Author Topic: Deflecting or destroying dangerous asteroids  (Read 59642 times)

Offline whitelancer64

Re: Deflecting or destroying dangerous asteroids
« Reply #120 on: 08/22/2017 04:17 pm »
On top of the impactor we put a smaller version of the proposed Orion damper with a large nuke behind it. The impactor now has a high delta-V. Just Before impact, we detonate the nuke and give the impactor at huge boost in speed. Plus any energy the nuke itself Projects around the plate.
What do you gain by transferring energy from the nuke, to the impactor and then to the target? Why not cut out the middle man?

In general, nukes have the highest energy density, so launching a combination of nukes + kinetic impactors gives you less capability than using the same mass of nukes alone. Kinetic impactors are technically and politically simpler, so they are attractive in cases where they provide sufficient energy in a reasonable launch mass.

Yes, really should have thought about that. How ever I read only 40% of the nukes energy is radiation and what not. If we put a gas between the impactor and the nuke. Could we also harwest the pressure wave in som manner and get more energy out of it?

NASA has a small side project called Hypervelocity Asteroid Intercept Vehicle (HAIV), which proposes sending an impactor and a nuclear device along the same mission. The impactor hits first, creating a small crater which the nuclear device then detonates in. Similar to your idea.
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Offline hop

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Re: Deflecting or destroying dangerous asteroids
« Reply #121 on: 11/16/2017 09:34 pm »
NASA has released a report on the current status of planetary defense efforts https://www.nasa.gov/feature/new-report-assesses-status-of-detecting-near-earth-asteroids

I haven't read it yet, but the summary suggests the big picture hasn't changed too much.

Offline dustinthewind

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Re: Deflecting or destroying dangerous asteroids
« Reply #122 on: 12/10/2017 10:03 pm »
Something neat I have seen recently they want to make was a space based phased array that could superheat a point.  With enough energy the rock can be vaporized and acts like a rocket via the vaporization.  The object can be diverted with out much delay as the energy travels at the speed of light.  I think they also suggested other uses for it such as photon propulsion for spacecraft and moving asteroids for mining, power transport. 

I had pondered an earth based array that used atmosphere correction similar to some telescopes.

I guess it is the DE-STAR project. 
« Last Edit: 12/10/2017 11:31 pm by dustinthewind »
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Offline LMT

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Re: Deflecting or destroying dangerous asteroids
« Reply #123 on: 12/11/2017 02:08 am »
Something neat I have seen recently they want to make was a space based phased array that could superheat a point.  With enough energy the rock can be vaporized and acts like a rocket via the vaporization.  The object can be diverted with out much delay as the energy travels at the speed of light.  I think they also suggested other uses for it such as photon propulsion for spacecraft and moving asteroids for mining, power transport. 

I had pondered an earth based array that used atmosphere correction similar to some telescopes.

For an estimate of deflection capability, Zhang et al. 2016 quantifies expected deflection for asteroids and comets, using stand-off DE-STAR and also the smaller stand-on DE-STARLITE.
« Last Edit: 12/11/2017 02:09 am by LMT »

Offline cube

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Re: Deflecting or destroying dangerous asteroids
« Reply #124 on: 08/22/2022 02:20 pm »
Hello, when a nuclear bomb explodes on Earth it causes a blast, a shock wave that can blow and repel objects.
On the other hand, in space, to my knowledge, a nuclear bomb could not cause a blast, a shock wave because of the absence of air.
So how could a nuclear bomb deflect an asteroid ?
Thanks !
« Last Edit: 08/22/2022 02:21 pm by cube »

Online Mark K

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Re: Deflecting or destroying dangerous asteroids
« Reply #125 on: 08/22/2022 03:29 pm »
The shock wave in the atmosphere is created by radiation hitting the air molecules. That same radiation pressure will hit the asteroid.  Plus some vaporized parts of the bomb, but basically the radiation pressure.

This is considering the case of the idea of detonating the bomb "near" the asteroid which would be preferred if the asteroid is small enough since detonation after impact would likely just cause the small enough asteroid to become zillions of pebbles as seen in the "landings" of several probes.

Online JayWee

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Re: Deflecting or destroying dangerous asteroids
« Reply #126 on: 08/22/2022 03:30 pm »
On the other hand, in space, to my knowledge, a nuclear bomb could not cause a blast, a shock wave because of the absence of air.
It will. See the Project Orion. (the nuclear one, not the Artemis one).


Online DanClemmensen

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Re: Deflecting or destroying dangerous asteroids
« Reply #127 on: 08/22/2022 03:53 pm »
Hello, when a nuclear bomb explodes on Earth it causes a blast, a shock wave that can blow and repel objects.
On the other hand, in space, to my knowledge, a nuclear bomb could not cause a blast, a shock wave because of the absence of air.
So how could a nuclear bomb deflect an asteroid ?
Thanks !
The fundamental principle here is conservation of momentum of the system.
  https://en.wikipedia.org/wiki/Momentum#Conservation
The center of mass of the system as a whole stays on the same trajectory. To shift the asteroid  to the left, (i.e., to change the trajectory), you change its momentum. To do this you must change the momentum of something else by moving that something to the right. When the bomb explodes, the system must throw a lot of mass at lower velocity or a smaller amount of mass at higher speed to the right.  Consider a bomb that penetrates and explodes a meter below the surface. It will throw the stuff "on top" of itself directly out. It will also throw a lot of energy into the material "below" itself. This will produce a crater. The ejected material will on average go "up" at high velocity, which, by conservation of momentum, means that the rest of the asteroid must go "down".

Offline cube

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Re: Deflecting or destroying dangerous asteroids
« Reply #128 on: 08/22/2022 05:28 pm »
Would the radiation pressure be sufficient?
I have always had the image of radiation pressure as the very weak force pushing a solar sail.
I read about the orion project and if I understood correctly they would have used a nuclear bomb where the radiation is converted into heat with a material opaque to the radiation and then this heat is directed towards a tungsten plate which vaporizes and the plasma resulting from this vaporization would have hit the thrust plate which would have created the thrust. So he wasn't using the radiation pressure to push her, not directly.
I don't know if the radiation pressure alone would have been enough to create enough thrust.
« Last Edit: 08/22/2022 05:29 pm by cube »

Online lamontagne

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Re: Deflecting or destroying dangerous asteroids
« Reply #129 on: 08/22/2022 06:04 pm »
Would the radiation pressure be sufficient?
I have always had the image of radiation pressure as the very weak force pushing a solar sail.
I read about the orion project and if I understood correctly they would have used a nuclear bomb where the radiation is converted into heat with a material opaque to the radiation and then this heat is directed towards a tungsten plate which vaporizes and the plasma resulting from this vaporization would have hit the thrust plate which would have created the thrust. So he wasn't using the radiation pressure to push her, not directly.
I don't know if the radiation pressure alone would have been enough to create enough thrust.
You have it right, but the other answer is also more or less correct.  The asteroid would act as a pusher plate and be deflected by the plasma from the explosion of an Orion type shaped charge. Even though the asteroid is probably not a very good pusher plate, but it's basically action and reaction Newtonian physics.
To increase the effectiveness you might want to detonate the nuclear charge close enough to the asteroid to vaporize some of the asteroids material into a gas, or even into a plasma.  Depending on how effective the coupling is, and how the hole dug into the asteroid shaped itself, you would end up with a short lived but very energetic jet that would push the asteroid onto a new course.
If the asteroid was not strong enough, then it might break itself into smaller bits, and some of these might still be on the original trajectory.  So there probably is an art to it.
« Last Edit: 08/22/2022 06:06 pm by lamontagne »

Offline cube

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Re: Deflecting or destroying dangerous asteroids
« Reply #130 on: 08/22/2022 07:42 pm »
So if I understand correctly a nuclear bomb without a tungsten plate which would explode near an asteroid would only produce radiation (ignoring the vaporized bomb shell) and it would produce radiation pressure on the asteroid (like light sun on a solar sail) but I imagine that this radiation pressure alone would create such weak thrust on the asteroid that it wouldn't deflect it?

On the other hand, if this same bomb explodes close enough to the asteroid, the radiation from the bomb could heat the surface of the asteroid enough to cause it to vaporize and transform part of it into gas or plasma which, by escaping from the surface of the asteroid, asteroid would cause significant thrust and deflect it.
« Last Edit: 08/22/2022 07:46 pm by cube »

Online DanClemmensen

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Re: Deflecting or destroying dangerous asteroids
« Reply #131 on: 08/22/2022 08:11 pm »
So if I understand correctly a nuclear bomb without a tungsten plate which would explode near an asteroid would only produce radiation (ignoring the vaporized bomb shell) and it would produce radiation pressure on the asteroid (like light sun on a solar sail) but I imagine that this radiation pressure alone would create such weak thrust on the asteroid that it wouldn't deflect it?

On the other hand, if this same bomb explodes close enough to the asteroid, the radiation from the bomb could heat the surface of the asteroid enough to cause it to vaporize and transform part of it into gas or plasma which, by escaping from the surface of the asteroid, asteroid would cause significant thrust and deflect it.
You will need to do the math. Your bomb releases a certain amount of energy, say 100 megaton of TNT equivalent. Assume this energy  spread in a uniform sphere. You can compute the percentage that intersects the surface of a asteroid. Some will be reflected and transfer momentum like a light sail, while the  rest will be absorbed and be converted to heat. A lot of heat. That heat will boil off material that will leave the asteroid surface in directions that to a first approximation average to the direction of the bomb: basically a great big inefficient rocket motor. Unless your bomb is quite far from the asteroid, this effect will be much larger than the radiation pressure. To do the math, you will need to know the spectrum of the bomb's radiation, the reflectivity of the of the asteroid's surface, the volatility of the asteroid's material, and the distance from the bomb to the asteroid.

Offline whitelancer64

Re: Deflecting or destroying dangerous asteroids
« Reply #132 on: 08/22/2022 08:41 pm »
So if I understand correctly a nuclear bomb without a tungsten plate which would explode near an asteroid would only produce radiation (ignoring the vaporized bomb shell) and it would produce radiation pressure on the asteroid (like light sun on a solar sail) but I imagine that this radiation pressure alone would create such weak thrust on the asteroid that it wouldn't deflect it?

On the other hand, if this same bomb explodes close enough to the asteroid, the radiation from the bomb could heat the surface of the asteroid enough to cause it to vaporize and transform part of it into gas or plasma which, by escaping from the surface of the asteroid, asteroid would cause significant thrust and deflect it.

Don't forget Newton's second law: For every action (no matter how small) there is an equal and opposite reaction. ANY thrust, even that of a mosquito landing on it, would alter the course of an asteroid by a very, very tiny amount.

Radiation pressure alone would be sufficient, but -- although this is heavily dependent on the construction of the asteroid -- vaporizing part of its surface would indeed produce more thrust.

In reply to DanClemmensen's comment:

Whitelancer64 points out to me that the most common US nuke developed for missile deployment is the W87, which has a yield of 475kT (updated from 300kt - see wiki), or ~17x less than my hypothetical 8Mt nuke.  However they are also lighter at ~250kg.

It's hard to believe that only one would be sent at a time (they were designed to be sent 12 at a time which is easily with the capability of an F9), but if it were, one would have to adjust the numbers in my table up (can't find the original table so just doing this by hand).  Again assuming 1% conversion to kinetic energy.

Time to deflect asteroid by one earth diameter for 1x W87, or 12x W87:
12km (Dino killer): 4930 days (13.5 years), 411 days
4km: 949 days (2.59 years), 79 days
1km: 117 days, 9.7 days
250m: 14 days, 1.2 days


... Again assuming 1% conversion to kinetic energy. Time to deflect asteroid by one earth diameter for 1x W87, or 12x W87:
250m: 14 days, 1.2 days
1) Where are getting the 1% conversion assumption? Is that based on vaporization of surface material?
Nothing so sophisticated.  The way I thought of it is that the explosive energy radiates evenly in all directions, and you don't necessarily want to explode a rubble pile so much as shift it.  You would probably perform a stand off explosion at some distance from the asteroid so the energy front from the bomb is roughly unidirectional.

Surface area of a sphere is 4πr2, (or 41253 square degrees) so 1% conversion to KinE assumes that the asteroid takes up about a 20 x 20 degree patch of sky relative to the bomb.  Or in other words, for a 250m asteroid, if the bomb is detonated 731m away, that means 1% of the energy from the bomb reaches the asteroid.  You could go closer, but you're more likely to break it up into multiple impactors.  1% was a nice round number.

Quote
2) After the Chelyabinsk meteor, Russia declared a single Dnepr (RS-36) with ten warheads (550-750kt each) would obliterate a 100m object with only a few hours notice. Impacting converts the majority of energy into kinetic - as opposed to simply brushing the surface with radiation. Having "bunker buster nukes" already designed for impacting is a bonus, unless you're the target.

Yeah but for anything in the 200m-1km range, you just break the asteroid into multiple impactors, which makes it way more likely that one of them hits a populated area.  Even a largish tsunami from a single ocean impact (that could be prepared for/evacuated from) would spread the damage out more than multiple chaotic airburst explosions on top of a heavily populated continent.


Speaking of which, Mods: please merge this thread with the existing thread:

"Deflecting or destroying dangerous asteroids"

https://forum.nasaspaceflight.com/index.php?topic=43359.0

[zubenelgenubi: Threads merged.]
« Last Edit: 08/24/2022 10:32 pm by zubenelgenubi »
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Offline sghill

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Re: Deflecting or destroying dangerous asteroids
« Reply #133 on: 08/24/2022 01:49 pm »
You have it right, but the other answer is also more or less correct.  The asteroid would act as a pusher plate and be deflected by the plasma from the explosion of an Orion type shaped charge. Even though the asteroid is probably not a very good pusher plate, but it's basically action and reaction Newtonian physics.
To increase the effectiveness you might want to detonate the nuclear charge close enough to the asteroid to vaporize some of the asteroids material into a gas, or even into a plasma.  Depending on how effective the coupling is, and how the hole dug into the asteroid shaped itself, you would end up with a short lived but very energetic jet that would push the asteroid onto a new course.
If the asteroid was not strong enough, then it might break itself into smaller bits, and some of these might still be on the original trajectory.  So there probably is an art to it.

I'd much rather get hit in the face with 1kg of gravel thrown at me than a 1kg solid rock....

Seriously though, I don't see why you'd want the bomb to go off above the surface. You'd want an impactor that triggers a fusion explosion at as as high an impact speed as possible as close to the surface as possible in order to liberate or vaporize as much material as possible. Ideally, the impactor is digging out a crater at tens of kilometers per second while the device is in the process of detonating so that a blast wave is created. If it detonates above the object, only radiation is emitted, but that radiation is 8-18 times higher than an atmospheric blast! (https://history.nasa.gov/conghand/nuclear.htm)

So that we can all grasp the sizes involved when intentionally creating nuclear craters, I submit the two largest- the 107kT "Sedan" nuclear test crater of 1962, and the nearly identical 140kT "Chagan" test crater in Kazakhstan in 1965: https://en.wikipedia.org/wiki/Sedan_Crater

Both explosions used ~100kt fusion devices with a mass of around 200kg buried at a depth 200m, and both liberated around 10 billion kg (1010) of rock in 1g gravity, creating craters approx. 400m wide.

For reference, the Earth-killer Apophis also has a mass of 1010 kg. with a .5km diameter, and you guys have been talking (for reference) about using the W87 warhead at 475kT.

If this kind of explosion occurred in space with the additional benefit of a high speed impact, anything smaller than Apophis would have been completely vaporized and turned into a rapidly expanding sand and gas ball at the 104kT sized explosion.

Looking at this linearly, I think we can state that with the ~4x larger W87 warhead, any snowball asteroid smaller than 2 kilometers would be completely annihilated and largely turned to gas, and any rock asteroid that size would be blown apart and the remaining rubble ejected outward by the explosion and liberated mass.

Lots of error bars here without knowing the exact composition and size, but knowing how fragile comets and asteroids are, and with the Sedan shot as a reference, I think a single W87 would eliminate the threat of anything smaller than 2km in diameter, and fewer than ten MERVS could eliminate comet and Eros sized asteroids and comets (6x1015 kg with 15km diameters).
« Last Edit: 08/24/2022 02:10 pm by sghill »
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Offline Asteroza

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Re: Deflecting or destroying dangerous asteroids
« Reply #134 on: 08/24/2022 11:09 pm »
Thing is, W87 is off the shelf more or less, but what we actually want is a nuclear shape charge like a Casaba Howitzer. for high directionality.

Online Mark K

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Re: Deflecting or destroying dangerous asteroids
« Reply #135 on: 08/25/2022 01:02 am »
Thing is, W87 is off the shelf more or less, but what we actually want is a nuclear shape charge like a Casaba Howitzer. for high directionality.

Yes, In answer to the previous the radiation pressure and energy deposition is far the largest thing to impart momentum.  The spalling and vaporization is just a consequence of the radiation that impart momentum. This is also true for the overpressure of a bomb on earth. It is all generated by gazillions of gamma and x rays and other re-emitted radiation. A shaped charge will cause more high energy radiation to be in the direction of the asteroid, so more efficient use of the bomb energy. We are talking radiation that would in milliseconds reduce your body to ionized molecules. Yes your molecules will be moving at very high speed in a direction, but all the momentum comes from the radiation.

Also you do not want a ball of spread out gravel to hit the atmosphere at escape velocity. The heating and energy imparted by the gravel will cause all the energy to be deposited in the atmosphere... not really what you want. You want the stuff to mostly miss.

Offline edzieba

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Re: Deflecting or destroying dangerous asteroids
« Reply #136 on: 08/25/2022 08:20 am »
'Nuclear shaped charges' are not any more efficient at directing the main X-ray pulse than a 'regular' warhead. Their trick is that they can couple the X-ray pulse that would hit have the target (be it pusher plate or asteroid/comet) to a tamper, and the vaporised tamper hitting the target couples momentum to the target more effectively than the X-ray pulse hitting directly.
Whether the inclusion of a tamper trades better for an 'asteroid buster' depends on whether your intent is to shatter the target or just deflect it, whether the size and composition means a 'bare' X-ray pulse is effective at shattering of deflecting the target, and whether removing the mass of the tampers from all devices launched and using that mass for additional devices provides improved effect (whatever that desired effect is).

Offline whitelancer64

Re: Deflecting or destroying dangerous asteroids
« Reply #137 on: 08/25/2022 06:07 pm »
Thing is, W87 is off the shelf more or less, but what we actually want is a nuclear shape charge like a Casaba Howitzer. for high directionality.

The point of using an "off the shelf" W87 is that you don't need some special design, very highly classified, shaped charge. You can do asteroid deflection with basic "vanilla" nuclear warheads, of which there are thousands available.
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Offline darkenfast

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Re: Deflecting or destroying dangerous asteroids
« Reply #138 on: 08/26/2022 01:35 am »
If the asteroid is of the "rubble pile" type, and the warhead is fairly rugged, what if it is just pushed or impacted INTO the asteroid some meters. I'm thinking of the recent probe experience, where it gently sank into the rubble. Would it impart enough "thrust" through the ejecta to alter the orbit enough to avoid a collision with Earth months down the line? Or, perhaps a penetrating conventional warhead (bunker-buster), followed by a nuclear device into the hole or crater created?

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Offline whitelancer64

Re: Deflecting or destroying dangerous asteroids
« Reply #139 on: 08/26/2022 03:16 pm »
If the asteroid is of the "rubble pile" type, and the warhead is fairly rugged, what if it is just pushed or impacted INTO the asteroid some meters. I'm thinking of the recent probe experience, where it gently sank into the rubble. Would it impart enough "thrust" through the ejecta to alter the orbit enough to avoid a collision with Earth months down the line? Or, perhaps a penetrating conventional warhead (bunker-buster), followed by a nuclear device into the hole or crater created?

Fun with explosives!

If done sufficiently in advance, an impact alone would be enough to deflect an asteroid. DART will demonstrate that. For a rubble pile, a stand-off nuclear detonation might disrupt the asteroid without having to impact it.

An impactor followed closely by a nuclear weapon detonating in the new crater is a good idea.

There was a proposed project called HAIV (Hypervelocity Asteroid Intercept Vehicle) that would do just that, create a crater for a following warhead to detonate in.

https://www.nasa.gov/directorates/spacetech/niac/2012_phaseII_fellows_wie.html
« Last Edit: 08/26/2022 03:17 pm by whitelancer64 »
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