NASA's DART spaceship has hit the Dimorphos asteroid: what now?

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OscarCP
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NASA's appropriately named "DART" space mission (for "Double Asteroid Redirection Test"), funded at some 330,000,000 worth of USA taxpayers' dollars, has been, as far as we know at these still early days, successful in its various planned goals: to navigate to the asteroid Dimorphos, then hit it precisely as intended and, something at this time still being confirmed in detail, change its orbit slightly but enough. Because this now very small change is expected to increase gradually. So it was a very slight nudge that can have a substantial effect, given enough time.

The following is from Science, the AAAS publication, written before the impact, on what this mission may achieve and why it is justifiable:

https://www.science.org/content/art...n-mission-more-billiards-space-scientists-say


And after the impact, this:

https://www.france24.com/en/america...ccessfully-smashes- spacecraft -into-asteroid

And tomorrow, October 11 2022 at 2:PM (US EDT), as I write this:

https://www.nasa.gov/press-release/...-on-dart-world-s-first-planetary-defense-test


Now, to me at least, this allows for a discussion on how best to deflect an incoming asteroid that is really going to hit Earth and big enough to maybe, among other nefarious effects, cook us alive after setting the sky aflame, or at least making it hot enough to microwave us, sort of, with its radiated heat: A dinosaur-sized bad thing to happen.

There are other possibilities, besides sending many DART-like but bigger impactors, or just one carrying a really big H-bomb. Which, who knows?, might make many smaller asteroids of the one big one, perhaps with some big pieces still coming even more accurately in our direction, if the explosion does not vaporize it and, or breaks it into insignificant bits and pieces and, one way or another, sends the lot in the direction of, let's say, Antares in the constellation Scorpius.

For example, there is also the idea of sending a mass big enough to displace by its gravitational attraction the asteroid from its course and then drag it further from it by acting like a tractor linked to the big rock by gravitation alone. The tractor will have to have its own impulsion engine and, of course, be maneuverable enough to do this. And be massive enough to make the asteroid budge from its previous fatal course and do it fast enough.

There are some ideas out there on how to achieve this particular goal in a feasible way.
For example, by using many launches to carry water to a big pouch in space and let it solidify as ice inside it, as its heat gets radiated towards the very cold black sky around it, except for the part covered by Earth itself below.

Then accelerating to escape Earth's velocity the now full-of-ice pouch using the intentionally extra and still unused stages of some of the rockets that brought the water to the orbiting pouch. Their combined thrusts would be speeding it to some 4-5 km/s higher than the until then orbiting velocity it had where it was put together at a height of, let's say, some 600 km.

So not as big a deal as would be to launch the pouch directly from the Earth's surface, with the most enormous rocket ever built -- thus economizing in fuel, hardware, time and dollars. And embarrassment, if the thing blows up. As new giant rockets tend to do at first, assuming there are then seconds.

Of course, the icy pouch and those rockets would have to be built and maybe also deployed before the asteroid menace is discovered, or as soon as it is discovered, if then there is enough time left to send all that up and then ensemble it in orbit, etc.

Finally, the pouch would have to be navigated to an appropriate location near the asteroid.
And then an appropriately powerful thrust has to be applied to send both pouch and asteroid in a non threatening trajectory, ideally one that ends with both inside the Sun, so the threat from this particular big space rock is no more.

Some people have suggested, when the time comes, to spray from a piggy-backing small spacecraft the asteroid with a very black paint, so as it always partially faces the Sun, this one heats the ice until it becomes first a liquid and then a vapor at increasing pressure that can be vented to provide thrust: you get the idea.

Now, I am explaining this in some detail to clarify what my intention in writing this has been, not because it is my favorite idea. (I don't have one.)

Because I am curious to know what is yours, or what you make of all this.
 
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Answers and Replies

  • #2
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Personally, for me there’s not much more to add. You covered almost all the means proposed of deflecting or destroying a rogue asteroid.

Using a bomb on it just means having many smaller fragments having the same or similar trajectories to contend with.

Another issue is estimating the composition of the asteroid in order to estimate what the impact will really accomplish.

DART is perhaps the very first attempt at exploring the real engineering required to mitigate a strike on Earth. It’s better to study this now than to wait when a strike is imminent.
 
  • #3
OscarCP
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I agree, but I only have covered this topic in rough outline.
It should be OK to have other people's ideas on this, if they wanted to explain them here.

And now, some very recent news: important results are already in and they look good.

But before that, this is nice, watch the video:
https://www.nasa.gov/specials/pdco/index.html

And be scared, very, very scared.

The mission was more successful than expected and hoped for: as intended, the asteroid was pushed by the impact into a new orbit closer to the bigger asteroid of which it was and still is a satellite.

Being closer to the main asteroid, their mutual gravitational attraction is also greater, so the new orbit is also a faster one.
Because of this, the impact cut down the time it takes for the smaller one to go around the bigger one, the orbit period, by considerably more than expected.

Actually 25 times more than expected:

https://www.nasa.gov/press-release/...ion-impact-changed-asteroid-s-motion-in-space

Quote:

"Prior to DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit its larger parent asteroid, Didymos. Since DART’s intentional collision with Dimorphos on Sept. 26, astronomers have been using telescopes on Earth to measure how much that time has changed. Now, the investigation team has confirmed the spacecraft ’s impact altered Dimorphos’ orbit around Didymos by 32 minutes, shortening the 11 hour and 55-minute orbit to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus or minus 2 minutes.

Before its encounter, NASA had defined a minimum successful orbit period change of Dimorphos as change of 73 seconds or more. This early data show DART surpassed this minimum benchmark by more than 25 times.
"

Of course, it could well be that Dimorphos, the impacted asteroid, is a less massive body than people had thought it was.

But I am not going to quibble: this test has gone just fine.

So there we have it: our hard-earned 330,000,000 tax dollars at work.
 
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  • #4
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Yes, I can see the unintended consequences of tickling the asteroid and possibly making a mess of it should it collide with the bigger one.
 

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