Hybrid rocket engine fuel grains with compositional variations

The method of any of the preceding claims, in which depositing the beads of fuel grain material comprises rotating the mandrel during deposition of the beads.

The method of any of the preceding claims, comprising depositing the beads using a single deposition head.

The method of any of the preceding claims, comprising depositing the beads of the first layer using a first deposition head and depositing the beads of the second layer using a second deposition head.

The method of any of the preceding claims, comprising encasing the fuel grain in a cover without removing the fuel grain from the mandrel.

The method of any of the preceding claims, comprising varying an extrusion rate of the fuel grain material during the depositing.

The method of any of the preceding claims, comprising stopping the depositing to define a void in the fuel grain.

A method of making a fuel grain for a hybrid rocket engine, the method comprising:

• depositing multiple beads of fuel grain material adjacent to one another to form a fuel grain defining a combustion port extending axially therethrough, each bead of fuel grain material comprising a polymer based rocket fuel material,
• in which the depositing includes depositing beads of different form, beads of different composition, or both, such that the composition of the fuel grain varies within the fuel grain.

A fuel grain for a hybrid rocket engine, the fuel grain comprising:

• multiple, concentric layers of fuel grain material defining a combustion port extending through a body of the fuel grain, in which each layer comprises multiple beads of fuel grain material, in which the multiple beads in a given layer are disposed adjacent to one another and bonded together, and in which adjacent concentric layers are bonded together,
• in which each bead of fuel grain material comprises a polymer based rocket fuel material, and in which a composition of the fuel grain material varies along a radius of the fuel grain.

A fuel grain for a hybrid rocket engine, the fuel grain comprising:

• multiple layers of fuel grain material defining a combustion port extending through a body of the fuel grain, in which each layer comprises multiple beads of fuel grain material, in which the multiple beads in a given layer are disposed adjacent to one another and bonded together, and in which adjacent layers are bonded together,
• in which each bead of fuel grain material comprises a polymer based rocket fuel material, and
• in which a composition of the beads of the fuel grain material, a form of the beads of fuel grain material, or both varies within the fuel grain.