Old Rockets Carry Bacteria to the Stars
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El Corazon wrote:
constant slow acceleration
That's what I was missing. I thought the probes had no real engines, path correction only, and were moving on constant velocities.
"There are II kinds of people in the world, those who understand binary and those who understand Roman numerals." - Bassam Abdul-Baki Web - Blog - RSS - Math - LinkedIn - BM
No probe that is on a trajectory that will carry it from our solar system has significant propulsive capability after the last injection burn to take it towards it target(s). You can measure it in the 100s if not 10s of meters per second. The only vehicles that can provide small continual thrust are those that employ Electric Propulsion, the most prevalent in probes at the moment is xenon gridded ion engines and xenon hall-effect thrusters. These rely on solar arrays for power and these are the vehicles El Corazon was referring to. Pioneer 10, Voyagers 1 and 2 and New Horizons are comparitively very small and light vehicles, which is required in order to send them, even with gravity assist manuevers, to an escape velocity from our system.
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Very good explanation. I only have a question about one thing. You stated:
El Corazon wrote:
The sling-shots were navigation assists, allowing minute vectors to be increased in magnitude by the sling-shot effect around a planet.
At least in a couple of posts, you said that the "sling-shots" did not increase the spacecraft's acceleration. However, at http://www.planetary.org/news/2007/0118_New_Horizons_to_Test_its_Mettle_during.html[^] (which was obviously written before the Jupiter flyby), the author states: "As it swings by Jupiter, the planet’s enormous gravitational pull will give the spacecraft a boost that will increase its speed by 9000 miles per hour (5600 kilometers per hour) relative to the Sun. This gravity assist will cut a full three years from New Horizons’ journey, bringing it down to a mere 9 years." Is the key phrase here "relative to the Sun"?:confused: Cheers,
I would like to say that you noticed the right wording. Relative to Jupiter the hyperbolic velocity (Vhp) is the same before and after the manuever. It is the direction that is different which you add to the vector of Jupiter's orbital velocity to learn the effect. I would like to point out that the website has the units transposed. Jupiter is a deep enough gravity well that it is possible to get almost 180 degree turns in the Jupiter relative frame depending on the hyperbolic velocity. Gravity assist manuevers can be used just for navigation, but it also is the oldest trick in a mission designer's arsenal for getting someplace that you don't have the launch capacity to get to otherwise. Hyperbolic excess velocity is the velocity an object has relative to an gravity source when it is no longer under the gravity source's field (at infinity). For all intents and purposes, you can say that this velocity occurs at a body's sphere of influence (where the gravity and kinetic energy of a body is equivalent or greater than the gravity of the body it is orbiting). Hopefully these crude pictures will help explain: http://i59.photobucket.com/albums/g307/gerthdynn/gravityassist-small.gif http://i59.photobucket.com/albums/g307/gerthdynn/jupiter-assist-sun-relative-small.gif[^] As you can see, the inbound and exit hyperbolic velocity vectors are equal in the first picture. The mass of the planet, radius of the flyby and the magnitude of the hyperbolic excess velocity determine the turn angle. The effect in the sun relative frame is shown in the second picture.
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I would like to say that you noticed the right wording. Relative to Jupiter the hyperbolic velocity (Vhp) is the same before and after the manuever. It is the direction that is different which you add to the vector of Jupiter's orbital velocity to learn the effect. I would like to point out that the website has the units transposed. Jupiter is a deep enough gravity well that it is possible to get almost 180 degree turns in the Jupiter relative frame depending on the hyperbolic velocity. Gravity assist manuevers can be used just for navigation, but it also is the oldest trick in a mission designer's arsenal for getting someplace that you don't have the launch capacity to get to otherwise. Hyperbolic excess velocity is the velocity an object has relative to an gravity source when it is no longer under the gravity source's field (at infinity). For all intents and purposes, you can say that this velocity occurs at a body's sphere of influence (where the gravity and kinetic energy of a body is equivalent or greater than the gravity of the body it is orbiting). Hopefully these crude pictures will help explain: http://i59.photobucket.com/albums/g307/gerthdynn/gravityassist-small.gif http://i59.photobucket.com/albums/g307/gerthdynn/jupiter-assist-sun-relative-small.gif[^] As you can see, the inbound and exit hyperbolic velocity vectors are equal in the first picture. The mass of the planet, radius of the flyby and the magnitude of the hyperbolic excess velocity determine the turn angle. The effect in the sun relative frame is shown in the second picture.
firegryphon wrote:
It is the direction that is different which you add to the vector of Jupiter's orbital velocity to learn the effect.
So then it is the orbital velocity that gets added to the spacecraft's velocity, rather than the rotational velocity of the planet, as someone else stated farther down. That makes more sense to me. Cool! :) I knew all the rocket scientists hung out at Code Project! ;) Cheers,
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firegryphon wrote:
It is the direction that is different which you add to the vector of Jupiter's orbital velocity to learn the effect.
So then it is the orbital velocity that gets added to the spacecraft's velocity, rather than the rotational velocity of the planet, as someone else stated farther down. That makes more sense to me. Cool! :) I knew all the rocket scientists hung out at Code Project! ;) Cheers,
Bleh... you sound like my dad. I'm just an interplanetary mission designer specializing in low thrust trajectory analysis ;) As far as I can remember the only way you are going to get an effect from the rotational velocity of the planet is via Frame Dragging.
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Bleh... you sound like my dad. I'm just an interplanetary mission designer specializing in low thrust trajectory analysis ;) As far as I can remember the only way you are going to get an effect from the rotational velocity of the planet is via Frame Dragging.
Every satellite launched into Earth orbit get's a rotational effect, doesn't it? You don't see many satellites in retrograde orbits. :)
WE ARE DYSLEXIC OF BORG. Refutance is systile. Your a$$ will be laminated.
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Every satellite launched into Earth orbit get's a rotational effect, doesn't it? You don't see many satellites in retrograde orbits. :)
WE ARE DYSLEXIC OF BORG. Refutance is systile. Your a$$ will be laminated.
Bleh again... Yes taken out of context. Though you can negate that by launching from the poles. I thought about it more and it should be possible to get some insignificant fraction of your velocity due to non-uniformity and non-sphericity. I personally would never waste the computational resources on it for a mission, but you have to calculate it in order to predict the Moon's gradual orbit radius increase [edit: increases about 3 cm per year for reference]. Tidal effects... gotta love em.
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Bleh again... Yes taken out of context. Though you can negate that by launching from the poles. I thought about it more and it should be possible to get some insignificant fraction of your velocity due to non-uniformity and non-sphericity. I personally would never waste the computational resources on it for a mission, but you have to calculate it in order to predict the Moon's gradual orbit radius increase [edit: increases about 3 cm per year for reference]. Tidal effects... gotta love em.
Sorry. I guess I am a moron.:^):(:sigh:
WE ARE DYSLEXIC OF BORG. Refutance is systile. Your a$$ will be laminated.
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Sorry. I guess I am a moron.:^):(:sigh:
WE ARE DYSLEXIC OF BORG. Refutance is systile. Your a$$ will be laminated.
moron? I would never say that. I had to think on the problem for a while through fever induced haze before coming up with that answer. Which should go to tell you, don't trust anything I say until I stop being ill.
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moron? I would never say that. I had to think on the problem for a while through fever induced haze before coming up with that answer. Which should go to tell you, don't trust anything I say until I stop being ill.
Sorry to hear you are ill.:( I hope you get better soon so that you can get back to your "low thrust trajectory analysis". Sounds like you must work for JPL or somewhere like that. Thanks for the dialog. Get well soon.
WE ARE DYSLEXIC OF BORG. Refutance is systile. Your a$$ will be laminated.
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Good book, but I think that one worked itself out at the end. Can't remember the ending well.
"He who joyfully marches to music in rank and file has already earned my contempt. He has been given a large brain by mistake, since for him, the spinal cord would fully suffice. This disgrace to civilization should be done away with at once. Heroism at command, senseless brutality, deplorable love-of-country stance, how violently I hate all this, how despicable an ignorable war is; I would rather be torn to shreds than be a part of so base an action! It is my conviction that killing under the cloak of war is nothing but an act of murder." - Albert Einstein Web - Blog - RSS - Math - LinkedIn - BM
I read your Einstein quote and it didn't quite make sense to me so I checked. Where you have "an ignorable war" it should be "an ignoble war". cheers
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I read your Einstein quote and it didn't quite make sense to me so I checked. Where you have "an ignorable war" it should be "an ignoble war". cheers
Good catch.
"He who joyfully marches to music in rank and file has already earned my contempt. He has been given a large brain by mistake, since for him, the spinal cord would fully suffice. This disgrace to civilization should be done away with at once. Heroism at command, senseless brutality, deplorable love-of-country stance, how violently I hate all this, how despicable an ignoble war is; I would rather be torn to shreds than be a part of so base an action! It is my conviction that killing under the cloak of war is nothing but an act of murder." - Albert Einstein Web - Blog - RSS - Math - LinkedIn - BM
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I saw it recently, They discovered that the pathogen was very susceptible to small changes in pH. The baby crying and the drunks digestive system made both their blood acidic, making them be the only survivors of the initial outbreak and eventually leading to the connection. Great film
Philosophy: The art of never getting beyond the concept of life.
TClarke wrote:
made both their blood acidic,
Actually one was acid and the other alkali which initially confised the investigators until they worked out it could only survive in a narrow range of values.
