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gFEPWhatIf Spreadsheet for Latex Balloon with nonelastic constraining outer canopy.NASA 1962 Atmospheric model for float height
at 0C,101 kPaAir Density (Kg/m^3)Air Pressure (kPa) Air Temperature (deg K)Gasdensity Kg/m^3Molar Mass g/molHydrogenInputs in Green CellsHeliumPayload weight (Kg);The weight of the payload mass to be carried by the balloonAirLatex Balloon Weight (g)SThe weight of the inner latex balloon (typically 10% greater than its balloon size)Desired Float Height (m)<The desired float height for the balloon+payload combination(R universal gas constant m^3.kPa/mol.KThermal Gain (deg C)WThe estimated temperature of gas inside the balloon above local atmospheric temperatureLifting GasThe chosen lifting gasLifting gas Density (Kg/m^3)8The density of the lifting gas at 0C 101kPa (from table)Lifting gas Molar Mass (g/mol)5The molar mass of the chosen lifting gas (from table)!Mass excluding gas at Launch (Kg)$Weight of Payload + Balloon + Fabric
Free Lift at Launch (Kg)XThe free lift is the amount of extra lift to make the balloon ascend at the desired rateGas Volume at Launch (m^3)@Gas volume needed to lift Payload + Balloon + Fabric + Free Lift 45
mols of gas (mols)AThe amount of gas in mols (needed to calculate internal pressure)$Internal gas pressure at float (kPa)GThe gas pressure inside the balloon at float (P = mols * R * T/ Volume)Differential pressure (kPa)CThe difference between the internal and external pressures at float"Tension in fabric + balloon (kN/m)eCalculated tension assuming spherical shape (based on spherical surface tension/hoop stress equation)Material strength (kN/m)y The working strength of the constraining envelope material must be significantly more than the tension in the row above=Fabric weight (gsm)EThe constraining envelope material's weight in grams per square meterFabric total area (sq m)GThe surface area of the balloon assuming a sphere. (A = 4 * PI() * r^2)Mass of Raw Fabric (Kg)URaw material weight of the envelope based on the surface area and fabric weight (gsm)Fudge Factor*Factor to allow for seams/joins in fabric.Envelope Mass (Kg)EEstimated envelope weight based on raw fabric weight and fudge factorRadius at float (m)dRadius of the balloon to give float volume assuming spherical shape (r = cube_root(V*3/(4 * PI()))Balloon Diameter at float (m)L2 x Radius must be significantly less than the latex balloon burst diameter
Balloon volume at float (m^3){The volume of air the balloon must displace at the float altitude to equal the mass of the Payload + Balloon + Fabric + Gas[u
Total mass at launch (Kg)7Calculated mass of the Payload + Balloon + Fabric + Gas1
This spreadsheet is a what if calculator for a Superpressure balloon comprising an inner latex balloon with external constraining fabric envelope.sThe sheet allows calculation of internal and external pressures and hence tension in the balloon envelope & fabric.'You may enter values in the green cellsTThe values in red cells are calculated from the values you enter in the green cells.!Things to ensure viable solution:0Balloon diameter << latex balloon burst diameter$Surface tension << Material strength
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