Page 25 - Mike's published articles

TABLE 1. Parameters Used in the Calculation of Escape Velocities
HIGH SPEED INK AGGREGATES 7
Dl
Fragment size
Impact area
0.05–0.2 mm 10–100 mm
8 ⇥ 1013 3 ⇥ 1011 m2
Table 1 shows a range of parameters taken from the photomicrographs, which yields a range of impact velocities for the above penetration depths (0.05 and 0.2 mm):
The lower end impact velocities, below 5 ms1, (which correspond to the larger mass, lower kinetic energy aggregates) will result in minimal surface damage on the glass, if any. This may account for the image in Figure 3a where it appears to show tattoo aggregates on the glass surface. The upper end of these impact velocities appears to be rather high but they are theoretically possible given the explosive nature of photomechanical reactions and the very small mass of the particles. The range of ink fragment masses will inevitably be large yielding a large range of kinetic energies, and hence escape velocities. However, given the number of assumptions in this very rough calculation the actual velocities may be in a much larger range than shown above.
Given that Ready [22] observed velocities around 10,000 ms1 of ejecta from an aluminium target it appears the above calculations are in the same range. It should be noted that these calculations are based on the impact kinetic energies. The kinetic energy of individual ink particles will be higher as they leave the donor site but the surrounding dermal collagen will inevitably absorb some of that energy, thereby slowing down those aggregates.