The program was marred by various concerns, notably the safety of Mir following a fire and a collision, financial issues with the cash-strapped Russian space program and worries from astronauts about the attitudes of the program administrators. Nevertheless, a large amount of science, expertise in space station construction and knowledge in working in a cooperative space venture was gained from the combined operations, allowing the construction of the ISS to proceed much more smoothly than would have otherwise been the case.
