Author Topic: Deflecting or destroying dangerous asteroids  (Read 10640 times)

Offline hop

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Re: Deflecting or destroying dangerous asteroids
« Reply #40 on: 07/25/2017 07:47 PM »
Somewhat related news today: There seem to be more large long period comets than previously estimated.

Large, Distant Comets More Common Than Previously Thought
https://www.jpl.nasa.gov/news/news.php?release=2017-197
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...
NASA's WISE spacecraft, scanning the entire sky at infrared wavelengths, has delivered new insights about these distant wanderers. Scientists found that there are about seven times more long-period comets measuring at least 0.6 miles (1 kilometer) across than had been predicted previously. They also found that long-period comets are on average up to twice as large as "Jupiter family comets," whose orbits are shaped by Jupiter's gravity and have periods of less than 20 years.
...

Paper (paywalled) Debiasing the NEOWISE Cryogenic Mission Comet Populations
« Last Edit: 07/25/2017 07:48 PM by hop »

Offline hop

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Re: Deflecting or destroying dangerous asteroids
« Reply #41 on: 07/25/2017 09:08 PM »
Regarding the effectiveness (or otherwise) of nuclear deflection, here's a paper from Bruck Syal et al in 2013 which reviews the subject:

Limits on the use of nuclear explosives for a steroid deflection (PDF via google scholar search for that title http://www.planetary.brown.edu/pdfs/4747.pdf)

An interesting bit on the energy deposition question:
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The simulated nuclear explosive was selected for optimized neutron output (high fusion to fission yield), as the cross-section of energetic neutrons is nearly independent of composition for materials between carbon and iron. This results in a penetration depth of 17g/cm^2, heating substantially more mass than the same flux of x-rays and providing a larger impulse for the same amount of incident energy.

On survey efficiency, supporting my earlier WAG about NEOCam and LSST
Modeling the Performance of the LSST in Surveying the Near-Earth Object Population - Tommy Grav, Amy Mainzer, Tim Spahr
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We further show that while neither LSST nor a space-based IR platform like NEOCam individually can complete the survey for 140m diameter NEOs, the combination of these systems can achieve that goal after a decade of observation.
No 20m telescopes required  ???

Offline Propylox

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Re: Deflecting or destroying dangerous asteroids
« Reply #42 on: 07/26/2017 05:03 AM »
Just to correct a misconception you have - deflection can be done in any direction. Slowing down an asteroid, pushing it to the side, or speeding it up would all work equally well to cause it to miss the Earth.
Ah, semantics. Altering a path in any direction can be "deflection", though that usually implies radial movement.
But radial movement adds momentum to a body and any physical deflection is likely to produce debris, some tiny - some massive, that maintain the original trajectory. This becomes a debris field stretching from original to intended trajectory. Decelerating an object removes momentum for the object, any debris, maintains a bulk field without drift and ensures almost all of it misses Earth.
Accelerating will also keep the object generally cohesive, but adds momentum. Whether decelerating or accelerating, it's amplified in ejected small debris. For this reason, I'd avoid accelerating an object to avoid collision and "only decelerate it".

Offline Propylox

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Re: Deflecting or destroying dangerous asteroids
« Reply #43 on: 07/26/2017 06:02 AM »
Hop, May I suggest some consistency in your claims, or at least acknowledge the lack of consistency in "the field" of so-called experts ...
While the 90% goal for >140m NEOs won't be met soon with current resources, LSST and existing surveys are expected to reach  ~70%
... planned upgrades + LSST + NEOCam  is probably enough to meet the 90% of 140m NEOs goal, or at least come fairly close.
"We further show that while neither LSST nor a space-based IR platform like NEOCam individually can complete the survey for 140m diameter NEOs, the combination of these systems can achieve that goal after a decade of observation."

No 20m telescopes required  ???
And still no ability to see objects small enough to deflect; no means to deflect objects we could possibly see. Our nuclear arsenal is equipped to stop 100m-sized meteors, according to Russia, but there's no means to find objects of that size or down to the 20-30m range equivalent to ICBM blasts.
Of course a 20m telescope would and do so in a couple years, not decades, while non-regular (new) orbits threatening Earth would be readily identified.

When those people are experts in the field, and their work is backed up by rigorous study, it's a lot more likely to be true than random individuals idle speculation. If you want to convincingly dispute the work of the people who have done detailed analysis of nuclear weapon effects on asteroids, you need to actually demonstrate that their match is wrong, not just say "nuh uh!"
Yeah, I'm not sure how you can call them "experts" without proving they have a clue or their "rigorous studies" can even agree - Without arguing their case or disputing mine, only asserting so. Position, authority and quoting such does not equate to truth.
There's no need to "convincingly dispute" their claims when they effectively do so to each other. What you've shown appears as "random individuals idle speculation" which you copy/pasted and declared as fact.

In citing "experts" working nuclear deterrence, including lectures of remedial information, none acknowledge the impossible distance, impossibly high number of warheads required or any means to implement. They're of no practical, actionable use - only speculative theory to support minimally effective actions.

The practice of science has advance significantly since Copernicus.
Unfortunately the intellectual integrity of those that follow science, and seem to enjoy citing others' work, apparently has not. If you understood the topic, not just recite it, you'd question your assertions as well.
« Last Edit: 07/26/2017 06:11 AM by Propylox »

Online whitelancer64

Re: Deflecting or destroying dangerous asteroids
« Reply #44 on: 07/26/2017 03:43 PM »
As noted in several posts above, it is possible to deflect massive asteroids, but more lead time is required to do so. We are in no way limited to only the deflection of 100 meter or smaller asteroids.

There have been many, many studies on asteroid deflection - not idle speculation by random people. Hop has cited some of them.

Why haven't you cited any studies to show you are correct? hmm...
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
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Offline hop

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Re: Deflecting or destroying dangerous asteroids
« Reply #45 on: 07/26/2017 04:10 PM »
And still no ability to see objects small enough to deflect;  no means to deflect objects we could possibly see.
You seem quite sure of this. How small is "small enough to deflect"? Are the calculations, models and assumptions this is based on published somewhere? Is this based on particular deflection methods or warning times?

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but there's no means to find objects of that size or down to the 20-30m range equivalent to ICBM blasts.
Do you have specific calculations showing that the overall risk from 20-30m asteroids is significant compared to that posed by 140+ meter bodies?
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Of course a 20m telescope would and do so in a couple years, not decades, while non-regular (new) orbits threatening Earth would be readily identified.
What size range would this 20m space telescope completeness >90% for, and how did you arrive that conclusion? How much is overall risk reduced by completing the survey in a "a couple years" rather than decades? Does this "couple years" account for construction time of the 20m telescope?

Also, your previous argument was not that smaller telescopes would be too slow, you said
Anything small enough for us to redirect is too small for us to see in time while anything we can see in time is too large to redirect. Unless we start putting +20m telescopes in space there's no point in developing redirect capabilities.
(my bold)
Taken at face value, this seems imply that you believe anything less provides no useful reduction of risk. Again, is this based on specific models or calculations? If not, why are you so confident that it's true?

edit:
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none acknowledge the impossible distance, impossibly high number of warheads required or any means to implement
Which specific scenarios in Bruck Syal et al paper linked above require "impossible" distance or warhead numbers? What models or calculation did you use to come to the conclusion that these scenarios are "impossible"?
« Last Edit: 07/26/2017 08:33 PM by hop »

Offline meberbs

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Re: Deflecting or destroying dangerous asteroids
« Reply #46 on: 07/26/2017 07:24 PM »
Hop, May I suggest some consistency in your claims, or at least acknowledge the lack of consistency in "the field" of so-called experts ...

Yeah, I'm not sure how you can call them "experts" without proving they have a clue or their "rigorous studies" can even agree - Without arguing their case or disputing mine, only asserting so. Position, authority and quoting such does not equate to truth.

There's no need to "convincingly dispute" their claims when they effectively do so to each other. What you've shown appears as "random individuals idle speculation" which you copy/pasted and declared as fact.
So now you are reduced to disputing the credentials of the people who study this for a living.

There is plenty of need to convincingly dispute their claims, even if they did it to each other, you would have to show where these supposed contradictions are. If you bother actually reading these studies such as the one hop linked about LSST performance, you will see they compare their results to other researchers and explain causes for any differences.

Your arguments are equivalent and just as wrong as the people who doubt that the Earth is getting warmer, and use arguments such as "two scientists using different models didn't get the exact same answer, therefore their models are worthless and wrong so the opposite of what they say must be true and the Earth is cooling" ignoring that the data all agrees that the Earth is warming, and the differences are part of the known uncertainty, which isn't large enough to change the result that the Earth is warming.

In citing "experts" working nuclear deterrence, including lectures of remedial information, none acknowledge the impossible distance, impossibly high number of warheads required or any means to implement. They're of no practical, actionable use - only speculative theory to support minimally effective actions.
These aren't the people responsible for designing rockets, and there are others out there working on building bigger, better rockets. Their studies are necessary of course for figuring out whether we have a big enough rocket for a given deflection mission.

The practice of science has advance significantly since Copernicus.
Unfortunately the intellectual integrity of those that follow science, and seem to enjoy citing others' work, apparently has not. If you understood the topic, not just recite it, you'd question your assertions as well.
If YOU understood the topic, you wouldn't question their work unless you had something specific to question about it.

Offline Propylox

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Re: Deflecting or destroying dangerous asteroids
« Reply #47 on: 07/28/2017 06:13 AM »
Do you have specific calculations showing that the overall risk from 20-30m asteroids is significant compared to that posed by 140+ meter bodies? ... What size range would this 20m space telescope completeness >90% for, and how did you arrive that conclusion? How much is overall risk reduced by completing the survey in a "a couple years" rather than decades? ... Again, is this based on specific models or calculations? ... Which specific scenarios in Bruck Syal et al paper linked above require "impossible" distance or warhead numbers? What models or calculation did you use to come to the conclusion that these scenarios are "impossible"?
You've taken the position, reasoning and arguments of a parliamentarian or statistician, not a scientist.

Such studies, assumptions and calculations are like those done for LOM/LOC, none of which can tell you if things will go wrong tomorrow, the next three times or how - or if the actions taken are even necessary. But while LOM/LOC improves robustness and identifies weaknesses, all the studies you pursue accomplish nothing but keeping people busy and patting each other on the back like saying "We reached an agreement to form a committee to have an accord."
Moreover, "completeness" under 100% isn't complete and even if it was, wouldn't actually be complete just like "risk reduction" doesn't actually reduce the risk of a city or planet being anhiliated. These are meaningless statistics used by people who don't understand the problem, but like to justify their participation. If you actually understood the science and risks, you wouldn't reason like a parliamentarian and offer statistical studies as proof. You'd actually recognize their misrepresentation of truth.

So now you are reduced to disputing the credentials of the people who study this for a living. ... Your arguments are equivalent and just as wrong as the people who doubt that the Earth is getting warmer ... If YOU understood the topic, you wouldn't question their work unless you had something specific to question about it.
Did I just get called a GW-denier? Stay classy.

If that's your reference, you know there's plenty of "experts", "studies", pundits and marketeers from the "other side" (whichever side YOU stand on) that have no scientific merit. They may have great credentials and spent their lives on the topic, but that doesn't make them right - only the truth can do that. I have not questioned others' credentials, only their conclusions and pointed out credentials don't matter. I'll also point out hop, like other topic pundits, have led you astray with false promises, flawed reasoning, worthless studies and his inability to defend those subject/quotes is proof of his ignorance of it.

First and foremost; all studies to date are without merit as the physical properties of meteors is unknown - specifically their tensile strength, shear strength and elasticity. Shoemaker-Levy 9 disentigrated from tidal forces that are comparatively minor, suggesting anything but compressive forces with containment or minute forces over decades would be disasterous. But making assumptions about how to affect them would be like making environmental or atmospheric predictions without actually knowing the atmosphere's composition. DART will fill some voids current "experts" ignore while making speculative and uneducated theories.

In the complete absence of actionable data, but a wealth of irrelevant glad-handing and statistics, we can realistically only rely on the total vaporization of a meteor as defense. That limits our defense to 100m or less, but the path of parliamentarians and statisticians has concluded we should only focus on larger objects, with fungible "completeness" or "risk reduction" assertions. In truth nothing has been accomplished as no defense -from any size or distance- has been made. Only empty, and foolish promises.
« Last Edit: 07/28/2017 06:20 AM by Propylox »

Offline tyrred

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Re: Deflecting or destroying dangerous asteroids
« Reply #48 on: 07/28/2017 07:14 AM »
So what is your plan to gain 100% certainty, and how will you convince others to fund and field it, if all others have failed?

Offline meberbs

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Re: Deflecting or destroying dangerous asteroids
« Reply #49 on: 07/28/2017 02:27 PM »
So now you are reduced to disputing the credentials of the people who study this for a living. ... Your arguments are equivalent and just as wrong as the people who doubt that the Earth is getting warmer ... If YOU understood the topic, you wouldn't question their work unless you had something specific to question about it.
Did I just get called a GW-denier? Stay classy.
No, I said you are using the exact same kind of horribly wrong anti-science arguments as them.

They may have great credentials and spent their lives on the topic, but that doesn't make them right - only the truth can do that.
It makes them more likely to be right than you, especially when you don't actually point to specific things they say that are wrong.

I have not questioned others' credentials,
Questioning their credentials is exactly what is implied when you put the word expert in quotes.

only their conclusions and pointed out credentials don't matter.
Credentials don't matter? Lets go ask a 5 year old to resolve this for us then.

I'll also point out hop, like other topic pundits, have led you astray with false promises, flawed reasoning, worthless studies and his inability to defend those subject/quotes is proof of his ignorance of it.
You are the only one here doing any of the things you said. There generally has been nothing to defend the quotes because you haven't been providing any specific arguments against them. Your lack of specific arguments against them "is proof of your ignorance of it" (to paraphrase you)

To your credit, you at least attempted specific criticisms in this post even if they take the exact form that I just explained was utterly wrong: Calling an entire field of research worthless due to known uncertainties.

First and foremost; all studies to date are without merit as the physical properties of meteors is unknown - specifically their tensile strength, shear strength and elasticity. Shoemaker-Levy 9 disentigrated from tidal forces that are comparatively minor, suggesting anything but compressive forces with containment or minute forces over decades would be disasterous. But making assumptions about how to affect them would be like making environmental or atmospheric predictions without actually knowing the atmosphere's composition. DART will fill some voids current "experts" ignore while making speculative and uneducated theories.
More evidence you don't read any of the papers, scientists tend to be quite explicit with their assumptions. We do have some data, and that includes that there are a variety of types of asteroids. Even if a study only applies to some of them it is far from worthless.

In the complete absence of actionable data, but a wealth of irrelevant glad-handing and statistics,
Did you just say that statistics aren't data?

we can realistically only rely on the total vaporization of a meteor as defense. That limits our defense to 100m or less,
It is almost certainly pointless to ask, but do you have any calculations or data to back up this assertion? What assumptions did you make?

Obviously one of your assumptions was to ignore options like the gravity tractor.

but the path of parliamentarians and statisticians has concluded we should only focus on larger objects, with fungible "completeness" or "risk reduction" assertions. In truth nothing has been accomplished as no defense -from any size or distance- has been made. Only empty, and foolish promises.
Since the only thing you count as progress is successfully deflecting an asteroid, we should give up all searches for asteroids and research into deflection methods right now, because none of them are producing progress. Then if we somehow notice something on a collision course anyway, we can send a last minute thrown together mission and cross our fingers.

Or maybe you might want to reconsider using absolute words such as "nothing."

Edit: mis-placed quote tag and minor typos
« Last Edit: 07/28/2017 04:55 PM by meberbs »

Offline hop

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Re: Deflecting or destroying dangerous asteroids
« Reply #50 on: 07/28/2017 04:50 PM »
That limits our defense to 100m or less, but the path of parliamentarians and statisticians has concluded we should only focus on larger objects, with fungible "completeness" or "risk reduction" assertions. In truth nothing has been accomplished as no defense -from any size or distance- has been made. Only empty, and foolish promises.
So, all the specific assertions you made earlier were not based on any specific calculations or model? Yet somehow, you are certain that 20 m space telescopes are required, and that standoff nukes are "useless", and that diverting >100 m asteroids is "impossible"

If you haven't done any calculation or experiment, why do you believe these specific things are true? Why should we believe your assertions over people who spent decades at NASA and national labs working on this stuff in a rigorous manner?

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Moreover, "completeness" under 100% isn't complete and even if it was, wouldn't actually be complete just like "risk reduction" doesn't actually reduce the risk of a city or planet being anhiliated. These are meaningless statistics used by people who don't understand the problem, but like to justify their participation.
This is just total innumeracy. Statistics are a fundamental and extremely successful part of science, and impact risk is based on quite simple statistics. If you have to cross a mine field, and have a choice of knowing where ~90% of the mines are, or not knowing where any are, which do you chose?
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First and foremost; all studies to date are without merit as the physical properties of meteors is unknown
This is just totally, obviously incorrect: We have in-situ data for multiple asteroids and comets, surface data from Rosetta and Hayabusa (soon to be joined by OSIRIS-Rex and Hayabusa 2) and impact data from Deep Impact. We have observations of many hundreds of thousands of asteroids, and many of these provide significant insight into their structure and physical properties. We also have literally tons of asteroid material from meteorites, and observation of thousands of objects entering the atmosphere.

Physical properties are a significant source of uncertainty, but to say we know nothing just shows total ignorance of the field. The data we have puts significant constraints on the range of properties we are likely to encounter.

Offline hop

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Re: Deflecting or destroying dangerous asteroids
« Reply #51 on: 07/29/2017 02:12 AM »
Nukes are insufficient.
In what way are nukes insufficient? The big problems are political: Pretty much everyone would probably be OK with nukes if a major catastrophe was imminent, but you'd really like to do some tests before you need them, and that opens up a big cans of worms. Even laying the groundwork to have them ready could get very touchy.

There are cases where you wouldn't get enough warning to effectively use nukes, but other methods generally require even more warning, so that's not really a problem with nukes specifically.
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So if a nuclear mass generator was a viable / non-fictional concept,
It's not, at least not any anything above atomic scales. Any civilization that could produce significant macroscopic mass from energy would have plenty of ways to divert asteroids.

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I'd guess that would be more practical than the above two concepts (nukes & tethers).
I'm not aware of tethers being a serious deflection option. There have been some suggestion of "harpooning" passing comets / asteroids as a way of saving fuel (e.g. https://www.space.com/30451-nasa-comet-hitchhiker-concept-mission.html), but it's a pretty far out concept that is far from being available in the real world.

Kinetic impactors and various slow push methods like gravity tractors tend be the most common alternatives to nukes. The 2007 report to congress has a good overview https://cneos.jpl.nasa.gov/doc/neo_report2007.html  (although of course a lot of work has been done since, and many of the dates have slipped)

Offline Hog

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Re: Deflecting or destroying dangerous asteroids
« Reply #52 on: 07/29/2017 11:31 AM »
What size of fission fission/fusion device would be need?
Would the current less than 1mT devices be sufficient, or would we need to revisit some 9-15mT weapons of the past?

I can see the difficulty in testing for such devices, or even attempting to procure the materials and engineer the actual nuclear portion of the device.
Paul

Offline Propylox

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Re: Deflecting or destroying dangerous asteroids
« Reply #53 on: 07/29/2017 12:24 PM »
We have observations of many hundreds of thousands of asteroids, and many of these provide significant insight into their structure and physical properties. ... Physical properties are a significant source of uncertainty, but to say we know nothing just shows total ignorance of the field.
No, you really don't know anything. Six months ago the 40-90m asteroid "2017 BS5" was discovered in an orbit nearly identical to Earth's and flew past last weekend. This is an obvious orbit to detect, like a dim star following the Earth, and yet it wasn't detected until the point no redirection theories could have avoided a possible collision, only total vaporization of the object at the last minute. Fortunately it missed.
Thankfully pundits and "the field of experts" who focus on "risk reduction and completion" have enough "studies" of the physical properties to handle this, right?
Dr. John S. Lewis - "Until we know what the body is made of, hazard projections are nonsense. It could be a dustball, a snowball, a loose collection of rocky rubble, a monolithic soft rock, a monolithic hard rock, a giant steel cannonball, et cetera. It could, at the extremes, fall apart into dust at high altitudes or penetrate hundreds of meters into Earth’s crust and explode like World War III." http://deepspaceindustries.com/asteroid-profile-2017-bs5/

Since the only thing you count as progress is successfully deflecting an asteroid, we should give up all searches for asteroids and research into deflection methods right now, because none of them are producing progress.
Actually I said we should focus on finding asteroids/meteors we can currently stop (100m down to 20m equivalent to ICBMs) that can cause massive destruction, while awaiting data (DART) to inform us on the properties of asteroids instead of wildly speculating on what to do, how effective it would be, calling it "expertise" and trying to con Congress into funding it. Notably, finding 20m meteors means we found the 20mi ones as well and provides more future options to test redirect concepts.

Statistics are a fundamental and extremely successful part of science, and impact risk is based on quite simple statistics. If you have to cross a mine field, and have a choice of knowing where ~90% of the mines are, or not knowing where any are, which do you chose?
I wouldn't cross the minefield, duh. I also wouldn't play Russian roulette or buy into a "~90% completion in ten years" scheme. I'd actually try to identify all the hazards, find out their properties and remove the threat rather than waltzing through with my fingers crossed, waiving a study and professing expertise.

Credentials don't matter? Lets go ask a 5 year old to resolve this for us then.
and Did you just say that statistics aren't data?
If someone's entirely wrong and peddling myths, credentials only show who was foolish enough to give them credentials. If a 5yr old had credentials, does that make them right? And no, statistics aren't real data. Observed, recorded information is valuable, but not after it's gone through a blender with ample assumptions, categorization and reconfigurations to become stats, marketing or whatever you want it to be.
« Last Edit: 07/29/2017 03:32 PM by Propylox »

Offline Propylox

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Re: Deflecting or destroying dangerous asteroids
« Reply #54 on: 07/29/2017 03:27 PM »
Might be a change in direction with the conversation (don't let me interrupt).

... Obviously a desirable amount of mass would need to be generated.  So if a nuclear mass generator was a viable / non-fictional concept, I'd guess that would be more practical than the above two concepts (nukes & tethers). ...
Please, interrupt  ;)
Frankly if enough energy to marginally alter mass could be delivered to an asteroid, you'd turn it into a cloud of plasma. At far less levels of energy you could magnetize it enough to be affected by solar wind. At even less energy, you could constantly vaporize the surface, even of a rotating body, to create directional thrust.
« Last Edit: 07/29/2017 03:33 PM by Propylox »

Offline as58

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Re: Deflecting or destroying dangerous asteroids
« Reply #55 on: 07/29/2017 03:39 PM »
Actually I said we should focus on finding asteroids/meteors we can currently stop (100m down to 20m equivalent to ICBMs) that can cause massive destruction, while awaiting data (DART) to inform us on the properties of asteroids instead of wildly speculating on
what to do, how effective it would be, calling it "expertise" and trying to con Congress into funding it. Notably, finding 20m meteors means we found the 20mi ones as well and provides more future options to test redirect concepts.

Why? Studies (and history) show that risk of lives lost due to ~20m meteors is very low, while detecting them is extremely difficult (=expensive). If one is spending money to save lives and property, concentrating on finding small asteroids/meteors makes very little sense from cost/benefit point of view.

Offline Propylox

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Re: Deflecting or destroying dangerous asteroids
« Reply #56 on: 07/29/2017 04:03 PM »
If one is spending money to save lives and property, concentrating on finding small asteroids/meteors makes very little sense from cost/benefit point of view.
Why, when small asteroids are the only ones we can stop? Programs to find large meteors have no benefit as we have no actions against them. And the cost of finding small asteroids is almost no different than finding large ones if the cost of scaling up a telescope is minimal. Previously I mentioned telescopes haven't advanced in 350years - the date when reflection replaced refraction in large scopes. Sure, we've managed to ease production and reduce weight by combining multiple mirrors into a larger primary and surface-coat rather than back-coat the mirrors, but that's embarrassingly minor for 31/2 centuries.

Building better telescopes is something everyone can get on board with. From asteroids, to the Solar system and deep space - even downlookers want better scopes. That's the squeaky wheel which actually benefits mankind and identifies smaller, more numerous asteroids to test redirect methods on in the future.
« Last Edit: 07/29/2017 04:15 PM by Propylox »

Offline RonM

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Re: Deflecting or destroying dangerous asteroids
« Reply #57 on: 07/29/2017 04:24 PM »
If one is spending money to save lives and property, concentrating on finding small asteroids/meteors makes very little sense from cost/benefit point of view.
Why, when small asteroids are the only ones we can stop? Programs to find large meteors have no benefit as we have no actions against them. And the cost of finding small asteroids is almost no different than finding large ones if the cost of scaling up a telescope is minimal. Previously I mentioned telescopes haven't advanced in 350years - the date when reflection replaced refraction in large scopes. Sure, we've managed to ease production and reduce weight by combining multiple mirrors into a larger primary and surface-coat rather than back-coat the mirrors, but that's embarrassingly minor for 31/2 centuries.

Building better telescopes is something everyone can get on board with. From asteroids, to the Solar system and deep space - even downlookers want better scopes. That's the squeaky wheel which actually benefits mankind and provides smaller, more numerous options to test redirect methods in the future.

We don't have to "stop" asteroids. A slight change in course will cause them to miss hitting the Earth. The earlier they are detected, the better because it will take less of a push. Even very large asteroids can be deflected with a few years advanced warning.

Since you believe telescope technology hasn't advanced in 350 years, you obviously don't know what you're talking about.

Asteroid survey telescopes don't need to large, but it would help if they were in space. Orbital wide field of view IR telescopes are needed.

Offline as58

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Re: Deflecting or destroying dangerous asteroids
« Reply #58 on: 07/29/2017 04:32 PM »
If one is spending money to save lives and property, concentrating on finding small asteroids/meteors makes very little sense from cost/benefit point of view.
Why, when small asteroids are the only ones we can stop? Programs to find large meteors have no benefit as we have no actions against them. And the cost of finding small asteroids is almost no different than finding large ones if the cost of scaling up a telescope is minimal. Previously I mentioned telescopes haven't advanced in 350years - the date when reflection replaced refraction in large scopes. Sure, we've managed to ease production and reduce weight by combining multiple mirrors into a larger primary and surface-coat rather than back-coat the mirrors, but that's embarrassingly minor for 31/2 centuries.

Building better telescopes is something everyone can get on board with. From asteroids, to the Solar system and deep space - even downlookers want better scopes. That's the squeaky wheel which actually benefits mankind and provides greater options to test redirect methods in the future.

Just because we can (with great expense) deflect ~20 m asteroids doesn't necessarily mean that trying to detect all of them is a worthwhile goal. I believe a much better cost/benefit would come from almost any much more down-to-earth investment in public safety.

Saying that telescopes haven't advanced in 350 years needs some strange definition of what counts as a (significant) advancement. But I'm not sure what kind of development you are hoping to happen. There are laws of physics to contend with and only in New Physics section can wishful thinking overcome them. Or perhaps your posts are a prelude to a sales pitch for large-scale diffractive lenses?

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Re: Deflecting or destroying dangerous asteroids
« Reply #59 on: 07/29/2017 06:11 PM »
We have observations of many hundreds of thousands of asteroids, and many of these provide significant insight into their structure and physical properties. ... Physical properties are a significant source of uncertainty, but to say we know nothing just shows total ignorance of the field.
No, you really don't know anything. Six months ago the 40-90m asteroid "2017 BS5" was discovered in an orbit nearly identical to Earth's and flew past last weekend. This is an obvious orbit to detect, like a dim star following the Earth, and yet it wasn't detected until the point no redirection theories could have avoided a possible collision, only total vaporization of the object at the last minute. Fortunately it missed.
Thankfully pundits and "the field of experts" who focus on "risk reduction and completion" have enough "studies" of the physical properties to handle this, right?
Dr. John S. Lewis - "Until we know what the body is made of, hazard projections are nonsense. It could be a dustball, a snowball, a loose collection of rocky rubble, a monolithic soft rock, a monolithic hard rock, a giant steel cannonball, et cetera. It could, at the extremes, fall apart into dust at high altitudes or penetrate hundreds of meters into Earth’s crust and explode like World War III." http://deepspaceindustries.com/asteroid-profile-2017-bs5/

Since the only thing you count as progress is successfully deflecting an asteroid, we should give up all searches for asteroids and research into deflection methods right now, because none of them are producing progress.
Actually I said we should focus on finding asteroids/meteors we can currently stop (100m down to 20m equivalent to ICBMs) that can cause massive destruction, while awaiting data (DART) to inform us on the properties of asteroids instead of wildly speculating on what to do, how effective it would be, calling it "expertise" and trying to con Congress into funding it. Notably, finding 20m meteors means we found the 20mi ones as well and provides more future options to test redirect concepts.

Statistics are a fundamental and extremely successful part of science, and impact risk is based on quite simple statistics. If you have to cross a mine field, and have a choice of knowing where ~90% of the mines are, or not knowing where any are, which do you chose?
I wouldn't cross the minefield, duh. I also wouldn't play Russian roulette or buy into a "~90% completion in ten years" scheme. I'd actually try to identify all the hazards, find out their properties and remove the threat rather than waltzing through with my fingers crossed, waiving a study and professing expertise.

Credentials don't matter? Lets go ask a 5 year old to resolve this for us then.
and Did you just say that statistics aren't data?
If someone's entirely wrong and peddling myths, credentials only show who was foolish enough to give them credentials. If a 5yr old had credentials, does that make them right? And no, statistics aren't real data. Observed, recorded information is valuable, but not after it's gone through a blender with ample assumptions, categorization and reconfigurations to become stats, marketing or whatever you want it to be.

One quote you missed from that very same article... says we can determine the composition of an asteroid.

"JSL: There are, as yet, no useful data to characterize what 2017 BS5 is made of. The close fly-by this weekend will give Earth-based astronomers a great opportunity to get a good spectrum and tell us what class of meteorite it is most closely related to, what the dominant minerals are, and what economic value it might have."

Nobody in this thread would ever say that we should stop looking for asteroids. Long lead-times are essential for a deflection attempt. Where you go wrong is your claim that we can't deflect any unless they are ~100 meters in diameter or smaller.

Do you have any sources you can cite that shows the people who have done asteroid deflection studies are "entirely wrong and peddling myths"?
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

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