Did Apollo's velocity slow down after TLI due to Earth's gravity?












1














I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating. Did it start accelerating as it approached the Moon. What was the rate of deceleration due to Earth's gravity?






the-moon crewed-spaceflight apollo-program trajectory







share|improve this question
























  • What do you mean? Rate of deceleration at what point? Much of the lunar transfer is unpowered. Can you clarify.
    – Rory Alsop
    6 hours ago










  • @RoryAlsop I did not say powered deceleration. The velocity of Apollo changed from TLI to until Lunar orbit insertion due to the gravity of the Earth and presumably the Moon. What what that rate of change?
    – Bob516
    6 hours ago






  • 2




    While the question could have been better formulated, I don't feel it merits being down voted, as judging on the basis of OP's record here, it was asked in good faith. What seems obvious to ourselves might not to somebody else, and that is something all of us ought to keep in mind when interacting here.
    – Happy Koala
    6 hours ago










  • @HappyKoala wouldn't it be cool to have some kind of program or website where you could click a button that plots separation from Earth and separation from Moon versus time on the same axis? Or a pair of plots with the distances in the first and their rates of change in the second? It could be called plot range-rate analogous to real delay-doppler measurements.
    – uhoh
    2 hours ago


















1














I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating. Did it start accelerating as it approached the Moon. What was the rate of deceleration due to Earth's gravity?






the-moon crewed-spaceflight apollo-program trajectory







share|improve this question
























  • What do you mean? Rate of deceleration at what point? Much of the lunar transfer is unpowered. Can you clarify.
    – Rory Alsop
    6 hours ago










  • @RoryAlsop I did not say powered deceleration. The velocity of Apollo changed from TLI to until Lunar orbit insertion due to the gravity of the Earth and presumably the Moon. What what that rate of change?
    – Bob516
    6 hours ago






  • 2




    While the question could have been better formulated, I don't feel it merits being down voted, as judging on the basis of OP's record here, it was asked in good faith. What seems obvious to ourselves might not to somebody else, and that is something all of us ought to keep in mind when interacting here.
    – Happy Koala
    6 hours ago










  • @HappyKoala wouldn't it be cool to have some kind of program or website where you could click a button that plots separation from Earth and separation from Moon versus time on the same axis? Or a pair of plots with the distances in the first and their rates of change in the second? It could be called plot range-rate analogous to real delay-doppler measurements.
    – uhoh
    2 hours ago
















1












1








1







I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating. Did it start accelerating as it approached the Moon. What was the rate of deceleration due to Earth's gravity?






the-moon crewed-spaceflight apollo-program trajectory







share|improve this question















I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating. Did it start accelerating as it approached the Moon. What was the rate of deceleration due to Earth's gravity?






the-moon crewed-spaceflight apollo-program trajectory




the-moon crewed-spaceflight apollo-program trajectory






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 5 hours ago









PearsonArtPhoto♦

80.5k16230443




80.5k16230443










asked 6 hours ago









Bob516Bob516

1,4171316




1,4171316












  • What do you mean? Rate of deceleration at what point? Much of the lunar transfer is unpowered. Can you clarify.
    – Rory Alsop
    6 hours ago










  • @RoryAlsop I did not say powered deceleration. The velocity of Apollo changed from TLI to until Lunar orbit insertion due to the gravity of the Earth and presumably the Moon. What what that rate of change?
    – Bob516
    6 hours ago






  • 2




    While the question could have been better formulated, I don't feel it merits being down voted, as judging on the basis of OP's record here, it was asked in good faith. What seems obvious to ourselves might not to somebody else, and that is something all of us ought to keep in mind when interacting here.
    – Happy Koala
    6 hours ago










  • @HappyKoala wouldn't it be cool to have some kind of program or website where you could click a button that plots separation from Earth and separation from Moon versus time on the same axis? Or a pair of plots with the distances in the first and their rates of change in the second? It could be called plot range-rate analogous to real delay-doppler measurements.
    – uhoh
    2 hours ago




















  • What do you mean? Rate of deceleration at what point? Much of the lunar transfer is unpowered. Can you clarify.
    – Rory Alsop
    6 hours ago










  • @RoryAlsop I did not say powered deceleration. The velocity of Apollo changed from TLI to until Lunar orbit insertion due to the gravity of the Earth and presumably the Moon. What what that rate of change?
    – Bob516
    6 hours ago






  • 2




    While the question could have been better formulated, I don't feel it merits being down voted, as judging on the basis of OP's record here, it was asked in good faith. What seems obvious to ourselves might not to somebody else, and that is something all of us ought to keep in mind when interacting here.
    – Happy Koala
    6 hours ago










  • @HappyKoala wouldn't it be cool to have some kind of program or website where you could click a button that plots separation from Earth and separation from Moon versus time on the same axis? Or a pair of plots with the distances in the first and their rates of change in the second? It could be called plot range-rate analogous to real delay-doppler measurements.
    – uhoh
    2 hours ago


















What do you mean? Rate of deceleration at what point? Much of the lunar transfer is unpowered. Can you clarify.
– Rory Alsop
6 hours ago




What do you mean? Rate of deceleration at what point? Much of the lunar transfer is unpowered. Can you clarify.
– Rory Alsop
6 hours ago












@RoryAlsop I did not say powered deceleration. The velocity of Apollo changed from TLI to until Lunar orbit insertion due to the gravity of the Earth and presumably the Moon. What what that rate of change?
– Bob516
6 hours ago




@RoryAlsop I did not say powered deceleration. The velocity of Apollo changed from TLI to until Lunar orbit insertion due to the gravity of the Earth and presumably the Moon. What what that rate of change?
– Bob516
6 hours ago




2




2




While the question could have been better formulated, I don't feel it merits being down voted, as judging on the basis of OP's record here, it was asked in good faith. What seems obvious to ourselves might not to somebody else, and that is something all of us ought to keep in mind when interacting here.
– Happy Koala
6 hours ago




While the question could have been better formulated, I don't feel it merits being down voted, as judging on the basis of OP's record here, it was asked in good faith. What seems obvious to ourselves might not to somebody else, and that is something all of us ought to keep in mind when interacting here.
– Happy Koala
6 hours ago












@HappyKoala wouldn't it be cool to have some kind of program or website where you could click a button that plots separation from Earth and separation from Moon versus time on the same axis? Or a pair of plots with the distances in the first and their rates of change in the second? It could be called plot range-rate analogous to real delay-doppler measurements.
– uhoh
2 hours ago






@HappyKoala wouldn't it be cool to have some kind of program or website where you could click a button that plots separation from Earth and separation from Moon versus time on the same axis? Or a pair of plots with the distances in the first and their rates of change in the second? It could be called plot range-rate analogous to real delay-doppler measurements.
– uhoh
2 hours ago












2 Answers
2






active

oldest

votes


















3














Yes, in fact it did slow down with time, until it approached close enough that the Moon pulled it faster. That happened at a point very close to the Moon. In a diagram on this page, for Apollo 8 we can see that point was just after the second full day, and the speed was about 3578 km/hr.






share|improve this answer





















  • from your page: "At 2:50:37.79 GET (0141:37 AEST), the S-IVB stage burned for 5 minutes 17.7 seconds to boost the spacecraft’s velocity by 7,451.2 kilometres per hour, and Apollo 8 left Earth orbit and headed for the Moon at 38,959.4 kilometres per hour."
    – bitchaser
    3 hours ago










  • "Borman, Lovell and Anders were the first humans to leave the Earth’s gravity. They also never felt any physical change when the spacecraft slowed down to 3,578 kilometres per hour relative to Earth and crossed over into the Moon’s gravity field at 55:38:40 GET (0629:40 AEST). They were 326,415 kilometres from Earth and 62,598 kilometres from the Moon."
    – bitchaser
    3 hours ago



















2















I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating.




A pretty good analogy for TLI is throwing a baseball straight up into the air. The "throw" is the TLI burn; as soon as the ball leaves your hand it begins to slow down, trying to fall back towards Earth. The peak altitude of the "throw" is around where the moon will be three days later.




Did it start accelerating as it approached the Moon.




Yes, as noted in @PearsonArtPhoto's answer.




What was the rate of deceleration due to Earth's gravity?




The deceleration decreases the farther you get from Earth in an inverse-square relation:



$a=-{G M over r^2}$



Where $GM$ (aka $mu$) is the gravitational parameter of Earth (3.986e14) and $r$ is the distance from the center of Earth in meters. In LEO this is still 9.2 m/s2 or about 94% of Earth's surface gravity. By the time you're 3000 km up, though, it's only about 50% of surface gravity.



You can compare the results of the equations for the "downward"-pulling Earth component and the "upward"-pointing moon component, with the appropriate distances and gravitational parameters for the two bodies, to see what the crossover point is. Or use algebra if you're into that.






share|improve this answer





















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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    3














    Yes, in fact it did slow down with time, until it approached close enough that the Moon pulled it faster. That happened at a point very close to the Moon. In a diagram on this page, for Apollo 8 we can see that point was just after the second full day, and the speed was about 3578 km/hr.






    share|improve this answer





















    • from your page: "At 2:50:37.79 GET (0141:37 AEST), the S-IVB stage burned for 5 minutes 17.7 seconds to boost the spacecraft’s velocity by 7,451.2 kilometres per hour, and Apollo 8 left Earth orbit and headed for the Moon at 38,959.4 kilometres per hour."
      – bitchaser
      3 hours ago










    • "Borman, Lovell and Anders were the first humans to leave the Earth’s gravity. They also never felt any physical change when the spacecraft slowed down to 3,578 kilometres per hour relative to Earth and crossed over into the Moon’s gravity field at 55:38:40 GET (0629:40 AEST). They were 326,415 kilometres from Earth and 62,598 kilometres from the Moon."
      – bitchaser
      3 hours ago
















    3














    Yes, in fact it did slow down with time, until it approached close enough that the Moon pulled it faster. That happened at a point very close to the Moon. In a diagram on this page, for Apollo 8 we can see that point was just after the second full day, and the speed was about 3578 km/hr.






    share|improve this answer





















    • from your page: "At 2:50:37.79 GET (0141:37 AEST), the S-IVB stage burned for 5 minutes 17.7 seconds to boost the spacecraft’s velocity by 7,451.2 kilometres per hour, and Apollo 8 left Earth orbit and headed for the Moon at 38,959.4 kilometres per hour."
      – bitchaser
      3 hours ago










    • "Borman, Lovell and Anders were the first humans to leave the Earth’s gravity. They also never felt any physical change when the spacecraft slowed down to 3,578 kilometres per hour relative to Earth and crossed over into the Moon’s gravity field at 55:38:40 GET (0629:40 AEST). They were 326,415 kilometres from Earth and 62,598 kilometres from the Moon."
      – bitchaser
      3 hours ago














    3












    3








    3






    Yes, in fact it did slow down with time, until it approached close enough that the Moon pulled it faster. That happened at a point very close to the Moon. In a diagram on this page, for Apollo 8 we can see that point was just after the second full day, and the speed was about 3578 km/hr.






    share|improve this answer












    Yes, in fact it did slow down with time, until it approached close enough that the Moon pulled it faster. That happened at a point very close to the Moon. In a diagram on this page, for Apollo 8 we can see that point was just after the second full day, and the speed was about 3578 km/hr.







    share|improve this answer












    share|improve this answer



    share|improve this answer










    answered 5 hours ago









    PearsonArtPhoto♦PearsonArtPhoto

    80.5k16230443




    80.5k16230443












    • from your page: "At 2:50:37.79 GET (0141:37 AEST), the S-IVB stage burned for 5 minutes 17.7 seconds to boost the spacecraft’s velocity by 7,451.2 kilometres per hour, and Apollo 8 left Earth orbit and headed for the Moon at 38,959.4 kilometres per hour."
      – bitchaser
      3 hours ago










    • "Borman, Lovell and Anders were the first humans to leave the Earth’s gravity. They also never felt any physical change when the spacecraft slowed down to 3,578 kilometres per hour relative to Earth and crossed over into the Moon’s gravity field at 55:38:40 GET (0629:40 AEST). They were 326,415 kilometres from Earth and 62,598 kilometres from the Moon."
      – bitchaser
      3 hours ago


















    • from your page: "At 2:50:37.79 GET (0141:37 AEST), the S-IVB stage burned for 5 minutes 17.7 seconds to boost the spacecraft’s velocity by 7,451.2 kilometres per hour, and Apollo 8 left Earth orbit and headed for the Moon at 38,959.4 kilometres per hour."
      – bitchaser
      3 hours ago










    • "Borman, Lovell and Anders were the first humans to leave the Earth’s gravity. They also never felt any physical change when the spacecraft slowed down to 3,578 kilometres per hour relative to Earth and crossed over into the Moon’s gravity field at 55:38:40 GET (0629:40 AEST). They were 326,415 kilometres from Earth and 62,598 kilometres from the Moon."
      – bitchaser
      3 hours ago
















    from your page: "At 2:50:37.79 GET (0141:37 AEST), the S-IVB stage burned for 5 minutes 17.7 seconds to boost the spacecraft’s velocity by 7,451.2 kilometres per hour, and Apollo 8 left Earth orbit and headed for the Moon at 38,959.4 kilometres per hour."
    – bitchaser
    3 hours ago




    from your page: "At 2:50:37.79 GET (0141:37 AEST), the S-IVB stage burned for 5 minutes 17.7 seconds to boost the spacecraft’s velocity by 7,451.2 kilometres per hour, and Apollo 8 left Earth orbit and headed for the Moon at 38,959.4 kilometres per hour."
    – bitchaser
    3 hours ago












    "Borman, Lovell and Anders were the first humans to leave the Earth’s gravity. They also never felt any physical change when the spacecraft slowed down to 3,578 kilometres per hour relative to Earth and crossed over into the Moon’s gravity field at 55:38:40 GET (0629:40 AEST). They were 326,415 kilometres from Earth and 62,598 kilometres from the Moon."
    – bitchaser
    3 hours ago




    "Borman, Lovell and Anders were the first humans to leave the Earth’s gravity. They also never felt any physical change when the spacecraft slowed down to 3,578 kilometres per hour relative to Earth and crossed over into the Moon’s gravity field at 55:38:40 GET (0629:40 AEST). They were 326,415 kilometres from Earth and 62,598 kilometres from the Moon."
    – bitchaser
    3 hours ago











    2















    I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating.




    A pretty good analogy for TLI is throwing a baseball straight up into the air. The "throw" is the TLI burn; as soon as the ball leaves your hand it begins to slow down, trying to fall back towards Earth. The peak altitude of the "throw" is around where the moon will be three days later.




    Did it start accelerating as it approached the Moon.




    Yes, as noted in @PearsonArtPhoto's answer.




    What was the rate of deceleration due to Earth's gravity?




    The deceleration decreases the farther you get from Earth in an inverse-square relation:



    $a=-{G M over r^2}$



    Where $GM$ (aka $mu$) is the gravitational parameter of Earth (3.986e14) and $r$ is the distance from the center of Earth in meters. In LEO this is still 9.2 m/s2 or about 94% of Earth's surface gravity. By the time you're 3000 km up, though, it's only about 50% of surface gravity.



    You can compare the results of the equations for the "downward"-pulling Earth component and the "upward"-pointing moon component, with the appropriate distances and gravitational parameters for the two bodies, to see what the crossover point is. Or use algebra if you're into that.






    share|improve this answer


























      2















      I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating.




      A pretty good analogy for TLI is throwing a baseball straight up into the air. The "throw" is the TLI burn; as soon as the ball leaves your hand it begins to slow down, trying to fall back towards Earth. The peak altitude of the "throw" is around where the moon will be three days later.




      Did it start accelerating as it approached the Moon.




      Yes, as noted in @PearsonArtPhoto's answer.




      What was the rate of deceleration due to Earth's gravity?




      The deceleration decreases the farther you get from Earth in an inverse-square relation:



      $a=-{G M over r^2}$



      Where $GM$ (aka $mu$) is the gravitational parameter of Earth (3.986e14) and $r$ is the distance from the center of Earth in meters. In LEO this is still 9.2 m/s2 or about 94% of Earth's surface gravity. By the time you're 3000 km up, though, it's only about 50% of surface gravity.



      You can compare the results of the equations for the "downward"-pulling Earth component and the "upward"-pointing moon component, with the appropriate distances and gravitational parameters for the two bodies, to see what the crossover point is. Or use algebra if you're into that.






      share|improve this answer
























        2












        2








        2







        I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating.




        A pretty good analogy for TLI is throwing a baseball straight up into the air. The "throw" is the TLI burn; as soon as the ball leaves your hand it begins to slow down, trying to fall back towards Earth. The peak altitude of the "throw" is around where the moon will be three days later.




        Did it start accelerating as it approached the Moon.




        Yes, as noted in @PearsonArtPhoto's answer.




        What was the rate of deceleration due to Earth's gravity?




        The deceleration decreases the farther you get from Earth in an inverse-square relation:



        $a=-{G M over r^2}$



        Where $GM$ (aka $mu$) is the gravitational parameter of Earth (3.986e14) and $r$ is the distance from the center of Earth in meters. In LEO this is still 9.2 m/s2 or about 94% of Earth's surface gravity. By the time you're 3000 km up, though, it's only about 50% of surface gravity.



        You can compare the results of the equations for the "downward"-pulling Earth component and the "upward"-pointing moon component, with the appropriate distances and gravitational parameters for the two bodies, to see what the crossover point is. Or use algebra if you're into that.






        share|improve this answer













        I assume Apollo's velocity slowed down after it left Earth orbit, for how long was it decelerating.




        A pretty good analogy for TLI is throwing a baseball straight up into the air. The "throw" is the TLI burn; as soon as the ball leaves your hand it begins to slow down, trying to fall back towards Earth. The peak altitude of the "throw" is around where the moon will be three days later.




        Did it start accelerating as it approached the Moon.




        Yes, as noted in @PearsonArtPhoto's answer.




        What was the rate of deceleration due to Earth's gravity?




        The deceleration decreases the farther you get from Earth in an inverse-square relation:



        $a=-{G M over r^2}$



        Where $GM$ (aka $mu$) is the gravitational parameter of Earth (3.986e14) and $r$ is the distance from the center of Earth in meters. In LEO this is still 9.2 m/s2 or about 94% of Earth's surface gravity. By the time you're 3000 km up, though, it's only about 50% of surface gravity.



        You can compare the results of the equations for the "downward"-pulling Earth component and the "upward"-pointing moon component, with the appropriate distances and gravitational parameters for the two bodies, to see what the crossover point is. Or use algebra if you're into that.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered 4 hours ago









        Russell BorogoveRussell Borogove

        83.4k2281361




        83.4k2281361






























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