4 ms·

I don’t know if any real rockets were built, but according to this old video we’d see a reduction of weight due to the absence of heavy chemical fuel. https://

• CydeWeys 6y ago
  The fuel mass is already incorporated into Isp. Hydrogen being less dense causes a problem (not solves one) because the fuel tanks need to be much larger for the same propellant mass, and thus you're adding a lot of structural mass.