of the fuel and the mass of the rocket at the same time. The prelaunched fuel would provide some visibility into the interstellar medium – thus alerting the trailing spacecraft of unseen hazards (e.g. brown dwarfs). The major disadvantages of this system include The spacecraft could not deviate from the precalculated trajectory unless it was critical to do so. Any such deviation would separate the spacecraft from its fuel supply and leave it with only a minimal ability to return to its original trajectory. Prelaunched fuel for deceleration at the destination star would not be available unless launched many decades in advance of the spacecraft launch. However, other systems (such as the magnetic sails) could be used for this purpose. References For more on ramjet math calculations see External links Interstellar Medium Interstellar Hydrogen Images of Bussard Ramjet Hypothetical spacecraft Interstellar travel Nuclear spacecraft propulsion Hydrogen technologies Hypothetical technology 1960 in science