Handout Artist’s renditon of Radian One, a "space plane" capable of reaching orbit in a single stage. A Seattle-area startup called Radian Aerospace is fine-tuning the design of its orbital space plane, with an eye toward building a subscale prototype as early as this year. The company is also in the midst of a fresh round of fundraising, following up on $ 27.5 million in investment that was announced in 2022, according to Livingston Holder, Radian’s co-founder and chief technology officer. “That round will be larger,” Holder said. Over the past two years, Radian has made progress on an ambitious plan to create a reusable winged space plane that would be launched toward low Earth orbit by a rocket-propelled sled and its own rocket engines. The single-stage-to-orbit concept, or SSTO, has been called a “holy grail” for cheap access to spacePhoto by Radian Aerospace via ABACAPRESS.COM