A project to develope a balloon system capable of providing scientific measurements for 100-day missions with floating altitude close to 35km transporting payloads of near 1.5 tons.
It is a super-pressure balloon made of a composite fabric (polyester + polyethylene film and fabric) that is filled with Helium and hermetically sealed. Meridional tendons provide additional rigidity to the envelope. The pressure inside the envelop is maintained above the ambient pressure at all times to keep the balloon afloat at a constant altitude. During daytime the internal pressure increases due to solar heating but the volume remains constant due to the rigidity of the envelope. At night the pressure drops due to infrared radiative cooling to space, but as long as the internal pressure remains above the ambient pressure, the balloon stays at the same altitude.
On the future, transported by stratospheric winds around the globe at 30m/s the ULDB would be make a full circunnavegation to Earth in about 2 weeks.
Balloon launched on: 10/23/1999 at 14:50 utc
Launch site: Scientific Flight Balloon Facility, Fort Sumner, (NM), US
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon 60.000 m3 - 6611-2.118-.6/.25/.25-N
Balloon serial number: R2.12-3.0U-01
Flight identification number: 474NT
End of flight (L for landing time, W for last contact, otherwise termination time): 10/23/1999 at 16:08 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 2 h
Landing site: 3 miles S of Melrose, New Mexico, US
The balloon was launched at 14:50 utc on October 23th, 1999 by dynamic method assisted by a launch vehicle and using a auxiliary balloon to help to deploy the Ultra Long Duration Balloon material.
Balloon launch and ascent were nominal but the balloon failed at 26.3 km.
This was the first flight of the 60.000 m3 balloon built with fabric/film material. The goals of the test were to evaluate the balloon itself and to evaluate launch techniques developed for the ULDB.
From these general goals, the flight was classified as a success. The balloon was inflated and launched successfully and much valuable information was gained from the flight. As the balloon was being inflated, one of the tendons could be seen peeling away from the balloon shell in the sub pressure area of the launch bubble.
After a successful launch, the on board cameras were used to find that the tendon had continued to peel away from the balloon shell. As the balloon began to pressurize, the tendon was displaced to a position on top of an adjacent tendon. The continued pressurization of the balloon caused the displaced tendon to roll across the surface of the balloon and carry adjacent tendons with it.
The pressure inside the balloon gradually decreased until the balloon gets fully inflated. The balloon stoped its ascent at 26.3 km and the balloon gas, recovering from the adiabatic expansion, continued to pressurize the balloon until the shell failed after a sudden displacement of nearly twenty tendons.
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