Estimating the Deployment Pressure in Pumpkin Balloons
Estimating the Deployment Pressure in Pumpkin Balloons
复制标题
估计南瓜气球的展开压力
DOI：
10.2514/1.c031083
复制
发表时间：
2010
影响因子：
2.2
通讯作者：
K. Brakke
中科院分区：
文献类型：
--
作者：
F. Baginski;K. Brakke
阻碍高空重型南瓜气球系统发展的一个令人烦恼的难题是，该系统能够可靠地展开成所需的对称形状。根据2007年27米直径200戈尔的南瓜气球膨胀试验的经验结果，NASA的气球项目办公室在2008年成功地部署了南瓜：Flight 586-NT， 200万立方英尺的200戈尔设计，和Flight 591-NT， 600万英尺200戈尔设计。先前对应变对称浮子形状的稳定性分析得出了有关部署的部分信息。在漂浮条件下发现有大量不稳定模式的气球也被发现有部署问题。问题是，一个南瓜气球在多大的压力下会形成一个循环对称的形状（不一定是完全形成的形状）？对一系列轴对称上升形状的仔细研究揭示了压差与不稳定模态数量之间的相关性。本文给出了可用于估算部署压力的准则。为了约束问题，考虑了顶端板拟合的固定边界、约束边界和自由边界条件。研究发现，固定条件和约束条件下的稳定性结果几乎相同，因此部署压力的估计策略称为部署路径画像。部署压力dep定义为最小的最低点压力，其中无顶边界条件产生两个不稳定模态，顶固定边界条件不产生不稳定模态。通过将基于部署路径图的部署压力分析预测与2007年586-NT航班和591-NT航班膨胀测试期间记录的部署压力进行比较，验证了该方法的有效性。观测到的部署压力与分析预测结果非常吻合。这是评估部署压力的第一个基于分析的方法。
A vexing conundrum that has hindered the development of a high-altitude heavy-lift pumpkin balloon system is the system’s ability to reliably deploy into the desired symmetric shape. With design strategies honed by empirical results from inflation tests in 2007 using 27-m-diam 200-gore pumpkin balloons, NASA’s Balloon Program Office executed successful pumpkin deployments in 2008: Flight 586-NT, a 2 million cubic foot 200-gore design, and Flight 591-NT, a 6 million ft 200-gore design. Earlier stability analysis of strained symmetric float shapes yielded partial information regarding deployment. Balloons that were found to have a large number of unstable modes at float conditions were found also to have deployment problems. The question remained, what was the minimum pressure at which a pumpkin balloon would deploy into a cyclically symmetric shape (not necessarily the fully developed one)? Careful examination of a family of axisymmetric ascent shapes revealed a correlation between differential pressure and the number of unstable modes. In this paper, criteria that can be used to estimate the deployment pressure is presented. To bound the problem, fixed-, constrained-, and free-boundary conditions are considered for the top endplate fitting. It was found that the stability results using the fixed and constrained conditions are nearly identical, and so the strategy for estimating the deployment pressure, called the deployment pathway portrait, is as follows. The deployment pressurePDep is defined as the smallest nadir pressurewhere the topfree boundary condition yields two unstable modes and the top-fixed boundary condition yields no unstable modes. The approach is validated by comparing analytical predictions of deployment pressures based on the deployment pathway portrait with the deployment pressures that were recorded during the inflation tests in 2007: Flight 586-NT and Flight 591-NT. Very good agreement between the observed deployment pressures and the analytical predictions was found. This is the first analytical-based approach for estimating the deployment pressure.