We analyse how incumbent firms from terrestrial industries tackle opportunities in the Space Economy. Grounded in extensive data obtained from case studies across different markets, we develop a novel framework named 'Resource-Knowledge Generalizability Model' which outlines three strategic approaches to entry in the emerging Space Economy, classified as discovery, reinvention, and repurposing. Specifically, discovery requires the development of new knowledge to pursue opportunities far beyond the firm's initial capabilities. Reinvention starts instead with existing capabilities but demands significant adaptation for the new market. Finally, repurposing leverages existing knowledge and capabilities with minimal changes. Our findings demonstrate that the suitability of each entry strategy depends on the interplay between a firm's resource availability and the generalisability of its knowledge base. Discovery is best suited for firms with substantial resources, enabling them to develop groundbreaking capabilities for opportunities outside their traditional domains. Reinvention is advantageous for firms with moderate resources, allowing them to adapt and extend their existing capabilities to new contexts. Finally, repurposing is most effective for resource-constrained firms with highly generalisable knowledge, facilitating efficient entry with minimal adjustments. These insights contribute to a deeper understanding of strategic entry in high-tech, nascent markets, offering guidance for firms navigating the unique challenges and opportunities of dynamic and uncertain environments.