Gravitational Currents Could Slash Fuel Needed For Space Flight 177
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."
fracking lawyers theyre everywhere (Score:3, Interesting)
... Jovian moon system suing gravitational currents ...
The best ideas of the 1970's ! (Score:4, Interesting)
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.
Re:Getting out of Orbit (Score:5, Interesting)
Which is why we need one of these: http://en.wikipedia.org/wiki/Launch_loop [wikipedia.org]
Have a look at the economics:
So if there was a 10-fold decrease (Score:2, Interesting)
1. Take a craft that has the fuel and thrust to go from Earth to Mars without the tubes in X days.
2. Actively navigate the tubes instead of free-falling
3. Wouldn't this make for a shorter, more efficient trip?
4. Does navigating the currents have any effect on relativity? (Could a ship travel closer to c through these tubes?)
Re:So if there was a 10-fold decrease (Score:3, Interesting)
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.
Re:Getting out of Orbit (Score:3, Interesting)
I can't look at the economics - because there aren't any economics to looks at, only theories based on some questionable assumptions.
Like this one: The launch loop will, unlike any other significant project ever, come in at or under budget and at or under schedule. Or this one: That it will generate sufficient revenue in the first year(s) of operation to pay not only operating overhead, but also interest and principal. (Highly doubtful as there isn't any backlog of payloads sitting around waiting for launch - it will take years for the demand to build.)
Or the most questionable assumption of all: That it can actually be built and will operate as designed.
Re:You can't dumb down rocket science (Score:3, Interesting)
If I'm in orbit around the sun, stationed at an L1, 2, 3, where do I get the delta V (change in energy) from Earth's circular orbit to Jupiter? What magical force adds energy to my current trajectory?
I'm looking at a reference to "a great book written by Edward Belbruno on his design of advanced trajectories called "Weak Stability Boundary Trajectories". http://www.tobedetermined.org/2008/10/fly_me_to_the_moon.html [tobedetermined.org]. I see a trajectory which flies from Earth to lunar distance in 2 days. That's not "low energy". That's twice the speed of the moonshots. Yes, I know that using this chaotic system, you can slide into lunar orbit (capture) without having to burn much propellant, so you can use that in the boost. But that won't get you past the moon. It won't get you to Mars, asteroids, comets or Jupiter. You need more energy, not more time. Where does the energy come from? Chaos? HA!
The basic idea is that if you can get to one of the (unstable) Lagrange points (#1-3), only a very small impulse is needed to go anywhere in the solar system.
Ok, this is the kernel of my argument. Stop using "dumbed down" descriptors like "only a very small impulse". You are dumbing them down even more.
It is an illustrative myth that "once you get into earth orbit, you are halfway to anywhere." I did this math a long time ago. It goes like this... You need, ballpark, 7km/s to get into earth orbit. From there, you only need 11km/s to escape. That's a MERE 4km/s. THAT'S NOT MERE! "very little impulse is like "333m/s" maybe an OMS burn. 4KM/S is an apogee kick motor weighing in at a goodly portion of the total payload's mass. Gross Mass: 543 kg (1,197 lb) [astronautix.com] to get a 1737 lb (788 kg)spacecraft into GeoSynch. Not the moon, which is 10 times farther.
It takes a LOT of energy to get from here to 'there.' Chaos doesn't provide it. Stop making it sound like it does.