FULL STORY at

http://science.nasa.gov/science-news/science-at-nasa/2011/16aug_osirisrex/

10. They retired the space shuttle without a replacement.

Sadly, this is irrelevant, as Shuttle couldn’t get anywhere near an incoming impactor until it was about 10 seconds from hitting the atmosphere.

“We could try blowing it up, but that’s actually a bad idea: at best it creates a lot of debris that can still smack into us, some of which may still be big enough to do us serious harm.”

Common misconception that gets spread around because most people, even scientists, have an irrational fear of nuclear weapons.

Debris from a mass ejection redirection, using a large nuclear explosion, would almost certainly be ejected at meters per second or greater velocities. Almost all of these scraps would quickly spread out past the diameter of the Earth.

It is funny that we are focusing on redirecting a fastball with drops of water, rather than the grenades we already have on hand. Nuclear weapons just are not PC anymore?

There is indeed something to be said for detonating a very large explosive (to billion ton yield) deep within the rubble-pile asteroids or comets. Not only will it vaporize KMs of rock and ice directly, but it will also send the bulk of the object away from the detonation at meters per second or more. More than enough, given a few months warning time, to get the job done.

Clearly you do not know as much about nuclear weapons as you would like to think.

First, the largest warhead ever detonated had a yield of 62 megatons – a factor of 16 smaller than your “billion ton yield”. It was hoped that the device would yield 100 megatons, so clearly we do not have the knowhow to build a “billion ton yield” warhead.

Second, on Earth, nukes are devastating because of the immense shock waves that they create as they superheat the air. In space, there is no air, so they won’t “push” stuff around anywhere near as much as you seem to think.

Third, even if an unfeasibly large device could be built and transported to the rock, let’s see if we can work out what it is likely to do:

A nuke creates, essentially, a lot of radiation. This is emitted all the way up the spectrum from IR to hard X-rays. On Earth, the X-rays cause the air to ionise and become opaque, which (because it therefore absorbs all the other radiation) causes it to heat up immensely and this leads to the phenomenally powerful shock wave. I imagine a nuke does much the same thing to rock, so you really would need to bury your nuke as deep as you can in the asteroid. Once it has vaporised a certain amount of rock, the rock vapour will create pressure in the asteroid and will cause part of it to shatter. The vaporised rock will then expand and act sorta like rocket exhaust, propelling the remaining bits in the opposite direction, and probably causing the asteroid to tumble also. Depending on exactly how the rock shatters or cracks, the chunks of rock (it is unlikely to be blasted into smithereens – most probably there will be a few large pieces and many smaller pieces) could end up being dispersed, or accelerated in such a way that their trajectory will miss Earth, or some of them could end up being accelerated towards Earth. It is messy and unpredictable.

Subsequently, unless the velocity imparted to the pieces exceeds the escape velocity of the asteroid, the chunks are likely to move back together, due to their mutual gravitational attraction.

Basically, detonating a nuke on or in an asteroid has no guaranteed outcome, apart from that the outcome is unpredictable. It depends too much on the properties of the individual rock.

What would it take to capture one of these into geosynchronous orbit or into one of the Lagrange Points? (like Apophis for example as it’s the one that will approach the closest)

More fuel than is really feasible.

Most asteroids that cross Earth’s orbit have a delta-v in the range of 20 – 30 km/sec. That makes 1/2 mv^2 a very large number indeed.

Another thought that I’ve not seen in a movie, or any other discussion would be to plant a probe on the surface of a potentially dangerous rock and fire the engine essentially pushing it over time. Could we think of a thrust mechanism efficient enough to provide enough push? Granted an impact such as the one planned by the ESA would transfer all momentum of the craft into the combined mass of the craft and the rock, but it’s a one shot deal. You don’t get to hit again. With a craft constantly pushing you can increase thrust using of course solar energy to aid this thrust. IDK, it’s a thought.

This is actually considered to be one of the less good options. The reason being, you would need that thrust to go directly through the centre of mass of the rock to avoid making the rock tumble chaotically.

In theory a good project but what if the impact changes actualy changes the asteroid trajectory- towards earth?

I daresay the mission scientists have thought of this already.

Yet, despite this, it’s been an uphill battle to get NASA to pay attention.

What this needs is for some astronomer dude – preferably one who has worked with NASA in the past – to write a book about the dangers posed by stuff hitting the Earth from space.

Common misconception that gets spread around because most people, even scientists, have an irrational fear of nuclear weapons.

Heh, that’s a common misconception. No, it’s because they have a rational understanding of the actual effects of a nuclear weapon and the amount of energy needed to actually disrupt a large impactor. Phil was quite gung-ho about the nuke option in his Bad Universe show (the truth is that many scientists have an irrational love of explosions), but it turns out it just isn’t going to work. Especially not for the rocks big enough for an extinction-level event. Sorry! I was hoping the answer would be as simple as “nuke it!” too!

This is one thing that deep impact and Armageddon actually got right!

LOL! No seriously, I LOLed IRL. That’s just precious. If you think even your hypothetical Gigaton nuke would have a significant effect on a Texas-sized asteroid, much less save us with only months to spare, then it would appear you and Michael Bay share the common misconception that nukes are magical all-explodey devices.

http://scienceblogs.com/pharyngula/2011/08/would_neil_degrasse_tyson_plea.php

In case folks haven’t already seen it on Pharyngula.

What else could we have done with all the money that’s being wasted on things like the bank bail out?

Things like James Webb space telescope – or /and asteroid impact prevention studies.

I’m not at all a Tyson fan – see :

http://blogs.discovermagazine.com/badastronomy/2011/08/05/cosmos-will-hit-the-air-once-again/#comment-403985

& then # 87 on that thread too for why.

However, I do agree completely with what he said there in that one clip.

BTW. Vf gung ovg nobhg gur $ 850 zvyyvba onax onvy bhg zbarl ernpuvat Irahf gehr be abg? Nalbar xabj?

Cut’n'paste into :

http://www.rot13.com/index.php

to decipher. Done to prevent spoilers.

I reckon it’d be easier to get funding happen if the asteroid was proven to have alien life forms on it. Even if they were bacteria-sized.

But I think the saddest thing is that doing these types of things may have other uses sooner: namely, more research and understanding for a future time when we are living in space, or using non-Earth sites for resources. Knowing how to avoid collisions would be applicable not just in the future, but for now, considering the ISS and previous collisions with various objects out there in space. And that’s something that would definitely appeal to the ones in charge.

@R2K

Phil was not referring to the problems of nuclear weaponry, but the fact that something exploding overhead – ie, a giant chunk of rock – produces little chunks of rock that then fall very fast into potentially urban areas. Rocks on fire + houses = damage.

Nuclear or not, doing something like that seems a little silly, especially if you take into account that this doesn’t just include the small asteroids, but the ones that cause mass extinction events. Clouds of ash doesn’t sound like fun, nor does panic, fright or large migrations because of panic/fright/whatever. I’m not a scientist and even I get that. I think I’ll agree with the scientist’s opinion and the ‘common misconception’. PS. You might want to read the BA’s commentary on the movie Armageddon before continuing on; it can be found at his other website, linked to on the right-hand side of this blog.

EDIT: Oops, been beaten to it by Jamey, @25. Also, if I’m wrong, please someone let me know. The above is based on my vague recollection of previous posts on asteroid impacts, but I’m probably off the mark.

The USA & Europe both seem to have their economic woes taking first priority now but I’d love to see Western nations continue investing in science particularly space exploration, development & technology – especially given the threat of extinction that is posed by asteroid impacts generally. Methinks, that *is* an existential threat that Humanity (incl. our Wstern civilisation) does need to take very seriously and find ways of countering without any doubt.

Of course the USA, via its national govt agency NASA even, is still doing *something* asteroid studies~wise currently. After all, it’s got Dawn orbiting Vesta hasn’t it?

This is why I think we need a Lunar base – it serves as a platform for doing more things – things that can lead to much more development of both Luna, and orbital space. And as opposed to the Mars Direct program – if there are problems, a mission can reach the Moon in a couple of days, instead of three months minimum.

Rather than hit the asteroid with a satellite moving at ultra-high velocity (like, what are the odds we could actually impact the rock), carefully maneuver a big nuke into place (stick it with a big wad of space bubblegum).

“This is one thing that deep impact and Armageddon actually got right!”

Armageddon? Congratulations, R2K, you’ve just disqualified yourself from further analysis.

The University of Iowa looked at this 2009-2010. Sending an impactor to do a subsurface detonation is surprisingly hard, due to the speeds involved. The missions literally exceed current technologies, at least if you demand any real reliabilities.

Even without a direct hit, a close nuclear blast isn’t the slam dunk that gawkers and fanboys think it is. As Jamey mentions, small Solar-System bodies don’t just vaporize like in dogfight scenes from sci-fi. For one, both rock and ice (to say nothing of nickel-iron) make good blast shielding.

1. All the mission did was hang a “Mission Accomplished” banner on the asteroid.
2. Successfully invaded the asteroid, but lacked an exit strategy.
3. Congress zeroed the budget halfway through.
4. Asteroid is welcomed because it hastens the end times, Revelation 8:10-11.
5. Republicans feared that allowing the asteroid to be deflected would “give Obama a win”.
6. Asteroid skeptics argued that volcanoes emit more rocks into the atmosphere each year without human extinction.
7. Deep Impact-style rocket named “Messiah” is grounded by ACLU for violating the first amendment.
8. Invisible hand of the market really dropped the ball on this one.
9. Unable to resolve debate over whether it’s an asteroid or a dwarf planet.
10. They retired the space shuttle without a replacement.

A blast on, or within, a rubble-pile body would result in a very small fraction of the body being ejected, while the majority would maintain its self-gravitation and re-settle back in, with the majority of the energy having gone into jostling the pieces around, and pieces scrapping against other pieces, making smaller pieces.

The largest nuclear warhead ever detonated was the Tsar Bomba, a 50 megaton yield device (dialed down from the original 100 megaton design yield). It would vaporise megatons of rock and ice – temporarily – but that would be a hollow of only a few hundred meters – not the kilometers you’re talking about.

Surface detonated, a huge fraction of the energy would be reflected, and again, most of the rest would be dissipated in the fragments jostling around.

This is one of the reasons the gravity tug idea is being considered so strongly – besides allowing for the use of high efficiency, long duration thrusts, the jostling is kept to a minimum as the entire body is affected by the gravitational pull as a unit.

Bigger boom is not always better, unless you get to *REALLY* bigger boom, and then it may cause other problems as well.