Heavy inert gas insulated blast tube

An insulated blast tube, comprising:

• a hollow blast tube shell defining a sealed void space therein along a length of the shell;
• and
• an insulating layer of phenolic resin having a thermal conductivity (Tcond_phenolic) on an interior surface of the shell,
• wherein vacuum is pulled on the sealed void space and then filled with an inert gas selected from Argon, Krypton, Xenon or a synthetic inert gas having a density of at least 1.5 Kg/m3 and a thermal conductivity (Tcond_gas) of no greater than two-thirds of a thermal conductivity of air (Tcond_air) to form a heavy inert gas insulation layer, wherein the thermal conductivity of the inert gas is less than one-one hundredth the thermal conductivity of the phenolic resin,
• wherein the insulated blast tube couples a nozzle to a rocket motor.

A rocket motor, comprising:

• a cylindrical rocket motor casing having a diameter D1;
• a combustion chamber including a propellant positioned in the cylindrical rocket motor casing;
• a nozzle positioned aft of the combustion chamber to expel hot gases resulting from combustion of the propellant;
• an insulated blast tube that couples the combustion chamber to the nozzle, said blast tube having a diameter D2<D1 that defines a first void space between the blast tube and the rocket motor casing;
• one or more sub-systems positioned in the first void space,
• wherein the insulated blast tube comprises,
• a hollow blast tube shell defining a second sealed void space therein along a length of the shell;
• and
• an insulating layer formed of a burn resistant material on an interior surface of the shell that erodes as hot gases pass through the blast tube and protects the blast tube from elevated temperatures,
• wherein the second sealed void space contains an inert gas having a density of at least 1.5 Kg/m3 and a thermal conductivity (Tcond_gas) of no greater than two-thirds of a thermal conductivity of air (Tcond_air) to form a heavy inert gas insulation layer to provide additional thermal insulation to thermally insulate the one or more sub-systems.