# 10619 bysailorbarsoom@... on April 28, 2008, 11:39 p.m.
Member since 2021-10-03
So I'm imagining a bunch of kids in a Bernal sphere hopping on their
bicycles and riding to school in the morning. And suddenly I see them
all riding straight (OK, around the curved inner surface) and leaning
to the left. Those riding in the opposite direction are leaning
right. Both of them are leaning the same direction, of course, but
the riders have to remember "On the way to school, I lean left. On
the way home, I lean right."
special tires, or would plain old bicycle tires do it?
# 10620 byian.woollard@... on April 29, 2008, 1:14 a.m.
Member since 2021-10-03
2008/4/29 sailor.barsoom :
> So I'm imagining a bunch of kids in a Bernal sphere hopping on their
> bicycles and riding to school in the morning. And suddenly I see them
> all riding straight (OK, around the curved inner surface) and leaning
> to the left. Those riding in the opposite direction are leaning
> right. Both of them are leaning the same direction, of course, but
> the riders have to remember "On the way to school, I lean left. On
> the way home, I lean right."
Yeah, it is actually.
In a rotating frame of reference, there's two pseudoforces that
appear, centrifugal force that pushes you outwards with a g-force
proportional to your distance from the spin axis, and Coriolis force
that kicks in when you start to move.
Coriolis only kicks in though when you climb up/down or go
upspin/downspin. Going along the axis (north/south or whatever you
want to call it) doesn't do anything per se.
Coriolis acts at 90 degrees to your speed in the plane your spinning
in. So if you run downspin, coriolis pushes you harder into the deck.
If you run upspin it lightens you. If you drop something it pushes it
upspin, if you raise it up, it pushes downspin.
Hope you're with me so far.
The bottom line is that cycling on the 'flat' (i.e. constant radius
from spin axis, for example going equatorially around a Bernall
sphere) does nothing more than make you heavier or lighter, but for
example, going downhill or uphill along the spin axis (north/south)
will mean you will have to lean the bike to compensate for Coriolis,
and yes, it does depend whether you're going up or downhill- it will
be opposite directions!
--
-Ian Woollard
We live in an imperfectly imperfect world. If we lived in a perfectly
imperfect world things would be a lot better.
# 10621 bysailorbarsoom@... on April 29, 2008, 3:22 a.m.
Member since 2021-10-03
--- In spacesettlers, "Ian Woollard" wrote:
> In a rotating frame of reference, there's two pseudoforces that
> appear, centrifugal force that pushes you outwards with a g-force
> proportional to your distance from the spin axis, and Coriolis force
> that kicks in when you start to move.
space dwellers weight.
> Coriolis only kicks in though when you climb up/down or go
> upspin/downspin. Going along the axis (north/south or whatever you
> want to call it) doesn't do anything per se.
Think I get this too. If my student lives due north or south from
school (and doesn't have to go uphill or downhill), she can ignore
Coriolis while biking to and from Gerard O'Neill High.
> Coriolis acts at 90 degrees to your speed in the plane your spinning
> in. So if you run downspin, coriolis pushes you harder into the
> deck.
> If you run upspin it lightens you. If you drop something it pushes
> it upspin, if you raise it up, it pushes downspin.
>
> Hope you're with me so far.
I think so. We'll call the direction of spin "west" and the anti-spin
direction "east" and assume them to be left and right of a person
facing north, respectively (it is on Earth). With the several hundred
KmPH that a habitat spins, the gains and losses in weight would hardly
be noticeable, unless you are a champion racer or something.
But if I drop a shot-put, it won't fall (from my POV) straight down.
It will move slightly to the west. How much depends on how high the
drop is and how fast the habitat is spinning. If I care about the
condition of my toes, I'll take this into account (or just not drop
the danged thing). If I toss it straight up, it moves to the east...
until it starts back down, at which time it starts curving to the west.
> The bottom line is that cycling on the 'flat' (i.e. constant radius
> from spin axis, for example going equatorially around a Bernall
> sphere) does nothing more than make you heavier or lighter, but for
> example, going downhill or uphill along the spin axis (north/south)
> will mean you will have to lean the bike to compensate for Coriolis,
> and yes, it does depend whether you're going up or downhill- it will
> be opposite directions!
OooooooK. I think I get this. If our high school bicyclist is going
uphill and north, she will feel a force pushing her west (left, from
her POV). However, if she then turns around and rides downhill and to
the south, she will feel pushed to the east (still left, for her). In
both cases, she leans RIGHT to compensate.
If she then rides over a section where she neither gains nor loses
altitude (a cylindrical section near the equator?) she feels no force
to the side, and rides upright, like on Earth.
But, if she continues to the south and starts going uphill again, she
will feel pushed to, um... to the west again, only now this is right
to her. Coming back downhill, she will be pushed east again, which
again will be right. In both cases, she leans LEFT to compensate.
WHEW!!
So it isn't "lean right going to school and left coming home," it's
"lean east going uphill and lean west going downhill."
I'm pretty sure I've got this, now. And yes, I'm writing a scene of a
high school girl riding her bike to school. I'll post it here when I'm
done, if anybody wants to read it.
# 10622 bysailorbarsoom@... on April 29, 2008, 3:25 a.m.
Member since 2021-10-03
I apologize for the BUTT-UGLY formatting of my last post. I did
everything I could think of, and deleted it twice trying to fix it.
The stupid line brakes, and it doesn't show that to you in "Preview,"
and I hates it gollum gollum.
# 10623 byian.woollard@... on April 29, 2008, 3:54 a.m.
Member since 2021-10-03
For extra marks, I'll include the equation for the acceleration.
where v is the velocity vector and w is the rotation vector (aligned
with the rotation axis, of length the rotation speed in radians per
second), x is the cross product.
For somebody on an x% gradient at a speed of v, going north south in a
habitat of radius r and an equatorial gravity of g
|w| = SQRT(g/r)
The vertical component of the speed is x*v
so stripping away all the vector stuff the sideways acceleration is 2
SQRT(g/r)*(x*v)
g = 10 (the engineer decided not to match the earth precisely!)
r = 1000
x = 0.333 (1 in 3)
v = 50 km/h (31 mph, 13.9 m/s... wheee!)
acoriolis = 2*SQRT(10/1000)*(0.333*13.9) = 0.92 m/s^2
Now the vertical g varies proportional to distance from the axis, but
at the bottom of the hill that's an angle of ARCTAN(0.92/10) = 5.3
degrees not as much as I expected.
I *think* I did it right. It's going to be more at the top of the hill
because the g is lower. It's also going to be more significant in
smaller habitats.
--
-Ian Woollard
We live in an imperfectly imperfect world. If we lived in a perfectly
imperfect world things would be a lot better.
# 10624 byspider_boris@... on April 29, 2008, 12:55 p.m.
Member since 2021-10-03
This is the sort of thing that would give soccer
goalies nightmares.
# 10625 bysailorbarsoom@... on April 29, 2008, 4:19 p.m.
Member since 2021-10-03
Thanks. Due to my inumeracy, I can't do a lot with this, but I'll
keep it around in case I have a guest who can or I suddenly become
enlightened.
for that!) to use this on my behalf.
# 10626 byrussell.wallace@... on April 29, 2008, 11:34 p.m.
Member since 2021-10-03
On Tue, Apr 29, 2008 at 4:11 AM, sailor.barsoom wrote:
> I'm pretty sure I've got this, now. And yes, I'm writing a scene of a
> high school girl riding her bike to school. I'll post it here when
> I'm done, if anybody wants to read it.
to see the story when it's done.
# 10627 bysailorbarsoom@... on April 30, 2008, 2:10 a.m.
Member since 2021-10-03
--- In spacesettlers, Ed Minchau wrote:
> goalies nightmares.
The girl on the bicycle is also a center midfielder, though she plays
the weightless cylindrical version.
Which means non-rotating. Which might be while she plays it.
# 10628 bysailorbarsoom@... on April 30, 2008, 2:44 a.m.
Member since 2021-10-03
--- In spacesettlers, "Russell Wallace" wrote:
> I'd like to see the story when it's done.
Thanks. The bike-riding scene turned out pretty dull, as she
neither gained nor lost altitude, and was slow enough that gains
or losses in weight were negligible. However, I'd really like to
include this, and will be looking for an opportunity to put her
back on that bike.
Here is the dull bike ride:
When I got downstairs, my pancakes were waiting for me.
Dad usually made them after eating his own breakfast.
Sometimes I'd see him just before he left. Today he was
already gone, and as I glanced at the clock, I realized
that, in spite of dressing so fast, I was running a
little behind. It was the shower. I'd let my mind wander
to what was going to happen today after I got to school.
I ate in a hurry and left, riding my bike instead of
walking like I usually do. Today of all days I didn't dare
be late. I didn't want anybody thinking that I was trying
to get out of anything. I rode off in fine form, my slacks
feeling a little tight. Well, I wouldn't have to worry about
that for long. I waved to a few other people as we rode
along. I guess I should mention that we only use cars for
emergencies, and those are electric. The whole circumference
here is little more than six Km, so it takes little time to
get from one place to another.
It was a bright day, and there was no rain scheduled. Yes, we
control our weather here. That would be almost impossible on a
full-sized planet like Earth, but it's easy enough here. An I2
is big enough to generate some of its own weather, but small
enough to keep it under control. The weather in the I3's is
harder to control, and letting it be a bit unpredictable is
considered part of the charm of living there. They can have it,
I thought.
I glanced up, and saw a couple of fliers, almost at the axis.
Remember how I mentioned that the higher you climb, the less you
weigh? Well, when it gets down to sixteen percent or so, you
can strap on wings and fly by flapping. I fly sometimes, but
I'm more of a swimmer.
I got to Principle Takahashi's office just in time to see Neil
Collins leaving.
# 10629 byrussell.wallace@... on April 30, 2008, 6:08 p.m.
Member since 2021-10-03
On Wed, Apr 30, 2008 at 3:18 AM, sailor.barsoom wrote:
> Thanks. The bike-riding scene turned out pretty dull, as she neither
> gained nor lost altitude, and was slow enough that gains or losses in
> weight were negligible. However, I'd really like to include this, and
> will be looking for an opportunity to put her back on that bike.
have been on Earth. On the other hand, I liked the bit about people
disagreeing on whether it's charming to live on a habitat big enough
to have uncontrolled weather :)
1/6 g low enough to fly by flapping wings - do you have a source for
that, or was it an off the cuff guess? My guess for what it's worth is
that you'd need to go a bit lower, particularly in an environment with
few or no thermals to glide on, but I'm really not sure of the answer.
# 10630 bymikecombs@... on April 30, 2008, 8:04 p.m.
Member since 2021-10-03
From: Russell Wallace
> that, or was it an off the cuff guess? My guess for what it's worth is
> that you'd need to go a bit lower, particularly in an environment with
> few or no thermals to glide on, but I'm really not sure of the answer.
Marshall Savage seemed to think human flight would be possible in his
moon domes. Of course I've seen varying opinions on Savage's expertise
on such matters.
One complication is that a moon-dome or orbital habitat is apt to have
an atmosphere half as dense as what we're used to (and I think Savage
assumes even lower pressures), which makes flight more difficult.
But one of the charms of rotating habitats is that no matter how low a
gravity level is required to have personal flight, there will be some
corresponding location.
Human flight might be easiest on Titan. Gravity is even lower than on
our moon, but the atmosphere is 1.5 times as dense as the air we're
breathing. It wouldn't exactly be correct to say that one had the
encumbrance of a spacesuit, though. You would need an oxygen mask and a
high-insulation thermal suit.
Regards,
Mike Combs
# 10631 byrussell.wallace@... on April 30, 2008, 8:13 p.m.
Member since 2021-10-03
On Wed, Apr 30, 2008 at 9:03 PM, Combs, Mike wrote:
> One complication is that a moon-dome or orbital habitat is apt to have
> an atmosphere half as dense as what we're used to (and I think Savage
> assumes even lower pressures), which makes flight more difficult.
because that lets a few more kilograms of weight be shaved from the
hull, but that incentive wouldn't apply to a habitat, would it?
> But one of the charms of rotating habitats is that no matter how low a
> gravity level is required to have personal flight, there will be some
> corresponding location.
True! Just remember your parachute in case you accidentally drift away
from the axis :)
> Human flight might be easiest on Titan. Gravity is even lower than on
> our moon, but the atmosphere is 1.5 times as dense as the air we're
> breathing. It wouldn't exactly be correct to say that one had the
> encumbrance of a spacesuit, though. You would need an oxygen mask and a
> high-insulation thermal suit.
Which is still a _lot_ easier to move in than a pressure suit.
# 10632 byjoe@... on April 30, 2008, 8:49 p.m.
Member since 2021-10-03
On Apr 30, 2008, at 2:03 PM, Combs, Mike wrote:
> an atmosphere half as dense as what we're used to (and I think Savage
> assumes even lower pressures), which makes flight more difficult.
>
I imagine that flight on the Moon won't be in general "living domes,"
but in structures (aviaries?) built specifically for that purpose.
That could include a (possibly leaky) airlock for entering and
exiting, so that the dome could have a higher air pressure if necessary.
Of course fliers might have to keep an eye on their blood nitrogen
levels, especially if they're planning to go outside in a space suit
shortly after some time in the aviary. But this is no different from
what scuba divers do today.
Best,
- Joe
# 10633 bysailorbarsoom@... on May 1, 2008, 12:22 a.m.
Member since 2021-10-03
--- In spacesettlers, "Russell Wallace" wrote:
> have been on Earth. On the other hand, I liked the bit about people
> disagreeing on whether it's charming to live on a habitat big enough
> to have uncontrolled weather :)
I assume that the people in the bigger habitats control their weather
a *little bit.* There's charming, and then there's plain uncivilized. ;)
> 1/6 g low enough to fly by flapping wings - do you have a source for
> that, or was it an off the cuff guess? My guess for what it's worth is
> that you'd need to go a bit lower, particularly in an environment with
> few or no thermals to glide on, but I'm really not sure of the answer.
I can't point you to an actual paper on the matter, but Edgar Rice
Burroughs, Robert A. Heinline and Marshall Savage all said it can be
done. However, I do recall that Heinline in _The Menace From Earth_
stated that the aviary (don't remember if he called it that, but it's
a good name, Joe Strout) had a slightly higher than Earth sea level
pressure. For my story, I'm assuming 75% sea level, at least at the
equator. I do have to wonder if it might thin out too fast.
# 10634 byian.woollard@... on May 1, 2008, 12:38 a.m.
Member since 2021-10-03
2008/4/30 Combs, Mike :
> Marshall Savage seemed to think human flight would be possible in his
> moon domes. Of course I've seen varying opinions on Savage's expertise
> on such matters.
certainly would be possible on the moon in domes, it would be 6x
easier.
I don't think that an unaided person could fly just by flapping their
arms though ;-)
> Mike Combs
--
-Ian Woollard
We live in an imperfectly imperfect world. If we lived in a perfectly
imperfect world things would be a lot better.
# 10635 byjoe@... on May 1, 2008, 1:35 a.m.
Member since 2021-10-03
On Apr 30, 2008, at 6:38 PM, Ian Woollard wrote:
> Well, human *powered* flight has been done on Earth, and so it
> certainly would be possible on the moon in domes, it would be 6x
> easier.
>
> I don't think that an unaided person could fly just by flapping their
> arms though ;-)
>
experience as strapping on a flight suit and flapping away.
When my kids reach high school, I'm going to try to subtly push the
idea of doing a detailed simulation/analysis of possible flight suit
designs under various gravity and air pressure levels as a science
fair project. :)
Best,
- Joe
# 10636 bysailorbarsoom@... on May 1, 2008, 3:25 a.m.
Member since 2021-10-03
--- In spacesettlers, Joe Strout wrote:
>> Well, human *powered* flight has been done on Earth, and so it
>> certainly would be possible on the moon in domes, it would be 6x
>> easier.
>>
>> I don't think that an unaided person could fly just by flapping
>> their arms though ;-)
> Well yes, but pedaling an ultralight is not at all the same
> experience as strapping on a flight suit and flapping away.
That's right!
> When my kids reach high school, I'm going to try to subtly push the
> idea of doing a detailed simulation/analysis of possible flight suit
> designs under various gravity and air pressure levels as a science
> fair project. :)
OOOOO!!!!!
That sounds interesting. Too bad I don't talk to many high school
kids. I'd suggest it myself.
I have a nephew and some nieces in high school, and don't even really
know what they are taking. Well, except that the one niece is being
run ragged by band, color guard, and extra credit projects. I don't
know to be proud or worried.
# 10637 bymikecombs@... on May 1, 2008, 1:57 p.m.
Member since 2021-10-03
From: Russell Wallace
> because that lets a few more kilograms of weight be shaved from the
> hull, but that incentive wouldn't apply to a habitat, would it?
It would apply in spades to large habitats where we would measure the
hull not in square meters but in square kilometers.
Although in this case the weight would be less the issue than the
expense of construction.
O'Neill assumed air at one-half the pressure with twice the percentage
of oxygen. Zubrin and Savage assume even lower pressures with even
higher O2 percentages.
Regards,
Mike Combs
# 10638 byrussell.wallace@... on May 1, 2008, 8:22 p.m.
Member since 2021-10-03
On Thu, May 1, 2008 at 2:56 PM, Combs, Mike wrote:
> From: Russell Wallace
>
> > Is there a reason for the low density? It's low in today's spacecraft
> > because that lets a few more kilograms of weight be shaved from the
> > hull, but that incentive wouldn't apply to a habitat, would it?
>
> It would apply in spades to large habitats where we would measure the
> hull not in square meters but in square kilometers.
>
> Although in this case the weight would be less the issue than the
> expense of construction.
shielding anyway, but much of that could be machinery, water reserves,
coolant pipes and suchlike, not all of it need be the load-bearing
shell. So if the atmosphere is 1 bar, that's 10 tons/m^2 of load on
top of everything else; it bumps up the required shell thickness quite
substantially. So yeah, there is an incentive to reduce the air
pressure as much as you can reasonably get away with.
# 10639 byjoe@... on May 1, 2008, 8:28 p.m.
Member since 2021-10-03
On May 1, 2008, at 2:22 PM, Russell Wallace wrote:
> Actually you're right, it would. You need a few tons/m^2 for radiation
> shielding anyway, but much of that could be machinery, water reserves,
> coolant pipes and suchlike, not all of it need be the load-bearing
> shell.
>
dirt anyway to plant trees in, dig gardens in, bury pipes and wires
in, etc., and that right there will meet most or all of your
radiation-shielding needs.
Best,
- Joe
# 10640 bysailorbarsoom@... on May 2, 2008, 5:33 a.m.
Member since 2021-10-03
--- In spacesettlers, Joe Strout wrote:
>> Actually you're right, it would. You need a few tons/m^2 for
>> radiation shielding anyway, but much of that could be machinery,
>> water reserves, coolant pipes and suchlike, not all of it need
>> be the load-bearing shell.
This is true. A radiation shield made of water could also be the main
reservoir... or the main sewer.
> And don't forget the dirt! I'd want a couple meters (at least) of
> dirt anyway to plant trees in, dig gardens in,
You betcha.
> bury pipes and wires in, etc.,
I'd rather these things not be buried in dirt. If they are, then when
something goes wrong, you've got to did them back up. I'd rather have
a "basement" of sorts, where these things are located. Then, when
something breaks you just walk up to it and fix it, with no digging
required.
> and that right there will meet most or all of your
> radiation-shielding needs.
Yeppers. I think two metres is enough for just about anything, and is
enough for the shield.
# 10641 bydsw_s@... on May 3, 2008, 12:35 a.m.
Member since 2021-10-03
--- In spacesettlers@yahoogroups.com, Joe Strout wrote:
> dirt anyway to plant trees in, dig gardens in, bury pipes and
wires
> in, etc., and that right there will meet most or all of your
> radiation-shielding needs.
Why so much dirt? When a tree blows over and rips up the roots along
with all the dirt caught in them, it's a sheet of sod about half a
meter thick. If you have more dirt than you need, all that
nonstructural mass makes the whole thing more expensive relative to
its size. Burying pipes on top of a floor doesn't make sense when
you can hang them below the floor; if it were practical, why don't we
have dirt floors in very large buildings on earth?
Also, don't forget impact shielding. Your dirt needs to be on the
inside of your air barrier, whereas your impact shielding needs to be
on the outside.
As I've said in other postings here, there's a natural size for
habitats (given a particular choice of tensile structural material,
air pressure, amount of pseudogravity, and distribution of
micrometeoroids to protect against) where the thickness of cable wrap
necessary to offset the air pressure and weight is enough that it and
the impact shielding provide all your radiation shielding.
# 10642 bydsw_s@... on May 10, 2008, 3:34 p.m.
Member since 2021-10-03
A reservoir that you can't empty without irradiating yourselves isn't
serving its purpose as a reservoir very well.
wrote:
# 10643 bysailorbarsoom@... on June 11, 2008, 8:12 p.m.
Member since 2021-10-03
I've found an excuse to put her back on that bicycle and have her ride
off at right angles to the spin and go uphill. I can post the new
scene here if you like.
nudity and personal embarrassment. Not so much in this scene, but
it's unmistakably there.
There isn't any sex,[*] and mostly it's a bit of a geeky description
of riding a bicycle in a Bernal Sphere. But the public nudity and
embarrassment is there. If this squicks you, then you either need to
read the scene prepared to be squicked, or not read it.
In fact, I'm not even posting it unless I get a lot of "go ahead" replies.
- Sailor Barsoom (aka Xenophile)
[*] In this part of the story. Later chapters will have it.
# 10644 bysailorbarsoom@... on June 11, 2008, 8:13 p.m.
Member since 2021-10-03
Is there any way to get rid of these @#%@!@#$ page breaks that I DID
NOT PUT HERE?!?!?!?!?!?
# 10645 byhitssquad@... on June 12, 2008, 8:48 p.m.
Member since 2021-10-03
--- In spacesettlers, sailor.barsoom wrote:
> I've found an excuse to put her back on that bicycle
> and have her ride off at right angles to the spin and
> go uphill. I can post the new scene here if you like.
# 10646 bysailorbarsoom@... on June 13, 2008, 9:30 p.m.
Member since 2021-10-03
I've gotten exactly two requests to post this thing. I don't want to
inflict it on those not interested, or on those who would be squicked
by some of the themes. So I am going to mail it to those two guys.
a pain. ^_~