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 15:49:04 GMT
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Viewed:
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645 times
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In article <G9v9or.19J@lugnet.com>, Damraska <Damraska@Excite.com> wrote:
> I considered and discarded that methodology, but upon reflection, I cannot
> think of a good reason why. It could work. The probability of something
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 side-effect, I think: Since the
"non-rotating" section actually rotates, why not make it identical to the
rotating section? It would then rotate the same speed the other direction,
and, well, centripetal force doesn't care which direction you rotate. You
have to be careful in the hub going from section to section (as the rotational
speed from there looks like _twice_ what you'd guess...), but it's probably
do-able. Though maybe not in Lego-- I can't think of a rotation mechanism in
Lego that doesn't involve something at the center of the hub, which implies
axles, which are now counter-rotating and happily decapitating our minifigs
as they try to move between arms.... Perhaps you just don't switch arms
while spinning...
> 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.
True, but since the parts aren't moving under thrust, you can put nice thick
pins in everything to keep it stationary when you're doing that. And the
thrust vector would be in line with the shafts of the ship, so you don't
have to worry about shear strength as much, just compression strength,
except at those nice thick pins. Or you don't bother with a rotating
crew section at the end of one stick, and migrate the minifigs to the
other end of the ship. But that seems wasteful. More so than rotating
assemblies and pins? I dunno.
> 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.
If I remember my particle dynamics correctly, the amount of energy it takes
to get a hydrogen particle from stationary to velocity V is equal to the
amount of energy it takes to get a hydrogen particle from stationary to
velocity V no matter when you do it, at the start or in the middle of
space. It's not an issue of how much energy can you get from the hydrogen--
it's an issue of "You're gonna have to accelerate this hydrogen anyhow."
Which is heavier, the bigger hydrogen tank or a Bussard scoop, figuring
that you have to either a) collect all the hydrogen you need to slow
down (read: half of what you need total) or b) have a Bussard scoop that
you can point in the direction opposite of your thrust, which seems even
more fragile than some of the other stuff? And even so, decelerating,
once you get slow enough it becomes approximately useless anyhow.
Basically, a Bussard scoop saves you half (ish) of what size your hydrogen
tanks need to be.
> anyway. Any minifigs planning such a trip should expect in flight delays in
> advance--perhaps a dew decades.
True. Which brings us to another real problem with minifig space travel: how
do you keep your blue ship from turning yellow over the decades? The thread
in .general implies it's not sunlight that yellows bricks. :)
> 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.
But still has the shielding problem-- after all, the more stars we spend
time near, the more high energy particles hit our poor minifigs. Also,
given the fact that these primitive ships would be heading toward close stars,
chances are slingshotting won't get us much except maybe a decent way to slow
down on the other end.
> Unfortunately, a sail only catches photons, not high energy particles, so
On the one hand, I want to say, "Well, why not just build it to catch high
energy particles, too?" but on the other hand, we've already noted that
that takes heavy steel plates or asteroids, and now we've got too much mass
for a solar wind even augmented by HE particles to accelerate us. So a
smaller shield would indeed be a better idea.
> the need for a shield remains. Maybe solar sailors should take along some
> nuclear weapons for added stopping power, just in case.
Why not? They've got the shield already. :)
> I personally lean towards the 3x3x2 rocket cones these days. They seem more
> sleek to me.
I'd thumb my nose at you and say, "Ha! What good is sleek in space?", but
the real reason I use 4x4x2 ones is because I don't have as many 3x3x2
cones. :)
-JDF
--
J.D. Forinash ,-.
foxtrot@cc.gatech.edu ( <
The more you learn, the better your luck gets. `-'
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Message has 2 Replies:
 | | Re: Where's all that gravity coming from?
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| (...) Would it be possible to make a Bussard scoop out of some kind of projected magnetic field? Two basic questions here: 1. do hydrogen atoms react to magnetic fields and 2. could such a field be constructed/projected? Unfortunately, I don't have (...) (24 years ago, 8-Mar-01, to lugnet.space)
| | | Re: Where's all that gravity coming from?
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| J.D. Forinash <foxtrot@cc.gatech.edu> wrote in message news:9889lg$s7$1@ana...net.foo... (...) cannot (...) parts (...) right (...) rotational (...) probably (...) in (...) implies (...) minifigs (...) How about this: build a large drum (or box) (...) (24 years ago, 9-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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| J.D. Forinash <foxtrot@cc.gatech.edu> wrote in message news:986560$3pl$1@y2...net.foo... (...) for (...) the (...) I considered and discarded that methodology, but upon reflection, I cannot think of a good reason why. It could work. The probability (...) (24 years ago, 8-Mar-01, to lugnet.space)
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