Rapier =
Dr Jan Zigmund, creator and manufacturer of Rapier motors has this to say about them: The Rapier model jet propulsion units have been designed for sport and recreational flying of jet powered model aeroplanes. The units are made of a cardboard tube with a refractory nozzle and cover. The ideal thrust to weight ratio has been achieved by using suitable simple materials for the construction of the jet unit tube combined with a special propellant. This propellant has a low burning rate, low flame temperature and is able to burn at low operational pressure in the cardboard combustion chamber. A long burning time and consequent long flight time are of special interest to modelers of jet models. We hope you have many happy hours of fun flying your models using the Rapier Model Jet propulsion unit. Rapiers are available in three power ratings: L-1, L-2 and L-2HP

EDF = ELECTRIC DUCTED FAN  These units can be purchased in many sizes from Free Flight size to radio control models of very large sizes.  This being a stick and tissue site we offer plans in the Free Flight mostly with a few that can be reduced to Free Flight size.

IDF = This is the Internal Combustion Ducted Fan which has been around for a fairly long time.  Mostly powered with glow engines from .049-.60 size engines or larger. Mostly rc models.
RDF = Always desiring to push the limits of rubber band powered aircraft there have been a number of Rubber Ducted Fan plans produced and  experimented with. 
JETEX = Was a popular jet propulsion motor of the 1950s here's a link to their site for current models and motor suggestions: http://archivesite.jetex.org/links.html#sales

SOME IC PLANS CAN BE REDUCED FOR "EDF" "RDF" OR "RAPIER" SIZES