WEBVTT 00:00:00.000 --> 00:00:03.209 Why can't we fly a plane into space 00:00:03.209 --> 00:00:05.939 what stops it from just flying higher and 00:00:05.940 --> 00:00:08.250 higher until it in space. 00:00:08.250 --> 00:00:10.559 well there are several issues but 00:00:10.558 --> 00:00:12.299 assuming we are in something like a 00:00:12.300 --> 00:00:14.969 normal jet airliner then one of the main 00:00:14.968 --> 00:00:18.059 problems is the air or lack of it as we 00:00:18.059 --> 00:00:19.500 get closer to space. 00:00:19.500 --> 00:00:22.230 a plane flies because it is propelled 00:00:22.230 --> 00:00:25.019 forward the wings which shaped to make 00:00:25.018 --> 00:00:27.268 the air flow faster of the top of them 00:00:27.268 --> 00:00:30.479 rather than the bottom generate lift as 00:00:30.480 --> 00:00:33.119 the plane goes faster the wings create 00:00:33.119 --> 00:00:36.119 more lists when the lift is greater than 00:00:36.119 --> 00:00:38.399 the weight to the plane it will climb into 00:00:38.399 --> 00:00:41.730 the air. As our playing climbs higher and 00:00:41.729 --> 00:00:43.619 higher into the atmosphere the air 00:00:43.619 --> 00:00:46.709 becomes less and less dense the plane to 00:00:46.710 --> 00:00:49.829 fly faster to create more iift until 00:00:49.829 --> 00:00:51.989 eventually it reaches an altitude where 00:00:51.988 --> 00:00:53.909 the engines either cease to function 00:00:53.909 --> 00:00:55.738 correctly because of the lack of oxygen 00:00:55.738 --> 00:00:59.820 or the air is too thin to create enough lift. 00:00:59.820 --> 00:01:02.520 Just as we need air to breathe then the 00:01:02.520 --> 00:01:05.159 engine need oxygen to burn to create 00:01:05.159 --> 00:01:07.680 thrust to propel the plane forward just 00:01:07.680 --> 00:01:09.479 engines however engines can work at higher 00:01:09.478 --> 00:01:11.728 altitudes than people. We humans have a 00:01:11.728 --> 00:01:14.640 limit about 8,000 meters or 26,000 feet 00:01:14.640 --> 00:01:17.368 above which is what climbers 00:01:17.368 --> 00:01:20.579 call the "Death Zone", this is where there 00:01:20.579 --> 00:01:22.739 is not enough oxygen for humans to 00:01:22.739 --> 00:01:26.339 survive for sustained period. The summit 00:01:26.340 --> 00:01:29.670 of Mount Everest is 29,000 feet high in 00:01:29.670 --> 00:01:31.530 the air density there is about 00:01:31.530 --> 00:01:34.530 33% of that at sea level. 00:01:34.530 --> 00:01:36.629 This means that with each breath you 00:01:36.629 --> 00:01:38.759 take you're only getting 00:01:38.759 --> 00:01:40.859 33% of the oxygen. If you want to 00:01:40.859 --> 00:01:43.679 stay at this altitude without additional 00:01:43.680 --> 00:01:45.750 oxygen you would suffer from a condition 00:01:45.750 --> 00:01:48.810 called hypoxia were due to a lack of 00:01:48.810 --> 00:01:51.570 oxygen to the body starts to slow shut 00:01:51.569 --> 00:01:53.609 down and die. 00:01:53.609 --> 00:01:57.930 At 12,000 meters or 40,000 feet which is 00:01:57.930 --> 00:01:59.640 the upper limit for most modern 00:01:59.640 --> 00:02:01.650 airliners the air density is about 00:02:01.650 --> 00:02:04.800 18% of that at sea level. If you 00:02:04.799 --> 00:02:06.629 were in a plane that had a rapid 00:02:06.629 --> 00:02:09.719 decompression at 40,000 feet you'll have 00:02:09.719 --> 00:02:13.020 about five maybe ten seconds to get your 00:02:13.020 --> 00:02:15.780 emergency oxygen mask on before you 00:02:15.780 --> 00:02:18.509 became unconscious. The highest flying 00:02:18.509 --> 00:02:21.269 jet plane in level flight was the 00:02:21.270 --> 00:02:24.150 Lockheed SR-71 blackbird with a height 00:02:24.150 --> 00:02:30.840 of 85,069 feet 42,929 meters 00:02:30.840 --> 00:02:35.039 and where the a density is just 2% of 00:02:35.039 --> 00:02:38.159 that sea level. At that height it's 00:02:38.159 --> 00:02:43.079 traveling at mach 3.2 or 2190 miles an 00:02:43.080 --> 00:02:47.040 hour. The SR-71 pilots had to wear a full 00:02:47.039 --> 00:02:49.799 pressure suit with its own oxygen supply 00:02:49.800 --> 00:02:52.469 in case of a cockpit decompression or 00:02:52.469 --> 00:02:55.289 emergency ejection and this was put to the 00:02:55.289 --> 00:02:58.949 test when you 1966 an SR-71 piloted by 00:02:58.949 --> 00:03:02.879 Bill Weaver disintegrated that mach 3.1 00:03:02.879 --> 00:03:06.599 at an altitude the 78,000 feet as it was 00:03:06.599 --> 00:03:08.579 performing a test flight to ironically 00:03:08.580 --> 00:03:11.549 optimizing performance. At that altitude 00:03:11.549 --> 00:03:14.250 your blood will boil in a similar way to 00:03:14.250 --> 00:03:16.169 when you open a bottle of fizzy drink as 00:03:16.169 --> 00:03:19.559 the nitrogen in your blood to the gas in 00:03:19.560 --> 00:03:21.959 the low-pressure atmosphere. The pressure 00:03:21.959 --> 00:03:24.269 suit work and Weaver survived the 00:03:24.269 --> 00:03:27.480 descent from 78,000 feet but tragically 00:03:27.479 --> 00:03:30.449 the navigator Jim's Zwayer died of a broken 00:03:30.449 --> 00:03:32.369 neck resulting from break of the 00:03:32.370 --> 00:03:34.860 plane. Now while you would think that the 00:03:34.860 --> 00:03:38.790 SR-71 soft to get into space you need to 00:03:38.789 --> 00:03:40.739 reach what is called "escape velocity" 00:03:40.739 --> 00:03:43.950 this is where you are traveling faster 00:03:43.949 --> 00:03:46.048 than gravity is pulling you back to work 00:03:46.049 --> 00:03:49.620 and that is 25,020 miles an 00:03:49.620 --> 00:03:53.330 hour or 40,270 km/h and 00:03:53.330 --> 00:03:54.830 and if that wasn't a problem there's 00:03:54.830 --> 00:03:57.080 also to recognized altitude at where 00:03:57.080 --> 00:03:59.510 space starts at 328,000 ft 00:03:59.509 --> 00:04:02.750 or 100,000 meters 00:04:02.750 --> 00:04:05.659 well over three times the 00:04:05.659 --> 00:04:09.560 highest flight of the SR-71. Normal jet 00:04:09.560 --> 00:04:12.020 engines like those in the SR-71 have a 00:04:12.020 --> 00:04:13.850 maximum air speed limits for around 00:04:13.849 --> 00:04:18.560 about Mach 3.5 or 2695 miles now beyond 00:04:18.560 --> 00:04:20.449 that the air pressure and temperature 00:04:20.449 --> 00:04:22.550 becomes too high for compresses and the 00:04:22.550 --> 00:04:25.129 engine to effectively. For hypersonic 00:04:25.129 --> 00:04:28.339 speeds, experimental unmanned aircraft 00:04:28.339 --> 00:04:32.119 like NASA X-43 use what is called a scramjet 00:04:32.120 --> 00:04:36.290 engine. The X-43 is currently the fastest 00:04:36.290 --> 00:04:38.840 free flying air-breathing aircraft in 00:04:38.839 --> 00:04:44.569 the world having flown at mach 9.6 or 7310 00:04:44.569 --> 00:04:47.480 miles an hour in November of 2004. 00:04:47.480 --> 00:04:50.569 Scramjets do away with the turbine 00:04:50.569 --> 00:04:52.490 compressors of the jet engine so they 00:04:52.490 --> 00:04:55.340 have no moving parts instead they use 00:04:55.339 --> 00:04:57.889 shock waves in the engine to compress 00:04:57.889 --> 00:05:00.709 the raise the temperature in the engine to 00:05:00.709 --> 00:05:03.560 burn fuel and create trust an in theory 00:05:03.560 --> 00:05:06.918 they can fly up to Mach 20 and possibly 00:05:06.918 --> 00:05:09.680 beyond. The problem with this is that 00:05:09.680 --> 00:05:12.230 they won't work at speeds of less than 00:05:12.230 --> 00:05:14.240 around Mach 5 so they have to be 00:05:14.240 --> 00:05:16.759 brought up to speed by rocket engine 00:05:16.759 --> 00:05:19.490 booster before they can operate, which is 00:05:19.490 --> 00:05:23.030 how NASA x43 worked. They also won't 00:05:23.029 --> 00:05:25.759 work in space because there is no air 00:05:25.759 --> 00:05:28.899 with oxygen in to combust the fuel 00:05:28.899 --> 00:05:31.179 So this why space vehicles are 00:05:31.180 --> 00:05:33.850 launched by Rockets. Rockets can have 00:05:33.850 --> 00:05:36.009 much more power and can operate from a 00:05:36.009 --> 00:05:39.490 speed of zero on the launchpad to Mach 33 and 00:05:39.490 --> 00:05:41.500 beyond which is the escape velocity of 00:05:41.500 --> 00:05:44.439 Earth. One of the earliest experimental 00:05:44.439 --> 00:05:47.500 space planes was the North American X-15 00:05:47.500 --> 00:05:51.430 which reached a height of 353,000 feet 00:05:51.430 --> 00:05:56.139 or 107,000 meters 1963 and was 00:05:56.139 --> 00:06:00.069 powered by a liquid rocket danger but it 00:06:00.069 --> 00:06:02.620 had to be carried up to 45,000 feet 00:06:02.620 --> 00:06:04.959 attached to the underside with B-52 00:06:04.959 --> 00:06:07.359 bomber before being released. Then of 00:06:07.360 --> 00:06:09.520 course we've had space shuttle the 00:06:09.519 --> 00:06:10.750 Soviet version of the Space Shuttle 00:06:10.750 --> 00:06:14.860 the "Buran", SpaceShipOne and the Boeing X-37, 00:06:14.860 --> 00:06:17.530 all of which were examples of space 00:06:17.529 --> 00:06:20.019 planes but we're really just rocket powered gliders. 00:06:20.019 --> 00:06:23.500 Rocket differ from Jets 00:06:23.500 --> 00:06:26.019 because they bring their own oxygen to 00:06:26.019 --> 00:06:28.089 burn the fuel and don't rely on the 00:06:28.089 --> 00:06:29.888 atmospheric oxygen. 00:06:29.889 --> 00:06:31.598 This means that they can working space 00:06:31.598 --> 00:06:34.509 equally as well as in the atmosphere. The 00:06:34.509 --> 00:06:36.519 problem with rockets is that because they 00:06:36.519 --> 00:06:38.829 need to bring the oxidizer with they makes 00:06:38.829 --> 00:06:41.199 them very heavily. Look at the space 00:06:41.199 --> 00:06:43.360 Shuttle for example, the external fuel 00:06:43.360 --> 00:06:46.629 and the tanks to hold it along with the two 00:06:46.629 --> 00:06:51.490 solid rocket boosters weighed 1,940 metric 00:06:51.490 --> 00:06:54.220 tonnes at liftoff and that's without the 00:06:54.220 --> 00:06:56.440 space shuttle. All of which has to be 00:06:56.439 --> 00:06:58.449 carried along with the shuttle to the 00:06:58.449 --> 00:07:00.189 edge of space where they are they 00:07:00.189 --> 00:07:03.699 jettisoned. The maximum payload the shuttle 00:07:03.699 --> 00:07:05.949 could deliver it into a low earth orbit was 00:07:05.949 --> 00:07:10.270 27.5 metric tons, which as a payload 00:07:10.269 --> 00:07:15.098 fraction is just 1.3% of the total 00:07:15.098 --> 00:07:16.709 take off weight. 00:07:16.709 --> 00:07:19.680 Rockets however can create huge amount 00:07:19.680 --> 00:07:21.810 of power, so they can achieve the 00:07:21.810 --> 00:07:24.180 speed that is need to escape the pull 00:07:24.180 --> 00:07:27.000 of gravity and go into orbit and Beyond. 00:07:27.000 --> 00:07:30.120 But what of the future, will we ever get 00:07:30.120 --> 00:07:32.160 planes that can take off from an 00:07:32.160 --> 00:07:35.040 aircraft runway, fly into space and then 00:07:35.040 --> 00:07:38.220 return back to a runway. There are 00:07:38.220 --> 00:07:40.620 still considerable technical issues to 00:07:40.620 --> 00:07:42.750 overcome but one design which looks 00:07:42.750 --> 00:07:47.069 promising is the Skylon. This is an SSTO 00:07:47.069 --> 00:07:50.040 or Single Stage To Orbit design meaning 00:07:50.040 --> 00:07:52.230 that unlike a rocket, it stays in one 00:07:52.230 --> 00:07:55.080 piece rather than having a separate main 00:07:55.079 --> 00:07:57.509 booster stage which detaches and return 00:07:57.509 --> 00:08:00.000 to Earth and then a smaller second stage 00:08:00.000 --> 00:08:02.490 which one goes on to orbit. The key 00:08:02.490 --> 00:08:05.819 technology makes Skylon work is the SABRE or 00:08:05.819 --> 00:08:08.370 Synergetic Air Breathing Rocket Engines. 00:08:08.370 --> 00:08:11.850 Now these are kind of hybrid jet rocket 00:08:11.850 --> 00:08:14.430 engine which can take off like a normal 00:08:14.430 --> 00:08:18.120 jet engine, breathe air upto 93,000 feet 00:08:18.120 --> 00:08:22.350 and at a speed up to Mach 5.4 when then 00:08:22.350 --> 00:08:24.840 switches to rocket mode and can fly 00:08:24.839 --> 00:08:28.799 into space for up to 800 kilometers 500 00:08:28.800 --> 00:08:31.800 miles above the earth. It would then 00:08:31.800 --> 00:08:34.350 return to the Earth's atmosphere and 00:08:34.350 --> 00:08:37.800 land as normal air-breathing plane to be 00:08:37.799 --> 00:08:40.019 checked, refueled and ready for launch. 00:08:40.019 --> 00:08:43.350 Because it uses more efficient engines 00:08:43.350 --> 00:08:46.320 and the lift of the wings it would use 00:08:46.320 --> 00:08:48.690 only 20% of the fuel compared 00:08:48.690 --> 00:08:50.970 to a conventional rocket. It would still 00:08:50.970 --> 00:08:53.009 need to bring it oxidizer for the rocket 00:08:53.009 --> 00:08:55.319 portion of the journey but a lot less 00:08:55.320 --> 00:08:56.850 that will be required for a normal 00:08:56.850 --> 00:08:59.700 rocket. This allows for a larger payload 00:08:59.700 --> 00:09:01.800 when compared to the total weight around 00:09:01.799 --> 00:09:05.549 5.5% compared to the shuttles 1.3%. 00:09:05.549 --> 00:09:07.889 Unmanned flight test of the Skylon 00:09:07.889 --> 00:09:11.340 could be happening by 2025, if all goes 00:09:11.340 --> 00:09:13.300 well but a 00:09:13.299 --> 00:09:15.579 potentially large flying in ointment is the 00:09:15.580 --> 00:09:18.790 recent advances in reusable rockets like 00:09:18.789 --> 00:09:22.208 SpaceX Falcon f9r and the Blue Origin 00:09:22.208 --> 00:09:24.579 New Shepherd. These could make the 00:09:24.580 --> 00:09:26.410 development costs to the Skylon 00:09:26.409 --> 00:09:28.929 expensive for satellite deployment and 00:09:28.929 --> 00:09:30.309 supplying the International Space 00:09:30.309 --> 00:09:33.189 Station. One thing which could come out 00:09:33.190 --> 00:09:35.950 though, is a rocket less version of the 00:09:35.950 --> 00:09:39.100 SABRE engine which could make hypersonic 00:09:39.100 --> 00:09:42.129 air travel more a viable option than using 00:09:42.129 --> 00:09:43.778 a scramjet. 00:09:43.778 --> 00:09:46.120 Only time will tell but this is an 00:09:46.120 --> 00:09:48.310 exciting time for both the future of air 00:09:48.309 --> 00:09:51.639 and space travel, so we may yet see the 00:09:51.639 --> 00:09:54.879 plane that can fly to space. So as always 00:09:54.879 --> 00:09:57.610 thanks for watching and please subscribe, 00:09:57.610 --> 00:10:04.680 rate and share.