木制卫星正在从概念走向现实。2024年12月9日从国际空间站释放的LignoSat虽通信失败，但其以木兰木为主体的结构经受住了太空考验：在−100°C至+100°C的温度循环与太阳风辐射下保持完好，直至116天后再入大气层。另一项测试载具WISA Woodsat计划于今年夏天发射，采用可耐受−163°C的桦木胶合板。木材相较合金更轻、更便宜，且对无线电透明，有望减少部署复杂度。

环境与合规是关键动因。2023年约有290吨太空垃圾坠入大气；研究发现所采样的平流层硫酸颗粒中约十分之一含金属。预测显示到2035年，每年坠落量或超2,800吨。金属蒸发可能引发化学反应并影响臭氧，而木材燃烧主要生成烟尘，尽管其与电子蒸汽反应的影响仍未知。与此同时，监管趋严的“为消亡而设计”规则要求控制再入；通常超过约300公斤的卫星需昂贵的受控再入。引入可在大气中烧蚀的木材，或使重量高达1吨的航天器免于此成本。

工程收益同样显著。木材不干扰无线电，通信设备可内置，降低碎片损伤与稀薄大气阻力。计划于2028年在400公里轨道测试的LignoSat2将验证这一点，预计阻力降低可使寿命延长约50%。木材还能吸振、隔热，减少加热能耗。虽真空会析出水分与有机物，但试验表明影响有限，涂覆氧化铝可进一步防护。小型航天器或将“返木而行”。

Wooden satellites are moving from concept to reality. LignoSat, released from the ISS on December 9th 2024, lost communications but proved its magnolia structure could survive space: temperature swings from −100°C to +100°C and solar-wind radiation left panels intact until re-entry 116 days later. Another test craft, WISA Woodsat, is due this summer using birch plywood rated to −163°C. Compared with alloys, wood is lighter and cheaper, and transparent to radio signals, simplifying design.

Environmental and regulatory pressures matter. About 290 tonnes of space junk fell into the atmosphere in 2023; roughly a tenth of sampled stratospheric sulphuric-acid particles contained metal. By 2035, annual fall-in may exceed 2,800 tonnes. Vaporised metals could spur chemistry that harms ozone, whereas wood mainly yields soot, though interactions with electronic vapours remain uncertain. “Design for demise” rules are tightening: satellites over ~300kg often need costly controlled re-entry. Using wood that burns up could let craft up to 1 tonne re-enter uncontrolled, avoiding that expense.

Engineering benefits add up. Wood does not block radio waves, allowing embedded antennas and reducing damage from debris and drag in low orbits. LignoSat2, planned for a 400km orbit in 2028, will test whether reduced drag extends life by about 50%. Wood also damps vibrations and insulates better, cutting heater use. Vacuum outgassing is a risk, but tests suggest it is manageable, especially with aluminium-oxide coatings. Small spacecraft may soon revert to timber hulls.