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10:04
Transcript
0:00
Why can't we fly a plane into space
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what stops it from just flying higher and
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higher until it in space.
0:08
well there are several issues but
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assuming we are in something like a
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normal jet airliner then one of the main
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problems is the air or lack of it as we
0:18
get closer to space.
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0:19
a plane flies because it is propelled
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forward the wings which shaped to make
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the air flow faster of the top of them
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rather than the bottom generate lift as
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the plane goes faster the wings create
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more lists when the lift is greater than
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the weight to the plane it will climb into
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the air. As our playing climbs higher and
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higher into the atmosphere the air
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becomes less and less dense the plane to
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0:46
fly faster to create more iift until
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eventually it reaches an altitude where
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the engines either cease to function
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correctly because of the lack of oxygen
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or the air is too thin to create enough lift.
0:59
Just as we need air to breathe then the
1:02
engine need oxygen to burn to create
1:05
thrust to propel the plane forward just
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engines however engines can work at higher
1:09
altitudes than people. We humans have a
1:11
limit about 8,000 meters or 26,000 feet
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above which is what climbers
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call the "Death Zone", this is where there
1:20
is not enough oxygen for humans to
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survive for sustained period. The summit
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of Mount Everest is 29,000 feet high in
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the air density there is about
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33% of that at sea level.
1:34
This means that with each breath you
1:36
take you're only getting
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33% of the oxygen. If you want to
1:40
stay at this altitude without additional
1:43
oxygen you would suffer from a condition
1:45
called hypoxia were due to a lack of
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oxygen to the body starts to slow shut
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down and die.
1:53
At 12,000 meters or 40,000 feet which is
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the upper limit for most modern
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airliners the air density is about
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18% of that at sea level. If you
2:04
were in a plane that had a rapid
2:06
decompression at 40,000 feet you'll have
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about five maybe ten seconds to get your
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emergency oxygen mask on before you
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became unconscious. The highest flying
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jet plane in level flight was the
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Lockheed SR-71 blackbird with a height
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of 85,069 feet 42,929 meters
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and where the a density is just 2% of
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that sea level. At that height it's
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traveling at mach 3.2 or 2190 miles an
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hour. The SR-71 pilots had to wear a full
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pressure suit with its own oxygen supply
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in case of a cockpit decompression or
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emergency ejection and this was put to the
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test when you 1966 an SR-71 piloted by
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Bill Weaver disintegrated that mach 3.1
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at an altitude the 78,000 feet as it was
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performing a test flight to ironically
3:08
optimizing performance. At that altitude
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your blood will boil in a similar way to
3:14
when you open a bottle of fizzy drink as
3:16
the nitrogen in your blood to the gas in
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the low-pressure atmosphere. The pressure
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suit work and Weaver survived the
3:24
descent from 78,000 feet but tragically
3:27
the navigator Jim's Zwayer died of a broken
3:30
neck resulting from break of the
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plane. Now while you would think that the
3:34
SR-71 soft to get into space you need to
3:38
reach what is called "escape velocity"
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this is where you are traveling faster
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than gravity is pulling you back to work
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and that is 25,020 miles an
3:49
hour or 40,270 km/h and
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and if that wasn't a problem there's
3:54
also to recognized altitude at where
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space starts at 328,000 ft
3:59
or 100,000 meters
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well over three times the
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highest flight of the SR-71. Normal jet
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engines like those in the SR-71 have a
4:12
maximum air speed limits for around
4:13
about Mach 3.5 or 2695 miles now beyond
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that the air pressure and temperature
4:20
becomes too high for compresses and the
4:22
engine to effectively. For hypersonic
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speeds, experimental unmanned aircraft
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like NASA X-43 use what is called a scramjet
4:32
engine. The X-43 is currently the fastest
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free flying air-breathing aircraft in
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the world having flown at mach 9.6 or 7310
4:44
miles an hour in November of 2004.
4:47
Scramjets do away with the turbine
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compressors of the jet engine so they
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have no moving parts instead they use
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shock waves in the engine to compress
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the raise the temperature in the engine to
5:00
burn fuel and create trust an in theory
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they can fly up to Mach 20 and possibly
5:06
beyond. The problem with this is that
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they won't work at speeds of less than
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around Mach 5 so they have to be
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brought up to speed by rocket engine
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booster before they can operate, which is
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how NASA x43 worked. They also won't
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work in space because there is no air
5:25
with oxygen in to combust the fuel
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So this why space vehicles are
5:31
launched by Rockets. Rockets can have
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much more power and can operate from a
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speed of zero on the launchpad to Mach 33 and
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beyond which is the escape velocity of
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Earth. One of the earliest experimental
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space planes was the North American X-15
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which reached a height of 353,000 feet
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or 107,000 meters 1963 and was
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powered by a liquid rocket danger but it
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had to be carried up to 45,000 feet
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attached to the underside with B-52
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bomber before being released. Then of
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course we've had space shuttle the
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Soviet version of the Space Shuttle
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the "Buran", SpaceShipOne and the Boeing X-37,
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all of which were examples of space
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planes but we're really just rocket powered gliders.
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Rocket differ from Jets
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because they bring their own oxygen to
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burn the fuel and don't rely on the
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atmospheric oxygen.
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This means that they can working space
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equally as well as in the atmosphere. The
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problem with rockets is that because they
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need to bring the oxidizer with they makes
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them very heavily. Look at the space
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Shuttle for example, the external fuel
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and the tanks to hold it along with the two
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solid rocket boosters weighed 1,940 metric
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tonnes at liftoff and that's without the
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space shuttle. All of which has to be
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carried along with the shuttle to the
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edge of space where they are they
7:00
jettisoned. The maximum payload the shuttle
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could deliver it into a low earth orbit was
7:05
27.5 metric tons, which as a payload
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fraction is just 1.3% of the total
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take off weight.
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Rockets however can create huge amount
7:19
of power, so they can achieve the
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speed that is need to escape the pull
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of gravity and go into orbit and Beyond.
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But what of the future, will we ever get
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planes that can take off from an
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aircraft runway, fly into space and then
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return back to a runway. There are
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still considerable technical issues to
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overcome but one design which looks
7:42
promising is the Skylon. This is an SSTO
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or Single Stage To Orbit design meaning
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that unlike a rocket, it stays in one
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piece rather than having a separate main
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booster stage which detaches and return
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to Earth and then a smaller second stage
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which one goes on to orbit. The key
8:02
technology makes Skylon work is the SABRE or
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Synergetic Air Breathing Rocket Engines.
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Now these are kind of hybrid jet rocket
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engine which can take off like a normal
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jet engine, breathe air upto 93,000 feet
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and at a speed up to Mach 5.4 when then
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switches to rocket mode and can fly
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into space for up to 800 kilometers 500
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miles above the earth. It would then
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return to the Earth's atmosphere and
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land as normal air-breathing plane to be
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checked, refueled and ready for launch.
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Because it uses more efficient engines
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and the lift of the wings it would use
8:46
only 20% of the fuel compared
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to a conventional rocket. It would still
8:50
need to bring it oxidizer for the rocket
8:53
portion of the journey but a lot less
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that will be required for a normal
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rocket. This allows for a larger payload
8:59
when compared to the total weight around
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5.5% compared to the shuttles 1.3%.
9:05
Unmanned flight test of the Skylon
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could be happening by 2025, if all goes
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well but a
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potentially large flying in ointment is the
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recent advances in reusable rockets like
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SpaceX Falcon f9r and the Blue Origin
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New Shepherd. These could make the
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development costs to the Skylon
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expensive for satellite deployment and
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supplying the International Space
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Station. One thing which could come out
9:33
though, is a rocket less version of the
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SABRE engine which could make hypersonic
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air travel more a viable option than using
9:42
a scramjet.
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Only time will tell but this is an
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exciting time for both the future of air
9:48
and space travel, so we may yet see the
9:51
plane that can fly to space. So as always
9:54
thanks for watching and please subscribe,
9:57
rate and share.
— end of transcript —
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