Good article and very interesting content but stuff like:
"The impact caused the asteroid’s orbit around another space rock to shrink — Dimorphos now completes an orbit 33 minutes faster than before the impact"
drives me nuts. How long did the orbit originally take? Without this information it very much obscures the point.
Edit: I looked it up
"Before the impact, the orbital period was 11 hours, 55 minutes. It now is 11 hours, 22 minutes. NASA's previous estimate, announced in October, was an orbital change of 32 minutes. The benchmark for success had been set as a change of at least 1 minute, 13 seconds."
So it reduced it by about 1%. Pretty cool.
Edit2: as pointed out correctly by @statusgraph it's actually close to 5%. I fumbled the math on that.
Just tried this on macOS but it must be a different 'units' command as it won't accept that input. :-(
However I just discovered that if you hit command spacebar and paste that into the spotlight search it gives the right answer! Spotlight has always done simple unit conversions but it didn't used to be able to do calculations with units in them. I wonder when that was introduced...
Yes, the ellipse of the orbit would change a bit, while still passing through the point where the impact happened. Most of the change would be on the opposite side of the ellipse.
However, I think that for such a small velocity change, it is a reasonable approximation to assume that the ellipsis around the sun stays pretty much the same, and only the phase of the object (i.e. where it is on the ellipsis at which time) is affected.
in astronomical terms, measurable but not really significant, can become significant at cosmological times scales/distances. adjust the trajectory of something at the distance of Jupiter by a "measurable but not really significant" amount, and it could be the difference of a direct impact with earth or a near miss by the time that not really significant amount is accumulated for that distance.
Even better, if you scroll down far enough that results would scroll off the left side of the page it straightens again. Someone considered the edgecases.
I was going to see if they imparted any meaning into the angle they chose to CSS transform, knowing Google and all, but alas, they just did 1 degree.
First off, I thought that it would be cool if they rotated a proportion of 360 degrees equal to the proportion of the change in orbital time period to the previous orbital time period of the asteroid. Then I realized that it changed by around 5%, so that would be 360 * 0.05 = 18 degrees. Not really readable.
That's 2 minutes that I'll never get back, but it's left me amused for some reason. Heh.
Wow, that's a neat little Easter egg! It's always fun to stumble upon unexpected surprises like this. I wonder if Google has any other hidden gems like this one. As for the Double Asteroid Redirection Test itself, it's fascinating to see how scientists and engineers are working to develop technology to deflect asteroids that could potentially collide with Earth. The potential consequences of such an impact are staggering, so it's reassuring to know that steps are being taken to mitigate this risk.
I thought, well, there must be many more, perhaps the network log tab brings something up to investigate. I was curious on how they did this, so I tried to trace the request and immediately realized that the seemingly tiny and spotless Google home page is in fact one giant nightmare of obfuscated code. I bet one could write an entire programming book just about that one page transition.
Oh wow, it started as a game concept! I was just thinking I wish they made a videogame with the physics and geopolitics (stellar politics?) from the show.
There is an Expanse board game[0] that might interest you (it's been described as being like the cold-war themed classic, Twilight Struggle, but for up to 4 (TS only plays 2):
The Expanse, a board game based on the Syfy television series of the same name, focuses on politics, conquest and intrigue similar to the board game Twilight Struggle, although with a shorter playing time. The card-driven game uses key images from the show, along with action points and events that allow players to move and place "Fleets" and "Influence".
In more detail, players represent Earth's UN forces, the military of Mars, the rebels of the O.P.A., and the mysterious corporation Protogen Inc. Each player has special abilities that must be maneuvered to gain advantage. Players increase their control over the solar system using characters and events from the universe of The Expanse.
(There's also expansion, The Expanse: Doors and Corners, that adds new tech, leaders, the protomolecule, etc.)
The only problem would be finding a reasonably-priced copy as it appears to be out-of-print, which can lead to the price of second-hand copies going way up.
I kid but not really. The Expanse might be fictional but the threat it raises and considered with here isn’t - it’s good to see this as a proof of concept but there lots more to be done, detection included.
Thanks. I got a couple whales of undetermined species in my aquarium and handle them daily to give them a good scrubbing. That comparison gave me some perspective.
- With goose down having a density of 0.00286 g/cm^3.[1]
- The area of a football pitch being roughly 0.714 hectares.[2]
You could cover one football pitch to a depth of nearly 50 meters:
You have: (1000 tonnes / (0.00286 g/cm^3)) / 0.714 hectare
You want: m
* 48.970637
/ 0.0204204
(Using GNU Units.)
If you spread the feathers to a depth of 1 cm, you'd get roughly 5,000x more coverage, or 5,000 football pitches. Give or take.
________________________________
Notes:
1. Jing Gao, Weidong Yu, & Ning Pan. (2007). Structures and Properties of the Goose Down as a Material for Thermal Insulation. Textile Research Journal, 77(8), 617–626. doi:10.1177/0040517507079408 <https://sci-hub.ru/10.1177/0040517507079408> p. 624.
At some point in the next few decades, I expect to see humanity use this technology to divert an asteroid away from the Earth. And that's pretty neat.
Chelyabinsk was only a 20m asteroid, yet thousands were injured and a lot of damage was done. It's not inconceivable that in the next couple decades, we could predict that sort of event years out, and send a (likely much smaller) redirector mission to give it a tiny push, preventing the asteroid from entering Earth's atmosphere.
What scares and fascinates me though is what happens when we start asking 'okay, but where is it going to hit, and how many of my voters live there?'
Maybe, but you should watch Scott Manley's videos about keyholes. Asteroids can have orbits that are highly sensitive to initial conditions so you can't predict that much in advance even for some asteroids with known orbits.
I actually expect them to route them towards Earth, to some stable orbit, to be mined. But yes first the collision protection, that's much simpler to achieve and important
An asteroid already on a collision course with Earth only needs a tiny push to miss if we hit it early enough -- think about slightly bumping a sniper before he takes the shot. An asteroid a month out, heading straight for Earth's center, could be redirected to just skim the outer atmosphere with only about 4 m/s of delta-V.
On the other hand, getting a near-miss asteroid to orbit Earth instead means taking it from above escape velocity (11.2 km/s) to an orbital velocity, which means at least a thousand times more delta-V (more like 4 km/s). And that's the easy case -- getting an asteroid from the belt to fall toward Earth is another several km/s on top of that. Besides, ejecting 1M kilograms into a busy Earth orbit in order to slow the asteroid down sounds like a pretty scary idea. Especially since we'd have to do it hundreds of times for one asteroid.
The problem is that we have no ability to conclusively determine whether or not an asteroid is on a near-collision course, or on an actually-collision course.
And if it's the former, giving it a small bump is just as likely to put it on an actually-collision course as not doing anything at all.
There’s at least a plausible need there, what with the whole “don’t want to slam an asteroid into the planet” problem.
Mining is still an utter fantasy. It’s completely economically unviable to mine anything from an asteroid and bring it down the gravity well, and we have close to zero ability to actually mine and manufacture anything in space. We are a long long long time away from that.
It's an interesting question. The assumption is that it will never (or at least not for a very very long time) make sense to mine or manufacture in space for use on Earth. Mining/Manufacturing in space for use in space will presumably happen in only a very long time.
That said; what the bigger issue - for in situ operations, the distance to get the raw materials or just doing anything with the raw materials at all? Is it going to be - we could do anything at all but going all the way past the orbit of Mars is too much trouble - or - Getting to a rock past Mars is easy but it's hard to do anything practical with it (compared to just getting it off Earth presumably)
I got no clue as to which way it could go but it doesn't seem a question that answers itself to me.
There was a quote I read somewhere about giant impact extinctions to the effect that "They'll keep happening until a species evolves that can do something about it."
> It is a truth universally acknowledged, that a single species in possession of a good technological base and a will to survive, must be in want of a interplanetary kinetic asteroid redirection system.
It would be waaaay easier to build a self sufficient colony hundreds of feet below the ice in Antartica. And there would actually be a reason to want to survive.
> "The impact ejected at least one million kilograms of rock from Dimorphos’s 4.3-billion-kilogram mass. The debris formed a tail that stretched for tens of thousands of kilometres behind the asteroid."
"one million kilograms" = one gigagram
"4.3-billion-kilogram" = 4.3 teragram
"tens of thousands of kilometres" = tens of megametres.
I don't understand the media's reluctance to use large SI prefixes for mass and distance, when they'll happily use them for electrical units.
I have never heard of the use of kilo/mega/giga used for standard mass or distance units, either in the media, scientific literature or anywhere else (except kilometer, and kilogram, but kg IS actually the standard unit, not g)
Only place where I've witnessed it's use is during my own personal musings while sitting on the loo. Same goes for money. "Gigadollars" has a nice ring to it but it's not used :(
There are other units of measurement when the numbers get really big, like AU, lightsecond/minute/year, Solar Mass, etc. I'm no scientist, but I also think when you get to the astonomical scale, order-of-magnitude relative measurements is more useful knowing a galaxy's mass to the nearest gram.
No, they don't get used, but they should be. We all understand metric prefixes now, and use them for other units. I'm saying we should stop using "thousands/millions/billions of" kilometres/kilograms, and start using mega/giga/tera metres/grams.
However they are frequently used for tons (the megagram variety, not sure about imperial). Kilotons are of course famous because we measure explosions and other forces in kiloton-tnt-equivalents, but Megatons and Gigatons are also used (the later commonly for emitted CO2)
I think they're just not well understood by most people. 1000Kg is a small car. 1Mg is...who the fuck knows. You can tell someone a building weighs 1Gg but they're gonna stare at you funny until you tell them it's about 1000 small cars.
OTOH, 1KHz has no basis in physical reality for normal people but they know 1KHz is 1000x faster than 1MHz so it works nicely for things like "is my new computer faster than my old computer" (at least a decade ago, I don't see clocks advertised much at all anymore).
Well of course if it doesn't get used then most people will not be familiar with it — that's the point. We should encourage the use so people become familiar with them, so we can stop using "thousands of" and "millions of".
Re kHz, I think most people understand frequencies we can hear. (1 kHz is close to a high C note). MHz and GHz are radio frequencies.
1 megagram is a ton, which is widely used. A lot of stuff is measured in tons, including cars (“this car weighs almost two tons, which is pretty heavy for a sports car”), cargo (20-ton train car), etc.
It stops on the ton, though - “40 thousand tons of grain” - gigagram isn’t used.
The imperial system is perfect. 625,000 golf carts is one Great Pyramid, and 6,557,075 Great Pyramids of Giza is one Texas. How is this not obvious? /s
Also, ChatGPT trivializes sarcastic responses that involve a bit of math.
1000 tonnes. Though using the base units is never wrong and I generally prefer it. In common language a ton can be a short ton (US) or long ton(UK) though I am sure they are all well within the margin of error.
Shower thoughts this morning while listening to the NEOMIR project that watches out for asteroids heading towards earth from one of its Lagrange points[1]: observing is the first step, but why don't we ready a few missiles waiting in space/orbit in case asteroids head towards earth ? How hard would that be to maintain in working condition for decades ? The goal would be to remove the need to prepare a rocket from earth (lots of fuel wasted, etc.) and have lower response times in case a "big one" (or many smaller ones) are ever detected.
They hit it "head on" ... or you mean the actual angle?
> Other work Ernst and her colleagues are doing recreates the impact itself. They calculated that the spacecraft flew in on a trajectory about 73 degrees above the local surface. "So not quite vertical, but pretty close," she said.
If anything, these few days have shown to me that many on HN don't seem to get the metric system at all. Broken math and silly conversions everywhere, baby
"ton" is overloaded with three units having the same name, although at least the "metric ton" is often spelled tonne (1 tonne = 1000 kg ≈ 2204 lbs), but that still doesn't do enough to disambiguate it in speech. In written texts, it can be difficult to impossible to know whether "ton" refers to the American unit (2000 lbs ≈ 907 kg) or the British unit (2240 lbs ≈ 1016 kg).
I've never seen non-americans take ton for anything other than 1000 kg. The real funny thing in that other thread is the guy specifically claimed "metric tons" while doing math with some other type of tons.
Who cares, though, right? What's important is sounding right
Well... at least to me, one of those is a large amount of a mass that I have some understanding of.
The other is lalaland non-sense.
I'd have even preferred "Billion grams" over gigagram. Although a gram is really hard to intuit about, since it's basically just too small. I can probably reliably tell you if an object I pick up weighs 1kg or 2kg, I probably can't reliably tell you if it weighs 1g or 2g.
I wonder if an antimatter collector could be built in space. Collect antimatter in a magnetic bottle and put that in a missile. Launch small, fast, powerful antimatter missiles via maglev towards asteroids.
Antimatter is a really inefficient energy storage mechanism. Even if we figured out way to make it efficiently, it would still be super expensive. Nuclear weapons are efficient, they make energy, and comparatively cheap.
Also, this mission was to demonstrate could move asteroid without large explosion. There is fear that most asteroid are loose rubble and would be blown apart by blast.
I happen to agree, but the headline conveys information in the most accessible format. SI just makes a lot of promises that it can't deliver on, because human beings aren't interested in such a unit system.
They seem to want just three unit scales, "smaller than me", "the same size as me", and "larger than me." They will fit the entirety of their experience and frame of reference into these three scales, even when they know there are other options.
It's probably the reason they punted and let a _kilo_gram be a base unit in the first place, and why everyone represents the distance to the sun in kilometers instead of gigameters; even though they round the kilometer figure down to a point where gigameters would clearly be the most warranted.
which makes a whole bunch of other things simpler. The other option to meter-kilogram-second would have been the centimetre-gram-second, but then you're not using the metre as your base unit for length. Scale is probably the reason for picking MKS over CGS, but it's only moving the weird-base-unit problem around.
ISTR reading once that MKS has coherence advantages over CGS with regards to electromagnetism (probably current), but I can't find the reference now.
It's so that it retains coherence without moving to a non-gram based measurement. You could have easily selected a new unit, or even just given what we call a "kilogram" a non-prefixed name and be done with it.
The point is, it's obvious that they didn't define the system on first principles, but allowed "creature comforts" to creep into the scope of the system.
For example the needless definition of Hz which conflicts with radians, and the needless definition of the unitless mol. These are obvious conveniences. They're not first-class members of the system.
The kilogram is the SI base unit of mass. Mass is the only one where the base unit has a multiplier for some reason. Expressing quantities in the base unit makes total sense for me as a metric native.
honest question: if a golf cart sized spacecraft ejected 1M Kg out of this asteroid, if it had hypothetically hit the earth's atmosphere, would it have broken up easily?
If the impact speed were ~30 km/s [1], breaking it up in the atmosphere through friction would create about...
E = MV^2/2 = 3.87 10^18 joules.
For contrast, the energy released by the Tsar bomba was 2.45 * 10^17 joules. The Tunguska meteor impact was something on the order of ~1 * 10^17 joules.
Even if much of the energy dissipates in the upper atmosphere, and does so over multiple seconds, I'd say that anyone within ~150 miles of the point of 'impact' will likely have a very, very, very bad day.
[1] Which is a pretty bad case. The Chelyabinsk meteor was traveling at ~18 km/s - a 30 km/s impact would be close to a 'head-on' collision.
Maybe, maybe not. This was a sudden impulse to one point on the asteroid but reentry would be a gradually increasing force across the whole leading edge.
It’s likely that the gigagram of ejecta is in some sense the “easiest” 1M kgs to knock out. I doubt it’s boulders and loosely compacted gravel all the way down.
... you realize that we just bumped a smaller object orbiting a larger asteroid so that it has a VERY slightly altered orbit, right? It's not like we drastically changed the orbit (let alone gave it escape velocity from the solar system).
so 610kg smashed into 5.5 million tons and it lost 1 million tons in ejected mass?
I presume that if it wasn't such a loose collection the result would be quite different.
Given that it is a loose collection it wouldn't be a real threat to earth anyway (if for instance it was heading towards us) because that would cause it breakup in the atmosphere easier.
they seem to be surprised by these equations.. I thought this was all fairly established science.
There isn’t much need for quick reaction time. This technique can only move asteroid by tiny bit so it only works over years. If the asteroid is going to hit sooner, there is not much we can do. Our rockets aren’t that fast and would take months or years to get there.
It does make sense to develop spacecraft so it can be launched quickly without going through years of development. Maybe build two and test one out. Then we would be ready to build more if needed.
You mean for the launch? Or getting to asteroid? Or moving the asteroid?
Launching Project Orion from the ground would dump a ton of radioactive fallout. Unfortunately, it is expensive to launch with rockets because of the heavy plate and having to assemble it.
Launching it from orbit will knock out most of the satellite and could cause EMP over wide area. It doesn't do any good if you deflect asteroid, and one this size would only cause regional damage, if destroy civilization.
The Starship is big enough that can launch spacecraft with a few nukes and rocket to reach asteroid. Assuming that Starship is being launched regularly, then launching or building the spacecraft would be sufficient.
This whole mission of colliding with asteroid was done because it is uncertain if nukes could be used to deflect asteroid. There is a danger that nuke would blow the asteroid apart instead of deflecting it. For one this size, that probably wouldn't be a problem but turning larger one into few smaller ones would be bad.
2) the asteroid was too close and you needed it there as fast as possible
because as the original article points out, the closer it is / more deflection you need, the more firepower/energy you need. Heck as a last resort you can use the ship to simply push the asteroid.
You're going to take a bit of fallout (and there was lots of work in orion in making the "cleanest" explosions) vs an asteroid strike... you'll take a bit of fallout.
Orion is the only ship design with current tech (heck 1960s tech) that can get there fast enough with enough payload. You know, if one was ready, etc etc etc.
I'm not saying it would be feasible, just that within the "oh my god asteroid" scenario it might be the only design that could work.
It's obviously debatable, but Orion might be able to be chucked together in a short time. You don't need to optimize weight, you just need a big shield and the nukes, and a nuke firing system. (you know, just that).
We have nearly all of the extinction level asteroids detected. It is really unlikely that one on collision course would be detected. There could be dangerous comet which appear suddenly but those are even less likely. The other problem is that they are big enough that might be hard to divert.
The test one is small enough that it wouldn’t do that much damage. Worth the expense to send spacecraft to divert something that could destroy a city. Not worth wrecking civilization to protect a city. Most of asteroids we haven’t detected are the smaller size.
Finally, Orion isn’t necessary. Nukes are small, you could send up a bunch in Starship. We could also come up with better propulsion, like nuclear rocket, that would be useful. Orion would be stupid expensive for very unlikely contingency.
You are probably correct in about ... six months when Starship officially hits orbit.
The only real thing that Orion has going for it is that it is brutally effective. If we need something to launch fast, it might not be that much on civilization level effort to get a big honker going.
nobody yet has said 1m KG == 1000 1000kgs == 1000 tonnes == 1 kilotonne.
the original A bomb was 17 kilotonnes. explosive equivalent. I have no idea what a kilotonne of friable matter entering the atmosphere represents, in explosive equivalent.
$330 million dollars just for that, it's an insane waste of money. The Mars helicopter cost $80 million dollars. 50% off the US doesn't have 1k in their savings account.
"[Dimorphos] ... seems to be a loose pile of rubble barely held together by gravity — whose surface would probably shatter spectacularly when DART hit it.
DART [impacted] Dimorphos at more than 6 kilometres per second. The impact caused the asteroid’s orbit around another [larger] space rock [Didymos] to shrink — Dimorphos now completes an orbit 33 minutes faster than before the impact.
The impact ejected at least one million kilograms of rock from Dimorphos’s 4.3-billion-kilogram mass. The debris formed a tail that stretched for tens of thousands of kilometres behind the asteroid. Various telescopes watched over weeks as the tail shifted and evolved under the pressure of the Sun’s rays; the Hubble Space Telescope even detected a second tail, which had disappeared by 18 days after the impact.
One factor [in successfully changing Dimorphos's orbit] is that the spacecraft hit a spot around 25 metres from the asteroid’s centre, maximizing the force of its impact. Another is that large amounts of the asteroid’s rubble flew outwards from the impact. The recoil from this force pushed the asteroid further off its previous trajectory. Researchers estimate that this spray of rubble meant Dimorphos’ added momentum was almost four times that imparted by DART4."
It's good that this technique worked on a "loose pile of rubble", but I'm not sure we can assume all asteroids are composed in the same way. A denser rock of iron or similar might be more difficult to divert.
Shaking off 1/4300 of the mass, roughly, is likely not the most important part. Changing the trajectory even a slighted bit may mean much more after the asteroid travels a few million km. To avert a direct impact at Earth, we only need a correction of about 7000 km of the orbit intersection point, at the very worst case.
I'm still intrigued at a possibility of detonating a megaton-classl nuclear device at a very close proximity to a tough metal / rock asteroid. Consider the blast happening close to the surface but on the "side", as much off-center as possible. Won't it evaporate enough material for a jet of it to significantly push the orbit sideways, thus shifting it enough away from a collision course?
The idea is to irradiate and evaporate a slightly larger area "below" the blast, so that more of the ejected matter had the impulse with the direction across the course, obstrucred by the asteroid on one side and thus not symmertical.
(Much if the energy will anyway be wasted on beams / jets that are symmetrical and thus compensating each other.)
No, this was a successful test! Very small changes in the energy of an object can cause large changes in its trajectory. An impact at this same scale could be the difference between a direct collision with Earth, and not even getting inside the moon's orbit. We don't need any mass to be knocked off. In fact, it's probably even more effective if the target stays intact.
What we do need is time. If the asteroid is weeks away, we've got a great chance of deflecting it. If it's hours, we'll certainly be struck.
We'll need decades to install a system that could solve this problem when given weeks of notice. Perhaps those decades of effort will start soon?
Alternatively, if we knew a particular asteroid would threaten us in one decade, that one decade might be enough to do something about it. Many asteroids won't give us that sort of notice, since orbits can have century-long periods.
> A denser rock of iron or similar might be more difficult to divert.
May be, or may be not. But I think it doesn't make it impossible to divert them, even if it is more difficult. The idea is to struck it in a carefully chosen moment, when small differences in delta-v can translate into huge differences in a probability of the impact with Earth.
A pile-of-rubble kind of asteroids seemed the most troublesome, because when you shoot it bullets can just pass through. Or asteroid can break into a lot of pieces amplifying a probability of the impact with Earth: one of pieces can strike Earth and it is can be enough for a catastrophic consequences. But the outcome of an experiment assures us that it is not a case. A lot of small boulders fly on a lot of different trajectories, but they are small, they will burn in atmosphere if they get here.
ps. I feel it is important to state that I'm not an astrophysicist or someone like this, so all written above is my own opinion that can be completely wrong.
All the planning charts and demolition orders have been on display at your local planning department in Alpha Centauri for 50 of your Dimorphos years, so you’ve had plenty of time to lodge any formal complaint and it’s far too late to start making a fuss about it now.
drives me nuts. How long did the orbit originally take? Without this information it very much obscures the point.
Edit: I looked it up
"Before the impact, the orbital period was 11 hours, 55 minutes. It now is 11 hours, 22 minutes. NASA's previous estimate, announced in October, was an orbital change of 32 minutes. The benchmark for success had been set as a change of at least 1 minute, 13 seconds."
So it reduced it by about 1%. Pretty cool.
Edit2: as pointed out correctly by @statusgraph it's actually close to 5%. I fumbled the math on that.
https://www.voanews.com/a/asteroid-bashing-spacecraft-phenom....