Asteroid defense ideas

[Ken Fabian]

On 5/29/2024 at 10:19 AM, Moontanman said:

As long as we don't get a large asteroid approaching from the direction of the sun... 

We are fine only because it hasn't happened... yet

Seems to me that would give us more time, not less. And I expect it has happened - and equally likely to reach us that way as inbound.

Large objects should be identifiable from any direction and well before any passage around the sun - and identifying and tracking should be (and is) the space agency priority. And (not sure) but may be potential for gravity sling and more effective deflection with less energy can be done when it is closest to the sun?

5 hours ago, Airbrush said:

It doesn't get blown up.  There is only an intense, very short, pulse of HEAT, no shock wave in space, that should melt any rocks or ice and they would immediately freeze again but fused together, and it gets a push from outgassing.

The Nuclear Devices for Planetary Defense link does suggest potential for explosive dispersal and also that a late response might have little choice but to rely on that.

 

6 hours ago, zapatos said:

Coalesce due to gravity is a bad thing if the thing you just blew up coalesces into a single object prior to impact with earth.

I can't see that as likely; the gravity of such objects - even the large ones - is small. Even if it doesn't disperse most of the debris that isn't dispersed will end up orbiting, not coalescing.

[zapatos]

28 minutes ago, Ken Fabian said:

I can't see that as likely; the gravity of such objects - even the large ones - is small. Even if it doesn't disperse most of the debris that isn't dispersed will end up orbiting, not coalescing.

 

Quote

Several ways of avoiding an asteroid impact have been described.^[8] Nonetheless, in March 2019, scientists reported that asteroids may be much more difficult to destroy than thought earlier.^[9][10] In addition, an asteroid may reassemble itself due to gravity after being disrupted.^[

https://en.wikipedia.org/wiki/Asteroid_impact_avoidance#:~:text=In addition%2C an asteroid may,to gravity after being disrupted.

[dimreepr]

16 hours ago, Airbrush said:

If you learned that an asteroid that will destroy a city, or a country, or life as we know it, would you not care?

I was going to say "it depends on whether we see it in time" but it really doesn't; why do I need to know?

If we see it in time and can convince enough people of influence then perhaps 'we' can glory in 'our' victory; I haven't even got a backyard telescope, in order to be the plucky hero that tries to alert the authorities but is, either, snared by the red tape or dies trying. 

All I can do is vote angrily, when the fuckwits have screwed up our only chance... 😉

[Moontanman]

14 hours ago, Ken Fabian said:

Seems to me that would give us more time, not less. And I expect it has happened - and equally likely to reach us that way as inbound.

I provided a link that explains why we can't see asteroids coming in from the glare of the sun.  

[Ken Fabian]

@zapatos If detonations can't give loose rubble enough impetus to escape it's own gravity that would be a mission gone wrong. Avoiding missions going wrong would be important.

I'm thinking of what happens with inadequate dispersal, with rocks moving about within a weak gravity well - I would expect any bits coming back in towards the centre of gravity will bounce off each other, not coalesce, some gaining enough momentum to escape in the process, some losing it and orbiting closer. I expect it would take a long time to settle and I think any persistent configuration is more likely to end up as 2 or more smaller rubble piles orbiting each other,  possibly after a long time as a larger one with a ring before that. Significant solid portions within what we think (wrongly) is loose rubble might be very problematic.

Detonations intended to disperse will be external, on one side, with shock waves within the asteroid as well as rocks outgassing and a range of directions for pieces dispersed, with variable speeds. That would not be like an inadequate detonation placed at the core where the material goes out and a most comes back the same direction. Which I think would make a cloud of loose material that, again, would "coalesce" as a ring with enough time.

 

4 hours ago, Moontanman said:

I provided a link that explains why we can't see asteroids coming in from the glare of the sun.  

Yes, sorry, I missed a few posts along the way and was thinking of asteroids from further out. The asteroids that orbit near, inside and just outside Earth's orbit do present challenges for detection but I wouldn't think those are insurmountable. The challenges for any deflection might turn out to be less for such asteroids as long as we have the early detection due to lower delta-v requirements to reach them.

Detection will need to move beyond Earth based observatories to get as complete a database as possible - and improving detection is surely the immediate priority.

[Moontanman]

33 minutes ago, Ken Fabian said:

@zapatos If detonations can't give loose rubble enough impetus to escape it's own gravity that would be a mission gone wrong. Avoiding missions going wrong would be important.

I'm thinking of what happens with inadequate dispersal, with rocks moving about within a weak gravity well - I would expect any bits coming back in towards the centre of gravity will bounce off each other, not coalesce, some gaining enough momentum to escape in the process, some losing it and orbiting closer. I expect it would take a long time to settle and I think any persistent configuration is more likely to end up as 2 or more smaller rubble piles orbiting each other,  possibly after a long time as a larger one with a ring before that. Significant solid portions within what we think (wrongly) is loose rubble might be very problematic.

Detonations intended to disperse will be external, on one side, with shock waves within the asteroid as well as rocks outgassing and a range of directions for pieces dispersed, with variable speeds. That would not be like an inadequate detonation placed at the core where the material goes out and a most comes back the same direction. Which I think would make a cloud of loose material that, again, would "coalesce" as a ring with enough time.

It's interesting that there exists an asteroid with a ring,I wonder if a strike from a solid asteroid on a rubble pile asteroid gives some validity to to your idea? 

[zapatos]

10 hours ago, Ken Fabian said:

If detonations can't give loose rubble enough impetus to escape it's own gravity that would be a mission gone wrong. Avoiding missions going wrong would be important.

We're all aware that avoiding missions going wrong would be important but the fact remains that missions in space have on occasion not performed as expected. Thus identifying and mitigating risk is important. As far as I can tell, reassembly still remains a risk depending on the type of mission.

One way to mitigate the risk of dispersal of debris with nuclear weapons and subsequent reassembly or 'bouncing' around, would be to avoid nuclear weapons when possible. A gravity tractor would not introduce such a risk

[Mordred]

Both the use of nukes and impactor method has the risk of breaking apart the asteroid. Asteroid composition being a factor for the likely hood. Even though you only get the radiation portion and not the kinetic shock waves from the nuke. There is still a risk. One risk is thar if you have non uniform outgassing this can lead to breakage.

[Airbrush]

On 5/30/2024 at 8:35 PM, zapatos said:

 

https://en.wikipedia.org/wiki/Asteroid_impact_avoidance#:~:text=In addition%2C an asteroid may,to gravity after being disrupted.

Thanks for the link!

"In 2011...scientists began to study strategies that could deal with 200–1,600 ft objects when the time to Earth impact was less than one year. He concluded that to provide the required energy, a nuclear explosion or other event that could deliver the same power, are the only methods that can work against a very large asteroid within these time constraints."

"A study published in 2020...researchers ran a model that suggested a nuclear detonation near the surface of an asteroid designed to cover one side of the asteroid with x-rays would be effective. When the x-rays cover one side of an asteroid in the program, they produce propulsion energy that would propel the asteroid in a preferred direction...a nuclear impact offered more flexibility than a non-nuclear approach, as the energy output can be adjusted specifically to the asteroid's size and location."

Again, thanks.  I had not even thought of searching Wiki for this.

 

Edited June 1 by Airbrush

[Mordred]

I seem to recall someone mentioning a reference for the nuke method in regards to the radiation vs kinetic shock wave you get for atmospheric explosion  that last link highlights thar detail. Just in case anyone missed that.

[Ken Fabian]

On 6/1/2024 at 2:56 PM, Moontanman said:

It's interesting that there exists an asteroid with a ring,I wonder if a strike from a solid asteroid on a rubble pile asteroid gives some validity to to your idea? 

Just my understanding that evolution of a gravity bound cloud of material should settle into a ring (or possibly more than one) that can coalesce over longer time into a second object or more than one. I think much will depend on how much total rotational momentum of the "system" created and I don't know what the time scales would be to become a ring... centuries, millennia, more?

 

On 6/2/2024 at 2:15 AM, Mordred said:

I seem to recall someone mentioning a reference for the nuke method in regards to the radiation vs kinetic shock wave you get for atmospheric explosion  that last link highlights thar detail. Just in case anyone missed that.

 

I would expect that close proximity detonations would explosively vaporize surface material and the shock wave of that will travel through the object.

I'm still inclined to consider penetrating munitions, even as a preparatory first strike ahead of a second dispersing nuclear blast; if there is one area of engineering that we don't stint on, that we are very good, at it is weaponry. A real asteroid threat would be worth more than one device.

[Moontanman]

11 hours ago, Ken Fabian said:

Just my understanding that evolution of a gravity bound cloud of material should settle into a ring (or possibly more than one) that can coalesce over longer time into a second object or more than one. I think much will depend on how much total rotational momentum of the "system" created and I don't know what the time scales would be to become a ring... centuries, millennia, more?

 

 

I would expect that close proximity detonations would explosively vaporize surface material and the shock wave of that will travel through the object.

I'm still inclined to consider penetrating munitions, even as a preparatory first strike ahead of a second dispersing nuclear blast; if there is one area of engineering that we don't stint on, that we are very good, at it is weaponry. A real asteroid threat would be worth more than one device.

Dispersal could be a double edged sword, the asteroid represents a huge amount of kinetic energy, even dispersed the fragments would transfer the same amount of energy to the Earth as the solid object. Changing the objects orbit so it doesn't hit at all would be the best outcome, IMHO.  

[zapatos]

3 minutes ago, Moontanman said:

Dispersal could be a double edged sword, the asteroid represents a huge amount of kinetic energy, even dispersed the fragments would transfer the same amount of energy to the Earth as the solid object. Changing the objects orbit so it doesn't hit at all would be the best outcome, IMHO.  

Well, they would at least transfer the same amount of energy to earth's atmosphere anyway, right? While a large object may make it to the surface, many small objects may not.

[Moontanman]

3 minutes ago, zapatos said:

Well, they would at least transfer the same amount of energy to earth's atmosphere anyway, right? While a large object may make it to the surface, many small objects may not.

It would depend on the size of the initial object but the transfer of energy to the atmosphere from a large object would be devastating even if dispersed.    

[zapatos]

1 hour ago, Moontanman said:

It would depend on the size of the initial object but the transfer of energy to the atmosphere from a large object would be devastating even if dispersed.    

Seems like it MIGHT be devastating even if dispersed. Even a nuclear bomb would have minimal impact if its energy were spread over thousands of square miles.

[Moontanman]

17 minutes ago, zapatos said:

Seems like it MIGHT be devastating even if dispersed. Even a nuclear bomb would have minimal impact if its energy were spread over thousands of square miles.

A nuclear bomb, currently that would be a max of around 3 megatons if an asteroid like Apophis his it would be around 1000 megatons.

https://www.planetary.org/articles/will-apophis-hit-earth

What would happen if Apophis hit Earth?

Apophis would cause widespread destruction up to several hundred of kilometers from its impact site. The energy released would be equal more than 1,000 megatons of TNT, or tens to hundreds of nuclear weapons.

BTW a pop up ad just wiped out what I was writing in response to this post. 

[zapatos]

19 minutes ago, Moontanman said:

A nuclear bomb, currently that would be a max of around 3 megatons if an asteroid like Apophis his it would be around 1000 megatons.

https://www.planetary.org/articles/will-apophis-hit-earth

What would happen if Apophis hit Earth?

Apophis would cause widespread destruction up to several hundred of kilometers from its impact site. The energy released would be equal more than 1,000 megatons of TNT, or tens to hundreds of nuclear weapons.

BTW a pop up ad just wiped out what I was writing in response to this post. 

But again, it depends on the dispersal. Isn't it clear that the more dispersed the less the impact?

[Ken Fabian]

Smaller ones dispersed late but most of the rubble still hitting should reduce damage. Larger ones, no, with significant consequences just from atmospheric heating from a large enough debris cloud, without big surface impacts. Doing it far enough out that dispersal means few or preferably none of significance hitting Earth (including atmosphere) would be the intention.

But this has already been discussed. I think we are just repeating what has already been said - disagreeing without resolution - so unless something new comes up I'll withdraw from the discussion. Been interesting, got me reading things I hadn't come across before, not a waste of time. Thanks all. 

[zapatos]

 

Quote

The Vera C. Rubin Observatory, nearing completion on a mountaintop in northern Chile, features a telescope that’s enormous but also incredibly agile. The telescope, with a primary mirror 28 feet across and a 3.2-gigapixel camera, will sweep across the sky night after night, requiring a mere five seconds to reposition itself after each 15-second exposure. Thanks to its large field of view—encompassing an area equivalent to 40 full moons—and its ability to move swiftly, the telescope will scan the entire visible sky every three days. 

“Every night we’ll see about ten million things change in brightness or position,” says Mario Jurić, an astronomer at the University of Washington in Seattle. “Out of those ten million, you want to select a handful that may be worth following up.”

The Rubin Observatory is expected to discover millions of previously unknown asteroids—small rocky bodies that have been circling the sun for billions of years but have eluded detection because they reflect only a tiny amount of sunlight.

Today, astronomers are aware of only about 40 percent of potentially hazardous asteroids—close-flying objects that are large enough to cause continent-wide destruction if they were to impact Earth, Jurić says. With Rubin, astronomers should be able to detect up to 80 percent of such objects. “This is one discovery that all of us are hoping we won’t make,” he says. “But the idea is, if there is an object like that, we want to find it while it’s maybe 40 or 50 years out, because that gives us enough time to figure out how we’re going to deflect it.”

https://www.smithsonianmag.com/science-nature/this-revolutionary-new-observatory-will-locate-threatening-asteroids-and-millions-of-galaxies-180984514/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=editorial&spMailingID=49882089&spUserID=MTI5NTk5ODgyMTA1NAS2&spJobID=2722255208&spReportId=MjcyMjI1NTIwOAS2