Direct Fusion Drive: Enabling Rapid Deep Space Propulsion. Presented by: Stephanie Thomas. DIRECT FUSION DRIVE. FISO Telecon 05-29-19. Team Members: - Stephanie Thomas, Michael Paluszek, Charles Swanson (Princeton Satellite Systems, Plainsboro, NJ) - Dr. Samuel Cohen (Princeton Plasma Physics Lab, Plainsboro, NJ) This material is based upon work supported by NASA under award No. NNX16AK28G and 80NSSC18K0040. PFRC: Princeton Field-Reversed Configuration - Compact toroid configuration - RF heating - FRC 'in a mirror' - SOL flow removes fusion exhaust DFD: Direct Fusion Drive - PFRC with an open end - SOL flow rate adjusted to produce desired thrust and Isp - 'Thrust augmentation' - Power AND Propulsion in one device PFRC will produce 1-10 MWe per mini-van size reactor, with almost no radiation. Applications: - Civilian: Distributed and remote power (e.g., villages in Alaska); Mobile and emergency power (hurricane damage relief, e.g., Puerto Rico); Modular power satellites; Low capital cost power plants. - NASA and Space: Deep space robotic missions; Lunar/Mars settlements; Asteroid/comet intervention; Space platform power; High power communications; 3He mining & transport; 550 AU observatory. - DoD Terrestrial and DoD Space: The electric battlefield; Small naval combatants; Forward power; Fusion powered drones for boost phase missile defense. - FRC: Field-Reversed Configuration - Enabled by new magnetic plasma heating method (Steady-state operation) - Simple linear array of magnetic coils (PFRC-2 in operation at PPPL) - Small size permits clean operation (ultra low radioactivity) - Easily direct flow for rocket engine mode: Propellant is introduced into the scrape-off layer (SOL), absorbs energy from fusion products, and accelerates through a nozzle coil. - MNX: DOE 1998-2015 - PFRC-1: DOE FES 2002-2009 - PFRC-2: DOE FES 2010-2016 - NIAC NASA: 2016-2019 - STTRs NASA: 2017-2020 - ARPA-E OPEN: 2019-2020 With a 1-2 MW fusion engine and a 10,000 kg mission: - 1 AU: ~1 year - 5 AU: ~2 years - 10 AU: ~3 years - 20 AU: ~4 years - 30-40 AU: ~5 years Advanced Propulsion Big Picture (Theoretical Maximum Delta-V & Pluto Transfer Time): - DFD Isp: 10,198 s (Structural Fraction F: 0.02, Delta-V max = 300 km/s) - Nuclear Electric VASIMR Isp: 4,997 s - Nuclear Electric Hall Isp: 2,040 s - Nuclear Thermal Isp: 900 s - Chemical Isp: 462 s Achievable delta-V is fundamentally limited by the structural fraction and exhaust velocity. The engine uses RF heating to create a closed field lines Field-Reversed Configuration (FRC) inside a 1-2 m magnetic mirror, producing power and thrust. - Fusing plasma acts as heating source for cool propellant flowing outside confinement region (thrust augmentation). - Performance: Thrust ~5-10 N/MWf; Specific Impulse ~10,000-20,000 s. Power Production: - Fusion deposits heat in walls (x-rays and microwaves) - ~45% radiation fraction, ~55% exhaust fraction. - Brayton cycle engine converts heat to electricity (~60% efficiency). - Excess heat rejected to space via radiator (~40%). Single launch from Earth, fly directly to Pluto with constant thrust: - Launch Mass: 10,000 kg - Engine: 1,100 kg - Radiators: 250 kg (Area 120 m²) - Fuel (D2): 7,250 kg (Liquid D2 tank 2.6 m radius) - Helium-3: 0.5 kg (Gas 3He tank 0.95 m radius) - Fuel Tanks: 400 kg - Structure: 300 kg - Payload: Orbiter 500 kg, Lander 200 kg Mission Capability: Put a 1,000 kg spacecraft into orbit around Pluto, beam power to a lander using optical transmission, return high-definition video, and arrive in less than 5 years. DFD differs from traditional fusion reactor concepts (e.g., Tokamaks): 1. Unique heating method: Rotating Magnetic Field (RMF) current drive; efficient drive at magnetic null. 2. Simple configuration: Linear array of coils, modular assembly that can be pulled apart in segments. 3. Small size: 1-10 MW, 2 m diameter, developed in 5-10 years (compared to tokamaks at 1000-4000 MW, 60 m tall, 30-50 year development). 4. Clean operation: D-3He aneutronic fuel. - Primary reaction: D + 3He -> 4He (3.6 MeV) + p (14.7 MeV) [98.4% power] - Side reactions: D + D producing T and n (<1.6% combined power) - Tritium is exhausted before it can fuse (<20 ms residence time). - Less than 1% power in neutrons. - PFRC-1 (concluded 2011): Demonstrated rapid electron heating (>200 eV), stability 10^3x better than MHD predictions, and indirect FRC formation. - PFRC-2 (operating): Demonstrated electron heating >500 eV, 100x improved particle confinement, and stability 10^5x better than MHD. Operating up to 40 kW power. - Upgrades under ARPA-E OPEN grant: Higher RF and magnet power, lower frequency to heat ions directly. - Computational tools applied: LSP (particle-in-cell), kinetic Hamiltonian model (RMF), and UEDGE (multi-species fluid model for SOL heating and flow).