Pulse Jet rocke...??? crazy of brillant...???

[BigtonyICU]

Hi Guys,

I've been building Hi power (G-L class) solid and hybrid rockets for the past 12 years. I also have a BA in Mechanical Engineering.

I was looking at the post on rocket racers, where someone mentions that there missing the boat on Pulse jet racers... that go me thinking...

I'm not extremely familiar with Pulse jet but… a pulse jet is essentially a combustion chamber with 2/3 of a nozzle (a convergence and the throat… A long, long throat) a valve is added to the combustion chamber on the opposite side of nozzle, fuel is dumped in, ignition is provided, the detonation slams the valve shut, forcing the hot gases out the nozzle throat, once the pressure drop the valve reopen move air comes in more gas is added, ignition, detonation… and the process continues and voila you got trust. (Sorry to all the pulse jet expert out there for the crude explanation, but I’m a rocket guy, not a pulse guy)

Now this is where I get thinking… I would slightly modify the nozzle by adding a divergence. We could add a buck head in front of the valve voila… you’ve now got a rocket engine… Yes I know what’s the point…

Orbital Space or long range Sub Orbital travel. This would allow a great reduction in the amount on oxidizer required at take off. Reducing the weight… reducing the size… reducing the COST of Hypersonic Travel…


Now tell me what you think. I’m currently 3D CADing a crude design in CATIA to see what the simulation say.

[MJD]

For a rocket to work with any reasonable efficiency, chamber pressures start at several hundred psi. A rocket motor working at 500psi (low) with a 1.25" throat and a thrust coefficient of about 1.4 typical at that pressure would produce 859 pounds of thrust. And the chamber temperatures would destroy the motor unless regenerative cooling were used.

Rather than trying to make one type of motor do two things, it is usually better to make it do one thing really well. This is why there is a lot of interest in aircraft launched rockets for small satellite payloads to LEO. The aircraft does an effiecient job of getting the rocket up out of the soupy lower atmospheric air.

MJD