Some History on Motorjets

[larry cottrill]

Most or many of you may have seen this, but I thought it had some pretty interesting historical mentions, along with drawings, etc. Also, the guy has built a little 'thrown together' motorjet powered from the nearest wall outlet:

http://www.angelfire.com/art/jetengine/

One thing he does a good job of bringing out is that usually, the motorjet is essentially a ducted fan with afterburner.

I still think this is a good idea for something to try - especially now that powerful, extremely efficient flyable electric ducted fan systems are easily obtained. Of course, you can still set up gas-powered ones, as well.

L Cottrill

[Najm]

Is the SR-71's engine some type of motor(turbine) jet?
I saw long way back on Discovery that it generated 70% of its thrust just from the compressor's air, the other 30% was from the turbine's exhuast.

[Bruno Ogorelec]

No, it is a hybrid engine; a combination of turbojet and ramjet. It has an interesting history -- it may actually have been developed in its initial form by the French Nord Aviation. There's a conspiracy theory backed by some good data saying that the research was done in France with US money. There may have been some internal political reasons for the move, but it was partly a bid to sidetrack the Russians. Once the engine was proven to work well enough in practice, it was tested on a missile before finally going into the proper airframe.

[Zippiot]

i deem this the motorpropjetplane:

http://en.wikipedia.org/wiki/Mikoyan-Gu ... 50_%28N%29

freaky cool motorjet designed into a plane:

http://history.nasa.gov/SP-4305/p237a.jpg


and i got an idea that might help the motorjet...
make the ducts retractable, and add one that will lead straight into the combustion chamber. see what i mean? its just a motor assisted ramjet i guess, but once up to speed, switch the ducts turn off the compressor and there you have a running ramjet.

i once saw a great picture of a fighter jet from ww2 that was motorjet powered, still looking for it

[Zippiot]

i was under the impression that these were rocket powered...

http://tanks45.tripod.com/Jets45/Histor ... Ohka22.htm

guess not, now that i get a closer look at it. maybe 2 versions exist

[Zippiot]

here is the best looking design i have seen yet!

http://www.rescyou.com/motojet/

if only the flames werent computer simulated...

this looks like a good challenge, who is up to it, making a small motorjet that can be fitted to an r/c aircraft?

[Bruno Ogorelec]

here is the best looking design i have seen yet!

http://www.rescyou.com/motojet/

if only the flames werent computer simulated...

this looks like a good challenge, who is up to it, making a small motorjet that can be fitted to an r/c aircraft?

Ah, that would be our friend Shane, the intrepid oil well fire fighter. He has not been around in years. He never did anything by halves, as far as I can remember. He has always been quite fascinated by motorjets. (Or thermojets, as they also used to be called. We now use 'thermojet' for a particular sort of pulsejet.)

[Bruno Ogorelec]

If someone were to build something like a motorjet now, I'd suggest a completely different approach.

I'd take a Wankel engine off an old Mazda RX-7 or something and use it as the jet engine combustion chamber, with some whopping big turbocharger to provide the compressor part and the turbine part

The mean effective pressure will be very high without the stack of compressor wheels that the turbojets usually have.

Also, everything will be off the shelf. No special complex parts to design and make, just a few brackets and thingies.

You can remove a lot of unnecessary gear from the Wankel, probably also machine a lot of steel and alloy off that the engine, as it won't need much of the cast webbing etc. if it's just used as a combustion chamber.

The reason I'm talking Wankel is its high firing frequency. It runs at very high RPM and a two-chamber engine has six bangs per revolution, meaning that it will work at 400 HZ at 8000 RPM, which should be a cinch for Mazda. That means a very smooth production of driving gas, almost as if you had a constant pressure combustor. Turbines like their incoming gas smooth.

You can easily add an afterburner, too.

Or you could gear the Wankel and the turbocharger together and get a turboshaft engine.

[Zippiot]

lets say i dont want to deal with the rx-7's ill fated wankel, and dont have the money for the rx-8's renesis...

i have seen many 125-250 cc single cylinder motors that can reach up to 25,000 rpm. in a ducted fan type thing i am sure that 25000 rpm will be usefull for something...

if we had a larger scale application i would actually go electric. we have made massive improvements in electric motors, we have electric go karts that run up to 150 mph in 15 seconds, with a 120 hp 59,000 rpm electric motor. a recharging system would be needed, possibly one can be shoved into the combustion chamber...

[multispool]

Most or many of you may have seen this, but I thought it had some pretty interesting historical mentions, along with drawings, etc. Also, the guy has built a little 'thrown together' motorjet powered from the nearest wall outlet:

http://www.angelfire.com/art/jetengine/

One thing he does a good job of bringing out is that usually, the motorjet is essentially a ducted fan with afterburner.

Most or many of you may have seen this, but I thought it had some pretty interesting historical mentions, along with drawings, etc. Also, the guy has built a little 'thrown together' motorjet powered from the nearest wall outlet:

That site has mention of Henri Coanda as the father of the jet engine. While history circa 1911 can become a little vague over time. I did some research into this a few years ago and came up with some quite opposite answers:

Mainly, Coanda claimed that he had taken off and crashed shortly afterwards when the fuselage caught on fire. There were no witnesses to this and was probably just wishfull thinking on his part, as was his claim of 200kg traction.
The wing and fusellage covering was plywood, not metal

Alfred Bodemer at the Musee de l'air studied the design and concluded that the compression ratio of the compressor could hardly have been more than 1:1 thus providing inadequate power for any kind of take off.

The principle of operation was to use the engine to drive the compressor and use this airflow to mix with the engine exhaust gasses within the fuselage, raising it's temperature before discharging it out a hole in the tail.

Most importantly, No aditional fuel was injected or burned so could not really be classed as a gas turbine fore-runner.

A fascinating man and machine never the less!

[Zippiot]

it never flew you say, this i must research. if true many online fact databases are incorrect. but the internet is full of falsified things...

i have a speed 10 electric airplane motor (its small but very powerful and fast) and i am starting to draw up plans to turn it into a motorjet. i am not sure if i will place the motor inside the jet assembly (like the image i linked to earlier) or whether it will be in the plane assembly with air ducting into it.

the only issue is fuel... i will most likely have to get it running really lean at full throttle, because i dont really want to deal with throttle gas and electric...

i will lose out on top end power, but simplicity is key...as these motors seemed to be abandoned after ww2...

[Zippiot]

http://www.aerospaceweb.org/question/hi ... 0144.shtml

i found the thermojet powered aircraft i was looking for, scroll down the page a little it is there. looks quite large compared to other fighters of the time.

also click on some of the links at the bottom of the page, many cool ideas for airplanes and such down there