# 19702 byvictoriatangoman on April 2, 2004, 4:16 p.m.
Member since 2022-08-22
For all you engineers. If we want a spaceship with a rotating torus
section how do we mate it with a non-rotating spindle?
worthiness?
Obviously, the rotating section can be encased within a pressure
vessel, like Discovery from 2001:A Space Odyssy. Is this optimum?
Any thoughts?
TangoMan
# 19703 byvictoriatangoman on April 2, 2004, 4:19 p.m.
Member since 2022-08-22
For all you engineers. If we want a spaceship with a rotating torus
section how do we mate it with a non-rotating spindle?
worthiness?
Obviously, the rotating section can be encased within a pressure
vessel, like Discovery from 2001:A Space Odyssy. Is this optimum?
Any thoughts?
TangoMan
# 19704 byMitchell James on April 2, 2004, 6:46 p.m.
Member since 2022-08-22
Why would the spindle be non rotating? Most designs for this assume
that only the end parts of the spindle are non rotating.
Mitchell James
# 19705 byvictoriatangoman on April 2, 2004, 7:13 p.m.
Member since 2022-08-22
> Why would the spindle be non rotating? Most designs for this
assume
> that only the end parts of the spindle are non rotating.
> Mitchell James
website.
=Red+Planet+1.jpg&.view=t&.done=http%
26.view=t
It is the ship from RED PLANET. It has two counter-rotating torii.
They rotate around the spindle.
I'm wondering about the engineering of this ship.
TangoMan
# 19706 byForDutyAndHumanity IAmSpacebearAICDA on April 3, 2004, 1:26 a.m.
Member since 2022-08-22
mechanical seals bearings, oil. you could use electromagnetics as a bearing, no friiction problems but the power to them should have failsafes, make them superconductive and save on energy. also you could modifiy the electromagnetic bearing to speed up or slow down the torus or toruses. with 2 on the spindle you could have them rotate in counter to each other.
best regards pete
victoriatangoman wrote: For all you engineers. If we want a spaceship with a could rotating torus
section how do we mate it with a non-rotating spindle?
worthiness?
Obviously, the rotating section can be encased within a pressure
vessel, like Discovery from 2001:A Space Odyssy. Is this optimum?
Any thoughts?
TangoMan
# 19707 byvictoriatangoman on April 3, 2004, 7:22 a.m.
Member since 2022-08-22
--- In ssi_list@... ForDutyAndHumanity
> mechanical seals bearings, oil.
> you could use electromagnetics as a bearing, no friiction problems
but the power to them should have failsafes, make them
superconductive and save on energy.
> also you could modifiy the electromagnetic bearing to speed up or
slow down the torus or toruses. with 2 on the spindle you could have
them rotate in counter to each other.
integrity between the rotating and non-rotating sections?
TangoMan
# 19708 byMitchell James on April 3, 2004, 10:58 p.m.
Member since 2022-08-22
Here is my take on what the picture shows:
gondolas. Each one capable of being individually pressurized. Possibly
connected by couplings. Each is attached to a single solid ring. The
ring cannot be a cable because it would buckle when starting and stopping.
In order to enter or exit, the rotation of the ring must be brought to a
halt with respect to the spindle. Sort of like getting on or off a
ferris wheel. This would be okay for systems in which one did not need
continuous access to the spindle for cargo and manufacturing. The
picture therefore seems to be showing a vehicle therefore rather than a
space colony.
The best vehicle design would of course be the one with the least
surface area that would require radiation shielding and therefore the
least mass and least energy required per change in velocity. The design
has too much surface area. So the assumption would be that some problem
required a slower rotation to achieve the desired centrifugal force and
only some of the gondolas are shielded. Which of course doesn't make
any sense. Why put cargo on the ring instead of in the spindle?
Mitchell James
# 19709 byIan Woollard on April 4, 2004, 7 a.m.
Member since 2022-08-22
> For all you engineers. If we want a spaceship with a rotating torus
> section how do we mate it with a non-rotating spindle?
tunnel.
You just have a bearing to hold it centralised and multiple layers of
sliding seals around the periphery.
Between each layer of seals use vacuum pumps to minimise any leakage to
space. Vacuum pumps are capable of reducing the remaining leakage down
to countable molecules if you really want that.
> WHat would the structural problems be? How would you insure pressure
> worthiness?
There aren't any. You build it; then pressurise it up to a few times
atmospheric to test it. If it doesn't explode and you haven't got any
big leaks, it's going to be fine. Atmospheric pressure is 10 tonnes
(force) per square meter- which sounds a lot; but aluminum suitable to
keep it in is surprisingly thin- for example the pressure hatch on the
Apollo lunar lander- you could poke your finger through it (if you were
feeling suicidal; ok in practice, they ran the lunar lander at 1/3 bar
which made it 1/3 thickness, but still.)
Incidentally, a hole has to be surprisingly big to give significant
leakage. Aircraft are designed to lose a whole window, and still make it
down from 35,000 ft to 10,000 ft before all the air gets sucked out and
everyone passes out (minutes); Concorde had small windows for that
reason (it flew higher at 55000 ft so took longer to get down.) Big
holes lose pressure disproportionately faster than thin gaps around
things due to viscosity effects. So, if the pumps fail, you aren't going
to die, although you gradually lose valuable atmosphere; and so it might
be a good idea to close hatches either side.
# 19710 byvictoriatangoman on April 4, 2004, 8:58 a.m.
Member since 2022-08-22
> The picture therefore seems to be showing a vehicle therefore
> rather than a space colony.
> The best vehicle design would of course be the one with the least
> surface area that would require radiation shielding and therefore
> the least mass and least energy required per change in velocity.
Which would be a sphere, correct?
What I liked about this ship from the movie RED PLANET, was the
counter-rotating rings. Each would counter the angular momentum of
the other. Is this correct?
If there was only one ring, how would the angular momentum be
accomodated?
Here are some quick calculations:
If we want a 1.0 gravity environment:
With 6 rotations per minute the radius of the ring = 86 m
With 5 rotations per minute the radius of the ring = 97 m
With 4 rotations per minute the radius of the ring = 117 m
With 3 rotations per minute the radius of the ring = 160 m
If we want a 0.75 gravity environment:
With 6 rotations per minute the radius of the ring = 80 m
With 5 rotations per minute the radius of the ring = 88 m
With 4 rotations per minute the radius of the ring = 103 m
With 3 rotations per minute the radius of the ring = 136 m
If we want a 0.66 gravity environment:
With 6 rotations per minute the radius of the ring = 77 m
With 5 rotations per minute the radius of the ring = 85 m
With 4 rotations per minute the radius of the ring = 98 m
With 3 rotations per minute the radius of the ring = 127 m
If we want a 0.5 gravity environment:
With 6 rotations per minute the radius of the ring = 73 m
With 5 rotations per minute the radius of the ring = 79 m
With 4 rotations per minute the radius of the ring = 89 m
With 3 rotations per minute the radius of the ring = 111 m
If we want a 0.33 gravity environment:
With 6 rotations per minute the radius of the ring = 69 m
With 5 rotations per minute the radius of the ring = 73 m
With 4 rotations per minute the radius of the ring = 79 m
With 3 rotations per minute the radius of the ring = 94 m
If we want a 0.25 gravity environment:
With 6 rotations per minute the radius of the ring = 67 m
With 5 rotations per minute the radius of the ring = 70 m
With 4 rotations per minute the radius of the ring = 75 m
With 3 rotations per minute the radius of the ring = 86 m
OK, is it a good idea to have counter-rotating rings? I'm assuming
it is.
If that is what is desired, then I fall back to the design of the
Discovery in 2001:A Space Odyssey. Put the centerfuges inside the
shell of the sphere. This eliminates the pressure seal issue for the
outer shell becomes the unitary pressure vessel.
Place the two counter rotating centerfuges next to each other at the
center of the spherical shell. All of the volume outside the two
narrow centerfuges becomes zero-gravity crew quarters and storage.
If you look at the numbers above you'll see that if the crew can
survive sustained exposure to 6 rpm then the radius difference
between the different gravity simulation levels drops in smaller
increments than at lower rpms.
I know from the Stanford Torus study that they recommended a
rotation rate of less than 3 rpm so that a broad range of people
could accomodate themselves to living within the Habitat.
However, a spaceship doesn't have to have those design constraints,
and we could select a crew that can adjust to a higher rpm rate.
Does anyone have any information on how high rpm rates can go and
how long they can be sustained so that the crew can live normally.
Lastly, consider the volume of the sphere that could be used for
other purposes. If it is too much space, then perhaps we could
design a disk shaped ship within which to place the centerfuges but
now we're faced with the prospect of flat surfaces and corner joints
within the pressure vessel design. How problematic are they?
Any thoughts?
TangoMan
# 19711 bysheikyurdices on April 4, 2004, 9 a.m.
Member since 2022-08-22
posted this a couple of days ago but doesn't seem to get there, so I
think I'll repost it, apologies if you get it twice...
fundamentally flawed... ;)
The problem is not the "rotating" bit, is the torus. Why a whole torus?
The main issue I see is that in this design the entire circumference
that rotates is pressurised, and then the entire contraption needs to
spin very fast indeed to get any simulated gravity at all, being
necessarily of a small radius, while all you really want are the two
points, the center and the rotating end one, and the further apart
they are the better it is. What need there is to have a continuous
closed circumference? Why not just spin a very short section at the
end of a much longer radial arm, eventually with a second one as a
counterbalance at the other end, if needed?
Basically take your "wheel" design and multiply the radius by say a
factor of four or more, then saw off all but two very small sections
at the opposite ends of the wheel. What you are left with is a system
that spins much faster at the circumference end (where you want to
have the artificial gravity) but much slower at the hub, where you
have the bearings.
The rotating parts needs not be pressurized at all, making the
construction and maintenance that much simpler, as all you need is a
pressurized cab moving between the pressurized section at the hub and
the pressurized section at the far end(s) of the arm. The "arm" (or
arms) itself doesn't need to be pressurized and in fact it doesn't
need to be anything more than a cables or ribbons system, hold in
tension by the spinning itself. To make a concept example, rather than
a bicycle wheel you can have a "bolas" design.
Because you concentrate all the pressurized volume in two points only
instead of distributing along the entire circumference you can have a
much larger radius (easily ten times larger) for the same mass/cost.
Seems much more efficient? Maybe there is some technical reason why
this is not possible but then please explain it to me! :)
Cheers,
Claudio
--- In ssi_list@... "victoriatangoman"
# 19712 byvictoriatangoman on April 4, 2004, 9:07 a.m.
Member since 2022-08-22
> Between each layer of seals use vacuum pumps to minimise any
> leakage to space. Vacuum pumps are capable of reducing the
> remaining leakage down to countable molecules if you really want
> that.
of failure if the vacuum pumps and their back-ups fail through some
type of localized catastrophe.
I'm thinking passive pressurization, rather than active
pressurization, presents a safer baseline.
If you were a ship designer, what benefits would you gain by
offering this type of active pressurization. I would think that
there would be a mass savings by avoiding the need to enclose the
centrefuges within a unitary pressure shell. What other benefits
would be worth making this trade-off?
TangoMan
# 19713 byvictoriatangoman on April 4, 2004, 9:13 a.m.
Member since 2022-08-22
--- In ssi_list@... "sheikyurdices"
> points, the center and the rotating end one, and the further apart
> they are the better it is. What need there is to have a continuous
> closed circumference? Why not just spin a very short section at the
> end of a much longer radial arm, eventually with a second one as a
> counterbalance at the other end, if needed?
From my vast library of space images I conjure the following:
=Rotating+Arm+Ship.jpg&.view=t&.done=http%
26.view=t
Or look in the PHOTOS section of the website for "Rotating Arm Ship."
Is this what you mean?
TangoMan
# 19714 byMitchell James on April 4, 2004, 11:15 a.m.
Member since 2022-08-22
Much better. Add your counter rotating spokes and reduce the spindle
mass. The ship is controlled from living quarters in the rotating arms
and doesn't need anything that looks like a crew compartment on the
spindle. Reaction mass, some power generators, storage are the only
things on spindle.
Mitchell James
# 19715 byIan Woollard on April 4, 2004, 11:35 a.m.
Member since 2022-08-22
>
> > Between each layer of seals use vacuum pumps to minimise any
> > leakage to space. Vacuum pumps are capable of reducing the
> > remaining leakage down to countable molecules if you really want
> > that.
>
> Do you think that this type of arrangement inserts a critical point
> of failure if the vacuum pumps and their back-ups fail through some
> type of localized catastrophe.
either side.
Otherwise; pump failure isn't at all a catastrophe. As I noted, the
natural rate of leakage, provided you use reasonable seals, is really
rather low; perhaps a few cubic feet of air per hour. The gap only needs
to be a few thousandth of an inch.
The pumps are just there to scavenge the atmosphere you would otherwise
have lost to space; atmosphere is expensive.
# 19716 byClaudio on April 4, 2004, 12:01 p.m.
Member since 2022-08-22
yup, sort of, you can loose all the front and back really, seems just
redundant zero-g space. You can have a docking facility in front of the hub,
and engines in the back, but in proportion of the whole structure would be a
tenth of what's depicted there...
Still, the whole thing is just good for experimental or research vessels.
Any ship with a decent engine will have is max speed limited by the
acceleration the crew could stand, so artificial gravity would really be the
least of the things you would design your ship around IMHO.
First of all trash all the horizontal designs, StarWars/Startreck type of
things, that's just a Hollywood convention to make things more familiar to
the audience. Any reasonable ship designed according to law of physics will
be arranged top>down, not rotating and even less left>right, because the
acceleration will make the bottom the part oriented opposite the direction
of travel, not perpendicular to it. To maximise speed in a voyage you'll be
accelerating at ~1G constantly to half way, then shut the engines, spin the
ship 180 and spend the other half of the voyage decelerating back at the
same rate. All the time your feet will be solidly stuck to the floor by the
acceleration, except for a few minutes of zero-g midtravel while you spin
the ship. That's because that is the max speed you can go regardless the
efficiency of your engines. We already have engines that can accelerate
faster than that, so going slower is not really an issue... Given the very
minimal acceleration represented by 1G, rotating gizmos are only necessary
for ships that go so slow as to be pretty much useless for space distances
anyway. I don't have the math on hand but even at a constant acceleration
and deceleration of 1G would take months just to get to Mars IIRC... slower
than that, don't bother really... :)
It's more likely that ship's crew will be trained (if not actually
genetically enhanced) to stand accelerations of 2, 3G or even more for the
duration of the entire voyage. As a matter of fact it's likely that a whole
race of space traders will gradually adapt at living in high G environments
even without genetically manipulation, just getting used to it from birth
will already make a big difference...
If ships will be designed with artificial gravity as a main concern, that
will be to dampen acceleration effects, not generating anymore!
Cheers,
Claudio
# 19717 byEd Minchau on April 4, 2004, 1:23 p.m.
Member since 2022-08-22
> I don't have the math on hand but even at a constant acceleration
> and deceleration of 1G would take months just to get to Mars
IIRC... slower
> than that, don't bother really... :)
(aug 27/03: 55746199000 m), then starting from earth orbit 100 km up
(initial velocity is earth's orbital velocity around the sun plus
orbital velocity at 100km orbit: total of 37605m/s) and finishing at
mars orbit 100 km up (final velocity is mars' orbital velocity
around sun plus orbital velocity at 100 km orbit: total of 27598
m/s), with acceleration and deceleration at 1 gee and negligible
turnaround time in the middle... total trip time would be just over
28.5 hours. Peak velocity (at turnaround) would be 537 km/s.
One would need a very high ISP to maintain 1 gee thrust for just
over a day like that, but man oh man, talk about Mars Direct.
Ed
# 19718 byvictoriatangoman on April 4, 2004, 1:45 p.m.
Member since 2022-08-22
--- In ssi_list@... "Ed Minchau"
> > I don't have the math on hand but even at a constant acceleration
> > and deceleration of 1G would take months just to get to Mars
> IIRC... slower
> > than that, don't bother really... :)
>
> By my calculations: if Mars and Earth are at their minimum
distance
> (aug 27/03: 55746199000 m), then starting from earth orbit 100 km
up
> (initial velocity is earth's orbital velocity around the sun plus
> orbital velocity at 100km orbit: total of 37605m/s) and finishing
at
> mars orbit 100 km up (final velocity is mars' orbital velocity
> around sun plus orbital velocity at 100 km orbit: total of 27598
> m/s), with acceleration and deceleration at 1 gee and negligible
> turnaround time in the middle... total trip time would be just
over
> 28.5 hours. Peak velocity (at turnaround) would be 537 km/s.
>
> One would need a very high ISP to maintain 1 gee thrust for just
> over a day like that, but man oh man, talk about Mars Direct.
>
> Ed
Very interesting. Do you have any idea what the payload proportion
would be? I'd imagine using the rocket equation, that the amount of
reaction mass that you'd have to carry to sustain an engine burn, be
it chemical, nuclear, or solar powered, of 28.5 hours would be
immense.
That's why I don't buy into the stacked ship arrangement because
counting on acceleration to provide a sense of gravity would be
impracticle. Unless, we're talking Bussard Intersteller Ramjet.
I'd think that this ship would be immense and there'd only be a
small crew capsule stuck on it somewhere.
TangoMan
# 19719 byAsteroza on April 4, 2004, 5:02 p.m.
Member since 2022-08-22
>For all you engineers. If we want a spaceship with a rotating torus
>section how do we mate it with a non-rotating spindle?
>
>WHat would the structural problems be? How would you insure pressure
>worthiness?
>
>Obviously, the rotating section can be encased within a pressure
>vessel, like Discovery from 2001:A Space Odyssy. Is this optimum?
>
>Any thoughts?
>
>TangoMan
design that incorporates a hard rotating arm/spoke with a pendulum like
section hanging off the end (allowing fore and aft motion) would accomodate
the crew/passengers better. Unfortunately, such a design doesn't lend
itself well to encapsulation in an exterior pressure hull due to waste of
volume. Additionally, it won't have a full gravity environment due to the
economics and mechanics of such a configuration, nor does it lend itself
well to having a counter-rotating section. That said, it is arguably the
most elegant solution for a ship that has variable acceleration profiles
due to journey choices and cargo manifests. One arguably bizzare variation
is to have the rotating arms on fore/aft hinges at the hub, and a variable
circumference torus (sweeping out a cone shape while under ship
acceleration, and a wheel shape when the ship is not accelerating)
Other choices being a rotating torus with only a transfer cab system up and
down its radius to a non-rotating hub, or a non-rotating torus pressure
hull with a contained rotating section with a contained transfer cab in the
torus for transitioning to zero-g (with either a pressurized arm/spoke or a
zero-g transfer cab to the hub).
Fundamentally it is a tradeoff between the convienance of a rotating seal
for continuous use with the associated maintenance headaches and the great
forces and stresses involved at the hub, versus a transfer cab system with
a heavily used airlock seal and the maintenance associated with what
amounts to a separate spacecraft.
The full sphere pressure hull method isn't terrible, since you could have
counter-rotating hemispheres or any lesser shape, but to get to full
gravity would require an inordinately large pressurized volume. Having a
"hollow center" fiilled with non-rotating spaces for crew and cargo would
deal with the inconvienant low gravity sections. To justify such a large
pressurized volume however would mean the transport of large quantities of
manufactured goods, as most bulk goods could be carried externally in
tanks, and the remaining other types of cargo that can survive vacuum would
also be externally carried. Such a vehicle is only good for doing "tramp
steamer" cargo services to isolated and non-self sufficient ports of call
and delivery of initial machinery to soon-to-be self supporting facilities.
Additionally, it does not lend itself well to higher acceleration profiles
for the ship as the decks can not rotate to accomodate the changes in
acceleration vector, thus dooming the ship to long flight durations. Thus
such a ship would be in essence required to be a very large cargo carrier
of the "slow boat" variety, unless it is intended to be a mobile
construction shack in which case it carries all the materials for
constructing new facilities, then moves on to the next jobsite after
picking up new construction materials.
Asteroza
# 19720 byClaudio on April 4, 2004, 5:53 p.m.
Member since 2022-08-22
ok maybe wasn't mars... Jupiter? :)
If the engine is nuclear and burns some heavy gas fuel heating it to plasma
temperatures the mass required shouldn't be extreme at all... solar or
chemical don't even bother to do the math, but a nuclear plasma jet engine
should be able to deliver that sort of acceleration... thinking mostly out
of comparison with smaller systems, so maybe just talking straight out my
wrong end though...
Claudio
# 19721 byBill on April 4, 2004, 6:33 p.m.
Member since 2022-08-22
This in an interesting thread.
Earth without a problem. The basic method is to have very well
machined parts that fit togther closely. Imagine three cylinders two
the same radius and the third slightly larger so that the two can fit
into it. The two smaller ones fit into each end of the bigger one. The
two can then be clamped together internally so they don't rotate
relative to each other. the middle section can now rotate freely.
When engineering the three sections, a 'small' lip can be added so
that the three sections don't move relative to each other.
Such an arrangement will leak, but the leakage will be very small.
Adding heavy oil as libricant can decrease the leakage further but
never stop it entirely. Structurally the arrangement will not buckle
so catastrophic pressure release is improbable.
On design:
I would suggest two living volumes similar to apartment buildings held
together with a smaller 'tube' connected to the middle section of the
cylinders above perpendicularly. It would look like a large barbell
spinning around its access.
I envision a space ship to look like a large sperm (spherical head
with a long mass driver type engine attached to it) with one or more
of these barbell sections. Most likely one or more solar power
stations attached to the mass driver. The 'fuel' would be large chunks
of material strapped on to the mass driver. As it is needed, it is
brought into the spherical section pulverized into dust and used.
Cargo containers (agricultural sections ?) would be strapped on the
same way as the fuel.
On Counter rotation.
You will need something to counter-rotate. If it isn't another living
area, its going to be one big gyroscope.
Bill
--- In ssi_list@... "victoriatangoman"
# 19722 byBill on April 4, 2004, 6:48 p.m.
Member since 2022-08-22
I think any reasonable continuous accelerating engine will be very low
acceleration. Tops 0.01 gravities.
The second obvious one is an ion engine. There are other designs I can
think of. I doubt nuclear is going to be an option used. i think it
will be a solar powered electrical engine that accelerates reaction mass.
Bill
> ok maybe wasn't mars... Jupiter? :)
> If the engine is nuclear and burns some heavy gas fuel heating it to
plasma
> temperatures the mass required shouldn't be extreme at all... solar or
> chemical don't even bother to do the math, but a nuclear plasma jet
engine
> should be able to deliver that sort of acceleration... thinking
mostly out
> of comparison with smaller systems, so maybe just talking straight
out my
# 19723 byEd Minchau on April 4, 2004, 7:17 p.m.
Member since 2022-08-22
> ok maybe wasn't mars... Jupiter? :)
gee for several months, then one attains a significant fraction of
light speed.
> If the engine is nuclear and burns some heavy gas fuel heating it
to plasma
> temperatures the mass required shouldn't be extreme at all...
solar or
> chemical don't even bother to do the math,
heh... someone _always_ does the math...
> > Ed, Thanks, I was going to sit down and calculate the same thing.
> > Very interesting. Do you have any idea what the payload
proportion
> > would be? I'd imagine using the rocket equation, that the amount
of
> > reaction mass that you'd have to carry to sustain an engine
burn, be
> > it chemical, nuclear, or solar powered, of 28.5 hours would be
> > immense.
I made one major assumption in the calculation that must be noted: I
assumed no turnaround time. Such a ship would need some turnaround
time though, during which time it would coast at top speed. The
longer the turnaround time, the less fuel is needed, and the lower
the top speed; also, the total trip would take longer. Consider
that 28.5 hours as a lower bound for any trip to Mars at one gee
acceleration.
More numbers: the trip would start at earth's orbital speed around
the sun (29747 m/s) plus the orbital velocity of the craft 100 km
above the earth (7858 m/s)=37605m/s; acceleration for 50912 seconds
(about 14 hours 9 minutes) would bring the craft to 537048m/s; delta
vee is 50912*9.81=499443...deceleration to match mars orbital speed
and to be in mars orbit (down to 27598 m/s) takes 51932 seconds
(14h26m) and the delta vee is 509450.
Assume that 1/4 of the propellant is used on the first leg of the
trip, accelerating at 1 gee, and that another 1/4 of the fuel is
used for the second leg of the trip, decelerating on approach to
Mars. That way, half the propellant remains for the return trip to
earth, more than enough. If propellant makes up 90% of the ship
mass, then the total mass used:
M(e)=empty mass of ship
M(p)=total propellant mass
M(f)=fully fuelled mass=M(e)+M(p)*M(e)
mass after 1/4 propellant is gone: M(p)=9*M(e) so M(p)/4=2.25*M(e)
so mass after first leg=M(1)*M(e)-2.25*M(e)=7.75*M(e)
deltaVee=Vexhaust*ln(M(f)/M(1))
499443=Vexhaust*ln(10/7.75)
Vexhaust59km/s
Isp=Vexhaust/g59428/9.819738s
So if 90% of the ship is propellant, this course requires an Isp of
almost 200000s and an exhaust velocity of almost 2000km/s, nearly 1%
of c. That would need one hell of an engine; consider that the
space shuttle main engines have an Isp of 450s.
Of course, if there is a turnaround time of minutes or hours or even
days, the fuel requirements are significantly lower. There are
plenty of other numbers to play around with in the equations.
Ed
# 19724 byValens Agnitio on April 4, 2004, 11:55 p.m.
Member since 2022-08-22
I like this idea. Perhaps a teardrop shaped, multilevel container at each
end, insted of arc segments... Just another idea. Perhaps, in order to
minimize surface area, the containers could be spherical. If I follow
Claudio's idea, the radial arms could be long enough that the 'gravity
difference between each level in the containers would be unnoticable.
>Date: Sun, 04 Apr 2004 14:00:46 -0000
>
>posted this a couple of days ago but doesn't seem to get there, so I
>think I'll repost it, apologies if you get it twice...
>
>I'm no engineer but I always thought the rotating torus design is
>fundamentally flawed... ;)
>The problem is not the "rotating" bit, is the torus. Why a whole torus?
>The main issue I see is that in this design the entire circumference
>that rotates is pressurised, and then the entire contraption needs to
>spin very fast indeed to get any simulated gravity at all, being
>necessarily of a small radius, while all you really want are the two
>points, the center and the rotating end one, and the further apart
>they are the better it is. What need there is to have a continuous
>closed circumference? Why not just spin a very short section at the
>end of a much longer radial arm, eventually with a second one as a
>counterbalance at the other end, if needed?
>Basically take your "wheel" design and multiply the radius by say a
>factor of four or more, then saw off all but two very small sections
>at the opposite ends of the wheel. What you are left with is a system
>that spins much faster at the circumference end (where you want to
>have the artificial gravity) but much slower at the hub, where you
>have the bearings.
>The rotating parts needs not be pressurized at all, making the
>construction and maintenance that much simpler, as all you need is a
>pressurized cab moving between the pressurized section at the hub and
>the pressurized section at the far end(s) of the arm. The "arm" (or
>arms) itself doesn't need to be pressurized and in fact it doesn't
>need to be anything more than a cables or ribbons system, hold in
>tension by the spinning itself. To make a concept example, rather than
>a bicycle wheel you can have a "bolas" design.
>Because you concentrate all the pressurized volume in two points only
>instead of distributing along the entire circumference you can have a
>much larger radius (easily ten times larger) for the same mass/cost.
>Seems much more efficient? Maybe there is some technical reason why
>this is not possible but then please explain it to me! :)
>
>Cheers,
>
>Claudio
>
>--- In ssi_list@... "victoriatangoman"
> > > The picture therefore seems to be showing a vehicle therefore
> > > rather than a space colony.
> >
> > Sorry for the confusion, yes, I'm referring to spaceship design.
> >
> > > The best vehicle design would of course be the one with the least
> > > surface area that would require radiation shielding and therefore
> > > the least mass and least energy required per change in velocity.
> >
> > Which would be a sphere, correct?
> >
> > What I liked about this ship from the movie RED PLANET, was the
> > counter-rotating rings. Each would counter the angular momentum of
> > the other. Is this correct?
> >
> > If there was only one ring, how would the angular momentum be
> > accomodated?
> >
> > Here are some quick calculations:
> >
> > If we want a 1.0 gravity environment:
> >
> > With 6 rotations per minute the radius of the ring = 86 m
> > With 5 rotations per minute the radius of the ring = 97 m
> > With 4 rotations per minute the radius of the ring = 117 m
> > With 3 rotations per minute the radius of the ring = 160 m
> >
> > If we want a 0.75 gravity environment:
> >
> > With 6 rotations per minute the radius of the ring = 80 m
> > With 5 rotations per minute the radius of the ring = 88 m
> > With 4 rotations per minute the radius of the ring = 103 m
> > With 3 rotations per minute the radius of the ring = 136 m
> >
> > If we want a 0.66 gravity environment:
> >
> > With 6 rotations per minute the radius of the ring = 77 m
> > With 5 rotations per minute the radius of the ring = 85 m
> > With 4 rotations per minute the radius of the ring = 98 m
> > With 3 rotations per minute the radius of the ring = 127 m
> >
> > If we want a 0.5 gravity environment:
> >
> > With 6 rotations per minute the radius of the ring = 73 m
> > With 5 rotations per minute the radius of the ring = 79 m
> > With 4 rotations per minute the radius of the ring = 89 m
> > With 3 rotations per minute the radius of the ring = 111 m
> >
> > If we want a 0.33 gravity environment:
> >
> > With 6 rotations per minute the radius of the ring = 69 m
> > With 5 rotations per minute the radius of the ring = 73 m
> > With 4 rotations per minute the radius of the ring = 79 m
> > With 3 rotations per minute the radius of the ring = 94 m
> >
> > If we want a 0.25 gravity environment:
> >
> > With 6 rotations per minute the radius of the ring = 67 m
> > With 5 rotations per minute the radius of the ring = 70 m
> > With 4 rotations per minute the radius of the ring = 75 m
> > With 3 rotations per minute the radius of the ring = 86 m
> >
> > OK, is it a good idea to have counter-rotating rings? I'm assuming
> > it is.
> >
> > If that is what is desired, then I fall back to the design of the
> > Discovery in 2001:A Space Odyssey. Put the centerfuges inside the
> > shell of the sphere. This eliminates the pressure seal issue for the
> > outer shell becomes the unitary pressure vessel.
> >
> > Place the two counter rotating centerfuges next to each other at the
> > center of the spherical shell. All of the volume outside the two
> > narrow centerfuges becomes zero-gravity crew quarters and storage.
> >
> > If you look at the numbers above you'll see that if the crew can
> > survive sustained exposure to 6 rpm then the radius difference
> > between the different gravity simulation levels drops in smaller
> > increments than at lower rpms.
> >
> > I know from the Stanford Torus study that they recommended a
> > rotation rate of less than 3 rpm so that a broad range of people
> > could accomodate themselves to living within the Habitat.
> >
> > However, a spaceship doesn't have to have those design constraints,
> > and we could select a crew that can adjust to a higher rpm rate.
> > Does anyone have any information on how high rpm rates can go and
> > how long they can be sustained so that the crew can live normally.
> >
> > Lastly, consider the volume of the sphere that could be used for
> > other purposes. If it is too much space, then perhaps we could
> > design a disk shaped ship within which to place the centerfuges but
> > now we're faced with the prospect of flat surfaces and corner joints
> > within the pressure vessel design. How problematic are they?
> >
> > Any thoughts?
> >
> > TangoMan
>
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# 19725 byBill on April 5, 2004, 9:26 a.m.
Member since 2022-08-22
A ten storey cylindrical building at each end is probably the easiest
thing to design and build. The amount of extra sheilding needed
relative to a sphere with the same volume is about one third, but a
cylinder has more useable internal area than a sphere. If you put it
at the end of a 200 meter arm the difference between the bottom and
the top floor is not too bad.
need it. Think of what would be easy to build and maintain. Weight is
an important factor, but its not the first thing that should come to
you mind.
Bill
--- In ssi_list@... "Valens Agnitio"
> I like this idea. Perhaps a teardrop shaped, multilevel container at
each
> end, insted of arc segments... Just another idea. Perhaps, in order to
> minimize surface area, the containers could be spherical. If I follow
> Claudio's idea, the radial arms could be long enough that the 'gravity
> difference between each level in the containers would be unnoticable.
>
> Val
>
> >Date: Sun, 04 Apr 2004 14:00:46 -0000
> >
> >posted this a couple of days ago but doesn't seem to get there, so I
> >think I'll repost it, apologies if you get it twice...
> >
> >I'm no engineer but I always thought the rotating torus design is
> >fundamentally flawed... ;)
> >The problem is not the "rotating" bit, is the torus. Why a whole torus?
> >The main issue I see is that in this design the entire circumference
> >that rotates is pressurised, and then the entire contraption needs to
> >spin very fast indeed to get any simulated gravity at all, being
> >necessarily of a small radius, while all you really want are the two
> >points, the center and the rotating end one, and the further apart
> >they are the better it is. What need there is to have a continuous
> >closed circumference? Why not just spin a very short section at the
> >end of a much longer radial arm, eventually with a second one as a
> >counterbalance at the other end, if needed?
> >Basically take your "wheel" design and multiply the radius by say a
> >factor of four or more, then saw off all but two very small sections
> >at the opposite ends of the wheel. What you are left with is a system
> >that spins much faster at the circumference end (where you want to
> >have the artificial gravity) but much slower at the hub, where you
> >have the bearings.
> >The rotating parts needs not be pressurized at all, making the
> >construction and maintenance that much simpler, as all you need is a
> >pressurized cab moving between the pressurized section at the hub and
> >the pressurized section at the far end(s) of the arm. The "arm" (or
> >arms) itself doesn't need to be pressurized and in fact it doesn't
> >need to be anything more than a cables or ribbons system, hold in
> >tension by the spinning itself. To make a concept example, rather than
> >a bicycle wheel you can have a "bolas" design.
> >Because you concentrate all the pressurized volume in two points only
> >instead of distributing along the entire circumference you can have a
> >much larger radius (easily ten times larger) for the same mass/cost.
> >Seems much more efficient? Maybe there is some technical reason why
> >this is not possible but then please explain it to me! :)
> >
> >Cheers,
> >
> >Claudio
> >
> >--- In ssi_list@... "victoriatangoman"
> > > --- In ssi_list@... Mitchell James
> > > > The picture therefore seems to be showing a vehicle therefore
> > > > rather than a space colony.
> > >
> > > Sorry for the confusion, yes, I'm referring to spaceship design.
> > >
> > > > The best vehicle design would of course be the one with the least
> > > > surface area that would require radiation shielding and therefore
> > > > the least mass and least energy required per change in velocity.
> > >
> > > Which would be a sphere, correct?
> > >
> > > What I liked about this ship from the movie RED PLANET, was the
> > > counter-rotating rings. Each would counter the angular momentum of
> > > the other. Is this correct?
> > >
> > > If there was only one ring, how would the angular momentum be
> > > accomodated?
> > >
> > > Here are some quick calculations:
> > >
> > > If we want a 1.0 gravity environment:
> > >
> > > With 6 rotations per minute the radius of the ring = 86 m
> > > With 5 rotations per minute the radius of the ring = 97 m
> > > With 4 rotations per minute the radius of the ring = 117 m
> > > With 3 rotations per minute the radius of the ring = 160 m
> > >
> > > If we want a 0.75 gravity environment:
> > >
> > > With 6 rotations per minute the radius of the ring = 80 m
> > > With 5 rotations per minute the radius of the ring = 88 m
> > > With 4 rotations per minute the radius of the ring = 103 m
> > > With 3 rotations per minute the radius of the ring = 136 m
> > >
> > > If we want a 0.66 gravity environment:
> > >
> > > With 6 rotations per minute the radius of the ring = 77 m
> > > With 5 rotations per minute the radius of the ring = 85 m
> > > With 4 rotations per minute the radius of the ring = 98 m
> > > With 3 rotations per minute the radius of the ring = 127 m
> > >
> > > If we want a 0.5 gravity environment:
> > >
> > > With 6 rotations per minute the radius of the ring = 73 m
> > > With 5 rotations per minute the radius of the ring = 79 m
> > > With 4 rotations per minute the radius of the ring = 89 m
> > > With 3 rotations per minute the radius of the ring = 111 m
> > >
> > > If we want a 0.33 gravity environment:
> > >
> > > With 6 rotations per minute the radius of the ring = 69 m
> > > With 5 rotations per minute the radius of the ring = 73 m
> > > With 4 rotations per minute the radius of the ring = 79 m
> > > With 3 rotations per minute the radius of the ring = 94 m
> > >
> > > If we want a 0.25 gravity environment:
> > >
> > > With 6 rotations per minute the radius of the ring = 67 m
> > > With 5 rotations per minute the radius of the ring = 70 m
> > > With 4 rotations per minute the radius of the ring = 75 m
> > > With 3 rotations per minute the radius of the ring = 86 m
> > >
> > > OK, is it a good idea to have counter-rotating rings? I'm assuming
> > > it is.
> > >
> > > If that is what is desired, then I fall back to the design of the
> > > Discovery in 2001:A Space Odyssey. Put the centerfuges inside the
> > > shell of the sphere. This eliminates the pressure seal issue for the
> > > outer shell becomes the unitary pressure vessel.
> > >
> > > Place the two counter rotating centerfuges next to each other at the
> > > center of the spherical shell. All of the volume outside the two
> > > narrow centerfuges becomes zero-gravity crew quarters and storage.
> > >
> > > If you look at the numbers above you'll see that if the crew can
> > > survive sustained exposure to 6 rpm then the radius difference
> > > between the different gravity simulation levels drops in smaller
> > > increments than at lower rpms.
> > >
> > > I know from the Stanford Torus study that they recommended a
> > > rotation rate of less than 3 rpm so that a broad range of people
> > > could accomodate themselves to living within the Habitat.
> > >
> > > However, a spaceship doesn't have to have those design constraints,
> > > and we could select a crew that can adjust to a higher rpm rate.
> > > Does anyone have any information on how high rpm rates can go and
> > > how long they can be sustained so that the crew can live normally.
> > >
> > > Lastly, consider the volume of the sphere that could be used for
> > > other purposes. If it is too much space, then perhaps we could
> > > design a disk shaped ship within which to place the centerfuges but
> > > now we're faced with the prospect of flat surfaces and corner joints
> > > within the pressure vessel design. How problematic are they?
> > >
> > > Any thoughts?
> > >
> > > TangoMan
> >
> Tax headache? MSN Money provides relief with tax tips, tools, IRS
forms and
# 19726 byvictoriatangoman on April 5, 2004, 10:17 a.m.
Member since 2022-08-22
>
> A ten storey cylindrical building at each end is probably the
> easiest thing to design and build. The amount of extra sheilding
> needed relative to a sphere with the same volume is about one
> third, but a cylinder has more useable internal area than a
> sphere.
floors, then where does the *more usable internal area* for a
cylinder come from?
> Everyone should stop thinking in aerodynamic shapes. Space doesn't
> need it. Think of what would be easy to build and maintain.
I've been following this thread and I don't recall anyone proposing
aerodynamic shapes. Can you direct me to the message where someone
did make such a reference?
> Weight is an important factor, but it's not the first thing that
> should come to you mind.
Why not? The more massive the spaceship, the more fuel that it will
have to carry, all else being equal. The fact that they now have to
carry more fuel to propell the ship also means that they have to
carry more fuel to carry that extra fuel, see rocket equation.
TangoMan
# 19727 byBill on April 5, 2004, 12:38 p.m.
Member since 2022-08-22
>
> > Everyone should stop thinking in aerodynamic shapes. Space doesn't
> > need it. Think of what would be easy to build and maintain.
>
> I've been following this thread and I don't recall anyone proposing
> aerodynamic shapes. Can you direct me to the message where someone
> did make such a reference?
for the shape of the living areas, the nose and aft of the ship. In
fact I was specifically ranting about the teardrop design proposed. I
saw no benefit in the shape other than its aerodynamic.
>
> > Weight is an important factor, but it's not the first thing that
> > should come to you mind.
>
> Why not? The more massive the spaceship, the more fuel that it will
> have to carry, all else being equal. The fact that they now have to
> carry more fuel to propell the ship also means that they have to
> carry more fuel to carry that extra fuel, see rocket equation.
>
No, the ship will move slower, and take longer to get to its
destination. And this is an acceptable tradeoff if the simpler designs
make it easier and faster to build the ship.
If you design the ship to be manufactured quickly in space, the time
and cost savings in building the ship will more than offset any
transit time.
A ship such as we propose will take a decade to build. If we shave
three years from construction and add two years to the trip you are
still ahead.
# 19728 byValens Agnitio on April 6, 2004, 11:10 p.m.
Member since 2022-08-22
If you have ever been in a dome house, the wasted space becomes apparent
near the edges. There the curvature makes it to short for ergonomic sitting
or standing, and most furniture and utitlities that are designed for easy
human use are verticaly constructed and again, can't get all the way to the
edge. However, I think that fluid storage could make use of these areas
quite nicely in a space habitat, while providing shielding (as I recall,
TangoMan, you are quite fond of water shielding). There are probably
numerous other things that can also be fit into this 'wasted' space, such as
electronics, air cylinders, etc... So, in terms of space habitat, I'd have
to say that a cylinder with ten levels makes much more sense than a
cylinder. Here's two important reasons why:
2) much more efficient for heat conservation
This last may not be relevant, but I just don't know the dynamics of
equipment heat, plus sun, and how that relates to the inside temperature. At
any rate, it seems obvious that spheres will be the shape of choice for
compact human habitats and ship design.
Val
>Date: Mon, 05 Apr 2004 15:17:06 -0000
>
> > A ten storey cylindrical building at each end is probably the
> > easiest thing to design and build. The amount of extra sheilding
> > needed relative to a sphere with the same volume is about one
> > third, but a cylinder has more useable internal area than a
> > sphere.
>
>HUH? If you have a sphere with 10 floors and a cylinder with 10
>floors, then where does the *more usable internal area* for a
>cylinder come from?
>
> > Everyone should stop thinking in aerodynamic shapes. Space doesn't
> > need it. Think of what would be easy to build and maintain.
>
>I've been following this thread and I don't recall anyone proposing
>aerodynamic shapes. Can you direct me to the message where someone
>did make such a reference?
>
> > Weight is an important factor, but it's not the first thing that
> > should come to you mind.
>
>Why not? The more massive the spaceship, the more fuel that it will
>have to carry, all else being equal. The fact that they now have to
>carry more fuel to propell the ship also means that they have to
>carry more fuel to carry that extra fuel, see rocket equation.
>
>TangoMan
>
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# 19729 byEd Minchau on April 6, 2004, 11:40 p.m.
Member since 2022-08-22
--- In ssi_list@... "Valens Agnitio"
> to say that a cylinder with ten levels makes much more sense than
a
> cylinder.
?