The burning of solid fuels such as boron in ramjet type engines has presented many problems. It has been difficult to supply the boron to the burner at a uniform rate and it has been difficult to maintain the ignition temperature for the boron.
When air or other gas has been used as a carrier for the solid boron fuel, it has been difficult to maintain a uniform flow. Solid boron fuel slurry has been found to be difficult to pump and regulate and it has been difficult to provide a uniform burning for solid boron fuel delivered in this manner. In the past, solid boron has always been burned in the presence of another more easily burned fuel.