NASA高空气球的研究及其进展

高空气球是一种可以实现平流层飞行的无动力浮空器。文章重点从气球的结构、蒙皮材料、热特性研究及试飞试验等方面介绍了NASA高空气球的研究及其进展,为中国高空气球的研究发展提供参考。     

金星气球环境分析与热动力研究

分析了金星独特的大气环境,归纳了影响金星气球飞行的主要环境因素,并建立了数学模型.依据金星气球的投放、飘浮程序,设计了金星原型氦气球,设计驻留高度为35km.建立了金星气球热动力仿真平台.计算结果表明:金星气球在30~40km高度释放,可快速到达驻留高度并作长期飘浮;金星气球系统的温度范围为440~520K,最大速度低于10m/s.这为进一步开展对金星气球的研究提供了依据.      

Feasibility study of a sea-anchored stratospheric balloon for long-duration flights

Sea-anchored balloons are stratospheric super-pressure balloons that are anchored to the sea. The sea-anchored balloon is a simple system that has the capability for long-duration flights, fixed-point observations, flexible launch windows, easy telemetry links to ground stations, and quick recoveries. Such balloons are not required to fly through the jet stream while tethered to the ground or sea, because the tether is deployed from a reel on the balloon after reaching a floating altitude. In this study, the feasibility of the sea-anchored balloon is investigated, with particular emphasis on the tether strength, balloon altitude, and system mass, based on the present technological level of the tether’s specific strength. Although the wind distribution with altitude is a dominant factor for feasibility, a sea-anchored balloon with an altitude of about 25 km would be feasible if the velocity of the jet stream is sufficiently low. The sea-anchored balloon can be simply flight-tested, since additional ground facilities and special flight operations are not necessary.     

自然形高空气球上升过程形状预测

为研究高空气球在上升过程中的形状变化以及蒙皮应力分布情况，并给气球的结构设计以及强度设计提供一定依据，本文建立了气球上升过程中的热力学模型，同时基于高空气球蒙皮材料具有非线性、黏弹性、各向异性和不能抗压等特点，通过简化气球几何模型，采用最小势能法预测自然形高空气球上升过程中的形状，并分析了气球上升过程中的应力分布情况，气球的应力极值出现在气球顶部和底部，而经向应力的数量级远大于纬向应力；还对比了不同充气量下、不同时刻下气球形状及应力分布情况，为气球设计及工程应用提供了有效计算 方法。     

Observer-based control for the platform of a tethered space robot

This paper addresses the attitude control problem of a space tethered robot platform in the presence of unknown external disturbance caused by a connecting elastic tether. The tether-generated unknown disturbance leads to tremendous challenges for attitude control of the platform. In this work, the perturbed attitude dynamics of the platform are derived with a consideration of the libration of the elastic tether, and then with the purpose of compensating the unknown disturbance, major attention is dedicated to develop a nonlinear disturbance observer based on gyros measurements, after which, an adaptive attitude scheme is proposed by combining the disturbance observer with a sliding mode controller. Finally, benefits from the observer based on an adaptive controller are validated by series of numerical simulations.     

The Mars Environment Analogue Platform long duration balloon flight

The MEAP (Mars Environment Analogue Platform) mission was to fly a stratospheric balloon on a semicircular trajectory around the North Pole in summer 2008. The balloon platform carried the high-resolution neutral gas mass spectrometer P-BACE (Polar Balloon Atmospheric Composition Experiment) as scientific payload. MEAP/P-BACE is a joint project between the Esrange Space Center, Sweden, the University of Bern, Switzerland and the Swedish Institute of Space Physics (IRF), Kiruna, Sweden. Mission objectives were to validate the platform for future long duration flights around the North pole, to validate the P-BACE instrument design for planetary mission applications (conditions in the Earth stratosphere are similar to the conditions at the Mars surface), to study variation of the stratospheric composition during the flight and to gain experience in balloon based mass spectrometry. All objectives were fulfilled.     

Mechanical properties of ANTRIX balloon film and fabrication of single cap large volume balloons

The zero pressure plastic balloons used for high altitude studies are generally made from polyethylene material. Tensile properties of the thin film polymer are the key parameters for material selection due to extremely low temperature of −90 °C encountered by the balloons in the tropopause region during the ascent at equatorial latitudes. The physical and structural properties of the material determine the uniformity of the stress distribution over the entire shell. Load stresses from the suspended load propagate via load tapes heat sealed along with the gore seals as per the balloon design. A balance between this heat seal strength and the film strength is a desirable property of the basic resin in terms of the bubble strength, gauge uniformity, and long-term storage properties. In addition, the design of the top shell of the balloon and its stress distribution play an important role since only a fraction of the balloon is deployed during the filling operation and the ascent. In this paper we describe the mechanical properties of the ‘ANTRIX’ film developed by us and the optimized design of single cap balloons, which have been successfully used in our experiments over the past 5 years.     

高空系留气球建模与稳定性分析

平流层高空系留气球是典型的无控制欠阻尼自治系统,因此平台本身应当具有较好的稳定性,然而该系统的线性化模型含有零特征根,导致经典的Lyapunov第一方法难以从理论上获得其稳定性结论.从一般刚体的Newton-Euler方程出发,根据刚体对任一点的平动和转动方程,建立基于广义坐标的高空系留气球二阶非线性动力学模型,并针对Lyapunov方法证明稳定性的局限性,从能量的角度运用拉格朗日定理证明了高空系留气球的稳定性,数值仿真结果与理论结果一致.     

圆及椭圆轨道释放绳系子星的方法研究

研究绳系卫星系统质心沿椭圆轨道运动时，子星释放的最佳初始条件，运用变量替代简化动力学控制方程；对圆轨道运动的母星，采用轨道转移方法释放子星，计算弹射变轨参数及过渡轨道终了真近点角。本文取消母星质量远大于子星质量的假设，考虑子星释放过程中绳系卫星系统质心随子星运动的变化，所得结果更具有普遍意义。数值模拟结果表明，所述方法的有效性。     

临近空间串联气球系统设计与特性分析

目前,零压气球和超压气球固有的不足限制了高空气球的飞行能力。提出了 1种无需消耗压舱物和浮升气体即可实现昼夜高度自稳定且能够长时间迂回飞行的临近空间串联气球系统。结合了 2种气球的优点,避开了现阶段高空气球发展遇到的困难。建立了昼夜飞行高度一定的串联气球系统的数学模型,设计了能够利用准零风层风场条件实现迂回飞行的串联气球系统,通过与单一零压气球系统对比,验证了该系统的优势。数值仿真分析了零压气球形状、系统设计高度对超压气球尺寸、最大超压量等关键参数的影响,为设计飞行性能更好的系统提供了重要参考依据。