Subject:
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Re: Where's all that gravity coming from?
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Newsgroups:
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lugnet.space
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Date:
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Wed, 7 Mar 2001 20:10:05 GMT
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Viewed:
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539 times
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As some people have already pointed out, you can rotate just about any
structure for artificial gravity--a drum, a torus, a rectangular box, or a
box at the end of a boom (with suitable counterweight). The problem with
this methodology is the amount of gravity you will generate. Unless you put
the rotated surface fairly far away from the center of rotation or spin the
structure really fast, you won't get 1g. Fortunately, you can make do with
a lot less (with some side effects).
If you plan to put this structure under thrust, you will need to account for
it. If your compartments are all oriented with the floors facing outward
into space, and you start thrusting along the axis of rotation, all your
minifigs will get stuck to the walls. A boom will probably snap under the
stress no matter how well you build it. Not good. When under thrust,
either the compartments need to rotate down, the compartments must have
redundant working spaces on one wall, or everyone needs to evacute to the
spine (which contains redundant working spaces).
That's only the start of your problems. :) High Z particles will render
all of your minifigs blithering idiots unless you include adequate shielding
from stellar radiation sources. An asteroid between you and any nearby star
should be sufficient. If you plan on moving through interstellar space at
any significant velocity, you better push it in front of your ship, too.
All of this will require a *lot* of mass (even if you find a substitute for
the asteroid) and you need to move it. Assuming you also ban 'sci-fi
drives', you only have a limited set of options. You can forget rocket fuel
because you need more fuel to accelerate the fuel you take and so on. You
need something that will get you a lot of bang for very little mass. I can
think of three choices--a Bussard Ramjet (which I understand was recently
shown as unworkable), Orion, or a solar sail. A Bussard Ramjet works like
this: interstellar space contains some atomic matter (mostly hydrogen) but
the density is exceptionally low. However, if you travel *really* fast, you
will cover a lot space in a very short amount of time. If you stick a scoop
on the front of your ship and collect all those stray hydrogen atoms, you
will end up with a lot of free hydrogen fuel (free in the sense that you did
not need to accelerate it with your ship). If you use that hydrogen as fuel
for a fusion reaction, you have thrust. The problem is getting up to speed
to make the ramjet work. Method two is Orion: you build your ship on top
of a big metal plate and pump nuclear bombs behind your ship. As they
detonate, you get thrust (and lots of it). Method three, the solar sail, is
probably the most workable--if you can come up with a material for the sail.
There was also mention of using quantum black holes for gravity. That
introduces a few problems too. First, a quantum black hole has the mass of
a mountain or perhaps a large asteroid. How much gravity does a large
asteroid generate? Not much. A quantum black hole doesn't generate any
more (though the fact it is compressed to a point helps because you can get
closer to it, so to speak). Second, a quantum black hole has the mass of a
large mounatin or asteroid, and you have to move it with the rest of your
ship. Third, you have to contain the thing or it will hit the floor, eat a
little of it, and throw off a ton of really harmful radiation. This is
doable, but you will have to haul along the equipment to build an
electromagnetic containment bottle and it is heavy.
If I were going to build a hard sci-fi interstellar ship, I think it would
be Orion with a Bussard Ramjet on the front and 'sci-fi' shielding against
interstellar radiation. I would use a box for the spun section put working
surfaces on the walls (for use under spin) and floor (for use under thrust).
If I were going to use sci-fi tech, I would use point to point spacetime
folding for my gravity and movement and probability radiators for shielding.
Oh wait. I did that. :)
-Doug
Minifig Suns: http://pages.prodigy.net/damraska/
William R. Ward <hermit@bayview.com> wrote in message
news:m2r90bye2i.fsf@komodo.bayview.com...
>
> I don't believe that gravity generators will ever be a viable
> technology. Even if it were possible to create such a thing, they
> would likely cause a lot of undesirable effects.
>
> So I try to design my MOC's (at least my more recent ones) to be
> viable in a zero-G environment. However, since humans seem to
> function better with at least some exposure to gravity, that needs to
> be provided in some way. There are two basic ways to generate gravity
> in space:
>
> 1. Rotation - centripetal force can be used to generate a gravity of
> sorts.
>
> 2. Continuous Acceleration - pedal to the metal the whole way: turn
> the ship around halfway and then continuously decelerate as you
> approach your destination.
>
> Oddly enough, the biggest obstacle to designing realistic MOC's that
> use either of these approaches is the same: a lack of curved bricks.
>
> To build a centrifuge you need to make a large (at least 30 studs in
> diameter at minifig scale, I would say) ring. And it has to be
> airtight of course. I don't know of any way to do this using the
> tools we have at our disposal, though I'd love to hear ideas.
>
> Continuous acceleration means using a LOT of fuel. And that means
> huge fuel tanks. The most realistic ships would have spherical tanks,
> and that's a little hard to do without having very jaggy spheres.
> Also, in order to get any kind of acceptable thrust you would need to
> use a form of propulsion that generates a lot of harmful radiation, so
> the ship would need a lot of shielding. (And the more shielding there
> is, the more massive the ship is, so the more thrust is needed, so
> more fuel and/or sheielding is needed, etc.)
>
> Comments?
>
> --
> William R Ward hermit@bayview.com • http://www.bayview.com/~hermit/
> -------------------------------------------------------------------------- • ---
> "Those are my principles. If you don't like them I have others."-Groucho
Marx
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Message has 6 Replies:
 | | Re: Where's all that gravity coming from?
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| (...) Redundancy sounds heavy-- but you don't need it. I don't think there's any reason why the axis of rotation has to be the same as the direction of thrust of the ship's engines. So you simply build the rotating assembly, in this case (...) (24 years ago, 7-Mar-01, to lugnet.space)
| | | Re: Where's all that gravity coming from?
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| (...) ah, well, having done the astrophysics route in school, if i were going to build a "hard sci-fi" ship, it would use a rotating magnet to tap flux (massless charge) from spacetime, create an inertial field, drop my connection to standard (...) (24 years ago, 8-Mar-01, to lugnet.space)
| | | Re: Where's all that gravity coming from?
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| In lugnet.space, Damraska wrote: [snip] (...) [snip] Here's another problem: with the conventional approach of acceleration via some propulsion, artificial gravity is not your problem. The real problem is shedding the excessive G's. My numbers could (...) (24 years ago, 8-Mar-01, to lugnet.space)
| | | Re: Where's all that gravity coming from?
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| (...) Who said anything about interstellar? I've been thinking only in terms of tooling around the Solar System... I don't think Lego is up to the task of a hard SF interstellar ship, but an interplanetary ship is a realistic goal. --Bill. (24 years ago, 9-Mar-01, to lugnet.space)
| | | Re: Where's all that gravity coming from?
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| (...) As an example, if your structure is spinning at 2 rpm, you have to go out to 225 mm from the spin axis to get 1 g. And you have to be standing with your head towards the spin axis (like a hamster in a wheel). I got thinking about what this (...) (24 years ago, 10-Mar-01, to lugnet.space)
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Message is in Reply To:
| | Where's all that gravity coming from?
|
| I don't believe that gravity generators will ever be a viable technology. Even if it were possible to create such a thing, they would likely cause a lot of undesirable effects. So I try to design my MOC's (at least my more recent ones) to be viable (...) (24 years ago, 5-Mar-01, to lugnet.space)
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