Informal science education (ISE) programs serve as a method for developing, encouraging, and increasing both participation in, and enthusiasm for, STEM learning. One type of ISE program is provided by Challenger Centers through their space education curricula. Unfortunately, published evaluations related to space education programs are rare. The lack of research on informal space education programs has created a gap in our knowledge about the effectiveness of these programs in developing students' understanding of STEM related topics, their interest in STEM careers, and the connections they make to formal science learning outcomes. Even less is known about how subgroups of students respond to ISE space education programs. The purpose of this study was to report on the effectiveness of the space education program at one Challenger Center. Specifically, the attitudes and perceptions of middle school students on STEM related constructs were investigated at three points (pre, during, and post space mission), to determine how their beliefs changed over time. Additionally, we examined subgroups of students to further explore how involvement in the program influenced beliefs about STEM related constructs. Results demonstrate that students (N = 2945) felt very positive about their experience in the program and reported positive changes in attitudes and perceptions two weeks post-mission experience. Males (n = 719) had significantly greater changes in beliefs when compared to females (n = 748), and the program had a greater influence on the beliefs of students who are typically well represented in ISE programs (n = 949) compared to the subgroup of students who are typically underrepresented (n = 519) in ISE programs. Study limitations, future research, and implications are provided.