Slingshots in space

Des Emery,The Carborundum Chronicles,St.Thomas,ON,Canada — Wed, 28 Feb 2007 01:59:23 GMT

Hi, Alan -- I never really liked the image evoked by the word.'slingshot.' I could understand the use of gravity to increase the momentum of the probe, but I wished for a better description; 'carom' like a billiard ball implied actual contact, which wasn't the case. 'Gravity-assisted' seemed like too many letters. 'Cycling' implies repeating the maneuver. Oberg says it best with 'bounce' I guess. Maybe somebody else will come up with the exact word that adequately describes the trajectory that swings a probe on another body's gravity and imparts a new trajectory to the probe. Maybe 'levering' or 'leverage'? Was it Galileo who said, "Give me a place to stand, and a lever long enough, and I shall move the Moon."

Slingshots in space

Alfred Kelgarries — Wed, 28 Feb 2007 03:57:31 GMT

Speaking of gravity, New Horizons is planned to figure in the study of the Pioneer Anomaly (http://en.wikipedia.org/wiki/Pioneer_anomaly)a possible deviation from general relativity predicted by the MOND theory. If all known factors are counted, all long-duration probes are experiencing a small but detectable drag pulling them back towards the sun. First detected with the Pioneer spacecraft, it has also been seen in Cassini and Ulysses as well. Further study of New Horizons may shed further light on the effect, and settle once and for all if it is a measurement error, some overlooked normal explanation, or the first glimmer of new physics in gravitational study.

Slingshots in space

Des Emery,The Carborundum Chronicles,St.Thomas,ON,Canada — Wed, 28 Feb 2007 05:56:53 GMT

Alfred K. - Are those long-duration probes being monitored all the time for gravitational influences? Sol's gravity may have diminished to a point of 'no essential presence' and have been discounted in the measurements. But since gravity between objects always exists, maybe it should still be counted.

Slingshots in space

Rick Peterson, Grand Junction, CO — Wed, 28 Feb 2007 14:59:26 GMT

I believe the "sling-shot" terminology comes from a technique skaters use to "sling" the last guy in a line of folks going around a rink. Each person in line pulls the one behind (with, say, their right hand and arm). This speeds up the rear skater and slows down the lead skater. The overall effect on the last skater can be fairly dramatic.

Slingshots in space

Wade Whitlock, Aberdeen, MD — Wed, 28 Feb 2007 15:18:49 GMT

If you substitute the two thongs of the ancient sling for the "Y"shaped "slingshot of more modern origin, it still applies.

The operator or slinger has to put energy into the sling and the slung object. Everything is conserved. Originally the Pioneer or Voyager mission was to use a series of gravity assists for course changes and velocity increases. There was an original plan for a "Grand Tour" that was supposed to include Pluto, but took different courses.

When you do your gravitational experiments out of a gravity well, who knows? Seems to me The Mote in God's Eye (based on Robert Forward's theory) and some of Larry Niven's Known Space series forwards that idea.

Actually, Des, I believe I heard Archimedes say that!

Slingshots in space

Elvis Saravia — Wed, 28 Feb 2007 15:34:29 GMT

this is the first time i have come in this website and i read this interesting topic of the slingshot project. i study physics and i mean if this project was taken seriously by a group of young physicians who knows that in the future there will be our race living there. i have always dreamt of this and this inspires my wildest wishes to become the best physician ever. please tell me more on this slingshot anyone.

gladly appreciate it...

thanks...

Slingshots in space

Joe Azar, Cumming, Georgia — Wed, 28 Feb 2007 15:50:52 GMT

How about planetary gravitational push? It is the massive attraction of a large body that is then converted into a push, isn't it? As long as the spacecraft is above escape velocity and does not aim directly for the planet, it will be slung around the planet and propelled away at a higher speed.

Slingshots in space

Scott Hellier, Eugene, OR — Wed, 28 Feb 2007 16:21:40 GMT

I don't know about the relativity question, but the "slingshot" doesn't sound right to me either. How about comparing it to a vane or impeller pump? The water (space probe) is drawn in by the pump suction (gravity) and accelerated out the other side with greater pressure (force/speed/velocity)? Or, maybe a baseball pitching machine? Something that works radially or tangentially.

Slingshots in space

uwe fruendt san felipe baja mexico — Wed, 28 Feb 2007 16:33:53 GMT

i would like to see ones, the speed the are traveling and how much faster the travel after the slingshot effect??? thank you baja uwe!

Slingshots in space

Thomas Ashby, Calgary — Wed, 28 Feb 2007 16:46:31 GMT

Gravity assist is obviously an oxymoron. Why don't they just refer to it as it is rather than pander to the general population. If you say "angular momentum transfer or assist" I suppose you'd burst too many bubbles perhaps?

Slingshots in space

Frank, Dallas, TX. — Wed, 28 Feb 2007 17:30:46 GMT

I'd call it a "flyby". The craft is, of course, not actually flying but on a trajectory, but its a simple term that is accessible to a layman. It also explains the opportunity to take some pictures during the "flyby". If someone asks, you can say "it picks up speed, in a new direction, from the flyby."

Slingshots in space

Danny Walsh, Paducah, KY — Wed, 28 Feb 2007 17:39:17 GMT

Everybody talks about the speed gained as the rocket move toward the slingshot mass. But nobody explains how that same mass does not take away the speed as the rocket (or spacecraft) passes by and moves away from the slingshot mass. Where is the net gain in speed?

Slingshots in space

Danny Walsh, Paducah, KY — Wed, 28 Feb 2007 17:41:10 GMT

Slingshots in space

Sean, Oklahoma City — Wed, 28 Feb 2007 17:44:27 GMT

Don't think of the word as "slingshot". Think of it as "sling shot".

Slingshots in space

Gaetano Marano - Italy — Wed, 28 Feb 2007 17:50:17 GMT

.

not related with New Horizons but interesting...

I think that ALL versions of Orion (standard or TBS, small or big SM) must have its TPS firmly joined to the capsule an that a jettisoned TPS is a BAD design and a (possible) BIG risk, as explained in my new article:

http://www.gaetanomarano.it/articles/022orionTPS.html

in my opinion the BEST solution is to firmly join the TPS to the Orion's main body and locate the parachutes/airbags outlets on the Orion's sidewalls

.

Slingshots in space

Paul Miller, Woodbridge, VA — Wed, 28 Feb 2007 18:04:02 GMT

How about just "pulling" or "pushing?" The spaceship is simply pulled or pushed by the planet's gravity, depending on the direction the planet is moving, relative to the spacecraft.

Slingshots in space

Ron Phelps — Wed, 28 Feb 2007 18:34:40 GMT

It would appear that the english and scientific explinations are not acceptable. I propose following the advertising industry and forming new words describing the phenomenon. Like "gravacc" and "gravdec". Maybe just abbreviations like "GA" or "GD" would reduce typing even more? Maybe new words in our language will allow more poetry rhymes to be developed?

Slingshots in space

Jim Moore, Washington, D.C. — Wed, 28 Feb 2007 19:13:52 GMT

Des, it was Archimedes, not Galileo, who is generally credited with saying "Give me a place to stand and a lever long enough and I will move the world." Given that the attribution goes back to 220 BC, many versions have evolved.

Slingshots in space

Mike Feeley, Buffalo — Wed, 28 Feb 2007 19:25:26 GMT

Dear Alan, I also never liked the slingshot description for gravity assist. As an analagous effect for light is called gravitational lensing, why don't we call this angular lensing.

Slingshots in space

Loren Umbertis — Wed, 28 Feb 2007 19:42:26 GMT

When I looked at the Wikipedia site that described Cassini's velocity changes as a result of the gravity assist, I was somewhat surprised to the see the decrease in the speed of Cassini over it's long flight.

I had thought that space, since it has no air, would not experience friction, thereby causing any object to continue in its original speed. I suppose then that there is something then that is causing the friction, would that be because of minuscule levels of "air" (for lack of a better word) that would cause the friction?

Slingshots in space

Julio Lainez — Wed, 28 Feb 2007 19:51:27 GMT

Well, I've always looked at the 'gravity-assist' maneuver like a space probe being 'grabbed' by the planet's gravitational field and then using that 'force' or momentum gained from entering a planet's gravitational pull like a game of tether ball to speed it up.

Slingshots in space

John F. Reese, Jr., Barre, VT — Wed, 28 Feb 2007 20:31:09 GMT

Writing as a non-scientist, science geek, I would call it “The Carousel Effect” or the less scientific sounding “Merry-Go-Round Effect.” A stationary or slow moving object that is placed on a carousel will quickly begin traveling at the same speed as the carousel. When the object exits the carousel, it will do so more or less at the speed at which it was traveling while on the carousel (less the deceleration resulting from the carousel’s gravitational pull). How do you like them Newton’s apples?

Slingshots in space

Avery, Orlando Fl — Wed, 28 Feb 2007 20:34:44 GMT

Not that anyone wants to compare astronomy with auto racing, but the closest thing for comparison would be what is known as "drafting" where a lead car is followed closely by a trailing one. The rear of the lead car creates an area of low pressure and if the second car can place itself within this area, the low intensity vacuum-effect will exert a pulling force on it, allowing it to gain at the expense of the lead car's forward aerodynamics.

Slingshots in space

Alan Boyle — Wed, 28 Feb 2007 20:40:29 GMT

Actually, I had the same thought as Avery. The trick for a gravity-assisted speed-up is that the small spacecraft comes up from behind in the planet's orbit. The planet thus "pulls" the spacecraft more quickly, then veers off in its orbit, going along its merry way (just a bit more slowly, because of the transfer of angular momentum).

A gravity-assist will slow down the spacecraft if it passes in front of the planet in its orbit. In a sense, it's being "pulled back," while the planet is being pushed forward in its orbit by a very small amount.

Maybe this will make Jim Oberg's reference to the "ball off a wall" analogy a little clearer.

Slingshots in space

Luke, Seattle — Wed, 28 Feb 2007 20:43:14 GMT

At the expense of not being very scientific--how about "Flingshot?" Sounds like a nerf toy...oh well.

Slingshots in space

Rod Luhn, Middletown, NJ — Wed, 28 Feb 2007 21:23:22 GMT

I think a better analogy for gravitational slingshot is “drafting” such as a biker riding in front of another biker to reduce the energy expenditure of the rider behind. Clearly there is no turbulent effect in this gravitational drafting but the spacecraft in essence uses the orbital speed of the planet to boost its speed. Please feel free to use the term “gravitational drafting” for this interplanetary speed boost technique!

Slingshots in space

Eric Jobe, Orange County, CA — Wed, 28 Feb 2007 22:56:15 GMT

To: Danny Walsh

I think you are completely right; as I understand it- there is *no* net gain in speed relative to the planet providing the gravitational assist. "relative to the planet" is an important distinction because the planet is moving relative to the sun which is the kind of relative motion we're concerned about (and is the kind of relative motion we're increasing). Anyone- please feel free to correct me if I'm wrong.

BTW: I agree with Ron Phelps. We need some sort of catchy acronym or something. Perhaps "SPAM Injection" (for Supplemental Planetary Angular Momentum Injection). ;-)

Slingshots in space

Thomas Ashby, Calgary — Wed, 28 Feb 2007 23:30:22 GMT

Jeez..if we keep this up long enough, we'll start crashing planets into the sun!

Slingshots in space

Mark Healy, Melbourne , Australia — Thu, 01 Mar 2007 00:48:48 GMT

It certainly must be magic.I appreciate the gain in speed from the gravitational pull , but why isnt this equally lost as the object is going away ?

Slingshots in space

Mike Dondero — Thu, 01 Mar 2007 01:02:45 GMT

To answer Loren about the Cassini's velocity change, or slowing after the gravity assist... I think that space is not a perfect vacuum, but comes closer to a "perfect vacuum" than anything else in nature. Quantum mechanic's and gases found in space are some of the reasons for the decreasing speed of Cassini after the 'gravitational assist'

Slingshots in space

kelleigh lonidier — Thu, 01 Mar 2007 01:31:21 GMT

So in theory, I'm not talking about anytime in the near future but one day could one change the orbit of a planet by using this method. Take a large asteroid and keep swinging it by a planet like Venus and move it to a farther out orbit? Thus cooling the planet? or one day millions of years from now when the sun swells to a red giant (if were still around) could our sentimental descendants move the earth to an orbit where it would not burn up? This just gets me thinking.

Slingshots in space

Stephen Swanstrom, Missoula, MT — Thu, 01 Mar 2007 03:00:34 GMT

It's a whip. Like in 'crack the whip' The person standing still is the planet, the spacecraft is the person at the end. Who picks up speed?

Slingshots in space

Des Emery,The Carborundum Chronicles,St.Thomas, ON,Canada — Thu, 01 Mar 2007 06:27:58 GMT

Wade W. from Aberdeen and Jim M. from Washington, I swear I knew it was Archimedes, I just didn't recognize him with his clothes on after seeing him leap from his bathtub and run through the streets, screaming 'Eureka!' Galileo was a much more formal person. Well, they both moved the Earth, I guess.

After reading all the suggestions given, I myself will think of that move as a 'grass boost' (GRavity ASSisted). After all, the probe is probably bored and tired and needs something to pick it up before it is sent on its way, re-invigorated and with a new vision of its purpose.

I still think it's the gravity of the situation, Loren Umbertis, or rather, Sol's gravity reaching out to Cassini and the other long-gone probes and slowly pulling them back. Remember that gravity is a very weak force, but it has a constancy about it that gives it a power beyond compare to attract. Which is also one of the reasons that probes use grass to maneuver into a velocity and trajectory computed beforehand by their launchers.

Uwe Freundt - each probe will have a different speed and angle of inclination as it approaches the planet, and another, higher speed and change of angle after the maneuver; plotting out the various positions, speeds, angles, and time elapse until the probe receives its instructions from the launchers. Indeed, the original launch from Earth would not even be toward the eventual destination.

Elvis S. you will have fun exploring Alan's blogging here so come back again.

Slingshots in space

Wade Whitlock, Aberdeen, MD — Thu, 01 Mar 2007 14:01:59 GMT

Des, The bare truth!

Slingshots in space

David H., Dallas, TX — Thu, 01 Mar 2007 16:33:32 GMT

I believe that the skating maneuver mentioned by Rick P. is also called "Crack the Whip", and it's the best analog to what's happening - a line of skaters holds hands, one end of the line moves in a slow circle while the other end swings around faster and faster. A single skater approaches the "fast" end of the line and grabs the hand of the end skater, and this keeps up until the speed (and centrifugal force felt by the last skater) gets so high that the end skater has to let go, and goes flying off at a higher speed than any single skater could achieve. The spacecraft does get pulled back and slowed down as it leaves, of course, but since the force of gravity is related to the square distance between the two bodies, the speeded-up spacecraft leaves the planet's vicinity much more quickly, taking a most of its momentum gain with it. Any body moving away from a larger body will continue to slow down until some larger mass(es) exert a stronger influence - which is why Galileo, etc. would continue to slow down. Within the solar system, I believe that this effect far exceeds any friction with dust, gas, and solar wind particles, unless your spacecraft has small mass and large surface area, as in a solar sail.

Slingshots in space

Daniel Asti, Manhattan, New York — Thu, 01 Mar 2007 17:18:01 GMT

Stephen Swanstrom's "whip" analogy is a good one. The rocket closes in on the planet at a very high rate. The closer it gets the stronger the gravitaional pull and the faster the rocket moves. By positioning the rocket perfectly and hitting the engines at just the right times it "whips" off into space at very extreme speeds - just like the "crack" of that whip. Pulled and thrown is another favorite of mine.

This is the most clever way to travel in space. It saves money while being free, preserving resources and maintanence. I feel that with the perfect success of this technology it will lead us to much deeper space travel.

Slingshots in space

Alan Sheets, Loveland CO — Thu, 01 Mar 2007 17:21:18 GMT

Judging from several of the comments in the blog, it is obvious that high schools and colleges have stopped teaching about conservation of momentum.

It is just like bouncing steel balls against each other. One assumes the velocity imparted into it by the other, while the other one loses what is given away. Observed velocities differ after impact if there is a difference in the masses of the objects. In the case of Pluto Express vs. Jupiter, PE gains about 9000 km/h while jupiter loses about .0000001 nm/hour because of the differences in mass

Here's a couple links to basic explanations of the concepts involved:
http://en.wikipedia.org/wiki/Slingshot_effect
http://en.wikipedia.org/wiki/Conservation_of_energy
http://en.wikipedia.org/wiki/Conservation_of_momentum
http://www.physics.lsa.umich.edu/demolab/demo.asp?id=686

Slingshots in space

Thomas Ashby, Calgary — Fri, 02 Mar 2007 00:15:22 GMT

Alan S. The concept has been very well covered. My comment about crashing planets into the sun was a joke. But you did add one small piece that explains it totally when you speak of the relative masses.

Also, next time I am at the bar at the pool table, I'll see it for myself.

Slingshots in space

Stargazer, Cedar Rapids, IA — Fri, 02 Mar 2007 06:37:13 GMT

After reading all of the above comments, I think the name that best describes the maneuver would be "whiplash", as in whiplashing around the planet to gain speed or momentum. Water skiers use this whiplash effect to ski completely around the ski boat pulling them in a maneuver called "360 Around the Boat".

Slingshots in space

Thomas Ashby, Calgary — Sat, 03 Mar 2007 09:38:57 GMT

Well, I was at the bar tonight on the pool table. I came to the conclusion that simple grade 11 or 12 collision "experiments" do not describe the story...at all. How can it? The masses are equal!!

SO..you have to picture what is really happening.

Gravity accelerates Horizon obviously. And at an enormous rate in the case of Jupiter... the REAL velocity of Horizon at some point is many thousands of kms/hr above the resultant 9000 kms/hr gain.

Somehow a transfer of Jupiters' momentum of orbital velocity is imparted to Horizon at some Specific point. It is the mechanism of the transfer that is the problem. Where does it happen and in what way? We are speaking of gravity vs. "speed" or velocity. Somehow all this energy of gravity, mass and velocity (momentum) is mixed up and transmitted.

Slingshots in space

Burton, Brandon, Mantiba Canada — Sun, 04 Mar 2007 01:24:33 GMT

Imagine a tetherball attached to a whirlling pole... Except we can control the string :)

Slingshots in space

Thomas Ashby, Calgary — Fri, 09 Mar 2007 15:47:01 GMT

Another way I picture this is that in collision experiments where momentum is conserved, there is physical contact. A space craft that experiences a "slingshot" increase in energy must make some kind of contact with the planets frame of reference without touching it! If it was just gravity, then the craft would slow down by an equal amount as it proceeded. So what am I missing here?

Slingshots in space

CJ Bonifati New York, NewYork — Mon, 19 Mar 2007 15:25:50 GMT

Imagine if this were performed on a black hole. If we could get a rocket out to the nearest black hole picture how far into space we can send a probe.

Slingshots in space

cmd,stl.mo — Wed, 02 May 2007 15:45:54 GMT

I would call it a course correction. Drag and friction slows a object down.However if you are only going to one planet a strait line is best with little loss of speed because of less drag from a larger body

Slingshots in space

Ron Terborg, Larkspur, CO — Wed, 02 May 2007 22:02:29 GMT

So, I think it should be called "swoosh," except then Nike might file a Jovan lawsuit for trademark sound infringement.

By the way, the probe accelerating has a reverse effect on Jupiter via transfer of momentum, therefore Jupiter slows ever so slightly. Jeez, what if we throw it off its orbit ... (lighten up, space junkies, that was a joke).

Slingshots in space

Anthony, MN — Wed, 02 May 2007 23:45:03 GMT

I’m no physicist but how about merry-go-rounded? You start out slow jump on the merry-go-round; it speeds you up and then throws/pushes you off. Doesn’t that sound simple enough? It does sound of corny though.

Slingshots in space

Amanda Haluska, Donalson, PA — Thu, 03 May 2007 01:43:07 GMT

in school i am talking about space if you find any more stuff tell me i am very interesed

Slingshots in space

David Davis, Houston, TX — Fri, 11 May 2007 16:42:41 GMT

I'm all for calling it a G-boost. Two syllables. Doesn't there have to be some net change in the distance between the two objects in order for the velocity to increase? Or are they purely relying on the relative motion of the planet "moving away" from the craft as it orbits to gain velocity?

Slingshots in space

Walter Parker — Wed, 13 Jun 2007 18:09:20 GMT

It's hard to wrap my brain around gaining or loosing momentum or velocity. I can visualize a change in trajectory. Anyone who has toyed with magnets should. In the exit trajectory, the gravity field pulls against the satellite with as much force as it did in the entry trajectory. Is it due to the speed the satellite is travelling? Is it on its escape trajectory before the effects of its entry into the gravitational field are effected?
But what really troubles me is how can one theorize about a perspective if no one has had the benifit of experiencing that perspective?

Apollo 13 used the Moons gravity in its return trip to Earth. Was there so much going on that there was no relativity data collected? I mean Neil and Buzz didn't notice they were just a few minutes younger than they ought to have been?
Maybe it is due to the 'relative' strength of the gravitational field.

Slingshots in space

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Universal Logistics

Slingshots in space

David Lyttle, Dayton Ohio — Tue, 15 Jan 2008 14:56:15 GMT

I don't care if you call it "Sparky, the Wonder Dog Manuever." This is like arguing over the shape of the peace conference table while a war is going on. Lets get on with the science and get more people out into space!

Slingshots in space

ed — Sat, 01 Mar 2008 18:16:27 GMT

Maybe in the future you could put 2 large/dense objects rotating in opposite directions at high speed with a "gap" in between them. Picture a pitching machine, 2 discs rotating at high speed with a "gap" in the center for the "ball". The ball rolls between the gap and is caught/pinched and pushed out the front like a canon. would it work? The pinch would be the "gravity" of the 2 rotating bodies/objects. I'm talking about having 2 planet sized disks (left=counterclockwise, and the right clockwise. Then again, gravity would probably squish the probe/ship and send out a long spaghetti-like streamer rocketing thru space. lol