials. If these beams undergo the transverse deformation in a clockwise rotation, the spacecraft rotates in counterclockwise direction in order to conserve the system angular momentum. However, when the actuator is off, the beams come to their undeformed configurations because of their elastic properties. This problem can be overcome by employing a sequence of large rotations caused by deflecting actuators about two or three orthogonal axes to produce a net attitude change. The kinematics of all rotation sequences is considered and then the rotating angles of MEMS actuators are derived by solving a set of nonlinear equations in terms of attitude angles of the spacecraft and rotating angles of the MEMS actuators. This paper presents further researches based on the work of Li et al. Such as study of rotation sequences, kinematics analysis of spacecraft, and simulation of attitude motion. Assuming the conservation of system angular momentum and employing inverse kinematics, the time response of attitude motion of the spacecraft is simulated. This approach not only just searches a possible solution based on an open-loop control strategy, but also determines a set of optimal rotating rates of MEMS actuators, which can produce a minimum kinetic energy required for attitude control. The proposed approach may be particularly useful for the attitude control of miniature spacecraft.

Inverse Kinematics of an Untethered Rigid Body Undergoing a Sequence of Forward and Reverse Rotations

A sequence of rotations considered in this paper is a series of rotations of an untethered rigid body about its body-fixed axes such that the rotation about each axis is fully reversed at the end of the sequence. Due to the noncommutative property of finite rigid body rotations, such a sequence can effect nonzero changes in the orientation of the rigid body even though the net rotation about each axis is zero. These sequences are useful for attitude maneuvers of miniature spacecraft that use elastic deformation-based microactuators, or of other airborne or neutrally buoyant underwater vehicles. This paper considers the inverse kinematics problem of determining the angles in a given sequence to achieve a desired change in the orientation. Two types of problems are addressed. For the first problem, where four-rotation sequences are used, an analytical solution is presented and it is shown that a pointing vector attached to the rigid-body can be arbitrarily oriented. In the second problem, six-rotation sequences are used to control all three of the orientation freedoms of the rigid body. Some of the six-rotation sequences can provide any change in orientation while others are limited in their capabilities. A general numerical solution for all types, and a closed-form analytical solution for one type are presented along with the numerical examples and graphical visualization.