jamin_g t1_iqx19xh wrote
Reply to comment by JagerBaBomb in After DART: Using the first full-scale test of a kinetic impactor to inform a future planetary defense mission by EricFromOuterSpace
Lots of assumptions as to the composition of the thing we're hitting.
The impact into a bowling ball vs an exercise ball is going to be very different.
Khazahk t1_iqx5ixm wrote
Well for one thing the exercise ball would be slightly easier to hit size wise.
Next question.
SmugBoxer t1_iqxf2g0 wrote
No need sir, you've been promoted to Head Mathematician. We're lucky to have access to a man of your caliber and scrutiny.
jeffh4 t1_iqxn4zm wrote
More like the impact into a loose pile of irregular boulders. The last couple of photos were stunning and unexpected. No smooth surface visible. Just jagged and loosely interlocked rocks.
Back to the chalkboard, folks! We need to explore the real possibility the probe emerged out the back of the asteroid without losing all of its momentum.
evanc3 t1_iqy56gx wrote
What do you mean? It looks extremely similar to all of the other asteroids that we've landed on/ photographed recently...
Mediumcomputer t1_iqz3705 wrote
Could one make a shaped charge or cone shaped nuke? I feel like that would deflect a pile of barely held together rocks better than our own Little Rock with solar panels on it
ciroluiro t1_iqy8evy wrote
I would imagine that the composition would be less of a concern than knowing the exact mass of the asteroid.
A collision in space is as good of a scenario you could get in terms of applying conservation of momentum. Then, knowing that the worst case scenario is a plastic collision (because the probe going through the asteroid completely is very much impossible), you could know with very good certainty the final momentum (assuming we have fairly precise and accurate information on the velocity of both objects). I'm purely speculating as I haven't looked into the mission, but I also doubt the scientist expected a best case scenario of a bounce from the asteroid.
VolvoRacerNumber5 t1_iqywdop wrote
I think everyone here is ignoring how material gets ejected by the impact. They know the momentum of both the spacecraft and asteroid very well. There's nothing new the impact will show in regards to that very basic momentum conservation problem.
What they are actually trying to characterize is the way debris is ejected by the impact. This ejecta carries off its own momentum and can impart a significant additional momentum to the asteroid.
ciroluiro t1_iqz47cw wrote
But that's kinda my point. Anything ejected would only "push off" the asteroid and help nudge it off course, given that they mostly get ejected either in the opposite direction to the spacecraft, or perpendicularly in a roughly even manner (this last one is speculation on my part since I imagine it depends heavily on the angle of impact and possibly more things I don't know, but I don't think it's a wild assumption)
Impiryo t1_iqywgoc wrote
There was a huge amount of ejected mass from the collision - that is likely the majority of the momentum change, and what we are measuring.
Plastic vs elastic collisions fail when explodey stuff happens.
ciroluiro t1_iqz3jul wrote
Unless the ejected mass went somehow forward, I don't see how that would steal momentum from the asteroid. Maybe if the ejected mass went perpendicular in a manner was not even in all directions? Kinda stretching it.
Anyway, explodey stuff would only help, not hurt.
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