The SPARC Toroidal Field Model Coil Program

The SPARC Toroidal Field Model Coil (TFMC) Program was a three-year effort between 2018 and 2021 that developed novel Rare Earth Yttrium Barium Copper Oxide (REBCO) superconductor technologies and then successfully utilized these technologies to design, build, and test a first-in-class, high-field (~20 T), representative-scale (~3 m) superconducting toroidal field coil. With the principal objective of demonstrating mature, large-scale, REBCO magnets, the project was executed jointly by the MIT Plasma Science and Fusion Center (PSFC) and Commonwealth Fusion Systems (CFS). The TFMC achieved its programmatic goal of experimentally demonstrating a large-scale high-field REBCO magnet, achieving 20.1 T peak field-on-conductor with 40.5 kA of terminal current, 815 kN/m of Lorentz loading on the REBCO stacks, and almost 1 GPa of mechanical stress accommodated by the structural case. Fifteen internal demountable pancake-to-pancake joints operated in the 0.5 to 2.0 nOhm range at 20 K and in magnetic fields up to 12 T. The DC and AC electromagnetic performance of the magnet, predicted by new advances in high-fidelity computational models, was confirmed in two test campaigns while the massively parallel, single-pass, pressure-vessel style coolant scheme capable of large heat removal was validated. The REBCO current lead and feeder system was experimentally qualified up to 50 kA, and the crycooler based cryogenic system provided 600 W of cooling power at 20 K with mass flow rates up to 70 g/s at a maximum design pressure of 20 bar-a for the test campaigns. Finally, the feasibility of using passive, self-protection against a quench in a fusion-scale NI TF coil was experimentally assessed with an intentional open-circuit quench at 31.5 kA terminal current.Comment: 17 pages 9 figures, overview paper and the first of a six-part series of papers covering the TFMC Progra

Development of low-thrust solid rocket motors for small, fast aircraft propulsion

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, May, 2020Cataloged from the official PDF of thesis.Includes bibliographical references (pages 281-289).Small, uncrewed aerial vehicles (UAVs) are expanding the capabilities of aircraft systems. However, a gap exists in the size and capability of aircraft: no small aircraft are capable of sustained fast flight. A small, fast aircraft requires a propulsion system which is both miniature and high-power, requirements which current UAV propulsion technologies do not meet. Solid propellant rocket motors could be used, but must be re-engineered to operate at much lower thrust and for much longer burn times than conventional small solid rocket motors. This imposes unique demands on the motor and propellant. This work investigates technological challenges of small, low-thrust solid rocket motors: slow-burn solid propellants, motors which have low thrust relative to their size (and thus have low chamber pressure), thermal protection for the motor case, and small nozzles which can withstand long burn times.Slow-burn propellants were developed using ammonium perchlorate oxidizer and the burn rate suppressant oxamide. By varying the amount of oxamide (from 0-20%), burn rates from 4mms⁻¹ to 1mms⁻¹ (at 1MPa) were achieved. Using these propellants, a low-thrust motor successfully operated at a (thrust / burn area) ratio 10 times less than that of typical solid rocket motors. This motor can provide 5-10N of thrust for 1-3 minutes. An ablative thermal protection liner was tested in these firings. Despite the long burn time, only a few millimeters of ablative are needed. A new ceramic-insulated nozzle was demonstrated on this motor. The nozzle has a small throat diameter (only a few millimeters) and can operate in thermal steady-state. Models were developed for the propellant burn rate, motor design, heat transfer within the motor and nozzle, and for thermal stresses in the nozzle insulation.This work shows that small, low-thrust solid motors are feasible, by demonstrating these key technologies in a prototype motor. Further, the experimental results and models will enable engineers to design and predict the performance of solid rocket motors for small, fast aircraft. By providing insight into the physics of these motors, this thesis may help to enable a new option for aircraft propulsion.by Matthew T. Vernacchia.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Aeronautics and Astronautic

Development, modeling and testing of a slow-burning solid rocket propulsion system

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.Cataloged from PDF version of thesis.Includes bibliographical references (pages 163-168).Small, unmanned aerial vehicles (UAVs) are expanding the capabilities of aircraft systems. However, a gap exists in the size and capability of aircraft: no aircraft smaller than 10 kilograms are capable of flight faster than 100 meters per second. A small, fast aircraft requires a propulsion system which is both miniature and high-power, requirements which current UAV propulsion technologies do not meet. To meet this need, a slow-burning solid rocket motor has been developed. Such motors require slow-burning solid propellants with tailorable burn rate. This thesis reports experimental results and combustion theory for a slow-burning solid propellant. It also describes a rocket motor designed to use this propellant, and the manufacturing process used to produce it. This propellant burns slowly enough for the low-thrust, long-endurance needs of UAV propulsion. Its burn rate can be predictably tailored by addition of the burn rate suppressant oxamide. Further, this thesis presents a concept for a small, fast aircraft designed around this novel propulsion technology. The motor integrates elegantly into the aircraft's structure, and compact thermal protection system insulates other vehicle systems from the heat of combustion. These results demonstrate the feasibility slow-burning rocket propulsion systems, and their application to small aircraft. It should be possible for small, rocket-propelled UAVs to sustain powered, transonic flight for several minutes. With this technology, kilogram-scale UAVs could be able to quickly deploy over tens of kilometers, and fly joint missions alongside manned fighter jets.by Matthew T. Vernacchia.S.M

Low-Thrust Solid Rocket Motors for Small, Fast Aircraft Propulsion: Design and Development

Small, low-thrust, long-burn-time solid propellant rocket motors could provide propulsion for a new class of kilogram-scale, transonic, uncrewed aerial vehicles (UAVs). This paper investigates technological challenges of small, low-thrust solid rocket motors: slow-burn solid propellants, motors that have low thrust relative to their size (and thus have low chamber pressure), thermal protection for the motor case, and small nozzles that can withstand long burn times. Slow-burn propellants were developed using ammonium perchlorate and 0–20% oxamide (burn-rate suppressant), with burn rates of 1–4  mm⋅s−1 at 1 MPa. Using these propellants, a low-thrust motor successfully operated at a thrust/burn area ratio 10 times less than that of typical solid rocket motors. This kilogram-scale motor can provide 5–10 N of thrust for 1–3 min. An ablative thermal protection liner was tested in these firings, and a new ceramic-insulated nozzle was demonstrated. This paper shows that small, low-thrust solid motors are feasible and presents a baseline design for the integration of such a motor into a small UAV.Department of Defense (DoD)MIT Lincoln Laboratories, BAE Systems, Inc

Slow-Burn Ammonium Perchlorate Propellants with Oxamide: Burn Rate Model, Testing, and Applications

Low-thrust long-burn-time solid rocket motors may be useful as propulsion for small, fast, uncrewed aerial vehicles. These motors require a slow-burning propellant that can operate at unusually low chamber pressures (0.3–2 MPa). Slow-burn propellants were developed using ammonium perchlorate oxidizer and the burn rate suppressant oxamide. By varying the amount of oxamide (from 0 to 20%), burn rates from 4 to 1  mm⋅s−1 (at 1 MPa) were achieved. The adjustable burn rate allows a set of similar propellants to serve many aircraft and mission concepts. This work presents burn rate measurements (from both a strand burner and a research motor), minimum burn pressure measurements, and combustion chemical equilibrium simulations. A novel model of oxamide’s effect on burn rate is also presented, and it fits well to the experimental data. Finally, these propellant data and models are applied to select the propellant and chamber pressure for an example low-thrust solid rocket motor

Gesture-Based Robot Control with Variable Autonomy from the JPL Biosleeve

This paper presents a new gesture-based human interface for natural robot control. Detailed activity of the user's hand and arm is acquired via a novel device, called the BioSleeve, which packages dry-contact surface electromyography (EMG) and an inertial measurement unit (IMU) into a sleeve worn on the forearm. The BioSleeve's accompanying algorithms can reliably decode as many as sixteen discrete hand gestures and estimate the continuous orientation of the forearm. These gestures and positions are mapped to robot commands that, to varying degrees, integrate with the robot's perception of its environment and its ability to complete tasks autonomously. This flexible approach enables, for example, supervisory point-to-goal commands, virtual joystick for guarded teleoperation, and high degree of freedom mimicked manipulation, all from a single device. The BioSleeve is meant for portable field use; unlike other gesture recognition systems, use of the BioSleeve for robot control is invariant to lighting conditions, occlusions, and the human-robot spatial relationship and does not encumber the user's hands. The BioSleeve control approach has been implemented on three robot types, and we present proof-of-principle demonstrations with mobile ground robots, manipulation robots, and prosthetic hands