How Can We Effectively Destroy An Asteroid Headed for Earth?

[DaveC426913]

joema,

In the celestial mechanics of natural stellar satellites; 18 metric tons is a PITTANCE!

Dr. Gregory Greenman
Physicist

True, but a 400 meter wide keyhole is equally a dust mote.

 

[Astronuc]

NASA Report on Asteroids Suggests Nuclear Option
by Nell Boyce
http://www.npr.org/templates/story/story.php?storyId=7867322

Morning Edition, March 13, 2007 · Scientists have sent Congress a report on ways to prevent an asteroid from hitting Earth. Among the proposals: Use nuclear weapons to nudge a big space rock off a collision course. Some scientists don't think much of that idea.

Scientists Gather at Conference to Stop Asteroids
by Alex Chadwick
http://www.npr.org/templates/story/story.php?storyId=7713661

Day to Day, March 5, 2007 · A Planetary Defense Conference that starts Monday will look into possible methods of preventing asteroids from hitting Earth. William Ailor, a director with The Aerospace Corporation, talks about the threat of a direct hit.

Still a controversial topic.

 

[Morbius]

Still a controversial topic.

Astronuc,

A colleague of mine is active in the asteroid deflection field. He told me he was recently
at a conference that featured a paper by former astronaut Schweikert, who outlined the
parameters of a "gravity tractor" spacecraft .

My colleague did a calculation to show that you get more deflection impulse into the
asteroid if you CRASH the gravity tractor into the asteroid; than if you use it as a gravity
tractor.

Dr. Gregory Greenman
Physicist

 

[Astronuc]

A colleague of mine is active in the asteroid deflection field. He told me he was recently at a conference that featured a paper by former astronaut Schweikert, who outlined the parameters of a "gravity tractor" spacecraft .

My colleague did a calculation to show that you get more deflection impulse into the asteroid if you CRASH the gravity tractor into the asteroid; than if you use it as a gravity tractor.

:rofl: Well I suppose it will likely be a one way trip, but it sounds like some folks want a 'reusable' space tractor.

I think though an impulsive load makes much more sense - and the further out the deflection, the better.

 

[Morbius]

:rofl: Well I suppose it will likely be a one way trip, but it sounds like some folks want a 'reusable' space tractor.

I think though an impulsive load makes much more sense - and the further out the deflection, the better.

Astronuc,

Yes - even if a "gravity tractor" is used as intended; it will take a LONG time to deflect the
asteroid.

I also think an impulsive load makes WAY more sense. If you crash the tractor into the
asteroid; you can then measure the new trajectory of the asteroid and determine if the
deflection is enough. If there were any wrong assumptions in the original calculation; e.g.
the asteroid mass; the process can be repeated.

Since the "gravity tractor" is a much more gradual deflection; by the time one finds out
that the deflection rate is too slow with the "gravity tractor"; precious time has been
wasted.

Dr. Gregory Greenman
Physicist

 

[joema]

My colleague did a calculation to show that you get more deflection impulse into the asteroid if you CRASH the gravity tractor into the asteroid;...Since the "gravity tractor" is a much more gradual deflection; by the time one finds out that the deflection rate is too slow with the "gravity tractor"; precious time has been wasted...

The deflection rate is determined by the relative masses of the vehicle and asteroid, plus the hover height. Two of those would be known, the asteroid mass could be estimated. So even before launch the deflection rate could be estimated.

However your point about more deflection from actual impact makes sense. Kinetic energy increases as the square of velocity (KE = 1/2*m*v^2). Just to reach the asteroid, the velocity would be extremely high, and the impact velocity (relative to the asteroid) even higher.

The proposed gravity tractor might be 18 metric tons: http://news.nationalgeographic.com/news/2007/02/070217-asteroid-impact.html

It would probably be boosted to at least 15 km/sec on a direct escape trajectory, something like the New Horizons probe: http://en.wikipedia.org/wiki/New_horizons

The asteroid relative impact speed would probably at least 25 km/sec.

Thus the impact energy would be 5.625E12 joules (1.56E9 watt hours).

That's roughly equivalent to 1.4 million kg (!) of high explosives.

Don't know what the max energy imparted by a gravity tractor, but it must be far less than this.

Also the gravity tractor has an additional burden -- it must decelerate from high speed to rendezvous with the asteroid. Thus all that fuel mass required for rendezvous is subtracted from payload mass. I'd be curious if your colleague took that into account. It's possible the gravity tractor is even worse than first appears.

 

[Morbius]

Thus the impact energy would be 5.625E12 joules (1.56E9 watt hours).

That's roughly equivalent to 1.4 million kg (!) of high explosives.

joema,

In terms of explosive yield; 1 kiloton = 4.186 terajoules = 4.186e+12 joules.

So the impact energy is 1.34 kilontons; which is the same energy as a very small
atomic bomb - the Hiroshima bomb was over 10X as powerful, and the Nagasaki and
Trinity bombs were about 15X as powerful.

It's also many thousands of times less powerful than a thermonuclear device with a
mere fraction of the weight of the impactor.

When it comes to making alterations to the trajectories of asteroids; 1.4 million kg of
high explosive energy is UNIMPRESSIVE.

Dr. Gregory Greenman
Physicist

 

[joema]

...When it comes to making alterations to the trajectories of asteroids; 1.4 million kg of high explosive energy is UNIMPRESSIVE...

Yes, agreed. I only meant the energy and resultant momentum change imparted from a direct kinetic impact is probably much greater than that from a gravity tractor of the same payload mass at liftoff.

The gravity tractor concept is interesting and may be useful in some circumstances, but it seems quite limited in the delta V imparted to the asteroid. Especially considering the additional booster payload requirement to lift enough propellant for deceleration and rendezvous, plus that required for station keeping at the asteroid.

The kinetic impact method could use all the mass during direct impact, which increases the imparted energy.

You're right if you need more than a tiny deflection, it appears nuclear is the only near-term option using currently available technology.

The light weight of a a nuclear warhead would allow extremely high velocity, thus enable short reaction time intercept options unavailable with any other technique. E.g, the Nasa New Horizons probe weighed 478 kg and was boosted to 16.2 km/sec by an off-the-shelf Atlas V. It crossed the moon's orbit 9 hours after launch. An asteroid-deflecting nuclear warhead (plus terminal guidance) could easily fit within the same space/mass.

Typical warhead yield-to-weight is 350 kg per megaton, so an approx. 250-500 kt warhead might fit that booster size, leaving about 300-400 kg payload for packaging, guidance, terminal propulsion, etc.

Years of advance warning is good -- it enables more options. But the common notion that no other workable options exist for a timeframe on the order of months isn't really correct.

 

[Morbius]

You're right if you need more than a tiny deflection, it appears nuclear is the only near-term option using currently available technology.

Years of advance warning is good -- it enables more options. But the common notion that no other workable options exist for a timeframe on the order of months isn't really correct.

joema,

Agreed. The gravity tractor only works if you have extended advanced warning of an
asteroid on collision course. A gravity tractor is useless if a "quick" deflection is needed.

As you point out; a nuclear warhead can be used for a "quick" deflection. The nuclear
option is also available if there is extended advanced warning.

So one "solution", the gravity tractor only works in one limit of the threat spectrum, but
not the other. The nuclear option works in both limits. I wonder why limited resources
should be expended on a "solution" that only works in one limit; when a solution that
works in both limits is available.

Dr. Gregory Greenman
Physicist

 

[Aero Stud]

There's an international student competition about this subject of an asteroid deflection being held now. Except they're limmited to using one specific settelite launcher or something like that. Guys from my AE semester at the Technion started working on it as well. It's actualy a specific asteroid I think, something like 300 meters in diameter with some small chance of hitting us in something like 2027. Don't remember more details.

joema,

Agreed. The gravity tractor only works if you have extended advanced warning of an
asteroid on collision course. A gravity tractor is useless if a "quick" deflection is needed.

As you point out; a nuclear warhead can be used for a "quick" deflection. The nuclear
option is also available if there is extended advanced warning.

So one "solution", the gravity tractor only works in one limit of the threat spectrum, but
not the other. The nuclear option works in both limits. I wonder why limited resources
should be expended on a "solution" that only works in one limit; when a solution that
works in both limits is available.

Dr. Gregory Greenman
Physicist

The problem with the nuclear option is that if the asteroid is big anough you are likely to end up with several smaller parts, with pretty much the same trajectory and still way too big to burn in the atmosphere. It might even be worse than before in terms of expected damage.

Gravitational deflection may be a good solution when we know years ahead of the impact and the asteroid is not too big.

Personally, the best current option I can think of is nuclear, also. Except that instead of sending one missile we should use a battery of missiles that will hit the asteroid and its parts one at a time in a controlled manner - so we could take it apart to small anough pieces systematicly and/or deflect it and its parts. Also, depending on the asteroid's composition we could make rockets that could penetrate some distance inside by coming in at relatively high speed, if it promises better results.

One of the biggest problems is the amount of info we have about an asteroid. It could be made of many different materials, with different densities and moments of inertia or even be comprised of multiple parts moving together caught by their mutual gravity. Without collecting this information about the asteroid first, predicting the results of a nuclear bombardment is very difficult.

 

[Morbius]

The problem with the nuclear option is that if the asteroid is big anough you are likely to end up with several smaller parts, with pretty much the same trajectory and still way too big to burn in the atmosphere. It might even be worse than before in terms of expected damage.

Aero Stud,

WRONG WRONG WRONG!

Unfortunately, you fallen for the naive unscientific "clap trap" that you usually see in the
media about the nuclear option - that the intent is to blow up the asteroid.

NOBODY in the field of nuclear deflection is proposing that!

The object of using a nuclear device is NOT to blow up the asteroid but to DEFLECT it.

You deflect the asteroid by blowing up the bomb NEAR the asteroid but NOT on the
asteroid.

The radiation from the bomb will ablate the surface of the asteroid and result in a
impulse which DEFLECTS the asteroid. A nuclear warhead used in this manner will
result in a deflection impulse MANY times greater than what is available from ANY
type of rocket propelled by chemical propellant.

Dr. Gregory Greenman
Physicist

 

[Aero Stud]

I think that maybe you didn't quite read into what I wrote at the end. Which is basicly the main problem. We don't know what those things are made of. There's a huge variety of objects out there. And even looking at them a lot from down here and up in orbit and even going near them, the uncertainty factors are still relatively high. So they're not just golf balls floating around. Besides, we never blew up a nuclear warhead in space before. Not to mention, that unless you promise the political guys high chances of success they, with all the public pressure in addition, won't allow any nuclear weapons to be launched into space.

 

[Morbius]

I think that maybe you didn't quite read into what I wrote at the end. Which is basicly the main problem. We don't know what those things are made of. There's a huge variety of objects out there. And even looking at them a lot from down here and up in orbit and even going near them, the uncertainty factors are still relatively high. Besides, we never blew up a nuclear warhead in space before. Not to mention, that unless you promise the political guys high chances of success they, with all the public pressure in addition, won't allow any nuclear weapons to be launched into space.

Aero Stud,

WRONG! WRONG! WRONG!

You need to do some RESEARCH before you post!

We certainly HAVE blown up nuclear warheads in space!

It is now against Treaty to do so - but in the early days of atmospheric nuclear testing
we certainly DID put nuclear warheads on missiles and detonate them in space. In fact,
that's how the phenomenon of ElectroMagnetic Pulse or EMP was discovered.

Actually we DO know a fair amount about the composition of asteroids, and there have
been probes sent to rendevous with asteroids, and even land on them; from which we
have found out a lot.

Even so - the lack of knowledge composition of the asteroid is NOT an unsurmountable
obstacle to deflecting it. The nuclear warhead will vaporize ANYTHING!

As far as the political problem - for Heaven's sake THINK about it. If we suddenly find
that an asteroid is heading for Earth somewhere from beyond the Ort Cloud and it's
going to impact on THIS orbit - the only thing powerful enough to deflect it will be a
nuclear weapon.

Do you REALLY think the politicians and the environmentalists are going to say,
"Oh NO - don't use a nuclear weapon - I'd rather have the Earth destroyed by an
asteroid than to use a nuclear weapon!"

If it's a question of SURVIVAL of the Earth - launching a nuke will be ZERO problem.

Dr. Gregory Greenman
Physicist

 

[Aero Stud]

You need to do some RESEARCH before you post!

We certainly HAVE blown up nuclear warheads in space!

Really, in space ? Never heard of it. Sorry.

Actually we DO know a fair amount about the composition of asteroids, and there have
been probes sent to rendevous with asteroids, and even land on them; from which we
have found out a lot.

Even so - the lack of knowledge composition of the asteroid is NOT an unsurmountable
obstacle to deflecting it. The nuclear warhead will vaporize ANYTHING!

I know about the asteroid (don't remember more to add an "s" ), but they can be a lot different. I agree nothing is unsurmountable here, but it is a problem - and if you're considering different alternatives then things like this have their weight I think.

About the nuclear missile vaporising anything again everything it's relative, if it's several miles wide and made mostly of iron - there's a lot of blowing up needed there so who knows. I agree with the nuclear missiles, just saying that to be sure it's better to use several than hope just one big missile will do it and not forget to at least try to develop other options, can't hurt I think.

As far as the political problem - for Heaven's sake THINK about it. If we suddenly find
that an asteroid is heading for Earth somewhere from beyond the Ort Cloud and it's
going to impact on THIS orbit - the only thing powerful enough to deflect it will be a
nuclear weapon.

Do you REALLY think the politicians and the environmentalists are going to say,
"Oh NO - don't use a nuclear weapon - I'd rather have the Earth destroyed by an
asteroid than to use a nuclear weapon!"

If it's a question of SURVIVAL of the Earth - launching a nuke will be ZERO problem.

Dr. Gregory Greenman
Physicist

I think that when there are other solutions to compete with and/or the impact is not certain then people may prefer to wait until it is certain and the solution chosen is the best one, which doesn't leave that much time. But it's not really an argument, more of a sidenote to the nuclear option which like I said I generally argue for too. I see that maybe you're a bit emotional about the discussion.

The chemical rocket in case of a gravitational diflection just delivers the mass. Even a 1 ton mass can do a lot to say phousands of tons if the trajectory change is many years prior to impact. I don't see though how they can do it for now if they can't even calculate whether there will be an impact or not - and that's a pretty wide range at the end.

 

[joema]

...we never blew up a nuclear warhead in space before...

There have been numerous nuclear detonations in space (note the typical definition of "space" is 100 km altitude):

http://www.johnstonsarchive.net/nuclear/hane.html

 

[Aero Stud]

There have been numerous nuclear detonations in space (note the typical definition of "space" is 100 km altitude):

http://www.johnstonsarchive.net/nuclear/hane.html

Interesting. Did they also measure how the explosion changed the trajectories of those sattelite's that are mentioned ? Considering that's the primary objective here.

 

[joema]

Interesting. Did they also measure how the explosion changed the trajectories of those sattelite's that are mentioned ? Considering that's the primary objective here.

Don't understand your point. Those explosions weren't intended to change the trajectory of anything.

The point is numerous nuclear detonations in space have already happened, so doing it again in deep space to deflect an asteroid wouldn't be new. It would be much farther out in space, likely not visible from earth.

The fuzing and guidance technology for doing a precision stand-off detonation is well developed. It's essentially off-the-shelf technology.

Given years of advance warning, there are various options for asteroid deflection -- kinetic impact, gravity tractor, nuclear, etc. Given less than a year, the nuclear option is probably the only one available.

Given the stakes, it seems you'd probably want diverse redundant methods. That way if one fails, you'd try others.

 

[Aero Stud]

Don't understand your point. Those explosions weren't intended to change the trajectory of anything.

What I'm saying is that if we haven't measured in any way the effects of the explosion in terms of deflecting objects in space, for example by means of tracking those sattelite's, if any, that were destroyed directly by the impact and not due to EMP short-circuiting them, then are we currently able to predict accuratly anough the effects of such deflection explosions (assumng we know all we need to know about the asteroid itself). Or in simpler words, can you calculate accurately anough the momentum you'll impart by an explosion X feet away on a surface of Y dimensions at Z angle ?

The fuzing and guidance technology for doing a precision stand-off detonation is well developed. It's essentially off-the-shelf technology.

Given years of advance warning, there are various options for asteroid deflection -- kinetic impact, gravity tractor, nuclear, etc. Given less than a year, the nuclear option is probably the only one available.

Given the stakes, it seems you'd probably want diverse redundant methods. That way if one fails, you'd try others.

Yup, developing other options shouldn't be neglected.

 

[Morbius]

Or in simpler words, can you calculate accurately anough the momentum you'll impart by an explosion X feet away on a surface of Y dimensions at Z angle ?.

Aero Stud,

YES - that's essentially how inertial confinement fusion works; both the laser driven
and the pulse power driven - on a small scale.

The same thing happens on a large scale; but I'm not going to talk about that.
But the physics is the same.

http://www.space.com/businesstechnology/technology/nudging_not_nuking_000211.html

http://www.llnl.gov/planetary/

http://www.aero.org/conferences/planetarydefense/documents/Barbee_et_al_NASA_NEO_Workshop_Paper_June_2006.pdf

http://pdf.aiaa.org/preview/CDReadyMPDC04_865/PV2004_1481.pdf

Dr. Gregory Greenman
Physicist

 

[joema]

What I'm saying is that if we haven't measured in any way the effects of the explosion in terms of deflecting objects in space, for example by means of tracking those sattelite's, if any, that were destroyed directly by the impact...

I was simply responding to your statement that nuclear devices have never been detonated in space, which they have. I wasn't saying they were used to deflect or destroy satellites; to my knowledge they haven't been.

However it's not necessary that nuclear explosions in space be tested against actual asteroids before attempting a deflection. Nor is it necessary to know it would work. It would be nice additional information, as more quality data is generally better. However nuclear explosions have been tested thousands of times on earth. The effects on materials are well understood. In some tests a vacuum chamber was positioned adjacent to the device to measure effects against materials in a vacuum.

The ablative impulse from X and neutron radiation vaporizing a thin layer of material can be calculated. The magnitude and type of energy release based on warhead type is known, and the asteroid deflection can be calculated.

Here is a research paper where this was done (1.1MB .pdf): http://www.llnl.gov/planetary/pdfs/Interdiction/04-Solem.pdf

In any asteroid deflection technique (nuclear or non-nuclear), you wouldn't rely on a single attempt. There would be simply too much at stake. You'd have multiple redundant methods. E.g, four gravity tractor missions, anyone of which could achieve necessary deflection, launched sequentially. They'd likely be backed up by several nuclear methods if all of those failed.

If reaction time didn't permit non-nuclear methods, you'd likely have several nuclear deflections used conservatively in a repeating shoot-look-shoot sequence. That way the actual achieved deflection of the first detonation could be measured and used to fine tune the stand off distance of the subsequent ones.

 

[Morbius]

However it's not necessary that nuclear explosions in space be tested against actual asteroids before attempting a deflection. Nor is it necessary to know it would work. It would be nice additional information, as more quality data is generally better. However nuclear explosions have been tested thousands of times on earth. The effects on materials are well understood. In some tests a vacuum chamber was positioned adjacent to the device to measure effects against materials in a vacuum.

joema,

Yes - back in the days when the USA conducted nuclear tests; such tests were made by
the Dept. of Energy for the Dept of Defense in long horizontal tunnel shots:

http://www.nv.doe.gov/library/publications/newsviews/tunnel.htm

Dr. Gregory Greenman
Physicist

 

[Aero Stud]

I was simply responding to your statement that nuclear devices have never been detonated in space, which they have. I wasn't saying they were used to deflect or destroy satellites; to my knowledge they haven't been.

I was basing it on what's written in the link you posted with the different detonations listed. They say several sattelites were destroyed (I'm guessing they just short circuited due to EMP, but maybe some were directly hit by the blast).

 

[joema]

The electronics in those satellites were damaged by the radiation, either direct or indirect. Whether it was EMP, neutron, gamma radiation or a perturbation of radiation belts around earth, I don't know. E.g, satellites not properly rad hardened can be damaged by passing through the South Atlantic Anomaly: http://en.wikipedia.org/wiki/South_Atlantic_Anomaly

It wouldn't be from blast, as there is no blast in space -- no atmosphere to form a blast wave.

They key item in calculating asteroid deflection is how the material reacts the ablative radiation burst from a stand off detonation. I'm sure the materials science of that is well understood from the 2,000+ nuclear tests that have already happened. Nowadays sophisticated computer modeling can take that base data and extrapolate based on various possible asteroid material compositions.

The vacuum of space actually simplifies things in that you have no blast wave to worry about.

However we don't know much about the composition of asteroids and comets. The Deep Impact mission helped some: http://en.wikipedia.org/wiki/Deep_Impact_(space_mission)

We're also blind to approach trajectories near the sun. The European Gaia probe might help this when launched in 2011: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=29806

The European Don Quijote probe will attempt an asteroid impact to measure the achievable deflection. This will also reveal information about the asteroid's physical makeup: http://www.esa.int/esaCP/SEML9B8X9DE_index_0.html

 

[Chronos]

The physics are pretty simple - no matter, no matter to propogate a shock wave. A nuclear detonation would not be effective unless near enough to the asteroid to vaporize enough mass to propogate a shock wave. It might be possible to achieve the desired effect through a carefully timed sequence of detonations. The one thing you really should try to avoid is breaking up a large asteroid into a collosal menage of Mt. Everest sized fragments.

 

[Morbius]

The physics are pretty simple - no matter, no matter to propogate a shock wave. A nuclear detonation would not be effective unless near enough to the asteroid to vaporize enough mass to propogate a shock wave.

Chronos,

I'm sorry - but you are wrong here.

As long as you vaporize mass, and some of that mass ablates in the direction of the
bomb; the asteroid will recoil in order to conserve momentum. Hence there will be an
impulse to the asteroid.

The impulse doesn't have to be strong enough to propagate a shock wave. You get a
shock wave when the distrurbance attempts to propagate through a medium at a
speed in excess of the speed of sound in that medium.

The conservation of momentum is INDEPENDENT of whether the disturbance propagates
subsonically, or supersonically. Therefore, the recoil of the asteroid, and hence the
impulse delivered to it is also INDEPENDENT of whether the disturbance is subsonic or
supersonic.

Dr. Gregory Greenman
Physicist

 

[joema]

...no matter, no matter to propagate a shock wave. A nuclear detonation would not be effective unless near enough to the asteroid to vaporize enough mass to propagate a shock wave...

Clarifying for other readers: there'd be no atmospheric blast wave or shock wave as seen within the Earth's atmosphere. There might be a shock wave within the asteroid material, produced when the X and neutron radiation from a stand-off detonation vaporizes a thin layer of surface material.

The two separate effects (radiation vs blast) can clearly be seen from video of past nuclear tests.

About 30 sec into the below video, the surface of several vehicles and structures are vaporized by a nuclear explosion, yet they aren't demolished -- until the blast wave later arrives.

In space there would only be the initial vaporization, no blast wave.

http://video.google.com/videoplay?docid=-8173791211944754735

 

[Morbius]

Clarifying for other readers: there'd be no atmospheric blast wave or shock wave as seen within the Earth's atmosphere. There might be a shock wave within the asteroid material, produced when the X and neutron radiation from a stand-off detonation vaporizes a thin layer of surface material.

joema,

Correct you are.

There's no blast or shock wave in space between the bomb and asteroid.

There will be an impulse on the asteroid do to ablation caused by the radiation.

Whether that results in a subsonic wave or supersonic wave , i.e. shockwave,
depends on how strong the ablation is; but either way, there will be an impulse
delivered to the asteroid.

Dr. Gregory Greenman
Physicist

 

[Westic]

This is a thoroughly entertaining thread.
My first post.
Morbius you are definitely one of THE most patient and gracious persons on the face of this planet. LOL

 

[Sojourner01]

The primary objective, naturally, is deflection.

However, it would also be beneficial to get rid of the damn thing for good. Is it plausible to do precise enough dynamical calculations ahead-of-time in order to not only deflect an obejct from near earth, but ensure that its orbit takes it into either the sun or one of the gas giants? boy, that'd be a spectacle. Can you imagine what we'd learn from Jupiter if we could bung an asteroid the size of a small moon into it and watch what it stirs up?

 

[baywax]

Would fixing some rocket engines on to the asteroid help to deflect it? Just use a joystick to save earth. I guess the hard part would be getting on the surface with the engines, then positioning properly.

 

[Morbius]

Would fixing some rocket engines on to the asteroid help to deflect it? Just use a joystick to save earth. I guess the hard part would be getting on the surface with the engines, then positioning properly.

baywax

Depends on the orbit of the asteroid, how big it is...

Basically, it depends on how much energy would it take to deflect it, and how much
time you have.

If the asteroid is very massive, and it will hit us on its current orbit; then you may need to
put so much energy into it that NO chemical rocket could put that much energy in. There
would be NO chemical rocket that is powerful enough to deflect it.

There might even be an asteroid too massive for a nuclear weapon to deflect.

In which case, the Earh is doomed.

Dr. Gregory Greenman
Physicist

 

[Morbius]

The primary objective, naturally, is deflection.

However, it would also be beneficial to get rid of the damn thing for good. Is it plausible to do precise enough dynamical calculations ahead-of-time in order to not only deflect an obejct from near earth, but ensure that its orbit takes it into either the sun or one of the gas giants?

Sojourner01,

All depends on how much energy is required. These are massive objects, and we really
don't have a lot of energy available.

In cosmological terms; the forces of Nature at our command are pretty puny.

Dr. Gregory Greenman
Physicist

 

[Sojourner01]

Well, what I'm getting at is that assuming you can deflect the object from earth, are our computational methods precise enough to ensure that its new trajectory will put it where we want it? I'm sure the answer to this question will depend on where in the risky trajectory you choose to act - further away from Earth you don't need as much of a jolt, but that also puts it further away from its intended destination. I ask because I'm aware that astronomers can't say with complete certainty whether or not a particular object will strike us in the future; there's a 'window' limited by their ability to compute the dynamics of all the bodies involved ahead of time. Waht I'm asking is, does this inaccuracy extend to us altering the path of a large object, assuming we're practically able to?

 

[Morbius]

Well, what I'm getting at is that assuming you can deflect the object from earth, are our computational methods precise enough to ensure that its new trajectory will put it where we want it?

Sojourner01,

Oh sure to the computational methods.

Take, for instance, the Cassini mission. We had insufficient propulsion systems to launch
Cassini directly to Saturn; so it was launched in a trajectory that caused it to make TWO
fly-bys of Venus, in order to pick-up momentum via the "sling-shot" effect; before it went
to Saturn.

http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1997-061A

If we can accurately "hit" the rings of Saturn by making two "bank-shots" off of Venus;
then we can calculate how to deflect the asteroid.

Dr. Gregory Greenman
Physicist

 

[mr200backstrok]

this is a little off topic, but is there an upper limit for the yield of thermonuclear bombs?