A document describes a 5.5-m-diameter, helium-filled balloon designed for carrying a scientific payload having a mass of 44 kg for at least six days at an altitude of about 55 km in the atmosphere of Venus. The requirement for floating at nearly constant altitude dictates the choice of a mass-efficient spherical super-pressure balloon that tracks a constant atmospheric density. Therefore, the balloon is of a conventional spherical super-pressure type, except that it is made of materials chosen to minimize solar radiant heating and withstand the corrosive sulfuric acid aerosol of the Venusian atmosphere.
The shell consists of 16 gores of a multilayer composite material. The outer layer, made of polytetrafluoroethylene, protects against sulfuric acid aerosol. Next is an aluminum layer that reflects sunlight to minimize heating, followed by an aluminized polyethylene terephthalate layer that resists permeation by helium, followed by an aromatic polyester fabric that imparts strength to withstand deployment forces and steady super-pressure. A polyurethane coat on the inner surface of the fabric facilitates sealing at gore-to-gore seams. End fittings and seals, and a tether connecting the end fittings to a gondola, are all made of sulfuric-acid-resistant materials.
This work was done by Jeffrey Hall, Viktor Kerzhanovich, and Andre Yavrouian of Caltech; Debora Fairbrother and Magdi Said of NASA-Wallops Flight Facility; and Chuck Sandy and Thad Fredrickson of ILC Dover, Inc. for NASA's Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Physical Sciences category. NPO-43852
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Balloon for Long-Duration, High-Altitude Flight at Venus
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Overview
The document, titled "Balloon for Long-Duration, High-Altitude Flight at Venus" (NPO-43852), outlines the development of a superpressure balloon designed for extended missions in the harsh atmospheric conditions of Venus. Developed by NASA's Jet Propulsion Laboratory, this innovative balloon aims to carry a 44 kg payload while maintaining a near-constant altitude of 55 km.
Key features of the balloon include a 16-gore construction with taped overlap seams, utilizing materials that exhibit outstanding resistance to sulfuric acid, a prevalent component of Venus's atmosphere. The outer layer is made from second-surface metallized Teflon, which has a low solar absorptivity/emissivity ratio, helping to manage thermal conditions. The balloon's design incorporates a robust structural safety factor of 4.6 for a baseline two-day mission and approximately 3.3 for a six-day bonus phase, accounting for potential extreme solar heating and pressure excursions.
The balloon's end fittings are constructed from hastelloy, a high-strength nickel superalloy resistant to sulfuric acid, ensuring durability and reliability. A Viton O-ring provides a gas and acid seal at the junction between the metal fittings and the balloon material. The tether connecting the balloon to the gondola is made from Spectra, a high-strength fiber also resistant to sulfuric acid.
The design process emphasizes minimizing engineering and testing costs by using a common design for two balloons. The balloon is engineered to tolerate 85% concentration sulfuric acid aerosols, with all exposed surfaces treated with acid-resistant materials. The design also incorporates a safety factor of at least 2.0 for material strength, addressing uncertainties in environmental conditions.
The document highlights the balloon's capability to drift to the illuminated side of Venus, where it will be subjected to solar heating effects. The engineering team has developed a conservative model to estimate peak balloon temperatures and pressure excursions, ensuring the balloon can withstand the worst-case scenarios during its mission.
Overall, this technical support package provides a comprehensive overview of the balloon's design, materials, and expected performance, showcasing NASA's commitment to advancing aerospace technology for future exploration of Venus and beyond.
