During the 1960s and 1970s, scientists designed a spacecraft based on nuclear propulsion, but it was never built. true

It is true that during the 1960s and 1970s, scientists designed a spacecraft based on nuclear propulsion, but it was never built.

Some of the examples of spacecrafts based on nuclear propulsion that were proposed are the following (in no particular order):

Project Daedalus

Project Orion

AIMStar

Project Longshot

External Pulsed Plasma Propulsion

ICAN-II

i do not have an answer but if you make me the brainliest/5 stars i will freind request you

explanation:

nothing certain is known about what happened, but it seems that the country declined gradually, perhaps due to bad government, or, more likely, due to a series of bad harvests, which resulted in widespread and recurrent famine.