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What is our planetary defense capability against an Earth destroying object?
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This is World Building through a preventative measure.
The Earth has been destroyed a few times in the past and it will happen again in the future, it is just a matter of time. For the first time in history we have the capability to save ourselves if we work together.
What is our current capability when it comes to protecting Earth from a rogue moon, comet or asteroid? Hale Bopp comet is 500 million km from the nucleus. I understand after a certain size there is nothing you could do, right?
Meanwhile on the opposite side of the Earth.
What are the possibilities with current technology if money was no object? Any new realistic answers welcome even if it is your own. You may have the idea that saves the world.
science-based asteroids self-defense
edited 19 mins ago
a4android
30.6k340120
asked 5 hours ago
Muze
6731727
 |Â
show 12 more comments
up vote
2
down vote
favorite
This is World Building through a preventative measure.
The Earth has been destroyed a few times in the past and it will happen again in the future, it is just a matter of time. For the first time in history we have the capability to save ourselves if we work together.
What is our current capability when it comes to protecting Earth from a rogue moon, comet or asteroid? Hale Bopp comet is 500 million km from the nucleus. I understand after a certain size there is nothing you could do, right?
Meanwhile on the opposite side of the Earth.
What are the possibilities with current technology if money was no object? Any new realistic answers welcome even if it is your own. You may have the idea that saves the world.
science-based asteroids self-defense
edited 19 mins ago
a4android
30.6k340120
asked 5 hours ago
Muze
6731727
1
Moon-sized isn't a comet, it's a planet. To give an idea of how large comets are, here's a list of comets that are easy for us to observe: en.wikipedia.org/wiki/List_of_periodic_comets -- As the question is now, if a moon-sized object were going to hit the Earth, all life as we know it will most definitely end.
– Ghedipunk
5 hours ago
It really depends on when we see it. If it's far out, even a tiny nudge can make it miss entirely, and my "knows some things" mind says that if money weren't an object, it would be "Fairly easy" (Although highly complex and extremely expensive) to do. If we see it really close? Well, we wouldn't have time to build the stuff necessary, let alone get the mission going and doing it. As @Ghedipunk says, though, a moon-type object would simply to large. Comet or asteroid? Far more likely. Density (Actually: Mass) matters more than size here.
– Andon
5 hours ago
1
@Andon But if it is far out, we will probably have not enough precision to determine if it is going to hit us, and thus we will not know if giving it a nudge will put it in collision path. Also, I think you are overestimating the payload we can put "far out"; the nudge will be not tiny but "very tiny".
– SJuan76
5 hours ago
3
@Andon Coins would be far more efficient.
– Cadence
5 hours ago
1
@Muze I was referring to us as the people commenting. As in, I, personally, don't have the knowledge or information to back up my claims. There ARE people on Worldbuilding that do, they're just not me. I'm sure they'll be around eventually.
– Andon
5 hours ago
 |Â
show 12 more comments
up vote
2
down vote
favorite
up vote
2
down vote
favorite
This is World Building through a preventative measure.
The Earth has been destroyed a few times in the past and it will happen again in the future, it is just a matter of time. For the first time in history we have the capability to save ourselves if we work together.
What is our current capability when it comes to protecting Earth from a rogue moon, comet or asteroid? Hale Bopp comet is 500 million km from the nucleus. I understand after a certain size there is nothing you could do, right?
Meanwhile on the opposite side of the Earth.
What are the possibilities with current technology if money was no object? Any new realistic answers welcome even if it is your own. You may have the idea that saves the world.
science-based asteroids self-defense
edited 19 mins ago
a4android
30.6k340120
asked 5 hours ago
Muze
6731727
This is World Building through a preventative measure.
The Earth has been destroyed a few times in the past and it will happen again in the future, it is just a matter of time. For the first time in history we have the capability to save ourselves if we work together.
What is our current capability when it comes to protecting Earth from a rogue moon, comet or asteroid? Hale Bopp comet is 500 million km from the nucleus. I understand after a certain size there is nothing you could do, right?
Meanwhile on the opposite side of the Earth.
What are the possibilities with current technology if money was no object? Any new realistic answers welcome even if it is your own. You may have the idea that saves the world.
science-based asteroids self-defense
science-based asteroids self-defense
edited 19 mins ago
a4android
30.6k340120
asked 5 hours ago
Muze
6731727
edited 19 mins ago
a4android
30.6k340120
asked 5 hours ago
Muze
6731727
edited 19 mins ago
a4android
30.6k340120
edited 19 mins ago
a4android
30.6k340120
edited 19 mins ago
a4android
30.6k340120
30.6k340120
asked 5 hours ago
Muze
6731727
asked 5 hours ago
Muze
6731727
asked 5 hours ago
Muze
6731727
6731727
1
Moon-sized isn't a comet, it's a planet. To give an idea of how large comets are, here's a list of comets that are easy for us to observe: en.wikipedia.org/wiki/List_of_periodic_comets -- As the question is now, if a moon-sized object were going to hit the Earth, all life as we know it will most definitely end.
– Ghedipunk
5 hours ago
It really depends on when we see it. If it's far out, even a tiny nudge can make it miss entirely, and my "knows some things" mind says that if money weren't an object, it would be "Fairly easy" (Although highly complex and extremely expensive) to do. If we see it really close? Well, we wouldn't have time to build the stuff necessary, let alone get the mission going and doing it. As @Ghedipunk says, though, a moon-type object would simply to large. Comet or asteroid? Far more likely. Density (Actually: Mass) matters more than size here.
– Andon
5 hours ago
1
@Andon But if it is far out, we will probably have not enough precision to determine if it is going to hit us, and thus we will not know if giving it a nudge will put it in collision path. Also, I think you are overestimating the payload we can put "far out"; the nudge will be not tiny but "very tiny".
– SJuan76
5 hours ago
3
@Andon Coins would be far more efficient.
– Cadence
5 hours ago
1
@Muze I was referring to us as the people commenting. As in, I, personally, don't have the knowledge or information to back up my claims. There ARE people on Worldbuilding that do, they're just not me. I'm sure they'll be around eventually.
– Andon
5 hours ago
 |Â
show 12 more comments
1
Moon-sized isn't a comet, it's a planet. To give an idea of how large comets are, here's a list of comets that are easy for us to observe: en.wikipedia.org/wiki/List_of_periodic_comets -- As the question is now, if a moon-sized object were going to hit the Earth, all life as we know it will most definitely end.
– Ghedipunk
5 hours ago
It really depends on when we see it. If it's far out, even a tiny nudge can make it miss entirely, and my "knows some things" mind says that if money weren't an object, it would be "Fairly easy" (Although highly complex and extremely expensive) to do. If we see it really close? Well, we wouldn't have time to build the stuff necessary, let alone get the mission going and doing it. As @Ghedipunk says, though, a moon-type object would simply to large. Comet or asteroid? Far more likely. Density (Actually: Mass) matters more than size here.
– Andon
5 hours ago
1
@Andon But if it is far out, we will probably have not enough precision to determine if it is going to hit us, and thus we will not know if giving it a nudge will put it in collision path. Also, I think you are overestimating the payload we can put "far out"; the nudge will be not tiny but "very tiny".
– SJuan76
5 hours ago
3
@Andon Coins would be far more efficient.
– Cadence
5 hours ago
1
@Muze I was referring to us as the people commenting. As in, I, personally, don't have the knowledge or information to back up my claims. There ARE people on Worldbuilding that do, they're just not me. I'm sure they'll be around eventually.
– Andon
5 hours ago
1
1
Moon-sized isn't a comet, it's a planet. To give an idea of how large comets are, here's a list of comets that are easy for us to observe: en.wikipedia.org/wiki/List_of_periodic_comets -- As the question is now, if a moon-sized object were going to hit the Earth, all life as we know it will most definitely end.
– Ghedipunk
5 hours ago
Moon-sized isn't a comet, it's a planet. To give an idea of how large comets are, here's a list of comets that are easy for us to observe: en.wikipedia.org/wiki/List_of_periodic_comets -- As the question is now, if a moon-sized object were going to hit the Earth, all life as we know it will most definitely end.
– Ghedipunk
5 hours ago
It really depends on when we see it. If it's far out, even a tiny nudge can make it miss entirely, and my "knows some things" mind says that if money weren't an object, it would be "Fairly easy" (Although highly complex and extremely expensive) to do. If we see it really close? Well, we wouldn't have time to build the stuff necessary, let alone get the mission going and doing it. As @Ghedipunk says, though, a moon-type object would simply to large. Comet or asteroid? Far more likely. Density (Actually: Mass) matters more than size here.
– Andon
5 hours ago
It really depends on when we see it. If it's far out, even a tiny nudge can make it miss entirely, and my "knows some things" mind says that if money weren't an object, it would be "Fairly easy" (Although highly complex and extremely expensive) to do. If we see it really close? Well, we wouldn't have time to build the stuff necessary, let alone get the mission going and doing it. As @Ghedipunk says, though, a moon-type object would simply to large. Comet or asteroid? Far more likely. Density (Actually: Mass) matters more than size here.
– Andon
5 hours ago
1
1
@Andon But if it is far out, we will probably have not enough precision to determine if it is going to hit us, and thus we will not know if giving it a nudge will put it in collision path. Also, I think you are overestimating the payload we can put "far out"; the nudge will be not tiny but "very tiny".
– SJuan76
5 hours ago
@Andon But if it is far out, we will probably have not enough precision to determine if it is going to hit us, and thus we will not know if giving it a nudge will put it in collision path. Also, I think you are overestimating the payload we can put "far out"; the nudge will be not tiny but "very tiny".
– SJuan76
5 hours ago
3
3
@Andon Coins would be far more efficient.
– Cadence
5 hours ago
@Andon Coins would be far more efficient.
– Cadence
5 hours ago
1
1
@Muze I was referring to us as the people commenting. As in, I, personally, don't have the knowledge or information to back up my claims. There ARE people on Worldbuilding that do, they're just not me. I'm sure they'll be around eventually.
– Andon
5 hours ago
@Muze I was referring to us as the people commenting. As in, I, personally, don't have the knowledge or information to back up my claims. There ARE people on Worldbuilding that do, they're just not me. I'm sure they'll be around eventually.
– Andon
5 hours ago
 |Â
show 12 more comments
3 Answers
3
active
oldest
votes
up vote
6
down vote
Observation and foresight is everything
It all depends on how early you can detect it. This changes drastically the response and the chances of success. Luckily, orbital mechanics is generally well-understood, so if you can detect an object early, you can predict, perhaps even for centuries, if this object is likely to impact the Earth.
Not only does early detection give you more time to respond, it also has the advantage that effort required to move something off a trajectory is much smaller for objects that are a long way away, or take a lot of time to reach us. The slightest nudge would have minimal affect in a short time span, but over a long one would have a much larger effect.
So:
If it is large and decades away from hitting Earth: Even the smallest nudge would alter its trajectory over the years. Acting (relatively) quickly, we can send a probe with a nuclear device to land on it (which we can already do), then detonate it to nudge it.
If it is only a year away from hitting Earth: Depending on the mass to move, you need to increase the yield of your device commensurately
If it is only a few days away: Your chances are becoming minimal you can do anything to prevent the impact, and you may need to settle on survival measures.
In all scenarios the best thing you could do is to detect it as early as possible. This means basically more telescopes calibrated specifically to detect objects that may be on a collision course, and vigilance. The Nasa Planetary Defence Office, and associated network of telescopes around the world, is established exactly for this purpose.
Edit - for clarity, the Nasa PDO structure is:
As you can see, the vast majority of the functions of the PDO is simply in observation, for the above reasons.
answered 4 hours ago
flox
5,134217
add a comment |Â
up vote
4
down vote
First, a little digression on comets: the coma or "hair" (that's the literal Classical Greek translation) of the comet is indeed very, very long, but it's also incredibly rarified (not dense). More importantly, all the material in the coma is being flung away from the comet by the solar wind; it isn't as though the comet will hit us, followed by all the tail material. The nucleus or core of the comet is generally a few tens of kilometers across.
More to the point, what matters isn't so much the volume or composition of the object as its mass. Mass is what will make it hard to deal with. (It's also a large part of what will hurt us on impact. Speed also matters.)
Going off the link Ghedipunk provided, the general strategy is not to blow up the potential impactor but to deflect it. Compared to the size of earth's orbit, earth and any potential impactor are vanishingly tiny, and it wouldn't take much of a course change to make them miss one another. Deflection is easier, relative to the size of the target object, and way less likely to spall off fragments that will hit us anyway.
One way to change course is through an impact, or a series of impacts, from spacecraft. The two ideas NASA seems to be pursuing are kinetic impacts - using the spacecraft itself as a bullet - and nuclear weapons. (As for chemical explosives, my guess is that they don't yield a better bang for the tonnage compared to simply carrying more fuel and accelerating the spacecraft more.) Of these, nukes are quite a bit more powerful, and seem to be the only thing NASA thinks is likely to deflect a >1km diameter asteroid. However they come with all the political considerations you would expect from phrases like "launch nukes into space" and "detonate nukes on incoming asteroids". Also Bruce Willis might get involved and you'd never live it down.
The other method of changing course is to do it gradually. The winning proposal here seems to be the "gravity tractor", which consists in essence of flying a spacecraft very near an asteroid for a prolonged period of time (years to decades) and using its gravity to gently impel the asteroid in a given direction. The advantage is that because no thrust is being directly imparted to the asteroid, its composition and center of mass are irrelevant; this technique will work on so-called "rubble piles" that would fracture from impact or direct thrust. Also, because the magnitude of thrust is so small, the operators have a great deal of fine control over where the asteroid ends up. Finally, there's the benefit that intercepting asteroids and orbiting a thruster around them is something we've done, albeit not for nearly the amount of time required. The disadvantage is the time required, both in terms of detecting it early enough and making sure nothing happens to your spacecraft in that time. (Multiple craft would seem to be prudent, along with a generous margin for error.)
A third option is to laser ablate the impactor. The theory behind this is as follows. When an object is hit by a laser, a small part of its surface absorbs the heat and is converted to plasma, usually. This plasma expands in all directions essentially evenly. The plasma that expands back against the object imparts a force on the object. Therefore, the laser can be used to (very) gradually propel the object in a given direction. The advantage here is that the laser can stay on earth rather than going to the asteroid (space travel is highly inefficient, energetically speaking). The disadvantages are that it's slow, it's never been demonstrated on such a distant target, and of course when all is said and done you have a giant laser emplacement to keep track of.
answered 4 hours ago
Cadence
9,71651839
1
"It's also a large part of what will hurt us on impact. Speed also matters." Just say it! MOMENTUM!
– jpmc26
38 mins ago
add a comment |Â
up vote
1
down vote
Hit it with an asteroid while it is still far away from us.
To do this we would have to have a lot of notice, probably decades. But given the size of the rogue moon, that might not be a bad assumption.
We would compare the orbit of the rogue moon around the sun with asteroids that we consider movable and have orbits that we could adjust to intersect with the rogue moon. If we're lucky, and that interaction happens far enough away from the earth, then we could undergo a mission to adjust the asteroid's orbit so that it collides with the moon and thereby avoiding the collision of the moon with the earth.
answered 4 hours ago
Mathaddict
1,03411
add a comment |Â
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
6
down vote
Observation and foresight is everything
It all depends on how early you can detect it. This changes drastically the response and the chances of success. Luckily, orbital mechanics is generally well-understood, so if you can detect an object early, you can predict, perhaps even for centuries, if this object is likely to impact the Earth.
Not only does early detection give you more time to respond, it also has the advantage that effort required to move something off a trajectory is much smaller for objects that are a long way away, or take a lot of time to reach us. The slightest nudge would have minimal affect in a short time span, but over a long one would have a much larger effect.
So:
If it is large and decades away from hitting Earth: Even the smallest nudge would alter its trajectory over the years. Acting (relatively) quickly, we can send a probe with a nuclear device to land on it (which we can already do), then detonate it to nudge it.
If it is only a year away from hitting Earth: Depending on the mass to move, you need to increase the yield of your device commensurately
If it is only a few days away: Your chances are becoming minimal you can do anything to prevent the impact, and you may need to settle on survival measures.
In all scenarios the best thing you could do is to detect it as early as possible. This means basically more telescopes calibrated specifically to detect objects that may be on a collision course, and vigilance. The Nasa Planetary Defence Office, and associated network of telescopes around the world, is established exactly for this purpose.
Edit - for clarity, the Nasa PDO structure is:
As you can see, the vast majority of the functions of the PDO is simply in observation, for the above reasons.
answered 4 hours ago
flox
5,134217
add a comment |Â
up vote
6
down vote
Observation and foresight is everything
It all depends on how early you can detect it. This changes drastically the response and the chances of success. Luckily, orbital mechanics is generally well-understood, so if you can detect an object early, you can predict, perhaps even for centuries, if this object is likely to impact the Earth.
Not only does early detection give you more time to respond, it also has the advantage that effort required to move something off a trajectory is much smaller for objects that are a long way away, or take a lot of time to reach us. The slightest nudge would have minimal affect in a short time span, but over a long one would have a much larger effect.
So:
If it is large and decades away from hitting Earth: Even the smallest nudge would alter its trajectory over the years. Acting (relatively) quickly, we can send a probe with a nuclear device to land on it (which we can already do), then detonate it to nudge it.
If it is only a year away from hitting Earth: Depending on the mass to move, you need to increase the yield of your device commensurately
If it is only a few days away: Your chances are becoming minimal you can do anything to prevent the impact, and you may need to settle on survival measures.
In all scenarios the best thing you could do is to detect it as early as possible. This means basically more telescopes calibrated specifically to detect objects that may be on a collision course, and vigilance. The Nasa Planetary Defence Office, and associated network of telescopes around the world, is established exactly for this purpose.
Edit - for clarity, the Nasa PDO structure is:
As you can see, the vast majority of the functions of the PDO is simply in observation, for the above reasons.
answered 4 hours ago
flox
5,134217
add a comment |Â
up vote
6
down vote
up vote
6
down vote
Observation and foresight is everything
It all depends on how early you can detect it. This changes drastically the response and the chances of success. Luckily, orbital mechanics is generally well-understood, so if you can detect an object early, you can predict, perhaps even for centuries, if this object is likely to impact the Earth.
Not only does early detection give you more time to respond, it also has the advantage that effort required to move something off a trajectory is much smaller for objects that are a long way away, or take a lot of time to reach us. The slightest nudge would have minimal affect in a short time span, but over a long one would have a much larger effect.
So:
If it is large and decades away from hitting Earth: Even the smallest nudge would alter its trajectory over the years. Acting (relatively) quickly, we can send a probe with a nuclear device to land on it (which we can already do), then detonate it to nudge it.
If it is only a year away from hitting Earth: Depending on the mass to move, you need to increase the yield of your device commensurately
If it is only a few days away: Your chances are becoming minimal you can do anything to prevent the impact, and you may need to settle on survival measures.
In all scenarios the best thing you could do is to detect it as early as possible. This means basically more telescopes calibrated specifically to detect objects that may be on a collision course, and vigilance. The Nasa Planetary Defence Office, and associated network of telescopes around the world, is established exactly for this purpose.
Edit - for clarity, the Nasa PDO structure is:
As you can see, the vast majority of the functions of the PDO is simply in observation, for the above reasons.
answered 4 hours ago
flox
5,134217
Observation and foresight is everything
It all depends on how early you can detect it. This changes drastically the response and the chances of success. Luckily, orbital mechanics is generally well-understood, so if you can detect an object early, you can predict, perhaps even for centuries, if this object is likely to impact the Earth.
Not only does early detection give you more time to respond, it also has the advantage that effort required to move something off a trajectory is much smaller for objects that are a long way away, or take a lot of time to reach us. The slightest nudge would have minimal affect in a short time span, but over a long one would have a much larger effect.
So:
If it is large and decades away from hitting Earth: Even the smallest nudge would alter its trajectory over the years. Acting (relatively) quickly, we can send a probe with a nuclear device to land on it (which we can already do), then detonate it to nudge it.
If it is only a year away from hitting Earth: Depending on the mass to move, you need to increase the yield of your device commensurately
If it is only a few days away: Your chances are becoming minimal you can do anything to prevent the impact, and you may need to settle on survival measures.
In all scenarios the best thing you could do is to detect it as early as possible. This means basically more telescopes calibrated specifically to detect objects that may be on a collision course, and vigilance. The Nasa Planetary Defence Office, and associated network of telescopes around the world, is established exactly for this purpose.
Edit - for clarity, the Nasa PDO structure is:
As you can see, the vast majority of the functions of the PDO is simply in observation, for the above reasons.
answered 4 hours ago
flox
5,134217
edited 3 hours ago
answered 4 hours ago
flox
5,134217
answered 4 hours ago
flox
5,134217
answered 4 hours ago
flox
5,134217
5,134217
add a comment |Â
add a comment |Â
up vote
4
down vote
First, a little digression on comets: the coma or "hair" (that's the literal Classical Greek translation) of the comet is indeed very, very long, but it's also incredibly rarified (not dense). More importantly, all the material in the coma is being flung away from the comet by the solar wind; it isn't as though the comet will hit us, followed by all the tail material. The nucleus or core of the comet is generally a few tens of kilometers across.
More to the point, what matters isn't so much the volume or composition of the object as its mass. Mass is what will make it hard to deal with. (It's also a large part of what will hurt us on impact. Speed also matters.)
Going off the link Ghedipunk provided, the general strategy is not to blow up the potential impactor but to deflect it. Compared to the size of earth's orbit, earth and any potential impactor are vanishingly tiny, and it wouldn't take much of a course change to make them miss one another. Deflection is easier, relative to the size of the target object, and way less likely to spall off fragments that will hit us anyway.
One way to change course is through an impact, or a series of impacts, from spacecraft. The two ideas NASA seems to be pursuing are kinetic impacts - using the spacecraft itself as a bullet - and nuclear weapons. (As for chemical explosives, my guess is that they don't yield a better bang for the tonnage compared to simply carrying more fuel and accelerating the spacecraft more.) Of these, nukes are quite a bit more powerful, and seem to be the only thing NASA thinks is likely to deflect a >1km diameter asteroid. However they come with all the political considerations you would expect from phrases like "launch nukes into space" and "detonate nukes on incoming asteroids". Also Bruce Willis might get involved and you'd never live it down.
The other method of changing course is to do it gradually. The winning proposal here seems to be the "gravity tractor", which consists in essence of flying a spacecraft very near an asteroid for a prolonged period of time (years to decades) and using its gravity to gently impel the asteroid in a given direction. The advantage is that because no thrust is being directly imparted to the asteroid, its composition and center of mass are irrelevant; this technique will work on so-called "rubble piles" that would fracture from impact or direct thrust. Also, because the magnitude of thrust is so small, the operators have a great deal of fine control over where the asteroid ends up. Finally, there's the benefit that intercepting asteroids and orbiting a thruster around them is something we've done, albeit not for nearly the amount of time required. The disadvantage is the time required, both in terms of detecting it early enough and making sure nothing happens to your spacecraft in that time. (Multiple craft would seem to be prudent, along with a generous margin for error.)
A third option is to laser ablate the impactor. The theory behind this is as follows. When an object is hit by a laser, a small part of its surface absorbs the heat and is converted to plasma, usually. This plasma expands in all directions essentially evenly. The plasma that expands back against the object imparts a force on the object. Therefore, the laser can be used to (very) gradually propel the object in a given direction. The advantage here is that the laser can stay on earth rather than going to the asteroid (space travel is highly inefficient, energetically speaking). The disadvantages are that it's slow, it's never been demonstrated on such a distant target, and of course when all is said and done you have a giant laser emplacement to keep track of.
answered 4 hours ago
Cadence
9,71651839
1
"It's also a large part of what will hurt us on impact. Speed also matters." Just say it! MOMENTUM!
– jpmc26
38 mins ago
add a comment |Â
up vote
4
down vote
First, a little digression on comets: the coma or "hair" (that's the literal Classical Greek translation) of the comet is indeed very, very long, but it's also incredibly rarified (not dense). More importantly, all the material in the coma is being flung away from the comet by the solar wind; it isn't as though the comet will hit us, followed by all the tail material. The nucleus or core of the comet is generally a few tens of kilometers across.
More to the point, what matters isn't so much the volume or composition of the object as its mass. Mass is what will make it hard to deal with. (It's also a large part of what will hurt us on impact. Speed also matters.)
Going off the link Ghedipunk provided, the general strategy is not to blow up the potential impactor but to deflect it. Compared to the size of earth's orbit, earth and any potential impactor are vanishingly tiny, and it wouldn't take much of a course change to make them miss one another. Deflection is easier, relative to the size of the target object, and way less likely to spall off fragments that will hit us anyway.
One way to change course is through an impact, or a series of impacts, from spacecraft. The two ideas NASA seems to be pursuing are kinetic impacts - using the spacecraft itself as a bullet - and nuclear weapons. (As for chemical explosives, my guess is that they don't yield a better bang for the tonnage compared to simply carrying more fuel and accelerating the spacecraft more.) Of these, nukes are quite a bit more powerful, and seem to be the only thing NASA thinks is likely to deflect a >1km diameter asteroid. However they come with all the political considerations you would expect from phrases like "launch nukes into space" and "detonate nukes on incoming asteroids". Also Bruce Willis might get involved and you'd never live it down.
The other method of changing course is to do it gradually. The winning proposal here seems to be the "gravity tractor", which consists in essence of flying a spacecraft very near an asteroid for a prolonged period of time (years to decades) and using its gravity to gently impel the asteroid in a given direction. The advantage is that because no thrust is being directly imparted to the asteroid, its composition and center of mass are irrelevant; this technique will work on so-called "rubble piles" that would fracture from impact or direct thrust. Also, because the magnitude of thrust is so small, the operators have a great deal of fine control over where the asteroid ends up. Finally, there's the benefit that intercepting asteroids and orbiting a thruster around them is something we've done, albeit not for nearly the amount of time required. The disadvantage is the time required, both in terms of detecting it early enough and making sure nothing happens to your spacecraft in that time. (Multiple craft would seem to be prudent, along with a generous margin for error.)
A third option is to laser ablate the impactor. The theory behind this is as follows. When an object is hit by a laser, a small part of its surface absorbs the heat and is converted to plasma, usually. This plasma expands in all directions essentially evenly. The plasma that expands back against the object imparts a force on the object. Therefore, the laser can be used to (very) gradually propel the object in a given direction. The advantage here is that the laser can stay on earth rather than going to the asteroid (space travel is highly inefficient, energetically speaking). The disadvantages are that it's slow, it's never been demonstrated on such a distant target, and of course when all is said and done you have a giant laser emplacement to keep track of.
answered 4 hours ago
Cadence
9,71651839
1
"It's also a large part of what will hurt us on impact. Speed also matters." Just say it! MOMENTUM!
– jpmc26
38 mins ago
add a comment |Â
up vote
4
down vote
up vote
4
down vote
First, a little digression on comets: the coma or "hair" (that's the literal Classical Greek translation) of the comet is indeed very, very long, but it's also incredibly rarified (not dense). More importantly, all the material in the coma is being flung away from the comet by the solar wind; it isn't as though the comet will hit us, followed by all the tail material. The nucleus or core of the comet is generally a few tens of kilometers across.
More to the point, what matters isn't so much the volume or composition of the object as its mass. Mass is what will make it hard to deal with. (It's also a large part of what will hurt us on impact. Speed also matters.)
Going off the link Ghedipunk provided, the general strategy is not to blow up the potential impactor but to deflect it. Compared to the size of earth's orbit, earth and any potential impactor are vanishingly tiny, and it wouldn't take much of a course change to make them miss one another. Deflection is easier, relative to the size of the target object, and way less likely to spall off fragments that will hit us anyway.
One way to change course is through an impact, or a series of impacts, from spacecraft. The two ideas NASA seems to be pursuing are kinetic impacts - using the spacecraft itself as a bullet - and nuclear weapons. (As for chemical explosives, my guess is that they don't yield a better bang for the tonnage compared to simply carrying more fuel and accelerating the spacecraft more.) Of these, nukes are quite a bit more powerful, and seem to be the only thing NASA thinks is likely to deflect a >1km diameter asteroid. However they come with all the political considerations you would expect from phrases like "launch nukes into space" and "detonate nukes on incoming asteroids". Also Bruce Willis might get involved and you'd never live it down.
The other method of changing course is to do it gradually. The winning proposal here seems to be the "gravity tractor", which consists in essence of flying a spacecraft very near an asteroid for a prolonged period of time (years to decades) and using its gravity to gently impel the asteroid in a given direction. The advantage is that because no thrust is being directly imparted to the asteroid, its composition and center of mass are irrelevant; this technique will work on so-called "rubble piles" that would fracture from impact or direct thrust. Also, because the magnitude of thrust is so small, the operators have a great deal of fine control over where the asteroid ends up. Finally, there's the benefit that intercepting asteroids and orbiting a thruster around them is something we've done, albeit not for nearly the amount of time required. The disadvantage is the time required, both in terms of detecting it early enough and making sure nothing happens to your spacecraft in that time. (Multiple craft would seem to be prudent, along with a generous margin for error.)
A third option is to laser ablate the impactor. The theory behind this is as follows. When an object is hit by a laser, a small part of its surface absorbs the heat and is converted to plasma, usually. This plasma expands in all directions essentially evenly. The plasma that expands back against the object imparts a force on the object. Therefore, the laser can be used to (very) gradually propel the object in a given direction. The advantage here is that the laser can stay on earth rather than going to the asteroid (space travel is highly inefficient, energetically speaking). The disadvantages are that it's slow, it's never been demonstrated on such a distant target, and of course when all is said and done you have a giant laser emplacement to keep track of.
answered 4 hours ago
Cadence
9,71651839
First, a little digression on comets: the coma or "hair" (that's the literal Classical Greek translation) of the comet is indeed very, very long, but it's also incredibly rarified (not dense). More importantly, all the material in the coma is being flung away from the comet by the solar wind; it isn't as though the comet will hit us, followed by all the tail material. The nucleus or core of the comet is generally a few tens of kilometers across.
More to the point, what matters isn't so much the volume or composition of the object as its mass. Mass is what will make it hard to deal with. (It's also a large part of what will hurt us on impact. Speed also matters.)
Going off the link Ghedipunk provided, the general strategy is not to blow up the potential impactor but to deflect it. Compared to the size of earth's orbit, earth and any potential impactor are vanishingly tiny, and it wouldn't take much of a course change to make them miss one another. Deflection is easier, relative to the size of the target object, and way less likely to spall off fragments that will hit us anyway.
One way to change course is through an impact, or a series of impacts, from spacecraft. The two ideas NASA seems to be pursuing are kinetic impacts - using the spacecraft itself as a bullet - and nuclear weapons. (As for chemical explosives, my guess is that they don't yield a better bang for the tonnage compared to simply carrying more fuel and accelerating the spacecraft more.) Of these, nukes are quite a bit more powerful, and seem to be the only thing NASA thinks is likely to deflect a >1km diameter asteroid. However they come with all the political considerations you would expect from phrases like "launch nukes into space" and "detonate nukes on incoming asteroids". Also Bruce Willis might get involved and you'd never live it down.
The other method of changing course is to do it gradually. The winning proposal here seems to be the "gravity tractor", which consists in essence of flying a spacecraft very near an asteroid for a prolonged period of time (years to decades) and using its gravity to gently impel the asteroid in a given direction. The advantage is that because no thrust is being directly imparted to the asteroid, its composition and center of mass are irrelevant; this technique will work on so-called "rubble piles" that would fracture from impact or direct thrust. Also, because the magnitude of thrust is so small, the operators have a great deal of fine control over where the asteroid ends up. Finally, there's the benefit that intercepting asteroids and orbiting a thruster around them is something we've done, albeit not for nearly the amount of time required. The disadvantage is the time required, both in terms of detecting it early enough and making sure nothing happens to your spacecraft in that time. (Multiple craft would seem to be prudent, along with a generous margin for error.)
A third option is to laser ablate the impactor. The theory behind this is as follows. When an object is hit by a laser, a small part of its surface absorbs the heat and is converted to plasma, usually. This plasma expands in all directions essentially evenly. The plasma that expands back against the object imparts a force on the object. Therefore, the laser can be used to (very) gradually propel the object in a given direction. The advantage here is that the laser can stay on earth rather than going to the asteroid (space travel is highly inefficient, energetically speaking). The disadvantages are that it's slow, it's never been demonstrated on such a distant target, and of course when all is said and done you have a giant laser emplacement to keep track of.
answered 4 hours ago
Cadence
9,71651839
edited 2 hours ago
answered 4 hours ago
Cadence
9,71651839
answered 4 hours ago
Cadence
9,71651839
answered 4 hours ago
Cadence
9,71651839
9,71651839
1
"It's also a large part of what will hurt us on impact. Speed also matters." Just say it! MOMENTUM!
– jpmc26
38 mins ago
add a comment |Â
1
"It's also a large part of what will hurt us on impact. Speed also matters." Just say it! MOMENTUM!
– jpmc26
38 mins ago
1
1
"It's also a large part of what will hurt us on impact. Speed also matters." Just say it! MOMENTUM!
– jpmc26
38 mins ago
"It's also a large part of what will hurt us on impact. Speed also matters." Just say it! MOMENTUM!
– jpmc26
38 mins ago
add a comment |Â
up vote
1
down vote
Hit it with an asteroid while it is still far away from us.
To do this we would have to have a lot of notice, probably decades. But given the size of the rogue moon, that might not be a bad assumption.
We would compare the orbit of the rogue moon around the sun with asteroids that we consider movable and have orbits that we could adjust to intersect with the rogue moon. If we're lucky, and that interaction happens far enough away from the earth, then we could undergo a mission to adjust the asteroid's orbit so that it collides with the moon and thereby avoiding the collision of the moon with the earth.
answered 4 hours ago
Mathaddict
1,03411
add a comment |Â
up vote
1
down vote
Hit it with an asteroid while it is still far away from us.
To do this we would have to have a lot of notice, probably decades. But given the size of the rogue moon, that might not be a bad assumption.
We would compare the orbit of the rogue moon around the sun with asteroids that we consider movable and have orbits that we could adjust to intersect with the rogue moon. If we're lucky, and that interaction happens far enough away from the earth, then we could undergo a mission to adjust the asteroid's orbit so that it collides with the moon and thereby avoiding the collision of the moon with the earth.
answered 4 hours ago
Mathaddict
1,03411
add a comment |Â
up vote
1
down vote
up vote
1
down vote
Hit it with an asteroid while it is still far away from us.
To do this we would have to have a lot of notice, probably decades. But given the size of the rogue moon, that might not be a bad assumption.
We would compare the orbit of the rogue moon around the sun with asteroids that we consider movable and have orbits that we could adjust to intersect with the rogue moon. If we're lucky, and that interaction happens far enough away from the earth, then we could undergo a mission to adjust the asteroid's orbit so that it collides with the moon and thereby avoiding the collision of the moon with the earth.
answered 4 hours ago
Mathaddict
1,03411
Hit it with an asteroid while it is still far away from us.
To do this we would have to have a lot of notice, probably decades. But given the size of the rogue moon, that might not be a bad assumption.
We would compare the orbit of the rogue moon around the sun with asteroids that we consider movable and have orbits that we could adjust to intersect with the rogue moon. If we're lucky, and that interaction happens far enough away from the earth, then we could undergo a mission to adjust the asteroid's orbit so that it collides with the moon and thereby avoiding the collision of the moon with the earth.
answered 4 hours ago
Mathaddict
1,03411
answered 4 hours ago
Mathaddict
1,03411
answered 4 hours ago
Mathaddict
1,03411
answered 4 hours ago
Mathaddict
1,03411
1,03411
add a comment |Â
add a comment |Â
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1
Moon-sized isn't a comet, it's a planet. To give an idea of how large comets are, here's a list of comets that are easy for us to observe: en.wikipedia.org/wiki/List_of_periodic_comets -- As the question is now, if a moon-sized object were going to hit the Earth, all life as we know it will most definitely end.
– Ghedipunk
5 hours ago
It really depends on when we see it. If it's far out, even a tiny nudge can make it miss entirely, and my "knows some things" mind says that if money weren't an object, it would be "Fairly easy" (Although highly complex and extremely expensive) to do. If we see it really close? Well, we wouldn't have time to build the stuff necessary, let alone get the mission going and doing it. As @Ghedipunk says, though, a moon-type object would simply to large. Comet or asteroid? Far more likely. Density (Actually: Mass) matters more than size here.
– Andon
5 hours ago
1
@Andon But if it is far out, we will probably have not enough precision to determine if it is going to hit us, and thus we will not know if giving it a nudge will put it in collision path. Also, I think you are overestimating the payload we can put "far out"; the nudge will be not tiny but "very tiny".
– SJuan76
5 hours ago
3
@Andon Coins would be far more efficient.
– Cadence
5 hours ago
1
@Muze I was referring to us as the people commenting. As in, I, personally, don't have the knowledge or information to back up my claims. There ARE people on Worldbuilding that do, they're just not me. I'm sure they'll be around eventually.
– Andon
5 hours ago