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Road Trip On The Interplanetary Superhighway
eegad writes: "CNN has an article about a new idea from NASA springing from chaos theory called the interplanetary superhighway. It will purportedly allow easier space travel by steering through regions where the net gravitational force exerted by nearby bodies is smallest. The actual NASA news release is here. Sounds like an interesting concept but it is unclear how the scientists will account for every source of gravity, including the elusive dark matter."
The theories "from Star Trek" are actually simply upscale versions of those explained in high school physics textbooks.
Of course it's a great theory... they would never put a sketchy one in a school textbook. Wait, Darwin's evolution theory.... Big Bang... sorry, scratch that last statement.
However, as we learn as early as middle school science, there is minimal friction in space because it is a vacuum.
The research is about finding low-cost paths through the solar system, not interstellar space. The dynamics of the solar system are very well understood, and all of the important gravitating bodies are known (there isn't any significant dark matter inside the solar system, by the way). You just have to do some heavy-duty computations to take advantage of all that.
You can't solve the three-body problem for a general case (meaning analytically, with the solution written as an equation). You can numerically model the behavior of a gravitational system with many bodies, given some initial conditions.
However, over time your numerical model will deviate more and more from the real evolution of the system. As long as the timescale of this error growth is much longer than a typical spacecraft's travel time, these numerical models are good enough to predict orbital trajectories accurately. Given that current models are estimated to be accurate for many thousands of years, it's no problem.
Liberal (adj.): Free from bigotry; open to progress; tolerant of others.
Which makes sense for interstellar travel.
in interplanetary travel, these areas are probably constantly shifting, and so I wonder if the speed of shift is faster or slower than current space craft.
- Each planet and moon has five locations in space called Lagrange points, where one body's gravity balances another's. Spacecraft can orbit there while burning very little fuel. To find the Interplanetary Superhighway, Lo mapped all the possible flight paths among the Lagrange points, varying the distance the spacecraft would go and how fast or slow it would travel. Like threads twisted together to form a rope, the possible flight paths formed tubes in space. Lo plans to map out these tubes for the whole solar system.
They apparently delivered the software tool to NASA back in 2000."It is a greater offense to steal men's labor, than their clothes"
I don't mean to be picky, but radio astronomy and SETI have nothing to do with hearing. Despite what you may have seen in the movies, there are no headphones hooked up to radio telescopes, and if there were you would hear static no matter where the dishes were pointed. Also if you think SETI is some how going to help out by scanning the sky in radio and finding small objects you are mistaken. SETI only has time on Arecibo, (I believe, unless something has changed) and their reciever setup is not at all optimized for tracking objects. First off because Arecibo can't really move, and second because their entire goal is just to gather up all the static and look for patterns.
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Striving to put right what once went wrong, and hoping each time that his next leap, will be the leap ho
CHAOS THEORY...
It does apply to everything, but the little bit that is applies to really big things like planets and their effect on a space craft is negligile.
SLING SHOT...
A lot of people are talking about using gravity to propel a space craft, but don't seem to understand exactly how it works. When a space craft sling shots around a planet, what happens is this. The SC is captured by the gravity of the planet. The SC begins to fall towards the planet. However, it is falling at such an angle that it will never hit the planet or a significant portion of its atmosphere and is therefore release back into space. Now, conservation of energy applies and says that the kenetic energy gained by falling towards the planet is lost when it escapes on the other side. BUT (this is the heart of how the sling shot works) the planet is orbiting the sun. When the SC begins falling towards the planet, it also gains some of the energy from the planet itself. The SC picks up a significant portion of the velocity of the planet in it's orbit around the sun. When you apply the law of gravity for 2 bodies, you will figure out that the planet actually slows down because some of its energy is given to the SC. The end result is a SC that is going much faster and it didn't have to burn any fuel.
SPACE CRAFT'S FUEL...
several people are saying that the SC doesn't need to use fuel. If we could calculate exactly where everything is in the universe, then we could do it with almost no fuel. But we can't. Also, as all the calculations are only a pretty good estimate, the SC carries enough fuel to make in flight corrections.
LAGRANGE POINTS...
There are 5 points where gravity cancels exactly.
1. directly between the earth and the moon.
2. leading both the earth and the moon. It is in orbit around both the earth and moon, but does not move realtive to them because it can't fall around both.
3. same as 2, but trailing instead of leading
4. on the opposite side of the earth from the moon
5. on the opposite of the moon from the earth.
HOWEVER, only 2 points are STABLE. Points 1,4 and 5 are unstable, points 2 and 3 are stable. If you solve the problem, you realize that points 1,4, and 5 are sources and points 2 and 3 are sinks.
Now to qualify myself. I've only had 2 astro engineering courses (taken for fun) a few years ago back in college, so if i've made any mistakes, please forgive me and correct me.
If I drive fast enough at the red light, it'll appear green.
I recently read and interesting article in SCIAM proposing an alternative to the mysterious dark mater. He calls his theory MOND (Modification of Newtonian Dynamics) where he states that for extremely weak gravitational fields (a < 10E-5 m/s^2), F approaches ma^2. Apparently, his equation is able to explain the stability of may galaxies well without having to use dark matter. It remains to be seen whether his theroy will hold up to serious scrutiny but already, astronomers are using it to model galaxies (using it as a calculation technique instead of an actual law of nature). He has yet to incorporate it in relativity.
More information is available at http://www.astro.umd.edu/~ssm/mond/litsub.html
Lord, bless my users that they may stop being such fucking idiots!!
Gravity does not cause friction. Friction converts kinetic enery into heat which cannot be feasibly recovered. Total energy (potential + kinetic) in a gravity field is strictly conserved. Friction will most likely be greater in the "Super Highway" as interplanitary dust will collect in these gravity wells.
Contrary to what you say, the position of the planets is known to astonishing accuracy- it's only over millions of years that they move significantly chaotically, over a few months their position is entirely known.
A small body bouncing around between them is rather different however- that can be very chaotic.
Plotting a course through the solar system is quite routinely achieved. Remember Voyager?
Uh, wouldn't there be *TWO* such points? Think about it.
Do a web search on Lagrange points, you'll find it. There's 5. One between the earth and moon, one the other side of the moon, one opposite from the moon, one 60 degrees ahead of the moon and one 60 degrees behind.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Actually not the coriolis force. In the frame rotating about the center of mass you only have to consider gravity and the 'centrifugal force'. If you draw a map of the overall forces you find that there are 5 points in the rotating frame where there are no overall forces acting; these are the lagrange points. It's all amazingly elegant actually.
The coriolis forces are important when you are moving around in this rotating frame however.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Basically what happens is that there are certain points near to the earth and every other body in the solar system called the Lagrange points. The researchers have worked out a way of calculating a route that passes through the regions around the Lagrange points to jump from planet to planet with almost no expenditure of fuel.
The only downside to this is that the route is probably going to be slow; several years to go from place to place. Still, the implications of being able to move cargo/fuel to say, Mars ahead of human habitation cannot be overestimated. The other downside is you have to be fairly high above the earth initially to be able to reach the 'superhighways', so don't expect the program to give directions from route 66 ;-)
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Actually, it really doesn't take all that much computing power. I did a bunch of work on 3-body trajectories during graduate school, and my workhorse computer for that research was my home-PC at the time - a K6-2 (400MHz) running debian. As well, I was computing much more than just the trajectory. I was simultaneously computing a 6x6 matrix differential equation that provided a linearization around the trajectory. Even then, it was only when I got into doing large runs involving hundreds of trajectories that I found I needed to shift things to a server-level machine.
You are correct that a good idea of the initial conditions is essential. Without it, you are basically flailing blindly in the 6-dimensional phase space - it's unlikely that you'll find the trajectory you want. That's why Lagrange (libration) points are so popular. They are analytical "particular" solutions that provide a starting point for finding initial conditions. In addition, there are approximations for various periodic trajectories near the libration points that also give a nice place to start. From the periodic solutions it is relatively easy to use numerical methods to map out stable and unstable manifolds to/from the periodic solutions. Next thing you know, you're on the interplanetary superhighway...