Improved Magnetic Sail presented at Mars Society Conference

The Mars Society had their 20th conference on sept 7-10, 2017 in irvine, California.

On Sept 7 there were several presentations by Craig Davidson.

Craig is proposing improvements to the Zubrin Magnetic Sail and novel ways to test and use improved magnetic sails.

Sharkfin Magnetic sail

The SharkFin Magnetic Sail looks to go beyond the Zubrin Magnetic sail with the Lorentz Force law, Faraday’s law, and Lenz’s law to harvest propulsive force and electrical charge from large scale electromagnetic fields such as the Magnetosphere, Heliosphere, or Interstellar Magnetic Field (ISMF). Advances in superconducting cable design, including a self-insulating cable patented by Dark Sea Industries (patent pending), allows combining the benefits of electric/magnetic sails with advances in low voltage high current carrying capacity superconducting cables to provide a system which provides both power and propulsion to the spacecraft. The synthetic magnetosphere which envelopes the craft can also help slay a famous dragon, by eliminating exposure to charged radiation, leaving only neutral radiation to be absorbed by a shield (such as water ice). Magnetic sails are thus seen as the power/propulsion system of choice for interplanetary spacecraft.

The new design uses modern day superconductive wire, wrapped in an aerogel envelope, with a liquid coolant to provide thermal mass to keep the average temperature low, and an active conductive cryocooler to cool the coil down to operating temperature. Using liquid nitrogen, and one turn for every 10cm, a B field of 5 Tesla results, but the wire can only handle 2000 Amps. To get to 100,000 Amps, 50 strands of wire are required. The nice thing is that voltage is essentially a free variable here (up to the limits of the wire), so 100v provides a 10MW power supply and 1000V provides a 100MW power supply. Using an estimated weight of 1.2kg/m, 50 strands would be 60 kg/m, so a 6m cube at 10 cm spacing would be 4x60x60kg (leaving two faces uncovered, for a total weight of 14,000 kg. Super-capacitors and regulator electronics would total another 14,000 kg, for a total weight of 28,000 kg. This yields a kw/kg ratio of 3.57, easily 10 to 100 times better than nuclear power (due to lack of shielding and fuel). Note this is a dual redundant 100MW power supply versus a non-redundant nuclear supply.

Craig also had an unsuccessful Indiegogo to fund a test of his new ideas in magnetic sails.

The problem for ground based magnetic propulsion is that the field strength, unless there is a thunderstorm, can be measured in micro-amps, and provides no effective propulsion. At altitudes above 100,000 feet, there is a current in the atmosphere called the Birkeland Current, which has values up to 100,000 amps, and routinely peaks above a million amps (near noon and midnight). The current doesn’t reach its full value until it reaches the bottom layer of the Ionosphere, which varies between night and day. At night the E layer and F layer are present, starting at about 290,000 feet. During the day, a D layer forms at as low an altitude as 180,000 feet, and the E and F layers become much stronger. Often during the day the F layer, which starts at about 475,00 feet, will differentiate into F1 and F2 layers.

The Birkeland current is a ribbon about 285 miles wide by 1500 miles long, stretching from a circle around the magnetic pole (north or south), centered on the noon and midnight axis, one ribbon on each side of the globe. The ring is where we see the Aurora Borealis or Aurora Australis.

Birkeland current is described in Wikipediaa

He wanted to get an improved magnetic sail into the Birkeland current.

Craig Davidson has a patent for Thrust Augmentation Systems

Craig’s patent proposes augmenting thrusts using ionized gases. A gas is partially ionized, which then ionizes a second, neutral gas. A magnetic field creates a Townsend cascade in the ionized gases, greatly increasing the amount of ionized gases. To produce thrust the ionized gases are accelerated through a coil, which can have logarithmically increasing coil spacings. In another embodiment, electromagnetic forces in the atmosphere can be used to propel a vehicle that has parallel superconducting coils circumferentially disposed about an axis of travel of the vehicle, the coils comprising one or more moveable segments which are reversibly disconnectable from other segments in said coil, thereby allowing the polarity of the coil to be reversed. The ionization engines described above can be used to further accelerate or decelerate the vehicle.

The present invention is a method of generating thrust using an ionized gas, the method comprising ionizing a portion of a first gas; the ionized first gas ionizing a portion of a second gas in a magnetic field; and the magnetic field creating a Townsend cascade in the first and second ionized gases; and accelerating the ionized gas to create thrust. The magnetic field is preferably produced without requiring external power. The magnetic field is preferably produced by permanent magnets, electromagnets or superconductive electromagnetic coils, is preferably solenoid shaped, and preferably has a strength of greater than approximately one Tesla. The first gas is preferably ionized by a device selected from the group consisting of plasma torch, electric thruster, ionization pad, laser, solid rocket motor, chemical laser, and trigger diode. The second gas is optionally the same as the first gas, such as the unionized portion of the first gas. The method preferably further comprises increasing a velocity of the first ionized gas using vector addition, which is preferably generated by interactions of ionized gas particles via their gyroradii, preferably in a chamber comprising one or more high temperature paramagnetic materials. A difference between a velocity of the first gas and a velocity of the second gas preferably exceeds the Critical Ionization Velocity of at least one element in the second gas, so that preferably substantially every molecule of the element is ionized. The accelerating step preferably comprises passing the ionized gases pass through one or more coils comprising a logarithmically increasing spacing of adjacent coil segments after the step of creating a Townsend cascade. The coils preferably comprise a material selected from the group consisting of permanent magnetic, electromagnetic, or superconductive and can be arranged in series and/or in parallel. The ionized gases are preferably subsequently passed through an exhaust nozzle comprising a cone surrounded by a plurality of accelerator coils. At least one of the accelerator coils preferably comprises segments which can be selectively energized, thereby enabling control of directionality of an exhaust ion stream. The cone is also preferably surrounded by a plurality of generator coils which extract energy from the ionized gases. The method optionally comprises subsequently passing the ionized gases through a turbine to generate power.

The present invention is also a vehicle for traveling in an electromagnetic field of a celestial body, the vehicle comprising a plurality of parallel superconducting coils circumferentially disposed about an axis of travel of the vehicle, each coil comprising one or more moveable segments which are reversibly disconnectable from other segments in the coil. The polarity of each coil is preferably reversible when one of the moveable segments is disconnected from the coil. Each coil preferably comprises an aerogel jacket comprising a superconducting member surrounded by a cryogenic fluid. Solenoids preferably move the moveable segments, and seals prevent leakage of the cryogenic fluid. The vehicle optionally further comprises one or more engines for producing an electromagnetic field for accelerating or decelerating the vehicle.

About The Author