sentences:  Once the orbit is established, no propulsion is required to shuttle between the two, although some minor corrections may be necessary due to small perturbations in the orbit.The use of cyclers was considered in 1969 by Walter M. Hollister, who examined the case of an Earth–Venus cycler.Hollister did not have any particular mission in mind, but posited their use for both regular communication between two planets, and for multi-planet flyby missions.