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Thread: Faster-than-light travel: Is warp drive really possible?

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    Quote Originally Posted by DBT View Post
    With interstellar travel, it may not be a case of erosion. It may be a sudden and catastrophic collision with a clump of interstellar debris.
    The thing is the erosion problem is a certainty unless you develop something to counter it--which almost certainly requires technology far beyond our knowledge or else a truly humongous starship. (The energy being added is based on the cross section. If you make it long enough you can radiate away the heat.)

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    The cross sectional area seems to work against large objects speeding at huge velocities.

    Even for all the area that is NOT being bombarded, the area that is gets the heat from very few sections that are.

    However all of the volume inside is not getting hit, whereas if the same mass was put into a million projectiles there would be 100 times (N^1/3) more surface area.

    Hard to thing about this considering that this is in the near total vacuum of space compared to in the Earth's atmosphere.

    What about some sponge like material to be the shielding?

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    Quote Originally Posted by repoman View Post
    The cross sectional area seems to work against large objects speeding at huge velocities.

    Even for all the area that is NOT being bombarded, the area that is gets the heat from very few sections that are.

    However all of the volume inside is not getting hit, whereas if the same mass was put into a million projectiles there would be 100 times (N^1/3) more surface area.

    Hard to thing about this considering that this is in the near total vacuum of space compared to in the Earth's atmosphere.

    What about some sponge like material to be the shielding?
    A sponge won't make a difference--the problem is the energy being dumped from the collisions. There's no shockwave to deflect the energy like there is when a properly designed spacecraft plunges into atmosphere, it all shows up as heat in your radiation shield. To survive you are going to have to pump that heat away and radiate it to space faster than it's coming in.

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    Elder Contributor DBT's Avatar
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    There are also very large objects floating around in interstellar space, asteroids, planets...while a collision is not very likely, it is possible.

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    Objects hitting the spaceship aren’t relevant for an Alcubierre Drive. The spaceship doesn’t move. It warps spacetime around it. Any object in its way gets warped around it too.

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    Quote Originally Posted by Loren Pechtel View Post
    Quote Originally Posted by repoman View Post
    The cross sectional area seems to work against large objects speeding at huge velocities.

    Even for all the area that is NOT being bombarded, the area that is gets the heat from very few sections that are.

    However all of the volume inside is not getting hit, whereas if the same mass was put into a million projectiles there would be 100 times (N^1/3) more surface area.

    Hard to thing about this considering that this is in the near total vacuum of space compared to in the Earth's atmosphere.

    What about some sponge like material to be the shielding?
    A sponge won't make a difference--the problem is the energy being dumped from the collisions. There's no shockwave to deflect the energy like there is when a properly designed spacecraft plunges into atmosphere, it all shows up as heat in your radiation shield. To survive you are going to have to pump that heat away and radiate it to space faster than it's coming in.
    But a sponge can spread out thermal energy with radiation very easily and keep most of the surrounding volume at low temperature.

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    Do any of these fantasydrives address to problem of time distortion?

    I imagine most SOL or NSOL travels are expected to be one way trips. The alternative is to return from a 4 year spaceflight and find your children are older than you.

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    Quote Originally Posted by repoman View Post
    Quote Originally Posted by Loren Pechtel View Post
    Quote Originally Posted by repoman View Post
    The cross sectional area seems to work against large objects speeding at huge velocities.

    Even for all the area that is NOT being bombarded, the area that is gets the heat from very few sections that are.

    However all of the volume inside is not getting hit, whereas if the same mass was put into a million projectiles there would be 100 times (N^1/3) more surface area.

    Hard to thing about this considering that this is in the near total vacuum of space compared to in the Earth's atmosphere.

    What about some sponge like material to be the shielding?
    A sponge won't make a difference--the problem is the energy being dumped from the collisions. There's no shockwave to deflect the energy like there is when a properly designed spacecraft plunges into atmosphere, it all shows up as heat in your radiation shield. To survive you are going to have to pump that heat away and radiate it to space faster than it's coming in.
    But a sponge can spread out thermal energy with radiation very easily and keep most of the surrounding volume at low temperature.
    What's the point in spreading it out? You still have the same number of joules per gram whether it's spread out or not and a sponge radiates heat away no better than a solid.

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    Quote Originally Posted by Bronzeage View Post
    Do any of these fantasydrives address to problem of time distortion?

    I imagine most SOL or NSOL travels are expected to be one way trips. The alternative is to return from a 4 year spaceflight and find your children are older than you.
    Yes, but they introduce a different time problem--any simple FTL drive allows you to travel into your own past. I have seen many arguments that this is inevitable, but that is only true if Einstein has the last word (and if a FTL drive exists he doesn't!) If you're free to enter the FTL state in a reference frame of your choice (note that stationary relative to the star you're near is a frame of your choice because you can choose the star) then time travel is possible. Under Einsteinian math you can choose your reference frame--but I do not believe that precludes a forced reference frame involved in entering/leaving the FTL state as relativity doesn't address that at all. This could either be requiring velocity matching (which could be a big problem as it might require relativistic velocities!) or that the velocity you have is irrelevant, you're operating under different rules while FTL. (Your velocity in our universe might have nothing to do with your velocity in a hyperspace universe.)

    Note that this does not apply to jump drives, however. (Anything along the lines of you proceed to point A, push the button and instantly are at point B. Whether A and B need to be special points or not doesn't matter.)

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    Quote Originally Posted by Bronzeage View Post
    Do any of these fantasydrives address to problem of time distortion?

    I imagine most SOL or NSOL travels are expected to be one way trips. The alternative is to return from a 4 year spaceflight and find your children are older than you.
    In an Alcubierre drive you don’t move, thus your clock stays the same as earth’s clock.

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