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-   -   Alcubierre Drive - A thought excercise. (http://www.trekbbs.com/showthread.php?t=221098)

sojourner July 28 2013 11:20 PM

Alcubierre Drive - A thought excercise.
 
I was thinking about this today and thought it might make an interesting topic.

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.

StarCruiser July 29 2013 03:25 AM

Re: Alcubierre Drive - A thought excercise.
 
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).

Lindley July 29 2013 04:49 AM

Re: Alcubierre Drive - A thought excercise.
 
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.

JustAFriend July 29 2013 02:43 PM

Re: Alcubierre Drive - A thought excercise.
 
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....

Psion July 29 2013 04:04 PM

Re: Alcubierre Drive - A thought excercise.
 
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.

YellowSubmarine July 29 2013 06:41 PM

Re: Alcubierre Drive - A thought excercise.
 
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/sē 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.

sojourner July 29 2013 07:59 PM

Re: Alcubierre Drive - A thought excercise.
 
^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".

PurpleBuddha July 29 2013 08:08 PM

Re: Alcubierre Drive - A thought excercise.
 
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?

YellowSubmarine July 29 2013 08:48 PM

Re: Alcubierre Drive - A thought excercise.
 
Quote:

sojourner wrote: (Post 8442958)
And hey, it was merely a thought exercise. I never said it was "realistic".

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).

Quote:

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?
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.

Quote:

PurpleBuddha wrote: (Post 8442994)
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?

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

sojourner July 29 2013 11:14 PM

Re: Alcubierre Drive - A thought excercise.
 
^A NASA scientist has come up with a revision that reduces the amount of energy required from "insane" to something less than "improbable".

Psion July 31 2013 05:47 PM

Re: Alcubierre Drive - A thought excercise.
 
Quote:

sojourner wrote: (Post 8442958)
^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".

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

JarodRussell August 1 2013 12:56 PM

Re: Alcubierre Drive - A thought excercise.
 
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?

Quote:

JustAFriend wrote: (Post 8441701)
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....

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.

Quote:

PurpleBuddha wrote: (Post 8442994)
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?

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

Lindley August 1 2013 04:17 PM

Re: Alcubierre Drive - A thought excercise.
 
Speedy thing goes in, speedy thing comes out.

scotpens August 1 2013 04:41 PM

Re: Alcubierre Drive - A thought excercise.
 
Alcubierre Drive? Never heard of it. Sounds like a street in Beverly Hills.

Ronald Held August 1 2013 06:40 PM

Re: Alcubierre Drive - A thought excercise.
 
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.


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