The incorporation of spent bleaching clay (SBC) into the CaL process has been proposed to reduce the system cost, whereby fuels and/or heat from different SBC regeneration could be used as a partial energy source for the calciner; the regenerated SBC residues are used with lime powders to synthesize pellets. In this paper, the prepared sorbents doped with regenerated SBC and cement were tested in a bubbling fluidized bed (BFB) to further examine the cyclic CO2 capture capacity and attrition properties. The results revealed that the cyclic CO2 capture capacity of pellets modified by pyrolyzed SBC and/or cement displayed significantly better performance than limestone, consistent with the thermogravimetric analyzer (TGA) results. This is due to the improvement of pore structure and better sintering resistance produced by adding inert phases to the sorbent. The elutriation rates of the composites prepared with pyrolyzed SBC and/or cement were consistently lower than for crushed limestone. Scanning electron microscopy (SEM) images indicated that the pellets possessed higher sphericity than limestone particles, reducing surface abrasion. Limestone exhibited a high attrition rate (diameter reduction rate) of 10.7 μm/cycle, which could be effectively eliminated by adding regenerated SBC and/or cement. "L-5PC-10CA" (85% lime/5% pyrolyzed SBC/10% cement) showed a higher attrition resistance, exhibiting the lowest attrition rate of 7.9 μm/cycle. Based on the analysis

Fast development of CubeSat technology now enables the first interplanetary missions. The potential application of CubeSats to flyby near-Earth asteroids is explored in this paper in consideration of CubeSats' limited propulsive capabilities and systems constraints. Low-energy asteroid flyby trajectories are designed assuming a CubeSat is initially parked around to the Sun-Earth Lagrange points. High-impulse and low-thrust trajectories with realistic thrusting models are computed first in the Circular Restricted Three-Body Problem (CR3BP), and then in a high-fidelity ephemeris model. Analysis in the ephemeris model is used to confirm that trajectories computed in the CR3BP model also exist in a more realistic dynamical model, and to verify the validity of the results obtained in CR3BP analysis. A catalogue of asteroid flyby opportunities between years 2019 and 2030 is provided, with 80 m/s of available ΔV and departure from halo orbits around the first and second Sun-Earth Lagrange points (of similar size to those typically used by scientific missions). Results show that the CR3BP model can serve as an effective tool to identify reachable asteroids and can provide an initial estimation of the ΔV cost in the ephemeris model (with ±15 m/s accuracy). An impulsive maneuver model can also provide an accurate estimation of the ΔV requirement for a CubeSat equipped with a high-impulse thruster (with 4 m/s accuracy), even if its thrust magnitude is small and requires duty cycling; low-thrust ΔV requirements, however, may differ significantly from the impulsive results (±15 m/s).

Recent advancements in CubeSat technology unfold new mission ideas and the opportunity to lower the cost of space exploration. Ground operations costs for interplanetary CubeSats, however, still represent a challenge towards low-cost CubeSat missions: hence, certain levels of autonomy are desirable. The feasibility of autonomous asteroid flyby missions using CubeSats is assessed here, and an effective strategy for autonomous operations is proposed. The navigation strategy is composed of observations of the Sun, visible planets, and the target asteroid, whereas the guidance strategy is composed of two optimally-timed trajectory correction maneuvers. A Monte Carlo analysis is performed to understand the flyby accuracies that can be achieved by autonomous CubeSats, in consideration of errors and uncertainties in: (a) departure conditions, (b) propulsive maneuvers, (c) observations, and (d) asteroid ephemerides. Flyby accuracies better than ±100 km (3σ) are found possible, and main limiting factors to autonomous missions are identified, namely: (a) on-board asteroid visibility time (Vlim≥11), (b) ΔV for correction maneuvers (>15 m/s), (c) asteroid ephemeris uncertainty (<1000 km), and (d) short duration of transfer to asteroid. Ultimately, this study assesses the readiness level of current CubeSat technology to autonomously flyby near-Earth asteroids, in consideration of realistic system specifications, errors and uncertainties.

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