Asteroid 2012-DA14 will pass within 17,200 miles of Earth at 18,000mph

Captain Chaos

littlemac1980 wrote: »

Right - I'm no expert, but (unless I'm incorrect) it appears that the DA14 asteroid, has an orbit that generally is very similar to that of earths, both in terms of distance from the sun and the orbital period. I got that info from wikipedia so correct me if I'm wrong.

So, first of all, despite what people say about the difficulty spotting something like this in the vastness of space. It appears to me that this one wasn't just in our backyard, or even on the back porch, it was pretty much on the armrest of the couch in our living room. How was it not spotted before 2012? It must have been there for as long as we have been developing the technology to explore and view space.

We are sending probes to explore the outer reaches of the solar system and beyond - which I am delighted with - but this rock, couldn't have possibly come any closer to an impact and potentially killing millions of people and we didn't even know it was there until last year.

Secondly - how many more similar objects are there in the immediate vicinity of the Earth?

Thirdly - what are its origins (their origins) given the proximity to Earth and the similar orbital pattern, it is possible it was connected to the Earth or the formation of the moon, etc.

Fourthly - why are we not sending probes to such objects given they are literally a stones throw from us?

DA14 orbits in the vertical plane of motion relative to Earth so it only sort of connects with our orbit at 2 points. Given it's orbit and size, very easy to miss. It will be a long time before we ever cross again.

We are sending probes to asteroids, both NASA and Japan have done so and are still in those missions.

littlemac1980

Captain Chaos wrote: »

DA14 orbits in the vertical plane of motion relative to Earth so it only sort of connects with our orbit at 2 points. Given it's orbit and size, very easy to miss. It will be a long time before we ever cross again.

We are sending probes to asteroids, both NASA and Japan have done so and are still in those missions.

Thanks for the response, I was aware of the Japanese mission, but until now I really hadn't understood that there were a number of asteroids orbiting the sun at such a similar distance to earth.

I had always been under the impression that all asteroids (in orbit of the sun) were either in the belt between Mars and Jupiter, or else had entered orbits which had a Perihelion (if thats the correct term) that was at least hundreds of AU away - Thus with extremely long periods that would make trying to track them almost impossible at our current level of technology.

However, while I accept your point that Asteroids of this size are extremely difficult to spot. It seems to me that the predominant reason why that is the case is simply because we are not actively looking for them.

I accept that this had a vertical orbit as you say which would limit its immediate proximity to Earth, but the furthest it could ever be from us would seem to be about 2 AU, which I would have thought would make it detectable were one looking in the right place.

My concern is that this was only discovered last year, and came so ridiculously close to causing a catastrophe the scale of which none of us could begin to imagine - just take the sonic boom from the Russia Incident as an example of how unexpected the consequences of something the scale of a DA14 impact could have been. Who's to say what we might discover tomorrow in our solar vicinity and what likely trajectory such an object might have in a years time.

I fully understand that it is difficult to spot such objects, but I believe that task is made all the more difficult if all our space resources are targeted at the discovery of hypothetical planets in other solar systems light years away, or our greatest scientific endeavors remain focused on trying to fit anomalous infra-red echoes from billions of light years away to theories of the origins of the universe.

I know people will argue that the recent leaps in space exploration, observation and theories are of huge significance for our understanding of how the universe, our solar system, and planet were created, but all that is really of little value if we're all wiped out by a piece of rock that was idling around beside us for the last few hundred years waiting for us to detect it if we'd only bothered to have a serious look.

Zubeneschamali

kevc2 wrote: »

I took a photo of an object moving across the sky at 7:26PM on the 15th.

Probably a satellite. Check www.heavens-above.com How long did it take to cross the sky, and in which direction?

kevc2

Zubeneschamali wrote: »

Probably a satellite. Check www.heavens-above.com How long did it take to cross the sky, and in which direction?

Thanks for getting back to me. It looked a lot brighter than a satellite and lower in the sky. Judging by google maps, I would say I seen it from South West to South in the sky and took around 2 minutes to cross the sky. I will check that site out now thanks.

kevc2

Zubeneschamali wrote: »

Probably a satellite. Check www.heavens-above.com How long did it take to cross the sky, and in which direction?

I don't think it was a satellite going by that website.

Zubeneschamali

kevc2 wrote: »

I would say I seen it from South West to South in the sky and took around 2 minutes to cross the sky.

Definitely not the Asteroid, then, which would have taken hours to move from the NE horizon to the North.

tricky D

littlemac1980 wrote: »

I had always been under the impression that all asteroids (in orbit of the sun) were either in the belt between Mars and Jupiter, or else had entered orbits which had a Perihelion (if thats the correct term) that was at least hundreds of AU away - Thus with extremely long periods that would make trying to track them almost impossible at our current level of technology.

However, while I accept your point that Asteroids of this size are extremely difficult to spot. It seems to me that the predominant reason why that is the case is simply because we are not actively looking for them.

That asteroid belt is only a concentration of them. Asteroids are all over the Solar System as they get bumped and pulled into all sorts of trajectories and orbits.

As for tracking them and only seeing them 'late', they are generally too small, too dark and too distant to be seen until they are nearby. There's not much that can be done about that.

littlemac1980

tricky D wrote: »

That asteroid belt is only a concentration of them. Asteroids are all over the Solar System as they get bumped and pulled into all sorts of trajectories and orbits.

As for tracking them and only seeing them 'late', they are generally too small, too dark and too distant to be seen until they are nearby. There's not much that can be done about that.

Fair enough, and thanks for your comments but I think you're missing the point of my post.

I understand they are tricky to spot, but I'm making the argument that we're neglecting to properly look for them, especially the ones that are near.

DA14, while it is impossible to be sure what is was upto pre-discovery was in all probability in an orbit that never took it further away than 2 AU from Earth for perhaps hundreds or thousands (perhaps even millions) of years.

You say that "...there's not much that can be done about discovering these objects". What I'm saying is that if we're not spotting objects like DA14 until they are within fractions of an AU of Earth, then I believe we are focusing our resources in the wrong places for now. That's something that can be done.

shedweller

kevc2 wrote: »

I took a photo of an object moving across the sky at 7:26PM on the 15th.

I thought it might have been the ISS:http://spaceflight.nasa.gov/realdata/sightings/cities/view.cgi?country=Ireland&region=None&city=Dublin#.USOYC2cyLIE

But it only goes back a few days.

ps200306

littlemac1980 wrote: »

Fair enough, and thanks for your comments but I think you're missing the point of my post.

I understand they are tricky to spot, but I'm making the argument that we're neglecting to properly look for them, especially the ones that are near.

DA14, while it is impossible to be sure what is was upto pre-discovery was in all probability in an orbit that never took it further away than 2 AU from Earth for perhaps hundreds or thousands (perhaps even millions) of years.

You say that "...there's not much that can be done about discovering these objects". What I'm saying is that if we're not spotting objects like DA14 until they are within fractions of an AU of Earth, then I believe we are focusing our resources in the wrong places for now. That's something that can be done.

I think you are underestimating a) the success already achieved, b) the magnitude of the task to be completed.

There are two main ground-based NEO detection programs -- LINEAR and Catalina, and there has been one major space-based one, WISE.

It's estimated that there is only a handful of near earth objects greater than 1km diameter still to be discovered. At the other end of the scale, we may know about less than 20% of the sub-1km objects. Finding these is not a stroll in the park. The sky is a big place. These objects are, relatively speaking, tiny.

Also, when you we say "we are focusing our resources in the wrong places"... who's "we"? This stuff has to be paid for, and to get funding it has to justify itself. It is estimated that there is a Tunguska-style (> 10 Mtonne) event only once every thousand years. And the chances of it hitting a populated area are slim. So why would "we" devote the entire world's telescopic resources to the task, and who would pay for it anyway?

littlemac1980

ps200306 wrote: »

I think you are underestimating a) the success already achieved, b) the magnitude of the task to be completed.

There are two main ground-based NEO detection programs -- LINEAR and Catalina, and there has been one major space-based one, WISE.

It's estimated that there is only a handful of near earth objects greater than 1km diameter still to be discovered. At the other end of the scale, we may know about less than 20% of the sub-1km objects. Finding these is not a stroll in the park. The sky is a big place. These objects are, relatively speaking, tiny.

Also, when you we say "we are focusing our resources in the wrong places"... who's "we"? This stuff has to be paid for, and to get funding it has to justify itself. It is estimated that there is a Tunguska-style (> 10 Mtonne) event only once every thousand years. And the chances of it hitting a populated area are slim. So why would "we" devote the entire world's telescopic resources to the task, and who would pay for it anyway?

While you certainly have a good deal more knowledge than I do of the amount of resources available and extent of success already achieved in identifying NEO's, and while I appreciate your comments, I think that you're argument actually tends to support my position.

You repeatedly refer to estimates of:

1. The amount of large NEO that have been discovered - you say it is estimated there are only a handful remaining to be spotted.

2. The amount of unknown NEO of a diameter < 1km - you say is estimated at about 80%

3. The probabilities of Tunguska-Style events - you say is estimated at about 1 every 1000 years.

Now I understand that its reasonable to make estimations - particularly in relation to events - the probabilities of occurrence of which are quite difficult to predict - And I fully accept that the likelihood of a catastrophic event are quite remote, at least that appears to be the case based on what we know.

I may be incorrect, but I understand that the Tunguska event is hypothesized to have been caused by a meteor far smaller than 1 km in diameter - therefore one of which in your estimation, it is estimated we (The Global Community) have only discovered about 20% of those that are out there.

While predictions regarding occurrence probabilities tell us something of the likely frequency of a particular type of event recurring over an artificially long period of time, they don't offer any insight into predicting when on that time line such events may occur. Such an event is as likely to occur tomorrow as it is to occur in 500 years time.

The recent events, where not one but two major interaction events with NEO of a very significant scale occurred on the one day - one of which we were completely unaware of - sustantiates my above point.

Another issue with the three estimates you have provided is that they are connected and therefore a margin of error in one would have an impact on the degree of precision in the other - in so far as estimates can be in any way precise.

What I am saying is that the estimates that there are only a handful of NEO's over 1km out there, can't be substantiated (though I understand it unlikely there are hundreds), but its far more likely that we may only be aware of 5 % of the NEO's of size <1km.

Of course even that % can't be substantiated - and it may be the case that we have spotted 40% who knows. As you say, and of course I agree, they are very difficult to spot.

However, as difficult to spot as they are, they are not impossible to spot if you are looking in the right place.

Space is a big place, as you have correctly pointed out, attempting to scan the entire of our immediate Solar neighbourhood is of itself a mammoth task, more so with only three dedicated small scale programs to do so.

I'm not suggesting that all the worlds scientific instruments should be redirected to such a task. That would make little sense, there are plenty of instruments which have been designed and built in such a way that they couldn't contribute to such a project.

What I am suggesting (arguing) is that three dedicated programs isn't enough, that a global cooperative effort of a far more significant scale is what is required.

The 'We' I referred to - though I expected it would be obvious, given the context of the discussion - are the Global Communty of Space Organisations, and Government funded projects, funding etc., semi-amateur, amateur observers - basically any interest and capable party or organisation. (again I'm sure you have a better knowledge of the extent of those).

Again I'm not suggesting that we should drop all tools so to speak and all turn to look for NEO's but I am suggesting that recent events should be used as an impetus for a concerted effort, and an intesification of NEO identification particulary of those < 1km.

I'm not suggesting that we could ever achieve 100% knowledge of those category of NEO's however I believe recent events have shown our level of knowledge is vastly lacking and that an estimated 20% is far too low.

A concerted effort among the global community with a specific objective of increasing dramatically our estimated awareness of NEO's is what I'm suggesting, not that we stop communicating with Curiosity.

Space is a big place, and the NEO's are very small, but 10 Telescopes can get the job done better and quicker than 3.

ps200306

Certainly, ten telescopes can do more than three.

Two, actually -- WISE only had a two-year life span in space. And Catalina has largely taken over from LINEAR, so really it's one. But Catalina is a wide angle telescope, somewhat akin to the Sloan Digital All-Sky Survey. So it is the more efficient by far.

But nevertheless, ten more telescopes would find more NEOs, certainly. And why stop there? Why not a hundred? A thousand? Simple answer is that resources are rationed, and somebody decided on one, rather than ten or a thousand. Who is to say how much is enough?

One way to answer that is with another question. What would we actually do if we saw "the big one" heading for earth tomorrow? The short answer is nothing. We don't know how to stop an asteroid. A dense one kilometre asteroid weighs two billion tonnes. That's more than a 5,000 foot mountain. Imagine a 5,000 foot mountain doing 20,000 miles per hour. Even if you could chase it down and hit it with a nuclear bomb, you would have no certainty of deflecting it.

We're like a dog chasing a car. Rather than putting all our energy into the chase, at some point we have to think about what we're going to do if we catch it.

littlemac1980

ps200306 wrote: »

Certainly, ten telescopes can do more than three.

Two, actually -- WISE only had a two-year life span in space. And Catalina has largely taken over from LINEAR, so really it's one. But Catalina is a wide angle telescope, somewhat akin to the Sloan Digital All-Sky Survey. So it is the more efficient by far.

But nevertheless, ten more telescopes would find more NEOs, certainly. And why stop there? Why not a hundred? A thousand? Simple answer is that resources are rationed, and somebody decided on one, rather than ten or a thousand. Who is to say how much is enough?

One way to answer that is with another question. What would we actually do if we saw "the big one" heading for earth tomorrow? The short answer is nothing. We don't know how to stop an asteroid. A dense one kilometre asteroid weighs two billion tonnes. That's more than a 5,000 foot mountain. Imagine a 5,000 foot mountain doing 20,000 miles per hour. Even if you could chase it down and hit it with a nuclear bomb, you would have no certainty of deflecting it.

We're like a dog chasing a car. Rather than putting all our energy into the chase, at some point we have to think about what we're going to do if we catch it.

Just think we'd have a better chance of figuring out what to do, if we saw it coming.

ps200306

littlemac1980 wrote: »

Just think we'd have a better chance of figuring out what to do, if we saw it coming.

Oh I dunno ... one 20,000 mph mountain is much the same as the next.

Merch

ps200306 wrote: »

Certainly, ten telescopes can do more than three.

Two, actually -- WISE only had a two-year life span in space. And Catalina has largely taken over from LINEAR, so really it's one. But Catalina is a wide angle telescope, somewhat akin to the Sloan Digital All-Sky Survey. So it is the more efficient by far.

But nevertheless, ten more telescopes would find more NEOs, certainly. And why stop there? Why not a hundred? A thousand? Simple answer is that resources are rationed, and somebody decided on one, rather than ten or a thousand. Who is to say how much is enough?

One way to answer that is with another question. What would we actually do if we saw "the big one" heading for earth tomorrow? The short answer is nothing. We don't know how to stop an asteroid. A dense one kilometre asteroid weighs two billion tonnes. That's more than a 5,000 foot mountain. Imagine a 5,000 foot mountain doing 20,000 miles per hour. Even if you could chase it down and hit it with a nuclear bomb, you would have no certainty of deflecting it.

We're like a dog chasing a car. Rather than putting all our energy into the chase, at some point we have to think about what we're going to do if we catch it.

I saw a good programme after recent events.
it was about the possibilities
They were saying, preferably this needs to be done further out, but was talking about reflecting light with mirrors (large arrays of mirrors) off objects to try shift where they are going. Make them give off gasses that propel itself fractionally further out. That assumes the material the object is made of will respond according to how we want.

That also still means seeing the object far enough in advanced, then designing, building, launching such a vehicle, getting it where its needed and assuming it gets past all those hurdles , that it then works and said rock is diverted.
If one turns up on our doorstep we're probably screwed.

littlemac1980

ps200306 wrote: »

Certainly, ten telescopes can do more than three.

Two, actually -- WISE only had a two-year life span in space. And Catalina has largely taken over from LINEAR, so really it's one. But Catalina is a wide angle telescope, somewhat akin to the Sloan Digital All-Sky Survey. So it is the more efficient by far.

But nevertheless, ten more telescopes would find more NEOs, certainly. And why stop there? Why not a hundred? A thousand? Simple answer is that resources are rationed, and somebody decided on one, rather than ten or a thousand. Who is to say how much is enough?

One way to answer that is with another question. What would we actually do if we saw "the big one" heading for earth tomorrow? The short answer is nothing. We don't know how to stop an asteroid. A dense one kilometre asteroid weighs two billion tonnes. That's more than a 5,000 foot mountain. Imagine a 5,000 foot mountain doing 20,000 miles per hour. Even if you could chase it down and hit it with a nuclear bomb, you would have no certainty of deflecting it.

We're like a dog chasing a car. Rather than putting all our energy into the chase, at some point we have to think about what we're going to do if we catch it.

Well I don't think your analogy accurately reflects my point, and again I think you've inadvertently supported my argument.

If we spotted a 5000ft mountain (NEO) tomorrow hurtling toward space in two - three weeks time, there is little we could do - correct! The discussion re intercepting with a nuclear missile was gone through in the Russian post previously and was correctly, in my view (yours also it seems) decided as being near impossible with our current level of technology, and of little practical benefit at that time anyway.

However, spot a similar sized object or smaller (lets not get away from the fact that I'm suggesting intensification of spotting NEO's of <1km in diameter and much less - consider the recent interactions as demonstrative of the type of NEO's I'm talking about)... So spot a similar sized object 50 years in advance of a likely impact, and well that's a completely different ball game - not really a dog chasing a car scenario... (they don't aim to catch cars anyway), or even 20 years in advance.

I'd be very confident that 'we' (there's that word again) could develop a strategy to appropriately deal with such an event in a manner that would significantly reduce the likely damage caused, and perhaps figure a way to deal with it altogether in that time period.

Let's not forget I'm talking about NEO's like DA14 - that are located in an area of our solar system within 2AU's or thereabouts of Earth. Plenty of opportunity to intercept/land etc.

Let me put it to like this - what if DA14 was on a direct collision course with Earth last Feb 15th, God knows what damage would have been caused - but no matter where it impacted the consequences would have been tremendously devastating. Those of lucky not to have been affected would still be checking Youtube videos of the Impact etc.

By the time we spotted it last year - would have been too late to do anything about it.

However if we had spotted it in the mid eighties, we'd have known it was gonna hit in 2013, and I doubt very much we couldn't have dealt with it in space in the meantime.

Daffodil.d

littlemac1980 wrote: »

Well I don't think your analogy accurately reflects my point, and again I think you've inadvertently supported my argument.

If we spotted a 5000ft mountain (NEO) tomorrow hurtling toward space in two - three weeks time, there is little we could do - correct! The discussion re intercepting with a nuclear missile was gone through in the Russian post previously and was correctly, in my view (yours also it seems) decided as being near impossible with our current level of technology, and of little practical benefit at that time anyway.

However, spot a similar sized object or smaller (lets not get away from the fact that I'm suggesting intensification of spotting NEO's of <1km in diameter and much less - consider the recent interactions as demonstrative of the type of NEO's I'm talking about)... So spot a similar sized object 50 years in advance of a likely impact, and well that's a completely different ball game - not really a dog chasing a car scenario... (they don't aim to catch cars anyway), or even 20 years in advance.

I'd be very confident that 'we' (there's that word again) could develop a strategy to appropriately deal with such an event in a manner that would significantly reduce the likely damage caused, and perhaps figure a way to deal with it altogether in that time period.

Let's not forget I'm talking about NEO's like DA14 - that are located in an area of our solar system within 2AU's or thereabouts of Earth. Plenty of opportunity to intercept/land etc.

Let me put it to like this - what if DA14 was on a direct collision course with Earth last Feb 15th, God knows what damage would have been caused - but no matter where it impacted the consequences would have been tremendously devastating. Those of lucky not to have been affected would still be checking Youtube videos of the Impact etc.

By the time we spotted it last year - would have been too late to do anything about it.

However if we had spotted it in the mid eighties, we'd have known it was gonna hit in 2013, and I doubt very much we couldn't have dealt with it in space in the meantime.

Everytime those documentaries are on tv highlighting what would happen if we had an impact I always feel like the whole thing has been unfinished but I recently saw one on discovey that went into the future and imagined what life would be like after an impact. This particular one wasn't about an impact per say but is still relevant.-our sun went supernova it entertained the idea of having an ark type ship built and a lottery to pick people to go on it. It had its own plant life to produce oxygen and a recycled water supply and I can't remember the power supply (anyone else who might have seen it feel free to add) the ship eventually finds a planet like ours but by this time the people onboard are 3rd generation and have actually never lived on earth.It was interesting because there's all this stuff out there now about saving the planet and investing in what we have. But an impact is a very real threat and I'd plan A is to deflect it we should also have a plan B.. let's get outa here.;-)

littlemac1980

Daffodil.d wrote: »

Everytime those documentaries are on tv highlighting what would happen if we had an impact I always feel like the whole thing has been unfinished but I recently saw one on discovey that went into the future and imagined what life would be like after an impact. This particular one wasn't about an impact per say but is still relevant.-our sun went supernova it entertained the idea of having an ark type ship built and a lottery to pick people to go on it. It had its own plant life to produce oxygen and a recycled water supply and I can't remember the power supply (anyone else who might have seen it feel free to add) the ship eventually finds a planet like ours but by this time the people onboard are 3rd generation and have actually never lived on earth.It was interesting because there's all this stuff out there now about saving the planet and investing in what we have. But an impact is a very real threat and I'd plan A is to deflect it we should also have a plan B.. let's get outa here.;-)

Of course the most robust solution would be an extra terrestrial colony - perhaps on Mars or in the upper atmosphere of Venus.

Daffodil.d

littlemac1980 wrote: »

Of course the most robust solution would be an extra terrestrial colony - perhaps on Mars or in the upper atmosphere of Venus.

Maybe Mars at a push if you could pick the right place and in'vent a protective hub against -90 deg. But Venus would be impossible. It's upper atmosphere is made up of sulfuric acid and it's temp is over 400 deg- there's a range of things. I can't remember how they powered the ark/ship and it's bugging me now!

littlemac1980

Daffodil.d wrote: »

Maybe Mars at a push if you could pick the right place and in'vent a protective hub against -90 deg. But Venus would be impossible. It's upper atmosphere is made up of sulfuric acid and it's temp is over 400 deg- there's a range of things. I can't remember how they powered the ark/ship and it's bugging me now!

Lots of Sulphuric Acid alright, but the temp seems OK according to this guy:

http://www.universetoday.com/15570/colonizing-venus-with-floating-cities/

It's still a well out there idea, interesting concept though.

Capt'n Midnight

Meanwhile

http://www.theregister.co.uk/2013/02/26/india_launch_canada_microsatellites/

With India’s successful PSLV (Polar Satellite Launch Vehicle) lift-off on February 26, Canada is now boasting the deployment of the world’s first dedicated asteroid-hunting satellite.

Actually, its NEOSSat – Near-Earth Object Surveillance satellite – microsatellite will also be surveying space junk from its 100-minute, 800 km altitude orbit. As well as contributing to Canada’s High Earth Orbit Surveillance System, the satellite will take images in the direction of the sun to try and identify asteroids.

ps200306

Most of that stuff you see about diverting asteroids is likely to remain in the realms of sci-fi. There's a couple that can be ruled out right off the bat. You can't divert an asteroid by reflecting light onto with a mirror. The mirror itself would experience twice the acceleration of the asteroid (assuming 100% absortion by the asteroid). So now you need engines to keep the mirror in place. Well why not just strap them onto the asteroid? Solar sails could work in theory, but how to you anchor them to a rotating asteroid? Anyway, the acceleration produced by reflected light off any realistic area is tiny, so all of this presupposes decades of warning.

With less warning, the numbers just don't stack up. Suppose we discover a 1 km asteroid on a collision course with earth, with two years warning. The trajectory uncertainty is such that we need to move it 50,000 kilometres to ensure that it misses earth within an acceptable margin of error. It's a metallic asteroid, so it weighs two billion tonnes. Two years to shift a two billion tonne object by 50,000 km ... that's a continuously applied force of over 200 mega-Newtons, even assuming you have some way of appying the force effectively to a rotating body. And that's about seven times the peak thrust of the space shuttle's engines. Think about the launch weight of the space shuttle, and the fact that it burns through its giant external tank of fuel (not to mention the SRBs) in what, 8 minutes or so? Now imagine it has to stay at full throttle, day after day for two years. And you need seven of them. The problem is not just the mind-boggling amount of fuel, but the fuel you need to get the fuel to the asteroid (the so-called exponential delta-v problem). You're talking about a fuel tank that's the size of a minor planet in its own right. It's just not feasible.

Capt'n Midnight

ps200306 wrote: »

With less warning, the numbers just don't stack up. Suppose we discover a 1 km asteroid on a collision course with earth, with two years warning. The trajectory uncertainty is such that we need to move it 50,000 kilometres to ensure that it misses earth within an acceptable margin of error. It's a metallic asteroid, so it weighs two billion tonnes. Two years to shift a two billion tonne object by 50,000 km ... that's a continuously applied force of over 200 mega-Newtons,

How did you calculate the movement ?

Assume a constant acceleration to travel 50,000Km in 2 years.

The acceleration needed d=ut + 0.5 at^2

a = 50*10^6 m / ( 0.5 * (2*365.25*24*3600 s)^2 )
a = 25 *10^-9 m/s2

now for 2 billion tonnes
F=ma , 50,206 Newtons ( ~ 5 Tonnes of thrust )

E&OE


What's the moment of intertia of such an asteroid ?
it might be possible to reduce the rotation so it's only spinning on one axis

Zubeneschamali

Capt'n Midnight wrote: »

it might be possible to reduce the rotation so it's only spinning on one axis

Pardon me?

ps200306

Capt'n Midnight wrote: »

How did you calculate the movement ?

Yeraaaa .... what's three or four orders of magnitude between friends.

You're right. WE'RE SAVED!!!

Capt'n Midnight wrote: »

What's the moment of intertia of such an asteroid ?

Only the very largest are big enough to be spherical, so there is no easy way to calculate a moment of inertia, given we have no idea of shape (and even if we did we still couldn't easily do it).

Capt'n Midnight wrote: »

it might be possible to reduce the rotation so it's only spinning on one axis

As long as a body is rigid it can only spin on one axis. That still doesn't give us an easy way to apply a force whose line of action has a constant orientation.

ps200306

Thinking about this further, even if you had a source of motive power, applying a force in the right direction would be a real problem with a spinning asteroid. Maybe the mirror idea has more merit than I thought, even if you do need engines strapped to your mirrors!

Although, for the 50 kN force we were talking about above, you'd need a square mirror that was a hundred kilometres on a side. And that ignores that on an irregularly shaped asteroid, you still don't get straight line motion. And if your giant mirror starts vaporising the asteroid surface, you start accelerating vapour in random directions instead of asteroid away from earth.

Maybe we're screwed again.

Capt'n Midnight

Zubeneschamali wrote: »

Pardon me?

The asteroid is spinning on an axis, but that axis may wobble, a lot

so if you can nudge it so the axis doesn't wobble and it's north / south pole are lined up with the direction you want to pull/push then the spinning isn't a biggie



It all depends on time available



Hmmm... you could make a space elevator on a spinning asteroid

it would have to be long enough so that the far tip was at more than escape velocity so stuff would be flung away into space, this would via a belt pull up the next stuff to be discarded. timing when you released the stuff would change the velocity

tricky maths but you are using spinning inertial to generate thrust




If the asteroid is heading to earth, then changing it's direction by random amounts can't make things worse. n random walk moves you from the centre by by an average of sqrt(n) and we have the advantage that we can pull the plug once we like the randomness

ps200306

Capt'n Midnight wrote: »

The asteroid is spinning on an axis, but that axis may wobble, a lot

so if you can nudge it so the axis doesn't wobble and it's north / south pole are lined up with the direction you want to pull/push then the spinning isn't a biggie

I like your optimism ... but it's not that simple. I'm not sure where you're getting this idea of a wobble from. A perfectly rigid body rotating freely doesn't wobble. Maybe you are getting confused by the earth's wobble ... that's caused by the gravity of the moon on the equatorial bulge. The only way an asteroid can wobble is by flexure. If it is irregularly shaped, and not spinning around its axis of maximum rotational inertia, there are stresses inside it that can cause a wobble. (We've got one on earth -- the Chandler wobble -- but it only offsets the spin axis at the pole by something less than 10 metres I think). Unfortunately for your idea, you can't just straighten out this wobble -- it would be like flinging a water balloon into the air and hoping to flatten out the ripples in its surface. It happens spontaneously over a (very long) period of time by radiating away angular momentum. But I think the magnitude of the wobble is likely to be very tiny, unless the asteroid is truly loosely bound (i.e. the rubble heap model) in which case you have bigger problems moving it than the wobble.

As for changing the direction of the primary spin axis, it sounds like a big job. Considering that in our previous thought experiment, our 50 kN force only produced a linear velocity of 1.6 m/s after 2 years, intuitively it seems to me that changing the spin axis of a body with a decent rotation rate by a large angle could be a comparable task. (Would depend on rotation rate obviously).

Capt'n Midnight wrote: »

Hmmm... you could make a space elevator on a spinning asteroid

it would have to be long enough so that the far tip was at more than escape velocity so stuff would be flung away into space, this would via a belt pull up the next stuff to be discarded. timing when you released the stuff would change the velocity

tricky maths but you are using spinning inertial to generate thrust

Something smells very fishy about that idea. How does releasing your stuff cause anything other than the reciprocal reaction to that caused when you yanked it up in the first place? Really the best you can do is use the motive power of your elevator, employing chunks of asteroid as reaction mass. In that case a much simpler arrangement would be to just catapult stuff off the surface in the desired direction. But the energy ultimately comes from your elevator/catapult and needs fuel.

Capt'n Midnight wrote: »

If the asteroid is heading to earth, then changing it's direction by random amounts can't make things worse. n random walk moves you from the centre by by an average of sqrt(n) and we have the advantage that we can pull the plug once we like the randomness

That's quite a gamble! Heads, we're saved, tails the earth goes down in a giant ball of flame

Capt'n Midnight

ps200306 wrote: »

I like your optimism ... but it's not that simple. I'm not sure where you're getting this idea of a wobble from. A perfectly rigid body rotating freely doesn't wobble.

next time you are playing with a gryoscope try spinning it - a bicycle wheel held by the axel is one way, it keeps rotating that way. wobble was just shorthand

That's quite a gamble! Heads, we're saved, tails the earth goes down in a giant ball of flame

it's not a gamble

we'd only do it if the asteroid was on a collison course already
and we can stop tossing the coin when we get a result we like

It's not like betting your life's savings on Red
It's more like you are strapped to a time bomb that has a lot of buttons, some of the buttons pause the countdown, some allow it to continue

ps200306

Capt'n Midnight wrote: »

next time you are playing with a gryoscope try spinning it - a bicycle wheel held by the axel is one way, it keeps rotating that way. wobble was just shorthand

Don't know what you're saying here ... a gyroscope or a bicycle wheel doesn't wobble in the absence of a force.