Ducted Propulsion
 

You old timers, like me, may remember the single stage rocket that flew as a two stager, called the "Little Augie." It used the principle of 'ducted propulsion' to get the second stage to go higher. Question, I have not seen any more work done on this, or heard of it since the late sixties or early seventies. Has nor work been done? is the problem in the staging method? It is basically like CHAD staging, right? I built two of these back when, and I can recall them flying very well.

Jack (Rockeflyer)

Jack,

I think I remember it but I may have lost some of those brain cells in the 60's and 70's.

I seem to recall it reminded me of the Jetex "augmenter" tubes.

Am I on the right track?

Maybe if you post a picture I could jog that memory loose.

Isn't that something like the krusinov (sp) effect?

It looks kinda like a ramjet engine. The motor is in a central tube that is suspended in a larger tube. Air flows through the rocket so that it will have airflow around the end of the motor like a minimum diameter bird, even though the body is much larger. I'm sure the drag is better than a typical rocket of the same outside diameter, which would help altitude. The atmosphere does help direct thrust, eliminating the need for a big bell nozzle at low altitudes where the atmosphere is thicker, but I doubt that it would make enough difference to fool with performance wise on a little 18mm motor.

Little Augie
 

The rocket was a two motor bird, one body tube. The lower was a tube about two dia larger than the main, and held but suppotrs from the upper. The lower motor, booster was held inby strakes on the engine or mountedinside the bell tube. If I recall, the speed from the initial boost helped the air moving through the duct tube helped boost the exhaust velocity, thus adding to the boost of the sustainer motor.

The other effect mentioned is the Krushnic effect, discovered by the young person for whom it is named for, back in the mid 60's. This is the effect caused by recessing the motor to far into the sustainer body, thus not allowing the exhaust gases to buils up to speed, thus creating thrust. In a real sense the motor just burns away producing littl to no thrust and burning you rocket in the process. It's true. I tested the theory, and rockets do burn nicely on the pad, as well as the dried grass around it.


I'm trying to locate the plans for the Little Augie. I have them somewhere.

Jack

Jack,

No need to dig them up. JimZ has them online right here:

http://www.dars.org/jimz/eirp_10.htm

For some reason, I was thinking the outer tube was bigger than that. I'd imagine the added drag of an extra tube would cancel out any added boost. I also don't see how it could actually add thrust other than to help shape the exhaust without a bell nozzle...which shouldn't be a problem in the first place at low altitudes.

Maybe you were thinking of the Augie II.

http://www.dars.org/jimz/eirp_28.htm

Yes, that's exactly the one I was thinking of. Good call! :)

Thanks You
 

Thanks Scott, that's the one, Li'l Augie. I'm gonna build another one of those. For some reason I thought it used the old BT-40 tube instead of the BT-30. No matter, both tubes were strong. Thanks again Scott!