Satellite communications modeled by a feedforward random multiple-access system is considered. The transmission times of the users are governed by protocol signals. More specifically, we consider the model of slot-synchronized collision channel without feedback, proposed by Massey and Mathys, augmented by interleavers that are essential for enabling the use of practical short codes. We assess the throughput of the channel on the basis of a (so-called) short-coding error parameter. The set of parameters of all users characterizes the rate region achievable by employing short block codes with nonideal interleaving. The short-coding error parameter corresponds to a bound on the probability of error which is tighter than the bound expressed with the aid of the conventional cutoff rate. The analysis brings into account practical communication aspects, such as the effect of interleaving span and noise in noninterfered slots.