Name: 垂直起飞的现实生活科幻（The Real Life Sci-Fi of Vertical Take-Off Planes）
Uploaded: 2021-06-01T09:32:16.000Z
Duration: 8 min 41 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

This episode of Real Engineering is brought to you by Brilliant.org a problem solving

關係子句

website that helps you think like an engineer.

The sight of a 9.4 tonne plane slowly rise off the ground, balancing precariously on

4 columns of air over the rough water of Galway bay, is the closest to sci-fi alien technology

An inspiring sight that seeded an obsession with aviation technology.

The harrier was the culmination of decades of bizarre experimentation to eliminate the

planes greatest weakness, it's need for a runway to both land and takeoff.

This fascinating technology has one of the richest histories in aviation with roots in

both the lunar lander and outlandish WW2 era German sketches.

Both the Allies and the Germans used helicopters and autogyros during this period, but using

a rotor for both lift and thrust inherently trades off speed.

The German's dreamed of a plane capable of taking off from anywhere, eliminating the

need for tactically vulnerable airstrips, without sacrificing speed or dogfight capabilities.

Inspired by their ballistic missile program, which still lacked effective guidance programs

to accurate target allied aircraft, Erich Bachem developed the tail-sitting rocket powered

BP-349, which would allow the pilot to take control of the plane in it's final stages

of flight to guide it to it's target and unleash it's barrage of smaller rockets

The only manned test of this aircraft resulted in the death of the test pilot and the idea

was abandoned, but that didn't stopped the Germans in their pursuit of VTOL aircraft.

Next up was an even more bizarre tail sitting aircraft that featured 3 giant propellor blades

each powered by ram-jets at their tips, this would function similar to a helicopter for

take off and then transition to forward flight and use the blades like a giant propellor,

but it would require a nose-up position to achieve adequate lift, as it didn't have

Unsurprisingly this didn't make it passed basic wind tunnel testing, but could well

have inspired the Lockheed XFV and Convair XFV Pogo planes in the 1950s which used massive

The Lockheed version only ever managed to hover for a brief moment while transitioning

from horizontal flight to an upwards vertical flight, but the Convair XFV Pogo flown by

Lieutenant Colonel James Coleman became the first aircraft in history to successful fly

in both forward aerodynamic flight and in hover.

Ultimately both planes were cancelled due the difficulty in flying them, and their lack

Engines for propellor driven aircraft were simply not powerful enough yet.

To achieve necessary lift the rotors would need to increase velocity or diameter, which

would decrease the max horizontal speed of the aircraft as the tip-speeds of the blades

would rise, meaning the tips of the blades could easily break the sound barrier and cause

This problem and how the incredibly versatile V-22 Osprey solved it needs a video by itself

to explain the nuanced design of helicopters and their speed limits, but for now you will

just need to trust me that it's a difficult problem to solve.

And with the advent of powerful jet-engines, the problem was largely solved without the

The first craft to use jet propulsion for vertical lift was the Rolls-Royce Thrust Measuring

Rig, aptly nicknamed the flying bedstead, for it's obvious departure from the bird

This configuration largely influenced the design of the Lunar Lander training vehicle

that NASA developed for Neil Armstrong and other astronauts to practice with.

They mounted the engine on a gimbal to ensure it's thrust always pointed directly downwards

and only provided enough lift to simulate the moon's gravity, while hydrogen peroxide

Neil Armstrong attributed the success of his difficult landing on the moon to this ingenious

The lessons learned through early research craft like these provided Rolls-Royce with

the knowledge required to develop the Rolls-Royce Pegasus engine, which powers the Harrier.

This engine needed to have enough thrust to lift the entire weight of the plane, the designers

of the plane made this job easier by utilizing carbon-fibre composites for much aircrafts

structures to save weight, making the Harrier one of the first planes to use these materials.

Yet the job of designing a single engine capable of providing enough vertical thrust was still

difficult, and the resulting engine is pretty unique as a result.

The engine is similar to a traditional jet engine in that it consists of a low pressure

compressor fan, a high pressure compressor, a combustion chamber, a high pressure turbine

Where it differs radically is the engine outlet is not one large opening, but split into four

where the first 2 nozzles duct some of the air coming from the low pressure compressor

and the final two duct air from the higher pressure turbines.

[2] Because the air bleeding from the low pressure

compressor system has less force than the high pressure nozzles, the low pressure nozzles

need to be placed further from the planes centre of gravity than the high pressure nozzles.

This balances the plane along the length of the plane, but in vertical take-off mode there

is no air-flowing over the wings to provide force for the control surfaces.

So the plane needs a way of controlling it's roll, pitch and yaw in vertical takeoff mode,

and so the plane features nozzles that bleed air from the engine on the nose, tail and

This control system is not as reliable as aerodynamic lift, which is largely self correcting

when disturbances occurs, although fighters tend to purposely decrease stability to increase

maneuverability, which requires a computer to constantly monitor, but the disturbances

due to ground effect from the air from it's own jet can cause oscillations that overwhelm

this control system, and with no accurate way of correcting them, they could grow until

the plane inverts and lands on the cockpit, which has killed pilots on several occasions.

So pilots often dropped the plane heavily from a few metres above the ground before

the oscillations could take hold, which obviously wasn't ideal for the landing gear [3]

The harrier was also disadvantaged to conventional aircraft as the vertical takeoff mode it was

severely limited in max take-off weight and burnt off much of it's fuel in this intensive

So most Harrier take offs take place only as partial vertical take-off,where the plane

would accelerate on the runway like a conventional plane to achieve some lift from the wings

and then angle the nozzles to achieve the final lift needed to safely take off on the

The plane could then land vertically without wasting as much fuel later on when the weight

of the aircraft had reduced through use of it's fuel and armaments.

This takes it's max take-off weight from 9,415 kg to 14,100 kg, which is still lackluster

when comparing to their fellow Marine aircraft like the F/A-18 hornet that has a max take-off

weight of 23,541 kg and a maximum speed of 1.8 compared to the harriers subsonic, 0.9.

Make it a much more capable attack platform, but the hornet is only capable of launching

from large carriers, whereas the Harrier can launch from amphibious assault ships like

The Harrier has even managed to land on a cargo ship when it's pilot lost radio contact