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.
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IBS
4, Projectile prior to impact.
This is one of the two IBS's which operated flawlessly.
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IBS
4, Projectile at impact.
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.
-
IBS
4, Projectile after impact with dust smudge.
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.
-
IBS
4, After the dust tray door closed.
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.
-
IBS
6, Camera failed to focus.
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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COLLIDE Home Page
* Exerpted from the Collisions Into Dust Experiment - 2 Science
Requirement Document by Dr. Josh Colwell, LASP, Boulder Colorado, 28
January 1999, pp.11
