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  • Chemical rockets have done a lot for humanity.

  • Liquid hydrogen and liquid oxygen engines powered the Space Age, but they can only get us so far.

  • If we want to travel to deep space and beyond without waiting for the planets to align,

  • we're going to have to come up with some new propulsion systems.

  • The problem with chemical rockets is the fuel is heavy, and for all that weight, it's not very efficient.

  • The fuel's energy is limited to what's stored in the chemical bonds,

  • and after 90 years of research, chemical rockets aren't going to get much better.

  • Plus, once that candle's lit, it uses all its fuel in one burst

  • and then coasts the rest of the way to the destination.

  • If the kids are yelling in the back, you can't turn this rocket around, you know what I'm saying?

  • Well, you could orient it that way with hydrazine engines like the ones satellites use,

  • but those don't actually have enough thrust to do much more than orientation.

  • Whatever way the chemical rocket was pointing, that's where you're going.

  • So to explore deep space, NASA is looking past the energy stored in chemical bonds.

  • Another propulsion technology that's been around since the 60s is just showing promise in the last 20 years: ion engines.

  • Ion engines work by accelerating charged atoms, like xenon ion, through a magnetic field, and out the back of the spacecraft.

  • The fuel is lightweight and provides a low amount of thrust over a very long period of time,

  • so in theory, they're great for long-term deep-space exploration.

  • Early engines, though, destroyed themselves as the ions eroded the walls and it's hard to have a long-term mission with a short-term engine.

  • Engineers have finally cracked the puzzle by diverting the magnetic field around the walls, to stop the ions from bombarding it, and recent missions

  • like the Dawn Space Probe, sent to the asteroid Ceres, used ion engines to power it once it was out of Earth's orbit.

  • Another novel idea is getting rid of onboard fuel altogether, and letting the Sun push the craft along.

  • That's the principle harnessed by solar sails, and they're exactly what they sound like:

  • they're sails as large as a football field, and 40-100x thinner than a sheet of paper.

  • When fully unfurled, they catch the sun's light, and away they go.

  • Despite photons having no rest mass, they do have energy, which means they do carry a tiny amount of momentum.

  • When they bounce off the craft's surface, they impart their momentum.

  • So, an enormous sail out in space can take advantage of the practically endless stream of photons from the Sun,

  • accelerating for as long enough light keeps hitting it.

  • The Japanese space agency JAXA launched the first solar sail IKAROS in 2010,

  • and one month after it unfurled, JAXA reported the craft was accelerating due to photonic pressure.

  • (Just don't go too close to the Sun, IKAROS.)

  • Solar sails work well when they're close enough to the Sun,

  • but out past Mars, the power of the Sun fades, making solar sails impractical past that point.

  • If you can't wait for an ion engine or solar sail to pick up speed, there is the nuclear option...

  • literally. Some scientists have proposed using fusion or efficient propulsion systems to get humans to Mars in one month instead of seven.

  • Proposals vary, with some using nuclear reactors to generate plasma

  • that's then accelerated with a magnetic field -- like an ion engine on steroids.

  • Others would use hydrogen atoms that are forced together by collapsing lithium rings around them to generate pulses of fusion.

  • This method could provide the same amount of energy as four litres of rocket propellant with an amount of fuel as big as a grain of sand.

  • But these ideas have a lot of hurdles, and are still a long way off.

  • Then again, so are other planets,

  • and if we're going to send humans to any of them,

  • we prefer the journey be as fast as possible.

  • We'll still need chemical rockets to get us out of Earth's orbit.

  • But once we develop these technologies, who knows where we go from there?

  • Hey! While you're here, check out this next video at NASA's Jet Propulsion Laboratory

  • which shows how the design and manufacturing of future deep space exploration is sometimes based on origami.

  • Don't forget to subscribe for awesome science videos every week, and thanks for watching.

Chemical rockets have done a lot for humanity.

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Ion-Powered Rockets Could Take Us to Distant Planets in a Fraction of the Time

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    Jerry Liu posted on 2019/05/02
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