Old Rockets Carry Bacteria to the Stars
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I meant if the rocket stages were separated from the probes 20 years ago, they should have fallen back into the solar system pull. I thought the probes left the solar system only a few years ago? So if the stages did leave solar orbit too, then they must have been released fairly recently and not 20 years ago when they were all still within the solar system.
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Bassam Abdul-Baki wrote:
if the rocket stages were separated from the probes 20 years ago, they should have fallen back into the solar system pull.
As mentioned this is a function of velocity. Acceleration, or gravity reduces velocity until you leave the gravitational influence. If velocity exceeds the point where gravity can reduce it before reaching the end of gravitational influence, then that object will continue on, it has reached escape velocity. If you do not reach escape velocity of the earth, you fall back to the earth, if you escape the gravitational influence of the earth, you are still within the gravitational influence of the sun (the big bully of the solar system ... always throwing around its mass), and will fall into the sun. But if you leave the gravitational influence of the sun, or at least reach solar system escape velocity, you will continue to slow until leaving the gravitational influence and then continue at near the same velocity until captured by another gravitational influence. The boosters brought the probes' velocities up to solar system escape velocity during boost phase. When this velocity was achieved the probe was released. Both would have continued on the same vector out of the solar system missing all the planets. But the probes had minor engines for minor navigation, so they slowly turned to their paths. The bounce around slingshots entering and leaving other gravitational influences, but that increases velocity on the entry vector and decreases the velocity on the exit vector, but the net effect is nil because the probe is already too fast to be slowed. Outside of crashing into something the probes continue at an escape velocity as do the boosters that got them to speed, only the direction changes on the probles, not the velocity. the probes will be at very close to the same velocity as the booster stages even decades later, all they did was turn here and there.
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
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Marc Clifton wrote:
Well, the idea is, we don't want to infect other planets that might be harboring life, even if that life is alien and the chances are really small.
Oh, sure. When the aliens get pissed off at us for dumping old rockets on their heads, they'll be plenty healthy enough to retaliate. Good plan, NASA... :rolleyes:
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i hope you are feeling sleepy for people not calling you by the same.
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Shog9 wrote:
When the aliens get pissed off at us for dumping old rockets on their heads
Naw, we'll seed new life on another planet that will grow up pissed at being neglected and come back to boot their parents out of the solar system. ;P
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
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Rama Krishna Vavilala wrote:
Why sterilize unless the spacecraft was carrying humans?
Remember what happened when the Europeans came to America? Indians practically died off from simple childhood diseases the Europeans brought with them. Well, the idea is, we don't want to infect other planets that might be harboring life, even if that life is alien and the chances are really small. Marc
People are just notoriously impossible. --DavidCrow
There's NO excuse for not commenting your code. -- John Simmons / outlaw programmer
People who say that they will refactor their code later to make it "good" don't understand refactoring, nor the art and craft of programming. -- Josh SmithMarc Clifton wrote:
Well, the idea is, we don't want to infect other planets that might be harboring life, even if that life is alien and the chances are really small.
We also do not want any potential of 'seeding'. The last thing we want is to go looking for life and find our own.
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Marc Clifton wrote:
Well, the idea is, we don't want to infect other planets that might be harboring life, even if that life is alien and the chances are really small.
Oh, sure. When the aliens get pissed off at us for dumping old rockets on their heads, they'll be plenty healthy enough to retaliate. Good plan, NASA... :rolleyes:
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i hope you are feeling sleepy for people not calling you by the same.
--BarnaKol on abusive words
I am more afraid that the aliens should not build a "junkyard monster rocket" with all those old rocket spare parts and come to earth on that. :sigh:
"Hmmm, I wonder if this guy knows about the VCF? That's what all the cool programmers are using according to Jenna Jameson." - Jim Crafton.
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Interesting, I always thought that they had to be further away from the sun for them to make it on momentum alone.
"This perpetual motion machine she made is a joke. It just keeps going faster and faster. Lisa, get in here! In this house, we obey the laws of thermodynamics!" - Homer Simpson Web - Blog - RSS - Math - LinkedIn - BM
Bassam Abdul-Baki wrote:
I always thought that they had to be further away from the sun for them to make it on momentum alone
distance is irrelevant. other than it takes distance for constant slow acceleration to defeat strong gravity (which is acceleration on another vectored direction). If you can create a gun that launches at escape velocity out of the nozzle, it will leave the earth even though it was launched from the earth. This is actually one of the plans for mining the moon I forget the name of the gun. essentially you mine a valuable ore, place it in a metal cage, launch it from a magnetic launch tube (massively high speed short space) and it arcs up out of the lunar influence and can be easily tethered and pulled into a space-station or other vehicle. acceleration -><- gravity: --><- means your acceleration exceeds gravitational influence and are therefore increasing in velocity in respect to the gravity -><-- would mean that your acceleration is enough to decrease gravitation influence, but the gravity is still gradually slowing you down. when you cut engines you have a current velocity state which will slow relative to the inverse square of the distance and the mass of the object. It is true you no longer have acceleration to counter gravitational influence, but If you are A) far enough out or B) fast enough that you cannot be slowed enough, then you will continue indefinitely (or at least until you find someone else to pull you in). The distance really is irrelevant, just the velocity is easier to achieve at the greater distance.
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
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Interesting, I always thought that they had to be further away from the sun for them to make it on momentum alone.
"This perpetual motion machine she made is a joke. It just keeps going faster and faster. Lisa, get in here! In this house, we obey the laws of thermodynamics!" - Homer Simpson Web - Blog - RSS - Math - LinkedIn - BM
All that's needed is to reach escape velocity. The required velocity decreases as you move farther from the sun, but only by the same amount that an object traveling at that velocity would loose as it traveled the same distance outward.
-- You have to explain to them [VB coders] what you mean by "typed". their first response is likely to be something like, "Of course my code is typed. Do you think i magically project it onto the screen with the power of my mind?" --- John Simmons / outlaw programmer
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Bassam Abdul-Baki wrote:
if the rocket stages were separated from the probes 20 years ago, they should have fallen back into the solar system pull.
As mentioned this is a function of velocity. Acceleration, or gravity reduces velocity until you leave the gravitational influence. If velocity exceeds the point where gravity can reduce it before reaching the end of gravitational influence, then that object will continue on, it has reached escape velocity. If you do not reach escape velocity of the earth, you fall back to the earth, if you escape the gravitational influence of the earth, you are still within the gravitational influence of the sun (the big bully of the solar system ... always throwing around its mass), and will fall into the sun. But if you leave the gravitational influence of the sun, or at least reach solar system escape velocity, you will continue to slow until leaving the gravitational influence and then continue at near the same velocity until captured by another gravitational influence. The boosters brought the probes' velocities up to solar system escape velocity during boost phase. When this velocity was achieved the probe was released. Both would have continued on the same vector out of the solar system missing all the planets. But the probes had minor engines for minor navigation, so they slowly turned to their paths. The bounce around slingshots entering and leaving other gravitational influences, but that increases velocity on the entry vector and decreases the velocity on the exit vector, but the net effect is nil because the probe is already too fast to be slowed. Outside of crashing into something the probes continue at an escape velocity as do the boosters that got them to speed, only the direction changes on the probles, not the velocity. the probes will be at very close to the same velocity as the booster stages even decades later, all they did was turn here and there.
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
Thanks for the info. I understood all that, but my problem was with when this happened more than how. I thought that the rockets & boosters only got to escape velocity somewhere close to the outer rim of the solar system which would mean, I think, more recently (I assume they only escaped the solar system within the last decade). However, it makes sense that escape velocity was reached when they orbited the last known planet for slingshot effect, which would mean Jupiter from a long time ago. Did the probe dump the boosters before the slingshot around the planet or after?
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Thanks for the info. I understood all that, but my problem was with when this happened more than how. I thought that the rockets & boosters only got to escape velocity somewhere close to the outer rim of the solar system which would mean, I think, more recently (I assume they only escaped the solar system within the last decade). However, it makes sense that escape velocity was reached when they orbited the last known planet for slingshot effect, which would mean Jupiter from a long time ago. Did the probe dump the boosters before the slingshot around the planet or after?
"Patriotism is the last refuge of a scoundrel." - Samuel Johnson Web - Blog - RSS - Math - LinkedIn - BM
Bassam Abdul-Baki wrote:
I understood all that, but my problem was with when this happened more than how
Then you really aren't understanding the how either. The boosters were dropped before the very first planetary navigation. Speed was acheived first, the the probes released to travel to the planets. The sling shot is only a change in direction, nothing more. The issue you have, I think, is believing escape velocity == the point of leaving gravitational influence. We'll reduce the example to make it simpler, drop back to earth which once was the center of the solar system anyhow ;) You stand on the earth with a gravitational influence of 9.8m/s2 exerted on your person. Lets say you have a REALLY big gun. You fire the gun up at shell velocity of 11.2 kilometers a second. Even though the shell has no propulsion (the gun has the propulsion) the shell will leave the earth's gravitational field and fall into the sun. BUT if you slowly lift your craft by accelerating upwards, as you get higher from the earth you need less velocity to escape the earth's gravity. Theoretically you can make a slow lift vehicle that simply has an acceleration of 10 m/s2 and it will slowly rise. If at the point where you loose acceleration, your velocity exceeds the escape velocity at that location (gravity reduces on an inverse square of distance), you will escape the gravity of the earth. This is exactly how the probes worked. the boost phase was a long slow acceleration to get both distance and velocity. The farther out, the less velocity is needed to escape the sun, so a long-slow boost achieved both velocity and distance when the velocity exceeded escape velocity for that location, the engines were dropped and continued on out of the solar system. The probes turned and zigged and zagged through the solar system still staying at the same velocity of the booster. Both will slow, but will not slow to 0 before leaving the influence of the sun. Once they leave, they're free.
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
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Bassam Abdul-Baki wrote:
I always thought that they had to be further away from the sun for them to make it on momentum alone
distance is irrelevant. other than it takes distance for constant slow acceleration to defeat strong gravity (which is acceleration on another vectored direction). If you can create a gun that launches at escape velocity out of the nozzle, it will leave the earth even though it was launched from the earth. This is actually one of the plans for mining the moon I forget the name of the gun. essentially you mine a valuable ore, place it in a metal cage, launch it from a magnetic launch tube (massively high speed short space) and it arcs up out of the lunar influence and can be easily tethered and pulled into a space-station or other vehicle. acceleration -><- gravity: --><- means your acceleration exceeds gravitational influence and are therefore increasing in velocity in respect to the gravity -><-- would mean that your acceleration is enough to decrease gravitation influence, but the gravity is still gradually slowing you down. when you cut engines you have a current velocity state which will slow relative to the inverse square of the distance and the mass of the object. It is true you no longer have acceleration to counter gravitational influence, but If you are A) far enough out or B) fast enough that you cannot be slowed enough, then you will continue indefinitely (or at least until you find someone else to pull you in). The distance really is irrelevant, just the velocity is easier to achieve at the greater distance.
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
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.
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Bassam Abdul-Baki wrote:
I understood all that, but my problem was with when this happened more than how
Then you really aren't understanding the how either. The boosters were dropped before the very first planetary navigation. Speed was acheived first, the the probes released to travel to the planets. The sling shot is only a change in direction, nothing more. The issue you have, I think, is believing escape velocity == the point of leaving gravitational influence. We'll reduce the example to make it simpler, drop back to earth which once was the center of the solar system anyhow ;) You stand on the earth with a gravitational influence of 9.8m/s2 exerted on your person. Lets say you have a REALLY big gun. You fire the gun up at shell velocity of 11.2 kilometers a second. Even though the shell has no propulsion (the gun has the propulsion) the shell will leave the earth's gravitational field and fall into the sun. BUT if you slowly lift your craft by accelerating upwards, as you get higher from the earth you need less velocity to escape the earth's gravity. Theoretically you can make a slow lift vehicle that simply has an acceleration of 10 m/s2 and it will slowly rise. If at the point where you loose acceleration, your velocity exceeds the escape velocity at that location (gravity reduces on an inverse square of distance), you will escape the gravity of the earth. This is exactly how the probes worked. the boost phase was a long slow acceleration to get both distance and velocity. The farther out, the less velocity is needed to escape the sun, so a long-slow boost achieved both velocity and distance when the velocity exceeded escape velocity for that location, the engines were dropped and continued on out of the solar system. The probes turned and zigged and zagged through the solar system still staying at the same velocity of the booster. Both will slow, but will not slow to 0 before leaving the influence of the sun. Once they leave, they're free.
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
Actually, I understand the concept that the acceleration needed to be greater than the gravitational influence, however, I did not realize that the slingshots were for direction only. I assumed a gravitational pull will increase speed, but would cancel out like you said on exit. My other issue was with:
El Corazon wrote:
Both will slow, but will not slow to 0 before leaving the influence of the sun. Once they leave, they're free.
If the booster is gone and velocity is only based upon initial velocity and momentum, then in theory, shouldn't the sun's pull bring them back in in a few hundred years? I am assuming that 1) there's no acceleration, 2) constant velocity, 3) some drag that will slow down that velocity eventually. Pull from another solar system should be negligible compared to our own.
"You can lead a horse to Vista, but it won't get in stall." - Bassam Abdul-Baki Web - Blog - RSS - Math - LinkedIn - BM
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Bassam Abdul-Baki wrote:
I thought that without thrust, they'd fall back in?
Those particular rocket motors were used to boost four space probes so that they could escape the solar system, so the rockets have nearly the same velocity as well. Marc
People are just notoriously impossible. --DavidCrow
There's NO excuse for not commenting your code. -- John Simmons / outlaw programmer
People who say that they will refactor their code later to make it "good" don't understand refactoring, nor the art and craft of programming. -- Josh SmithWhatever happened when over ten million years ago or so comets and space debris seeded our nice little home with amoebas and other bacteria? OOps , sorry those were my predecessors.
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Bassam Abdul-Baki wrote:
I understood all that, but my problem was with when this happened more than how
Then you really aren't understanding the how either. The boosters were dropped before the very first planetary navigation. Speed was acheived first, the the probes released to travel to the planets. The sling shot is only a change in direction, nothing more. The issue you have, I think, is believing escape velocity == the point of leaving gravitational influence. We'll reduce the example to make it simpler, drop back to earth which once was the center of the solar system anyhow ;) You stand on the earth with a gravitational influence of 9.8m/s2 exerted on your person. Lets say you have a REALLY big gun. You fire the gun up at shell velocity of 11.2 kilometers a second. Even though the shell has no propulsion (the gun has the propulsion) the shell will leave the earth's gravitational field and fall into the sun. BUT if you slowly lift your craft by accelerating upwards, as you get higher from the earth you need less velocity to escape the earth's gravity. Theoretically you can make a slow lift vehicle that simply has an acceleration of 10 m/s2 and it will slowly rise. If at the point where you loose acceleration, your velocity exceeds the escape velocity at that location (gravity reduces on an inverse square of distance), you will escape the gravity of the earth. This is exactly how the probes worked. the boost phase was a long slow acceleration to get both distance and velocity. The farther out, the less velocity is needed to escape the sun, so a long-slow boost achieved both velocity and distance when the velocity exceeded escape velocity for that location, the engines were dropped and continued on out of the solar system. The probes turned and zigged and zagged through the solar system still staying at the same velocity of the booster. Both will slow, but will not slow to 0 before leaving the influence of the sun. Once they leave, they're free.
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
El Corazon wrote:
The sling shot is only a change in direction, nothing more.
That is incorrect. The slingshot can be modeled by a simple elastic collision with a small body and a very massive body. Imagine throwing a rock at a train heading towards you. That rock is going to bounce back traveling faster then the train. From wikipedia: http://en.wikipedia.org/wiki/Gravitational_slingshot[^] In orbital mechanics and aerospace engineering, a gravitational slingshot or gravity assist is the use of the gravity of a planet or other celestial body to alter the path and speed of an interplanetary spacecraft. It is a commonly used maneuver for visiting the outer planets, which would otherwise either take far too long or require far too much fuel using our current propulsion technologies. It was first developed in 1959 at the Department of Applied Mathematics of Steklov Institute.[1]
Using the GridView is like trying to explain to someone else how to move a third person's hands in order to tie your shoelaces for you. -Chris Maunder
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Actually, I understand the concept that the acceleration needed to be greater than the gravitational influence, however, I did not realize that the slingshots were for direction only. I assumed a gravitational pull will increase speed, but would cancel out like you said on exit. My other issue was with:
El Corazon wrote:
Both will slow, but will not slow to 0 before leaving the influence of the sun. Once they leave, they're free.
If the booster is gone and velocity is only based upon initial velocity and momentum, then in theory, shouldn't the sun's pull bring them back in in a few hundred years? I am assuming that 1) there's no acceleration, 2) constant velocity, 3) some drag that will slow down that velocity eventually. Pull from another solar system should be negligible compared to our own.
"You can lead a horse to Vista, but it won't get in stall." - Bassam Abdul-Baki Web - Blog - RSS - Math - LinkedIn - BM
Bassam Abdul-Baki wrote:
I am assuming that 1) there's no acceleration, 2) constant velocity, 3) some drag that will slow down that velocity eventually.
there is no drag. Only acceleration of gravity (or deceleration since opposite vectors) and current velocity. I must be explaining it poorly. I know I am too close to the visualization side of this type of stuff, so maybe I am being too technical, I don't know. The probes had no engines except for navigation, no acceleration of vehicles, the boosters referred to in the article provided ALL of the acceleration to reach escape velocity, therefore both probes and booster are at escape velocity. The probes turned, the boosters didn't both travelling continually out of the solar system at equal velocities. The sling-shots were navigation assists, allowing minute vectors to be increased in magnitude by the sling-shot effect around a planet. If the boosters fell back, so would the probes, because the booster provided the necessary speed and vice versa, if the boosters fell back, so would the probes. Because both achieved the right velocity much earlier, both will leave. Maybe someone else can help me here, I don't know an easier way to explain it.
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
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Actually, I understand the concept that the acceleration needed to be greater than the gravitational influence, however, I did not realize that the slingshots were for direction only. I assumed a gravitational pull will increase speed, but would cancel out like you said on exit. My other issue was with:
El Corazon wrote:
Both will slow, but will not slow to 0 before leaving the influence of the sun. Once they leave, they're free.
If the booster is gone and velocity is only based upon initial velocity and momentum, then in theory, shouldn't the sun's pull bring them back in in a few hundred years? I am assuming that 1) there's no acceleration, 2) constant velocity, 3) some drag that will slow down that velocity eventually. Pull from another solar system should be negligible compared to our own.
"You can lead a horse to Vista, but it won't get in stall." - Bassam Abdul-Baki Web - Blog - RSS - Math - LinkedIn - BM
If the gravitational force decreased less slowly then an inverse square that would be true. For example the constant gravitational force approximation used in basic physics for motion close to the earth has an infinite escape velocity. However because the force of gravity falls off so quickly with distance there is a finite energy needed for any object to reach infinity under that type of force. Check out this: http://en.wikipedia.org/wiki/Escape_velocity[^] Also for later spacecraft they try to follow these trajectories: http://en.wikipedia.org/wiki/Interplanetary_Superhighway[^] but they take a computer to compute. A gravitational slingshot is just a simple example of that.
Using the GridView is like trying to explain to someone else how to move a third person's hands in order to tie your shoelaces for you. -Chris Maunder
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Actually, I understand the concept that the acceleration needed to be greater than the gravitational influence, however, I did not realize that the slingshots were for direction only. I assumed a gravitational pull will increase speed, but would cancel out like you said on exit. My other issue was with:
El Corazon wrote:
Both will slow, but will not slow to 0 before leaving the influence of the sun. Once they leave, they're free.
If the booster is gone and velocity is only based upon initial velocity and momentum, then in theory, shouldn't the sun's pull bring them back in in a few hundred years? I am assuming that 1) there's no acceleration, 2) constant velocity, 3) some drag that will slow down that velocity eventually. Pull from another solar system should be negligible compared to our own.
"You can lead a horse to Vista, but it won't get in stall." - Bassam Abdul-Baki Web - Blog - RSS - Math - LinkedIn - BM
You are right that the booster will slow down since the sun is constantly "pulling". But the velocity will never change direction. If the velocity (at one point) is equal to the escape velocity (for that point), that means that as the distance increases, the velocity gets lower. But the escape velocity is also lower for higher distances, so the booster still has escape velocity. As the distance to the sun approaches infinity, the velocity will approach zero, but it'll never change direction. EDIT: It's easier to understand using the formula for potential energy: Epot = G*m1*m2*(1/r1 - 1/r2) This is the energy required to bring a body from radius r1 to r2. If you set r2 = infinity, you see that you only need the finite amount of energy (G*m1*m2*(1/r1)) to shoot body infinitely far. That amount of energy is the kinetic energy of the escape velocity.
Last modified: 7mins after originally posted --
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Bassam Abdul-Baki wrote:
I am assuming that 1) there's no acceleration, 2) constant velocity, 3) some drag that will slow down that velocity eventually.
there is no drag. Only acceleration of gravity (or deceleration since opposite vectors) and current velocity. I must be explaining it poorly. I know I am too close to the visualization side of this type of stuff, so maybe I am being too technical, I don't know. The probes had no engines except for navigation, no acceleration of vehicles, the boosters referred to in the article provided ALL of the acceleration to reach escape velocity, therefore both probes and booster are at escape velocity. The probes turned, the boosters didn't both travelling continually out of the solar system at equal velocities. The sling-shots were navigation assists, allowing minute vectors to be increased in magnitude by the sling-shot effect around a planet. If the boosters fell back, so would the probes, because the booster provided the necessary speed and vice versa, if the boosters fell back, so would the probes. Because both achieved the right velocity much earlier, both will leave. Maybe someone else can help me here, I don't know an easier way to explain it.
_________________________ Asu no koto o ieba, tenjo de nezumi ga warau. Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
El Corazon wrote:
I must be explaining it poorly. I know I am too close to the visualization side of this type of stuff, so maybe I am being too technical, I don't know.
No, I got it, finally. But for some reason, I always thought there is drag from solar winds, dust, and other stuff.
El Corazon wrote:
The probes had no engines except for navigation, no acceleration of vehicles, the boosters referred to in the article provided ALL of the acceleration to reach escape velocity, therefore both probes and booster are at escape velocity. The probes turned, the boosters didn't both travelling continually out of the solar system at equal velocities.
Unless there is absolutely no drag, I would expect that, but with no engines, they would eventually slow down. It would be interesting to know what there speeds where 20+ years ago, after separation, with what they are today. I guess we can't know for sure.
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If the gravitational force decreased less slowly then an inverse square that would be true. For example the constant gravitational force approximation used in basic physics for motion close to the earth has an infinite escape velocity. However because the force of gravity falls off so quickly with distance there is a finite energy needed for any object to reach infinity under that type of force. Check out this: http://en.wikipedia.org/wiki/Escape_velocity[^] Also for later spacecraft they try to follow these trajectories: http://en.wikipedia.org/wiki/Interplanetary_Superhighway[^] but they take a computer to compute. A gravitational slingshot is just a simple example of that.
Using the GridView is like trying to explain to someone else how to move a third person's hands in order to tie your shoelaces for you. -Chris Maunder
Andy Brummer wrote:
However because the force of gravity falls off so quickly with distance there is a finite energy needed for any object to reach infinity under that type of force.
That explains it.
Andy Brummer wrote:
Also for later spacecraft they try to follow these trajectories: http://en.wikipedia.org/wiki/Interplanetary\_Superhighway\[^\] but they take a computer to compute. A gravitational slingshot is just a simple example of that.
Wow! :cool:
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El Corazon wrote:
The sling shot is only a change in direction, nothing more.
That is incorrect. The slingshot can be modeled by a simple elastic collision with a small body and a very massive body. Imagine throwing a rock at a train heading towards you. That rock is going to bounce back traveling faster then the train. From wikipedia: http://en.wikipedia.org/wiki/Gravitational_slingshot[^] In orbital mechanics and aerospace engineering, a gravitational slingshot or gravity assist is the use of the gravity of a planet or other celestial body to alter the path and speed of an interplanetary spacecraft. It is a commonly used maneuver for visiting the outer planets, which would otherwise either take far too long or require far too much fuel using our current propulsion technologies. It was first developed in 1959 at the Department of Applied Mathematics of Steklov Institute.[1]
Using the GridView is like trying to explain to someone else how to move a third person's hands in order to tie your shoelaces for you. -Chris Maunder
Your bolded stuff cleared up Jeffrey's post from a few back that said: The bounce around slingshots entering and leaving other gravitational influences, but that increases velocity on the entry vector and decreases the velocity on the exit vector, but the net effect is nil because the probe is already too fast to be slowed. So technically, slingshots do speed up probes?
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Actually, I understand the concept that the acceleration needed to be greater than the gravitational influence, however, I did not realize that the slingshots were for direction only. I assumed a gravitational pull will increase speed, but would cancel out like you said on exit. My other issue was with:
El Corazon wrote:
Both will slow, but will not slow to 0 before leaving the influence of the sun. Once they leave, they're free.
If the booster is gone and velocity is only based upon initial velocity and momentum, then in theory, shouldn't the sun's pull bring them back in in a few hundred years? I am assuming that 1) there's no acceleration, 2) constant velocity, 3) some drag that will slow down that velocity eventually. Pull from another solar system should be negligible compared to our own.
"You can lead a horse to Vista, but it won't get in stall." - Bassam Abdul-Baki Web - Blog - RSS - Math - LinkedIn - BM
Bassam Abdul-Baki wrote:
If the booster is gone and velocity is only based upon initial velocity and momentum, then in theory, shouldn't the sun's pull bring them back in in a few hundred years?
It had enough initial speed that it is able to escape the sun's pull completely. Once it escapes, the sun is not pulling on it anymore, so it will never return, ever. That's why it is called "escape" velocity. It is the initial velocity that allows it to get far enough away that it is beyond the reach of the sun.
-------------------------------- "All that is necessary for the forces of evil to win in the world is for enough good men to do nothing" -- Edmund Burke
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You are right that the booster will slow down since the sun is constantly "pulling". But the velocity will never change direction. If the velocity (at one point) is equal to the escape velocity (for that point), that means that as the distance increases, the velocity gets lower. But the escape velocity is also lower for higher distances, so the booster still has escape velocity. As the distance to the sun approaches infinity, the velocity will approach zero, but it'll never change direction. EDIT: It's easier to understand using the formula for potential energy: Epot = G*m1*m2*(1/r1 - 1/r2) This is the energy required to bring a body from radius r1 to r2. If you set r2 = infinity, you see that you only need the finite amount of energy (G*m1*m2*(1/r1)) to shoot body infinitely far. That amount of energy is the kinetic energy of the escape velocity.
Last modified: 7mins after originally posted --
Thanks, that is easier for layman's. Andy's statement: However because the force of gravity falls off so quickly with distance there is a finite energy needed for any object to reach infinity under that type of force. also cleared it up.
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