#  Experimental Results 

 



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 Unconstrained Hydrojet Powered Mantle Motion

In order to determine a rough order of magnitude of the velocity a hydrojetting mechanism could achieve, the test setup was modified by removing the load cell. Using the high speed camera, frame by frame motion of the mantle was recorded and can be observed in the figure below. From this high speed imagery, velocimetry can be performed to determine the velocity of the mantle. The maximum velocity of the mantle and bladder is 200 in s-1 or 0.5 m s-1 . It should be noted that this bladder burst during the test as the high velocity mantle pulled the thin walled silicone bladder into the sharp edge of the test stand holding it in place. Careful observation of the T=20 ms frame shows the bladder’s contact with the test stand. Based on the propagation of gas in T=40ms, it is clear that this was the cause of the failure.

The flow meters indicate a hydrogen gas input of 189.69 scc(standard cubic centimeters) at STP. Using the ideal gas law, the total number of moles of hydrogen gas is estimated to be 0.0078 moles. Using the same method on the oxygen flow meter resulted in the expected 0.0039 moles, exactly half that of the hydrogen gas. By back calculating the number of moles of gas and using 80% efficiency of our fuel cells, the energy input to the system is 3.54 kJ. Running this combustion in Europa’s ocean will take slightly less than 1 hour with a 1 watt electrodynamic tether.

   ![(A) High Speed Frames in 10ms Increments of Unrestrained Motion of Mantle (B) Velocity vs Time of Mantle (C) Mantle Initial Mounting Configuration](/sites/g/files/omnuum4601/files/styles/hwp_1_1__720x720_scale/public/srt_competition_2016/files/expphotosabc.jpg?itok=Ph9BFxs4) 

 

(A) High Speed Frames in 10ms Increments of Unrestrained Motion of Mantle (B) Velocity vs Time of Mantle (C) Mantle Initial Mounting ConfigurationIt is worth noting that the bladder inside the mantle as indicated in Figure (c) is approximately 4 inches long initially and cylindrical in shape with 0.3175 cm wall thickness. As Figure (c) shows, the bladder is not in a cylindrical shape at the beginning of the test due to acting of the water on the bladder. This indicates that even the small pressure difference between the bottom and top of the mantle, a 5 cm height difference, causes an uneven expansion of the bladder. This expansion of the bladder could be caused by three different sources (i) initial alignment of the bladder due to gravity acting on the higher density water that vectors expansion upwards (ii) buoyant forces acting on the bladder during the gas expansion phase of combustion resulting in upward motion and/or (iii) the local high pressures in the water tank experimental setup.

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