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."

Comments

come on....

[LMCBoy]

Dark Matter?! Absolutely negligible on interplanetary scales.

Re:3-body problem?

[gilroy]

Blockquoth the poster:

Really? I thought the 3-body problem [uoregon.edu] was not solvable.

It's not solvable analytically. But it's a breeze to model the diff eq's. Doing it accuractely for long can be tricky, though...

its called falling

[Edmund Blackadder]

any "effect" where you use grvity to move with zero fuel is called falling.

no need to give it fancy names.

Re:Chaos theory itself also rules this out...

[exploder]

Actually if either of you had bothered to do a Google search for "Lagrange Points", you'd know (at least) three things:

• Lagrange Points don't just refer two any two bodies, but to two bodies orbiting each other.
• They are not points where gravity "exactly balances out", but rather where the combined gravity of the two bodies exactly cancels the centripetal acceleration needed to rotate along with them.
• There are exactly five. (But two are unstable if the mass ratio is too low, below 25 or so)

(mis)understanding the paper...

[slew]

Nowhere did Mr. Lo describe in his paper that the gravity cancels out on these paths (only that they were minimum energy and connected the Lagrange points).

The whole idea of a minimum energy paths through the solar system is that it's a dynamical systems of greater than 2 dimensions. The weird thing about dynamical systems of 3 dimensions is that trajectories in some of these systems exhibit a type of predictability called a "strange" attractor.

Strange attractors for trajectories are different than the attractors you normally see in 2 dimensions (like local minima or orbits that retrace themselves) in that small pertubations can cause greatly divergent behavior. Even though the behavior appears chaotic, in some systems, the behavior can still be described as nearby a "strange" attractor. This is effect is often called chaos, and the study of strange attractors is called chaos theory.

Apparently Mr. Lo has worked out a theory where the minimum energy trajectories under this complicated dynamical system (planetary gravitational attraction) exhibits attractors that looks like "tubes" that exhibit the chaos-like behavior of strange attractors.

At first glance, these tubes appear to have the dynamical structure similar to n-body orbits (this factoid about orbits was first discovered by Michel Henon in the 60's). "orbits" in n-body systems don't actually retrace themselves, but sort of looks like a coiled up extension cord. The envelope or attractor of the orbits look sort of like a mis-shaped torus (squished donut), where the orbits can pretty much be anywhere on the surface of the donut (the attractor), but the path it takes is somewhat unpredictable (chaos) and highly dependent on initial conditions. There are more complicated attractors (some involving little islands of stability inside the donut) depending on the energy level, but this is the basic idea. This discovery seems to extend this known factoid about orbits to the structure of minimum energy trajectories in n-body gravitational fields.

All this will be moot, however, when in the 2004 election, Al Gore wins the presidency by taking credit for inventing the Interplanetary Super-Highway while giving a campaign speech for an increased budget for Nasa leading all the l337 geek-crackers to rig the newly approved, non-tamperproof election computers... I boldly predict this will be henceforth called the "butterfly-ballot" effect... But I digress... ;^)