This paper addresses the efficacy of an open-inquiry approach that allows students to build on traditionally received knowledge. A sample of thirty engineering undergraduates, having already attended traditional university physics instruction, was selected for this study. The students were involved in a six-week long learning experience of open-inquiry research activities within the highly motivating context of developing a thermodynamically efficient space base on Mars. They designed and carried out their own scientific investigations, which involved gathering information, collecting and analyzing data, providing explanations, and sharing results. A questionnaire containing fifteen open-ended real-world problems in thermal science was administered to the students both prior to and after all activities, with the aim of investigating the nature of their difficulties in problem solving. Students' answers were classified into three epistemological profiles and a prepost instruction comparison was carried out, using methods of statistical implicative analysis. The students obtained significant benefits from their open-inquiry experiences, in terms of the strengthening of their practical and reasoning abilities, by proficiently applying the learned concepts to face and solve real-world problem situations.