Seal for gimbaling and/or fixed rocket engine nozzles, and associated systems and methods

A rocket propulsion system, comprising:

• a rocket engine having a gimbalable exhaust nozzle;
• a spherical seal plate carried by the exhaust nozzle;
• and
• a seal engaged with the seal plate, the seal including:
• at least one support;
• multiple flap pairs arranged circumferentially around the nozzle, each one of the flap pairs including:
• a first pivotable flap pivotable about a first hinge rotatable about at least a first pin and positioned to contact the seal plate;
• a second pivotable flap pivotable about a second hinge rotatable about at least a second pin and positioned to shield the first pivotable flap, wherein the first pivotable flap of one of the multiple flap pairs overlaps the second pivotable flap of a neighboring one of the multiple flap pairs;
• an actuator rod coupled to the second pivotable flap;
• a first spring coupled to the actuator rod to bias the second pivotable flap in a first rotary direction;
• a second spring coupled to the actuator rod to bias the second pivotable flap in a second rotary direction opposite the first rotary direction;
• and
• at least one support carrying the first and second pivotable flaps.

A seal for a rocket engine, comprising:

• at least one support positioned outwardly from an exhaust nozzle;
• multiple, pivotable first flaps, each having a sealing surface, with an individual one of the first flaps carried by the at least one support and pivotable about a first hinge rotatable about at least a first pin;
• multiple, pivotable second flaps, with an individual one of the second flaps (i) pivotable about a second hinge rotatable about at least a second pin and (ii) positioned to shield the individual one of the first flaps;
• and
• at least one forcing element operatively coupled to the individual one of the first flaps or the individual one of the second flaps, or both, to apply a pivoting force to the individual one of the first flaps or the individual one of the second flaps.