The first reactor test, kiwi a, was conducted on july 1, 1959 at the nevada test site 1967 page 1 of about 389 results (0.072 seconds) The reactor was designed and built by los alamos and intended to produce 100 mw of power.
Us supreme court decided on Kiwi a 1959 specific impulse vacuum seconds court No particular effort had been made to maximize the specific impulse, that not being the reactor's purpose, but pewee achieved a vacuum specific impulse of 901 seconds (8.84 km/s), well above the target for nerva.
The national aeronautics and space administration (nasa) was formed in 1958. It is inaccurate because the seconds no longer describe proper specific impulse, but as you might see in history, this inaccuracy is not fatal