00:00Let's say a spacecraft runs out of power far in deep space.
00:05It wouldn't fall in the traditional sense because there's no gravity.
00:09Newton once said that an object remains in motion unless acted upon by an external force.
00:15In our case, this external force is gravity.
00:19In other words, if there's nothing with gravity around, it would continue to move due to inertia.
00:25It would keep going the way it did, without us being able to change its trajectory or
00:29adjust it in any way.
00:32It would keep traveling through deep space almost forever, well at least until radiation
00:37and cosmic rays destroy it.
00:40And unless some celestial body like an asteroid doesn't destroy it either.
00:45And of course, unless it encounters something with a gravitational pull like a planet or
00:50a star.
00:51The likelihood of all this depends on the location and trajectory of the spacecraft.
00:57Voyager 1 was launched by NASA in 1977.
01:01It's been on its journey for almost 50 years now.
01:04Right now, it's the farthest human-made object from Earth, more than 50 billion miles away.
01:11It's already very far from all our planets, and it's the first spacecraft to enter interstellar
01:16space, the vast, empty space that exists between stars in a galaxy.
01:22It's the space outside our solar system, where there are no planets, moons, or other objects
01:29associated with our Sun.
01:31However, it's still in our solar system.
01:34To leave it, Voyager 1 needs to bypass the Oort cloud, a big, icy collection of objects
01:40where all the comets in our solar system probably come from.
01:44It will take Voyager about 300 years to reach the inner edge of the cloud, and then about
01:4930,000 years to bypass it.
01:52Voyager 1 has a special plate on board, like a message in a bottle.
01:57This plate is called the Golden Record.
02:00It's not really golden, it's actually a shiny gold color.
02:03On this plate, there are things that tell a story about Earth.
02:07It was created in case Voyager ever encounters any extraterrestrial beings.
02:13The record has greetings in different languages, music from Earth, and even the sounds of nature
02:18like birds chirping and the wind blowing.
02:21As the distance between us increases, the signal strength from Voyager 1 weakens over time.
02:28Eventually, it may become too weak to be detected by our communication equipment.
02:32The power output of Voyager 1's engine also declines over time.
02:37It's slowly running out of fuel.
02:40When all its systems shut down, we will lose contact with the spacecraft.
02:45Voyager 1 will work until 2025.
02:48After that, it will continue its journey on inertia.
02:51Luckily, it was designed to last, and the chance that it will encounter anything on
02:56its way is very small.
02:59Considering this, it might even keep going for billions of years.
03:03One day it might even reach other star systems, and maybe even outlast our Sun.
03:09The same goes for Voyager 2.
03:11It will keep traveling until it reaches interstellar space, joining its twin brother.
03:17Voyager 2 will continue to send us scientific and systematic data for a while even in interstellar space.
03:24However, it will also cease to function eventually, becoming a silent artifact drifting through
03:29the Milky Way.
03:32When there's something with gravity near the spacecraft, the inevitable happens.
03:36It falls onto that object.
03:39This is why out of the vast South Pacific Ocean beyond New Zealand lies a unique and
03:44intriguing place known as the Spacecraft Cemetery.
03:48Officially, it's called the South Pacific Ocean Uninhabited Area.
03:52It's located near Point Nemo, the most remote spot from any island.
03:57It serves as the final resting place for spacecraft that have completed their missions and reached
04:02their lifetime limit due to wear and tear.
04:06Sometimes, these larger spacecraft are too hefty to burn up during re-entry into Earth's atmosphere.
04:12In that case, they're directed to crash or splash down in this remote ocean location.
04:17This helps protect us from any potential harm during re-entry and impact.
04:22There are, however, some big problems with this place.
04:27Scientists are worried about the impact this spacecraft cemetery has on the ocean.
04:32When spaceships come back to Earth, they often spill chemicals.
04:37One of these chemicals is hydrazine, a dangerous rocket substance.
04:41Unfortunately, it might not completely burn up during re-entry, so it leaks out into the
04:46ocean, posing a threat not only to marine life, but to us as well.
04:51We made up some rules, both within countries and internationally, to stop this.
04:56However, it's not easy to figure out how risky it is for certain spacecraft to enter the
05:00cemetery.
05:02We can't say for sure how much of a substance is left after it enters the air.
05:08As for spacecraft that don't fall, they're often left in space as debris.
05:13This is what we call any man-made object orbiting Earth that's no longer useful.
05:19It's also very dangerous.
05:20There are over 27,000 pieces of space debris orbiting Earth at high speeds.
05:26All this puts human and robot missions at risk and harms spacecraft.
05:33As we mentioned, usually we get rid of space debris by trying to bring the crafts back
05:37to Earth.
05:39This makes them burn up when they re-enter due to high speeds and air pressure.
05:44This usually works with smaller objects.
05:47There are also riskier methods, like letting spacecraft break down themselves or crash
05:52into other things or blow up.
05:55These methods aren't great because they just make up even more debris, even if it's smaller.
06:00So now, scientists are trying to find new ways to get rid of retired spacecraft.
06:06For example, nets and magnetic arms.
06:10There's also a thing called reusable spacecraft.
06:14It's a space vehicle that's built to be used more than once.
06:17For example, space planes such as the Space Shuttle and the Dream Chaser or capsules like
06:22the SpaceX Dragon.
06:24They're designed to launch, orbit, come back to Earth and do it all over again.
06:30But it's important to make sure these spacecraft and their passengers or cargo stay safe during
06:35the return, which is quite hard to do.
06:38Reusable spacecraft have special systems to guide them back to Earth safely.
06:43The Space Shuttle, for example, had OMS pods, sort of special backpacks that help the spacecraft
06:49move and control its position in space.
06:52The SpaceX Dragon had its own engines to slow down and enter the atmosphere in a controlled
06:58way.
06:59They also have a heat shield to protect it during re-entry.
07:03The heat shield can be made of different materials, but they need to be tough and able to withstand
07:08multiple trips.
07:10Coming up with a heat shield that's both strong and lightweight is a bit of a challenge.
07:16Finally, if a spacecraft lands on a runway, it needs wings and landing gear.
07:21They also add weight.
07:23Some designs like lifting bodies or the delta wing of the Space Shuttle try to reduce the
07:28mass of these parts.
07:30After landing, the spacecraft might need some fixing up before it can go on its next adventure.
07:36This process can take a while, up to a year, and it might not always be possible to use
07:40the spacecraft again if it's been fixed up.
07:44There's also a limit to how many times a spacecraft can be fixed and used again before it has
07:49to retire.
07:51Different spacecraft have different abilities to be reused.
07:55Finally, sometimes we can rescue a spacecraft, or even remake and repurpose it.
08:02Voyager 2 is one of the examples.
08:04It had a little trouble with its radio in 1978.
08:08Engineers fixed it by using a backup system.
08:11Since then, it's been exploring our solar system for over 40 years.
08:16The Hubble Space Telescope is the most famous telescope we have, the grandfather of them
08:21all.
08:22However, it had a blurry start in 1990.
08:25The work wasn't done at all as expected.
08:28The pictures were of low resolution.
08:30Luckily, astronauts fixed it right in space in 1993.
08:35To do that, they used some corrective mirrors.
08:38Now it gives us fantastic views of the universe!
08:42As you can see, even in bad scenarios, there are many possible options to solve spacecraft-related
08:48problems.
08:49That's it for today!
08:50So, hey, if you pacified your curiosity, then give the video a like and share it with your
08:55friends!
08:56Or, if you want more, just click on these videos and stay on the Bright Side!
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