- Wild that we went from "can we even deflect an asteroid" to measurably changing a solar orbit. 150 milliseconds sounds tiny until you realize compounding over decades makes that a meaningful trajectory shift. The engineering confidence this gives for actual planetary defense is massive.
- >> The engineering confidence this gives for actual planetary defense is massive.
I've been waiting for this a long time. They initially reported significant changes to the orbit of the smaller rock around the larger one which was cool and all, but I kept wanting to hear how much it affected the whole system. I suspect it's taken several years to answer that because it's such a tiny change in velocity. Dimorphos we can deflect, Didymos not so much.
- I find it mesmerizing how predictable orbital mechanics are. We can tell where celestial body will be years ahead with meter accuracy.
- Or offense.
- You know what they say: the best planetary offense is a good asteroid redirect program
It's also the best planetary terrorism, going by the plot of The Expanse
- First things first, we have to colonize the rest of the solar system before we can terrorize Earth.
- Why exactly? I think the US ought to spend a few trillion on an actual space battleship - one that never comes down to the surface, just sits in orbit. There was a project regarding dropping telephone pole sized pieces of metal from space as an offensive weapon - put something like that on the space battleship and...
That is simply "Assured Destruction" with absolutely no mutual drawbacks or lingering consequences like radioactive wasteland. Just craters.
This is also something where the 1st country to achieve the "Space Battleship" could effectively prevent any other from also doing so...
In theory, Bezos or Musk could do it.
I don't understand why any country would bother with ground based military assets at this point.
- That totally depends on the type of super villain organization we're discussing. Some are willing to watch the Earth burn making the colonization step unnecessary. Others think humans are the problem and again would be willing to skip that step.
- It depends on the size of the asteroid and precision with which it can be aimed...
- queue the neurodivergent mech pilot
- Slight changes can cause such impacts? Now imagine how many other meteors and comets also will be adjusting because of this. Will one of them once on a course to never hit earth suddenly shift to hit earth in a thousand years time? The confidence i get is the opposite
- I don't think asteroids (like the target) have influence on others. There's so much space between them, and their mass is almost neglible.
- > slowed the orbit of a pair of asteroids around the sun by more than 10 micrometers per second
Or in other words, 1 meter per day
Why not say that?
- Because the SI unit is meters per second, so maintaining the “second” gives people with that understanding a basis in which to compare the delta-V.
- 1.22337962962963e-21 light years per second!
- That's interesting news. I wonder how much kinetic energy it had. This accumulation of information might be useful if an asteroid were to hit the Earth someday. At the very least, it's more realistic than sending oil drilling experts to an asteroid.
- >it's more realistic than sending oil drilling experts to an asteroid
Mandatory sharing of Ben Afleck commentary speaking for all of us.
- > ...I wonder how much kinetic energy it had...
Since kinetic energy is proportional to v squared, that highly depends on how you measure v...
- Interesting. I'd not considered the loss of mass as a means of propulsion.
Obviously there was the kinetic energy transfer but the impact ejacted some of the asteroids mass opposite to it's trajectory further increasing it's trajectory change.
Cool demonstration, hopefully not needed one day.
- When the impact happened the news articles seemed to imply some surprise about that as well which seemed strange to me. I just wrote it off to the journalist just not being up to speed on the subject matter. The size of the debris field trailing also seemed to be a surprising result.
- It's the butterfly effect. After the momentum exchange (the rocket slamming, stuff being ejected in the impact, etc), the entire system was left with different properties. From now on, the equation F=Gm1m2/r^2 will have a different m1, and you can sum the equation over all m2 (literally every other massive object in the universe).
- That's how rockets work.
- Yeah, I sort of meant in the context of an object losing its mass, it's seldom used on earth as the effects are small but on the timescale/distance/speeds of an asteroid it could have noticeable effects.
Rockets are using mass loss but there's more going on with the rapidly expanding gas causing the increased impulse.
- Rockets are able to optimize due to dealing with a gas. It's still just pushing off of a disconnected mass. You go one way the lost mass goes the other.
If you think about it that's how a cannon works. The projectile gets pushed forwards and the barrel gets pushed in the opposite direction. Some of the larger ones can push their launcher back quite a bit more than you might expect.
My point is that this is actually a common failure of intuition. We tend to think of larger objects on earth as fixed and in our day to day life on dry land they often are (at least more or less) due to static friction.
A slightly more interesting observation (I think) is that if the bodies don't achieve escape velocity relative to one another then the forces all cancel out in the end. It just might take an arbitrarily long time in the case of similarly sized masses.
- Is this a surprise?
- I'm annoyed at these nothing-burger titles...
Instead of pointing out that exact measurements finally came in (of long term movement change), journalist instead focused on the obvious outcome that everyone expects and knows
- The top comment in this thread calls this "wild" and expresses amazement that this is possible; clearly it's not what "everyone expects and knows".
The nitty-gritty details are what the article is for, not the title.
- That's amazing
- Is debris a problem? I think the ideal would be to embed or clamp a rocket on the target.
- A lot of asteroids are much less solid than we used to think. Some of them are big rocks, but many of them are just piles of sand- and gravel-sized material loosely held together by gravity. Clamps work great on the solid rock type, but many of the alternative methods - including smashing into it - work on asteroids of any composition
That's valuable not only for versatility, but also because it would really suck to send a spacecraft on a redirect mission only to find out that our assumptions about the asteroid's composition were wrong
- https://en.wikipedia.org/wiki/Mass_driver
You build a little factory and use chunks of the asteroid itself as thrust.
- Some have suggested attaching a solar shield to objects to add drag to alter the course. However, that would require a much more precise landing and some sort of drilling/anchoring effort. A kinetic impact like this is always going to be more efficient.
- Well done, DART, which country did you aim it to?
- India
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- [flagged]
- Wow, that's the first step!
However, the most efficient method would be actually land (I know - maybe even impossible?) on it, and use propellers to change its trajectory. We don't have too much throwaway high-tech to crash it on asteroids...
- Impact is actually a more efficient method, as it avoids the fuel consumption required for deceleration and soft landings.
- I'm not sure this is actually a necessary explanation...but while propellers technically COULD function in space (not a perfect vacuum, right?)...they're basically going to be useless.
- He probably misuses "propeller" which is strangely restrictive to "rotative blade propulsion" in English whereas "to propel" is generic in its meaning.
- Be careful about how you store those inflammable propellers.
- Inflammable made me so angry as a child/teen when I found out. I read it in our encyclopedia set but we didn't have a dictionary, and this was pre-internet.
It was in the context of hydrogen and I could have sworn it was flammable. But here is this encyclopedia telling me it's INflammable. It's... not flammable? Looked it up in the school library.
Thank you, that memory came up from the depths of time. Probably haven't thought about that in 30 years. Funny how we sometimes just didn't know stuff, and couldn't find out back then.
- Inflammable means flammable? What a country!
- Exactly!
The only logical way out of the flammable/inflammable mess is to use 'flammable' and 'non-inflammable', which makes me so mad.
- It's just a parsing error. "in-" is also a prefix to create verbs from a name or another verb like inhume, inflame, induce, incite, inject, infiltrate. Inflammable is (inflame)-able and not in-(flammable)
80 points by pseudolus 3 days ago | 43 comments