Asteroid defense ideas

[Mordred]

Nice alternative method list on that link. Several mentioned there that hasn't been mentioned this thread.

I did previously mention kinetic impact but no one has spent any examining that option. Didn't know about that particular test though thanks for sharing.

@Ken Fabian I particularly like the first article in so far as it included fuel consumption as well as a dollar value given in 1995 roughly.  Thanks for sharing that link as well.

That low deflection value you gave over time is accurate however as you only need enough deflection to miss the gravitational keyhole the needed deflection  only requires 20 days but if process starts in the later on that can change to 135 days or greater explained in the first link. 

Edited May 27 by Mordred

[Airbrush]

2 hours ago, zapatos said:

So now you are saying we DO have the time?

Aren't many small bombs the same as one large bomb? We can use 100 small or one large. Basically the same thing I believe.

It seems to me an indirect method as a gravity tractor, will take much longer to put into action, than a direct method of launching a series of strikes on the asteroid.  At least get a few rocket nukes on their way to the object.  We don't know how much time we have.  We don't want to be late in saving the world from massive destruction.

There is no 100-megaton nuke.  Tzar Bomba was less than 58 megatons.  Better to send what we already have thousands of small nukes to "fine-tune" changes to the object's trajectory.  You blast it with one and measure the response, then hit it with another.  It will be rotating, but that's ok, just keep pushing it in the same direction.

[zapatos]

9 minutes ago, Airbrush said:

It seems to me an indirect method as a gravity tractor, will take much longer to put into action, than a direct method of launching a series of strikes on the asteroid.

I would think they'd both be put into action at roughly the same time. That is, as soon as they arrive at the asteroid. While a direct strike vehicle wouldn't need to adjust course near the end of the trip and thus would arrive sooner, I don't know why that time would be significant.

11 minutes ago, Airbrush said:

We don't know how much time we have. 

Why not? As soon as we spot the asteroid and determine it is a collision risk, don't we know rather precisely how much time we have?

13 minutes ago, Airbrush said:

There is no 100-megaton nuke.   Bomba was less than 58 megatons.

Only because of how it was constructed. It easily could have yielded more than 100 megatons.

Quote

The explosive power of the bomb could have easily been raised by another 50 Mt by using a uranium-238 sheath instead of lead.^[37] It was consciously decided to replace the cladding material and thus decrease the yield in order to reduce radioactive fallout below an acceptable level.

https://en.wikipedia.org/wiki/Tsar_Bomba#Test

[dimreepr]

9 hours ago, Airbrush said:

It seems to me an indirect method as a gravity tractor, will take much longer to put into action, than a direct method of launching a series of strikes on the asteroid.  At least get a few rocket nukes on their way to the object.  We don't know how much time we have.  We don't want to be late in saving the world from massive destruction.

There is no 100-megaton nuke.  Tzar Bomba was less than 58 megatons.  Better to send what we already have thousands of small nukes to "fine-tune" changes to the object's trajectory.  You blast it with one and measure the response, then hit it with another.  It will be rotating, but that's ok, just keep pushing it in the same direction.

A big enough lump of lead, travelling at a relatively big enough speed, would put those numbers to shame.

Why is so much of this discussion, so emotionally charged?

 

[Ken Fabian]

On 5/27/2024 at 12:17 PM, Mordred said:

I did previously mention kinetic impact but no one has spent any examining that option.

Not missed out but it doesn't stand out as an option except in the sense that at small scale it would be the easiest to attempt using existing technologies. According the the Nuclear Devices for Planetary Defense link (included in the quote I used - KI being Kinetic Impactor)  -

Quote

 By comparison (with 1Mt NED), imparting a velocity change of ~6.7 cm/s to a similar
model asteroid using KIs requires a total KI spacecraft mass of 605,900 kg

605 metric tons is a LOT of mass to launch, far beyond existing capabilities. And (if I understand it) high speed impacts shed a lot of energy as heat and explosively, not all will be delivered as changed momentum in line with the direction of the impact. Not necessarily a problem and possibly advantage if sideways deflection does it better.

I still look at meteorite defense as a longer term challenge; yes one could be identified tomorrow but the odds favor not. In terms of odds a too ambitious "being prepared" program could look like waste -

Note that this looks at risks from objects within the solar system - there remains the possibility, if very low likelihood, of large objects from outside the observable solar system.

Edited May 28 by Ken Fabian

[Airbrush]

On 5/27/2024 at 6:02 AM, dimreepr said:

A big enough lump of lead, travelling at a relatively big enough speed, would put those numbers to shame.

Why is so much of this discussion, so emotionally charged?

 

Depending on the size and composition of the object, a big enough lump of lead traveling at a big enough speed could be very effective against the smaller objects, even rubble piles.  Velocity is squared so twice the speed means 4 times the KE.  If you hit a solid metal or rocky object far enough away a tiny impact may be enough to change its' course to miss earth.  If you hit a rubble pile far enough away, you may scatter the fragments so wide that only a few small pieces will make it to earth.

Discussion about saving the world from destruction may be emotional.

On 5/26/2024 at 8:39 PM, zapatos said:

I would think they'd both be put into action at roughly the same time. That is, as soon as they arrive at the asteroid. While a direct strike vehicle wouldn't need to adjust course near the end of the trip and thus would arrive sooner, I don't know why that time would be significant.

Why not? As soon as we spot the asteroid and determine it is a collision risk, don't we know rather precisely how much time we have?

Only because of how it was constructed. It easily could have yielded more than 100 megatons.

https://en.wikipedia.org/wiki/Tsar_Bomba#Test

1  The technology needed for a gravity tractor takes more engineering, cost, and time, than a direct method like hitting it with a mass or exploding a nuke nearby.  How much more time I don't know, but I think it would be significant.

2  We don't know when we might spot an asteroid, but after you do spot it, you hope you have time to do something.

3  Do you think it is worth trying to develop a 100-megaton bomb when we have thousands of smaller nukes.

"...the US likely has around 100 nuclear warheads with yields of at least one megaton, primarily in the form of the B83 bombs. This number is a rough estimate and may change due to ongoing disarmament efforts and modernization programs." - ChatGPT

If you have 100 warheads that yield at least one megaton, that sounds like enough individual impacts to address most threats.  No mention of comets so far, why not?  Because comets come from ANYWHERE, not just the plane of the solar system, and are much harder to detect.

[swansont]

6 minutes ago, Airbrush said:

Depending on the size and composition of the object, a big enough lump of lead traveling at a big enough speed could be very effective against the smaller objects, even rubble piles.  Velocity is squared so twice the speed means 4 times the KE.  If you hit a solid metal or rocky object far enough away a tiny impact may be enough to change its' course to miss earth.  If you hit a rubble pile far enough away, you may scatter the fragments so wide that only a few small pieces will make it to earth.

As Ken Fabian pointed out it’s the momentum imparted that matters. If you hit a rubble pile with a high KE projectile it might just blast through it; the part it hits would recoil but the remaining parts would continue on their path. 

 

[zapatos]

15 minutes ago, Airbrush said:

3  Do you think it is worth trying to develop a 100-megaton bomb when we have thousands of smaller nukes.

 

No. I never said we should.

16 minutes ago, Airbrush said:

The technology needed for a gravity tractor takes more engineering, cost, and time, than a direct method like... exploding a nuke nearby.

Citation?

[Airbrush]

1 minute ago, swansont said:

As Ken Fabian pointed out it’s the momentum imparted that matters. If you hit a rubble pile with a high KE projectile it might just blast through it; the part it hits would recoil but the remaining parts would continue on their path. 

 

Depending on the size of the rubble pile, a kinetic impactor can blow it to pieces, and if that happens far enough away, it will scatter the pieces far and wide so only a few tiny pieces may make it to earth, if any do.

[zapatos]

17 minutes ago, Airbrush said:

We don't know when we might spot an asteroid, but after you do spot it, you hope you have time to do something.

Seems self evident.

[swansont]

8 minutes ago, Airbrush said:

Depending on the size of the rubble pile, a kinetic impactor can blow it to pieces, and if that happens far enough away, it will scatter the pieces far and wide so only a few tiny pieces may make it to earth, if any do.

If it’s small it’s not a threat. Missiles tend to not be large compared to a few-hundred-meters-wide target, and rubble piles do not have tightly-bound components, so not much momentum would be transferred to the rubble away from the impact area.

Not to mention the difficulty in targeting, which gets harder as closing speed increases.

[zapatos]

10 minutes ago, Airbrush said:

"Diverting an asteroid can be approached using various methods, each with its own timeframe for effectiveness. Among the methods you mentioned—gravity tractor, direct kinetic impactor, and nuclear explosion near the object—the gravity tractor would generally take the most time to work. Here’s a comparison of each method:

1. Gravity Tractor:

   • Mechanism: A spacecraft hovers near the asteroid, using its gravitational pull to slowly alter the asteroid’s trajectory over time.
   • Timeframe: This method requires a prolonged period to have a significant effect, often taking years to decades to produce a noticeable change in the asteroid's path. The effectiveness depends on the mass of the spacecraft, the proximity to the asteroid, and the duration of the operation.

2. Direct Kinetic Impactor:

   • Mechanism: A spacecraft or projectile is deliberately crashed into the asteroid at high speed to impart momentum and alter its trajectory.
   • Timeframe: The kinetic impactor method can produce more immediate changes compared to a gravity tractor. The effect on the asteroid’s trajectory occurs at the moment of impact, but the degree of change depends on the mass and speed of the impactor and the asteroid’s characteristics. While it acts relatively quickly, achieving significant deflection might still take years, depending on the warning time and required trajectory change.

3. Nuclear Explosion Near the Object:

   • Mechanism: A nuclear device is detonated near the asteroid to vaporize part of its surface, creating a jet of debris that propels the asteroid in the opposite direction.
   • Timeframe: A nuclear explosion would result in a rapid and significant change in the asteroid's trajectory. The explosion causes an immediate reaction, potentially providing a substantial deflection in a short period. However, precise control of the outcome is more challenging compared to other methods.

   • In summary, the gravity tractor method takes the longest time to work among the three, as it involves a slow and gradual alteration of the asteroid’s trajectory over an extended period. The kinetic impactor acts faster but still requires a relatively longer timeframe compared to a nuclear explosion, which can achieve immediate and significant changes."

     - ChatGPT

(Note: I may be mistaken but I don't believe ChatGPT is allowed on this site for use as a citation. )

But that is neither here nor there as I agree a gravity tractor needs more time to achieve results. I am actually more interested in your claim that a gravity tractor requires more engineering and cost than exploding a nuke. While the results you'd achieve with a gravity tractor are well understood, knowing the size of a nuke to use, the altitude to explode above (or on) the asteroid, knowing the composition of the asteroid so that predictions of the result can be made, etc., may require extensive time and effort.

[swansont]

2 minutes ago, zapatos said:

Note: I may be mistaken but I don't believe ChatGPT is allowed on this site for use as a citation. )

You are correct. It carries no more weight than “some guy on the street told me”

[TheVat]

I suggested a laser weapon on page one.  I don't know what percent of asteroids are of a composition that would lend itself to thrust-producing outgassing on one side, but for them the beam would seem to offer precision and periodic adjustments like no other option.  And maximum effect per joule.  Problems include attenuation, given that our solar system is not a perfect vacuum.  And expense - though maybe that compares favorably with putting hundreds of warheads on long-distance rockets.  

 

[zapatos]

2 minutes ago, TheVat said:

I don't know what percent of asteroids are of a composition that would lend itself to thrust-producing outgassing on one side, but for them the beam would seem to offer precision and periodic adjustments like no other option. 

I question whether or not that would that be more precise and adjustable than a gravity tractor. Center of gravity of the asteroid to center of gravity of the tractor is rather precise, as would be the ability to move the tractor relative to the asteroid.

[Moontanman]

A laser sounds great but I have to ask how close would you have to be to use a high powered laser in that manner? Even a lasar spreads out as it travels.   

[TheVat]

7 minutes ago, Moontanman said:

A laser sounds great but I have to ask how close would you have to be to use a high powered laser in that manner? Even a lasar spreads out as it travels.   

Attenuation, as I mentioned, is the big question.  I think beam spread can be greatly reduced, since it is a laser.  But I don't know how the imperfect vacuum of the solar system would affect that.  

13 minutes ago, zapatos said:

I question whether or not that would that be more precise and adjustable than a gravity tractor. Center of gravity of the asteroid to center of gravity of the tractor is rather precise, as would be the ability to move the tractor relative to the asteroid.

When people say "it's not rocket science," they are definitely not describing this discussion.  I will have to learn more about the tractor concept, which sounds incredibly slow-acting to me on first view.  

[Moontanman]

Here is an explanation of laser divergence. 

https://en.wikipedia.org/wiki/Beam_divergence

I am math impaired so I am not sure how to use this information but I am sure someone here could. 

[TheVat]

It's a Gaussian function.  I can plug numbers in, but I am not qualified to explain it.  It does look as if shorter wavelengths would be advantageous, at least WRT to beam divergence.  But then there's the question of optimum wavelength for ablation of asteroid surface.  Here's a summary of the laser ablation concept....

 

https://en.wikipedia.org/wiki/Asteroid_laser_ablation

[Moontanman]

6 minutes ago, TheVat said:

It's a Gaussian function.  I can plug numbers in, but I am not qualified to explain it.  It does look as if shorter wavelengths would be advantageous, at least WRT to beam divergence.  But then there's the question of optimum wavelength for ablation of asteroid surface.  Here's a summary of the laser ablation concept....

 

https://en.wikipedia.org/wiki/Asteroid_laser_ablation

Interesting for sure, if the distance is too much to over come from Earth orbit why couldn't the laser be moved closer to the target? If the laser is going to be in orbit anyway and if time permits just move the laser closer?  I'm not sure how big the space craft containing the laser would have to be but I would assume it could be built ahead of time and stored in orbit until it was needed? 

[Mordred]

6 minutes ago, Moontanman said:

Interesting for sure, if the distance is too much to over come from Earth orbit why couldn't the laser be moved closer to the target? If the laser is going to be in orbit anyway and if time permits just move the laser closer?  I'm not sure how big the space craft containing the laser would have to be but I would assume it could be built ahead of time and stored in orbit until it was needed? 

Considering they have now missile defense lasers on US ships if I recall I would say it would be transportable on some craft. Albeit I wouldn't know the power requirements.

Something similar to the power requirements here could be workable

https://en.m.wikipedia.org/wiki/AN/SEQ-3_Laser_Weapon_System

Another options being LaWs

https://www.cnn.com/2014/12/11/tech/innovation/navy-laser-weapon

[Moontanman]

5 minutes ago, Mordred said:

Considering they have now missile defense lasers on US ships if I recall I would say it would be transportable on some craft. Albeit I wouldn't know the power requirements.

On the face of it this would seem to be the best if not the fastest way to go in this endeavor. The basic idea behind deflecting an asteroid being conveying energy to the asteroid in a controlled manner? 

Edited May 28 by Moontanman

[Mordred]

To generate heat and outgassing on the surface areas to apply Newtons second and third laws without causing large chunks to separate from the asteroid. Those I suggested may or may not work depending on laser sustainability and ability to reduce the output in case it's needful. This method would well on an icy asteroid possibly a solid rock face not too sure the practicality for a conglomerate surface.

The other issue being rotation.

I have been wondering the practicality of a single craft with both nukes and lasers the combined weight would also make it a suitable tractor but then a single craft could theoretically be equipped with all three options.

Edited May 28 by Mordred

[Moontanman]

2 hours ago, Mordred said:

To generate heat and outgassing on the surface areas to apply Newtons second and third laws without causing large chunks to separate from the asteroid. Those I suggested may or may not work depending on laser sustainability and ability to reduce the output in case it's needful. This method would well on an icy asteroid possibly a solid rock face not too sure the practicality for a conglomerate surface.

The other issue being rotation.

I have been wondering the practicality of a single craft with both nukes and lasers the combined weight would also make it a suitable tractor but then a single craft could theoretically be equipped with all three options.

To tell the honest truth IMHO, whatever we do, our only real hope is to plan ahead, this discussion should be taking place way before now and action should already be in place. I know others have discussed this but here we are with nothing to protect us... action is needed. 

I think the current worry is over Apophis, some 300 meters across? Imagine the cluster fuck if it was found that this asteroid was going to hit instead of passing us by in a few years, could we do anything even with such a long warning time? 

The time to have started this was 20 years ago, anything we do will require years of lead up time, prototyping, testing, not to mention getting international laws bypassed. 

This should be a major worry for everyone.  

A side note, if we could, wouldn't be better to direct an asteroid into the Moon or another body, just to make sure it doesn't come back around in a thousand years or so, or would this just open another can of worms? 

[Mordred]

Well I agree our government's should push to get better early warning detection as well as contingency plans in place thankfully though some testing has occurred already. A few were mentioned in this thread.

The moon idea isn't a bad one by the way. Provided the size of asteroid doesn't cause too significant of  damage. Though an asteroid of that magnitude would likely not be able to redirect with our current capabilities.