Rocket car

Care to explain the difference in detail? I'm a car enthusiast, not an automtive or jet/rocket propulsion expert?

It was ye olde jet car thats been on all the drag strips for 25 years.

Yeah, but I wanted Ken to explain the difference between Jet and rocket.

Probably can't. Anything that can go from 0-270 in 7 and a bit secs can hardly be classed as "tame" whether rocket or jet powered !

Mike P

Its a low bypass turbojet engine. With afterburner.

I don't know for sure, but my guess would be that jet involves some sort of spinning turbine that sucks air in from the front and pushes it out through the back, and rocket involves some sort of chemical reaction/explosion that creates the force from within, so to speak, and expels great amounts of air out the back to power the thing. This is complete guesswork, mind.....

Jet = jet engine, so some sort of turbojet or pulse jet, which is relatively OK as you can turn it on and off happily. A rocket motor on the other hand, can be a complete PITA as if it's solid fuel, once it's going, it's going until it's gone out.

Not quite true.

Solid fuel like firework rockets are like that, as are the shuttles boosters. But just like the shuttle main engines most rocket engines can be both shut of or throttled faster than a turbojet can. Turbines take time to spool up and down. Liquid fueled (usually kerosene/oxygen or hydrogen oxygen) can be shut off or throttled. As can the latest breed used in drag racing and in the recent X prize rocket. They use a plastic or rubber for the fuel and use nitrous oxide as the oxydiser via the solenoid valves which can be pulsed for power control or shut off for instant stop.

That the thing that always seemed to be like a big Hoover?

Aren't they hybrid rockets? A combination of solid fuel and liquid oxidiser. Rather than the traditional solid fuel rockets that contain the oxidiser in a solid state within the fuel.

Yep. But the fuel is a solid. Not a monopropellent like a firework. Theres one on sky right now.

I know a bit about them because they require Nitrous solenoids etc. The rocketry brigade and drag car guys with them email and ask questions about BIG nitrous solenoids!

They are solid plastic or rubber or a mix sat in a strong tube with a nozzle at one end and a nitrous injector at the other the solid fuel has a drilling down the centre and the gas goes down the middle oxydising the solid fuel on the way. And its controllable via pulsing the solenoid like a fuel injector. Just change the Pulse width duty.

Does it have an Inconel exhaust manifold?

No but it is based on the golf floorpan.

No its stainless. It does have inconel combustion chamber walls though! Almost all turbojets do. Even my 16lb thrust "toy" one on my desk.

What about a pulse jet. I thought that had no moving parts. Just a flow of air, a fuel source ijected into the airstream and a spark to fire it?

Fireworks are a solid bipropellant, a mixture of fuel and oxidiser like gunpowder. Monopropellants use only a single chemical, typically hydrazine or isopropyl nitrate.

I think the main difference is in where the oxidiser comes from, jets primarily use atmospheric oxygen where as a rocket has it's own supply.

There are jets and rockets both with and without moving parts. The crucial difference is that jets breathe air, rockets bring everything they need along with them.

The dragster people have (had) two, one powered by an Orpheus turbojet, the other by a Viper turbojet. Both of these are '50s vintage designs, the Viper (used in the Jet Provost) of about 2,500lb thrust and the Orpheus (used in the Red Arrows' Folland Gnats) of about 4,500 lb thrust. I think it was the Orpheus engined car that crashed.