Premise and audience benefit: readers will see that the 1977 settlement concept depended on several provisional systems—rotation, shielding materials, agricultural land, routed sunlight, and industrial revenue—rather than one magical life-support technology. Create exactly five punchy fact cards, each self-contained and tied to a named report concept: artificial gravity and rotation; lunar ore and mass-driver logistics as the material supply problem; the unresolved question of agricultural area; the large stationary mirror for routing sunlight; and space-based solar power stations as the proposed commercial engine. Keep each card to one standout fact or a sentence of no more than 20 words, define unfamiliar terms within the card, and distinguish specified mechanisms from questions the study left open. Do not invent a numerical agricultural area or claim that the ecology was complete.