What will happen if a FTL ship hits Earth?

[Aghanim]

I'm starting a new thread instead of continuing talking in The Space Lounge thread, because I want to refine the question and this could go long...

What will happen if FTL, I repeat FTL drive, specifically Alcubierre /warp drive, hits Earth? No, I'm not asking about 99.999999999999999999999999999999% c STL ship, I'm asking about 10 c or something like that. Alcubierre drive is real space drive instead of hyperspace drive, so probably the ship still carries a lot of kinetic energy while in warp space

Will every warp capable vessel becomes a doomsday weapon?

[Psycix]

The warp bubble will probably collapse in the presence of mass, so it will break out of warp as soon as it hits the thinnest parts of our atmosphere.

Note that the ship doesn't actually carry the kinetic energy to go that fast, it simply takes a shortcut while traveling at newtonian speeds. (My assumption, feel free to disagree.)

The main question that remains is how much energy is contained in the warp bubble, or ship fuel. Even standing still it is likely / possible that the ship is extremely energetic upon destructive reentry, consisting out of antimatter for a large fraction of its mass.

Edited January 12, 2014 by Psycix

[Albert VDS]

A ship with an Alcubierre drive doesn't actually go FTL, the warping of space actually moves everything around the bubble past the ship.

Your question should actually be what would happen if we would warp the space occupied by the Earth.

If the ship would actually go as fast as light then it would be an infinite mass slamming into a finite mass. Guess who wins?

[Themohawkninja]

Well, F=MA, and at 10c, you are getting into some very, very high mass ranges (Possibly not infinity, but high enough).

So, you would probably either destroy the Earth completely, or put a nice-sized crater somewhere on it. That being said, the instant the FTL ship hits the atmosphere, it may explode before reaching the ground, causing super-heated and ionized air to slam downwards and outwards from the point of explosion, destroying everything in it's path like an airburst nuclear device.

[Skyler4856]

An Alcubierre drive doesn't move the ship, Technically. The alcubierre drive moves the space around a ship.

[sal_vager]

So the warp bubble hits Earth, what damage could that conceivably cause?

[Tex_NL]

...

If the ship would actually go as fast as light then it would be an infinite mass slamming into a finite mass. Guess who wins?

My bet is on infinity. Because that's where you'll be spending the rest of your time.

[K^2]

So the warp bubble hits Earth, what damage could that conceivably cause?

Hot knife, meet butter. What I don't know is how long the bubble will last before collapsing. Original Alcubierre Drive will punch through and through, but that's just because the amount of energy that goes into one makes even the mass of entire Earth completely negligible. Something a bit more realistic would collapse early on, perhaps even in atmosphere, but that would probably just result in a massive explosion.

So depending on how plausible a warp drive is going to be, the effect can range from large nuke to total destruction of the planet.

[Scotius]

Don't forget about blast of Hawking radiation released from the collapsing bubble. I have no idea how much energy will be emitted (does it depend on how long ship has spent in FTL?), but i doubt it would be healthy to be in its range.

[MBobrik]

Mass enters warp bubble, warp bubble destabilizes, collapses and releases all its energy in the form of hawking radiation and gravity waves. Given that any practical Alcubierre drive will contain only microscopic amounts of (exotic) matter, the bang won't be any big - perhaps only in the ton or lower kiloton range. Enough to blast the ship into a cloud of plasma and fry any satellite nearby as the amounts of ordinary matter needed to destabilize a warp bubble will be minuscule too - it will most probably happen in the van allen belts or at LEO heights.

[Whirligig Girl]

in my SF story, this happened to a starship. The the craft comes towards the moon, but because it warps space, the outside world had no effect. It sort of slips through a bit of space that's a planck length thick, but the inside of the slit is bigger, the size of the starship.

[K^2]

perhaps only in the ton or lower kiloton range. Enough to blast the ship into a cloud of plasma and fry any satellite nearby as the amounts of ordinary matter needed to destabilize a warp bubble will be minuscule too - it will most probably happen in the van allen belts or at LEO heights.

If it's that unstable, the whole thing is useless. Even though practical warp drive would have to dramatically reduce the amount of negative energy required, it's not going to be anywhere near that low. I agree that anything we could build with resources we can get in foreseeable future won't survive through the atmosphere, but it has to be capable of withstanding particle radiation in Earth's orbit or it's too unreliable to ever be used. This requirement puts you in MT ranges easily.

[lajoswinkler]

With around 10 molecules per cm^3 in interplanetary space (not accounting for the solar wind particles), the thing would obviously be useless. Even in the highest vacuum in space, there's at least one molecule per m^3.

[TheDarkStar]

Also, wasn't there an article a while ago that showed that an Alcubierre drive might collect everything that it passes through until it stops, and then release it all at once in a fireball?

[Kerbin Dallas Multipass]

You might find this an interesting and entertaining read http://what-if.xkcd.com/20/

[MBobrik]

If it's that unstable, the whole thing is useless. Even though practical warp drive would have to dramatically reduce the amount of negative energy required, it's not going to be anywhere near that low. I agree that anything we could build with resources we can get in foreseeable future won't survive through the atmosphere, but it has to be capable of withstanding particle radiation in Earth's orbit or it's too unreliable to ever be used. This requirement puts you in MT ranges easily.

I don't think so. Because of safety concerns it would have to launch from outside planet's magnetic field anyway, and to minimize cost it would use the bare minimum of what is required to maintain stable bubble moving through interplanetary medium. ( meaning it would be OK flying between planets, but would likely not withstand even the tenuous atmosphere found at LEO heights ). However, I am sure that if someone manages to build FTL drives, there will be specialized military versions that can withstand much more, making it perhaps few dozen kilometers into the atmosphere before exploding, and and then releasing proportionally more energy.

[K^2]

Also, wasn't there an article a while ago that showed that an Alcubierre drive might collect everything that it passes through until it stops, and then release it all at once in a fireball?

I don't see any reason why it would do so. If you can dig up that article, I'd like to take a look at it.

[xmaslightguy]

In my mind, an Alcubierre drive is based on condensing space-time in front of the craft, and releasing it behind to create a wave the ship can ride. I'd say the result of this bubble hitting earth would be people in the path of the ship would see it entering the atmosphere in slow-motion, go to regular speed as they enter its sphere of influence, and then go superspeed on impact as the back of the bubble reaches ground level. To anyone outside of this bubble, they would just observe the spaceship going through the atmosphere at whatever speeds it was traveling (relative to Earth) when it started using the Alcubierre drive.

[andrewas]

I don't see any reason why it would do so. If you can dig up that article, I'd like to take a look at it.

I think this is the one:

http://www.universetoday.com/93882/warp-drives-may-come-with-a-killer-downside/

[thunderstar]

well, f=ma, and at 10c, you are getting into some very, very high mass ranges (possibly not infinity, but high enough).

So, you would probably either destroy the earth completely, or put a nice-sized crater somewhere on it. That being said, the instant the ftl ship hits the atmosphere, it may explode before reaching the ground, causing super-heated and ionized air to slam downwards and outwards from the point of explosion, destroying everything in it's path like an airburst nuclear device.

i don't know why but i don't feel safe anymore D:

[WestAir]

What happens if we're hit by a fist-sized ball of iron going at similar velocities to the Oh-My-God-Particle?

[Themohawkninja]

What happens if we're hit by a fist-sized ball of iron going at similar velocities to the Oh-My-God-Particle?

Well... you get a fist size ball of iron with near infinite mass and energy hitting the Earth... just what that does to Earth is hard to say, since I don't know how deep it would go into the Earth before stopping.

[Seret]

I don't see any reason why it would do so. If you can dig up that article, I'd like to take a look at it.

The paper it's based on is here.

[Kilmeister]

Interesting aspect to the Alcubierre drive I never thought about. I guess it makes sense that SOMETHING has to happen to all the matter you will end up passing through on a voyage of a massive distance.

[K^2]

The paper it's based on is here.

I only see problems with particles encountered during bubble acceleration and deceleration. During most of the voyage, particles pass right through without change in energy, according to this paper.