Asteroid Protection

[Ian Robinson]

Originally Posted by bojan

You are wrong mate, I am not watching Hollywood movies at all.
I am just proposing a method which seems plausible to me (prompted by someone else's (and quite correct) opinion that nuking in vicinity or from surface wont necessarily produce enough impulse to nudge asteroid sufficiently into safe(r) orbit.
Since I know something about explosives, I just proposed the idea to go there, bury the explosive devices on appropriate places and deep enough and this way produce significant multiple shock wave which may move the asteroid enough from the collision orbit.
If it does not work, it does not work.
Anyway, only proper computer modelling would give a correct answer to the question which method is most appropriate for a specific case.

Use of nukes against asteriods is a very unwize approach , the last thing you want is to turn one big impactor into a bunch of smaller impactors (even if you could get the nuke/s to the asteroid in time and make a dent on it .... we are talking billions of tonnes moving at 10 - 80 km per second velocity). Scattergunlike impacts all over the plant - not good.
The best you can expect is to warm some of it's surface , in space there is no atmosphere or anything rigid to react against in the detination or an atmosphere to propogate an explosion front , unlike in a terrestrial context. You'll just get a flash of light and heat and you'll irradiate some of the surface. So - back to the drawing board.

Best we can hope for is for a impactor to hit land somewhere on the other side of the planet and hope we can survive the "winter" which will result (over a few months or years , if it lasts longer than a year of so) and the resource and food wars that will most likely result as those who can try to take the food reserves of those who have them - we are likely to be cactus as a species.

If it hits an ocean - that will be very bad news globally no matter which ocean it lands in.

[bojan]

Originally Posted by Ian Robinson

..... in space there is no atmosphere or anything rigid to react against in the detination or an atmosphere to propogate an explosion front , unlike in a terrestrial context. You'll just get a flash of light and heat and you'll irradiate some of the surface. So - back to the drawing board.

Well.. what I proposed was to bury explosive devices underground of potential impactor at appropriate depth....
The heat from nuclear explosion (and there is a lot of it) will evaporate the surrounding material (and therefore produce high pressures) which will possibly move the fragments above explosion centre and thus produce the necessary impulse.. perhaps small in terms of scale of the asteroid, but possibly adequate (if there is enough time left before impact, and if asteroid is small enough). If we have more of those explosions, initiated with appropriate timing, the impulse will build up. Possibly this will be enough.
I do not think that this is the cowboy-style approach to the problem.
In perils like this no method should be dismissed just because it is nuclear (is this a new "dirty" word?) ..
And of course, any other ways should be investigated carefully and methodically.
But first of all, we have to find that impactor.. and then see what can be done about it, if anything is possible to do at all...

[Ian Robinson]

Originally Posted by bojan

Well.. what I proposed was to bury explosive devices underground of potential impactor at appropriate depth....
The heat from nuclear explosion (and there is a lot of it) will evaporate the surrounding material (and therefore produce high pressures) which will possibly move the fragments above explosion centre and thus produce the necessary impulse.. perhaps small in terms of scale of the asteroid, but possibly adequate (if there is enough time left before impact, and if asteroid is small enough). If we have more of those explosions, initiated with appropriate timing, the impulse will build up. Possibly this will be enough.
I do not think that this is the cowboy-style approach to the problem.
In perils like this no method should be dismissed just because it is nuclear (is this a new "dirty" word?) ..
And of course, any other ways should be investigated carefully and methodically.
But first of all, we have to find that impactor.. and then see what can be done about it, if anything is possible to do at all...

Straight from Hollywood.

So , considering we can't even get astronauts even out of low earth orbit now , and have only managed to get robots not much bigger than a kid's tricycle onto another planet in recent years and most of these have - missed the target planet , or crashed and burned , or simply failed and sailed past the target PLANETS on into infinity , how will we get a drilling rig and astronauts (cant trust a robotised rig in critical mission like this that the survival of humanity might depend on) safely to the asteroid's surface perhaps several million or even hundreds of millions of km from earth (depending on its orbit and velocity) ?
just how is that feat going to be achieved ?
not to mention getting any sort of substantial drilling rig and the astronauts safely onto an asteroid's surface ? and then there is the problem of working at drilling boreholes in the surface of the asteriod deep and broad enough to plant enough thermonuclear mines of sufficient power to make any difference when the nukes are detinated (not talking little firecrackers of a few MT yield here - probably need nukes with yields in GT yield class to even dent dangerous asteriods , and all this under zero or microgravity ?
And who are we going to trust to develop such powerful nukes - and where will they be tested ?

Brute force is not the answer and is unlikely to work.

The most promising proposals I have heard are to harpoon the asteriod on flyby of a space craft and thereby attach a humungous solar sail to it, and to sail it slightly off trajectory over several years , or to set up a humungous rail gun , or several of them on the moon's surface and fire large very high kinetic energy (ultra high velocity) projectiles at the asteriod , mining the raw materials on the moons surface and making them insitu , and firing them at the asteriod at velocities that are very high , in order to impart enough kinetic energy to change the asteriod's velocity enough for it's orbit change slightly though enough to miss the earth.

[bojan]

Originally Posted by Ian Robinson

Straight from Hollywood.

Ian,
Please do not mention Hollywood again...
We are talking about scenarios here, yes, but not for crappy movies.

[jungle11 (Greg)]

I guess by what I hear we need lots..and lots..of planning and testing. Which isn't happening, or at least not being followed through.
Seems more effort will be put into a few fellas walking around on Mars, than preparing for the possibility of an asteroid impact on Earth - go figure.

Perhaps you could be a little more thoughtful of others opinions Ian?

[theodog (Jeff)]

Hi All,
I can't seem to open the article
http://news.bbc.co.uk/2/hi/science/nature/7760659.stm
but it seems most of the discussion is on saving Earth. Firstly we have to find these buggers if we are to deal with them.
Try observing some of the objects on this form and do your bit for our future.
http://scully.cfa.harvard.edu/~cgi/NEAObs
Once they are found and their orbits determined, I doubt if Hollywood would want to know.
So much money is spent on volcanoes, earthquakes and pridicting sunamis yet these are really localised problems compared with an asteroid strike.

Get to it and man those cameras and eyepieces, amateurs can make a difference!!

[timb (Tim)]

Originally Posted by Ian Robinson

Straight from Hollywood.

So , considering we can't even get astronauts even out of low earth orbit now , and have only managed to get robots not much bigger than a kid's tricycle onto another planet in recent years and most of these have - missed the target planet , or crashed and burned , or simply failed and sailed past the target PLANETS on into infinity , how will we get a drilling rig and astronauts (cant trust a robotised rig in critical mission like this that the survival of humanity might depend on) safely to the asteroid's surface perhaps several million or even hundreds of millions of km from earth (depending on its orbit and velocity) ?
just how is that feat going to be achieved ?
not to mention getting any sort of substantial drilling rig and the astronauts safely onto an asteroid's surface ? and then there is the problem of working at drilling boreholes in the surface of the asteriod deep and broad enough to plant enough thermonuclear mines of sufficient power to make any difference when the nukes are detinated (not talking little firecrackers of a few MT yield here - probably need nukes with yields in GT yield class to even dent dangerous asteriods , and all this under zero or microgravity ?
And who are we going to trust to develop such powerful nukes - and where will they be tested ?

Brute force is not the answer and is unlikely to work.

The most promising proposals I have heard are to harpoon the asteriod on flyby of a space craft and thereby attach a humungous solar sail to it, and to sail it slightly off trajectory over several years , or to set up a humungous rail gun , or several of them on the moon's surface and fire large very high kinetic energy (ultra high velocity) projectiles at the asteriod , mining the raw materials on the moons surface and making them insitu , and firing them at the asteriod at velocities that are very high , in order to impart enough kinetic energy to change the asteriod's velocity enough for it's orbit change slightly though enough to miss the earth.

Your objections are to a strawman and your alternative is fanciful. Missiles that hit things, burying themselves a few meters then blow-up are a well developed terrestrial technology that could easily be adapted for use in space. Missiles are generally unmanned. A nuclear explosion occurring meters below the surface of an asteroid would (conservatively) send thousands of tons of rock moving away from it at hundreds of meters per second. This would change the orbit of the asteroid as a consequence of Newton's laws of motion. I don't know of any other way to impart such a large impulse to an asteroid in a sub-decadal period.

The alternatives you suggest depend on unproven technologies, would have large lead times, or would be enormously more expensive. It's ironic that you object to nuking an asteroid on the grounds that "we can't even get astronauts even out of low earth orbit now" then propose as an alternative that we "set up a humungous rail gun... on the moon's surface and fire large ... projectiles at the asteriod , mining the raw materials on the moons surface and making them insitu".

[xelasnave]

Welcome to iceinspace from me Tim and I think you should be on the committee to review the matter.
Thanks for your contribution.
best wishes
alex

[xelasnave]

Anyways why worry ..extinction is the rule and evolution the exception that runs while the rule sleeps... one day humans will be extinct I suspect then we wont need to worry.
alex

[timb (Tim)]

Originally Posted by xelasnave

Welcome to iceinspace from me Tim and I think you should be on the committee to review the matter.
Thanks for your contribution.
best wishes
alex

I thank you. I'm unfortunately only a swivel chair astronomer but I do try to keep abreast of what's happening in the literature using sites such as arxiv and adsabs. I heard about this forum on BAUT where I am a regular if low volume contributor.

[higginsdj]

The biggest misconceptions about the various approaches seems to be the understanding of how explosives work in space. Explosives get their power from pressure waves. Pressure waves are the compression of air/gas. There is no air in space thus there are no pressure waves and no 'explosions'. BUT there may be water/ice in the asteroid (lets face it rubble piles are glued together with ices) so some amount of expansion is expected due to heating. Now I admit that I am no expert but this is how it was explained to me by various scientists in the bis.....

What explosives will do is generate heat. Heat will evaporate material and the radiation/evaporation of material will have an impulse effect on the asteroid BUT it is slow and weak process (ie think YORP and Yarcovsky effects) - it is not an instantaneous effect. We then need to consider what effect such an approach will have on a rotating body. Equatorial placement then perhaps is of little value but placement on the poles are an option.

Of course the explosive does not need to be buried and to avoid any chance of shattering the asteroid (heating/expansion of gases on a monolithic asteroid - as opposed to rubble piles which can withstand almost any impact energy) a surface or above surface detonation is idea and real option. And, of course, it needs to be done long before the asteroid is going to hit us. This does NOT mean a long distance from us - ie it can be done on an earlier orbit when it is close to us.

The real problem cases are the objects we plot an impact trajectory on their first apparition. Probably not a lot we can do with these at the moment since, by the time we have calculated the orbit precisely enough to know it's an impactor, it will be too close to do anything about.

[Wavytone]

Don't worry about things you cannot do anything about.

When we can detect an impactor with sufficient time - and the technology - to do something about it, THAT is the time to start worrying.

There remains the question if there is an impact as to whether you should want to survive it. Possibly not.

[Ian Robinson]

http://www.youtube.com/watch?v=-zvCUmeoHpw

One to enjoy that I came across by accident.... good thing there are no 500km diam asteriods out there with earth's number on them.... now 500km diam comets .... maybe.... they'd be another matter and may well pose a threat.

Remember what rather smaller fragments did to Jupiter

Sorry .... there's no credence of any likely impact by a monster comet or asteriod or any other body in 2012. Despite what the believers in Nibiru claim , or what Nostradamus is supposed to have said.

[renormalised (Carl)]

Big difference between comparing an impact on Jupiter (Shoemaker-Levy) and one on Earth, that the professionals temporarily forgot in their awe of the spectacle. That's the physics of an impact on Jupiter are somewhat different to here. Namely, the energy of a Jupiter impact is being dissipated on a planet that is essentially a huge ball of gas. Whereas on Earth, much of the energy of the impact is dissipated into a solid body. Only a fraction of the total impact energy is released into the atmosphere. That's why they detonate nukes over a target at altitude, the effects are far more devastating than for a ground burst. On Jupiter, which has no real solid surface to speak of, all the energy of the impacts was dissipated into the atmosphere and hence very spectacular. On Earth a similar set of impacts, whilst extremely devastating, would have most of their energy absorbed by the body of the planet. You'd have a chain of craters, but most of the explosive energy would end up as very large seismic waves in the body of the planet and molten rock both in and around the craters, plus atmospheric dust. When the scientists viewed SL, they got carried away with what they saw, which was damn impressive, and then blurted out pronouncements without thinking clearly first. Mind you, having a series of large objects collide with the Earth is not my idea of a fun day at the park. We'd be pretty much cactus...and I mean the entire planet by that. One impact would be bad enough, especially from a large object. We might get another K-T event. But, a series of medium to large impacts might bring on a Permo-Triassic type of event which means 80-95% of all life would be cactus. Cockies might inherit the Earth after all

[Astro78]

I for one have enormous faith in our scientific community to solve these potential disasters. What we are achieving in space is absolutely remarkable and something to be immensely proud of.

What's that saying - 'need is the mother of invention'

[renormalised (Carl)]

Originally Posted by Astro78

I for one have enormous faith in our scientific community to solve these potential disasters. What we are achieving in space is absolutely remarkable and something to be immensely proud of.

What's that saying - 'need is the mother of invention'

I have all the faith in the world for the scientist, but I have no faith at all in the politicians and beaurocrats who will have to implement such a program.

It's these people who will do nothing about it, until it's too late. At least so far as the general population goes....you can bet pounds to peanuts they'll have everything setup for themselves, just in case.

[ngcles]

Hi All,

The BBC news article is incorrect to a small extent at least.

It says:

"They say the next major threatening event could occur in less than 20 years. Asteroid Apophis is due to pass close to the Earth and analyses suggest a one in 45,000 chance of a collision."

There is zero chance Apophis will strike the Earth in 2029. It will pass by very closely and I seem to remember that it will brighten to 3rd magnitude at closest approach, but it will not hit us in 2029.

It is a slightly different story for 2036. If (and that is a very very big if) it manages to pass through a "keyhole" only 600m wide during the 2029 pass, there is a chance (something like 1/45,000) that it will hit Earth in 2036. So no real need to be super-alarmed about Apophis -- for the moment.

I do agree that we need a contingency plan for a threat of this type and is a good argument to stage several test missions to several different asteroids to try this, that and the other to see if an orbit can be altered.

I seem to remember reading somewhere that if we had enough time, applying a reflective surface to [I]one side[I] of the "rogue asteroid" (I can just see that term being used in the papers) would produce an effect like the solar-sail -- enough (over several months) to just nudge it out of the way with radiation pressure.

Best,

Les D

[renormalised (Carl)]

Sort of a super sized Yarkovsky Effect.

[jjjnettie (Jeanette)]

I rest easy knowing that our Dennis is keeping a close eye on any asteroids that are nearby.