There are no jet engine VTOL (VTOL = Vertical Takeoff And Landing) aircrafts for civil aviation. This is because there are no adequate VTOL jet engines. Let's design one.
Back in the 1960's Rolls-Royce designed the jet engine RB162 as a VTOL engine. The thrust-to-weight ratio was 18.75:1, it was designed based on traditional get engine design and it was newer used.>
My idea here is to create a VTOL engine that has very high thrust-to-weight ratio. Ways to do that is to use simpler structure and composite materials. Also the fact that a VTOL engine would be used much shorter time than the main jet engine, gives possibility to use more changeable components.
Another requirement is to make the engine short in order to make it possible fit to aircrafts wings.
Here you can see three candidates for the VTOL engine. I have no idea if any of the candidates is viable. In the sketches black means static structure and red means rotating component. Green means a bearing and yellow a seal. Blue arrow means cool air and red arrow hot exhaust. Dotted lines means that the structure has holes. All designs have air intake from below of the compressor. Air is delivered through pipes from the aircrafts air intake. The candidates has no central shaft, the compressor and the turbine are connected to same rotatig component. My estimate for the thrust-to-weight is somewhere between 50:1 - 100:1.
First candidate has only one bearingpoint. This could work if the rotor would be stiff enough.
Second candidate has another bearingpoint. This makes the structure more robust also more complex. This means more weight.
Third candidate has rotating exhaust exit with rocket engine design. Propably makes no sense.
Fourth candidate has a cylinder shape burner.
Fifth candidate has a rocket shape burner and there is no nozzle.
Based on previous estimations I make an assumption that it is possible to create a jet engine with following specifications:
- thrust 8000 N (1800 lbf)
- weight 16 kg (35 lb), the thrust-to-weight ratio is 50
- height 300 mm (12")
- diameter 400 mm (16")
These kind of jet engines shouldn't be used in a consumer market because of the pollution. Small commercial jet planes or emergency aircrafts would be perfect targets. I am quite sure that the generals would use them in military aircrafts too.