Airbag systems are used for impact attenuation in a wide variety of applications on Earth. As landing systems, they find use on helicopters, UAVs, aerial cargo delivery systems and even the F-111 crew escape capsule. For space applications, airbag systems have been developed and used in a range of terrestrial and extra-terrestrial situations but most famously to cushion the landing impact on the Pathfinder and MER missions to Mars.
Vorticity has developed considerable expertise in the development of both non-vented and vented airbag systems over several projects. This expertise includes functional analysis and modelling of inflation and impact using LS-DYNA, Monte Carlo modelling of landing on simulated planetary terrains, detailed design of the airbag envelope, analysis and specification of inflation systems and retraction / release devices and testing at both Earth atmospheric and low pressure. Our team has conducted successful tests at the NASA low density facilities at Plum Brook and Johnson Space Center.
Airbag attenuation systems function by converting the kinetic energy from the payload into energy stored within the gas contained in the envelope. The energy flow is reversed during the rebound and some of the energy stored in the gas is returned in the form of kinetic energy. If the airbag is sealed during its operation it is called non-vented. The MER and Pathfinder airbags were of this type.
Vented airbags release the gas following compression and therefore remove the stored energy from the system which results in little or no rebound. UAV airbags are typically of this type. The function of vented airbags is very sensitive to ambient pressure. On Earth, when the bag vents, release of a small proportion of the mass of gas reduces the internal pressure to ambient. The motion of the system is highly damped. On Mars nearly all the gas needs to be released to achieve ambient pressure. The airbag system dynamics are very sensitive and a control system that vents different bag segments sequentially is necessary for a successful landing.
Landing Systems Case Studies
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