# Alcubierre Drive - A thought excercise.

Discussion in 'Science and Technology' started by sojourner, Jul 28, 2013.

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Basing this on the supposition that we make a working Alcubierre drive that doesn't get everyone killed automatically, we still have a problem. Let me prestate first that to my understanding the Alcubierre drive does not impart any inertia or remove any on it's own. It merely warps space to move the craft.

So. we board our hypothetical ship and point it at say - Epsilon Eridani - and away we go. Upon arriving at the star system I see 1 of 3 outcomes.

1. we get left behind as the star speeds away on it's orbit around the galactic center
2. we start falling into the star at incredible speeds due to lack of sufficient velocity for orbit.
3. we get sling-shotted around the star and back out of the system at high velocity.

What does this mean? We will need an incredibly powerful "real space" drive to give us the needed velocity vectors to actually stay in system at our destination. Something we don't currently have. So unless I am missing something, even if we built an Alcubierre driven ship tomorrow, without a real space drive to accompany it we'll still be stuck to this solar system.

Or am I totally missing something? I'm no scientist. Just an armchair space geek.

ETA: Doh, and totally forgot to spell check the thread title.

2. ### StarCruiserCaptainCaptain

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True - but one would assume that if we have found the technology and engineering needed to create an FTL drive of such power, we can probably build a fairly potent real space drive as well. It may be something like a Inertial Confinement Fusion drive (~10% c, in theory).

3. ### LindleyModerator with a SoulModerator

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The trick would be lining up the starting velocity vector within our system so that it lines up correctly on exit as well. That would minimize the delta-V required.

4. ### JustAFriendCommodoreCommodore

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Even pilots here on Earth need to do navigation and course correction (for things like headwinds, tailwinds and crosswinds and magnetic flucuations messing with instruments).

If you've got the tech to do FTL travel, you'd likely have the tech to navigate, too....

5. ### PsionCommodoreCommodore

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I assume, but I might be mistaken, that most of the stars in the Sun's vicinity share similar orbits and therefore a lot of adjustment isn't necessary for point one.

Points two and three are kind of fun. If you "drop out of warp" far enough away from the star, a drive system like VASIMR or even ion thrusters should be enough to nudge into the proper orbit before you fall into the star or get flung back out to interstellar space. And the process of falling towards the star helps conserve fuel as you maneuver towards habitable planets.

Failing that, a good old NERVA engine should do the trick in an emergency.

Warp drive ... it's trickier than you think.

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I have the same question, but about a more realistic problem. Andromeda is coming. How do we:
1. Maintain presence in the Milky Way if all our star systems get ejected?
2. Colonize Andromeda by sending a one-way mission to it?

The Delta-V for galaxies surely must be insane. How do we do that?

ETA: Two days acceleration at 1 m/s² ought to be enough to put you in either galaxy, it's barely 20 times ISS orbital speed, I don't think Epsilon Eridani would be much more of a problem. I would assume firing a large five-stage array of good old chemical engines for a few hours to a day or two would solve both problems.

Last edited: Jul 29, 2013

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^You didn't read the exercise carefully did you?

Regardless, while you may be able to match velocity vectors with the Andromeda galaxy as a whole, you still have to match vectors with a target star in that galaxy and then a planet within that star system. How big a rocket are you up to now?

And hey, it was merely a thought exercise. I never said it was "realistic".

Last edited: Jul 29, 2013

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The energy needed for the Alcubierre drive is a lot, even with the recent "revisions". Could this not also be used for a drive with more traditional thrust?

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And so I can share my similar thought exercise, can't I?

I've long thought we'd be facing this problem with Andromeda, and while we'd have no problem firing a spacecraft into the galaxy (per my rough calculations), we'd have to send quite more than a single spacecraft that will end up be alone and helpless in an empty galaxy. We'd have to accelerate quite a big chunk of a mass to start a colony that could survive and spread with guarantees.

Thankfully, we'd have plenty of time to prepare and do it, but that will hardly solve all the complications (other star systems should be fairly easier, and regular trips can be of fairly small mass).

Which is why I added "to a day or two" to account for delta-V expenses I could be missing at first glance, but matching the star's vector will be not more than twice the price of matching the other galaxy, and matching a planet in the system is cheap. I think the delta-V budget is less than the star's escape velocity budget (I could be wrong), and we've got four spacecrafts flying at escape velocity presently. I still think that you can do it with something as simple as a regular five-stage rocket.

Wasn't it a bit more than the total amount of energy in the universe or something? It ought to be enough for anybody.

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^A NASA scientist has come up with a revision that reduces the amount of energy required from "insane" to something less than "improbable".

11. ### PsionCommodoreCommodore

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I rather like this thought exercise. It suggests a number of things that might make simulating Star Trek ship maneuvers a little more realistic.

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Doesn't the warping of space automatically get rid of the problem of inertia? You pull a star system towards your own, and when you transition between A and B, you transition from one reference system to the other. You just MUST be able to equate both inertial systems, otherwise you can't create the warp, can you?

Not necessarily. We have the tech to make cars go as fast as 400 km/h. But you are not able to navigate at that speed in a city.

No, because the whole point of the Alcubierre drive is to get around the problem of relativistic speeds.

13. ### LindleyModerator with a SoulModerator

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Speedy thing goes in, speedy thing comes out.

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Alcubierre Drive? Never heard of it. Sounds like a street in Beverly Hills.

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A ship at the center of the warp bubble is in flat space so there are no problems with the changing space-time as you travel.

16. ### MetryqFleet CaptainFleet Captain

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Libby visits Copenhagen

Without causality, there is no science.

—METHUSELAH'S CHILDREN by Robert Heinlein

17. ### FreddyECaptainCaptain

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Alcubierre Drive is the theoretical real live version of warp drive.

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Joke. He was making a a joke.

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That is a good point. If an Apollo spacecraft were to go, say through a stargate as seen in SG1, it had better be in orbit of a habitable world or you are screwed.

I'm thinking any real space drive needed to explore in-system had better have both high specific impulse and high thrust--and NSWR is the only game in town. Land, take off, give one g thrust for hours--it is the closest thing to the Orbit Jet we will ever have.

Now in the Book THE DREAM MACHINES I do remember an airplane shaped craft that wasn't NSWR (not Aldebaran, but another one) that was a surface to surface craft.

Now what I would like to do is to find a wormhole with two mouths closer to each other in this solar system.

I wouldn't want them on Earth, but if I could find a way to make one wormhole mouth unidirectional--you would have the ultimate rocket.

You toss one wormhole mouth into the sun, and have a huge fusion jet out of the mouth of the other. There is your rocket.

A rocket with no fuel tank--saturday morning cartoons come to life. Push asteroids around at well, transport thousands of tons at speed, etc. Now it would take a long time to drain the sun, so this thing could just circle in system waiting to be recalled.

You push on to another, somewhat larger star, back and forth..and then throw the wormhole from the rocket into the other sun. That star becomes less massive, and lives longer, and our sun has fresh hydrogen.