1 00:00:00,000 --> 00:00:05,320 Well that's pretty neat. I mean, NASA uses electromagnets and this track to help them 2 00:00:05,320 --> 00:00:11,760 develop new ways to propel a spacecraft into orbit. And you know what? NASA's also using 3 00:00:11,760 --> 00:00:16,280 electricity, magnetism, and tethers to help them propel spacecraft already in orbit. 4 00:00:16,280 --> 00:00:21,440 Wait, you said tethers? Like tetherball with the pole and the rope attached to the ball? 5 00:00:21,440 --> 00:00:26,800 Absolutely. Some other examples of tethers besides tetherball are the elastic string 6 00:00:26,800 --> 00:00:32,440 that keeps a paddleball on a paddle, a fishing line that keeps the fish on a pole, and even 7 00:00:32,440 --> 00:00:37,720 a leash that keeps a dog close to its owner. Maybe you can think of some more examples. 8 00:00:37,720 --> 00:00:44,720 You know, NASA has been using tethers and conducting experiments in space for years. 9 00:00:44,720 --> 00:00:56,360 You're right. In fact, in the 1960s, the Gemini astronauts used tethers to connect their spacecraft 10 00:00:56,400 --> 00:01:03,400 to another unoccupied rocket. The 1960s! Far out, man. What? 11 00:01:07,560 --> 00:01:12,200 Over the years, NASA has learned that connecting two spacecraft together opens up a whole new 12 00:01:12,200 --> 00:01:18,520 world of possibilities, like propelling a spacecraft. One person who knows all about 13 00:01:18,520 --> 00:01:23,240 tethers in space is physicist Les Johnson, and he works at NASA Marshall Space Flight 14 00:01:23,240 --> 00:01:26,360 Center. Thanks, Van. We're testing a new kind of 15 00:01:26,360 --> 00:01:30,760 propulsion system for space that doesn't need any rocket engines or fuel. Instead, it'll 16 00:01:30,760 --> 00:01:34,160 use the Earth's magnetic field to help push or pull on the spacecraft. 17 00:01:34,160 --> 00:01:38,200 All magnetic objects form invisible lines of force that extend between the poles of 18 00:01:38,200 --> 00:01:44,000 the object. A magnetic field is the space around a magnet where you feel its force. 19 00:01:44,000 --> 00:01:49,920 Magnetic field lines extend and radiate between the Earth's north and south poles, and between 20 00:01:49,920 --> 00:01:53,040 the poles of a magnet. Basically, the Earth's magnetic field works 21 00:01:53,040 --> 00:01:56,880 with a special type of wire or conductor called an electrodynamic tether to push or 22 00:01:56,880 --> 00:02:00,800 pull on the object. The electrons that make up the electric current flowing through the 23 00:02:00,800 --> 00:02:05,520 conductor will experience a force when they move through a magnetic field like the Earth's. 24 00:02:05,520 --> 00:02:09,880 Since they're trapped in the conducting wire tether, the force will be applied to the tether 25 00:02:09,880 --> 00:02:13,680 and whatever is attached to it. Depending upon the direction in which the current is 26 00:02:13,680 --> 00:02:18,720 flowing, this force can be a push or a pull, either lowering or raising a spacecraft's 27 00:02:18,720 --> 00:02:21,920 orbit. So the direction of the current determines 28 00:02:21,920 --> 00:02:25,160 whether it's pushing or pulling. And the more current, the more force. 29 00:02:25,160 --> 00:02:29,800 Right. In fact, NASA Marshall is working on a project called PROSEDS, which uses the Earth's 30 00:02:29,800 --> 00:02:34,080 magnetic field to push or pull on the attached tether. When the tether moves, so does the 31 00:02:34,080 --> 00:02:37,880 spacecraft. Les, PROSEDS is an acronym, right? What does 32 00:02:37,880 --> 00:02:41,440 it stand for? PROSEDS stands for Propulsive Small Expendable 33 00:02:41,440 --> 00:02:46,760 Deployer System. Space exploration is limited largely by the cost of launching payloads. 34 00:02:46,760 --> 00:02:50,920 Finding a cheaper way to explore space is always very important to us. Typically, a 35 00:02:50,920 --> 00:02:55,480 rocket will place its payload into low-Earth orbit, and from there, propellant-fueled thrusters 36 00:02:55,480 --> 00:03:00,360 have to boost it to a higher altitude. PROSEDS is one experiment that focuses on the technology 37 00:03:00,360 --> 00:03:03,800 to cut the expense of placing a payload into its final orbit. 38 00:03:03,800 --> 00:03:08,800 Sounds like PROSEDS can be a nice alternative to using rocket engines and lots of fuel. 39 00:03:08,800 --> 00:03:13,880 Absolutely. Electrodynamic tethers could one day be used as a cheap, lightweight, and reliable 40 00:03:13,880 --> 00:03:18,520 way to remove space junk from orbit, keep the International Space Station in orbit, 41 00:03:18,520 --> 00:03:23,880 and even power missions to other planets. Wow! This can get us to other planets? 42 00:03:23,880 --> 00:03:28,120 Tethers offer unlimited possibilities, man. That's why I'm all charged up about this project.