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Ceres water rich?

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Hop David

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Sep 9, 2005, 5:17:34 PM9/9/05
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http://msnbc.msn.com/id/9247925/

There's some speculation that Ceres has lots of water.

At 2.77 AU it's about in the middle of the Main Belt.

I'd imagine that objects in the outer main belt and the Trojans would be
even more likely to be water rich.

--
Hop David
http://clowder.net/hop/index.html

Michael Rhino

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Sep 12, 2005, 1:30:29 AM9/12/05
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"Hop David" <hopspageHA...@tabletoptelephone.com> wrote in message
news:4321FBEE...@tabletoptelephone.com...

> http://msnbc.msn.com/id/9247925/
>
> There's some speculation that Ceres has lots of water.
>
> At 2.77 AU it's about in the middle of the Main Belt.

This means that Ceres could be a viable place to colonize. It is going to
take a while for our space population to reach 1 million people, so Ceres is
large enough for our short term needs. The main export would be to O'Neill
colonies. It takes less energy to launch something from Ceres than from the
moon, Mars, or Earth.


Mike Combs

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Sep 12, 2005, 1:39:59 PM9/12/05
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"Michael Rhino" <news...@alexanderpics.com> wrote in message
news:Vn8Ve.5558$Gh....@tornado.socal.rr.com...

Yes, but are the habitats in cislunar space, or elsewhere? If in cislunar
space, you have consider the total delta-V from the Belt to HEO. As I
recall from "The High Frontier", O'Neill had calculated that the delta-V for
importing from the Belt would just about equal that from the Earth's
surface, although he was willing to allow that the requirements for
high-thrust drives and aeroshells in the case of Earth would probably tip
the balance in favor of the Belt, costwise. On the other hand, time is
money.

But later, the comparison became moot when it was realized that there was a
wide variety of asteroids in near Earth orbits. Even assuming the space
colonization process begins in cislunar space (most likely, in my view),
these NEOs can help us get well past that 1 million people mark you
mentioned. I would tend to think of the resources of Ceres as being for a
much-later-generation settlement push within the Belt itself.

--


Regards,
Mike Combs
----------------------------------------------------------------------
Member of the National Non-sequitur Society. We may not make
much sense, but we do like pizza.


Hop David

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Sep 12, 2005, 2:02:18 PM9/12/05
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Mike Combs wrote:
> "Michael Rhino" <news...@alexanderpics.com> wrote in message
> news:Vn8Ve.5558$Gh....@tornado.socal.rr.com...
>
>>"Hop David" <hopspageHA...@tabletoptelephone.com> wrote in message
>>news:4321FBEE...@tabletoptelephone.com...
>>
>>>http://msnbc.msn.com/id/9247925/
>>>
>>>There's some speculation that Ceres has lots of water.
>>>
>>>At 2.77 AU it's about in the middle of the Main Belt.
>>
>>This means that Ceres could be a viable place to colonize. It is going to
>>take a while for our space population to reach 1 million people, so Ceres
>
> is
>
>>large enough for our short term needs. The main export would be to
>
> O'Neill
>
>>colonies. It takes less energy to launch something from Ceres than from
>
> the
>
>>moon, Mars, or Earth.
>
>
> Yes, but are the habitats in cislunar space, or elsewhere? If in cislunar
> space, you have consider the total delta-V from the Belt to HEO. As I
> recall from "The High Frontier", O'Neill had calculated that the delta-V for
> importing from the Belt would just about equal that from the Earth's
> surface, although he was willing to allow that the requirements for
> high-thrust drives and aeroshells in the case of Earth would probably tip
> the balance in favor of the Belt, costwise. On the other hand, time is
> money.

I get 10.3 km/sec delta vee to park Ceres cargo at an Earth/Moon L4 or
L5 point. (ordinary chemical rockets, Hohmann transfer orbit). Trip time
is 1.3 years

>
> But later, the comparison became moot when it was realized that there was a
> wide variety of asteroids in near Earth orbits. Even assuming the space
> colonization process begins in cislunar space (most likely, in my view),
> these NEOs can help us get well past that 1 million people mark you
> mentioned. I would tend to think of the resources of Ceres as being for a
> much-later-generation settlement push within the Belt itself.

I agree. NEOs, the moon, Phobos & Deimos are the best bet for building
cislunar infrastructure.

But I believe watery bodies will be helpful in building the main belt
when that time comes.

James Nicoll

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Sep 12, 2005, 2:17:20 PM9/12/05
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In article <4325C2A...@tabletoptelephone.com>,

Hop David <hopspageHA...@tabletoptelephone.com> wrote:
>
>I get 10.3 km/sec delta vee to park Ceres cargo at an Earth/Moon L4 or
>L5 point. (ordinary chemical rockets, Hohmann transfer orbit). Trip time
>is 1.3 years
>
Hmmm. Ceres's day is about 9 hours. 10 km/s x 9 hrs x 3600 s
is 324,000 km, and if that is the circumference of a circle, r is
about 52,000 km. Think we can build a 52,000 km tether on Ceres?

A would be less than 2 m/s/s.

Alternatively, we could just use a smaller r and a much
shorter period of revolution.


--
http://www.cic.gc.ca/english/immigrate/
http://www.livejournal.com/users/james_nicoll

Mike Combs

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Sep 13, 2005, 1:10:17 PM9/13/05
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"James Nicoll" <jdni...@panix.com> wrote in message
news:dg4gng$25a$1...@reader1.panix.com...

> >
> Hmmm. Ceres's day is about 9 hours. 10 km/s x 9 hrs x 3600 s
> is 324,000 km, and if that is the circumference of a circle, r is
> about 52,000 km. Think we can build a 52,000 km tether on Ceres?

At that scale, I can't help but wonder if it wouldn't be cheaper to build an
EM accelerator all the way around the asteroid. One could launch cargo and
in so doing either be speeding up or slowing down the rotation rate,
depending on your preference. Large volumes of launches would minutely
affect the orbit of Ceres, but it would be affected much less than many
smaller asteroids.

James Nicoll

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Sep 13, 2005, 2:31:10 PM9/13/05
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In article <dg715p$f7t$1...@home.itg.ti.com>,

Mike Combs <mike...@nospam.com_chg_nospam_2_ti> wrote:
>"James Nicoll" <jdni...@panix.com> wrote in message
>news:dg4gng$25a$1...@reader1.panix.com...
>> >
>> Hmmm. Ceres's day is about 9 hours. 10 km/s x 9 hrs x 3600 s
>> is 324,000 km, and if that is the circumference of a circle, r is
>> about 52,000 km. Think we can build a 52,000 km tether on Ceres?
>
>At that scale, I can't help but wonder if it wouldn't be cheaper to build an
>EM accelerator all the way around the asteroid. One could launch cargo and
>in so doing either be speeding up or slowing down the rotation rate,
>depending on your preference. Large volumes of launches would minutely
>affect the orbit of Ceres, but it would be affected much less than many
>smaller asteroids.
>
The accelerator is going to need a big ass generator and
accelerator equipment. It seems to me that the cable could be much
more simple and cheaper (But limited in where it can send packages).

Hop David

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Sep 13, 2005, 5:45:26 PM9/13/05
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Mike Combs wrote:
> "James Nicoll" <jdni...@panix.com> wrote in message
> news:dg4gng$25a$1...@reader1.panix.com...
>
>>Hmmm. Ceres's day is about 9 hours. 10 km/s x 9 hrs x 3600 s
>>is 324,000 km, and if that is the circumference of a circle, r is
>>about 52,000 km. Think we can build a 52,000 km tether on Ceres?
>
>
> At that scale, I can't help but wonder if it wouldn't be cheaper to build an
> EM accelerator all the way around the asteroid. One could launch cargo and
> in so doing either be speeding up or slowing down the rotation rate,
> depending on your preference. Large volumes of launches would minutely
> affect the orbit of Ceres, but it would be affected much less than many
> smaller asteroids.
>

Remember in asteroids you can tunnel much deeper than on earth. IIRC on
earth tunnels more than 4 km deep will collapse from stress. Stress
caused by the weight of the earth above the tunnel or lateral stress
caused by tectonic plates.

SFAIK Asteroids don't have tectonic plates and the weight of material
above tunnels is much less for a given depth.

I believe it'd be possible to tunnel clear through Ceres. If you jumped
in a tunnel entrance at the north pole, you'd get a free ride to the
south pole.

Tunnels piercing Ceres would make it a colony throughout the _volume_ of
Ceres, rather than the surface. Some have said Ceres could be a
nationstate the size of Texas. But if the volume were exploited, it'd be
much larger.

Any way, I've imagined the tunnels piercing Ceres (or other asteroids)
housing mag rail trains. If you chose not to decelerate upon reaching
the middle, but instead keep on accelerating, you could turn the mag
rail tunnel into a linear accelerator.

A curved accelerator along the surface would lose delta vee fighting
acceleration from centrifugal force. A linear accelerator is more efficient.

A rail gun the diameter of Ceres could give cargo enough delta vee to
enter a Ceres to Earth transfer orbit and then some.

Pat Flannery

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Sep 13, 2005, 6:47:09 PM9/13/05
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Hop David wrote:

>
> I believe it'd be possible to tunnel clear through Ceres. If you
> jumped in a tunnel entrance at the north pole, you'd get a free ride
> to the south pole.


You get the added advantage that the deeper you go down your bore hole,
the less gravity you experience, till you hit zero G at the asteroid's
core. In fact, you could excavate a large spherical cavity at the center
of the asteroid and have the whole cavity be weightless,* which would be
a great place to store spacecraft at, as they wouldn't need any landing
gear, and would only need to be stressed to handle the forces that their
engines generate by their thrust.

* At least that's what my friend the physicist said.

Pat

Alain Fournier

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Sep 13, 2005, 11:12:02 PM9/13/05
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Hop David wrote:


> Any way, I've imagined the tunnels piercing Ceres (or other asteroids)
> housing mag rail trains. If you chose not to decelerate upon reaching
> the middle, but instead keep on accelerating, you could turn the mag
> rail tunnel into a linear accelerator.
>
> A curved accelerator along the surface would lose delta vee fighting
> acceleration from centrifugal force. A linear accelerator is more
> efficient.
>
> A rail gun the diameter of Ceres could give cargo enough delta vee to
> enter a Ceres to Earth transfer orbit and then some.

I don't think that would be very practical. You can't point the rail
gun. You would probably be better off just to build a rail gun of
similar size floating in free space near Ceres. It would be easier
to point just a big free floating rail gun than to point Ceres.
You could still build the mag rail train through the center of
Ceres for local transportation.

Alain Fournier

Hop David

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Sep 14, 2005, 9:55:07 AM9/14/05
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Alain Fournier wrote:
>
>
> Hop David wrote:
>
>
>> Any way, I've imagined the tunnels piercing Ceres (or other asteroids)
>> housing mag rail trains. If you chose not to decelerate upon reaching
>> the middle, but instead keep on accelerating, you could turn the mag
>> rail tunnel into a linear accelerator.
>>
>> A curved accelerator along the surface would lose delta vee fighting
>> acceleration from centrifugal force. A linear accelerator is more
>> efficient.
>>
>> A rail gun the diameter of Ceres could give cargo enough delta vee to
>> enter a Ceres to Earth transfer orbit and then some.
>
>
> I don't think that would be very practical. You can't point the rail
> gun.

If colonists attempt to fully exploit Ceres' volume, there could be a
number of asteroid piercing tunnels.

Ceres rotates. If there were 4 tunnels, exits at 0 degrees (the
equator), 30, 60 and 90 degrees (north or south pole) you could aim any
direction within 15 degrees.

About 4.9 km/sec sends Cargo earthward from Ceres's surface. If the
cargo was shot 15 degrees off from the desired direction, the correction
burn would be 1.3 km/sec.

1.3 vs 4.9 km/sec is some savings of reaction mass.

You would probably be better off just to build a rail gun of
> similar size floating in free space near Ceres.

Recoil may be an issue. If the gun's a 1000 times more massive than the
cargo, sending cargo off at 4.9 km/sec would send a floating gun in the
opposite direction at 4.9 meters/sec.

Mike Combs

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Sep 14, 2005, 1:31:38 PM9/14/05
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"James Nicoll" <jdni...@panix.com> wrote in message
news:dg75te$klm$1...@reader1.panix.com...

> >
> The accelerator is going to need a big ass generator and
> accelerator equipment.

Mass-driver-like technology can be made pretty efficient at converting
electricty to kinetic energy. But yeah, I'm sure we're talking about solar
arrays (or more likely concentrating mirrors and solar arrays) by the square
mile.

> It seems to me that the cable could be much
> more simple and cheaper (But limited in where it can send packages).

Simpler: undeniably true. But the question is which is cheaper/easier:
relatively simple cabling by the tens of thousands of kilometers, or
relatively more complex EM coils by the tens of kilometers?

Also, there's a bit more flexibility with the EM approach. You'll remember
I said we could launch in such a way as to either speed up or slow down the
rotation rate, depending on our preference? With a tether, exports would
only be able to reduce the rotation rate.

Mike Combs

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Sep 14, 2005, 1:40:35 PM9/14/05
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"Hop David" <hopspageHA...@tabletoptelephone.com> wrote in message
news:43274876...@tabletoptelephone.com...

>
> Remember in asteroids you can tunnel much deeper than on earth. IIRC on
> earth tunnels more than 4 km deep will collapse from stress. Stress
> caused by the weight of the earth above the tunnel or lateral stress
> caused by tectonic plates.

You know, my first thought was a straight tunnel through Ceres. But then I
decided that a mass driver encircling Ceres would be cheaper due to the
elimination of the need to tunnel. I was thinking more about holding costs
down than the problems of extremely deep tunnels.

> Any way, I've imagined the tunnels piercing Ceres (or other asteroids)
> housing mag rail trains. If you chose not to decelerate upon reaching
> the middle, but instead keep on accelerating, you could turn the mag
> rail tunnel into a linear accelerator.

Now that's a thought. If a maglev-type system is going to be built anyway
to provide transportation, and can then be turned into an export
accelerator, then you've gotten something else to absorb part of the
amortization.

> A curved accelerator along the surface would lose delta vee fighting
> acceleration from centrifugal force. A linear accelerator is more
efficient.

Maybe, but I'm not sure. The bracing requirements will certainly go up, but
even the straight mass driver will require considerable bracing.

Hop David

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Sep 14, 2005, 2:20:01 PM9/14/05
to

Mike Combs wrote:
> "Hop David" <hopspageHA...@tabletoptelephone.com> wrote in message
> news:43274876...@tabletoptelephone.com...
>
>>Remember in asteroids you can tunnel much deeper than on earth. IIRC on
>>earth tunnels more than 4 km deep will collapse from stress. Stress
>>caused by the weight of the earth above the tunnel or lateral stress
>>caused by tectonic plates.
>
>
> You know, my first thought was a straight tunnel through Ceres. But then I
> decided that a mass driver encircling Ceres would be cheaper due to the
> elimination of the need to tunnel. I was thinking more about holding costs
> down than the problems of extremely deep tunnels.
>
>
>>Any way, I've imagined the tunnels piercing Ceres (or other asteroids)
>>housing mag rail trains. If you chose not to decelerate upon reaching
>>the middle, but instead keep on accelerating, you could turn the mag
>>rail tunnel into a linear accelerator.
>
>
> Now that's a thought. If a maglev-type system is going to be built anyway
> to provide transportation, and can then be turned into an export
> accelerator, then you've gotten something else to absorb part of the
> amortization.

Yes, exactly.

Although using an intra Ceres transportation system as an interplanetary
rail gun might be like using a city freeway for a Space Shuttle runway.

>
>
>>A curved accelerator along the surface would lose delta vee fighting
>>acceleration from centrifugal force. A linear accelerator is more
>
> efficient.
>
> Maybe, but I'm not sure. The bracing requirements will certainly go up, but
> even the straight mass driver will require considerable bracing.
>

Centrifugal acceleration is w^2 * r
where w is angular velocity and r is radius of Ceres. If the cargo
followed a rail along the surface of Ceres, it's radial velocity would
remain zero (until release). It seems to me w^2 * r would be subtracted
from the acceleration exerted by a curved rail gun.

Sander Vesik

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Sep 14, 2005, 5:15:48 PM9/14/05
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Hop David <hopspageHA...@tabletoptelephone.com> wrote:
>
> Remember in asteroids you can tunnel much deeper than on earth. IIRC on
> earth tunnels more than 4 km deep will collapse from stress. Stress
> caused by the weight of the earth above the tunnel or lateral stress
> caused by tectonic plates.

I find this very hard to believe without a cite or math to show it. After
all, natural caves extend to over two kilometers, or about 1/3 of that claimed
maximal tunnel depth. The deepest mines - and that is not really just a
simple downwards tunnel - go to the depth of 3.5 kilometers. The practical
problem there is not the tunnel collapsing but temperature.

Most places on earth are rather far away from a border area between two
tectonic plates.

--
Sander

+++ Out of cheese error +++

Hop David

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Sep 14, 2005, 8:02:51 PM9/14/05
to

Sander Vesik wrote:
> Hop David <hopspageHA...@tabletoptelephone.com> wrote:
>
>>Remember in asteroids you can tunnel much deeper than on earth. IIRC on
>>earth tunnels more than 4 km deep will collapse from stress. Stress
>>caused by the weight of the earth above the tunnel or lateral stress
>>caused by tectonic plates.
>
>
> I find this very hard to believe without a cite or math to show it. After
> all, natural caves extend to over two kilometers, or about 1/3 of that claimed
> maximal tunnel depth. The deepest mines - and that is not really just a
> simple downwards tunnel - go to the depth of 3.5 kilometers.

How does citing 2 km deep caves and 3.5 km deep mines refute what I said?

The practical
> problem there is not the tunnel collapsing but temperature.


Actually both temperature and pressure are problems:
http://hypertextbook.com/facts/2003/YefimCavalier.shtml

Whether temperature or pressure make it difficult to dig deep tunnels
doesn't change my point that deeper tunnels could be dug on Ceres.

A few years ago a planetary scientist was kind enough to answer my
inquiries on this subject. I don't want to give his name as he likely
values his privacy. But here's some excerpts from his correspondence:

"How many atmospheres pressure can a tunnel take? Depends. Heroic
efforts are required even in hard rock at > 1000 atm. In rubble, all
strength comes from intentional reinforcement."

"A rubble-pile asteroid would provide "spelunking" access via its cracks
and pores."

"An asteroid will have significant pore space up to over 100 atm
pressure, virtually vanishing around 1000 atm."

He also gave this equation:

"central pressure of a homogeneous body increases with r^2
P(cent) = 4 pi G rho^2 r^2/9"

Ceres info (from Wikipedia)
radius 475000 meters
mass 9.5 * 10^20 kg
density = 2080 kg/meter^3

So central pressure (if Ceres were homogeneous)
=4 pi G (2080 kg/meter^3)^2 (475000 meters)^2/9
=90936300.35 newtons/meter^2
=897 atmospheres

bombardmentforce

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Sep 14, 2005, 8:44:03 PM9/14/05
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>tunnel clear through Ceres

Ted Taylor's tunneling nukes would be quite useful here.

Alain Fournier

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Sep 14, 2005, 9:34:38 PM9/14/05
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Hop David wrote:

> Alain Fournier wrote:
>
>> Hop David wrote:
>
>>> Any way, I've imagined the tunnels piercing Ceres (or other
>>> asteroids) housing mag rail trains. If you chose not to decelerate
>>> upon reaching the middle, but instead keep on accelerating, you could
>>> turn the mag rail tunnel into a linear accelerator.
>>>
>>> A curved accelerator along the surface would lose delta vee fighting
>>> acceleration from centrifugal force. A linear accelerator is more
>>> efficient.
>>>
>>> A rail gun the diameter of Ceres could give cargo enough delta vee to
>>> enter a Ceres to Earth transfer orbit and then some.
>>
>> I don't think that would be very practical. You can't point the rail
>> gun.
>
> If colonists attempt to fully exploit Ceres' volume, there could be a
> number of asteroid piercing tunnels.
>
> Ceres rotates. If there were 4 tunnels, exits at 0 degrees (the
> equator), 30, 60 and 90 degrees (north or south pole) you could aim any
> direction within 15 degrees.

You could also aim any direction within 15 degrees if you have 3 tunnels
at 15, 45 and 75 degrees. Or with 4 tunnels at 11.25, 33.75, 56.25
and 78.75 degrees you could aim any direction within 11.25 degrees.

> About 4.9 km/sec sends Cargo earthward from Ceres's surface. If the
> cargo was shot 15 degrees off from the desired direction, the correction
> burn would be 1.3 km/sec.
>
> 1.3 vs 4.9 km/sec is some savings of reaction mass.

Yes it is. But 1.3 km/s is still more than about 500 m/s needed
to reach an orbiting rail gun from Ceres.

> You would probably be better off just to build a rail gun of
>
>> similar size floating in free space near Ceres.
>
>
> Recoil may be an issue. If the gun's a 1000 times more massive than the
> cargo, sending cargo off at 4.9 km/sec would send a floating gun in the
> opposite direction at 4.9 meters/sec.

It is an issue, but not that big an issue. If your rail gun is only ten
times more massive than the cargo and it is in a highly elliptical orbit
around Ceres pointing in the right direction at periapsis, with orbital
speed at periapsis of 330 m/s, then you can give your cargo an extra
6.6 km/s, that is a total velocity of 6.93 km/s with the speed of the
rail gun. The recoil will give a 180 degree plane change to the rail
gun. You then reset the orbit of the rail gun at apoapsis to have it
pointing in the direction needed for the next payload. If you don't
want to give as much as 6.93 km/s to your cargo, you set it up to have
a plane change of less than 180 degrees. If your rail gun is 1000 more
massive than the cargo as you were suggesting you will typically have
only minor plane changes, but you will be lowering the apoapsis of the
rail gun or losing a part of the 330 m/s initial speed for the cargo
by shooting in a non optimal direction (non optimal for cargo
speed, maybe optimal for positioning the rail gun in a favorable
orbit).

Note that the above is merely an example of how you can deal with
recoil. A real system would probably prefer to have a higher periapsis,
which means a speed at periapsis lower than 330 m/s. If the rail
gun is very long, tidal forces near Ceres could bend your rail gun
in a way that would void its warranty :-)

This is just my opinion. I don't think it is really possible to
decide which would be best, the Ceres tunnel rail gun, the Ceres
surface rail gun or the Ceres orbiting rail gun without getting
into more details about what would be the purpose of the gun (how
much stuff is going to Earth, how much to Mars, how much to etc.)
and what kind of building materials are available.

Alain Fournier

Hop David

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Sep 15, 2005, 9:42:47 AM9/15/05
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Alain Fournier wrote:

> It is an issue, but not that big an issue. If your rail gun is only ten
> times more massive than the cargo and it is in a highly elliptical orbit
> around Ceres pointing in the right direction at periapsis, with orbital
> speed at periapsis of 330 m/s, then you can give your cargo an extra
> 6.6 km/s, that is a total velocity of 6.93 km/s with the speed of the
> rail gun. The recoil will give a 180 degree plane change to the rail
> gun. You then reset the orbit of the rail gun at apoapsis to have it
> pointing in the direction needed for the next payload.

You sound like Henry. That seems to be one of his favorite mantras: Do
the plane change at apoapsis. Of course it is sensible advice.

Changing aim is much easier for free floating railguns. Come to think of
it, the most frequently proposed landbased railguns are aimed at a
single target: A gun on our tidelocked moon aimed at an earth/moon L point.

Asteroids chock full of subterranean tunnels is an image I've been in
love with for several years now. But lack of gravity needed to stay
healthy is a big flaw in this imagined ant farm. A Ceres nation limited
only by tunnel digging speed would be much less constrained than one
that had to build Stanford Tori or spinning cylinders for its inhabitants.

bombardmentforce

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Sep 18, 2005, 2:59:36 PM9/18/05
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Fun things to calculate.

Dela V to attach Ceres to a Lunar elevator.

Maximum H2O transfer rate per ton of elevator structure.

Lunar climate at various rates of irrigation.

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