Slashdot Mirror
Gravitational Currents Could Slash Fuel Needed For Space Flight
Hugh Pickens writes "BBC reports that scientists are mapping the gravitational corridors created from the complex interplay of attractive forces between planets and moons that can be used to cut the cost of journeys in space. 'Basically the idea is there are low energy pathways winding between planets and moons that would slash the amount of fuel needed to explore the solar system,' says Professor Shane Ross from Virginia Tech. 'These are free-fall pathways in space around and between gravitational bodies. Instead of falling down, like you do on Earth, you fall along these tubes.' The pathways connect Lagrange points where gravitational forces balance out. Depicted by computer graphics, the pathways look like strands of spaghetti that wrap around planetary bodies and snake between them. 'If you're in a parking orbit round the Earth, and one of them intersects your trajectory, you just need enough fuel to change your velocity and now you're on a new trajectory that is free,' says Ross. 'You could travel between the moons of Jupiter essentially for free. All you need is a little bit of fuel to do course corrections.' The Genesis spacecraft used gravitational pathways that allowed the amount of fuel carried by the probe to be cut 10-fold, but the trade off is time. While it would take a few months to get around the Jovian moon system using gravitational currents (PDF), attempting to get a free ride from Earth to Mars on the currents might take thousands of years."
Space Travel is just like the internet. All you need to do is navigate a bunch of tubes.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
For example, this old article discusses the same concept.
In my day we went to Mars uphill both ways unlike you kids who coast the whole way - and we LIKED IT!!!
While it would take a few months to get round the Jovian moon system suing gravitational currents (PDF)...
I had never before considered using the power of lawsuits to drive an inter-planetary vehicle, very interesting. But is it feasible? What's the TPL (thrust per lawsuit) against a given gravitational current and how many lawsuits can a lawyer put out during the life of a mission? Does the size of the gravitational current matter? I imagine so since they said the system is much faster suing Jupiter's gravitational currents than Earth's and Mars' currents.
I haven't seen any solid details on this yet, I think this whole plan is still a ways off yet.
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
Apparently the Rocket Industry Association of America found out that people were planning to travel for free by stealing gravity from nearby planets. They also discovered that gravitational currents are aiding and abetting these crimes by making it easy to find and use the gravity. These pirates think they can escape prosecution by relocating to the Jovian moon system, but the RIAA lawyers were able to track them down and sue them within a few months.
The vast majority of fuel usage is simply getting out of orbit. I imagine this would be musch more useful for vehicles that are simply motoring around the solar system, but not dropping to the planet, or even going into LEO.
But TFA makes it sound like you can find 'just the right spot just past the Moon' and zoooooop! Off you go the the gasoline seas of Titan.
BS.
Douglas Adams stated that "Space if really big." The image in TFA makes it looks like a skate park. Try drawing the Solar System to scale, and you begin to get the idea. A local community college has a scale MODEL. The sun is about a meter in diameter a frisbee throw away is Earth, this tiny dot with a tinier a fly's wingspan away. It took us a Saturn V to get there and 4 days. TFA wants us to think that once we get there, we can "freefall [down] pathways in space around and between gravitational bodies. Instead of falling down, like you do on Earth, you fall along these tubes." That's crap, without a metric a55load of Delta V.
'If you're in a parking orbit round the Earth, and one of them intersects your trajectory, you just need enough fuel to change your velocity and now you're on a new trajectory that is free.''
BS.
Now, I can go back to sleep
I swear to God...I swear to God! That is NOT how you treat your human!
This is not new. Almost every mission going further away than Mars or Venus uses these gravity assists, and has since Mariner 10 (1974).
I really dislike the term "gravitational currents." It conveys exactly the wrong impression. The effects of 3rd bodies is almost negligable except during close approaches, so "gravitational billiards" would be much more appropriate.
Depends on your time horizon. Millions of years, no. Human time horizons, however, we can handle.
A good, modern, numerical integrator at quadruple precision can handle the Sun, planets, and hundreds of asteroids with very small numerical errors (microns over decades). Bigger errors are introduced by observational uncertainty, primarily in the masses of the asteroids. But, even with that, errors are 100's of meters over decades.
Pffft, Russians do it for $40, and survive more.
Table-ized A.I.
Like fish in the water, we are swimming in an immense sea of energetic particles but we can't see it. An analysis of the causality of motion leads to the inevitable conclusion that we are moving in an immense sea of energetic particles. Soon we will understand how to tap into the sea for energy production and extremely fast transportation. It will be an age where vehicles have no need of wheels, move silently at enormous speeds with no visible means of propulsion and negotiate right-angle turns without slowing down. Get ready for interesting times ahead because Aristotle was right about motion requiring a cause.
The Problem with Motion
The "tubes" are unfortunately only "tubular" through four-dimensional spacetime. In three-dimensional space, they're just a spot (a LaGrange point) that moves around as the various bodies orbit. If you are trying to move faster than that, then you're essentially leaving the tube and entirely to navigate spacetime on your own power.
The World Wide Web is dying. Soon, we shall have only the Internet.
Now if we only had a book to tell us how to use these unsecured cargo bays to get around the Galaxy...
HA! I just wasted some of your bandwidth with a frivolous sig!
Just thought I'd add another clarifying point.
It's often hard to visualize this, but even though a gravity current path (the minimum energy path) in a 6-d manifold (position+velocity) has time-varying velocity 3d velocitu (because the path isn't straight in 3d space it implies some acceleration from a 3d perspective), the velocity change is still essentially zero energy because sometimes the energy for the required velocity changes can come from gravity interaction itself (imagine a "valley" of some sort in a 6-d manifold), although some may require being very near the optimal path (imagine a "ridge" of some sort in a 6-d manifold) and thus require small corrections to prevent "butterfly-effects" from pushing the spacecraft further away from the optimal path (which these small course corrections are still better than fighting gravity all the way to the destination).