1 00:00:00,000 --> 00:00:03,209 Why can't we fly a plane into space 2 00:00:03,209 --> 00:00:05,939 what stops it from just flying higher and 3 00:00:05,940 --> 00:00:08,250 higher until it in space. 4 00:00:08,250 --> 00:00:10,559 well there are several issues but 5 00:00:10,558 --> 00:00:12,299 assuming we are in something like a 6 00:00:12,300 --> 00:00:14,969 normal jet airliner then one of the main 7 00:00:14,968 --> 00:00:18,059 problems is the air or lack of it as we 8 00:00:18,059 --> 00:00:19,500 get closer to space. 9 00:00:19,500 --> 00:00:22,230 a plane flies because it is propelled 10 00:00:22,230 --> 00:00:25,019 forward the wings which shaped to make 11 00:00:25,018 --> 00:00:27,268 the air flow faster of the top of them 12 00:00:27,268 --> 00:00:30,479 rather than the bottom generate lift as 13 00:00:30,480 --> 00:00:33,119 the plane goes faster the wings create 14 00:00:33,119 --> 00:00:36,119 more lists when the lift is greater than 15 00:00:36,119 --> 00:00:38,399 the weight to the plane it will climb into 16 00:00:38,399 --> 00:00:41,730 the air. As our playing climbs higher and 17 00:00:41,729 --> 00:00:43,619 higher into the atmosphere the air 18 00:00:43,619 --> 00:00:46,709 becomes less and less dense the plane to 19 00:00:46,710 --> 00:00:49,829 fly faster to create more iift until 20 00:00:49,829 --> 00:00:51,989 eventually it reaches an altitude where 21 00:00:51,988 --> 00:00:53,909 the engines either cease to function 22 00:00:53,909 --> 00:00:55,738 correctly because of the lack of oxygen 23 00:00:55,738 --> 00:00:59,820 or the air is too thin to create enough lift. 24 00:00:59,820 --> 00:01:02,520 Just as we need air to breathe then the 25 00:01:02,520 --> 00:01:05,159 engine need oxygen to burn to create 26 00:01:05,159 --> 00:01:07,680 thrust to propel the plane forward just 27 00:01:07,680 --> 00:01:09,479 engines however engines can work at higher 28 00:01:09,478 --> 00:01:11,728 altitudes than people. We humans have a 29 00:01:11,728 --> 00:01:14,640 limit about 8,000 meters or 26,000 feet 30 00:01:14,640 --> 00:01:17,368 above which is what climbers 31 00:01:17,368 --> 00:01:20,579 call the "Death Zone", this is where there 32 00:01:20,579 --> 00:01:22,739 is not enough oxygen for humans to 33 00:01:22,739 --> 00:01:26,339 survive for sustained period. The summit 34 00:01:26,340 --> 00:01:29,670 of Mount Everest is 29,000 feet high in 35 00:01:29,670 --> 00:01:31,530 the air density there is about 36 00:01:31,530 --> 00:01:34,530 33% of that at sea level. 37 00:01:34,530 --> 00:01:36,629 This means that with each breath you 38 00:01:36,629 --> 00:01:38,759 take you're only getting 39 00:01:38,759 --> 00:01:40,859 33% of the oxygen. If you want to 40 00:01:40,859 --> 00:01:43,679 stay at this altitude without additional 41 00:01:43,680 --> 00:01:45,750 oxygen you would suffer from a condition 42 00:01:45,750 --> 00:01:48,810 called hypoxia were due to a lack of 43 00:01:48,810 --> 00:01:51,570 oxygen to the body starts to slow shut 44 00:01:51,569 --> 00:01:53,609 down and die. 45 00:01:53,609 --> 00:01:57,930 At 12,000 meters or 40,000 feet which is 46 00:01:57,930 --> 00:01:59,640 the upper limit for most modern 47 00:01:59,640 --> 00:02:01,650 airliners the air density is about 48 00:02:01,650 --> 00:02:04,800 18% of that at sea level. If you 49 00:02:04,799 --> 00:02:06,629 were in a plane that had a rapid 50 00:02:06,629 --> 00:02:09,719 decompression at 40,000 feet you'll have 51 00:02:09,719 --> 00:02:13,020 about five maybe ten seconds to get your 52 00:02:13,020 --> 00:02:15,780 emergency oxygen mask on before you 53 00:02:15,780 --> 00:02:18,509 became unconscious. The highest flying 54 00:02:18,509 --> 00:02:21,269 jet plane in level flight was the 55 00:02:21,270 --> 00:02:24,150 Lockheed SR-71 blackbird with a height 56 00:02:24,150 --> 00:02:30,840 of 85,069 feet 42,929 meters 57 00:02:30,840 --> 00:02:35,039 and where the a density is just 2% of 58 00:02:35,039 --> 00:02:38,159 that sea level. At that height it's 59 00:02:38,159 --> 00:02:43,079 traveling at mach 3.2 or 2190 miles an 60 00:02:43,080 --> 00:02:47,040 hour. The SR-71 pilots had to wear a full 61 00:02:47,039 --> 00:02:49,799 pressure suit with its own oxygen supply 62 00:02:49,800 --> 00:02:52,469 in case of a cockpit decompression or 63 00:02:52,469 --> 00:02:55,289 emergency ejection and this was put to the 64 00:02:55,289 --> 00:02:58,949 test when you 1966 an SR-71 piloted by 65 00:02:58,949 --> 00:03:02,879 Bill Weaver disintegrated that mach 3.1 66 00:03:02,879 --> 00:03:06,599 at an altitude the 78,000 feet as it was 67 00:03:06,599 --> 00:03:08,579 performing a test flight to ironically 68 00:03:08,580 --> 00:03:11,549 optimizing performance. At that altitude 69 00:03:11,549 --> 00:03:14,250 your blood will boil in a similar way to 70 00:03:14,250 --> 00:03:16,169 when you open a bottle of fizzy drink as 71 00:03:16,169 --> 00:03:19,559 the nitrogen in your blood to the gas in 72 00:03:19,560 --> 00:03:21,959 the low-pressure atmosphere. The pressure 73 00:03:21,959 --> 00:03:24,269 suit work and Weaver survived the 74 00:03:24,269 --> 00:03:27,480 descent from 78,000 feet but tragically 75 00:03:27,479 --> 00:03:30,449 the navigator Jim's Zwayer died of a broken 76 00:03:30,449 --> 00:03:32,369 neck resulting from break of the 77 00:03:32,370 --> 00:03:34,860 plane. Now while you would think that the 78 00:03:34,860 --> 00:03:38,790 SR-71 soft to get into space you need to 79 00:03:38,789 --> 00:03:40,739 reach what is called "escape velocity" 80 00:03:40,739 --> 00:03:43,950 this is where you are traveling faster 81 00:03:43,949 --> 00:03:46,048 than gravity is pulling you back to work 82 00:03:46,049 --> 00:03:49,620 and that is 25,020 miles an 83 00:03:49,620 --> 00:03:53,330 hour or 40,270 km/h and 84 00:03:53,330 --> 00:03:54,830 and if that wasn't a problem there's 85 00:03:54,830 --> 00:03:57,080 also to recognized altitude at where 86 00:03:57,080 --> 00:03:59,510 space starts at 328,000 ft 87 00:03:59,509 --> 00:04:02,750 or 100,000 meters 88 00:04:02,750 --> 00:04:05,659 well over three times the 89 00:04:05,659 --> 00:04:09,560 highest flight of the SR-71. Normal jet 90 00:04:09,560 --> 00:04:12,020 engines like those in the SR-71 have a 91 00:04:12,020 --> 00:04:13,850 maximum air speed limits for around 92 00:04:13,849 --> 00:04:18,560 about Mach 3.5 or 2695 miles now beyond 93 00:04:18,560 --> 00:04:20,449 that the air pressure and temperature 94 00:04:20,449 --> 00:04:22,550 becomes too high for compresses and the 95 00:04:22,550 --> 00:04:25,129 engine to effectively. For hypersonic 96 00:04:25,129 --> 00:04:28,339 speeds, experimental unmanned aircraft 97 00:04:28,339 --> 00:04:32,119 like NASA X-43 use what is called a scramjet 98 00:04:32,120 --> 00:04:36,290 engine. The X-43 is currently the fastest 99 00:04:36,290 --> 00:04:38,840 free flying air-breathing aircraft in 100 00:04:38,839 --> 00:04:44,569 the world having flown at mach 9.6 or 7310 101 00:04:44,569 --> 00:04:47,480 miles an hour in November of 2004. 102 00:04:47,480 --> 00:04:50,569 Scramjets do away with the turbine 103 00:04:50,569 --> 00:04:52,490 compressors of the jet engine so they 104 00:04:52,490 --> 00:04:55,340 have no moving parts instead they use 105 00:04:55,339 --> 00:04:57,889 shock waves in the engine to compress 106 00:04:57,889 --> 00:05:00,709 the raise the temperature in the engine to 107 00:05:00,709 --> 00:05:03,560 burn fuel and create trust an in theory 108 00:05:03,560 --> 00:05:06,918 they can fly up to Mach 20 and possibly 109 00:05:06,918 --> 00:05:09,680 beyond. The problem with this is that 110 00:05:09,680 --> 00:05:12,230 they won't work at speeds of less than 111 00:05:12,230 --> 00:05:14,240 around Mach 5 so they have to be 112 00:05:14,240 --> 00:05:16,759 brought up to speed by rocket engine 113 00:05:16,759 --> 00:05:19,490 booster before they can operate, which is 114 00:05:19,490 --> 00:05:23,030 how NASA x43 worked. They also won't 115 00:05:23,029 --> 00:05:25,759 work in space because there is no air 116 00:05:25,759 --> 00:05:28,899 with oxygen in to combust the fuel 117 00:05:28,899 --> 00:05:31,179 So this why space vehicles are 118 00:05:31,180 --> 00:05:33,850 launched by Rockets. Rockets can have 119 00:05:33,850 --> 00:05:36,009 much more power and can operate from a 120 00:05:36,009 --> 00:05:39,490 speed of zero on the launchpad to Mach 33 and 121 00:05:39,490 --> 00:05:41,500 beyond which is the escape velocity of 122 00:05:41,500 --> 00:05:44,439 Earth. One of the earliest experimental 123 00:05:44,439 --> 00:05:47,500 space planes was the North American X-15 124 00:05:47,500 --> 00:05:51,430 which reached a height of 353,000 feet 125 00:05:51,430 --> 00:05:56,139 or 107,000 meters 1963 and was 126 00:05:56,139 --> 00:06:00,069 powered by a liquid rocket danger but it 127 00:06:00,069 --> 00:06:02,620 had to be carried up to 45,000 feet 128 00:06:02,620 --> 00:06:04,959 attached to the underside with B-52 129 00:06:04,959 --> 00:06:07,359 bomber before being released. Then of 130 00:06:07,360 --> 00:06:09,520 course we've had space shuttle the 131 00:06:09,519 --> 00:06:10,750 Soviet version of the Space Shuttle 132 00:06:10,750 --> 00:06:14,860 the "Buran", SpaceShipOne and the Boeing X-37, 133 00:06:14,860 --> 00:06:17,530 all of which were examples of space 134 00:06:17,529 --> 00:06:20,019 planes but we're really just rocket powered gliders. 135 00:06:20,019 --> 00:06:23,500 Rocket differ from Jets 136 00:06:23,500 --> 00:06:26,019 because they bring their own oxygen to 137 00:06:26,019 --> 00:06:28,089 burn the fuel and don't rely on the 138 00:06:28,089 --> 00:06:29,888 atmospheric oxygen. 139 00:06:29,889 --> 00:06:31,598 This means that they can working space 140 00:06:31,598 --> 00:06:34,509 equally as well as in the atmosphere. The 141 00:06:34,509 --> 00:06:36,519 problem with rockets is that because they 142 00:06:36,519 --> 00:06:38,829 need to bring the oxidizer with they makes 143 00:06:38,829 --> 00:06:41,199 them very heavily. Look at the space 144 00:06:41,199 --> 00:06:43,360 Shuttle for example, the external fuel 145 00:06:43,360 --> 00:06:46,629 and the tanks to hold it along with the two 146 00:06:46,629 --> 00:06:51,490 solid rocket boosters weighed 1,940 metric 147 00:06:51,490 --> 00:06:54,220 tonnes at liftoff and that's without the 148 00:06:54,220 --> 00:06:56,440 space shuttle. All of which has to be 149 00:06:56,439 --> 00:06:58,449 carried along with the shuttle to the 150 00:06:58,449 --> 00:07:00,189 edge of space where they are they 151 00:07:00,189 --> 00:07:03,699 jettisoned. The maximum payload the shuttle 152 00:07:03,699 --> 00:07:05,949 could deliver it into a low earth orbit was 153 00:07:05,949 --> 00:07:10,270 27.5 metric tons, which as a payload 154 00:07:10,269 --> 00:07:15,098 fraction is just 1.3% of the total 155 00:07:15,098 --> 00:07:16,709 take off weight. 156 00:07:16,709 --> 00:07:19,680 Rockets however can create huge amount 157 00:07:19,680 --> 00:07:21,810 of power, so they can achieve the 158 00:07:21,810 --> 00:07:24,180 speed that is need to escape the pull 159 00:07:24,180 --> 00:07:27,000 of gravity and go into orbit and Beyond. 160 00:07:27,000 --> 00:07:30,120 But what of the future, will we ever get 161 00:07:30,120 --> 00:07:32,160 planes that can take off from an 162 00:07:32,160 --> 00:07:35,040 aircraft runway, fly into space and then 163 00:07:35,040 --> 00:07:38,220 return back to a runway. There are 164 00:07:38,220 --> 00:07:40,620 still considerable technical issues to 165 00:07:40,620 --> 00:07:42,750 overcome but one design which looks 166 00:07:42,750 --> 00:07:47,069 promising is the Skylon. This is an SSTO 167 00:07:47,069 --> 00:07:50,040 or Single Stage To Orbit design meaning 168 00:07:50,040 --> 00:07:52,230 that unlike a rocket, it stays in one 169 00:07:52,230 --> 00:07:55,080 piece rather than having a separate main 170 00:07:55,079 --> 00:07:57,509 booster stage which detaches and return 171 00:07:57,509 --> 00:08:00,000 to Earth and then a smaller second stage 172 00:08:00,000 --> 00:08:02,490 which one goes on to orbit. The key 173 00:08:02,490 --> 00:08:05,819 technology makes Skylon work is the SABRE or 174 00:08:05,819 --> 00:08:08,370 Synergetic Air Breathing Rocket Engines. 175 00:08:08,370 --> 00:08:11,850 Now these are kind of hybrid jet rocket 176 00:08:11,850 --> 00:08:14,430 engine which can take off like a normal 177 00:08:14,430 --> 00:08:18,120 jet engine, breathe air upto 93,000 feet 178 00:08:18,120 --> 00:08:22,350 and at a speed up to Mach 5.4 when then 179 00:08:22,350 --> 00:08:24,840 switches to rocket mode and can fly 180 00:08:24,839 --> 00:08:28,799 into space for up to 800 kilometers 500 181 00:08:28,800 --> 00:08:31,800 miles above the earth. It would then 182 00:08:31,800 --> 00:08:34,350 return to the Earth's atmosphere and 183 00:08:34,350 --> 00:08:37,800 land as normal air-breathing plane to be 184 00:08:37,799 --> 00:08:40,019 checked, refueled and ready for launch. 185 00:08:40,019 --> 00:08:43,350 Because it uses more efficient engines 186 00:08:43,350 --> 00:08:46,320 and the lift of the wings it would use 187 00:08:46,320 --> 00:08:48,690 only 20% of the fuel compared 188 00:08:48,690 --> 00:08:50,970 to a conventional rocket. It would still 189 00:08:50,970 --> 00:08:53,009 need to bring it oxidizer for the rocket 190 00:08:53,009 --> 00:08:55,319 portion of the journey but a lot less 191 00:08:55,320 --> 00:08:56,850 that will be required for a normal 192 00:08:56,850 --> 00:08:59,700 rocket. This allows for a larger payload 193 00:08:59,700 --> 00:09:01,800 when compared to the total weight around 194 00:09:01,799 --> 00:09:05,549 5.5% compared to the shuttles 1.3%. 195 00:09:05,549 --> 00:09:07,889 Unmanned flight test of the Skylon 196 00:09:07,889 --> 00:09:11,340 could be happening by 2025, if all goes 197 00:09:11,340 --> 00:09:13,300 well but a 198 00:09:13,299 --> 00:09:15,579 potentially large flying in ointment is the 199 00:09:15,580 --> 00:09:18,790 recent advances in reusable rockets like 200 00:09:18,789 --> 00:09:22,208 SpaceX Falcon f9r and the Blue Origin 201 00:09:22,208 --> 00:09:24,579 New Shepherd. These could make the 202 00:09:24,580 --> 00:09:26,410 development costs to the Skylon 203 00:09:26,409 --> 00:09:28,929 expensive for satellite deployment and 204 00:09:28,929 --> 00:09:30,309 supplying the International Space 205 00:09:30,309 --> 00:09:33,189 Station. One thing which could come out 206 00:09:33,190 --> 00:09:35,950 though, is a rocket less version of the 207 00:09:35,950 --> 00:09:39,100 SABRE engine which could make hypersonic 208 00:09:39,100 --> 00:09:42,129 air travel more a viable option than using 209 00:09:42,129 --> 00:09:43,778 a scramjet. 210 00:09:43,778 --> 00:09:46,120 Only time will tell but this is an 211 00:09:46,120 --> 00:09:48,310 exciting time for both the future of air 212 00:09:48,309 --> 00:09:51,639 and space travel, so we may yet see the 213 00:09:51,639 --> 00:09:54,879 plane that can fly to space. So as always 214 00:09:54,879 --> 00:09:57,610 thanks for watching and please subscribe, 215 00:09:57,610 --> 00:10:04,680 rate and share.