- Applications of the Ensemble Kalman Update to Electrospray Thrusters
- Electrostatic Actuation on Atmosphere-less Planetary Bodies
- Proximity Operations with Electrospray Thrusters
- Stage-based Electrospray Propulsion
- Motion Planning for Legged Rovers
- Fiber-Film Probes for Characterization of Cavitation Dynamics in a Rocket Engine Turbopump Inducer
Applications of the Ensemble Kalman Update to Electrospray Thrusters
Electrostatic Actuation on Atmosphere-less Planetary Bodies
Further details can be found in this paper.
Proximity Operations with Electrospray Thrusters
Stage-based Electrospray Propulsion
The standardization of small spacecraft through CubeSats has allowed for more affordable space exploration. This progress in affordability has been limited to Earth orbit due in part to the lack of high-ΔV propulsion systems that are compatible with the small form factor. The Ion Electrospray Propulsion System developed at the Space Propulsion Laboratory at the Massachusetts Institute of Technology is a promising technology foundation for a compact, high-ΔV propulsion system. However, the ΔV output of the propulsion system is limited by the lifetime of individual electrospray thrusters. This research presents the design and analysis of a stage-based concept for the Ion Electrospray Propulsion System where the propulsion system is composed of a series of electrospray thruster arrays, analogous to launch vehicle staging. The stage-based propulsion system bypasses the lifetime limit of individual electrospray thrusters in order to increase the lifetime of the entire propulsion system. In effect, propulsion capabilities for small spacecraft can be advanced without the need for technological developments. With the current performance metrics of the Ion Electrospray Propulsion System, deep-space missions with an spacecraft form factor as small as a 3U CubeSat are feasible with current propulsion technology.
Publications produced out of this work include:
- Master's thesis encompassing the design and analysis of an electrospray thruster staging system [Source]
- Development of the physical mechanisms required for staging [Source]
- Laboratory demonstration of an electrospray thruster staging system in vacuum [Source]
- Analytical methodologies for the analysis of staging systems [Source]
- Systems-level analysis of the feasibility of staging systems for deep-space CubeSat missions [Source]
- Analytical guidance during circular orbit transfers for spacecraft using staging systems [Source]
- Application of staging for propulsion system redundancy during asteroid detumbling [Source]
Motion Planning for Legged Rovers
Planetary surface robotic explorers currently implement limited amounts of autonomy, often relying on rigorously-developed offline plans. If deviation occurs, long communication delays often result in rover downtime and subsequent lost time for scientific exploration. Onboard robotic motion planning that is fast and accounts for obstacles and robot kinematics is one key piece of the autonomy pipeline required to bring more meaningful autonomy to planetary exploration. Current approaches normally rely on sampling-based planning methods like the rapidly exploring random tree (RRT) algorithm which has had considerable success for kinematic motion planning. However, global computation over the entire state space for high-dimensional systems in cluttered environments, like legged robots on a planetary surface, can be complex and too slow for practical use. Furthermore, complete environment information is often not available a priori. This work proposes a real-time combined global-local planner for a legged robot in a partially unobserved, cluttered environment. Large obstacles known beforehand (e.g., orbital imagery) are accounted for using a fast global planner on a low-dimensional model. Unknown small obstacles which restrict foot placements are dealt with as they are observed using a slower but real-time local planner, obeying the complex legged robot kinematics. This approach, called SweepingRRT, makes use of observed information locally as it becomes known, while providing the fast global replanning that may be necessitated by new obstacle observations. The planning algorithm is demonstrated in simulation for a standard four-legged, eight-jointed robot in some demonstrative obstacle environments consisting of large (known) and small (unknown) obstacles using a limited sensor range.
Further details can be found in this paper.
Fiber-Film Probes for Characterization of Cavitation Dynamics in a Rocket Engine Turbopump Inducer
One of the main challenges in characterising the dynamics of a rocket engine turbopump inducer is the measurement of mass flow fluctuations during forced response testing. Historically, such measurements have been taken through a spatially averaged mass flow measurement far upstream of the inducer with an electromagnetic flow meter or laser Doppler velocimetry. Fiber-film probes are proposed to take local, unsteady velocity measurements in a rocket engine turbopump inducer test setup. This work shows that a fiber-film probe is capable of taking local, unsteady velocity measurements in an inducer inlet flow during cavitation and has sufficient signal-to-noise ratio to measure velocity profiles in the presence of back flow. Experiments were run the Aerospace Cor- poration’s inducer test facility with the MIT inducer in order to assess a fiber-film probe’s performance. This work takes the first steps towards performing forced response inducer experiments with local, unsteady velocity measurements. This work was conducted as part of the SuperUROP program at MIT from Fall 2016 - Spring 2017.
Further details can be found in the final paper.