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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!!!
Next:$150 trip to Mars
Come on MIT boys, pump up that balloon and add another handwarmer.
... Jovian moon system suing gravitational currents ...
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.
This is a great idea but the difficulty is in solving n-body problems incorporating all the gravitational bodies in the solar system.
Even finding the Lagrange points between the earth, sun, and moon is very difficult. Throw in all the other moons and planets and you have a even harder task on your hands.
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.
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
Nope and nope.
It's just a low energy, weird looking, series of orbits. If you want to go to Jupiter, say, there are a couple of ways to do it. You can use lots of fuel and put yourself on a highly elliptical orbit of the sun then, when you're near Jupiter, use lots more fuel to kick yourself into orbit around it.
Or you can use less fuel to slowly spiral out to higher and higher Earth orbit, then maybe you kick into your own solar orbit, then maybe you wait until Mars is in the right place to kick you over into a higher solar orbit, then work your way over and get captured by Jupiter.
You can use various gravity slingshot maneuvers to help get you somewhere, which is what spacecraft have been doing since the first interplanetary probes, but if you don't want to wait around you can't use the "tubes." And they have no effect whatsoever on the laws of physics.
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.
"Up" is not the problem in getting to space; it is the velocity that is the problem. A 747 can reach a top speed of 567 miles per hour, while orbital velocity is 17,500 miles per hour. So, even if you could make a 747 carry a fully-loaded shuttle (it can't), you'd still need to accelerate an additional 17,000 miles per hour (which would still require the solid rocket boosters and the external tank, which are the majority of the weight, which a 747 certainly couldn't carry).
The shuttle passes a speed of 567 miles per hour in the first 20-30 seconds of flight IIRC. They are already throtting back the engines by that point to reduce aerodynamic stress on the vehicle.
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!
A gravity assist trajectory is using the gravitational field of a large planet to divert a spacecraft to it's final destination. Since you are falling down a gravity well with this trajectory, you generate acceleration. The reason this works is that you are essentially "stealing" some of the momentum from the planet (think billiard balls colliding and exchanging momentum, but this is just without the collision).
This technique is almost the dual of the gravity assist in that it has the spacecraft follow the 3 dimensional paths of zero-net gravitational acceleration. Think of this like walking between two mountains mostly along the isolines (instead of taking a path where you are walking down into a valley and have to walk back up). The path might be long and windy to walk across the iso lines, but you reduce the total energy you have to expend (except to get from your starting point to the iso-line and from the iso-line to your destination). The reason these paths are called currents is that it really isn't a 2-d isopath with minimum energy you are following, but really a 6-d iso path (position and velocity thus a "current"). This is where the analogy breaks down with the 2d isopath.
BTW, this is really, really old news... http://www.jpl.nasa.gov/releases/2002/release_2002_147.html
And also a DUPE http://science.slashdot.org/article.pl?sid=03/03/07/215211&mode=thread&tid=160
The problem is even at high-orbit you still need to slow down at intercept and circularise your orbit. You'd be much better off making fast fly-by on an (sun-centric) elliptical orbit that returns to Earth on the way back in. That way, you're in Mar's neighborhood for a month or so and can easily dispatch a lander for the final leg to Mars, but you don't waste a fuckton worth of fuel slowing down the bulk of your vessel to stop at the planet itself - save that for braking when you get home.
Scientists point out problems, engineers fix them
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The "tubes" are really iso-paths in 6-dimensional (3d position + 3d velocity).
The "tubes" happen to connect the LaGrange points in 4d, though.
You do NOT have to navigate spacetime in your own power if you stay in these "tubes", although since they are 6-d isopaths, their "minimum energy" aspect to the path is really at their intrinsic velocity (which is why they are slow).
Let's try to get this one right...