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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Thu, 8 Mar 2001 07:16:11 GMT
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Viewed:
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612 times
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J.D. Forinash <foxtrot@cc.gatech.edu> wrote in message
news:986560$3pl$1@y2.bufordnet.foo...
> In article <G9uEuL.Coq@lugnet.com>, Damraska <Damraska@Excite.com> wrote:
> > 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).
>
> 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 compartment-on-a-stick-with counterweight so that it rotates
> on an axis perpendicular to the thrust vector. Simply spin it down so it
> points in the right direction for acceleration or deceleration.
>
> Of course, that counterweight idea sounds heavy, too. So you build it so
> it's two compartments on a stick, one of which can rotate at the end of
> the stick, and it gets turned around on acceleration or deceleration.
I considered and discarded that methodology, but upon reflection, I cannot
think of a good reason why. It could work. The probability of something
breaking under thrust increases with more moving parts, and the ship you
describe requires a joint that turns the axis of rotation 90 degrees. It
would look pretty, but my guts tell me it is too flimsy to work. Of course,
a torus with rotating compartments is not exactly simple, and I left that in
there.
> > That's only the start of your problems. :) High Z particles will render
> > all of your minifigs blithering idiots unless you include adequate • shielding
>
> ...so is that why they've all got that silly smile on their faces...
I always thought it was because the minifigs from old sets are really smug
around minifigs from the new ones.
> > 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.
>
> Hm. I note we don't tend to build asteroids around our own current space
> stations... Is this a proximity-to-earth-shields-us deal? Or do we just
> build sufficient shielding into, say, ISS? Or is six months of exposure
> insufficient for blithering? I would guess with the very small density of
> stars running around that this is really only an issue early on (leaving a
> star system) and late (arriving at one...)
Earth serves as a huge radiation shield, yes. The issue is length of
exposure. According to current estimates, during a trip to Mars, every cell
in an astronaut's body will suffer at least one collison with a high energy
particle. This could result in a great deal of cellular damage. (To a
lesser extent, *every* astronaut who makes a trip into space experiences
this.) Unless you use something to deflect or absorb high energy particles,
travel near any stellar body for any length of time comprises a serious
health hazard. Out in interstellar space, I do not believe it is nearly as
big an issue, unless you head into a nebula at 0.5c or something.
> > 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
>
> This is where I was always wondering how a ramjet could work-- see, the
> problem is that that hydrogen wasn't moving before, and once you've • scooped
> it up, it is now. Which means you had to spend energy somewhere to impart
> that energy on the hydrogen, i.e, you decelerated some to make up for the
> fact that you collected the hydrogen. Which, to me, means you may as well
> have brought it with you from the start. The only weight you really save
> is what it took to build the bigger hydrogen tanks.
This may be why the whole idea was discounted. I wish I could find that
article. The question is, does the amount of energy expended to decelerate
the hydrogen exceed the energy generated when you burn it. If yes, no
ramjet. It may work up to a certain speed, where the breaking energy equals
the resulting burn energy.
> And it'd _really_ suck to find out that the hydrogen gets thinner than
> expected between stars...
Yes, but the ship is probably traveling at a significant velocity by then,
anyway. Any minifigs planning such a trip should expect in flight delays in
advance--perhaps a dew decades.
> > 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
>
> Ah. Nuclear bombs also emit lots o' radiation. Which means that this • method
> might be used to solve the stellar radiation problem, as well. The same
> shield you use to protect you from one can protect you from another, and
> elegantly enough, that shield is pointed the right direction-- after all, • you
> accelerate away from stars, and decelerate toward them.
Yup. Exactly.
> Adding in slingshotting around other stars, on the other hand, will change
> this problem... pointing the shield at the sun means you're now • accelerating
> in a direction your ship was not designed to accelerate in, and you now • need
> those redundant workstations, but in the upper left hand corner of the
> ceiling... Perhaps we shouldn't slingshot...
I guess you could make the crew spaces a sphere inside a sphere, but
building that in lego at minifig would be ugly. A box inside a gyroscope
would work.
> > 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.
>
> Something that, say, catches solar radiation? :) I'd guess that this
> could also solve the stellar radiation problem, too. You'd need to know • just
> how much solar wind can be expected on the other end, though, and adjust
> your sail size to compensate. It'd really suck to find out there was less
> on the other end and shoot past your destination with your only means of
> propulsion being designed to take you in what's now by definition the
> wrong direction.
Unfortunately, a sail only catches photons, not high energy particles, so
the need for a shield remains. Maybe solar sailors should take along some
nuclear weapons for added stopping power, just in case.
> > 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.
>
> Or, perhaps, one could theorize that the current cutting-edge work going
> on in Physics into trying to separate out subatomic particles from one
> another might yield something. THe Higgs particle, IIRC, is one theorized
> to have something to do with gravity/mass.
>
> The trick here, of course, is to get the gravity without the mass.
That, in my mind, is the sci-fi gravity generator. It may just work, but
not just yet. :)
> I think I'm really glad I just stick 4x4x2 rocket cones on the back and • use
> studs for gravity.
I personally lean towards the 3x3x2 rocket cones these days. They seem more
sleek to me.
-Doug
Minifig Suns: http://pages.prodigy.net/damraska/
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Message has 2 Replies:
 | | Re: Where's all that gravity coming from?
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| (...) It does have the annoyance that spinning up/spinning down affects both parts of the ship, so you have to use small thrusters to get pointing in the right direction before you can fire the main engine. This, interestingly enough, has a neat (...) (24 years ago, 8-Mar-01, to lugnet.space)
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Message is in Reply To:
| | 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)
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