比冲是什么，单位为什么是秒？
What is specific impulse, and why is it measured in seconds?
比冲是单位质量推进剂每秒产生的推力（或单位重量推进剂的冲量），数值上等于排气速度与重力加速度之比，所以常用秒表示效率高低。
Specific impulse is thrust per unit propellant flow (or impulse per weight), numerically the exhaust velocity divided by gravity, so it is quoted in seconds as an efficiency measure.
难度 专业 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
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Sutton《火箭推进原理》；NASA；Tsiolkovsky 火箭方程
Sutton, Rocket Propulsion Elements; NASA; Tsiolkovsky rocket equation
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780665590955 (2002)
#航天 #比冲
齐奥尔科夫斯基公式告诉我们什么？
What does the Tsiolkovsky rocket equation tell us?
它给出火箭速度增量 Δv = v_e·ln(m0/mf)，说明最终速度取决于排气速度和质量比（初始质量与燃料耗尽质量之比），解释了为何要分级和用高效推进剂。
It gives Δv = v_e·ln(m0/mf), showing final speed depends on exhaust velocity and mass ratio, explaining staging and high-efficiency propellants.
难度 专业 · 适合 小学高段(9-12)
CC BY 4.0 · 已核验 · Verified 2026-10-04
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Sutton《火箭推进原理》；NASA；Tsiolkovsky 火箭方程
Sutton, Rocket Propulsion Elements; NASA; Tsiolkovsky rocket equation
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780665590955 (2002)
#航天 #火箭方程
液氢液氧和煤油液氧发动机各有什么取舍？
What are the trade-offs between LH2/LOX and kerosene/LOX engines?
液氢比冲高、利于上面级但密度低、储箱庞大且需极低温；煤油密度大、易储存、适合起飞级，但比冲较低。
Hydrogen gives high specific impulse and suits upper stages but is low-density and cryogenic; kerosene is dense and easy to store, good for liftoff, but less efficient.
难度 专业 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Sutton《火箭推进原理》；NASA；Tsiolkovsky 火箭方程
Sutton, Rocket Propulsion Elements; NASA; Tsiolkovsky rocket equation
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780665590955 (2002)
#航天 #推进剂
火箭发动机的分级燃烧循环是什么？
What is a staged-combustion rocket engine cycle?
它先把部分推进剂在预燃室燃烧产生富燃料气体驱动涡轮，再把这些高温气体全部送入主燃烧室充分燃烧，能量利用率高，代表如RD-180。
It burns some propellant in a preburner to drive the turbine, then feeds all hot gas into the main chamber, achieving high efficiency, such as the RD-180.
难度 专业 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Sutton《火箭推进原理》；NASA；Tsiolkovsky 火箭方程
Sutton, Rocket Propulsion Elements; NASA; Tsiolkovsky rocket equation
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780665590955 (2002)
#航天 #发动机循环
高超音速飞行的发动机为什么不能有风扇和压气叶轮?超燃冲压难在哪?
Why must hypersonic engines drop fans and compressor blades — what makes scramjets so hard?
五倍音速以上,旋转叶轮会被气流磨到失效,发动机只能是一根精心塑形的管子。冲压喷气把来流减速增压后直接燃烧;但超过约六倍音速,减速到亚音速就会把气体加热到分解,于是超燃冲压让气流保持超声速穿过燃烧室,在毫秒停留时间内完成混合与点火燃烧。难点有三:燃料注入混合、火焰稳定、热防护(碳碳材料加主动冷却)。X-51A验证机2013年以约五倍音速完成三分半钟动力飞行,至今仍是工程前沿。
Past Mach five, spinning blades disintegrate in the flow, so the engine becomes a carefully sculpted duct. Ramjets decelerate incoming air for combustion; beyond roughly Mach six even subsonic slowing heats gas until it dissociates — so scramjets keep flow supersonic through the combustor, mixing and burning within millisecond residence times. Three hard problems: fuel injection and mixing, flameholding, thermal protection with carbon-carbon composites plus active cooling. The X-51A demonstrator flew three and a half minutes at about Mach five in 2013 — still the engineering frontier.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
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出处备注：此条未指向带版次的可引用著作（通识性内容、机构文件或未展开的英文书名），本库不提供独立书目出处；如需精确引用，需由编辑补全具体篇目与版次。
Curran,《Scramjet Engines: The First Forty Years»,Journal of Propulsion and Power 第19卷,2003
E. T. Curran, Scramjet Engines: The First Forty Years, Journal of Propulsion and Power 19, 2003
#超燃冲压 #高超音速 #热防护
姿控推力器有什么用？
What are attitude-control thrusters for?
它们是安装在航天器上的小推力喷口，通过短暂喷气产生力矩，用来调整飞行姿态、保持太阳能板对日或天线对地指向。
Small jets on a spacecraft fire briefly to create torque, adjusting attitude so solar panels face the Sun or antennas face Earth.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Sutton《火箭推进原理》；NASA；Tsiolkovsky 火箭方程
Sutton, Rocket Propulsion Elements; NASA; Tsiolkovsky rocket equation
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780665590955 (2002)
#航天 #姿态控制
运载火箭为什么多采用分级？
Why do launch vehicles use staging?
火箭飞出大气层后抛掉已烧完的储箱和发动机，可大幅减轻质量，根据齐奥尔科夫斯基方程，减少死重能显著提高最终速度。
After burnout, discarding empty tanks and engines cuts dead weight; by the Tsiolkovsky equation, less mass means much higher final velocity.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Sutton《火箭推进原理》；NASA；Tsiolkovsky 火箭方程
Sutton, Rocket Propulsion Elements; NASA; Tsiolkovsky rocket equation
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780665590955 (2002)
#航天 #火箭分级
涡扇发动机和火箭发动机都要喷气推进,为什么一个能重复用几千次另一个只能烧一次?
Turbofans and rockets both push with jets — why does one fly thousands of missions and the other burn once?
核心差别是氧化剂来源。涡扇发动机从前方进气道吸入空气,压气机增压后与燃料燃烧,燃气推动涡轮带动压气机再从喷口喷出——自带「呼吸系统」,只需携带煤油,结构可反复检修翻修。火箭必须自携燃料与氧化剂,因为高空与太空没有空气;储箱占掉绝大部分重量,烧完即弃(或像猎鹰九号那样回收复用以摊薄成本)。比冲对比鲜明:涡扇数千秒,液氢液氧真空约450秒。未来单级入轨空天飞机的梦想,正卡在两种模式难以合体。
The oxidizer is the difference. A turbofan breathes: intake air is compressed, burned with fuel, exhaust drives turbines that feed the compressor, then jets out — carrying only kerosene, airframes get overhauled across decades. Rockets must haul both fuel and oxidizer since space has no air; tanks dominate mass, spent stages drop away (or land again, Falcon 9 style, to spread cost). Specific impulse contrasts sharply: turbofans reach thousands of seconds, hydrogen-oxygen vacuum about 450. Single-stage-to-orbit dreams stall precisely on marrying the two modes.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 2 条独立证据
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Sutton 与 Biblarz,《Rocket Propulsion Elements》第9版,Wiley,2016
G. P. Sutton and O. Biblarz, Rocket Propulsion Elements, 9th ed., Wiley, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9780665590955 (2002)
#涡扇发动机 #火箭推进 #比冲