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

[Loren Pechtel]

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.)

 

[repoman]

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?

 

[Loren Pechtel]

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.

 

[DBT]

There are also very large objects floating around in interstellar space, asteroids, planets...while a collision is not very likely, it is possible.

 

[SLD]

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.

 

[repoman]

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.

 

[Bronzeage]

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.

 

[Loren Pechtel]

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.

 

[Loren Pechtel]

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.)

 

[SLD]

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.

 

[Jimmy Higgins]

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.

Sounds like a waste. It'd be better to harness that energy and either use it for propulsion or keep the batteries charged. Granted, the math starts really getting funky with these hypotheticals.

SOL just doesn't seem unlikely. Yes, the same was said of trains. Photons can do it, nearly anything with any kind of mass can't. The speed of light is based on just how much resistance in spacetime there is to transmitting an electric and magnetic force. Once you add mass, there is just so much more resistance.

Faster than light even less likely. I suppose the question might be, if you can make a ship technically go faster than light... how can you get anything on the ship to work? Can anything exist in a spacetime bubble? The subatomic elements that make up everything are tethered to what exactly? Then there is the issue of electrical and magnetic fields. How do they transmit without spacetime?

 

[Loren Pechtel]

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.

Sounds like a waste. It'd be better to harness that energy and either use it for propulsion or keep the batteries charged. Granted, the math starts really getting funky with these hypotheticals.

You can only harness energy differentials, not energy per se. And in this case you've got a big problem getting rid of the energy in the first place, attempting to capture some of it will make it even harder to keep your ship from melting.

SOL just doesn't seem unlikely. Yes, the same was said of trains. Photons can do it, nearly anything with any kind of mass can't. The speed of light is based on just how much resistance in spacetime there is to transmitting an electric and magnetic force. Once you add mass, there is just so much more resistance.

Getting small craft to relativistic velocity is certainly within human capability. Surviving in that realm is a lot more problematic.

Faster than light even less likely. I suppose the question might be, if you can make a ship technically go faster than light... how can you get anything on the ship to work? Can anything exist in a spacetime bubble? The subatomic elements that make up everything are tethered to what exactly? Then there is the issue of electrical and magnetic fields. How do they transmit without spacetime?

Einstein clearly says you can't push a craft to FTL velocity and that's a wall that will probably stand forever. What Einstein doesn't say is that there isn't some way to avoid the wall. You won't be FTL in whatever realm you're in even if the result is you beat light to some destination in our realm.

 

[skepticalbip]

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.

There would be zero velocity of the ship with respect to the space-time within the Alcubierre bubble along with the ship but there certainly would be a significant velocity of the ship with respect to Earth. That was sorta the idea of the drive.

 

[DBT]

Seems too good to be true. Most likely some price to pay, impossible energy requirements, etc

 

[Jokodo]

Seems too good to be true. Most likely some price to pay, impossible energy requirements, etc

One calculation suggests that the energy equivalent of one Jupiter should suffice for a small jump. All you need to do is find a Jupiter sized planet made entirely of antimatter, steer it onto a collision course with regular Jupiter, and harness at least 50% of the energy generated in the bang that ensues. That's a rather solvable engineering problem though.

Compared to the *other* problem, that sounds entirely plausible: the bigger problem is shielding the earth (or indeed any place within light years) from the waste heat, the excess energy you fail to harness. Even under unrealistic efficiencies, you're effectively left with a supernova in our backyard.

 

[Jimmy Higgins]

Sounds like a waste. It'd be better to harness that energy and either use it for propulsion or keep the batteries charged. Granted, the math starts really getting funky with these hypotheticals.

You can only harness energy differentials, not energy per se. And in this case you've got a big problem getting rid of the energy in the first place, attempting to capture some of it will make it even harder to keep your ship from melting.

We are talking about a ship going a large fraction the speed of light. Clearly technology is going to be present that can manage things better. And if we are getting such high velocities, we must be doing well with not losing energy in processes. One should never waste energy, and if something in coming and impacting, that can provide an opportunity to harness it. Not saying it is easy, but SOL isn't exactly easy either.

SOL just doesn't seem unlikely. Yes, the same was said of trains. Photons can do it, nearly anything with any kind of mass can't. The speed of light is based on just how much resistance in spacetime there is to transmitting an electric and magnetic force. Once you add mass, there is just so much more resistance.

Getting small craft to relativistic velocity is certainly within human capability. Surviving in that realm is a lot more problematic.

I said SOL, not less than SOL.

Faster than light even less likely. I suppose the question might be, if you can make a ship technically go faster than light... how can you get anything on the ship to work? Can anything exist in a spacetime bubble? The subatomic elements that make up everything are tethered to what exactly? Then there is the issue of electrical and magnetic fields. How do they transmit without spacetime?

Einstein clearly says you can't push a craft to FTL velocity and that's a wall that will probably stand forever. What Einstein doesn't say is that there isn't some way to avoid the wall. You won't be FTL in whatever realm you're in even if the result is you beat light to some destination in our realm.

And I'm asking what the realm is. Can light even exist in such a realm.

 

[Gun Nut]

For sure, they should make speeder bikes.

party fail. wrong genre.

 

[Gun Nut]

This shit again?
It's not only not feasible it's flat out impossible.

It's impossible to reach the moon, even, never mind traveling that fast.

There are only 1.1 Trillion tons of coal on Earth.

It would take over 1,000 times more coal than exists to power a steam engine with sufficient energy to escape earth and subsequently enter a lunar orbit. Therefore, at one time in human history, such an inconceivable task as reaching the moon was mathematically impossible.

 

[skepticalbip]

This shit again?
It's not only not feasible it's flat out impossible.

It's impossible to reach the moon, even, never mind traveling that fast.

There are only 1.1 Trillion tons of coal on Earth.

It would take over 1,000 times more coal than exists to power a steam engine with sufficient energy to escape earth and subsequently enter a lunar orbit. Therefore, at one time in human history, such an inconceivable task as reaching the moon was mathematically impossible.

You are using the wrong meaning of "impossible". Some things are impossible assuming current technology. Some things are impossible because it would violate the laws of physics.

And then there is the case where some people claim an impossibility because of their ignorance. For example: the newspaper editor that claimed it was impossible for rockets to work in space because the thrust wouldn't have any air to push against... and this was at the time early rocket engineers were doing just fine with their work.

 

[Gun Nut]

This shit again?
It's not only not feasible it's flat out impossible.

It's impossible to reach the moon, even, never mind traveling that fast.

There are only 1.1 Trillion tons of coal on Earth.

It would take over 1,000 times more coal than exists to power a steam engine with sufficient energy to escape earth and subsequently enter a lunar orbit. Therefore, at one time in human history, such an inconceivable task as reaching the moon was mathematically impossible.

You are using the wrong meaning of "impossible". Some things are impossible assuming current technology. Some things are impossible because it would violate the laws of physics.

And then there is the case where some people claim an impossibility because of their ignorance. For example: the newspaper editor that claimed it was impossible for rockets to work in space because the thrust wouldn't have any air to push against... and this was at the time early rocket engineers were doing just fine with their work.

The idea that a steam engine is the best possible way to convert energy (it was at one point) is the end-all barrier to advancement is the same as saying that "pushing mass through space is limited therefore getting somewhere faster than X is IMPOSSIBLE".

Obviously, a solution might be getting somewhere faster WITHOUT "pushing it through space" (like a neanderthal).
You did help make my point, though. Thank you. minor and probably temporary lack of imagination.
Note this "warp drive" does not move mass faster than light. It moves space faster than light and the "ship" stands motionless as the space itself moves. Or something like that.