Placeholder Image

字幕表 動画を再生する

  • NASA has a mission protocol which says if

  • a low-earth orbit mission increases the

  • life time risk of the crew getting

  • cancer by more than 3% then

  • they won't go ahead with it but the

  • upcoming Mars missions may expose the

  • crews to levels which will be beyond

  • that limit and two other hazards,

  • so how dangerous is deep space travel to

  • Mars and Beyond. With Ellen musk pushing

  • to get men onto Mars by the mid-2020s

  • and NASA looking to do the same for

  • the 2013 just how much we learned since

  • Apollo and from space stations. 50 years

  • on from the beginning of the Apollo

  • missions and we have yet to send any man

  • back to the moon let alone on the much

  • more arduous journey to our nearest

  • viable planet Mars. Now whilst much of

  • this as being down to the lack of

  • political will in the face of our own

  • man-made problems here on earth

  • it's also down to be increasing

  • sophistication of robotic probes and

  • Landers that are much cheaper to make

  • launch, can go where no man could go and

  • continue working for years of the time.

  • The Voyager probes for example are still

  • going 40 years after their launch. If we

  • relied upon man discovery only we would

  • know a fraction of what we know now. With

  • data from probes that we have sent

  • around solar system since then we have

  • built up a picture which is far from

  • the vision of just whizzing through

  • interplanetary space that along with the

  • joint NASA-Russian experiment of having

  • been in space for a year on board the

  • International Space Station, we now have

  • a much better understanding of what they

  • may experience from the two-and-a-half

  • year round trip tomorrow. We humans

  • evolved on earth and our bodies are

  • adapted from moving around under the

  • effects of 1g of gravity, take that away

  • and problem start to arise our

  • physiology. We often forget what a

  • sheltered life we all leave here on our

  • little blue dot in the harshness of space.

  • We are protected from 99.9% of

  • harmful radiation not only from the Sun

  • but also from other galactic sources by

  • our atmosphere the Earth's magnetic

  • field and the Van Allen belt,

  • yes they make a pain for space travel

  • but they do protect us from further

  • radiation on earth. Get beyond the

  • shelter of these and open space is far

  • from empty, it's teeming with not only

  • radiation from our Sun but also much

  • more powerful radiation from outside our

  • solar system in a form of galactic

  • cosmic rays and gamma rays. Most of the

  • hard data we have about the levels of

  • radiation in deep space comes from the

  • radiation assessment detector instrument

  • which was aboard Mars rover Curiosity,

  • part of the bar science laboratory which

  • was launched in November 2011. The

  • radiation assessment detector was turned

  • on for about 220 out of 253 day journey

  • to Mars and showed that the radiation

  • levels were between 100 and 1000 times

  • higher than that on the earth for an

  • unshielded occupant but it was highly

  • variable and depended a lot on the

  • solar activity at the time. Experiments done on

  • earth with Beam accelerators, computer

  • modeling and confirmation from the

  • cosmic-ray scope on the lunar

  • reconnaissance orbiter as it goes around

  • the moon has shown that plastics with a high hydrogen

  • content are more effective than the same

  • weight of aluminium at stopping particle

  • radiation from both the Sun and galactic

  • cosmic rays and this has been

  • incorporated into the latest spacecraft

  • design like the NASA Orion and the SpaceX Dragon 2. Galactic cosmic rays are

  • protons and nuclei of atoms which have

  • been expelled from supernovas and other

  • violent cosmic events and have been

  • accelerated to near the speed of light.

  • Because of this

  • they have a much greater energy level

  • and can right through space craft

  • and the crew.

  • Shielding helps but it's a compromise

  • between thickness of the shield the

  • extra weight involved which makes it more

  • difficult then to get into space from

  • Earth. To contend with solar flares, a

  • radiation shelter in the craft where

  • there is extra shielding has been

  • proposed with SpaceX Mars mission. Liquid

  • hydrogen or water storage tanks around

  • the crew areas provide a good shield

  • against particle radiation and creating

  • a strong magnetic shield around the crew

  • areas are all possible but don't protect

  • well against electromagnetic wave

  • radiation gamma-rays. Using the curiosity

  • data has been calculated that the

  • radiation risk of a return journey to

  • Mars will be about 600 millisieverts

  • equivalent to about 50 full-body CT

  • scans over that period or being on the

  • International Space Station for 4 years

  • straight.

  • This is also about 30 times the yearly

  • allowance for a radiation worker and

  • that doesn't include stay on Mars itself.

  • A dose of one sievert or 1000 millisieverts

  • is associated with a lifetime increase in

  • fatal cancers by about 5%,

  • which is near the level of the whole

  • mission including stay on Mars. This

  • would be a career limit any of the crew

  • and young women are at a higher risk of

  • cancer from radiation compared to older

  • men so that could affect the crew make

  • up. Along with the cancer risk there's

  • also be increased chance of developing

  • cataracts as the radiation passes

  • through the eye.

  • Recent research has also suggested that

  • the effects of galactic cosmic rays

  • damaging brain cells at the molecular

  • level could cause brain damage

  • similar to the onset of dementia which

  • could show within the duration of the

  • journey. Away from the radiation risks

  • they're also physiological effects of

  • microgravity on the human body.

  • NASA astronaut Scott Kelly spent 340

  • days in space on the International Space

  • Station and even with a tough

  • two-and-a-half-hour exercise regime each

  • day, he still experience problems

  • with circulation, eye sight as well as a

  • loss of bone and muscle mass. Once in space

  • the fluids in the body no longer have

  • gravity to pull them into the lower

  • extremities and are equally distributed

  • around the body. One of the effects of

  • this is to make the back of the eye

  • swell up and alter their shape which effects

  • vision. Stays on the International

  • Space Station of about a week were quickly

  • reversed when back on earth but lasted

  • for much longer after several months in

  • microgravity. On earth the heart pumps

  • blood around the body and the veins in

  • the legs squeeze the blood back to the

  • heart. In space the same amount of blood

  • is being pumped by the heart but there

  • is much less effort required to return it

  • to the body

  • this allows cardio muscular system in

  • the legs to weaken over time again. When

  • returning to a gravity environment this

  • can cause extreme dizziness and fainting

  • due to the lack of blood been returned

  • to the upper body and brain which could

  • occur the when they reach Mars. Within five

  • months of being in a microgravity

  • environment, astronauts can lose up

  • 40% of their muscle mass and

  • 12% of bone mass, this increases the

  • risk of bone fractures when returning to

  • a gravity environment and it's like

  • turning a 20 year-old into a

  • 60-year-old in just a few months.

  • Psychological issues are also a problem

  • to people in isolated areas for long

  • periods. Some scientists that worked all

  • year round in Antarctica suffer mental

  • health disorder called "Winter Over Syndrome"

  • which is characterized by symptoms such

  • as depression, irritability, aggressive

  • behavior, insomnia and memory problems

  • all the sort of things you don't want to

  • happen when trying to perform mission

  • critical tasks in space or on Mars.

  • Humans traveling in open space is always

  • going to be a risky business and in the

  • end some say the risk is worth the

  • reward of getting men to Mars and they can

  • do much more than a robot in a short

  • space of time and they are much better

  • at handling unexpected situations. But dead

  • or dying crew is something no one wants

  • to see beamed back to earth so it's in

  • all our interests

  • to make sure the risks are minimized as much as

  • possible. It will be over 50 years since

  • the last Apollo flight by the time the

  • earliest Mars missions come around, so

  • even just take a little bit longer than

  • expected, it won't make that much

  • difference to make sure that we get it

  • right.

  • What do you think of the Mars mission

  • and the risk of traveling in deep space?

  • let me know in the comments below and

  • don't forget to subscribe rate and share

  • and also check out some of our other

  • videos you may find interesting.

  • So thanks for watching and I'll see you

  • in the next video.

NASA has a mission protocol which says if

字幕と単語

動画の操作 ここで「動画」の調整と「字幕」の表示を設定することができます

B1 中級

火星やその先への深宇宙旅行はどれほど危険なのか? (How Dangerous is Deep Space Travel to Mars and Beyond ?)

  • 21 3
    Liang Chen に公開 2021 年 01 月 14 日
動画の中の単語