Why are scalemodel ramjets not used on rcplanes?

[Albinonutte2012]

They are simple to operate, with the only moving part needed being a fuel pump. Their construction might be somewhat chellenging for your average hobbyist but with economies of scale, I could see it making sense for a company. Scaling it down should also not really be a problem, seeing the size of some ramjets used in helicopters like the hiller. At this scale they would not really be the most efficient but if you are into rcplames do you really mind? It is quite expencive already. If the rocketboosters are strong enough, these planes could have some redicules performance compared to your regular or even more expencive rc jetplanes. If designed by a determend group with enough time like some university students, they would be capable of even breaking the soundbarrier. The most obvious problem however, atleast for most countries outside the US would be the necessary rocketbooster. While they would probably be illegal everywhere else, in the US it could work, I think. Please let me know your thoughts, I am very interested.

 

[Byeman]

they have a high minimum starting speed

 

[southwestforests]

Maintaining awareness of the model would be an issue.
Ramjets require high speeds to get the proper airflow through the engine.
There are already jet turbine powered models capable of 200 mph, 321.8 kph.
That is moving a mile, 1600m, every 20 seconds or so.
Who could even see the model when it is 40 seconds away from them?

And then there's the government and how it likes to regulate and control things.
If you are going to be flying RC planes, or drones too, weighing over half a pound then you need to register with the Federal Aviation Administration.

The most obvious problem however, atleast for most countries outside the US would be the necessary rocketbooster.

Rocket booster mentioned would probably be entering the realm of mid-power and high-power rocketry.
Those require a certification process to get approved to do them.
And the the government kind of gets interested in and involved when people fly them,

https://www.faa.gov/air_traffic/publications/atpubs/pham_html/chap31_section_1.html

https://www.faa.gov/space/licenses/amateur-rockets

 

[Justo Miranda]

It has been tried on many occasions, mainly with scale replicas of the V-1 missile, but the vibration of the pulsejet is destructive to the airframe and magnetizes the electronic equipment if it is not protected. In addition, when the missile flies, it is very dangerous for spectators.

View: https://www.youtube.com/watch?v=aGdxROaDI9A


https://theaviationgeekclub.com/imp...el-performing-classic-fighters-omaka-airshow/

View: https://www.youtube.com/watch?v=CJNhoSXvxYs

 

[Jemiba]

As Justo already pointed out, pulsejets actually are used on RC-planes. If you want to see more of them, keep an eye on the little town Rothenburg (but Rothenburg in the Oberlausitz, not at the Tauber !), especially on the "Luftfahrtechnische Museum" (aeronautical technical museum) there. Here's a link to the report about last years event there :

https://days-of-speed-and-thunder.de/rekordzahl-an-piloten-beim-16-pulsotreffen-in-rothenburg/

The name is motto, and this probably is a reason, that this type of propulsion isn't as widespread, as electric propulsion. And as southwestforests pointed out, you need a large area, as most of those models are really fast.
Attached are some photos I took at this event in 2015, and no, not every vehicle powered by a pulsejet there was flying ...

 

[Arjen]

That last one, did anyone ever start the engine?

 

[Albinonutte2012]

As Justo already pointed out, pulsejets actually are used on RC-planes. If you want to see more of them, keep an eye on the little town Rothenburg (but Rothenburg in the Oberlausitz, not at the Tauber !), especially on the "Luftfahrtechnische Museum" (aeronautical technical museum) there. Here's a link to the report about last years event there :

https://days-of-speed-and-thunder.de/rekordzahl-an-piloten-beim-16-pulsotreffen-in-rothenburg/

The name is motto, and this probably is a reason, that this type of propulsion isn't as widespread, as electric propulsion. And as southwestforests pointed out, you need a large area, as most of those models are really fast.
Attached are some photos I took at this event in 2015, and no, not every vehicle powered by a pulsejet there was flying ...

View attachment 746817View attachment 746818

View attachment 746819

View attachment 746820
View attachment 746821

Thanks for the tip. I will propably have to visit them at some point. Those are still different from Ramjets, though somewhat similar. I think ramjets are just fascinating because of their increadible mechanical simplicity.