DART & HERA, NASA/ESA Asteroid Redirection Missions Options

[Daniele_bianchin...]

So we wouldn't have more pictures of Didymos? :- /
I tried to compare Didymos ad DimorphoS with other recently visited asteroids:
http://mondialieni.altervista.org/asteroid...a_Bianchino.png

That's a brilliant montage Daniele!, thanks for your time composing it

It's easy to forget that the reconnaissance of the asteroids in our solar system is fairly well-advanced these days. Psyche and Lucy will really add to our knowledge in the next decade.

I feel really lucky to be along for the ride in this era of discovery. On the year I was born (1967), we had some pretty decent images of the moon, and that was about it.

Many Thanks jasemd.
It's nice to Live these future and modern moments !! there will be others!

I wonder if a momentary ring of debris like Chariklo can form around the system! :-) or fantasy?

>,

[Gladstoner]

Centrifugal scree 'slopes' on opposing hemispheres? Compared with talus features on Ceres:

[fredk]

For mass 535 kg at 6.65 km/s, DART had kinetic energy of around 10^10 J.

For a radius of 80 m and density of around 1.86 g/cm^3 (as assumed in Owen etal), the gravitational binding energy of Dimorphos is -3/5 GM^2/R ~ -10^7 J.

So DART had ~1000 times as much kinetic energy as would be needed to completely disperse Dimorphos (ie to "rest at infinity"), ignoring any mechanical cohesion in the moon.

One other relevant energy scale in the system is the orbital kinetic energy of Dimorphos. With a (pre-impact) orbital velocity of around 0.17 m/s and the above mass, I get around 6*10^7 J. So DART had roughly 200 times the KE that Dimorphos did. So it's not surprizing that DART could change the orbit significantly, subject to all the same caveats about dependence on mechanical properties of the moon etc. as we discussed above.

This suggests that impact may not be the most efficient way to perturb an asteroid, since only some small fraction of a percent of the KE of the impactor gets transfered to the asteroid; the rest going to heat and the ejecta. If time permits, perturbing instead with rocket engine burns (either sitting on the surface or via a gravitational tractor) may do better, and be more predictable, although of course such an engine needs to be sent to the asteroid and then slowed down to match its velocity, so it's not clear which would actually be more efficient.

[StargazeInWonder]

It seems like it'd be more efficient than that to have a rocket full of fuel hit the asteroid and explode on contact, combining the kinetic energy of the craft with the chemical energy with the explosion. There's no need to make a nice, controlled burn that the rocket survives.

[nprev]

In practical terms, this becomes a problem in terms of lead times & complexity even if compositional variables aren't considered. It would be difficult to built, test, and launch a powered redirect mission with a short lead time, but a DART-like impactor would be comparatively easy. In fact, building & storing (with ongoing maintenance & testing) a powered system for short-notice launch would be considerably more expensive than doing the same for an impactor mission.

Hard to say what, if anything, will eventually be decided here re an operational asteroid deflection system. But DART definitely provided a baseline set of interesting questions to ponder.

[mcaplinger]

There's no need to make a nice, controlled burn that the rocket survives.

Oh, that must be why we just explode the fuel in a rocket instead of spending all that effort to build a complex rocket engine.

Seriously, you have to get the rocket exhaust to all go in the same direction at as high a velocity as possible for maximum efficiency.

[Bill Harris]

Hubble is seeing a double tail around the Diddy-twins. A tail from the debris cloud could have been expected, but it seems that this tail and companion tail imply that there are active processes at work beyond the impact ejecta.
It will be interesting to see post-impact images from Hera.

https://hubblesite.org/contents/news-releas...2/news-2022-056

[HSchirmer]

...you have to get the rocket exhaust to all go in the same direction at as high a velocity as possible for maximum efficiency.

Agreed; first thought is that a 'perturbation solution' would want a BDB (big-dumb-booster) that is a simple as possible-
Perhaps a SRB (solid rocket booster) filled with a nitrogen or ammonia ice that will sublimate at the temperature of the warm side of the asteroid (perhaps add solar panels and heaters to jump-start the process)

[mcaplinger]

"Near-Earth Asteroid Deflection Strategies", by Dan Mazanek of NASA LRC, https://sservi.nasa.gov/wp-content/uploads/...on_Mazanek1.pdf is a good summary of various approaches. Direct propulsion is not the most effective according to this; short of nuclear weapons, kinetic impactors were judged the most effective.

[fredk]

All of this is for the unlikely scenario that an object large enough to do serious damage is on course to collide soon. Objects large enough to make kilometre-sized craters are expected on intervals of thousands of years or longer, and the fraction of those that would hit densely populated areas is tiny.

It's still sensible to plan for those rare events, but likely we'll be in a very different regime for the next major strike: thousands of years from now we'll (hopefully) detect the objects well in advance with future surveys so there won't be any rush to launch an interceptor, and no disadvantage to the slower avoidance methods.

[Explorer1]

Even if less efficient (and considering the result last September, it seems quite effective!), multiple KIs could work just as well for more massive objects, just sending one after the other in a sequence (Shoemaker-Levy-9) style. One can separate the impacts by enough time for debris to dissipate to ensure the next one hits the target without running into (of course, a KI can be completely inert by the time it makes contact; as long as it has mass that's all that's needed).

(And I'm sure the PDCO and many others have already considered everything we discuss here anyway)

[Marcin600]

On October 27, 2022, a new ASI event will take place: „LICIACube, un mese dopo!” [LICIACube, one month later!]: https://www.asi.it/event/liciacube-un-mese-dopo/

„...One month after the DART LICIACube mission (...) ASI is organizing a public event to present the contribution of the Italian scientific community. The event will be held at the Auditorium of the ASI headquarters on October 27, 2022, at 10.00 (...) LICIACube is still downloading the acquired images, data storage and processing is managed in the Science Operations Center (SOC), at the Space Science Data Center (SSDC) of ASI...” [with agenda - in Italian]


Maybe we'll see some new images and / or interpretations???

[nprev]

There's a case to be made for diverting smaller impactors down to Chelyabinsk-sized, though. Those demonstrably not only can cause extensive damage & injuries, they can also too easily be misinterpreted as military actions. Certainly long lead time detection & characterization of these smaller objects would mitigate the latter aspect, but it might be a good idea to be prepared to intercept them if they have a high probability of affecting a population center or other important/sensitive location.

[Marcin600]

On October 27, 2022, a new ASI event will take place: „LICIACube, un mese dopo!” [LICIACube, one month later!]

The recording of the event is here: https://asitv.it/contenuti/download/live/1e...be-un-mese-dopo
(only in Italian, no new pictures)

Some quotes from presentations:
The color of Didymos as seen by the LUKE camera is giallino = pale yellow
Characteristics of the plume:
- wide cone opening
- "filamentous" structure
- different distribution of speed and particle size
- deviation or overlapping of internal flows ("streamers") during the evolution of the plume
- morphology variable over time

And at 02:51:45 - nice clip of the OSIRIS-Rex touchdown video

Attached thumbnail(s)

 

[Explorer1]

Seven possible future targets for LICIACube being examined: https://pbs.twimg.com/media/FgEHo1jXwAE35_o...&name=large

The closest one could be for next March (2000 YA) but 14827 Hypnos seems most exciting to me (a possible extinct comet). Obviously the cameras on LICIACube are not as good as DART's was, but it's always a good opportunity to use a perfectly functional spacecraft!