  Relay drones in delay-tolerant applications are dispatched to remote
locations in order to gather data transmitted by a source node. Collected data
are stored on the drones and delivered to one or multiple bases. This paper
considers two schemes for broadcasting data to drones when feedback channels
are not available: a data carousel and systematic random linear network coding
(RLNC). We propose a theoretical framework for the calculation of the
probability that a base will fully or partially recover the transmitted data
and the probability that all involved bases will successfully obtain the data,
when the bases are either isolated or interconnected. Theoretical results are
validated through simulations. Design considerations are also discussed,
including the relationship among the field size used by RLNC, the number of
relay drones and the requirement for full data recovery or the retrieval of at
least part of the data.
