Conrad Zeidler

Greenhouse Module for Space System: A Lunar Greenhouse Design

Abstract In the next 10 to 20 years humankind will return to the Moon and/or travel to Mars. It is likely that astronauts will eventually build permanent settlements there, as a base for long-term crew tended research tasks. It is obvious that the crew of such settlements will need food to survive. With current mission architectures the provision of food for longduration missions away from Earth requires a significant number of resupply flights. Furthermore, it would be infeasible to provide the crew with continuous access to fresh produce, specifically crops with high water content such as tomatoes and peppers, on account of their limited shelf life. A greenhouse as an integrated part of a planetary surface base would be one solution to solve this challenge for long-duration missions. Astronauts could grow their own fresh fruit and vegetables in-situ to be more independent from supply from Earth. This paper presents the results of the design project for such a greenhouse, which was carried out by DLR and its partners within the framework of the Micro-Ecological Life Support System Alternative (MELiSSA) program. The consortium performed an extensive system analysis followed by a definition of system and subsystem requirements for greenhouse modules. Over 270 requirements were defined in this process. Afterwards the consortium performed an in-depth analysis of illumination strategies, potential growth accommodations and shapes for the external structure. Five different options for the outer shape were investigated, each of them with a set of possible internal configurations. Using the Analytical Hierarchy Process, the different concept options were evaluated and ranked against each other. The design option with the highest ranking was an inflatable outer structure with a rigid inner core, in which the subsystems are mounted. The inflatable shell is wrapped around the core during launch and transit to the lunar surface. The paper provides an overview of the final design, which was further detailed in a concurrent engineering design study. During the study, the subsystem parameters (e.g. mass, power, performance) were calculated and evaluated. The results of the study were further elaborated, leading to a lunar greenhouse concept that fulfils all initial requirements. The greenhouse module has a total cultivation area of more than 650 m² and provides more than 4100 kg of edible dry mass over the duration of the mission. Based on the study, the consortium also identified technology and knowledge gaps (not part of this paper), which have to be addressed in future projects to make the actual development of such a lunar greenhouse, and permanent settlements for long-term human-tended research tasks on other terrestrial bodies, feasible in the first place.

Greenhouse Modules and Regenerative Life-Support Systems for Space

Long exploration missions to the Moon and Mars will require the growth of food on site to sustain the crew because current launchers are unable to send the required mass of consumables into orbit at an affordable cost. Growing fresh food will also be of prime importance for the crew dietary and psychological requirements. ESA expertise on advanced life support systems within the MELiSSA (Micro-Ecological Life Support System Alternative) project, coupled to the EDEN (Evolution and Design of Environmentally-closed Nutrition Sources) project in DLR join forces to study a greenhouse within the MELiSSA loop for a manned base on the Moon surface. Both projects are aimed at studying and developing regenerative life support systems for long duration space missions: MELiSSA is a closed artificial ecosystem program based on microbiological and physicochemical waste degradation and higher plants; EDEN combines different CEA Technologies (Controlled Environmental Agriculture) within an automatic planetary Greenhouse-Module (GHM). Previous studies on Greenhouse Modules have addressed mass, volume, and energy consumption needs but the technologies and data on which these calculations were based are now outdated or were limited at that time. They thus need to be reassessed to have better estimates of these variables and evaluate what it takes to grow plants on the Moon. A study of the lunar environment based on various elements such as illumination, radiation levels, accessibility, and temperature gradients, enables to make a comparative analysis for the best location to setup a greenhouse module on the Moon surface. Trade-offs between electrical and natural lighting, and various grow accommodation options, based on the ALISSE criteria are also conducted. Finally, this leads to the identification of critical points and recommendation on future work for preliminary greenhouse concepts.