WEBVTT 00:00.109 --> 00:03.470 The XC 142 is in the museum's Global 00:03.480 --> 00:06.750 Reach gallery . And it tested another 00:06.760 --> 00:08.816 form of vertical takeoff and landing 00:08.816 --> 00:11.560 technology called tilt wings and tilt 00:11.569 --> 00:13.402 wings , operate with the engines 00:13.402 --> 00:15.529 attached to the wings and the entire 00:15.539 --> 00:19.469 wing goes vertical . And the XC 142 00:19.479 --> 00:21.920 was actually very successful in testing , 00:22.170 --> 00:23.837 but it wasn't bought and made 00:23.837 --> 00:25.920 operational . And it's a great 00:25.930 --> 00:28.110 illustration of the problem that we 00:28.120 --> 00:31.100 face called the Valley of Death . And 00:31.110 --> 00:33.520 that's where there's a system that 00:33.529 --> 00:36.520 works well and test , but ultimately is 00:36.529 --> 00:39.240 not bought by the acquirer or fielded 00:39.250 --> 00:42.310 by the warfighter . And A RL has 00:42.319 --> 00:44.939 different means that we're trying to 00:44.950 --> 00:47.061 prevent the valley of death problem . 00:47.061 --> 00:49.228 One of those is through the integrated 00:49.228 --> 00:51.394 capabilities directorate where they're 00:51.394 --> 00:54.380 pairing warfighter , science and 00:54.389 --> 00:57.419 technology folks and acquirer to make 00:57.430 --> 00:59.263 sure that the systems that we're 00:59.263 --> 01:01.152 developing , the technology we're 01:01.152 --> 01:03.208 developing can be applied bought and 01:03.208 --> 01:06.319 fielded . This is a pulse detonation 01:06.330 --> 01:08.730 engine developed in FRL in the two 01:08.739 --> 01:11.959 thousands and it's pretty amazing . 01:11.970 --> 01:14.137 They're fairly simple engines but very 01:14.137 --> 01:16.519 difficult to control . Uh Typical 01:16.529 --> 01:18.140 engine uses something called 01:18.140 --> 01:20.029 deflagration , this actually used 01:20.029 --> 01:22.239 detonation or basically a series of 01:22.250 --> 01:25.629 controlled explosions and PDES 01:25.639 --> 01:29.599 are simpler and fuel efficient but 01:29.610 --> 01:31.943 again , very difficult to develop . Now , 01:31.943 --> 01:35.080 this particular PDEE used a standard 01:35.089 --> 01:38.879 car engine block and it was used 01:38.889 --> 01:41.489 to power the first airborne aircraft to 01:41.500 --> 01:44.269 use a PDE . Now there's parallel 01:44.279 --> 01:47.029 technology to pulse detonation called 01:47.040 --> 01:49.830 rotating detonation engines or R DS . 01:50.180 --> 01:53.480 And both P DS and R DS are being 01:53.489 --> 01:57.029 developed in a FRL . Today , we're at 01:57.040 --> 02:00.339 the C 141 star lifter and this was an 02:00.349 --> 02:02.769 important air force strategic airlifter 02:02.779 --> 02:05.339 used in the 19 sixties all the way into 02:05.349 --> 02:07.460 the 19 nineties and even into the two 02:07.460 --> 02:10.419 thousands . And the C 141 was powered 02:10.429 --> 02:13.619 by low bypass turbo fans . And 02:13.630 --> 02:15.686 basically , that just means that the 02:15.686 --> 02:17.630 volume of air traveling around the 02:17.630 --> 02:19.741 engine through the fan and around the 02:19.741 --> 02:21.720 engine was not a very high ratio 02:21.729 --> 02:23.673 compared to the air that was going 02:23.673 --> 02:25.896 through the engine itself . There was a 02:25.896 --> 02:28.580 huge leap forward with the development 02:28.589 --> 02:31.500 of the high bypass turbo fan . And we 02:31.509 --> 02:33.120 have the very first one used 02:33.120 --> 02:36.800 operationally and produced in the T 39 02:36.809 --> 02:39.490 high bypass turbo fan right behind me 02:39.500 --> 02:41.667 here . And this large structure at the 02:41.667 --> 02:45.449 front is the fan and that's a 02:45.460 --> 02:47.639 key part of a turbo fan . You can see 02:47.649 --> 02:49.910 it's huge . And the reason why it's so 02:49.919 --> 02:53.220 big is because actually for every part 02:53.229 --> 02:55.396 of air that goes through this engine , 02:55.550 --> 02:58.679 eight parts go past the engine . So all 02:58.690 --> 03:00.912 the air goes through the fan , but much 03:00.912 --> 03:03.410 of the air actually bypasses the engine 03:03.419 --> 03:05.910 itself . Hence the name high bypass 03:05.919 --> 03:09.419 turbo fan , high bypass turbo fans have 03:09.429 --> 03:12.440 unparalleled fuel efficiency compared 03:12.449 --> 03:14.671 to other types of turbine engines . And 03:14.671 --> 03:16.979 in fact , these TF 39 s are the reason 03:16.990 --> 03:19.779 why the C five , the huge galaxy 03:19.789 --> 03:23.690 strategic airlifter was possible and 03:23.699 --> 03:26.710 commercial versions of this TF 39 have 03:26.720 --> 03:29.309 been used on large airliners even to 03:29.320 --> 03:31.320 this day . So chances are if you've 03:31.320 --> 03:33.369 flown on a big airliner , it was 03:33.380 --> 03:35.436 powered by the commercial version of 03:35.436 --> 03:37.979 this TF 39 . So where are the labs in 03:37.990 --> 03:40.059 this ? Well , the labs champion this 03:40.070 --> 03:42.750 idea of creating a high bypass turbo 03:42.860 --> 03:44.979 fan . In the 19 sixties , a lot of 03:44.990 --> 03:47.046 people thought they weren't possible 03:47.046 --> 03:48.979 because high bypass turbo fans 03:48.990 --> 03:51.089 absolutely require higher heats , 03:51.100 --> 03:53.211 higher temperatures , which is a real 03:53.211 --> 03:55.529 materials and structure problem . Well , 03:55.539 --> 03:59.070 Cliff Sim Simpson , an Ira pioneering 03:59.080 --> 04:02.529 engineer in the labs developed scale 04:02.539 --> 04:05.160 models of turbo fans and then also the 04:05.169 --> 04:07.660 labs developed key cooling technology 04:07.669 --> 04:10.169 called film cooling which allowed the 04:10.179 --> 04:12.720 high heats required for the high bypass 04:12.729 --> 04:16.369 turbo fan . This concludes our tour of 04:16.380 --> 04:18.489 the National Museum of the US Air Force .