A kinetic impact transfers momentum from a spacecraft to an asteroid, but material blasted away from the surface can add recoil. Researchers describe that enhancement with a beta factor that compares the resulting momentum change with the spacecraft's incoming momentum. A value above one indicates that ejecta contributed to the push, which matters when estimating the mass and speed a deflection mission would need.
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21:54part will be transferred to that other car. Exactly. Which is why then you have to see the driving scenes with like oh yeah to counteract the transfer of momentum. >> Yeah. And that's why that's why the double the double system matters right because like this is a small enough system where like I can I can make that I can make that change discernable. 33 minutes out of 12 hours >> something I can easily measure. Now >> sense >> when it comes to the big thing. Now let's think about the big thing. There's a there's the big system that's moving around the sun. >> Yes. that thing is moving at 23 kilometers per second. >> Okay. >> Mhm. >> The change that my momentum is going to cause is going to be less than a millimeter per second. >> Mhm.
22:34>> That's way harder to measure. >> Yeah. >> And that is what this paper is doing. >> I see. >> This paper is measuring the big one. >> So, let's get into some of the physics that we were talking about. Right. >> Okay. We've got the kinetic impactor which is this idea of um a sort of satellite drone going in making contact and its momentum getting transferred. Now it's not that simple because it's not a simple momentum conservation undergrad problem. Okay. >> Okay. >> It turns out that when I go and make this contact at high velocity at 6 km/s to this little moon that's going to generate shock waves. So the the asteroid is going to ring a little bit. There's going to be an impact crater and
23:15there's also going to be massive ejector that is flying the opposite direction. So imagine my hand is the moon. I make contact, there's going to be ejector flying this way. It's almost like another little rocket impulse that's going the opposite direction. So what I'm going to get is something called momentum enhancement. >> The amount of momentum that gets transferred is not just how much I went in with, but also how much that it threw out. >> Right? Yes. >> And so there's this beta factor called momentum enhancement factor and that's the ratio of the total momentum that was transferred to the target divided by the total momentum that I had. >> If beta is greater than one, that means
23:56that I've actually impacted more momentum than I originally had because the original object has pushed out a bunch of debris in the opposite direction. Does that make sense? >> Yeah. Yeah. So, so what we're saying is um we have an object, our object's coming in to make contact with something. This actually dovetales with the panspermia story we talked about in our last episode about about impacts and that there's ejecta and the velocity by which you hit something can shoot that stuff very very fast and can potentially spread life. But what is the amount of stuff that gets ejected out >> almost creates this additional push in the direction you were already going in addition to the amount of push that you individually as the object was giving.
24:38>> Yes. And that's that enhancement. >> And that's the enhancement, right? >> And so it's really important for us to calculate what this enhancement is because if, >> god forbid, there's an asteroid coming for us. >> Yes. >> Knowing this value of beta is going to be instrumental for figuring out how fast do I need to nudge it, right? How big of the drone does the satellite need to be in order to make contact? How much momentum am I trying to put in there? because the momentum transfer is not just what I'm putting in initially, but it's this beta factor multiplied by the initial momentum. >> So the the the idea here is is when Morgan Freeman is in the classified room talking and someone says, uh, we have an
25:19Ellie, an extinction level event because this rock is coming and they're saying, "Okay, what options do we have?" NASA would be able to come into the room and say because we had our Dart mission where we were able to get real world data about what the momentum enhancement factor >> is. We know that because this trajectory is X Y or Z, we're going to need to send this amount of payload at this speed because the math is mathing. >> Exactly. And now we have all the parameters to make that math math. >> Right. Right. Okay. >> Okay. With the Dart mission, we got a local version of beta,
26:00>> right? >> Yes. >> But let's do a little lesson in undergrad physics. We're going to talk about systems and what are their components. >> Okay. >> Whenever we do um undergrad physics, we always try to think of what is the system that is isolated from the environment that we're trying to work with. >> For example, the earth, sun, moon system. Yes, there's three bodies,
AstrophysicsOrbital MechanicsPlanetary DefensePrecision Measurement