Asteroid Impact/Capture/Encounter??????

[Big_Spark]

Please read this piece of Astro News before reading my question below it.

Last month was significant for the asteroid formerly known as 2004 MN4. On July 19, it lost its provisional designation and acquired its permanent number and name. The number, 99942, is the largest yet assigned to an asteroid. The name, which will delight Egyptologists and science-fiction fans alike, is Apophis.

Between July 9 and 11, astronomers Dave Tholen, Fabrizio Bernardi, and Roy Tucket took what are likely the last optical images of the asteroid before 2007. They used the 90-inch Bok Telescope at Kitt Peak National Observatory in Arizona. The same team discovered the asteroid last June.

On April 13, 2029, Apophis will pass 22,600 miles (36,350 kilometers) from Earth — so close it skirts the belt of orbiting geosynchronous satellites and will be visible to the unaided eye as a moving, magnitude 3.3, starlike point. Astronomers estimate the space rock is 1,050 feet (320 meters) across and has a striking power equivalent 850 million tons of TNT, or more than 4 times the energy released when the Indonesian volcano Krakatoa erupted in 1883.



Asteroid Apophis will pass near Earth in 2029. E. De Jong, S. Suzuki / JPL / NASA
At about the same time Tholen's team took its latest Apophis images, the Jet Propulsion Laboratory's Near Earth Object (NEO) Program Office incorporated new observational data into its calculation of the asteroid's impact risk.

The new data slightly raise the odds of an impact in the 2030s to roughly 1 in 8,000. The most probable impact scenario occurs in 2036, off the Pacific coast of North America, and carries the potential of generating a 30-foot-high tsunami that could strike southern California.

Still, while Apophis probably won't strike Earth in the foreseeable future, the asteroid will not be the same after its close encounter with our planet in 2029. Earth's gravity and the tidal forces exerted on Apophis will change it in several ways — a cosmic makeover.

First, the asteroid's orbit will be significantly altered. As things currently stand, Apophis belongs to the Aten group of asteroids, which circle the Sun inside Earth's orbit. After April 13, 2029, the rock's orbit will have changed enough to place it in the Apollo class — asteroids that actually cross Earth's orbit.

Second, the encounter with Earth will significantly alter the object's rotation rate. Recent calculations by a team led by Daniel Scheeres of the University of Michigan indicate that tides raised in Apophis by Earth's gravity could result in a lengthening of the asteroid's present 30-hour "day" by as much as 27 hours; a speed-up is also possible. The 2029 encounter will provide astronomers with their first chance to watch the disruption of an asteroid's spin state.

According to Scheeres and others, such as Dan Durda of the Southwest Research Institute, the tidal forces will strain the asteroid, causing "localized shifts" — asteroid quakes — on its surface and within its interior. If the asteroid has a lower density — less than half that of water — than astronomers now think, Apophis could be either reshaped or completely disrupted.

Apophis is the Greek name given to the Egyptian demon Apep, who was the enemy of light and order, the personification of evil and chaos. Depicted as a giant snake, Apophis/Apep attacked the Sun god Ra as he made his way through the Egyptian underworld during the evening hours. Solar eclipses were thought to be Apep's few daytime attempts to swallow Ra, who always succeeded in cutting his way out of the snake's belly. As the enemy of Ma'at, the ancient Egyptian concept of order and law, Apep represented chaos.

However, it's likely mythology wasn't the only consideration in naming Apophis. Codiscoverer Dave Tholen is known to be a fan of the TV series Stargate SG-1. The show's most persistent villain is Apophis, an alien also named for the Egyptian god.

Whether inspired by mythology or science fiction, the name seems appropriate for an object that continues to change the way astronomers think about asteroids and planetary protection.

Origin article can be found Here

Now my question is this, Who thinks it would be a good idea to look at the feasibility of using human technology, such as chemical rockets, to alter this asteroids orbit so that instead of missing Earth, it actually enters Earth Orbit about 36,000 miles above the surface in a Geostationary orbit?

This would then be in an excellent position for the actual study of an Asteroid in space, something we don't have the luxury of yet, but also it could be used as a Space Station. Then we could use it as a test bed for mining operations in space at the same time.

If such a plan was considered too dangerous, what about the alteration of it's orbit to cause a Lunar Impact that we could then study?

 

[AdamW]

it actually enters Earth Orbit about 36,000 miles above the surface in a Geostationary orbit?

I am wondering how you intend to have a stable geostationary orbit at 36,000 miles above the surface...

It is a nice idea, and it would be very exciting to have a near-earth object to observe all the time. In fact, I think it would be freakin' sweet and would LOVE to have a new moon.

There are a few potential problems:

1) If the asteroid passes the earth at an angle to the equatorial plane, then at geostationary distance it's orbit will cross that of artificial satellites, possibly knocking out Sky and depriving me of my satellite telly. This could be overcome with the rockets you speak of for manoeuvring the asteroid.

2) We don't know what direction it will pass the earth... it could be retrograde, therefore even more likely to neutralise my satellite TV.

3) The asteroid will be passing the earth at a "somewhat nippy" speed. According to a link of the link, it will be moving at 2.5 degrees per minute. I have no paper to hand so can't do a proper calculation, but a quick calculation shows that in the best case you you would have to shave about 105,000 kph off the speed of the asteroid to get it into a stable geostationary orbit.

HOWEVER, I can see an adaptation of your idea that would be easier to accomplish: push it into an orbit further out. If you used your chemical rockets to push it away from the earth's centre, then it could enter an orbit at, say, 150,000 km instead of 36,000 km. It would move slowly across the sky, but it would require far less energy to accomplish. It would also be less likely to encounter any communications satellites, regardless of direction.

 

[Freddie]

I think some people have far too much time on their hands. And why would you want to observe a lump of metal/rock/ice in space? i suppose it beats Eastenders

In the 1950's and early 1960's some so called clever people actually believed we would have nucleur powered aeroplanes

 

[Big_Spark]

Adam, to address some of your points.

Firstly, any orbit that is around 36,000 miles above the surface is likely to be geostationary, this simply means it orbits the Earth in 23hrs 56mins and 4.43 seconds, the actual time the planet takes to rotate. As a result the orbiting object would remain above the same point in the sky as long as it's orbit does not change. This is very easy to do.

Regarding artificial satellites, the vast majority orbit earth at LESS than 1000 miles, the majority at about 250 miles. There are numerus reasons for that, but the two prime ones being cost of launch and also after death the satellite will burn up in the atmosphere after a given period.

Regarding the direction of travel, this is known, if we did not know this, then the orbital parameters would be unknown and the date given and distance for close approach would be incalculable.

Regarding the speed, this is the critical issue. The orbital speed of Aten class bodies is around 37kp/s-¹ (22mp/s-¹), this translates to 133200 kp/h-¹ (79200mp/h-¹). In order for Earth to capture the asteroid and for it to fall into a stable orbit, then some very careful calculations would need to be done, howver this can be done slowly over many years. As the object passes close the earth each orbit, a small change in velocity would be enough to slow it down over longer periods, as they do with spacecraft. Further, we could also swing the asteroid by Venus or even The Moon to use their gravity to give us a freebie orbital and thus velocity change, again this is a well known prcedure.

There would be extreme technical challenges to overcome, however this could be the first of several natural, yet artificially placed moons that Earth could have, each one being formed into a habitat for communities of scientists and miners.

++++++++++++++++++++++++++++++++++++

I think some people have far too much time on their hands. And why would you want to observe a lump of metal/rock/ice in space? i suppose it beats Eastenders

In the 1950's and early 1960's some so called clever people actually believed we would have nucleur powered aeroplanes

Each to their own Freddie. Nuclear powered aircraft are possible and technically easy to build today, but their practicality is a whole other issue. I for one would oppose them!!

 

[Freddie]

Which was my point Fwl, we all know they could fly but also go wrong and god knows what would happen just like your metorite/astoroid/comet/lump of rock/whatever

 

[AdamW]

Adam, to address some of your points.

Firstly, any orbit that is around 36,000 miles above the surface is likely to be geostationary, this simply means it orbits the Earth in 23hrs 56mins and 4.43 seconds, the actual time the planet takes to rotate. As a result the orbiting object would remain above the same point in the sky as long as it's orbit does not change. This is very easy to do.

I was splitting hairs on this one , a geostationary orbit exists at 36,000 kilometres above the equator

Regarding the direction of travel, this is known, if we did not know this, then the orbital parameters would be unknown and the date given and distance for close approach would be incalculable.

Imagine you are looking down on the earth from the north pole... if the asteroid swings past to the left of the earth, from the outer solar system towards the sun, then it will enter an anticlockwise orbit.

Then imagine it swings past to the right of the earth... this would result in a clockwise "retrograde" orbit. Which would mean it was orbiting at the same distance as all the comms satellites, but in the opposite direction: a closing speed of about 23,000 kph. Bang! No more Men&Motors for me.

Unless I missed it, they didn't say which way the asteroid was passing the Earth. So, it is 50:50 as to whether or not it would be passing on the right side to perform such a delecate manoeuvre.

You are totally right about careful calculations though, and using other bodies to slow it down could result in less energy being required to get it into the right orbit.

However, I reckon that unless an asteroid is actually going to hit the earth (and this can be proved), they would rather leave it alone. Could you imagine being the one having to explain to the world "Sorry guys, I forgot to carry the one, it's gonna hit!!!"

 

[Big_Spark]

Adam, simple mistype by me that I did not pick up on, you are 100% correct that it should be 36K KM not MILES as I posted...Tired and beer don't mix I think

Regarding the direction, it is PROGRADE, as in it orbits the Sun in the same direction as Earth, this is why the low approach velocity.

With very few exceptions, all of the several hundred known NEO's are in prograde orbits. Were this not the case then the article would say the motion was -2.5 degress as oppose to +2.5 degrees of motion across the sky.

Further, your description of the right and left hold no meaning space, if I may be so pedantic, that is why the terms prograde and retrograde are used.

Prograde orbits are those which follow convention. All of the Major bodies of the Solar system orbit in the same direction, that is prograde. Seen from above the system this is anti-clockwise. Many asteroids and about 50% of comets orbit the Sun in a retrograde manner, which is opposite the convention, thus seen from above the system their orbits are clockwise.

Such phenomena also exist with planetary satellites and even planetary rotations.

 

[Zampa]

Please read this piece of Astro News before reading my question below it.

Last month was significant for the asteroid formerly known as 2004 MN4. On July 19, it lost its provisional designation and acquired its permanent number and name. The number, 99942, is the largest yet assigned to an asteroid. The name, which will delight Egyptologists and science-fiction fans alike, is Apophis.

Between July 9 and 11, astronomers Dave Tholen, Fabrizio Bernardi, and Roy Tucket took what are likely the last optical images of the asteroid before 2007. They used the 90-inch Bok Telescope at Kitt Peak National Observatory in Arizona. The same team discovered the asteroid last June.

On April 13, 2029, Apophis will pass 22,600 miles (36,350 kilometers) from Earth — so close it skirts the belt of orbiting geosynchronous satellites and will be visible to the unaided eye as a moving, magnitude 3.3, starlike point. Astronomers estimate the space rock is 1,050 feet (320 meters) across and has a striking power equivalent 850 million tons of TNT, or more than 4 times the energy released when the Indonesian volcano Krakatoa erupted in 1883.



Asteroid Apophis will pass near Earth in 2029. E. De Jong, S. Suzuki / JPL / NASA
At about the same time Tholen's team took its latest Apophis images, the Jet Propulsion Laboratory's Near Earth Object (NEO) Program Office incorporated new observational data into its calculation of the asteroid's impact risk.

The new data slightly raise the odds of an impact in the 2030s to roughly 1 in 8,000. The most probable impact scenario occurs in 2036, off the Pacific coast of North America, and carries the potential of generating a 30-foot-high tsunami that could strike southern California.

Still, while Apophis probably won't strike Earth in the foreseeable future, the asteroid will not be the same after its close encounter with our planet in 2029. Earth's gravity and the tidal forces exerted on Apophis will change it in several ways — a cosmic makeover.

First, the asteroid's orbit will be significantly altered. As things currently stand, Apophis belongs to the Aten group of asteroids, which circle the Sun inside Earth's orbit. After April 13, 2029, the rock's orbit will have changed enough to place it in the Apollo class — asteroids that actually cross Earth's orbit.

Second, the encounter with Earth will significantly alter the object's rotation rate. Recent calculations by a team led by Daniel Scheeres of the University of Michigan indicate that tides raised in Apophis by Earth's gravity could result in a lengthening of the asteroid's present 30-hour "day" by as much as 27 hours; a speed-up is also possible. The 2029 encounter will provide astronomers with their first chance to watch the disruption of an asteroid's spin state.

According to Scheeres and others, such as Dan Durda of the Southwest Research Institute, the tidal forces will strain the asteroid, causing "localized shifts" — asteroid quakes — on its surface and within its interior. If the asteroid has a lower density — less than half that of water — than astronomers now think, Apophis could be either reshaped or completely disrupted.

Apophis is the Greek name given to the Egyptian demon Apep, who was the enemy of light and order, the personification of evil and chaos. Depicted as a giant snake, Apophis/Apep attacked the Sun god Ra as he made his way through the Egyptian underworld during the evening hours. Solar eclipses were thought to be Apep's few daytime attempts to swallow Ra, who always succeeded in cutting his way out of the snake's belly. As the enemy of Ma'at, the ancient Egyptian concept of order and law, Apep represented chaos.

However, it's likely mythology wasn't the only consideration in naming Apophis. Codiscoverer Dave Tholen is known to be a fan of the TV series Stargate SG-1. The show's most persistent villain is Apophis, an alien also named for the Egyptian god.

Whether inspired by mythology or science fiction, the name seems appropriate for an object that continues to change the way astronomers think about asteroids and planetary protection.

Origin article can be found Here

Now my question is this, Who thinks it would be a good idea to look at the feasibility of using human technology, such as chemical rockets, to alter this asteroids orbit so that instead of missing Earth, it actually enters Earth Orbit about 36,000 miles above the surface in a Geostationary orbit?

This would then be in an excellent position for the actual study of an Asteroid in space, something we don't have the luxury of yet, but also it could be used as a Space Station. Then we could use it as a test bed for mining operations in space at the same time.

If such a plan was considered too dangerous, what about the alteration of it's orbit to cause a Lunar Impact that we could then study?

I think it will be yet another total waste of money....so what??...and who cares....theres millions of people dying every day from alsorts....and we are walking around with our heads skywards???

Bit like the appollo landings...and journeys to mars......

They have absolutly no significance whatsoever

Complete waste of resources and money IMO

 

[Big_Spark]

Zampa, in one way I sort of agree with you, but in many ways I do not.

Firstly, we have been very lucky as a species, the last 20,000 years has been geologically quiet and there are several types of asteroid impact that are overdue.

The last "major" impact was 9500 years ago in what is today Northern Chad, this impact is why North Africa is a desert. It left a crater 20.5km across, after the rim collapsed, and some 1.8km deep. Everything within about 700km would have been vapourised within a few short seconds.

This sort of impact normally occurs with an average interval of some 4000 years, there should have been at least one such impact since, yet there hasn't been, it is overdue. Further, there should be smaller impacts on a regular basis, about every 800 to 1000 years there should be impacts of objects up to 300m across, there haven't been any in 6700 years.

It is not that the rocks are not out there, they are, we have simply been fortunate in that encounters have been with smaller objects in the last few thousand years, but this cannot and will not continue.

The problem we have is that we still know little about the maeup of most asteroids, yes we know the materials they are made from in most cases, but we do not know if they are solid or simply piles of rubble held together by gravity. This may sound insignificant, but it is extremely important to the mechanics of an impact, further, if Apophis is actually a rubble pile, then the encounter of 2029 is very likely to pull it to pieces, as Jupiter did Comet P/ Shoemaker-Levy 9. This will change the orbital mechanics of the pieces forming Apophis, and it is impossible to calculate what effect this will have. Some fragments may be ejected into safe orbits, some may be thrown into an Earth orbit, eventually impacting the Earth or the Moon, others may well be pulled into the atmosphere directly.

Yes many will likely burn up, but depending on the pieces and their actual make-up, some may well impact the ground, and it could be a small swarm of them.

It would only take a piece of Apophis about 1000 tonnes to hit a major metropolitan area to kill hindreds of thousands or even millions depending where it hit. The Impact would release the energy of a small Nuclear Warhead similar in size to Hiroshima or Nagasaki.

We need to understand the rocks in the space around us, and to do that we need to get close to them, I cannot think of a better way than placing one or more into Earth Orbit.

 

[Zampa]

Oh yes I agree there...when we are talking about the survival of our planet...

But some of the money spent just seems to me is purely becasue we want to find whats there..

I see it as recreational money....bit like buying fags an booze when the kids need clothes and decent food.

An impact is a terrifying thought....and the possiblities of averting it most be looked into...

But jollies to the moon and mars....nah.

 

[ban-all-sheds]

Regarding artificial satellites, the vast majority orbit earth at LESS than 1000 miles, the majority at about 250 miles.

I don't know what proportions of the entire collection of artificial satellites are in geosynchronous, medium altitude, sun synchronous polar or low altitude orbits, but Adam was talking about the asteroid colliding with a Sky TV satellite, and they are all geosynchronous...

 

[AdamW]

Adam, simple mistype by me that I did not pick up on, you are 100% correct that it should be 36K KM not MILES as I posted...Tired and beer don't mix I think

Couldn't help it, my pedant hat was on!

Regarding the direction, it is PROGRADE, as in it orbits the Sun in the same direction as Earth, this is why the low approach velocity.

With very few exceptions, all of the several hundred known NEO's are in prograde orbits. Were this not the case then the article would say the motion was -2.5 degress as oppose to +2.5 degrees of motion across the sky.

Further, your description of the right and left hold no meaning space, if I may be so pedantic, that is why the terms prograde and retrograde are used.

Yes, the way I phrased it was ambiguous, I got so far as saying "looking down on the North pole" but didn't actually describe any other directions.

What I was saying is that the asteroid may well be orbiting the sun in a prograde fashion, same as us, but that does not mean it would be captured into a prograde orbit around the Earth.

Now, as you can see in the following, the red asteroid and the black asteroid are both orbiting the sun prograde. However the black asteroid would be captured in a retrograde orbit around the earth.

They don't actually quote the direction of the asteroid's motion, only the magnitude (2.5 degrees/minute)... astronomical convention dictates that if they mean +2.5 degrees, they will say +2.5 degrees... perhaps they are just being sloppy (I have seen positive magnitudes written without a plus sign)? After all, if they can state with some certainty the miss distance, then they should also know which side it will pass on... either way, pretty impressive that they can calculate to such accuracy!

How much thrust do we need to move it? Well they reckon it is about 400m across. Let's assume it is not spherical but instead has half the volume of a sphere 400m across (so it's very knobbly and relatively light for its size)...

Volume = (4/3 * pi * r^3)/2
= 16.8 million cubic metres

Let's assume it has the density of the moon, 3300kg/m^3:

Mass = 3300 * 16.8*10^6
= 5.5 *10^10 kg

Now, the minimum momentum change required would be to slow it by 105,000kph, or 29,000 metres per second.

mv = 2.9*10^4 * 5.5 *10^10
= 1.6*10^15 kg.m/s

Now, a Shuttle solid rocket booster produces 14.7MN of thrust, for around 126 seconds. That is a total impulse of 1.9*10^9 kg.m/s

So, in all you would need to burn the equivalent of... 842,000 Shuttle SRBs... That's a lot of rocket fuel!

 

[Zampa]

Adam, simple mistype by me that I did not pick up on, you are 100% correct that it should be 36K KM not MILES as I posted...Tired and beer don't mix I think

Couldn't help it, my pedant hat was on!

Regarding the direction, it is PROGRADE, as in it orbits the Sun in the same direction as Earth, this is why the low approach velocity.

With very few exceptions, all of the several hundred known NEO's are in prograde orbits. Were this not the case then the article would say the motion was -2.5 degress as oppose to +2.5 degrees of motion across the sky.

Further, your description of the right and left hold no meaning space, if I may be so pedantic, that is why the terms prograde and retrograde are used.

Yes, the way I phrased it was ambiguous, I got so far as saying "looking down on the North pole" but didn't actually describe any other directions.

What I was saying is that the asteroid may well be orbiting the sun in a prograde fashion, same as us, but that does not mean it would be captured into a prograde orbit around the Earth.

Now, as you can see in the following, the red asteroid and the black asteroid are both orbiting the sun prograde. However the black asteroid would be captured in a retrograde orbit around the earth.

They don't actually quote the direction of the asteroid's motion, only the magnitude (2.5 degrees/minute)... astronomical convention dictates that if they mean +2.5 degrees, they will say +2.5 degrees... perhaps they are just being sloppy (I have seen positive magnitudes written without a plus sign)? After all, if they can state with some certainty the miss distance, then they should also know which side it will pass on... either way, pretty impressive that they can calculate to such accuracy!

How much thrust do we need to move it? Well they reckon it is about 400m across. Let's assume it is not spherical but instead has half the volume of a sphere 400m across (so it's very knobbly and relatively light for its size)...

Volume = (4/3 * pi * r^3)/2
= 16.8 million cubic metres

Let's assume it has the density of the moon, 3300kg/m^3:

Mass = 3300 * 16.8*10^6
= 5.5 *10^10 kg

Now, the minimum momentum change required would be to slow it by 105,000kph, or 29,000 metres per second.

mv = 2.9*10^4 * 5.5 *10^10
= 1.6*10^15 kg.m/s

Now, a Shuttle solid rocket booster produces 14.7MN of thrust, for around 126 seconds. That is a total impulse of 1.9*10^9 kg.m/s

So, in all you would need to burn the equivalent of... 842,000 Shuttle SRBs... That's a lot of rocket fuel!

Great grpahic...makes it all o so much clearer.. ...whats the fried egg in the middle though?

 

[Big_Spark]

Adam, great Maths mate, but there are a couple of flaws in it. Firstly, most NEO's have an average density of around 2.8g/cm-³, however the greatest flaw is the in the momentum calculations.

Firstly, actually slowing a body down in the solar system is far easier than you might think, as the Sun's and Earth's gravity will work for you to rob angular momentum from the object, and if the orbital calculations are done precisely enough, then you can get Earth to slow the Apophis's orbital velocity by over 90% alone.

All that is required is boosters to control the rotation of the object, to prevent chaotic tumbling, this is relatively easy to do, secondly, once this has been achieved, small boosters could rob a few km/s-¹ off the momentum, this would alter the objects orbit. If you corrected it's path correctly, then you could get the asteroid to make a few close passes of venus and the Moon between now and 2029. Each of these would then modify the orbit and change it's angular momentum.

Once this was achieved, one more final pass by the lunar surface, so long as it was outside the Lunar Roche Limit, would reduce the orbit to a level weher the Earth could easily capture it.

This may sound difficult, and it is, but we have become experts on doing this with countless satellites and probes, the technique is well understood, and computer programs have been used with the information gleaned, to understand asteroid capture and disintigration by planets.

The whole project could probably be achieved with the equivelent of about 20 shuttle launches.

The real questions are whether we have the will, and whether we have the balls to try, considering the potential consequences if it goes teats up..

 

[Freddie]

Blar blar blar----so whats the point spend billions just so you can watch a lump of rock in space Why not just stick a few cameras on one and you have the same effect

Blo ody stupid idea if you ask me