In this letter, a reservation scheme with contention resolution diversity slotted ALOHA (CRDSA), called R-CRDSA, is proposed. Although CRDSA promises excellent performance compared to slotted ALOHA (SA), there are two barriers to be overcome for its use in satellite networks. The first is a low critical point of an offered load; i.e., at this point, as the offered load increases, the throughput will decrease. CRDSA has a lower critical point than that of SA. The second barrier is that CRDSA has a lower capacity efficiency compared to SA; i.e., on average, CRDSA requires more power or bandwidth than SA for transmission. R-CRDSA can overcome these barriers at the same cost as CRDSA, especially for multi-packet messages. The analytic performances are derived by the observation of the transition between two successive frames, and the average number of packets in a message. The simulation results show that the analytic derivations are valid, and they confirm that the barriers are resolved by R-CRDSA.