It's definitely worse than H2's ISP in an NTR, but ~600s is still a solid boost over the ~450s that's about the best a practical LOX/LH2 chemical engine can do.

It's definitely worse than H2's ISP in an NTR, but ~600s is still a solid boost over the ~450s that's about the best a practical LOX/LH2 chemical engine can do. My curiosity is essentially just whether the performance lost between an H2 and CH4 NTR would be gained back through reduced tank mass and boil-off. Shielding/engine mass will certainly be a big mass penalty versus chemical rockets.