Word tips radically adj. 根本地;彻底地 obstacle n. 障碍;障碍物 space shuttle 航天飞机 enormous adj. 巨大的 misconception n. 错误认识;误解 velocity n. 速度 haul up 拖上去,拉上去 fraction n. 小部分;少量 feasible adj. 可行的 lightweight adj. 轻量的,的 tensile adj. 张力的;拉力的 nanotube n. 纳米管 ribbon n. 丝带;带子 Questions: 1. What is the biggest obstacle today to putting structures, equipment and people into space? 2. Why does the student mention climbing a ladder? 3. What new approach did the professor propose? 4. What features do the new material carbon nanotubes have