The DART mission to nudge an asteroid

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Funkworks

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The DART mission has taken off. Its goal is to target an asteroid, crash into it, and make it deviate from its present course.

 

Grog6

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I'm betting a year from now this will be hitting the earth, and I'd love to be on that phone call to Bruce Willis.
"Look I'm an Actor...
 

boomtube-mk2

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Whatever happened to LUCY?
The last I read about it one of the solar panels had problem fully deploying.

Couldn't we just cajole the asteroid into not hitting Earth?
"Come on Dimorphos, you don't really want to collide with Earth; what would all the other asteroids think?"
 

dr wogz

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Does anyone else have the feeling that someone isn't being completely straight with us about this mission?
what do you think the mission is really all about?

Not being rude or trolling.. But am genuinely curious as to what you might think this is about.. Mining? crossed my mind as well.. Planned 'touchdown' on a moving target? also thought of that.. to add a remote device to an asteroid: to weaponize it / make it controllable / make it capable of hitting a specified target?! also thought of that.. :D
 

Joekeyo

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I am usually very enthusiastic about the space program, after all, I am a rocketeer. But if this is only what they say it is, it is a wasteful yawner🥱
 

Funkworks

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If they could get some High-Def. video of the impact, that would be cool.
From today' wikipedia:
"It is accompanied by an Italian Space Agency (ASI) 6-Unit LICIACube flyby Cubesat that will be released 10 days before impact to observe the asteroid and Dart's impact."

On the LICIACube page:
"it plans to take a image every 6 seconds during the DART's impact period

News story:
 

Blast it Tom!

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Knock a train off the track with a BB gun
That's what I'm thinking; I can't imagine that they'll be attempting to do anything like bust it up, and it's tough to imagine a measurable "nudge" - maybe if they impact perpendicular to the path? But I have yet to read up on mission specifics. Mass x velocity squared can represent a lot of energy at interplanetary speeds, but how would it be distributed? What is the mass of the target asteroid? Recall the Osiris-Rex mission to sample an asteroid, the approach speed was very, very slow as the gravity was so slight - but it was still an awfully big chunk of rock to imagine changing it's path with an earth-launched directed energy source - especially if they're only counting on impact energy.
 
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OverTheTop

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I am reading a book currently that discusses a lot of detail about redirect missions for planetary protection. Move it early enough and a small deflection is sufficient. If you are trying to move it to prevent a harmonic return on future orbits it can be sufficient to keep it out of "keyhole" zones which might only require a deflection of a couple of hundred meters or even less. You don't necessarily have to deflect it the width of a planet.

Also current modelling says you get about three times the kinetic deflection energy. The kinetic energy is only about 1/3 of the impulse provided, a plasma stream caused by the impact provides the rest. This mission will validate some of the modelling.
 
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Joekeyo

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Funkworks

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Found a bit of data.

Moon data

moon diam: 160 m
moon radius: 80 m
moon volume: 2,144,660 m3
moon density: 1.7 g/cm3
moon density: 1700 kg/m3
moon mass: 3,645,922,994 kg

Probe data

probe speed: 6.6 km/s
probe speed: 6,600 m/s
probe mass: 610 kg
probe momentum: 4,026,000 kg·m/s
probe energy: 13,285,800,000 J

In case anyone wants to calculate (maybe me later).

 
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OverTheTop

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They’re probably going for a side impact, which will make the moon deviate from its regular orbit.
Based on a quote from your last link (GSFC) I suspect they are going to hit it head-on, directly aiming for the CG (so no induced rotation). It looks like they are looking at the orbit relative to its companion and this makes sense as it it should be quite a sensitive tool to measure the changes. Measuring changes in the heliocentric orbit of the pair around the sun is more difficult and doesn't make sense. Remember it is the \( {\Delta}V \) in line with the orbit that raises or lowers the orbit. Pushing on the side just changes the eccentricity I think. They are going for a head-on slam and estimating a 1.4% decrease in orbital period (lowering of relative orbit).
 
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aerostadt

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The mathematics of orbital mechanics shows that a small Delta V in one part of an orbit can make a big difference later in another part of the orbit.
 

OverTheTop

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The mathematics of orbital mechanics shows that a small Delta V in one part of an orbit can make a big difference later in another part of the orbit.
Yes, a small \( {\Delta}V \) adjustment at apoapsis has a greater effect on the orbit than if applied elsewhere.
 

ThirstyBarbarian

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I saw something on this last night. The main asteroid has a small “moon” asteroid orbiting it. And the orbit of the moon around the main asteroid is known very precisely. So the impact of DART on the small moon asteroid is going to cause an extremely small change in the moon’s velocity. EXTREMELY small. I don’t recall exactly what he said, but a remember the words “about half a millimeter”, so maybe .5mm per second? Per hour? I don’t really know. But apparently it’s enough to cause a measurable change in the orbit of the moon around the main asteroid. This is just a demonstration project, so as long as the change is measurable, the experiment will provide data, even if there’s not a practical application at this scale.

The other thing the guy mentioned was that as a practical matter, if we want to save the earth from an asteroid impact, the best way would be to know years in advance and just deflect it a tiny bit. It really doesn’t need to be very much.
 

Funkworks

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Based on a quote from your last link (GSFC) I suspect they are going to hit it head-on, directly aiming for the CG (so no induced rotation). It looks like they are looking at the orbit relative to its companion and this makes sense as it it should be quite a sensitive tool to measure the changes. Measuring changes in the heliocentric orbit of the pair around the sun is more difficult and doesn't make sense. Remember it is the \( {\Delta}V \) in line with the orbit that raises or lowers the orbit. Pushing on the side just changes the eccentricity I think. They are going for a head-on slam and estimating a 1.4% decrease in orbital period (lowering of relative orbit).
Ok thanks. And I edited my post. Sometimes my links are longer than I have time read on a lunch break 😁
 

cbwho

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This is perhaps one of the most important NASA missions. It's a shame nowadays that people (rocketeers especially) don't understand the importance of staving off the next big asteroid strike...
 

OverTheTop

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Michael L

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Didn't they try this with Mars? Oh... wait... yeah... that was a units conversion problem... Never mind...
 
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aerostadt

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One of the reasons MRV and MIRV on ICBM's are so practical is that once the payload is out of the earth's atmosphere the bus that is carrying all the warheads can make minor adjustments sending the warheads on vastly different trajectories. (Such is the insanity of warfare finding technical solutions to engineering problems. Once they are up who cares where they come down that is not my department says Wernher von Braun, or so went a comedian's line. Bottom line, give engineers good jobs to do real work.)
 

OverTheTop

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I can't imagine that they'll be attempting to do anything like bust it up,
Breaking up an asteriod is problematic in that unless you give it enough energy to ensure all the pieces have sufficient escape velocity to get away from each other then they all just stay in the same neighbourhood and you don't get a second shot at the problem. That is one of the things that limits using nukes. If the asteroid is rocky a nuke has a chance of splitting it. Ok to use them on metallic asteriods, but the issue there is timing. They estimate that it is most effective to detonate the explosion at about 70m altitude. The problem is that the closing speeds for these missions is in the range of 20-30km per second. Timing is critical for maximum effectiveness.
 

Michael L

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Breaking up an asteriod is problematic in that unless you give it enough energy to ensure all the pieces have sufficient escape velocity to get away from each other then they all just stay in the same neighbourhood and you don't get a second shot at the problem.
The Russians just proved that with a satellite. Trash everywhere.

staving off the next big asteroid strike...
I'm not sure how important it is but I'm all for trying as long as we don't splatter the planet with the detritus. Hand grenades were invented for a reason and the are effective.
 

Funkworks

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... they all just stay in the same neighbourhood and you don't get a second shot at the problem...
I haven't digged into this very much, but many small pieces still seem better than a big one. By coming in smaller, the pieces would come in at different times and places, spreading overall friction heat over a larger area, and more mass would burn up. It all depends on size and speed of course. A diameter of 160 m or 500 ft is apparently when it starts to be a concern. Not sure how fast a typical meteorite goes.
 
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