Russia to send spacecraft to knock Apophis off course?

[cyclonebuster]

So I will pass on your not so generous offer thank you very much!

I suspected that you would And it was actually quite generous, to spend an hour of my precious time showing that your idea had no merit.

What method of deflection did you use during your calculations? :idea:

 

[MeteorWayne]

I haven't spent the time to do them, since you refused my offer. You do the work!

 

[cyclonebuster]

I haven't spent the time to do them, since you refused my offer. You do the work!

LOL! You said: "And it was actually quite generous, to spend an hour of my precious time showing that your idea had no merit." Which means you spent an hour to do calculations? Which method of deflection did you use?

 

[cyclonebuster]

Notice each projo. that is shot has a recoil effect to the structure base! "The recoil force exerted on the rails is equal and opposite to the force propelling the projectile."


Theory and construction
A railgun consists of two parallel metal rails (hence the name) connected to an electrical power supply. When a conductive projectile is inserted between the rails (at the end connected to the power supply), it completes the circuit. Electrons flow from the negative terminal of the power supply up the negative rail, across the projectile, and down the positive rail, back to the power supply.

This current makes the railgun behave as an electromagnet, creating a powerful magnetic field in the region of the rails up to the position of the projectile. In accordance with the right-hand rule, the magnetic field circulates around each conductor. Since the current is in opposite direction along each rail, the net magnetic field between the rails (B) is directed vertically. In combination with the current (I) across the projectile, this produces a Lorentz force which accelerates the projectile along the rails. There are also forces acting on the rails attempting to push them apart, but since the rails are mounted firmly, they cannot move. The projectile slides up the rails away from the power supply.

A very large power supply providing, on the order of, one million amperes of current will create a tremendous force on the projectile, accelerating it to a speed of many kilometres per second (km/s). 20 km/s has been achieved with small projectiles explosively injected into the railgun. Although these speeds are possible theoretically, the heat generated from the propulsion of the object is enough to erode the rails rapidly. Such a railgun would require frequent replacement of the rails, or to use a heat resistant material that would be conductive enough to produce the same effect.

[edit] Considerations in railgun design
[edit] Materials
The rails and projectiles must be built from strong conductive materials; the rails need to survive the violence of an accelerating projectile, and heating due to the large currents and friction involved. The recoil force exerted on the rails is equal and opposite to the force propelling the projectile. The seat of the recoil force is still debated. The traditional equations predict that the recoil force acts on the breech of the railgun. Another school of thought invokes Ampère's force law and asserts that it acts along the length of the rails (which is their strongest axis).[5] The rails also repel themselves via a sideways force caused by the rails being pushed by the magnetic field, just as the projectile is. The rails need to survive this without bending, and must be very securely mounted.

 

[MeteorWayne]

No, the offer was generous, which you refused. So I did not spend the time. If I have some to spare in the next few days, I'll do it for my own curiousity. When I have the time to spare.

 

[cyclonebuster]

No, the offer was generous, which you refused. So I did not spend the time. If I have some to spare in the next few days, I'll do it for my own curiousity. When I have the time to spare.

Your offer was not reasonable for a moderator to try and quell an active participant to a blog.

BTW
"The recoil force exerted on the rails is equal and opposite to the force propelling the projectile."

 

[cyclonebuster]

Pssst! Me thinks MeteorWayne is doing calculations now since his curiosity has peaked! What say you guys? :lol:

 

[cyclonebuster]

In theory you could do the same with a straw and some spit balls if the asteroid had an atmosphere where we could breath!

 

[MeteorWayne]

MOD HAT ON***

Please lets stick to the topic here. If anyone wants to discuss the offer of my effort or anything related, use the PM function.

MOD HAT OFF****

 

[MeteorWayne]

I would STRONGLY suggest that anyone discussing the Apophis issue read the full B612 paper available here:

http://www.b612foundation.org/papers/wpdynamics.pdf

If you have not read it, you are not informed about what they actually said, including the map posted above.

I could post some excerpts, but it would be better if anyone involved in the discussion read the whole thing first.

MW

 

[silylene]

MW, good paper, thank you. I had not read this one.

 

[Boris_Badenov]

Hey Boris, what is the map supposed to represent?

Possible impact effects
It came from this Wiki page.

 

[silylene]

The map actually came from the article that MW linked. The track is surprisingly narrow, if you read the paper.

 

[R1]

Yes, well we do have to probe it, it seems. Someone needs to dock some probes and transponders to it.
While they attach transponders to it, I would like to see some additional radar mapping instruments on it,
wouldn't it be nice to have Apophis run some radar maps during the times when it is on the opposite
side of the Sun, at the Earth's doppleganger region?

And I figured the U.S. doesn't have the fuel to be running around the solar system trying to catch up to dozens of
asteroids. Hopefully international Public Safety funding will be made availabe for the nuclear-electric propulsion
briefly mentioned. Is that the same thing as the Prometheus project which died from lack of U.S. money to
fund it? Or was it a different propulsion type?

Finally, I think Earth should deploy a few satellites to help in the live tracking of these PH objects. I don't
mean satellites orbiting the earth, but rather two or three satelites at various equidistant locations along
Earth's path around the Sun. In other words, satellites at or near the monthly earth's location in January, April,
and August, for example. Wouldn't this be helpful in securing a quality, live, and permanent communications link to
all and any PH object probes?

 

[Buzzz]

I would STRONGLY suggest that anyone discussing the Apophis issue read the full B612 paper available here:

http://www.b612foundation.org/papers/wpdynamics.pdf

If you have not read it, you are not informed about what they actually said, including the map posted above.

I could post some excerpts, but it would be better if anyone involved in the discussion read the whole thing first.

MW

Mr. MeteorWayne, My first post.
What if it misses us in said year and hit Venus like this trajectory suggests? Can anyone confirm this??

http://media.silive.com/weather/photo/99942-apophis-x1gif-ffa4ef48b04b41eb_large.gif

 

[MeteorWayne]

Hi Buzzz, welcome to Space.com

I don't think it comes as close as it looks like in that image; it's kind of a side view from an angle. Unfortunayely, I couldn't find anything out about how that image was created like what angle above the plane of the solar system it represents, or what date it shows the planetary positions.

The NEODyS website lists no close appraches to Venus through 2090, and they are pretty good about that.

The JPL Sentry site does show a close approach at .07 AU (still quite far away, about 30 times our distance to the moon) in 2016, and one in 2024, of 0.12 AU; but that list doesn't appear to extend past the 2029 close approach to earth.

http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=9 ... ;cad=1#cad

That kind of makes sense, since that very close approach to earth in 2029 will significantly change the orbit...anything beyond then has very low confindence, which is why there remains the very small risk (again, 1 in 233,000 or so) of an earth impact in 2036.

Wayne

 

[Fallingstar1971]

What should happen is a flurry of instruments being sent to this asteroid to ride its orbit. With it passing as close as it is, it would be a wonderful opportunity to hitch a ride. We can learn many things. Lets not waste the opportunity.

Star

 

[cyclonebuster]

What should happen is a flurry of instruments being sent to this asteroid to ride its orbit. With it passing as close as it is, it would be a wonderful opportunity to hitch a ride. We can learn many things. Lets not waste the opportunity.

Star

Correct a new Opportunity and Spirit rover similar to the ones on Mars would work very well on this asteroid.

 

[vaseghi]

I like it. Apophis is a chance to be the best space station by orbiting around the Earth or the Moon
a.vaseghi@hotmail.com

 

[cyclonebuster]

I like it orbiting around Earth as our second moon also! Lets vote on it! LOL!

 

[Gravity_Ray]

Of course I know that all that crap that Anatoly Perminov said can be taken with a grain of salt since the Russian space agency is as broke as I am. But still the idea that a country can just up and touch a space rock that has a possibility of impacting Earth (albeit a slim to none chance, and slim just left town) is pretty scary.

I hope he does another vodka shot and forgets about this.

 

[dragon04]

"If it ain't broke, don't fix it."

 

[tanstaafl76]

Why is it that there is such an uncertainty factor in predicting the course of these objects? We can send space probes all over our solar system to perfectly rendezvous with various planets, comets, and asteroids, but when examining a giant asteroid headed at us it is still a matter of probability as to whether it will hit us? Is it because the mass of the object is unknown? Couldn't we get a good estimate of its mass based upon its past trajectory through the solar system?

 

[tanstaafl76]

I like it orbiting around Earth as our second moon also! Lets vote on it! LOL!

It would be a hell of a counter-weight for a space elevator!

 

[MeteorWayne]

Why is it that there is such an uncertainty factor in predicting the course of these objects? We can send space probes all over our solar system to perfectly rendezvous with various planets, comets, and asteroids, but when examining a giant asteroid headed at us it is still a matter of probability as to whether it will hit us? Is it because the mass of the object is unknown? Couldn't we get a good estimate of its mass based upon its past trajectory through the solar system?

It's not the mass, but for most, it's the uncertainty in the orbit. An orbit is detemined by making repeated measurements of it's position against the background stars. Every measurement has some uncertainty, so rather than a series of points across the sky, instead you have a series of small cirles against the background. Many possible orbits can pass through all those circles. So there are many possible orbits, and for objects on the risk pages, some of those orbits (not very many, but some) can intersect earth. The longer you observe an orbit (the "arc" or how many days) the more circles you have, and the fewer, and more closely grouped orbits that can fit the observations. So the possible orbits become more refined, and fewer (or none) can intersect earth.

For a spacecraft, we not only have the positions, but we have constant radio contact with the craft. That gives us precise (VERY precise) measurements of it's velocity, as well as it's position. SO there is only a very narrow band of possible paths. As the mission evolves, little tweaks are done to ensure that the possible paths are aiming where we want it to.

For a well studied object like Apophis, some other effects come into play. We actually have a few (7, compared to 1399 position) precise doppler (velocity) measurements, so it's orbit is very well known compared to most. But there is still some uncertainty, and due to the close approach to earth in 2029, even a few meters of difference in the exact path will have a much larger change in the orbit that will result afterward. In addition, there are some other subtle effects, such as solar wind, the YORK effect , the Yarkovsky effect, etc. Basically the last two have to do with how radiation from the sun is absorbed and reradiated from the surface, which depends on how the surface absorbs and reradiated the energy, how fast the object is spinning, what axis it is rotating on, it's exact shape, and in that case, the mass does make a difference. Apophis is the most analyzed asteroid in history, but all these affects could add up to change it's path by a few meters, or a few millimeters per second in velocity, which will have huge affects after the 2029 close approach.

We will get a repeat of such radar measurements in 2013 which will refine the orbit even more, but those other subtle effects will remain.