The video illustrates the only time this concept is any use, for speed on the flat.
Any gradient or headwind would bring it to a standstill.
The problem is the small area of thrust at the nozzle, the area of air it's pressing against being too small to realise useful power against any real resistance.
Earlier jet engines had the same problem with high load applications, until Pratt & Whitney invented the turbofan bypass engines for the Boeing 747, which greatly increased the area of thrust and the effectiveness of the central area of thrust.
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I'm not sticking up fot this method of propulsion, I think it's totally wrong and inefficient on this scale.
However, this has nothing to do with nozzle size. Nozzle size alone does not dictate how powerful these engines are or how much thrust they produce. In simple terms the engine or motor is producing a force which we term as thrust. In a jet engine thrust is produced by taking a volume of air and changing its velocity (speed) through the engine, or accelerating it. Force (or thrust) = mass (quantity of air) x acceleration (how much you speed up the airflow). So you can either (1) take a small quantity of air and accelerate it greatly or (2) take a large quantity of air and accelerate it more gently in order to produce exactly the same output in terms of thrust or force.
Both methods have advantages and disadvantages.
(1) usually results in the air and combustion products exiting the engine hot and at supersonic speeds. These are termed low by pass engines and tend to be used on military jets etc or where supersonic flight is desired. The engine also tends to be much smaller and compact for a given output which is good for military jets. However they are horrendously noisy. In the early days of commercial jet travel this type of engine was prevalent The P&W JT8D on 737s, 707s and 727s. The RR Conway on VC10s, RR Spey on the Trident, RR Olympus on Concord, all very loud and unacceptable for today's commercial flying.
(2) These are engines such as the RR RB211 series and more recently the Trent and GE CM56s. Instead of spitting out fast moving supersonic exhaust gasses, these engines utilise extra turbine stages to remove more energy from the exhaust gas. This results is slower, cooler and much more quiet emission. The additional energy extracted in the slowing and cooling phase is used to drive a large fan at the front. Just think of this as a multi bladed propeller encased within the engine. This fan moves a massive quantity of air but doesn't speed it up as much as in the case of (1). These engines are very quiet, almost inaudible on the ground when cruising at altitude. Perfect for civil aviation purposes.
The move to these physically larger engines was not anything to do with lack of thrust due to small nozzle areas, thrust was never a problem. It was the noise aspect and to propell a 747 with a low by pass engine would have created earth shattering noise levels making it a commercial failure. The high by pass engines which are on every commercial jet today are everything to do with noise and not thrust.
Just as an aside, I was at Bruntingthorpe in Northants last year for their Cold War Jets Day. They high speed taxi all sorts of relecs and chop the engine just as the nose wheel comes up in the hope they can stop before the end of the runway. The Lightnings (RR Avon engines with re-heat) where like nothing I've ever heard before. Being only 10 meters away wasn't probably the best plan. However, a VC10 went later on and my liver is still resonating from that. That noise does not belong on earth and to imagine it taking off from Heathrow on 09 across London is unthinkable. No wonder it was never very successful. Beutiful fast aircraft in its day, but far too noisy, hence the move to high by pass.
