Lifetime Embodied Energy: A New Value System for the Coming Space Economy

Diagram: General organization of a Lifetime Embodied Energy model for a Mars outpost. The embodied energy of space logistics is the source of embodied energy for Mars systems. This energy is subsequently allocated from upstream to downstream systems.

Aerospace engineers often rely on mass-based metrics, like the Initial Mass in Low Earth Orbit (IMLEO), to estimate space mission costs. However, developments such as reusable rockets, in-situ resource utilization (ISRU), in-space manufacturing (ISM), and a shift towards lasting habitats on other planets have weakened the link between these mass proxies and the true economic costs of space exploration. Consequently, there's a pressing need for more accurate cost indicators that can withstand the evolving landscape of human spaceflight.

In a thesis, conference papers and a book chapter I proposed Lifetime Embodied Energy (LEE) as an alternative to IMLEO and similar metrics. Establishing settlements on planetary surfaces requires significant initial and continual work, and energy is as an ideal unit measure for work in all its forms. Originating in the 1970s among ecologists and economists, embodied energy gauges cumulative work, mostly utilized nowadays for assessing building energy life cycles. Lifetime embodied energy looks both backward and forward to all direct and indirect energy costs to create, operate, sustain and decomission any system. Hence, for space logistics, LEE is proposed as a standard cost proxy unit, ensuring it aligns with the current emphasis on mass reduction in space missions.

Studies with toy models, discussed in detail in the AIAA 2018 paper and the 2023 Handbook of Space Resources chapter, indicate divergent embodied energy costs even when IMLEO remained unchanged, underscoring the need for a new metric to replace launched mass.

A summary of important LEE findings:

• Lifetime embodied energy per unit of lifetime emplaced mass is superior to logistical mass as a proxy for the true economic cost of in-space activities;
• Low-LEE architectures with significant investments in ISRU and ISM also offer opportunities for a simultaneous increase in system reliability
• Investment in ISRU and ISM must be accompanied by investments in AI-powered industrial robotics to mitigate the impact on crew free time;
• Private companies and space agencies may wish to reconsider technology roadmapping priorities, emphasizing the early development of in situ supply chains and designing space systems for manufacturability rather than for minimum mass or for component-level reliability.

In conclusion, the proposed LEE metric fosters better strategies for crafting sustainable human settlements on other planets, paving the way for future self-sufficiency from Earth.

For more details, there is a full-length chapter on Lifetime Embodied Energy in the Handbook of Space Resources (2023) and an AIAA Space conference paper (2018).