Page 1 of 4 123 ... LastLast
Results 1 to 30 of 119

Thread: shooting something into the sun

  1. #1
    Join Date
    Jun 2003
    Posts
    1,073

    shooting something into the sun

    I vaguely remember reading a thread here where it was stated that it is extremely difficult to get something from here to the sun; something to do with having to cancel out the centrifical force of the Earth along with the terminal velocity of the earth. Is this true? If it is, how did we get probes to inner planets like Venus and Mercury? And if it is possible to get something to the sun, how would it be done?

    Thanks.

  2. #2
    Join Date
    Jan 2005
    Posts
    2,930
    The difficulty of launching something into the Sun is twofold:

    1.) Escape from Earth's gravity.
    2.) Cancelling the Earth's angular momentum, such that a direct "dive" into the Sun is possible.

    IIRC, there is no booster in existence that could do this for even a "regular-sized" space probe. Getting to Venus though, is much easier; as for Mercury, we use gravity assists to slow probes down without using precious fuel (and hence, without adding launch mass).

    I think the easiest way to get a significant payload into the Sun was discussed some time ago with a proposed Solar Probe; launch the payload *outward* to Jupiter, and then use its massive gravity to slingshot it back into a collision course with the Sun.

  3. #3
    Join Date
    Mar 2004
    Posts
    15,470
    Quote Originally Posted by Kebsis View Post
    If it is, how did we get probes to inner planets like Venus and Mercury?
    To Mercury, with great effort.

    Look at the Messenger mission flight plan, for instance. On its way to Mercury orbit, it performs one Earth flyby, two Venus flybys, and 3 Mercury flybys, over 6-1/2 years, before approaching Mercury for an orbit insertion.
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
    No ATM forum is better than our ATM forum.

  4. #4
    Join Date
    Jun 2003
    Location
    SE Michigan
    Posts
    3,043
    Romanus is correct. The Messenger probe to Mercury is making several fly-bys: Earth, Venus twice, and Mercury thrice in order to slow down enough for its engines to put it into Mercury orbit.

    As for the Jupiter fly-by to send stuff to the sun, this is exactly what Ulysses did to change its orbit so as to observe the north and south poles of the sun. I don't know if the technique could be used to make the orbit intersect the sun, but I bet it could be done.

    Fred
    Hey, you! "It's" with an apostrophe means "it is" or "it has." "Its" without an apostrophe means "belongs to it."

    "For shame, gentlemen, pack your evidence a little better against another time."
    -- John Dryden, "The Vindication of The Duke of Guise" 1684

    Earth's sole legacy will be a very slight increase (0.01%) of the solar metallicity.

  5. #5
    Join Date
    Jun 2006
    Posts
    7,157
    I thought I should be able to work out the delta V to launch something into the sun with a little effort. Unfortunately a little effort was too much for me.

  6. #6
    Join Date
    Jul 2005
    Location
    Longmont, CO
    Posts
    3,490
    It's actually quite simple, for a straight in trajectory. You simply cancel all of the earth's orbital velocity, 29.8 km/s, and it will fall right in. That's quite a bit of velocity to cancel though. IIRC, it takes less delta v to eject it completely from the system.

  7. #7
    Join Date
    Jun 2006
    Posts
    7,157
    It's actually quite simple, for a straight in trajectory. You simply cancel all of the earth's orbital velocity, 29.8 km/s, and it will fall right in. That's quite a bit of velocity to cancel though. IIRC, it takes less delta v to eject it completely from the system.
    I thought it might be that simple, but I didn't want to say because people think someone who says nothing is smarter than someone who says something and gets it wrong, despite the fact that a person who often makes mistakes is a person who often has opportunities to learn. (Or perhaps just an idiot.)

  8. #8
    Join Date
    Jul 2005
    Location
    Longmont, CO
    Posts
    3,490
    You could definitely do it with less delta v through various trajectories, but that is the most direct way. Now, calculating the minimum delta v path is more complicated...

  9. #9
    Join Date
    Oct 2002
    Posts
    3,841
    If you cancel ANY of the Earth's orbital velocity, why won't the probe spiral in, eventually?
    John

  10. #10
    Join Date
    Sep 2006
    Posts
    1,707
    Quote Originally Posted by JohnD View Post
    If you cancel ANY of the Earth's orbital velocity, why won't the probe spiral in, eventually?
    John
    Conservation of angular momentum. You could look it up.

  11. #11
    Join Date
    Jul 2005
    Posts
    13,953
    Quote Originally Posted by JohnD View Post
    If you cancel ANY of the Earth's orbital velocity, why won't the probe spiral in, eventually?
    Cancel a small amount of orbital velocity, and the spacecraft will fall towards the sun, pick up speed, and come back out to the original distance. Then the cycle repeats: it just enters an elliptical orbit.

    Grant Hutchison

  12. #12
    Join Date
    Oct 2006
    Posts
    3,672
    If cancelling a fraction of the speed causes a more-elliptical orbit that still extends at least as far out as the original less-elliptical one did, then how would you create an equally, or less, elliptical orbit at a shorter distance from the sun, one that does not extend out to the original orbit's distance? (This is what I would have expected to happen, but now it sounds like you're saying this would require a second "burn" after the initial decrease in distance, or perhaps a long continuation of the first "burn" to counter the slingshot acceleration you mentioned.)

  13. #13
    Join Date
    Jul 2005
    Location
    Longmont, CO
    Posts
    3,490
    You would do a short burn to get it into the elliptical orbit. Then, when it was at the perigee (closest point to the sun), you would do another burn to slow it down again. This would circularize the orbit closer to the sun than it started.

  14. #14
    Join Date
    Jan 2007
    Posts
    543
    it must be an easy task, as the atomic industry has ( I remember well ) promised to dump all their mess in the sun one day

  15. #15
    Join Date
    Sep 2006
    Posts
    1,707
    Quote Originally Posted by satori View Post
    it must be an easy task, as the atomic industry has ( I remember well ) promised to dump all their mess in the sun one day
    I disbelieve you. Could you please provide a reference for this claim?

    It is _not_ an easy task. I just gave my physics students a homework question which involves the amount of fuel required to launch 1 kg of material into the Sun ... and it's not a small number.

  16. #16
    Join Date
    Jul 2005
    Location
    Longmont, CO
    Posts
    3,490
    Quote Originally Posted by satori View Post
    it must be an easy task, as the atomic industry has ( I remember well ) promised to dump all their mess in the sun one day

    1) It is absolutely not an easy task
    2) References? There are about a million easier ways to dispose of nuclear waste.

  17. #17
    Join Date
    Jan 2007
    Posts
    543
    I just wanted to discredit the atomic industry !

    You are of course perfectly right cjl with your pointing to our orbital velocity of 30km/sec. Add another 10km/sec (?) or so to get rid of Earth's gravitational embrace and you schould have quite a good estimation of the amount of energy you would need to reach Sun.

    ( yes i begin to realize, in this artifical posting world you must use explicite means to mark irony as what it was meant for. sorry my fault ! )
    -------------------------------------------
    all will end in tears....I just know it

  18. #18
    Join Date
    Jan 2007
    Posts
    543
    cjl,
    "There are about a million easier ways to dispose of nuclear waste.".....But is there one Good one ?!

    We will live to see the day, when the enemy will dispose of atomic waste in a dirty bomb kind of fashion. That will be the day, when those stupid Sun-disposal-plans will finaly have their day after all and they will set up Huge rocket factories all over...

  19. #19
    Join Date
    Feb 2005
    Location
    Boulder, Colorado
    Posts
    6,269
    Quote Originally Posted by cjl View Post
    It's actually quite simple, for a straight in trajectory. You simply cancel all of the earth's orbital velocity, 29.8 km/s, and it will fall right in. That's quite a bit of velocity to cancel though. IIRC, it takes less delta v to eject it completely from the system.

    that is fast, only 2.5x faster that we can go now. but we could manage it maybe if we weren't trying to have it drop straight down onto the sun. Have it do a flyby of venus during a time of good alignment, and with good calculations it will go directly into the sun.
    My travel blog Mostly about riding a motorcycle across the US and Europe. Also has cool things that happen in between.

  20. #20
    Join Date
    Dec 2004
    Location
    UK
    Posts
    7,520
    Quote Originally Posted by satori View Post
    cjl,
    "There are about a million easier ways to dispose of nuclear waste.".....But is there one Good one ?!
    well, you can put it on the bus Gus,
    Put it on the plane Elaine...............
    .................
    ................

  21. #21
    Join Date
    Jul 2006
    Posts
    11,135
    *WARNING LAYMAN ABOUT TO ASK QUESTION*

    So all of you are saying that taking something like a Saturn V set up, leading the Sun a little bit, and firing at the right time won't send a payload the wieght of an Apollo mission to a fiery doom? I thought it was downhill from here to the Sun. Especially if you are just trying to hit it and not orbit it.
    Time wasted having fun is not time wasted - Lennon
    (John, not the other one.)

    "Hey buddy! My eyes are up here!" - Medusa

  22. #22
    Join Date
    Jan 2007
    Posts
    543
    i once climed at night on a balustrade and looked up.... after a while i got the strange feeling, that when i jumped now, i would fall among all those stars....that's about as wrong an impression of course as the one you harbour about us and the sun...

    cjl will certainly straight it out for you better than i could

  23. #23
    Join Date
    Jul 2005
    Posts
    13,953
    Quote Originally Posted by BigDon View Post
    So all of you are saying that taking something like a Saturn V set up, leading the Sun a little bit, and firing at the right time won't send a payload the wieght of an Apollo mission to a fiery doom?
    That's right.
    If you do that, you'll send your payload into an elliptical orbit. You essentially need to remove all of the Earth's speed around the sun to make your elliptical orbit fall far enough in to even graze the sun. And if it doesn't graze the sun, it'll just loop back up out of the sun's gravity-well under its own momentum.

    Think of sitting on a train, and trying to lob a tennis ball at a fencepost, as it whips past at 100mph. You just can't do it when you're level with the post, because the speed of the train carries your lob past the post.
    Ah-ha, you say, I just need to throw the ball before I'm level with the post, and let the speed of the train slam my ball into it sideways. Trouble is, when you're in a circular orbit, you're always level with the post.

    Grant Hutchison

  24. #24
    Join Date
    Feb 2005
    Location
    Boulder, Colorado
    Posts
    6,269
    Quote Originally Posted by grant hutchison View Post
    That's right.
    If you do that, you'll send your payload into an elliptical orbit. You essentially need to remove all of the Earth's speed around the sun to make your elliptical orbit fall far enough in to even graze the sun. And if it doesn't graze the sun, it'll just loop back up out of the sun's gravity-well under its own momentum.

    Think of sitting on a train, and trying to lob a tennis ball at a fencepost, as it whips past at 100mph. You just can't do it when you're level with the post, because the speed of the train carries your lob past the post.
    Ah-ha, you say, I just need to throw the ball before I'm level with the post, and let the speed of the train slam my ball into it sideways. Trouble is, when you're in a circular orbit, you're always level with the post.

    Grant Hutchison

    couldn't have said it better
    My travel blog Mostly about riding a motorcycle across the US and Europe. Also has cool things that happen in between.

  25. #25
    Join Date
    Jul 2006
    Posts
    11,135
    But...but..but.. I saw on TV where....




    Thanks guys, seems there's an education in every bowl of BAUT flakes.
    Time wasted having fun is not time wasted - Lennon
    (John, not the other one.)

    "Hey buddy! My eyes are up here!" - Medusa

  26. #26
    Join Date
    Oct 2006
    Posts
    3,672
    Quote Originally Posted by BigDon View Post
    I thought it was downhill from here to the Sun. Especially if you are just trying to hit it and not orbit it.
    It's downhill on a slope that's shaped like the inside of a bowl, where you're always moving so fast that your momentum tends to cause you to drift outward, which is uphill.
    Last edited by Delvo; 2007-Feb-19 at 05:51 PM.

  27. #27
    Join Date
    Oct 2001
    Posts
    8,774
    We discussed this issue a while back. The idea was to use a space elevator to dump nuclear waste into the Sun.

  28. #28
    Join Date
    Apr 2005
    Posts
    11,545
    Quote Originally Posted by grant hutchison View Post
    Think of sitting on a train, and trying to lob a tennis ball at a fencepost, as it whips past at 100mph. You just can't do it when you're level with the post, because the speed of the train carries your lob past the post.
    You could do it if you could throw it faster than 100mph. But that's your point, I know, not many people would be capable of doing that.

    It takes a lot of effort.

  29. #29
    Join Date
    Sep 2003
    Posts
    11,514
    Quote Originally Posted by grant hutchison View Post
    Trouble is, when you're in a circular orbit, you're always level with the post.
    For those on this side of the Atlantic, his "level" refers to being "even" with the post, or along side of it. Over here, "level" is associated with a horizontal grade normally, unless we stipulate otherwise.

    [Added: I assume the 100mph is not of a narrow-gage train. ]
    We know time flies, we just can't see its wings.

  30. #30
    Join Date
    Jul 2005
    Posts
    13,953
    Quote Originally Posted by hhEb09'1 View Post
    You could do it if you could throw it faster than 100mph. But that's your point, I know ...
    Exactly. The only way to do it is to stand a baseball pitcher on the caboose, and have him pitch almost straight backwards to effectively cancel the train's speed. Which is analogous to the fact that you have to largely cancel the Earth's orbital speed to drop something into the sun.

    Grant Hutchison

Similar Threads

  1. Help with shooting stars
    By mradam67 in forum Astrophotography
    Replies: 7
    Last Post: 2011-Nov-08, 01:45 AM
  2. Shooting the moon
    By phunk in forum Astrophotography
    Replies: 4
    Last Post: 2011-Jul-22, 08:01 AM
  3. How Big Was the shooting star I saw
    By wiggy in forum Space/Astronomy Questions and Answers
    Replies: 2
    Last Post: 2011-Jun-27, 10:00 AM
  4. shooting star
    By Star_Scream in forum Astronomy
    Replies: 5
    Last Post: 2006-Dec-14, 02:40 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •