Parachute load test with an unexpected outcome

Last Thursday it was time to determine once and for all how much the parachutes we use in the landing system could handle. Having failed to break them in both the car towing test and the actual drop test, me and our supervisor Gunnar Tibert resorted to more brutal methods.

One of the 70″ parachutes was hung upside down from a hook in the Structures Lab at KTH, supported by a single line of paracord which was to brake the fall. This is the same type of cord that was successfully used in the drop tests above Esrange. The parachute was loaded with about 19 kg of extra load, and dropped with 1.5 m of slack paracord.

Sometimes it's best to use what you have closest at hand! 19 kg of old newspapers have just the right density to fill out the parachute nicely.

Much to our surprise, it turned out the paracord, which we thought was rated to the equivalent of a couple of hundred kilograms in force, was the weakest link:

View from the hook of the crane, filmed with the GoPro HD Hero.

420 FPS high speed footage shot using a Casio consumer camera. This doesn’t show the paracord breaking, but is cool nontheless!

Right now we’re trying to determine the speed right before and after the line broke so we can calculate the force in the cord. At any rate, it is likely we will switch this cord for the real system to be sure that the same won’t happen during our flight! However, the cord still needs to be flexible so the shock to the experiment isn’t too great.

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