The helium is just a recirculating coolant. In the test rig, it's being cooled by boil-off of LN2. In a flight configuration, using cryogenic propellants as a

The helium is just a recirculating coolant. In the test rig, it's being cooled by boil-off of LN2. In a flight configuration, using cryogenic propellants as a heat dump seems logical.