Development of indigenous linear low-density polyethylene film and other related techniques for heavy-load balloons in India

A new grade of balloon film extruded out of LLDPE resin with Butene as comonomer and Cold Brittle Point (CBP) at −88°C was extruded and successfully flight tested with a 25 micron single shell 53,000 Cu.M. balloon carrying 330 Kg. payload to 33 Km. altitude. We have also produced superior LLDPE film out of Dowlex 2045 Dow Chemicals resin with Octene as comonomer, which has the cold brittle point lower than −90°C and superior mechanical properties at low temperatures. A high pressure hydrogen filling system capable of delivering 2200 Cu.Ft. of hydrogen per minute has been commissioned and successfully utilised in 11 flights. With this new filling system, the inflation time is drastically reduced by over 50% thereby reducing the duration of pre-launch stresses on the ground bubble. After the acceptance of our revised design criteria for balloons to be flown from equatorial latitudes by M/s.Winzen International Inc., U.S.A., 41 flights have been made, out of which 36 have been successful giving us a success record of 88%. Out of the 5 failures, 3 have been float failures with gross inflations exceeding 1950 kg, for which launch spool damage is a suspect. To reduce the spool damage, the shell thickness of the subsequent balloon was increased to 20.32 microns from 17.78 microns and the flight was a success. For further reducing the possibility of launch spool damage, a larger diameter spool is being designed.