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  • [♪INTRO]

  • 60 years ago this month, in January 1958, the United States launched its first satellite, Explorer 1.

  • It started a legacy and launched the longest-running space exploration program in history, so you'd

  • think making it would have been part of some big plan figured out years in advance.

  • But... nope.

  • Instead, Explorer 1 and the modified rocket that launched it were finished in just 84 days.

  • And we had a lot to figure out in those three months.

  • But somehow, we did it.

  • Like most of America's early space program, Explorer 1 was a result of the Cold War struggle

  • with the Soviet Union.

  • In October 1957, the Soviets launched Sputnik, the world's first satellite.

  • And what did the US do?

  • It freaked out.

  • Like, seriously panicked.

  • In the race to claim the high ground of space, America was clearly behind.

  • To make matters worse, when the US attempted to launch its first satellite that December,

  • it failed just over a meter off the launchpad.

  • Newspapers called itKaputnik”. Ouch.

  • Since NASA didn't even exist yet, coming up with a successful -- and fast -- response

  • to Sputnik fell to the US Army Ballistic Missile Agency and the Jet Propulsion Laboratory,

  • better known today as JPL.

  • And in an incredible feat of engineering, Explorer 1 launched not even three months later.

  • Take that, Kaputnik.

  • But that's definitely not how things were supposed to happen.

  • As a show of peace, the US had long planned to launch their first satellite on top of

  • a modified sounding rocket.

  • Sounding rockets are used mainly to help study the Earth's climate, so this would be a

  • clear signal that this was a mission of science, and that we weren't trying to start an actual

  • war with the Soviet Union or anything.

  • But after that first failure, the Army just needed something that would work, so they

  • turned to the Jupiter-C rocket, which was used as a test platform for intermediate-range

  • ballistic missiles.

  • Also, the rocket that launched Sputnik was a modified missile, not a sounding rocket,

  • so the show of peace seemed less important by that point.

  • Even though it had three stages, or segments -- which these days is more than enough to

  • launch satellites -- the Jupiter-C wasn't powerful enough to put something into orbit,

  • so the Army did the only thing it had time to do: duct-tape on a fourth stage.

  • Well, not literally.

  • But adding another stage did make the setup seem kinda ridiculous.

  • It was a like building a triple-decker bus.

  • Like, sure, it's possible to do that, but it's not exactly the most, like, elegant

  • solution, and it can create more opportunities for things to go wrong with computers or engines.

  • For comparison, most rockets today usually only have two or three stages.

  • And much better computers.

  • But even with all that, the satellite itself still had to be really small -- just 14 kilograms,

  • or about as much weight as a beagle.

  • And about 40% of that weight was needed for its battery, which didn't leave a lot of

  • weight for other things.

  • So the engineering team had to get creative.

  • To relay data back to Earth, they equipped the satellite with an innovative antenna system.

  • And byinnovative”, I mean really weird.

  • It consisted four wirewhips”, which extended into a large transmitter as the spacecraft

  • spun along its axis.

  • Also, in order to keep the radio and other instruments from getting too hot or too cold,

  • Explorer 1 needed a temperature control system, but without the weight of fancy radiators.

  • So what did JPL do?

  • They painted the spacecraft in stripes of white and green.

  • Since different colors transmit different amounts of heat, the area of white versus

  • green could be tuned for just the right equilibrium temperature.

  • On January 31st, 1958 -- 119 days after the launch of Sputnik 1 -- all this was put to the test.

  • And it worked!

  • Getting into space was a big enough accomplishment, but Explorer 1 also performed pioneering scientific

  • experiments in orbit.

  • For one, it carried a Geiger counter to make the first direct measurements of the radiation

  • environment in outer space.

  • At times the counter registered so much radiation that it overwhelmed the sensors -- which baffled scientists.

  • Eventually, they figured out this was the result of radiation trapped by Earth's magnetic

  • field, regions we now call the Van Allen Belts after the leader of Explorer 1's scientific

  • investigations.

  • The mission also carried a pair of experiments designed to measure the rate at which micrometeorites

  • strike the Earth.

  • One consisted of a wire grid mounted on the outside skin of the spacecraft.

  • If a small particle struck the grid, one of the wires would break, altering an electric circuit.

  • The other was a microphone inside the spacecraft that listened for theplinkof a particle

  • striking the hull.

  • Over about a day, it picked up 145 impacts, giving scientists their first direct measurement

  • of natural space debris.

  • None of this seems exactly hi-tech, but hey, it got the job done.

  • Even though Explorer 1 only lasted a few months, it began a program that continues today.

  • In 2013, NASA launched a spacecraft to study the atmosphere of the Sun.

  • It was called IRIS, but its official record lists it by another name: Explorer 94.

  • In the next couple of months, NASA will also launch ICON and GOLD, two Explorers that will

  • study part of Earth's upper atmosphere.

  • And this year, they'll also launch TESS, which will search 200,000 nearby stars for exoplanets.

  • By the early 2020s, we'll probably even see the launch of the 100th Explorer mission.

  • Although they've each had their own goals, all the missions in the Explorer program have

  • followed in the footsteps of America's first satellite from 60 years ago.

  • And one thing's for sure: We're definitely a lot better at building satellites than we

  • were in 1958.

  • Thanks for watching this episode of SciShow Space!

  • If you love learning about space history, news, and other weird things in the universe

  • as much as we do, you can go to youtube.com/scishowspace and subscribe.

  • [♪OUTRO]

[♪INTRO]

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アメリカが初の人工衛星を打ち上げた経緯 (How the US Launched Its First Satellite)

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    林宜悉 に公開 2021 年 01 月 14 日
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