Talk:Asteroid impact avoidance

The anti-nuclear tilt is too obvious. Maybe some Wiki-ist can resist beating the anti war drum.

"Nuclear scientists are simply trying to find new excuses to keep nuclear missiles around"

Its only the most powerful force creatable by man. I'm not sure they can make millions of tons high explosives much less get it into space.

Totally agree. These wimpy methods of placing vapor cloud in the path of an asteriod and the like are ridiculous. It's an ASTEROID for crying out loud! We are talking about cubic miles of rock here! For computationally challenged I translate - a cubic mile of rock (or even ice) weighs BILLIONS of tons.

Nice megaton-class surface or slightly above surface thermonuclear blast - that's the stuff which works. And by the way, it works not by "shattering the asteroid to pieces", but by vaporising and venting a lot of surface material, creating a rocket exhaust effect.

Again, for the computationally challenged - 1 ton thermonuclear device delivers ~6 MT blast. Delivery of such device to the asteroid is quite doable with todays launch vehicles. Deep Impact mission's impactor weighted 600 kg. —Preceding unsigned comment added by 89.102.207.196 (talk) 21:16, 9 June 2008 (UTC)

More ideas

Anyone who has read any science fiction (like me) knows about lots of other things that in theory could be done, that does not seem to be part of the near future science consideration. Would it make sense to have a "main artlce" on how this is solved in the world of Science Fiction. There is a Time travel article which reads like science thinks that is plausible, with a main article Time travel in fiction.

Examples of what I mean by solutions in Science Fiction:

• Stick eyes in the sky to see the menace long before it gets here, like a satelite on the dark side of the moon, in the equivalent of a 24 hour orbit over planet Earth where satelite in fixed point in sky. So these satelites are used to map what's coming at us from all directions, and where the risks might be, instead of risk not find out about the thing before it is right on top of us.
• Spend serious money budget to send expeditions to some of those asteroids and comets that cross earth orbit, to learn as much as we can about their composition, what it would take to divert them. We need to know as much about them, if not more, than we know about all other bodies in the solar system other than the Earth and the Sun.
• Send an expedition to the Asteroid belt, and tow some of them back here, to use as shields ... a big rock is hurtling towards us, so we take one of the shields and acelerate it up to rammming speed, at a collision angle that will take the debris away from Earth.
• There are some SF movies that involve shooting nuclear missiles at these rocks. I would like to see some scientific analysis of the validity of the "science" in those movies. If we tried that in real life, I expect that instead of a huge rock on a collision course with Earth, there would be a huge radioactive rock on a collision course with Earth.

User:AlMac|^(talk) 06:30, 30 December 2005 (UTC)

Just beautiful. You think it's plausible to "tow some" asteroids here and then "acelerate it up to rammming speed, at a collision angle" (reality check - do you have a slightest idea how much asteroids weigh??) but at the same time you think deflecting an asteroid with surface nuclear blast(s) is not? I propose you first study in depth how many letters "c" should be in the word "accelerate". —Preceding unsigned comment added by 89.102.207.196 (talk) 21:24, 9 June 2008 (UTC)

• • Hmm...with that last one- if the explosion was forceful enough, you could knock it out of its path. I'm not a scientist myself, but I have seen stuff on this. One concern is that the structure of some asteroids would absorb a lot of the blast.—The preceding unsigned comment was added by 211.30.132.2 (talk • contribs).

What about landing thrusters on it and using them to force the thing away (preferably into Jupiter or the sun, where it won't come back).—The preceding unsigned comment was added by 211.30.132.2 (talk • contribs).

You'll have to explain what you mean by "absorbing the explosion." So long as the blast hits the asteroid, conservation of momentum is unavoidable, but I guess it's possbile some might break off little pieces, and then we have a lot of little asteroids headed for the Earth. Well, getting hit with buckshot is probably better than getting hit with a tank shell, but getting hit by buckshot followed by a tank shell would probably be even more unpleasant. Someguy1221 08:40, 11 June 2007 (UTC)

"Absorbing the explosion" means that its structure will sort of crumple- but the blast won't actually stop it from moving towards us. It's sort of like punshing a really huge sponge- you can hit it all you like, it won't move.

Here is a bit of "sort of mathematics" for you. Let's say we build, send and blow up a 2 ton thermonuclear device on the surface of the asteroid. It delivers 12 MT blast. Such blast creates 4 sq.km. by 50 m crater on Earth, in other words, it ejects 200 000 000 cubic meters of material. Let's assume 1 ton/cubic meter density (water ice). Let's assume that average speed of ejecta is 1 km/s. The total impulse of so much material leaving the asteroid is 200 000 000 m^3 * 1000 kg/m^3 * 1000 m/s = 200 000 billion kg * m/s. For 6 kilometer wide water ice asteroid (mass approx 200 000 000 000 000 kg) it changes its velocity by 1 m/s. Even if my assumptions (density, amount and speed of ejecta) are seriously off, such nuke should be enough to deflect kilometer-sized objects.

If we have lots and lots of little asteroids, it might not be too bad- if they were small enough, they'd burn up in the atmosphere. You'd need to be careful that they don't smash into satellites. You coudl break it up, but personally I'd rather redirect it somewhere away from Earth. In the worst case scenario (if it was really clsoe to Earth), I'd send it flying towards the moon. It's protected us form asteroids before (though not flawlessly).

Your analysis of "absorbing the explosion" doesn't work, see conservation of momentum. Punch a sponge in the vacuum of space, it'll move. Though this is more accurately compared to throwing something at the sponge. Someguy1221 06:34, 28 June 2007 (UTC)

BTW, who was it that said that wed need ten years to prepare for a 200 m asteroid? That's ridiculous: as soon as it became apparent a 200m rock was heading our way, I reckon a few people might try and do soemthing about it.

Some here malign the gravitational tractor idea because of a perceived anti-nuke bias; however, the case for such a strategy (namely, the ability to affect 'awkward' asteroids with high spin or considerable debris clouds) seems valid. However, the gravitational force is the weakest of the fundamental forces; perhaps this deflection method could be augmented by the addition of an electron-gun/accelerator on the tractor, such that the electrostatic force could be added to the gravitational force in the tractor. I've not done even preliminary calculations on this, though, so I don't know if it could produce a usable effect.

Links

Some of the links, that I found, perhaps ought to be moved from this article on deflection strategies, to one of the related articles, that focus more on what the problems are that call for deflection strategies. User:AlMac|^(talk) 02:38, 23 January 2006 (UTC)

There needs to be a disambigous page for the asteroid named Apophis that will graze planet Earth in 2029. User:AlMac|^(talk) 06:29, 23 January 2006 (UTC)

Separate sections or main articles

I think there may need to be

1. Separate article on this topic in Science Fiction.
2. Separate article on the public relations angle of
   1. Each time one of these is discovered, the news media cries "wolf" making it sound like the scientists do not know what they talking about. Then as the scientists get more and more info, getting better and better estimates, and the news media reports this, it sounds like they did not get it right the first time.
   2. By the time the human race is really threatened, the voting public will be so used to each news story being worse than the last story, then turning out to be nothing, that we humans will not take the real thing seriously.
   3. There are also political issues. Suppose an effort by nation-A to deflect fails, and nation-B gets hit. Assuming nation-B survives, what kind of liability is nation-A facing?
3. We have various strategies proposed. What we do not have are the major pros and cons of each strategy. For which of them does the technology exist? What kind of expense?
4. I saw that Carl Sagan had said that developing some of these strategies was potentially more dangerous than the threat they protecting against. Can we get the specific quote?
5. Are there other efforts in space which, if perfected in time, can also help with the flexibility of solving this one?
   1. For example space elevators could make it more inexpensive to get the anti-asteroid weapons and fuel to escape earth orbit.
6. Time Line{s) ... there may already be relevant wiki articles ... if so need to link with this, if not perhaps need to add some
   1. Significant historical impacts when, sequenced not chronologically but from greatest damage or potential threat, to less of a risk of harm. We can then see clearly how often planet Earth is placed at risk by impacts of various severity.
      1. Indicate how much damage they would have inflicted had they arrived in a major city, rural area, ocean strike, other terrain.
      2. Number of Near Earth Objects of comparable or larger size, and frequency with which they cross Earth orbit, so we can see the rate at which we are playing this cosmic Russian roulette.
   2. Human understanding has dramatically evolved in a relatively short time span. When I was in college in the 1960's there was a cover story in an Analog Science Fiction and Fact magazine on Giant Meteor Impact which identified scars on surface of planet Earth from prior impacts and compared their energy signature with major volcanic eruptions, such as Krakatoa. An ocean strike was considered worse than a land strike because of risk of penetrating the magma on ocean floor and punching a hole in the planet's crsst, with a super volcano coming back out of it, triggering the mother of all tsunamis. In the 1960's the whole idea of extinction impact was science fiction to most people, even though the race to the moon was on, and anyone who looks at the moon can see that it has been plastered, the idea that the Earth had also been plastered, was just not what a lot of people willing to believe.
   3. Do we really know if the risk is about the same over time? As global warming contributes to sea level rise, human habitation becomes more at risk to risk of damage from giant tsunamis.
   4. Spaceguard existed on a volunteer basis around the world long before US Congress gudgeted funds, after many years of ignoring USAF budget requests for planetary defense. Other nations, equally slow to respond to their relevant experts requests.

User:AlMac|^(talk) 07:49, 23 January 2006 (UTC)

Panic Now!

This could be an interesting article, full of pros and cons of existing or near-future technology plus speculative solutions. But unfortunately, a good portion of the article is already littered with sensationalistic "it could happen tomorrow!" kind of fear mongering. Perhaps, according to someone's math, it is more likely to be killed by a falling asteroid than die in a plane crash, but they both still have a very, very low probability. So comparing them is somewhat silly. (IMHO) I think we should reduce the "likelihood of an impact" and "effects of an impact" topics no more than one paragraph each and spend most of the article dealing with the stated topic. –Shoaler (talk) 19:52, 24 January 2006 (UTC)

I plead guilty to adding content to show that there is a definite risk out there, against which the planet needs to defend itself. I feel that such content belongs someplace in Wikipedia, but perhaps in other articles. I do not have a good feel for all the related articles that do exist, where the timeline may belong, and was contemplating other main article(s) where some detail could subsequently be transferred to. User:AlMac|^(talk) 12:38, 25 January 2006 (UTC)

Why was this removed by User 149.159.98.46 ?

Asteroid Gravitational tractor

- NASA astronauts Edward Lu and Stanley Love have proposed using a large heavy unmanned spacecraft to pull an asteroid into a non-threatening orbit. Here's one article about their proposal. The craft was originally designed for another mission, uses electric thrusters, using electric power to heat a gas to extremely high temperatures and squirt jets to the sides of the asteroid, not directly at it, which would undermine the desired gravity tug boat effect, maintaining a constant close distance so gravity can do its work. By using gravity to pull the asteroid, this can save us from near earth objects that have the consistency of piles of rubble, which if detonated just changes distribution of the rubble still headed towards us, or high rotation that is difficult to mount a pusher on. The gravity tractor would have to spend approximately a year beside the asteroid to be effective.

Dawn: ~1 ton, total dV 11000m/s (achieved in 2000 days of thrusting). If we impart the same impulse onto 1 cubic km asteroid with density 1 ton/m^3 (density of water) by making Dawn-like spacecraft to hover upon it as described, velocity change will be something like 0.000011 m/s, or 0.011 mm/s. This is after ~5.5 years of "gravity tracting". Give me a break. 89.103.91.47 (talk) 17:14, 22 June 2008 (UTC)

I had originally started this writeup, then added to it, since I felt it was a notable effort by NASA scientists, reported in believable media, that was different from the write-ups that I found in the other solution strategies. User:AlMac|^(talk) 00:26, 25 January 2006 (UTC)

Thanks, I see that someone has put the section back in, and phrased it much more elegantly than I had, but dropped the citations proving that the content is truth. User:AlMac|^(talk) 12:33, 25 January 2006 (UTC)

Why was this removed by User:149.159.102.7 ?

Gravitational Tractor

- Proposed by NASA scientists Edward Lu and Stanley Love, this plan calls for a huge, ~20 ton spaceship to hover near the asteroid, years before it comes close to hitting Earth. With the heavy end of the spaceship facing the asteriod, this should be enough to "pull" the asteriod into a slightly different orbit, that years later will save earth.

This more elegant write up, without the earlier citations and additional detail, was also removed. I hope it was removed for improved re-write. User:AlMac|^(talk) 01:13, 29 January 2006 (UTC)

As I commented above, the idea is ridiculous and is probably born out of irrational fear of using nuclear bombs for quick and efficient asteroid deflection. 89.103.91.47 (talk) 17:18, 22 June 2008 (UTC)

What about comets?

They pose a threat too. Perhaps this article needs to be moved to Meteor deflection strategies? --Revolución (talk) 03:39, 29 January 2006 (UTC)

• Actually, the sad fact is that most experts think comet impacts are essentially unpreventable, because their orbits would generally give almost no warning beforehand. You know, that should probably be in the article...--Pharos 19:07, 4 February 2006 (UTC)

Trampoline

Nice try, anonymous :) Please put it back in iff you find a source... University of Queensland devised a plan utilising advanced polymer technology in 2005. The polymer-metal compound produced is engineered into several giant tensile springs, each approx 1km in length. They are then assembled to a trampoline megastructure designed to bounce the incoming comet back out to space upon impact. Some speacialists suggest having several people simultaneously jumping on the surface of the structure could help to "super-bounce" the comet with even greater force. --DerHerrMigo 14:40, 2 February 2006 (UTC)

Yet another bogus strategy

I may be over-zealous this time, but I can't quite believe this would work: Creating an artificial debris cloud in the object's path so that upon impact the object will be deflected. You'd need one helluva lot of debris - where do you take that from? --DerHerrMigo 20:23, 3 February 2006 (UTC)

I tend to agree with you. As phrased, that won't work. A debris field sounds like a rubble pile, which can cause same kind of damage.

• The gravity tractor idea does not need a regular space craft, but it does need propulsion attached to the gravity source.
• Another asteroid, captured, attach space drive, then use that a number of ways, depending on how good precision of aiming. It is like shooting a bullet with a bullet. Can we do that with ABM technology, or does that really mess up the electronics of incoming missiles, and not truly have bullet hit bullet.

User:AlMac|^(talk) 10:50, 4 February 2006 (UTC)

Nice new article & nice new strategy

http://www.popsci.com/popsci/aviationspace/da8309cdd1919010vgnvcm1000004eecbccdrcrd.html Could someone update wiki? The main idea is using gravitational force. They claim that it would be possible to slightly change trajectory of 50 million tons asteroid named 99942 Apophis(1 to 10000 chance to hit an Earth in 2036), if they could sent spacecraft by year 2029... They mention Russian Federal Space Agency; U.N. Office for Outer Space Affairs; JSR Space Report, article looks serious. TestPilot 06:07, 10 February 2006 (UTC)

I added this theory some time ago, with multiple links to show it was a valid theory from notable people, but other volunteers here kept deleting that material without good explanation. I not want to get in an edit war, so I leave it to consensus what belongs. User:AlMac|^(talk) 05:08, 11 February 2006 (UTC)

Hmm... TestPilot 07:55, 11 February 2006 (UTC)

I reinstalled that paragraph. I checked history - first it is not a volunteers, just one anonym. Looks like he simply do not understanding idea and do not believe in that strategy. And do not bother to check sources. And, now I noticed that Gravity Proposal was mentioned here(discussion page), and there was no need to create new section - totally mine fault. TestPilot 08:28, 11 February 2006 (UTC)

Hey guys - I'm glad you put that back in! I've reworded the section quite a bit, making it (hopefully) easier to understand; hope you like it. It could still use some 'polishing' by a native speaker, though... --DerHerrMigo 18:00, 11 February 2006 (UTC)

Yeah, thanx. I absolutely love your edit - it way more understandable now. TestPilot 20:34, 11 February 2006 (UTC)

Terminology

The word program is used on more than one occasion in this article. To assist people whose first language might not be English I propose that program be used to descibe a computer program, and programme be used to describe a series of events. Arcturus 12:11, 12 February 2006 (UTC)

The word program existed long before computer programs came along, and with the rise of computers, continued to be used quite heavily in many contexts unrelated to computers, such as

• government program
• project program
• convention or conference program

Perhaps it would be more relevant to ask about spelling in different English speaking nations. I think programme is British while program is American, but how is it done in Australia, India, and elsewhere, particularly the nations that have active space programs (or is that space programmes?), and thus likely to have constructive contributions to this subject. User:AlMac|^(talk) 10:34, 14 February 2006 (UTC)

Yes, it might boil down to different versions of English. Here in England, the usage is as I described, with program always being used to refer to a computer program. Therefore it's quite easy to understand the context (it's easy anyway for native English speakers, of course). I think in America programme is not generally used in any context. However, maybe we should think about the alternative spellings as a way of differentiating the usages. Arcturus 17:20, 14 February 2006 (UTC)

English is a second language for me. And I have never before saw(noticed?) use of programme word. Program is way more popular - Google give 5,050,000,000 results vs 560,000,000 for programme and more understandable. Lets keep it simple. But i live in Canada, so i got "chequing account" in my bank and I live not far from "Chinatown centre". So there is some differences. TestPilot 05:23, 15 February 2006 (UTC)

Fiction section

Deep Impact based on Arthur C. Clarke novel Hammer of God?

Only very, very loosely. If at all. See The Hammer of God#Film_connection and Deep Impact (film)#Source_material_alterations --Dmtipper 17:56, 6 May 2006 (UTC)

Political dangers?

Referring to this paragraph from the article:

“The dangers posed by such collisions go beyond the physical destruction caused by the impacts themselves. A nation hit by less than extinction-destructive force may, depending on their military political situation, think they are being attacked by another nation and retaliate. If this had happened to a superpower during the Cold War, it may have thought it was under nuclear attack and "returned" fire.”

I think this paragraph/rambling should be deleted: it reads like someone thinking out loud, and makes little sense. A nation hit by a massive asteroid impact will not confuse it with a nuclear attack due to, among other things, the singularity of the impact (as opposed to several smaller warheads), the lack of radioactivity, the lack of any detectable delivery methods (no planes or missiles), the magnitude of the explosion, and the knowledge, even if gained only a few hours prior to the impact, that an asteroid impact is imminent. This adds no value to the article.

Ron g 16:54, 24 July 2006 (UTC)

be bold!

and fix it ! ;>Xenocidic 16:15, 31 July 2006 (UTC)

2 edits

1. The 'social problems' aspect appeared quite biased as holding the whole endeavour as a waste of funds. Gramatically, it was quite rambling as well. I believe I remedied both. I would prefer to make more sweeping changes, but I do see the utility of the viewpoint.

2. I added a portion to mitigate against the view that our detection strategies are (or soon will be) 100% efficient. At the very least, asteroids can have an approach plane which keeps them blocked by the glare of the sun, and that leaves them currently undetectable.

The 1972 Near Impact Event

---

Not disputing it, but I'd imagine something of this significance would be easier to obtain sources for. Anyone got anything more concrete?

See [1] and its references. The event did occur, but the size quoted in the article is exaggerated. The above web site refers to size estimates from 3 to 80 m in diameter, with impact energies (had the object hit straight on) being "Hiroshima-sized" at the lower end of that size range. --mglg_(talk) 22:31, 5 January 2007 (UTC)

Project Icarus

I changed 'Icarus Project' to 'Project Icarus' which is the actual name of the book. Someone probably wants to create a page for it - there are good details here http://www.thespacereview.com/article/175/1

Not that anyone will care, but

I came up with the solar sail proposal in 2004, and sent it to NASA. I never received a reply email, but I've seen this scenario posted at a couple of different discussion groups. I'm not sure if I should be pleased, or pissed that I was never credited with the original idea. I guess my small claim to fame, if it helps everyone, should be just that. A small claim. I just hope it works if they go to use it. -Tercero

Does anyone mention?

Does anyone think that a nuclear explosion, but a miscalculated one, will send smaller radioactive asteroid pieces to Earth instead? Should this be adressed as a "con" for nuking the asteroid? Brandonrush 22:39, 13 March 2007 (UTC)

Popular strategies

Per WP:OR, theories should be published to be included here. A link to a researcher's personal homepage isn't a sufficient citation.

Also can someone clarify this sentence:

If not completely vaporized, the resulting reduction of mass from the blast combined with the radiation blast could produce positive results.

—Kymacpherson 13:31, 15 April 2007 (UTC)

Having a less massive asteroid hit the Earth would most certainly be positive, but I have no idea what good a radiation blast does, besides possibly putting us out of our misery when we're not expecting it  ;-) Someguy1221 08:43, 11 June 2007 (UTC)

+++ Oberth/Tsiolkovsky/Goddard meet Faraday/Henry/Weber/Maxwell ++ Electro-magnetic Field Reaction Propulsion and Electro-dynamic Induction Braking in Space Applications. – By Mark J. Carter

Space propulsion has changed little since mankind took its first tentative steps into space. Even with the incremental advances in the efficiency of chemical fuels; the basic nature of rocketry is still defined by the basic Delta V Rocket Equation with all its limitations; be it the powerful boosters used to obtain orbital velocity or the low impulse Ion Thrusters used to power deep space missions. This ancient approach to propulsion limits both the potential flight parameters of deep space missions and the life span of earth orbiting satellites.

In earth orbiting satellites, the electronics of the satellite may last indefinitely; but the useable lifespan of that satellite is limited by the availability of on-board propellants used for orbital maintenance. Once the chemical propellant is exhausted, the satellite no longer has the capability of maintaining proper station.

The International Space Station is dependent upon chemical propellants to offset orbital decay. The need and use of these chemical propellants increases the potential for catastrophic accident, increases the cost of operational maintenance, and requires the commitment of launch capacity for that purpose.

Interplanetary and deep space missions face similar limitations inherent to dependence on chemical propellants. Although gravitational assist has been a regular tool used in both navigation and imparting changes in specific orbital energy; obtainable velocities, launch windows, and other flight parameters remain severely limited by dependence upon the same Newtonian Propulsion methods used by the ancient Chinese to power their rudimentary rockets. Even Ion Propulsion, which uses electro-magnetic acceleration of the ion fuel to achieve impulse, is still a type of Newtonian Propulsion where the total energy imparted is limited by exhaust velocity and total available fuel mass; as defined by Tsiolkovsky's rocket equation. Newtonian Propulsion may have gotten us to earth orbit and beyond; but it will be Electro-magnetic propulsion that will carry us to the stars. In the mean time, its development will allow us to achieve flight parameters unimaginable when considering only chemical propellants.

The Ampere Defined As Magnetic Force:

Prior to 1948 the ampere was defined, based on Faraday’s Law Of Electrolysis, as the amount of unvarying current, that when passing through a solution of silver nitrate, deposits silver at a rate of .00111800 grams per second.

The ampere was redefined in 1948 as the amount of unvarying current, that when being carried by two infinitely long conductors separated by one meter, would generate a magnetic force between the conductors of 2 X 10-7 Newton per meter of length. This is the Standard International definition of an Ampere.

Electro-magnetic Field Reaction Propulsion and Electro-dynamic Induction Braking when combined with the now and near term future technologies related to super conductivity and other related technologies will introduce a new paradigm in space propulsion.

The Fundamentals Described As A Space Based Experiment:

A simple space based experiment to demonstrate the basic principles of electro-magnetic propulsion is easily imagined. In this experiment a simple coil, a number of accelerometers, a polarity reversing switch, power source, and radio telemetry is used to determine the earth’s electro-magnetic field strength at the range of the experimental package. It would be most advantageous if the coil length is as great as possible. The coil is circuited in series with the polarity reversing switch and the power source. The accelerometers serve to activate the polarity reversing switch. The experiment is then suitably packaged and conventionally launched to a low inclination orbit defined by the optimum induction flux angle. The experimental package is then positioned so that the field coil of the package is aligned so the coil will be at maximum repulsion with earth’s electro-magnetic field when the coil circuit is initially energized.

So positioned, when the switch is initially closed and power is applied to the coil there will be two vector forces acting on the coil.

Since the coil is aligned in repulsion with earth field, one force will be acting along a line that is perpendicular to the earth’s North/South polarity (approximating the line of orbital radius) and will translate to an acceleration vectored along the orbital radius converting circuit energy to increased gravitational potential.

The other force acting on the field coil will translate to torque causing the field coil to begin to rotate about the central axis of the coil length as it begins to align towards the magnetic equilibrium position relative to earth field; that being one of maximum attraction and 180 degrees relative to the maximum repulsive position. In doing so, some of the electrical energy supplied to the field coil will be converted to kinetic rotational energy of the package. As the field coil rotates towards the equilibrium position, the accelerometer reading acceleration along the line of the orbital radius will sense zero acceleration as the angular relationship between the field coil and the earth’s North/South polarity reaches 90 degrees relative to the maximum repulsion or attraction position. The coil polarity control circuit is designed to reverse the polarity of the field coil at this position, thus maintaining a repulsive relationship as the rotational inertia carries the coil package through the 90 degree position.

The timing of the polarity reversing switch is critical for maintaining repulsion; avoid dampening the oscillation, or allowing the package to continue increasing its spin velocity.

As power is applied to the circuit, energy begins to be converted thru linear and rotational acceleration to the gravitational and rotational energy of the package. Without empirical proof, I suggest that the applied coil circuit energy will be the sum of the energy translated to gravitational potential and rotational kinetic energy. That the linear force acting along the line of orbital radius will vary as the cosine of the relative field angle while the force translated to torque about the center axis of the coil will vary as a sine function of the relative field angle. The linear force will approximate the force at 0 degrees (maximum repulsion) times the cosine of the relative field angle. The force imparting torque about the center axis of the field coil will approximate the force imparting torque about the center axis of the field coil at 90 degrees (maximum torque) times the sine of the relative field angle.

Where the moment of inertia of the experimental package is known, Earth’s Electro-Magnetic Field Strength can be derived from acceleration and circuit power.

Attitude Determination and Control Applications On Board Earth Based Satellites:

Using the Earth’s magnetic field as a reaction field in attitude determination and control of earth orbiting satellites was first proposed early on in space science applications history. Current applications include the sensing of relative field angle to determine satellite attitude and the use of electro-magnets to maintain and change satellite attitude. The author believes that widespread application may be limited by the orbital perturbation that would result from earth field/satellite field interaction. Electro-magnetic attitude control, without an Electro-magnetic orbital maintenance regime, would require expenditure of thruster fuel to maintain orbital station. To make electro-magnetic attitude determination and control a viable application, a means of offsetting the orbital perturbation using electro-magnetic propulsive technology rather than chemical thrusters must be developed. Also, the mass and volume fractions of electro-magnetic attitude determination and control technologies must be brought to values where the advantages of the technology offset the mass and volume fractions required. A primary advantage of Electro-magnetic propulsive methods for this application is that it can be accomplished without the complex mechanical components as required in momentum and reaction wheel technology or the fuel and valving required for thrusters. This resulting increase in reliability will serve as further incentive to apply electro-magnetic technology to attitude control.

Increasing Hyperbolic Excess Speed in departure from Earth’s sphere of gravitational influence:

By definition, for an Earth orbital escape mission, the Hyperbolic Excess Speed is the residual speed that remains as the space craft climbs out of the Earth’s gravity well. Simply stated, it approximates the rocket burn out velocity minus the escape velocity at the range of burnout.

It may be possible to increase the Hyperbolic Excess Speed by using magnetic repulsive force generated by propulsion coils aboard the spacecraft acting against Earth’s electromagnetic field. The repulsive force would offset the deceleration of gravity as the space craft moves out of the Earth’s gravity well. This offsetting force would leave more residual or “Hyperbolic Excess Speed” as the space craft leaves the gravitational sphere of influence. If the magnetic repulsive force exceeds the gravitational force, then this force would continue to accelerate the space craft. The additional energy imparted would approximate the applied circuit energy calculated as applied power times time.

By thoughtful design, repulsion can be maintained without using an oscillating polarity strategy (as described in the Space Based Experiment), thus maintaining constant space craft attitude.

Increasing Hyperbolic Excess Speed in Gravity Assist Maneuvers:

A number of deep space missions have used Gravity Assist to either increase or decrease the mechanical energy of the space craft. Although such maneuvers use the gravitational acceleration of the assisting planet to increase or decrease the heliocentric relative velocity of the space craft, the Hyperbolic Excess Speed of the space craft relative to the assisting planet remains unchanged. The reason for this is the relative velocity between the space craft and the assisting planet gained by the acceleration of gravity on the approach trajectory is lost to that same gravitational force on the departure trajectory.

By using Electro-magnetic Field Reaction Propulsion, both additional hyperbolic excess speed relative to the assisting planet and heliocentric relative velocity can be imparted when the assisting planet has a significant magnetic field. In this application the propulsion coil(s) are used in attraction polarity on the approach to the assisting planet. This increases the acceleration above that imparted by gravity alone.

As the space craft begins its departure trajectory from the assisting planet, the relative polarity is reversed and maintained in repulsion. This offsets the deceleration imparted by gravity, and increases both the Hyperbolic Excess Speed of the spacecraft relative to the assisting planet and the Heliocentric Velocity; by adding the energy imparted by the electro-magnetic system to the specific mechanical energy of the space craft.

If desired, the inverse process could be used to decrease spacecraft energy.

Orbital Station Maintenance and Altering Eccentricity:

By using properly timed Electro-magnetic Impulse, in repulsion and in attraction, possibly combined with Electro-dynamic braking; total orbital energy and eccentricity of orbit may be altered. Conceptualization of this regime involves both magnetic impulse and dynamic-braking at specific points in the orbit and could include using the induced dynamic-braking energy to produce vectored magnetic impulse.

Orbital Energy, often described as “The Specific Mechanical Energy”, has two components. These are the kinetic energy per unit mass and the gravitational potential per unit mass. The sum of these two variables equals the specific mechanical energy. In a mass constant orbiting object, when not acted on by any other force than the gravity of the prime focus object; this Specific Mechanical Energy remains constant. In elliptical orbits this energy translates between kinetic energy and gravitational potential energy.

Introductory texts on Astro-dynamics teach that in most cases, a change in the Specific Mechanical Energy of a satellite is accomplished by imparting impulse along the velocity vector. This change in velocity translates to a change in the semi-major axis of orbit. By imparting impulse along the velocity vector the Specific Mechanical Energy can be either increased or decreased with the timing of the impulse relative to periapsis or apoapsis determining orbital eccentricity. Changes in apoapsis are made by imparting impulse at periapsis while impulse to change periapsis is imparted at apoapsis.

In both cases, the impulse either increases or decreases the total orbital energy by imparting a change in orbital velocity. This change in velocity is then translated to a change in gravitational potential by altering the semi-major axis.

It is proposed that changes in the orbital energy of the space craft can be made using Electro-magnetic technology; increasing the orbital energy by increasing the semi-major axis directly through repulsive interaction with earth field or decreasing orbital energy by electro-dynamic braking.

In a properly inclined orbit, generating a magnetic field in repulsion with earth field will begin to impart impulse along the orbital radius, increasing the semi-major axis, thus directly increasing the gravitational potential component of the Specific Mechanical Energy. By imparting magnetic impulse during the entire orbital period, or applying bit impulse relative to apoapsis and periapsis, the orbit can be stepped up and eccentricity controlled. If using conventional chemical propellants, stepping up the orbit is accomplished by increasing the velocity component, translating to gravitational potential, with the impulses timed relative to apoapasis and periapsis to control eccentricity. Experimentation with generating magnetic field in attraction to earth field may yield some surprising results. How will the circuit energy be conserved?

Electro-magnetic Induction Braking (Electro-dynamic Braking) of the space craft will impart a braking force along the vector of orbital velocity, decreasing the orbital energy, and translated to a reduction in gravitational potential. By timing the Electro-dynamic braking inputs relative to periapsis and apoapsis the orbit can be stepped down and eccentricity controlled. Using chemical propellants stepping down the orbit is accomplished by impulse opposite the velocity vector, slowing the spacecraft. The timing of braking impulse relative to periapsis and apoapsis will allow control orbital eccentricity.

Electro-dynamic Induction Braking:

All electro-magnetic induction processes are composed of three primary components; the excitation field, the inductor, and rate of change. The rate of change can be supplied by velocity of the inductor relative to the excitation field, the oscillation of the excitation field in the presence of the inductor, or combination of the two.

For those of you who may have had the opportunity to empirically experience the fundamental physics of induction through experimentation with a simple hand crank generator, that lesson showed the relationship of circuit load to cranking force, and can be extrapolated to the inductive braking of a satellite or asteroid.

In Electro-dynamic Induction braking applications the solar or planet field will provide the excitation field while coils aboard the spacecraft, or the spacecraft/asteroid body itself, serves as the inductor. The spacecraft/asteroid velocity cutting the flux lines of the Solar or Planet field will supply the rate of change component. This induction process will generate a braking force as is inherent in any electro-magnetic induction process. The induced energy will then be dissipated through circuits designed to generate heat for radiative dissipation, conversion to vectored propulsive impulse, or stored for peak power/subsystem applications. Applications of Electro-dynamic braking will include adjustments in semi-major axis and eccentricity; as well as braking to orbit in planetary missions.

Because the orbital velocity of a satellite or asteroid is so high, significant voltage can be developed even though the excitation field may be very weak. The “tether” experiments flown on the space shuttle clearly indicate the validity and potential application of this technology.

Imparting Orbital Escape Energy:

Escape speed, as given in reference material, gives the escape speed at the surface of the body referenced. This escape speed decreases as the radius of orbit increases. If an orbiting spacecraft is given continual magnetic impulse to step up the orbital radius, at some point, the orbital velocity of the spacecraft will approach and then exceed the escape speed at range, thus allowing the spacecraft to “escape” the gravitational sphere of influence of the prime focus body (planet or Sun). Using such a method, a satellite may be given Excess Hyperbolic Speed, not by imparting additional velocity, but by imparting additional gravitational potential until the energy of the spacecraft exceeds that needed to escape the gravitational sphere of influence of the prime focus body.

By initiating high power Electromagnetic impulse in low earth orbit and maintaining this impulse during the outbound trajectory, very high Excess Hyperbolic Speeds might be achieved.

Braking to Orbit:

A space craft approaching Jupiter, or other target body, may have too much energy to establish orbit. By using Electromagnetic Propulsive methods it may be possible to alter both the magnitude and vector of the approach velocity; thus giving an alternative to using chemical propellants or atmospheric braking as the sole methods of reducing the energy of the spacecraft so that it can be captured by the intended prime focus body.

Deep Space Propulsion and Navigation:

Force vectoring will be obtained by very precise control of field strength, field angle, and action time relative to the reaction fields of planets having significant field, the Sun, and once beyond the heliopause; the galactic field. Vector control, when within the magnetic sphere of influence of multiple field sources; will utilize the relationship of reaction field range, reaction field angle, and time span of power input to sum the force vectors from two or more reaction fields to obtain the desired net force vector. An example would be to act in repulsion of earth field for a fixed time at a fixed power and then act in attraction to Sun field for a fixed time at a fixed power. The net vector force would be the vector sum of the two forces. Because of the cosine relationship of repulsion/attraction force to the relative angle between the propulsion coil(s) and fields of the Sun, Earth, Jupiter, or other reaction fields, and if those fields are offset at a substantial angle relative to each other; effective impulse vectoring can be accomplished.

In Closing:

The Delta V imparted by a chemical rocket is limited by the attainable exhaust velocity of the rocket and total fuel mass available. In an Electro-magnetic Field Reaction Propulsion System capable of generating extreme field strength, the Delta V imparted will be limited only by the amount of available applied electrical power and the time span that power is made available.

In all cases, the minute field strengths of the reaction fields at range become usable when the propulsion system is capable of generating extremely strong fields or, in the case of dynamic braking, the induction circuit is capable of maintaining extremely high acceptance when dissipating high power.

The use of Electro-magnetic Propulsion may negate the requirement of waiting for opportune alignment of Jupiter and Saturn for use in Gravity assist maneuvers. The launch windows now continuously open by the ability to use Solar Field in repulsion to give the space craft the kick up that would otherwise require a gravity assist trajectory or maneuver.

A most important ramification of Electro-magnetic Field Reaction Propulsion and Electro-dynamic Braking in Space Applications may be the fundamental change in the logistics of asteroid deflection. This technology will negate the need to carry chemical fuel mass to the asteroid for the purpose of supplying impulse. It will allow mankind to use the orbital energy of the asteroid itself as the prime source of energy for deflection through an integration of Electro-dynamic braking, vectored electro-magnetic impulse, and for powering Newtonian Propulsion Systems that use scavenged mass from the asteroid and accelerate it using propulsion coils. Perhaps, it will cause a re-evaluation of the decision to use nuclear explosive deflection and fractionation as the preferred approach to this impending challenge.

--Mark J. Carter 23:42, 23 September 2007 (UTC)

Has this been published? Someguy1221 02:28, 24 September 2007 (UTC)

fiction overlap

The subsection "fiction" on this page overlaps with, but is less exhaustive than, the fiction section in Asteroids in fiction (Asteroids in fiction#Collisions with Earth). Should these be condensed to a single article on asteroids colliding with Earth in fiction, instead of two? Geoffrey.landis 20:43, 4 October 2007 (UTC)

Fair use rationale for Image:Deep Impact poster.jpg

Image:Deep Impact poster.jpg is being used on this article. I notice the image page specifies that the image is being used under fair use but there is no explanation or rationale as to why its use in this Wikipedia article constitutes fair use. In addition to the boilerplate fair use template, you must also write out on the image description page a specific explanation or rationale for why using this image in each article is consistent with fair use.

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BetacommandBot (talk) 21:09, 13 February 2008 (UTC)

What do you think?

In the section "Poplular strategies" it says "Destruction concentrates on rendering the impactor harmless by fragmenting it and scattering the fragments so that they miss the Earth or burn up in the atmosphere. As will be shown, this does not always solve the problem, as sufficient amounts of material hitting the Earth at high speed can be devastating even if they are not collected together in a single body." It never dose explain that and I was wondering if we should explain why it makes the problem a hundred times worse. Skeletor 0 (talk) 16:35, 5 September 2008 (UTC)