Schoolboy Corrects NASA's Math On Killer Asteroid 637
spiracle writes "A German schoolboy, Nico Marquardt, has revised NASA's figures for the chances that the Apophis asteroid will hit earth. Apparently if the asteroid hits a satellite in 2029, its path could be diverted enough to cause it to collide with Earth on the next orbit, in 2036. NASA had calculated the chances as 1 in 45,000 but the 13-year-old, in his science project, made it 1 in 450. NASA agreed." Update: 04/16 16:47 GMT by Z : This is not entirely accurate, it turns out — more details.
No suprise here... (Score:2, Interesting)
So..... (Score:3, Interesting)
Giant laser? Kinetic kill vehicles?
Nuke it from orbit?
Re:In other news... (Score:4, Interesting)
It would interesting if funding in SpaceX and the other alt-space companies went up as a result of this.
Rich people: get us off this rock.
Where's the math? (Score:4, Interesting)
Why did the kid have access to this information?
Re:Not peer reviewed. (Score:2, Interesting)
there's no way this is true (Score:4, Interesting)
Hitting anything in space is like hitting a needle in a haystack. Actually, that's vastly understating it.
There better be an explanation of exactly what it is going to hit and how it will "improve" its trajectory.
Hang on ... (Score:5, Interesting)
Next week: 13 year old boy discovers new chemical reaction in which a combination of scientifically illiterate PR bunnies and sub-editors produces large quantities of bullshit.
Re:Friday the 13th (Score:5, Interesting)
So a little less than 1 Mt St Helens then.
Nonlinear optimization (Score:2, Interesting)
Re:Where's the math? (Score:5, Interesting)
Interestingly, this caused shock in Germany as Germans had regarded themselves as having one of the best education systems in the world. In the US, people are so used to the idea of having a shitty education system that it passed without notice.
wrong wrong WRONG (Score:2, Interesting)
Re:Um, was this by any chance an April Fools paper (Score:2, Interesting)
Re:Hang on ... (Score:3, Interesting)
The satellite would weigh a few tons. The asteroid weighs 21 million tons. The course change won't be that significant. Which is exactly why it's an interesting case -- if the course change was significant, it would miss us by rather a lot. Remember, small changes get magnified by close interactions with other bodies. So a small change while deep in Earth's gravity well changes the exact location it will be in by rather a lot some time later.
As for the Atlantic, don't forget projection distortions -- the bits of the planet near the horizon are less likely to get hit, per unit planet surface area, because they get foreshortened from the perspective of the incoming asteroid.
Re:So if it does hit a sat will we know about it? (Score:5, Interesting)
That's the depressing part.
To answer your question: Probably a few months after the 2027 encounter (and hypothetical collision with the satellite), but at that point, it'll be impossible to do anything about it in the 9 years between 2027 and 2036.
The right strategy is to use the 20 years between now and 2027 to build an orbiter/lander (with a big-ass nuke, nuclear reactor powering a big-ass laser, or big-ass solar sail of reflective/absorptive paint -- and as much as I like nukes, the big can of paint's probably the best way to go -- attached).
We use the 20 years to build the orbiter/lander. We send it up to rendezvous or orbit in 2027. If Apophis smacks into a satellite (or we're just unlucky), we'll have an orbiter and countermeasures in orbit around the asteroid on that pass, and those countermeasures will have nine years in which to do their work. A nuke's pretty cool, but it can't compete with nine years of momentum transfer from the sun shining on a rock painted white on one side and black on the other side.
Suppose we cut it short and by 2027 we still don't have any good countermeasures - just a crappy-ass nuke as a last-ditch measure. Even if we go this route, we've still got 9 years for this orbiter to give us an exact gravity map of this object, and we'll have a couple of years after that to figure out where to land the nuke for maximum trajectory deflection away from the earth. (Hell, if we get the orbiter up there early enough in 2027, we can blow the nuke at/near closest approach to Earth and guarantee a miss in 2036!)
But we're short-sighted. So we'll do nothing between now and 2027. And odds are it'll sail on by in 2027 and we'll conclude that the odds of an impact in 2036 are only one in a few tens of thousands. But what an irony -- if we're wrong, then it'll be too late in 2028 for us to send anything to catch up to the rock and do anything about it. For the sake of a month's pork-barrel spending in Iraq, we'll condemn a few billion of our fellow humans to certain death in 2036.
If it's not Apophis, it'll be some other rock in the next few centuries. Just like the dinosaurs, we'll go extinct because we don't have a space programme. Unlike the dinosaurs, this time around, we'll deserve it.
Re:Hang on ... (Score:4, Interesting)
Yeah, even with the distortion, it's still no better than about 50% to hit the Atlantic (5 time zones = 75 degrees. sin(75/2) = 0.53).
As for the small change, the asteroid is actually ~20 billion tonnes, so its about 5E9 times more massive than a satellite. There is info about its orbit in this table [nasa.gov] correctly. I haven't done the calculations, but my guess is that the ratio of its mazimum possible collision velocity relative to a typical geostationary satellite to its orbital velocity is very small, but lets say 5% (almost certainly a huge over-estimate). That means that the effect of the collision on its orbital velocity is going to be on the order of 1E-11. Now, that's well inside the the errors on the table, so yes, small changes can be amplified, but a change that is significantly smaller than measurement error is not going to change any predictions for where this thing ends up.
Re:Where's the math? (Score:2, Interesting)
What part of TFA lead you to believe that it was a case of NASA scientists not being able to multiply numbers together correctly??? (besides the blatantly misleading title and crappy summary, that is...)
The story itself explains that there was no miscalculation per se. The kid pointed out a factor in their scenario that NASA hadn't considered: given how close the asteroid will pass Earth, what if it hits one or more of our orbiting satellites? The fact that he was mathematically inclined allowed him to recalculate the scenario himself, instead of waiting for NASA's brainiacs to confirm.
His math skills are somewhat incidental to the real story, which is that he has better disaster planning skills than NASA. But that wouldn't be nearly as sensational as implying that even a German schoolboy could add up numbers better than those dumb ol' NASA people.
Re:Damn zeros (Score:2, Interesting)
He would not have the political drive to lie either.
Re:Hang on ... (Score:5, Interesting)
The NASA NEO [nasa.gov] site gives 2.1E10 kg, or 2.1E7 tons -- 21M tons, unless I've screwed up the units somewhere or that site is wrong (both possible :) ).
The same site gives vImpact for Apophis at 12.59km/s. I haven't looked at the approach trajectory in detail, but geosynchronous orbit is only 3.07 km/s, so the relative velocity is dominated by Apophis (moving at less than 12.59, but more than the 5.87 km/s vInfinity; I'm too lazy to work out the exact number). It's orbital velocity wrt the Sun is about the same as Earth's, or 30 km/s -- so the 5-10 km/s collision velocity is 15-30% of its orbital velocity, roughly.
It's a small effect, to be sure, but it has a very, very long lever to work with. I'd be reluctant to say he's wrong without actually doing the math myself in far greater detail than either of us has done here.
Re:Where's the math? (Score:5, Interesting)
What is the error estimate on the precise trajectory of the asteroid and its velocity? How can they arrive at a 400 m window, when they don't even have a good tracking of all the space junk in orbit? How many satelites were taken into consideration in reaching the 1:450 number? Can these really be ignored if the trajectory is to be computed this precisely? Have all the calculations taken into account numerical precision associated with floating point representation? Have the gravitational effects of the other planets been adequately accounted for? With what precision?
Just questions it would be interesting to look at to assess how these figures are arrived at.
It wouold be instructive to see what figures NASA or the German schoolboy used in their equations.
Re:Friday the 13th (Score:5, Interesting)
Re:Friday the 13th (Score:5, Interesting)
Also on the theme of Mount St. Helens, it stopped building the dome inside the crater at about the same time as swarms of earthquakes were detected off the coast of Oregon (usually a precursor to volcanic activity). There are no volcanos in the area the earthquakes were detected, so vulcanologists have ascribed the tremors (reaching 5.5 on the richter scale) to a shift in the magma flow. There was no suggestion - as far as I can tell - that the lack of mountain-building and the earthquakes were linked, but it wouldn't shock me. If that is corrct, then there's an awful lot of molten rock going somewhere - the dome was building a dumptruck's worth of rock per second, according to one quote I saw - and there are a lot of volcanos considered overdue for exploding.
Re:Um, was this by any chance an April Fools paper (Score:5, Interesting)
There, I hope that gave you a flavor. BTW, there is no mention here either of any named individual in NASA or ESA that is standing behind the numbers quoted.
The article is breathless about how wonderfully catastrophic this all is, but I do have some questions about the math. For one, are there really 40,000 satellites in geostationary orbit (or geosynchronous orbit)? That's the quoted number - I was under the impression that there were rather fewer. And how on earth do they get a figure of 1:450 that the satellite will hit one of them? And that that hit will guarantee the catastrophic outcome they so desire?
For another, I'm not getting a picture of a long observational period and multiple telescopes. Only one telescope is mentioned, and the science fair aspect makes it more suspicious. It looks more like a novel hypothesis ("what if it rams a satellite?") combined with some serious guesswork.
And finally, did anybody else get a little bothered by the description of a 160-meter radius asteroid that weighs 200 billion tons? That gives a density of a little under 12 kilograms per cubic centimeter, which would make it a rather unique and valuable material. As near as I can tell, Wikipedia being your friend and all, they missed by three orders of magnitude. Speaking of correcting the numbers...
Apophis is an opportunity, not a threat (Score:5, Interesting)
We are developing several strategies to deflect the course of asteroids. If these mature over the next few years before our close encounters with Apophis, we may have the chance of bringing into Earth orbit, providing nearby and easily accessible resources for space construction.
Providing it with enough energy to slow from solar orbit to Earth orbit could be tricky, so I suggest the best way is to deflected in such a way it undergoes aerocapture.
People always seem concerned about the possibility of the rock just smacking into Earth, and think this is a reason not to pursue such a strategy. Tell me, am I being too Lex Luthor about this?
Re:Friday the 13th (Score:3, Interesting)
Re:Other news stories on this (Score:5, Interesting)
First off... how does a 200,000,000,000 tonne asteroid (200,000,000,000,000 kg) travelling at any substantial inter-planetary speed be deflected by a satellite travelling at 3070 m/s and at most wieghing 10,000kg?
This object is in an orbit which resonates with our own orbit. It is certain to continue close approaches with Earth until either (1) it hits us or (2) is thrown into a totally different orbit, most likely as a result of a very close approach.
Re:Friday the 13th (Score:1, Interesting)
Anyway, in the case of Mt. St. Helens it was a "lateral blast" -- that is, most of the pyroclastic explosion was directed laterally. This was especially bad for conditions on the ground, but made the amount of material expelled into the atmosphere somewhat less than if it had been vertical. On the scale of volcanic eruptions Mt. St. Helens is a piddly little thing. For example, the Mount Pinatubo eruption in 1991 in the Phillipines was much bigger.
In the case of an asteroid impact of this scale the explosion occurs at the end of a shaft of rarified atmosphere produced by the passage of the asteroid. This means the explosion products will shoot back up the path of the asteroid and be much more widely dispersed world-wide. There is also the high chance of a mega-tsunami, which also spreads out the effect.
Apophis is supposed to be ~350m in dimensions. Any way you consider the question the effects would be a whole lot worse than Mt. St. Helens. The effect would definitely be on a global scale.
A more comparable volcanic eruption is Krakatoa which erupted in 1883 and generated a tsunami and climatic effects world-wide -- except that Krakatoa was ~200 megatons equivalent, whereas estimates for Apophis' impact are ~880 megatons, so the explosion is still bigger -- closer to the scale of Mount Tambora (1815). We're talking about an explosion on a scale that would be on par with the biggest ever observed. Even away from the direct impact effects we are talking about widespread/global crop failures as a result of atmospheric dust and cooling. The 1815 "Year Without A Summer" [wikipedia.org] from the Tambora eruption is probably a decent comparison.
It would be a bad day for everybody. On the plus side, it might slow global warming for a few years
Schoolboy's asteroid-strike sums are wrong (Score:5, Interesting)
Re:Other news stories on this (Score:5, Interesting)
I'll play along. I'm qualified to do so on this forum: I've read slashdot for years and I've never studied orbital mechanics or anything else pertinent to the subject.
The original NASA estimate was based on the probability that on the previous orbit Apophis would hit a small window of opportunity that would slingshot it around Earth into the final collision orbit. What the kid did was demonstrate that the window is actually much larger than NASA had first estimated, since collisions with small stuff known to be orbiting the Earth could funnel Apophis into the slingshot zone.
Oh, you wanted a car anology:
Consider a photographer at an auto race who has jumped the safety barrier to get some real good photos of the cars roaring into a hairpin turn. He knows that there is some small risk that a car will spin out as it approaches him and smash him flat, but to his mind it is an extremely low risk. There is only a narrow trajectory that would cause him danger.
But what if a bunch of ball bearings had been strewn onto the track in front of the curve? That changes the whole equation: if a race car teetering on the verge of spinning out hits one of these, it is much more likely to plow into the luckless photographer. The range of dangerous trajectories is much wider than the photographer estimated, since the track is not as clean as he pictured it in his mental model.
Re:Other news stories on this (Score:3, Interesting)
Yes, but a strike from a satellite will impart certainly less than 1mm/s. And you're talking about your senior design program. This is a schoolboy we're talking about here. I doubt he has bested you.
I remain skeptical of this story. I'd like to see it *researched* and reported by a reputable source. I'd like to see it posted on a NASA website. So far, what I've seen is that what amounts to a tabloid posted the story and some other news agencies have parroted it, apparently without doing any original research.
I think this story is a hoax.