Killer Asteroids

  • #1

Main Question or Discussion Point

As far as avoiding a killer asteroid in the future, I have what I consider to be a simple solution. Japan has already demonstrated the technology of landing a spacecraft on an asteroid, so what could be more simple than to land on an asteroid, rotate the landing engine 180 degrees, fire it up and literally push the asteroid into another trajectory? We could strategically post these craft orbiting the moon, Mars, etc. for immediate deployment. Nuclear power for straight-line travel and chemical fuel for rocket control.
It's true I probably don't know what I'm talking about, bringing my high school education to bear. But, it sure sounds like the solution to me.
 

Answers and Replies

  • #2
mathman
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The major problem is time constraint. From the time a killer asteroid is discovered, is there enough time to do what is needed to change its trajectory?
 
  • #3
Chronos
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The problem with asteroids is one of ambush. If it is detected only days before impact, that is a big problem. We do not have launch ready anti-asteroid kits sitting around. It has been estimated we would need to detect a collision bound asteroid at least 6 months prior to impact to mount a realistic defense. Even then, the efficacy of such defensive ideas is untested. The priority at present is detecting all the disaster size asteroids in our vicinity, which is surprisingly difficult for a number of reasons. At present, it is thought we have catalogued only 10-15% of them.
 
  • #4
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I'm actually working on a system right now. I've got a website setup, still trying to iron out all the details. The later phases of the project are a little 'out there' but the initial phases are most certainly doable right now. www.tregsproject.com [Broken] is my website. If you'd like to assist me in hashing out the details, maybe we can make this as a legitimate proposal to NASA or some other entity who would like to see this come to light.
 
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  • #5
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Gaia can do all of this. To detect asteroids, it is not necessary to go far away from earth. You might be lucky and get closer to some asteroid by a factor of 2 - but you need much more time and more fuel (-> less useful payload) to send probes to other planets.

Building a new satellite is cheaper than repairing one in some remote location.
You don't need a grid of satellites, a few relay station around frequently visited objects will do the job.

The priority at present is detecting all the disaster size asteroids in our vicinity, which is surprisingly difficult for a number of reasons. At present, it is thought we have catalogued only 10-15% of them.
That depends on their size. For objects with a diameter of more than 1km close to our orbit, it is expected that most of them (80%? 90%? Don't remember) are known. Those are the global killers - an asteroid with a diameter of 100m can destroy a city, but it won't end our civilization.
 
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  • #6
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Gaia can do all of this. To detect asteroids, it is not necessary to go far away from earth. You might be lucky and get closer to some asteroid by a factor of 2 - but you need much more time and more fuel (-> less useful payload) to send probes to other planets.

Building a new satellite is cheaper than repairing one in some remote location.
You don't need a grid of satellites, a few relay station around frequently visited objects will do the job.
This is quite interesting, and I admit I'd never heard of gaia before now. It's interesting how it works. I could see that doing a fair job, but the problem still remains it's too difficult to see an incoming asteroid due to how dark it is until the very last moment. We have no early detection system.

My view of our stance on space and science is that it's very mediocre. I would like to see mankind ACTIVELY in space. I mean full gear, massive space stations capable of housing several thousand people, space ships capable of traveling between these stations, from there missions to various planets and moons. But none of this is capable without the ability to detect and prevent these stations from being struck by space objects like meteors and asteroids. I kind of feel like it's going to be impossible to get mankind into space like that without the foundation of protection, and that nearly requires an early detection system. I don't think even the Gaia project can settle that. Fact is, asteroids and meteors are nearly undetectable at long distances and by the time we do detect them it's far too late. I would love to see what the Gaia satellite can do, but I don't think it's a suitable detection system to map out the entire solar system in real time for an accurate and effective early detection system.
 
  • #7
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This is quite interesting, and I admit I'd never heard of gaia before now. It's interesting how it works. I could see that doing a fair job, but the problem still remains it's too difficult to see an incoming asteroid due to how dark it is until the very last moment. We have no early detection system.
If the ability to detect asteroids with a size of 200m basically everywhere in the inner solar system is not an early detection system, what is one?

My view of our stance on space and science is that it's very mediocre. I would like to see mankind ACTIVELY in space. I mean full gear, massive space stations capable of housing several thousand people, space ships capable of traveling between these stations, from there missions to various planets and moons. But none of this is capable without the ability to detect and prevent these stations from being struck by space objects like meteors and asteroids.
There are many challenges for such a vision, detectable asteroids are a small issue in that respect.
 
  • #8
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If the ability to detect asteroids with a size of 200m basically everywhere in the inner solar system is not an early detection system, what is one?
The fact that the project has a 5 year life span, only points in a specific direction and can only detect in that direction, means that this is not an early detection system at all. An early detection system would be real-time, would not be ended, and would be able to see in all directions all the time.

There are many challenges for such a vision, detectable asteroids are a small issue in that respect.
This is why I created my other thread "Occupying Space", for that discussion.
 
  • #9
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The fact that the project has a 5 year life span, only points in a specific direction and can only detect in that direction, means that this is not an early detection system at all. An early detection system would be real-time, would not be ended, and would be able to see in all directions all the time.
Gaia does not point in a specific direction, it rotates.
Asteroids don't magically appear in the solar system*. With observation arcs of 5 years, you can calculate their future position at least several decades in advance, and you know when the predictions will lose their accuracy. You don't have to look at them all the time.

*comets do that in some way, but they are rare. And Gaia is certainly not the last telescope...
 
  • #10
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I suppose that is true. I think the only problem with that theory are the asteroids that enter the solar system that are not part of the Oort Cloud. I would imagine that something like that is not entirely unfeasible, and in that case I would assume we would want to continue the project on going. I didn't realize it rotated though, which is a good measure. I suppose my thought process is that there should be ongoing 360 degree observation from space for a very long time, not just to map things out, but to catch things as they happen. i can imagine we've missed multiple events in space out and about just because our telescopes weren't pointed in that direction.
 
  • #11
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There are networks to catch rare events like gamma ray bursts or nearby supernovae.
 
  • #12
Chronos
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The number of NEO's is pretty uncertain. NASA, for example, claims about 90% of NEO's 1 km or larger have been catalogued - which is a somewhat comforting number. LSST, on the other hand, estimates less that 20% of such objects have been catalogued (re: http://www.lsst.org/lsst/public/neoquant [Broken]), which is much less comforting. I tend to lean to the pessimistic side. Many asteroids have low albedos making detection difficult to nearly impossible. Rogue asteroids are another unknown. They can, and are randomly flung our direction from the far reaches of the solar system. The potential consequences are so great some sort of early warning system is a luxury we really can't afford not to indulge, IMO.
 
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  • #13
phinds
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I would like to see mankind ACTIVELY in space. I mean full gear, massive space stations capable of housing several thousand people, space ships capable of traveling between these stations, from there missions to various planets and moons.
Wow ... I'd like to have some of what you're smoking if you think that's even remotely likely any time soon. The technical challenges are non-trivial, BUT ... they ARE trivial compared to the economic/political problems. Who do you think would pay for all that?
 
  • #14
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Chronos, I would have to agree. NASA didn't even know about the 7 football field large asteroid that nearly hit the earth, and it wasn't even reported on until nearly a month later. This is simply unacceptable, but with the current setup we have, it's the best we can do. That's why I put the T.R.E.G.S. System out there, to be discussed and hopefully if the countries of the world would put their minds together, could accomplish it. I'm still putting the website together, but you can take a look at www.tregsproject.com [Broken]. I just got done with some simple mathematical calculations and have been able to make some determinations on about how big this project would have to be. What do you think?
 
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  • #15
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Wow ... I'd like to have some of what you're smoking
You can kindly squash that kind of insult, thank you.

... if you think that's even remotely likely any time soon. The technical challenges are non-trivial, BUT ... they ARE trivial compared to the economic/political problems. Who do you think would pay for all that?
I refer you to my other thread I started for this conversation: https://www.physicsforums.com/showthread.php?t=718173
 
  • #16
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I just got done with some simple mathematical calculations and have been able to make some determinations on about how big this project would have to be. What do you think?
I don't see that on the website.

Chronos said:
NASA, for example, claims about 90% of NEO's 1 km or larger have been catalogued - which is a somewhat comforting number. LSST, on the other hand, estimates less that 20% of such objects have been catalogued
Well, searches are getting better and better, but the number of new discoveries in the category km+ decreases, while the number of discoveries for smaller asteroids goes up - a good indication that we discovered most big objects that do not hide somewhere far away most of the time. I expect significant improvements from Gaia here - it is supposed to (at least) double the number of known objects in the solar system.
 
  • #17
phinds
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You can kindly squash that kind of insult, thank you.
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I see that rather than address my criticism, you are attempting to deflect it by objecting to my wording. So back to the question --- who DO you think would pay for all that stuff you mentioned?
 
  • #18
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I haven't put the math on the website yet.

phinds, I responded to your question in two parts. The first part was to address your insult. The second was a link where I have already answered your question. feel free to carry that conversation on in a thread that directly addresses it.
 
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  • #19
phinds
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The second was a link where I have already answered your question.
No, that thread does not even begin to answer my question. You have no proposal that is in any way realistic as to how all that would be paid for.
 
  • #20
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Why does that even concern you? If someone comes up with the money it will happen, if not it won't. I didn't address it because I don't limit human advancement by how much money I have in my pocket. I don't have a specific way of how or who will fund this, and it's no one's concern right now. I'll look for sponsoring support once the project is laid out and we can get a price guesstimate, which is how all large projects work. Does that answer your question?
 
  • #21
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I don't see that on the website.
I've added this post to the website with the math I was talking about. It's available for all viewers to look at it and comment.

http://tregsproject.com/?p=52 [Broken]
 
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  • #22
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This is a serious possibility for some asteroids, however, others are too large to even consider chemical rockets unless an entire volatiles-mining facility is built on the killer asteroid.
For example, assuming an effective exhaust velocity of 4,400 m/s, commonplace for bi-propellant rockets, altering the velocity by just 1 mm/s, (likely not enough except with a lot of early warning) requires a rocket with a fuel mass of 1/4400000 times the mass of the asteroid itself.
If, for example, the asteroid is a block of with a density of 4000 kg/m^3, and a side-length of 1000 meters, then it would already mass in at 4 Gigatonnes, and require a 1 Kilotonne rocket to propel it. This is similar to putting a Saturn V on said asteroid. Of course, then there is the expense and difficulty of getting an entire Saturn V into a solar orbit.
 
  • #23
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altering the velocity by just 1 mm/s, (likely not enough except with a lot of early warning)
This is easy to estimate for near-earth objects, as the velocity change is small the effect of the modified orbit is negligible (unless the asteroid performs a fly-by at some other object). If the relative velocity between asteroid and earth is large compared to the escape velocity (11km/s), the earth is just like a round disk as target. The maximal deflection needed is then just the radius, 6370km. If the asteroid is slow, it can need more deflection, but at the same time not every hit is perfectly central, so a required deflection of 1 earth radius is a good estimate. If we change the course 1 year before the possible impact, this gives a velocity change of 20cm/s. If we just get 1mm/s, we need a lot of warning time (or an initial orbit very close to a miss).

Velocity changes in flight direction close to the sun are more effective (Oberth effect), and far away from the sun all changes are more effective compared to projects close to our orbit.
 
  • #24
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If we change the course 1 year before the possible impact, this gives a velocity change of 20cm/s.
Exactly, so instead of one Saturn V, we need to figure out a way to launch 200 Saturn Vs and land them all with fuel still there on the Asteroid.

Makes this even less feasible.

Of course, there is always the nuclear option, if you vaporize part of the asteroid, the gas expelled kicks the rest of it back. In this case, the goal would be to maximize volume of material expelled to maximize the momentum change.
 
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  • #25
D H
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For example, assuming an effective exhaust velocity of 4,400 m/s, commonplace for bi-propellant rockets, altering the velocity by just 1 mm/s, (likely not enough except with a lot of early warning) requires a rocket with a fuel mass of 1/4400000 times the mass of the asteroid itself.
You don't need a 1 mm/s Δv if the asteroid is known to be on a collision course decades in advance. Given enough time, all that's needed is a micrometer/second change in velocity. That's a lot better than our current asteroid deflection capability, which is of course zilch. There are lots of plans, some feasible, others not. The plans that are feasible necessarily take technological and budgetary limitations into account.

The kilometer diameter snowball that we first detect six months prior to impact? There's no reason to address this extremely low probability event right now because if this happens we are toast. It's a philosophy of going after the low-hanging fruit. Since our current capabilities are non-existent, there's lots of low hanging fruit to be plucked.
 

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