Direct Fusion Drive (DFD) FD is a conceptual fusion-powered spacecraft engine. It should produce between 5-10 Newtons thrust per each MW of generated fusion power, with a specific impulse (Isp) of about 10,000-20,000 seconds. They would have 200 kW – 2MW available as electrical power. Approximately 35% of the fusion power goes to thrust, 30% to electric power, 25% lost to heat, and 10% is recirculated for the RF heating. The design uses a specially shaped radio waves (RF) “antenna” to heat the plasma.
The ISP is about 20,000. 5 to 10 newtons are generated per megawatt of fusion power. They are looking at 1 to 2 megawatts for the initial space system. This would thus produce 10 to 20 newton using a 2-megawatt system. They want to get their machine cycle down to 3 years. They want to complete the system for less than $100 million.
They believe they can also make a pure energy generation system. They refer to this as closed loop mode.
It would produce thrust from fusion without going through an intermediary electricity-generating step. It will use magnetic confinement and heating system, fueled with a mixture of helium-3 (He-3) and deuterium (D), to produce high specific power, variable thrust and specific impulse, and a low-radiation spacecraft propulsion system. They will heat plasma to 100 keV (which is 1,120,000,000 degrees K)
The plasma is confined in a torus-like magnetic field inside of a linear solenoidal coil and is heated by a rotating magnetic field to fusion temperatures. Bremsstrahlung and synchrotron radiation emitted from the plasma are captured and converted to electricity for communications, spacecraft station-keeping, and maintaining the plasma’s temperature.
Princeton Plasma Physics Laboratory has licensed the technology for Direct Fusion Drive (DFD) a fusion-powered rocket engine that could take people on a mission to orbit Mars for 30 days with total trip duration of 310 days.
They would create a cigar-shaped plasma—the superhot, electrically charged gas that fuels fusion reactions—inside a cylinder that is some 20 feet long and could produce up to 10 million watts of power. Propulsion would come from the stream of high-speed fusion exhaust that would blast into space through a magnetic nozzle.
A test facility, based on a concept known as magnetic field reversed confinement, could be completed by 2022.
Princeton technology can cut costs of RF equipment and reduce power consumption in NASA’s existing RF-based laboratory research and aerospace manufacturing operations. The improved RF gear can be used for microwave-heated thrusters and communication systems up to S-band. The switching amplifiers are also said to be more efficient than current RF systems using tubes, such as Traveling Wave Tube Amplifiers (TWTAs) and Solid State Power Amplifiers (SSPAs).
Princeton’s novel amplifier will have commercial applications:
HF band radars for coastal and over horizon systems (OTH)
Medium (MF) and High Frequency (HF) Radio (ITU Bands 5 and 6)
Communications channels up to S-band
Plasma heating for terrestrial fusion reactors
RF heating for manufacturing
SOURCES- Princeton Satellite Systems, NASA, Tennessee Valley Interstellar Workshop, FISO Future In-Space Operations working group, SBIR grants, NASA NIAC
Written By Brian Wang, Nextbigfuture.com