COLLIDE Results



 Scientific data and their interpretation will be added to this page as it is available or time permitting.  For now, here are some low-resolution captured frames from one of the COLLIDE videotapes to give you a flavor of the data retrieved.  The actual video resolution is higher than what is shown in these captured and compressed frames.

Analysis of the COLLIDE data is nearly complete.  Coefficients of restitution have been computed for all impacts, including those with poor focus and those where the doors did not open.  The results show much lower coefficients of restitution (on the order of 5 per cent) than is predicted by extrapolation of fits to data obtained by other researchers at 1 cm/s with impacts into frosted and smooth ice spheres (Bridges et al. 1984, Hatzes et al. 1988).  The results of COLLIDE are in:       Colwell, J. E., and M. Taylor 1999.  Low Velocity Microgravity Impact Experiments into Simulated Regolith. Icarus  138, 241-248.

  1. IBS 4, Projectile prior to impact.

  2. This is one of the two IBS's which operated flawlessly.
  3. IBS 4, Projectile at impact.

  4. This image shows the ball in contact with the surface of the JSC-1 powder.  The projectile is also visible, as planned, in the mirror. This shows that the projectile fired straight.  Analysis of the image in the mirror after impact will allow a determination of the penetration depth of the projectile into the dust layer.
  5. IBS 4, Projectile after impact with dust smudge.

  6. A smudge of JSC-1 dust is visible on the reflection of the ball in the mirror.  A small amount stuck to the ball on impact.
  7. IBS 4, After the dust tray door closed.

  8. When the door closes, a small layer of dust is peeled up by the door.  Preliminary analysis indicates that this peeling begins at the site of impact, consistent with a small crater rim being created by the impact elevated above the surface of the undisturbed dust layer.
  9. IBS 6, Camera failed to focus.

  10. Although the image is terribly blurred, frame-to-frame comparison shows the door opening and the projectile firing.  It may be possible to retrieve good velocity and coefficient of restitution measurements from this IBS.
     
     
     
    Table of Coefficients of Restitution from COLLIDE*
    IBS Initial Rotation Rate (1/s) Tangential Rebound Velocity (cm/s) Final Rotation Rate (1/s) Tangential Coefficient of Restitution (e)
    1 31 0.39 +/s .02 3.49 +/- 0.24 0.086
    4 37 0.78 +/- .02 2.48 +/- 0.12 0.023
    6 94 4.8 +/- 0.5 Unknown -0.053**
    **This lower limit is based on an assumed final rotation rate of 0.  Because the impact was into a non-
    rotating target, the effective lower limit of e=0 for this impact.



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* Exerpted from the Collisions Into Dust Experiment - 2 Science Requirement Document by Dr. Josh Colwell, LASP, Boulder Colorado, 28 January 1999, pp.11