Franklin Chang Díaz’s scientific contributions

While solar electric propulsion (SEP) is being widely considered for cargo transport to Mars, its value for propelling fast human missions is often viewed as marginal. This conclusion is driven by the high electric power requirement (multi megawatts) of a fast human spacecraft, coupled to the low power density of traditional solar arrays. For these applications, nuclear electric propulsion (NEP) appears to provide a better electric alternative. However, recent progress in the field of thin film photovoltaic cells and large deployable structures may, at least in the short-term, challenge this conclusion. Although ultimately NEP systems might very well become the mainstay of fast human deep space transport, we examine the human SEP option as an attractive intermediate path on this journey, one that capitalizes on the rapid evolution of the solar array technology being experienced today. We investigated the challenges of building suitably large, lightweight, solar arrays to produce the required electric power for both cargo and human interplanetary spacecraft and examined the advantages of such SEP architectures in the context of a long-stay human Mars mission. Within this framework, we present some conclusions regarding the prospects for this technology.