Independent deep-space CubeSat missions require efficient propulsion systems capable of delivering several km/s of ∆V. The ion Electrospray Propulsion System under development at MIT's Space Propulsion Laboratory is a high ∆V propulsion system that is a promising technology for propulsion of independent deep-space CubeSat missions due to its mechanical simplicity and small form factor. However, current electrospray thrusters have demonstrated lifetimes up to an order of magnitude lower than the required firing time for a mission to a near-Earth asteroid starting from geostationary orbit. A stage-based concept is proposed where the propulsion system consists of a series of electrospray thruster arrays. When a set of thrusters reaches its lifetime limit, it is ejected from the spacecraft exposing new thrusters thereby increasing the overall lifetime of the propulsion system. Such a staging strategy is usually not practical for in-space thrusters. However, the compactness of micro-fabricated electrospray thrusters means that their contribution to the overall spacecraft mass and volume is small relative to other subsystems. Mechanisms required for this stage-based approach are proposed and demonstrated in a vacuum environment. In addition, missions to several near-Earth asteroids with orbital elements similar to those of Earth are analyzed with a particular focus on the escape trajectory. With a stage-based approach, independent deep-space CubeSat missions become feasible from a propulsion standpoint.
Independent deep-space exploration with CubeSats, where the spacecraft independently propels itself from Earth orbit to deep-space, is currently not possible due to the lack of high-∆V propulsion systems compatible with the small form factor. The ion Electrospray Propulsion System (iEPS) under development at the Massachusetts Institute of Technology's Space Propulsion Laboratory is a promising technology due to its inherently small size and high efficiency. However, current electrospray thrusters have demonstrated lifetimes (500 hours) below the required firing time for an electrospray-thrusterpropelled CubeSat to escape from Earth starting from geostationary orbit (8000 hours). To bypass this lifetime limitation, a stage-based approach, analogous to launch vehicle staging, is proposed where the propulsion system consists of a series of electrospray thruster arrays and fuel tanks. As each array reaches its lifetime limit, the thrusters and fuel tanks are ejected from the spacecraft exposing a new array to continue the mission. This work addresses the technical feasibility of a spacecraft with a stage-based electrospray propulsion system for a mission from geostationary orbit to near-Earth asteroid 2010 UE51 through a NASA Jet Propulsion Laboratory Team Xc concurrent design center study. Specific goals of the study were to analyze availability of CubeSat power systems that could support the propulsion system and any other avionics as well as requirements for attitude control and communication between the spacecraft and Earth. Two bounding cases, each defined by the maturity of the iEPS thrusters, were considered. The first case used the current demonstrated performance metrics of iEPS on a 12U CubeSat bus while the second case considered expected near-term increases in iEPS performance metrics on a 6U CubeSat bus. A high-level overview of the main subsystems of the CubeSat design options is presented, with a particular focus on the propulsion, power, attitude control, and communication systems, as they are the primary drivers for enabling the stagebased iEPS CubeSat architecture.
Ionic-liquid ion sources produce beams of charged particles through evaporation and acceleration of ions and charged droplets from the surface of an ionic liquid. The composition of the emitted beam can impact the performance of ion sources for various applications such as focused beams for microfabrication and space propulsion. Numerical inference is considered for quantification of the beam composition of an ionic-liquid ion source through determining the current fraction of different species along with providing uncertainty in inferred values. An analysis of previously presented data demonstrates the ability to quantify the presence of ion clusters, including the distinct presence of heavy ion clusters such as heptamers. Quantification of beam composition will be an important technique for quantitative comparison of different time-of-flight data.
Advances in propulsion systems are key to enabling independent deep-space CubeSat missions. Currently available electric propulsion technologies require relatively high power and thereby heavy power generation systems, severely limiting their utility for missions going away from the Sun. The ionic-liquid electrospray is known to have high power efficiency but a relatively short lifetime in its present state, limiting the total impulse available in such systems. This lifetime limit can be overcome by using several stages of thrusters, which are used in sequence to multiply the total system lifetime. In this paper, we present the design details and laboratory testing results for a staging system that is compatible with the CubeSat standard. This system will later be demonstrated in space on the STEP-1 satellite, which could enable an exciting new era of accessible CubeSat exploration around the solar system. Nomenclature= Effective exhaust velocity of propulsion system, m/s = Hold-down wire diameter, m = Elastic (Young's) modulus, Pa = Stiffness (spring constant), N/m = Hold-down wire length, m 0 = Spacecraft initial wet mass, kg dry = Propulsion system dry mass, kg pay = Spacecraft payload mass, kg P = Electrical power of propulsion system, W = Specific power of electricity generation, W/kg Δ = Velocity increment from propulsion, m/s
This paper presents an analytical library for maneuvering of an underactuated spacecraft around a central target with application to remote inspection. Free-flying small spacecraft are an attractive option for in situ remote inspection but require maneuvering strategies that are computationally simple, such that they can be implemented on a small spacecraft computer, while still allowing for constraints like plume impingement and underactuation to be included. An analytical maneuver library provides a suboptimal solution but can be computed without the need for numerical optimization. In addition, the low fuel cost of maneuvers means that the degree of sub-optimality of the analytical maneuvers is marginal. To develop the library, forced circular motion is used in order to place the spacecraft in a controllable state such that external disturbances can be rejected. From there, maneuvers can be designed in order to manipulate the circular motion and accomplish maneuvers such as joining the circular motion from rest or changing the circle's radius. Conditions under which plume impingement is guaranteed to be avoided are developed and applications of the maneuver library to point-to-point maneuvering and landing on/docking to a rotating target are shown. I. IntroductionRemote inspection of spacecraft allows for an assessment of the condition of the vehicle's exterior and can be conducted with ground-based instruments or in proximity to the spacecraft. While not
In this work, we present coordinated molecular dynamics, ion cluster acceleration, and retarding potential analysis simulations to determine cluster fragmentation behavior in a realistic emitter geometry for electrosprays operating in the pure ionic regime. Molecular dynamics simulations are used to determine the fragmentation rates of ionic liquid clusters as a function of internal energy, electric field strength, and cluster size. A simplified model of electrospray cluster acceleration is developed from previous electrohydrodynamic emission models and used to simulate retarding potential analysis curves. Fragmentation rates and beam composition are inferred for experimental data based on the molecular dynamics and cluster acceleration simulations. We find that for these experimental data, temperatures of EMI-BF4 dimers likely range between 590 and 687 K while trimer temperatures are larger between 989 and 1092 K. The percentage of monomers, dimers, and trimers in the beam is approximately 45%, 30%–43%, and 13%–25%, respectively. Both ionic liquid cluster temperatures and beam composition agree with previous analysis of this experimental work, supporting the use of coordinated molecular dynamics and retarding potential analysis as a method of inferring electrospray beam parameters. Insights gained from this simulation process are discussed in the context of currently unexplained electrospray emitter behavior and experimental results including the presence of tetramers and trimers in the beam and fragmentation rates in high electric field regions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.