NASA's DART Data Validates Kinetic Impact As Planetary Defense Method (nasa.gov) 31
After analyzing the data collected from NASA's successful Double Asteroid Redirection Test (DART) last year, the DART team found that the kinetic impactor mission "can be effective in altering the trajectory of an asteroid, a big step toward the goal of preventing future asteroid strikes on Earth." The findings were published in four papers in the journal Nature. From a NASA press release: The first paper reports DART's successful demonstration of kinetic impactor technology in detail: reconstructing the impact itself, reporting the timeline leading up to impact, specifying in detail the location and nature of the impact site, and recording the size and shape of Dimorphos. The authors, led by Terik Daly, Carolyn Ernst, and Olivier Barnouin of APL, note DART's successful autonomous targeting of a small asteroid, with limited prior observations, is a critical first step on the path to developing kinetic impactor technology as a viable operational capability for planetary defense. Their findings show intercepting an asteroid with a diameter of around half a mile, such as Dimorphos, can be achieved without an advance reconnaissance mission, though advance reconnaissance would give valuable information for planning and predicting the outcome. What is necessary is sufficient warning time -- several years at a minimum, but preferably decades. "Nevertheless," the authors state in the paper, DART's success "builds optimism about humanity's capacity to protect the Earth from an asteroid threat."
The second paper uses two independent approaches based on Earth-based lightcurve and radar observations. The investigation team, led by Cristina Thomas of Northern Arizona University, arrived at two consistent measurements of the period change from the kinetic impact: 33 minutes, plus or minus one minute. This large change indicates the recoil from material excavated from the asteroid and ejected into space by the impact (known as ejecta) contributed significant momentum change to the asteroid, beyond that of the DART spacecraft itself. The key to kinetic impact is that the push to the asteroid comes not only from colliding spacecraft, but also from this ejecta recoil. The authors conclude: "To serve as a proof-of-concept for the kinetic impactor technique of planetary defense, DART needed to demonstrate that an asteroid could be targeted during a high-speed encounter and that the target's orbit could be changed. DART has successfully done both."
In the third paper, the investigation team, led by Andrew Cheng of APL, calculated the momentum change transferred to the asteroid as a result of DART's kinetic impact by studying the change in the orbital period of Dimorphos. They found the impact caused an instantaneous slowing in Dimorphos' speed along its orbit of about 2.7 millimeters per second -- again indicating the recoil from ejecta played a major role in amplifying the momentum change directly imparted to the asteroid by the spacecraft. That momentum change was amplified by a factor of 2.2 to 4.9 (depending on the mass of Dimorphos), indicating the momentum change transferred because of ejecta production significantly exceeded the momentum change from the DART spacecraft alone. DART's scientific value goes beyond validating kinetic impactor as a means of planetary defense. By smashing into Dimorphos, the mission has broken new ground in the study of asteroids. DART's impact made Dimorphos an "active asteroid" -- a space rock that orbits like an asteroid but has a tail of material like a comet -- which is detailed in the fourth paper led by Jian-Yang Li of the Planetary Science Institute.
The second paper uses two independent approaches based on Earth-based lightcurve and radar observations. The investigation team, led by Cristina Thomas of Northern Arizona University, arrived at two consistent measurements of the period change from the kinetic impact: 33 minutes, plus or minus one minute. This large change indicates the recoil from material excavated from the asteroid and ejected into space by the impact (known as ejecta) contributed significant momentum change to the asteroid, beyond that of the DART spacecraft itself. The key to kinetic impact is that the push to the asteroid comes not only from colliding spacecraft, but also from this ejecta recoil. The authors conclude: "To serve as a proof-of-concept for the kinetic impactor technique of planetary defense, DART needed to demonstrate that an asteroid could be targeted during a high-speed encounter and that the target's orbit could be changed. DART has successfully done both."
In the third paper, the investigation team, led by Andrew Cheng of APL, calculated the momentum change transferred to the asteroid as a result of DART's kinetic impact by studying the change in the orbital period of Dimorphos. They found the impact caused an instantaneous slowing in Dimorphos' speed along its orbit of about 2.7 millimeters per second -- again indicating the recoil from ejecta played a major role in amplifying the momentum change directly imparted to the asteroid by the spacecraft. That momentum change was amplified by a factor of 2.2 to 4.9 (depending on the mass of Dimorphos), indicating the momentum change transferred because of ejecta production significantly exceeded the momentum change from the DART spacecraft alone. DART's scientific value goes beyond validating kinetic impactor as a means of planetary defense. By smashing into Dimorphos, the mission has broken new ground in the study of asteroids. DART's impact made Dimorphos an "active asteroid" -- a space rock that orbits like an asteroid but has a tail of material like a comet -- which is detailed in the fourth paper led by Jian-Yang Li of the Planetary Science Institute.
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but what say they launch Trump instead?
A Falcon Heavy could do it, but not to a sufficiently safe distance.
Years or decades of warning (Score:1)
According to TFS, this only works with "several years at a minimum, but preferably decades" of warning.
So if there is a new comet or another Oumuamua, this would be useless.
Re:Years or decades of warning (Score:4)
Yup, completely useless. Which is why this will never be done again and no studies done because it's completely useless.
When it doesn't work 100% of the time, just stop doing it.
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Indeed. No idea why some people have this mental disability that they cannot understand that nothing is 100%, but that does not make it useless. In this particular case the moron in question also seems to be incapable of understanding that obviously an extended sensor network would be built in addition.
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obviously an extended sensor network would be built in addition.
... and at the next (next but several) election, the network would be shut down "to save costs for the taxpayer". After all, if it isn't used from one millennium to the next, it's just a dead cost.
We'll just have to build a new one in time for it to be used.
[No sarcasm was deployed in the writing of this post.]
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According to TFS, this only works with "several years at a minimum, but preferably decades" of warning.
So if there is a new comet or another Oumuamua, this would be useless.
Yup, completely useless. Which is why this will never be done again and no studies done because it's completely useless.
When it doesn't work 100% of the time, just stop doing it.
To gauge the utility of another DART-like interception with minimal lead time, one has to consider several things. The most important is what the components of the required lead time are. The actual travel time to the target was 10 months. Assuming that the missile were ready along with the targeting support, then the lead time is mostly based on the missile travel time. The greater the danger to the earth, the shorter the distance from the earth and the shorter the required lead time. That's why this
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This covers roughly 95% of the impact threats. Comets are the remaining ~5%. So developing a technique that covers 95% is a huge advance, and the obvious place to start. Sort of like complaining about front-impact airbags because they are useless for side-impacts or roll-over accidents.
We are building out the catalog of threat objects from the inner solar system - we have all of the "dinosaur killer" threats, and even ones much smaller than that completely catalogued, and are working down the list. In the n
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Seriously though... (Score:2)
Smashing a satellite into an asteroid to study kinetic impact data might be interesting, but realistically .... I should like to believe that if there was ever an actual danger of an earth impact, the nations of earth would mobilize a bunch of nukes and sort it out.
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...I should like to believe that if there was ever an actual danger of an earth impact, the nations of earth would mobilize a bunch of nukes and sort it out.
Uh, didn't we just read an article stating something about how we haven't actually tested those nukes in decades? A rather fitting end to humanity to find a planet full of Rocket Mans trying to launch their bottle rockets against a planet killer. How very ignorantly human of us.
Even those jumping up and down over the success of this test should understand why bulletproof vests, aren't sometimes.
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Certainly it is worth investigating, but...
One hurdle to even doing an experiment is that the Test Ban Treaty of 1963 [wikipedia.org] presently bans testing nukes in space. This was, in part, because we realized that testing a nuke at high altitude [wikipedia.org] (hundre
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consensus on nukes is hard to come by
Consensus on anything is hard to come by, since it's often not even about the merits of the issue at hand but more about what each party can get out of the negotiations.
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Nukes are likely a _very_ bad idea. Protip: Caveman-thinking only rarely works.
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[hit 'em with nukes]
Blowing a big one apart can be counter-productive, missing the Earth with some of the fragments but making the ones that hit far more damaging.
If you can push it into a miss, and then into an orbit that will always miss, without breaking it up (or only dropping a few sky-show pebbles on an impact trajectory), why settle for less?
(Besides: A lot of these things are worth mining, and if you have to spend the resources to ship a pusher out to it to save the planet, and have enough lead tim
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A lot of these things are worth mining, and if you have to spend the resources to ship a pusher out to it to save the planet, and have enough lead time, why not make the pusher a miner/mass driver? They're both a thruster and a shipping system.
Heck: If it's big enough, once it's no longer a threat, SETTLE it.
The real-estate industry used to say they don't make more of it. With space industry that no longer needs to be true.
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I've seen that movie! Unfortunately the asteroid was full of precious metals, so we let it hit while trying to salvage those metals...
Mission lacked critical feature (Score:2)
This is great and all but when it impacts the asteroid it doesn't vibrate to announce "boop" which to me seems like a huge mistake. If we aren't booping asteroids, what's even the point?
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For a $billion dollar mission to potentially save humanity, I suppose we could spring for some sound effects.
"Has broken new ground" (Score:3)
They didn't validate a useful delta-V (Score:2)
Scaling the delta-V up by 2~3 orders of magnitude might introduce some uncertainty.
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A delta-V of 2.7mm/s means shifting an Earth radius in 1800 years. So a couple of decades warning wouldn't be enough to save the Earth, although perhaps you could at least steer clear of a major city.
So hit it again, and again, and again.
Scaling the delta-V up by 2~3 orders of magnitude might introduce some uncertainty.
The point of the experiment, as I understand it, was to see if such objects might be coherent enough that you can push them around like solid objects, rather than essentially dustballs that y
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??
6378 kilometers / (2.7 mm/sec) =~ 75 years
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75yrs does mean a more useful delta-V! Thanks for checking the maths!
How many papers? (Score:2)
The findings were published in four papers in the journal Nature.
So, if in doubt, RTFJournal :