A propulsion element including a catalyzing reactor, the catalyzing reactor having a reactor entrance, a reactor exit, and an internal structure configured for flowing a reacting medium from the reactor entrance to the reactor exit, the internal structure comprising at least one reactor channel having a channel wall that includes a catalyst for catalyzing a reaction of the reacting medium,
- wherein the reactor channel defines a flow path between the reactor entrance and the reactor exit, and wherein the reactor channel is looped such that a first portion of the flow path that is relatively more downstream with respect to the reactor entrance is proximate, and in heat exchanging contact with, a second portion of the flow path that is relatively more upstream with respect to the reactor entrance, the reactor channel being configured for transferring heat between the reacting medium present in the first portion of the flow path and the reacting medium present in the second portion of the flow path.