再入角度为什么必须控制得很精确？
Why must the reentry angle be precisely controlled?
角度太陡会因过热烧穿或过载过大；太浅则会被大气层弹回太空无法着陆，因此需在狭窄的走廊内再入。
Too steep overheats or overloads the craft; too shallow and it skips back into space, so reentry must stay within a narrow corridor.
难度 专业 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
Sutton & 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)
#航天 #再入
返回舱再入大气层时如何防热？
How does a reentry capsule resist heat?
高速再入时空气被剧烈压缩产生上千摄氏度高温，返回舱用烧蚀防热层（表层材料受热分解带走热量）和隔热层保护舱内人员与设备。
High-speed reentry compresses air to over a thousand degrees; capsules use an ablative heat shield, where material chars and carries heat away, plus insulation to protect crew and gear.
难度 专业 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
Sutton & 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)
#航天 #再入防热
后掠翼和面积律为什么能让飞机飞得更快？
Why do swept wings and the area rule let aircraft fly faster?
后掠翼把来流分解为垂直于前缘（弦向）和沿前缘（展向）两个分量，只有较小的弦向分量 V·cosΛ 决定压缩性效应，从而把激波出现和阻力发散推迟到更高马赫数；面积律要求全机横截面积沿纵轴平滑变化，以减小跨音速波阻。两者都是突破跨音速阻力急升的关键设计。
A swept wing splits the oncoming flow into a chordwise component normal to the leading edge and a spanwise component along it; only the smaller chordwise component V·cosΛ drives compressibility effects, pushing shock formation and drag rise to higher Mach numbers. The area rule requires the whole aircraft's cross-sectional area to vary smoothly along its axis to cut transonic wave drag. Both were key to overcoming the transonic drag rise.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
Küchemann《飞机气动设计》(The Aerodynamic Design of Aircraft)；Whitcomb《近声速翼身组合零升阻力上升特性研究》(NACA RM L52H08, 1952)
Küchemann, 'The Aerodynamic Design of Aircraft'; Whitcomb, 'A Study of the Zero-Lift Drag-Rise Characteristics of Wing-Body Combinations Near the Speed of Sound' (NACA RM L52H08, 1952)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL22640504W：The aerodynamic design
#后掠翼 #面积律 #波阻 #跨音速
GPS 接收机是怎样在噪声中精准定位的，卡尔曼滤波起什么作用？
How does a GPS receiver pinpoint location in noise, and what does the Kalman filter do?
接收机测量多颗卫星信号的传播时延算出距离，再经三边交会确定位置；卡尔曼滤波则把带噪声的连续观测与运动模型融合，平滑估计并预测位置、速度。Kalman 在 1960 年提出这一递推最优估计方法。
The receiver measures signal travel time from several satellites to get distances, then trilaterates position; the Kalman filter fuses noisy sequential observations with a motion model to smooth and predict position and velocity. Kalman introduced this recursive optimal estimator in 1960.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
Kaplan 与 Hegarty《GPS 原理》(Understanding GPS)；Kalman《新线性滤波方法》(Journal of Basic Engineering, 1960)
Kaplan & Hegarty, 'Understanding GPS'; Kalman, 'A New Approach to Linear Filtering' (1960)
#GPS #卡尔曼滤波 #三边交会 #时延
喷气发动机的工作循环对应热力学里的哪个循环？
Which thermodynamic cycle does a jet engine correspond to?
涡轮喷气发动机近似布雷顿循环：空气经进气道和压气机连续增压，在燃烧室近似定压加热，再经涡轮和尾喷管膨胀做功并排出。提高总增压比和涡轮前温度可提升热效率与推力，而涡轮叶片的耐温能力是主要约束，这正是燃气轮机设计的核心矛盾。
A turbojet approximates the Brayton cycle: air is compressed continuously by the inlet and the compressor, heated at roughly constant pressure in the combustor, then expanded through the turbine and nozzle before exhausting. Raising the overall pressure ratio and the turbine-inlet temperature improves efficiency and thrust, while blade temperature capability is the main constraint—the central trade-off of gas-turbine design.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04 · 3 条独立证据
来源 · Source
Mattingly《燃气轮机推进原理》(Elements of Gas Turbine Propulsion)；Cengel《工程热力学》
Mattingly, 'Elements of Gas Turbine Propulsion'; Cengel & Boles, 'Thermodynamics: An Engineering Approach'
独立核验依据 · Independent verification: 核验依据 1 ISBN 978-1-259-27989-8 (9th ed., McGraw-Hill) · 核验依据 2 ISBN 9781260116106 (2018) · 核验依据 3 ISBN 9780665590955 (2002)
#布雷顿循环 #喷气发动机 #增压比 #燃气轮机
火箭上升过程中为什么要在最大动压点前后减小推力？
Why do rockets throttle down around the point of maximum dynamic pressure?
动压等于二分之一空气密度乘速度平方，上升时速度增大而密度减小，二者乘积在某一高度出现峰值，通常在起飞后一分钟多。此处箭体承受的气动载荷最大，稍有姿态偏差就可能超过结构极限。因此控制律会在这一段临时节流降速，过后再恢复全推力。
Dynamic pressure equals half the air density times velocity squared; as the rocket climbs, speed rises while density falls, so their product peaks at a certain altitude, usually a bit over a minute after liftoff. Aerodynamic loads on the vehicle are highest there, and a small attitude deviation could exceed structural limits. The control law therefore throttles back through this region and restores full thrust afterwards.
难度 专业 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
Sutton & 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)
#最大动压 #气动载荷 #节流
陀螺仪为什么能保持方向稳定，进动又是怎么回事？
Why does a gyroscope hold its orientation, and what is precession?
高速旋转的转子因角动量守恒倾向于保持转轴方向不变，外力矩不会立刻把它推倒，而是引发进动——角动量沿力矩方向变化，使转轴绕垂直于力矩的方向缓慢转动。这一特性被用于惯性导航和航天器姿态稳定。
A fast-spinning rotor tends to keep its spin axis fixed by conservation of angular momentum; an applied torque does not tip it over at once but causes precession—the angular momentum changes along the torque direction, so the axis slowly swings about an axis perpendicular to the torque. This underlies inertial navigation and spacecraft attitude control.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
Hughes《航天器姿态动力学》(Spacecraft Attitude Dynamics)；Goldstein、Poole 与 Safko《经典力学》(Classical Mechanics)，第 3 版
Hughes, 'Spacecraft Attitude Dynamics'; Goldstein, Poole & Safko, 'Classical Mechanics' (3rd ed.)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL8253810W：Spacecraft Attitude Dyn
#陀螺仪 #角动量 #进动 #姿态稳定
陀螺仪的『定轴性』如何帮助飞行器定位姿态？
How does a gyroscope's 'rigidity' help aircraft determine attitude?
高速旋转的陀螺具有保持自转轴方向不变的定轴性。将其装于飞行器，转轴相对机身的变化就能反映俯仰、横滚和偏航姿态，是惯性导航的核心元件。
A fast-spinning gyro resists changes to its spin axis. Mounted on a craft, shifts of that axis against the airframe reveal pitch, roll, and yaw—core to inertial navigation.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
David Macaulay,《The Way Things Work》,Houghton Mifflin,1988;中译《万物运转的秘密》
D. Macaulay, The Way Things Work, Houghton Mifflin, 1988; Chinese ed.
独立核验依据 · Independent verification: 核验依据 2 OPENLIBRARY 标识 /works/OL15130328W：The Way Things Work（按标
#陀螺仪 #定轴性 #姿态
火箭发动机的再生冷却是怎么保护燃烧室的？
How does regenerative cooling protect a rocket engine's combustion chamber?
燃烧室内温度可达三千摄氏度以上，远超金属熔点。再生冷却在室壁内开出许多细密通道，让低温燃料先流过通道带走热量，再进入喷注器燃烧。这样壁面被持续冷却，同时燃料被预热，燃烧更完全，热量没有白白浪费，因此称为再生。
Combustion gases can exceed three thousand degrees Celsius, far above the melting point of metals. Regenerative cooling runs many fine channels through the chamber wall so that cold fuel flows through them, carries heat away, and only then enters the injector to burn. The wall is continuously cooled while the fuel is preheated, improving combustion, so the heat is recycled rather than wasted, which is why it is called regenerative.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
Sutton & 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)
#再生冷却 #燃烧室 #热防护
反作用轮和磁力矩器为什么要配合使用？
Why are reaction wheels and magnetic torquers used together?
反作用轮通过改变自身转速与星体交换角动量，实现精细无污染的姿态控制，但长期受重力梯度、气动等干扰力矩作用会不断加速，最终饱和。磁力矩器让线圈电流与地磁场作用产生外力矩，把多余角动量卸掉，使轮子回到低转速。这种组合在低轨卫星上很常见，几乎不消耗工质。
Reaction wheels exchange angular momentum with the spacecraft by changing their own speed, giving fine, contamination-free attitude control, but persistent disturbance torques from gravity gradient and aerodynamics keep spinning them up until they saturate. Magnetic torquers pass current through coils that interact with Earth's magnetic field to produce an external torque, dumping the excess momentum and returning the wheels to low speed. This pairing is common on low-Earth-orbit satellites and consumes almost no propellant.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
Wertz《航天器姿态动力学与控制》
Wertz, Spacecraft Attitude Dynamics and Control
#反作用轮 #磁力矩器 #角动量卸载
超音速飞行时为什么会产生激波和马赫锥？
Why do shock waves and a Mach cone form in supersonic flight?
当飞行速度超过声速，前方压力信息来不及向前传播，被压缩堆积成一道近似不连续的激波，导致压强、温度和密度骤升。所有扰动被限制在机后一个以马赫角为半顶角的圆锥（马赫锥）内。
Once flight exceeds the speed of sound, pressure information cannot propagate ahead, so disturbances pile up into a near-discontinuous shock where pressure, temperature, and density jump. All disturbances are confined behind a cone of half-angle equal to the Mach angle.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
Anderson《现代可压缩流动》(Modern Compressible Flow)；Mach《激波研究》(1887)
Anderson, 'Modern Compressible Flow'; Mach, 'On supersonic projectile shock' (1887)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL1993329W：Modern compressible flo
#激波 #马赫锥 #超音速 #马赫角
齐奥尔科夫斯基火箭方程告诉我们什么限制？
What limitation does the Tsiolkovsky rocket equation reveal?
它表明火箭能达到的速度增量只取决于排气速度与质量比（起飞质量/末质量）的自然对数，与推力大小无关。这意味着要想高速，必须尽量提高比冲或减轻结构质量，因此多级火箭才成为必然。
It shows the achievable velocity change depends only on exhaust velocity and the natural log of the mass ratio (initial/final), not on thrust magnitude. To go fast you must raise specific impulse or cut structural mass, which is why staging is essential.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Sutton 与 Biblarz《火箭推进元件》(Rocket Propulsion Elements)，第 9 版；Tsiolkovsky《太空火箭》(1903)
Sutton & Biblarz, 'Rocket Propulsion Elements' (9th ed.); Tsiolkovsky, 'Exploration of Cosmic Space' (1903)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780665590955 (2002)
#火箭方程 #质量比 #比冲 #多级火箭
什么是火箭发动机的“比冲”（specific impulse）？它如何衡量性能？
What is the specific impulse of a rocket engine, and how does it measure performance?
比冲 I_sp 是单位推进剂重量流量产生的推力，单位为秒，数值越大效率越高。化学火箭的 I_sp 约250–450 s，离子推力器可达数千秒但推力很小，因此比冲与推力需权衡。
Specific impulse I_sp is the thrust per unit propellant weight flow, in seconds; a higher value means greater efficiency. Chemical rockets have I_sp of about 250–450 s, while ion thrusters reach thousands of seconds but with very low thrust, so I_sp and thrust must be traded off.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
美国航空航天学会（AIAA）；Sutton & Biblarz《火箭推进基础》
American Institute of Aeronautics and Astronautics (AIAA); Sutton & Biblarz, 'Rocket Propulsion Elements'
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780665590955 (2002)
#比冲 #火箭发动机 #推进效率 #离子推力器
什么是『音障』，飞机如何突破它？
What is the 'sound barrier,' and how do planes break it?
音障是飞机接近音速时激波导致阻力剧增、操控变难的现象。后掠翼、更强动力和面积律等设计让飞机在超音速下仍可控，从而稳定跨越音速。
The sound barrier is the drag and control difficulty from shock waves near Mach 1. Swept wings, more power, and area ruling let aircraft stay controllable and cross into supersonic flight.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
Anderson，《高超声速与高温气体动力学》（第2版）
Anderson, 'Hypersonic and High-Temperature Gas Dynamics' (2nd ed.)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL1993330W：Hypersonic and high-tem
#音障 #激波 #超音速
伯努利原理如何解释机翼产生升力？
How does Bernoulli's principle explain lift generation by a wing?
翼型使上表面气流速度更快、压强更低，下表面压强相对较高，压强差产生向上的升力，同时气流被向下偏转也通过牛顿第三定律提供升力。升力大小 L = ½ρV²S C_L，其中 C_L 为升力系数。
An airfoil makes the upper flow faster and lower in pressure while the lower surface stays at higher pressure, and the pressure difference yields upward lift; the downward deflection of air also contributes via Newton's third law. Lift is L = ½ρV²S C_L, where C_L is the lift coefficient.
难度 进阶 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
美国航空航天学会（AIAA）；J.D. Anderson《空气动力学基础》
American Institute of Aeronautics and Astronautics (AIAA); J.D. Anderson, 'Fundamentals of Aerodynamics'
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL20903326W：Fundamentals of aerody
#伯努利原理 #升力 #翼型 #升力系数
固体火箭发动机和液体发动机各适合什么场合？
What are solid and liquid rocket motors each suited for?
固体发动机把燃料和氧化剂预先浇铸成药柱，结构简单、可长期贮存、随时点火，推力大而集中，适合助推器和需要快速反应的场合。但它点火后难以关机和调节推力，比冲一般偏低。液体发动机可节流、可多次启动、比冲高，适合入轨与深空机动，代价是系统复杂、需要低温或有毒推进剂管理。
A solid motor has fuel and oxidiser cast together as a grain, giving a simple structure that can be stored for years, ignited on demand, and delivering large concentrated thrust, which suits boosters and quick-reaction missions. Once lit it is hard to shut down or throttle, and specific impulse is usually lower. Liquid engines can be throttled and restarted and offer higher specific impulse, suiting orbit insertion and deep-space manoeuvres, at the cost of complexity and handling of cryogenic or toxic propellants.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
Sutton & 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)
#固体火箭 #液体火箭 #推进选型
飞机的『攻角』是什么，和升力有何关系？
What is 'angle of attack,' and how is it linked to lift?
攻角是机翼弦线与来流方向的夹角。在一定范围内增大攻角会提高升力，但超过临界值气流分离、升力骤降并失速，所以飞行员需控制攻角。
Angle of attack is the angle between the wing chord and the airflow. Within a range, more angle means more lift, but past a critical value flow separates and lift collapses—stall—so pilots manage it.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
Anderson，《空气动力学基础》（第6版）
Anderson, 'Fundamentals of Aerodynamics' (6th ed.)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787516504413（豆瓣书目条目: 空气动力学基础）
#攻角 #升力 #失速
什么是“马赫数”？超音速飞行会面临哪些特殊挑战？
What is the Mach number, and what special challenges arise in supersonic flight?
马赫数 Ma = 飞行速度 / 当地音速。当 Ma > 1 进入超音速后会产生激波、波阻剧增、机体严重气动加热并伴随音爆，因此需采用后掠翼、加力燃烧和耐热材料。
The Mach number is Ma = flight speed divided by the local speed of sound. Once Ma > 1, shock waves form, wave drag rises sharply, the airframe heats severely, and a sonic boom occurs, so swept wings, afterburners, and heat-resistant materials are required.
难度 进阶 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
美国航空航天学会（AIAA）；J.D. Anderson《现代可压缩流》
American Institute of Aeronautics and Astronautics (AIAA); J.D. Anderson, 'Modern Compressible Flow'
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL1993329W：Modern compressible flo
#马赫数 #超音速 #激波 #波阻
为什么现代飞机常采用“放宽静稳定 + 电传操纵”设计？
Why do modern aircraft often use relaxed static stability with fly-by-wire control?
放宽静稳定度可减少配平阻力、提高机动性，但飞机本身趋于不稳定。电传操纵由飞行控制计算机持续微调舵面来稳定飞行，因而在战斗机与客机（如 A320）上广泛应用。
Relaxed static stability reduces trim drag and improves maneuverability, but makes the airframe naturally unstable. Fly-by-wire systems use flight-control computers to continuously trim the control surfaces and stabilize the aircraft, so the approach is widely used in fighters and airliners such as the A320.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
美国航空航天学会（AIAA）；Etkin & Reid《飞机飞行动力学》
American Institute of Aeronautics and Astronautics (AIAA); Etkin & Reid, 'Dynamics of Flight: Stability and Control'
独立核验依据 · Independent verification: 核验依据 1 ARCHIVE 标识 dynamicsofflight0000etki：Dynamics of flight :
#放宽静稳定 #电传操纵 #配平阻力 #飞行控制
空间碎片为什么危险，卫星退役后怎么处理？
Why is space debris dangerous, and what happens to satellites after retirement?
低轨物体相对速度可达每秒十公里量级，一颗厘米级碎片的动能就足以击穿舱壁。为减少碎片增长，低轨卫星寿命末期要主动降低轨道，让大气阻力在数十年内使其再入烧毁；同步轨道卫星则抬升到坟墓轨道。国际准则还要求钝化剩余能源，避免贮箱和电池爆炸产生新碎片。
Relative speeds in low orbit reach around ten kilometres per second, so even a centimetre-sized fragment carries enough energy to punch through a spacecraft wall. To limit debris growth, low-orbit satellites lower their orbit at end of life so atmospheric drag causes reentry and burn-up within a few decades, while geostationary satellites are boosted into a graveyard orbit. Guidelines also require passivating stored energy so tanks and batteries cannot explode and create new fragments.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-02
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Curtis，《轨道力学》（第4版）
Curtis, 'Orbital Mechanics for Engineering Students' (4th ed.)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787030253231（豆瓣书目条目: 轨道力学）
#空间碎片 #离轨 #航天可持续
发射场为什么多选在低纬度靠海的地方？
Why are launch sites often at low latitude and near the sea?
纬度越低，地球自转带来的向东初速度越大，向东发射赤道轨道时可以白赚一部分速度，节省推进剂。靠海则让残骸和一二级落区落在无人海域，降低对地面的风险，同时便于用船运输超大直径箭体。发射极地或太阳同步轨道时纬度优势减小，但落区安全依然重要。
The lower the latitude, the greater the eastward speed given free by Earth's rotation, so launching east into an equatorial orbit gains velocity and saves propellant. A coastal site lets spent stages and debris fall into empty ocean, reducing risk to people, and makes it easier to ship oversized rocket sections by sea. For polar or sun-synchronous orbits the latitude benefit shrinks, but safe drop zones still matter.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
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Sutton & 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)
#发射场 #自转助力 #落区安全
星敏感器是怎么帮卫星判断自己朝哪个方向的？
How does a star tracker tell a satellite which way it is facing?
星敏感器用小型相机拍下一小片天区，提取亮星的相对位置构成图形特征，再与星载星表比对匹配。匹配成功后即可解出相机光轴在惯性空间的指向，精度可达角秒级。它是卫星最精确的绝对定姿手段，但被太阳或地球边缘照射时会短暂失效，需要陀螺接续。
A star tracker photographs a small patch of sky, extracts the relative positions of bright stars as a pattern, and matches that pattern against an onboard star catalogue. A successful match yields the camera's pointing in inertial space, with accuracy down to arcseconds. It is a satellite's most precise absolute attitude reference, but glare from the Sun or Earth limb can blind it briefly, so gyroscopes bridge the gap.
难度 进阶 · 适合 大众
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。
Clarke 1945（地球静止轨道）；Wertz
Clarke (1945, geostationary orbit); Wertz, Space Mission Analysis
#星敏感器 #定姿 #航天导航
地球同步轨道为什么偏偏在约三万六千公里高？
Why is geostationary orbit at about thirty-six thousand kilometres?
轨道越高，绕地球一圈的周期越长。当轨道半径使周期恰好等于地球自转一周的时间时，卫星就与地面同步，这个高度约为三万五千八百公里。若同时把轨道放在赤道面且接近圆形，卫星在地面看来就固定在天上一点，非常适合通信和气象观测。
The higher the orbit, the longer it takes to circle the Earth. When the radius makes the period exactly equal to one rotation of the Earth, the satellite keeps pace with the ground, and that altitude is about thirty-five thousand eight hundred kilometres. If the orbit also lies in the equatorial plane and is nearly circular, the satellite appears fixed at one point in the sky, which is ideal for communications and weather watching.
难度 进阶 · 适合 大众
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。
Clarke 1945（地球静止轨道）；Wertz
Clarke (1945, geostationary orbit); Wertz, Space Mission Analysis
#同步轨道 #轨道周期 #通信卫星
飞机『失速』是指发动机熄火吗？
Does aircraft 'stall' mean the engine quits?
不是。失速指机翼攻角过大、气流分离导致升力突然大幅丧失，飞机下坠，发动机未必停止。恢复方法是降低机头、减小攻角让气流重新贴附。
No. Stall means the wing's angle of attack is too high and flow separates, abruptly losing lift—the plane drops, but engines may still run. Recovery is to lower the nose and reduce angle to reattach flow.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
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Anderson，《Fundamentals of Aerodynamics》（第6版）；FAA《Airplane Flying Handbook》(FAA-H-8083-3C) 高空运行章
Anderson, 'Fundamentals of Aerodynamics' (6th ed.); FAA 'Airplane Flying Handbook' (FAA-H-8083-3C), high-altitude operations
独立核验依据 · Independent verification: 核验依据 1 ISBN 9781947192898 (2021)
#失速 #攻角 #气流分离
机翼到底是怎么产生升力的？
How does a wing actually generate lift?
机翼上表面弯曲、流线更密、流速更快、压强更低，下表面压强相对更高，形成向上的压力差；同时气流被向下偏转，按动量守恒也产生向上的反作用。伯努利与牛顿两种解释其实是同一件事的两面。
The curved upper surface makes flow faster and lower-pressure while the lower surface stays higher-pressure, creating an upward pressure difference; at the same time air is deflected downward, giving an upward reaction by momentum conservation. Bernoulli and Newton describe the same phenomenon from two sides.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
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Anderson《空气动力学基础》(Fundamentals of Aerodynamics)；美国 NASA Glenn 研究中心《升力入门》
Anderson, 'Fundamentals of Aerodynamics'; NASA Glenn Research Center, 'Beginner's Guide to Aerodynamics'
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL20903326W：Fundamentals of aerody
#升力 #伯努利 #压力差 #动量守恒
卫星的自旋稳定和三轴稳定有什么区别？
What is the difference between spin-stabilised and three-axis stabilised satellites?
自旋稳定让整星像陀螺一样绕一个轴旋转，靠角动量抵抗扰动，结构简单可靠，但载荷指向受限，太阳能板利用率低。三轴稳定用反作用轮和推力器分别控制三个轴，星体可以稳定对地或对目标指向，适合成像和通信卫星，代价是控制系统复杂、需要更多部件。
A spin-stabilised satellite rotates about one axis like a gyroscope, resisting disturbance with its angular momentum; it is simple and robust but payload pointing is limited and solar cells are poorly used. Three-axis stabilisation uses reaction wheels and thrusters to control each axis, letting the body hold a steady attitude toward Earth or a target, which suits imaging and communication satellites at the cost of a more complex control system and more hardware.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-02
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Wertz《空间任务分析》；卫星稳定
Wertz, Space Mission Analysis and Design; satellite stabilization
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL19903182W：Space mission analysis
#姿态稳定 #角动量 #卫星平台
现代飞机为何大量使用复合材料？
Why do modern aircraft use composites heavily?
碳纤维等复合材料比强度高、抗疲劳、耐腐蚀且可整体成形，能显著减轻机重、降低油耗并减少金属疲劳问题，波音787和空客A350机身大量采用。
Carbon composites are light, fatigue- and corrosion-resistant, and can be molded in large pieces, cutting weight and fuel burn and avoiding metal fatigue—used widely on the 787 and A350.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
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Callister,《Materials Science and Engineering: An Introduction》Wiley 多版
W. D. Callister Jr., Materials Science and Engineering: An Introduction, Wiley, various editions
独立核验依据 · Independent verification: 核验依据 2 ISBN 978-1-119-45520-2 (Global Ed.) / 978-1-119-45391-8
#复合材料 #减重 #航空
液体火箭为什么要用涡轮泵而不是直接用高压气瓶挤压推进剂？
Why do liquid rockets use turbopumps instead of squeezing propellant out with high-pressure gas?
挤压式供应要求整个推进剂贮箱承受与燃烧室相当的压力，贮箱壁必须很厚，结构质量代价巨大。涡轮泵在低压贮箱和高压燃烧室之间做增压，贮箱可以做得很轻，因此大型火箭都用泵压式。挤压式结构简单可靠，仍用于小推力的姿控和上级发动机。
Pressure-fed supply requires the whole propellant tank to withstand roughly chamber pressure, so tank walls must be thick and the structural mass penalty is severe. A turbopump raises pressure between a low-pressure tank and a high-pressure chamber, letting the tanks be very light, which is why large rockets are pump-fed. Pressure-fed systems remain simple and reliable, so they are still used for small attitude-control and some upper-stage engines.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
Sutton & 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)
#涡轮泵 #推进剂供应 #结构质量
飞机起飞降落时放下襟翼有什么用？
Why do planes extend flaps during takeoff and landing?
襟翼是机翼后缘可向下展开的活动面，能增大机翼面积和弯度，从而提高升力并增大阻力，让飞机在较低速度下仍能安全起降、缩短滑跑距离。
Flaps are hinged surfaces on the trailing edge that increase wing area and camber, boosting lift and drag so the plane can take off and land safely at lower speeds with shorter rolls.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
Anderson，《空气动力学基础》（第6版）
Anderson, 'Fundamentals of Aerodynamics' (6th ed.)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787516504413（豆瓣书目条目: 空气动力学基础）
#襟翼 #升力 #起降
卫星在阴影区里靠什么继续工作？
What keeps a satellite working while it is in Earth's shadow?
低轨卫星每绕地球一圈就有三分之一左右时间进入地球阴影，太阳能板发不出电。这段时间由蓄电池供电，出影后太阳能板一边供电一边给电池充电。因此电池的充放电循环次数极多，寿命设计和热控是关键，深空探测器距离太阳太远时则改用同位素电源。
A low-orbit satellite spends roughly a third of each orbit in Earth's shadow, where its solar arrays produce nothing. Batteries carry the load during that period, and once back in sunlight the arrays both power the spacecraft and recharge the batteries. The batteries therefore endure a very large number of charge-discharge cycles, making life design and thermal control critical, while deep-space probes too far from the Sun use radioisotope power instead.
难度 入门 · 适合 大众
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。
Clarke 1945（地球静止轨道）；Wertz
Clarke (1945, geostationary orbit); Wertz, Space Mission Analysis
#卫星电源 #蓄电池 #地影