Heat Is the New Constraint in Orbit: Who Will Build the Radiators of the Space Economy

Abstract

Heat is a hard limit in orbit: in a vacuum, a spacecraft can shed heat only by radiating it. The International Space Station’s main cooling system needs about 475 square metres and almost 7 tonnes of radiators to reject 70 kW; at that performance, one megawatt would take about 6,800 square metres and nearly 100 tonnes, some $145 million just to launch. Demand is rising on two fronts: there are more satellites, each using more power, and on top come on-board computing and the first orbital data centres. Capital is not following the constraint: the four thermal start-ups profiled have disclosed about $25 million between them, against $420 million raised by Starcloud in 2026 alone. Deployable radiators, adaptive coatings and parts of active cooling loops are the segments most open to newcomers, while heat pipes are protected by qualification barriers and heat pumps still have no commercial entrant. Exits run through M&A, and the largest values sit with players that reached markets beyond space. The main risks are that orbital data centres remain hype, that qualification cycles delay revenue, that customers are few and concentrated, and that primes build thermal systems in-house.