00:00First electric propulsion systems like ion and hall thrusters.
00:04NASA's Dawn mission used them to visit the protoplanets Vesta and Ceres and the Indian
00:09space agency ISRO, tested a 300 millinewton plasma thruster for 1000 hours this year.
00:19That's ideal for probes since such drives offer a high specific impulse or ISP for short
00:25in the range of several thousand seconds. But in return they only have a tiny amount of thrust.
00:31Second nuclear thermal propulsion systems. NASA also tested fuel for 45 day Mars journeys
00:39this year. They achieved ISP values of about 900 seconds. Twice as good as chemical rockets. Third
00:49directed energy like Breakthrough Starshot which accelerates small probes to 20% of the speed
00:56of light using lasers. Realistic? Yes, but only for relatively small samples. The chances are good.
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