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.

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