Rail to the Stars - Superconducting Solutions to Spacecraft Propulsion

Today we will focus on high temperature superconductors and their applications to propulsion. The underlying science is critical to a full understanding of this important technology… we have focused on niobium-titanium wire for our superconductors because they are strong, durable and in use today for commercial applications. The last is very important. You want to be innovative as you design your space systems…but you don’t want to be waiting for a technological breakthrough to make it viable. If we wait on effective, economical fusion drives for space exploration we had better be in our late teens or early twenties. It is best to make systems that work with proven available technology…while keeping an eye on scientific development…closely watching those fields where a breakthrough would be immediately useful to the space industry. There are many areas that must be closely watched but some technologies effect thousands of others…one of those is superconduction. Superconductors are materials through which there is no resistant to the flow of electrons… Magnets made from superconductors are over five times stronger than non-superconducting magnets for the same amount of electrical power. The magnets in an MRI or on a levitating train are made from either niobium-titanium or niobium-tin…both of which we discussed earlier…surrounded by copper.
These are formed into solenoids…
Solenoids are just coils of conductive wire used to maximize the magnetic field produced by a current running through a wire. Here you see a solenoid coil…and here you can see one used in a stepper motor. A push type solenoid uses a spring to hold something closed…it is always pushing…but when electricity is applied to the coil it pulls the plunger back in and releases whatever it was holding against…a pull type solenoid is open or permanently pulling until activated by electricity at which point the plunger is pushed out. We will go over valves used in the space industry soon. The stepper motor is a very easy way to see how magnetic fields can be used in simple devices to make useful actuators. Remember that superconducting wires create magnetic fields over five times stronger than normally conducting materials for the same amount of power and they don’t heat up as the current is passed through. An MRI machine using either niobium-tin or niobium titanium wire will be cooled by liquid helium. Liquid helium is one of the coldest substances know to humans.
Liquid helium boils at 4.2K. Remember that if you are boiling a liquid it will maintain its temperature…expelling heat energy in evaporation…until all the liquid is a gas. That is why all boiling water at sea level is at 100 celsius. The liquid helium keeping our magnets at 4.2 kelvin is perfect since most superconducting niobium alloys have a critical temperature of 10 kelvin. Below 10 kelvin they are superconducting…above ten kelvin they are not. Helium is in limited supply on the Earth and compressing it to liquid form takes a lot of energy. It is very expensive to cool these MRI magnets so we can see into patients. If we could use liquid hydrogen…which will stay in a fully liquid state below 20 kelvin…we could do a lot more with superconductors. Niobium-Germanium has a critical temperature of 23k. We could use liquid hydrogen to cool it but it’s still very energy intensive to liquify hydrogen. On the Moon we could us liquid hydrogen form our rocket refueling tanks to keep niobium-germanium superconducting energy storage capacitors below their critical temperature. But for most applications we need superconductors that work at higher temperatures. This is where high temperature superconductors come in. High temperature here means anything above the ridiculously cold temperature of 73.15 kelvin. This is the lowest temperature reachable using liquid nitrogen. Nitrogen is abundant and relatively cheap to liquify. If we could use liquid nitrogen… we could use superconductors in a lot of applications much more cheaply.
The first high temperature superconductor discovered in 1986 was Yttrium Barium Copper Oxide. This material has nanoscale planes of copper oxide that are critical to superconducting. This material is also a ceramic meaning it is a crystalline oxide, nitride or carbide compound. These materials are hard and strong but brittle...
https://www.sciencedaily.com/releases/2019/11/191105113503.htm
https://theydiffer.com/difference-between-t1-and-t2-mri/
https://casemed.case.edu/clerkships/neurology/Web%20Neurorad/MRI%20Basics.htm
https://engineeringinsider.org/solenoid-functions/
https://supraconductivite.fr/en/index.php?p=supra-lefroid-plusfroid
https://www.sciencedirect.com/topics/materials-science/high-temperature-superconductors

Видео Rail to the Stars - Superconducting Solutions to Spacecraft Propulsion канала Terran Space Academy