arXiv:2610.19462v1 Announce Type: new Abstract: Emerging data-intensive space applications generate large volumes of data that must be processed, stored, replicated, and delivered efficiently. However, relying on terrestrial cloud regions can expose satellite data to high delivery latency and loss of timeliness due to intermittent satellite-to-ground visibility and limited access to ground infrastructure. Space Data Centers (SDCs), which organize collaborative satellites into logical compute and storage clusters, offer a promising approach for in-orbit data management and service continuity. In this paper, we first evaluate how satellite clustering with different sizes affects satellite visibility and gateway outage. We then propose BIER-DC, a stateless one-to-many communication protocol tailored for satellite-based SDCs. Unlike terrestrial multicast protocols designed for stable data center fabrics, BIER-DC decouples inter-SDC forwarding from intra-SDC delivery and encodes compact cluster-level forwarding information in packet headers. Comparative evaluations against BIER, BIER-TE, and Yeti show that BIER-DC significantly reduces packet-header length and byte-hop overhead, improving effective goodput and scalability for next-generation LEO space data centers.