[meteorite-list] NEAR landing

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:07 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C8692C5EE6_at_US-Torrance.mail.saic.com>

Sam wrote:

> I do not believe the Spacecraft will rebound off the surface of 433 Eros.

I have to agree with Stuart on this one: I think it's going
to bounce -- perhaps several times before settling. It
depends on many factors:

1. the surface conditions (hard/soft) at the impact site
2. the angle between the velocity vector and the surface
    normal of Eros at the impact site
3. the actual velocity at impact
4. the orientation and CG of the spacecraft relative to
    the velocity vector
5. the rigidity of the spacecraft (particularly at the
    point of contact)

All these factors (and probably more) will determine how
elastic the collision will be. #1 is perhaps the most
important -- if the surface is soft and powdery, the
spacecraft will burrow in a bit, allowing a slightly less
instantaneous deceleration. #'s 2 and 4 will determine
how much of the spacecraft's linear motion gets translated
into rotational motion.

No matter what happens (excluding an explosion due to unspent
propellant -- pretty farfetched), all of NEAR will eventually
settle on the asteroid. Escape velocity for Eros varies
from 3.1 to 17.2 meters per second, depending on how
far you are from the asteroid's CG and axis of rotation. I'm
assuming the landing target (in the saddle?) has an escape
velocity closer to the high end of the range (38.5 mph) than
the low end (6.9 mph). This pretty much rules out any chance
of pieces of NEAR managing to reach escape velocity following
the collision. --Rob
Received on Wed 07 Feb 2001 05:26:43 PM PST