Another critism I have for Mars is that because of its difference in
atmosphere and Gravity any colonist immigrating to mars will be
condemning his decendents to permenant life on Mars. Their bones will
not be strong enough to handle Earth's gravity.

Colonists of Space Islands will not have this problem so long as their
colonies stick with a standard level of gravity.

Personally, I do not see Mars as colonizable, so I often find myself
ommitting this argument. Once man reaches into space to nest, there
will be little use for Planets to dwell upon.

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of terrierkeeper

> Another critism I have for Mars is that because of its
> difference in atmosphere and Gravity any colonist immigrating
> to mars will be condemning his decendents to permenant life
> on Mars. Their bones will not be strong enough to handle
> Earth's gravity.
>
> Colonists of Space Islands will not have this problem so
> long as their colonies stick with a standard level of gravity.

Yeah, even on a completely terraformed Mars, not only the level of
gravity but also the intensity of the sunlight will be different from
what we're used to. An orbital habitat can have what we consider normal
levels of sunlight, even if built in the outer parts of the solar
system.

Regards,

Mike Combs

Which is why Space Islands are better than any planet currently
available for terraformation either mars or Venus or any moon for
which artificial colonies may be built.

Utimately it is the Space Island that is the Future for man.

Unfortunately none of the Science articles I come across mention
this. There are too many talking of Generation Ships to Solar Systems
which we don't even know if they might have planets that are
habitable or even if they might have populations of their own.

Space Islands are safe bet in these aspects as well and they're
available.

Man must move into space. If learning history has taught me anything,
it is that viable cultures are those that are constantly growing.
Meeting challenges and prevailing. Space is they ultimate field to
provide man with these things.Ample room for expansion and many
challenges without putting any indingenous peoples pr species at
hazard.

Unfortunately No One of importance seems to realize this.

Excuse me for going 'political' but The elite has taken us down the
path of decadence and limited reproduction to deal with limited
resources whent the correct path is to move into new space for
reaching unlimited resources. All our elite has achieved is narrowing
the human gene pool.

We need to move into space as a matter of human survival.

--- In spacesettlers@yahoogroups.com, "Combs, Mike"
>
> From: spacesettlers@yahoogroups.com
> [mailto:spacesettlers@yahoogroups.com] On Behalf Of terrierkeeper
>
> > Another critism I have for Mars is that because of its
> > difference in atmosphere and Gravity any colonist immigrating
> > to mars will be condemning his decendents to permenant life
> > on Mars. Their bones will not be strong enough to handle
> > Earth's gravity.
> >
> > Colonists of Space Islands will not have this problem so
> > long as their colonies stick with a standard level of gravity.
>
> Yeah, even on a completely terraformed Mars, not only the level of
> gravity but also the intensity of the sunlight will be different
from
> what we're used to. An orbital habitat can have what we consider
normal

an old mountaineer told me that to reach the top you
must climb one step at a time
we all agree on the ultimate advantages of totally
artificial space settlements, they can be located
everywhere on the solar system or exosolar planetary
systems, they can reproduce optimal atmosphere,weather
and gravity conditions for human habitat, they can
expand endleesly and allow mankind to reach entire
galaxies building artificial planets and not being
subject to local planets conditions, most, if not all,
of them will certainly prove hostile to us.
But entire generation s of sci fi culture has been
based on interplanetary flight, and most of us are
still planetcentric.
To reach the ultimate goals of space settlements we
still need to follow some necessary steps.
The Moon and mars are certainly the next ones, despite
their disadvantages and hostility, we need to master
such exraterrestrial habitats, use their resources
develop an affordable space transportation system
technologies before we could successfully use them to
build real space settlements.
So despite most opinions i still believe that the way
to go is to proceed with small but well planned steps
for space development on such bodies and then to the
asteroids in order to acquire all needee technologies
for more ambitiuos ones such as space settlements
--- terrierkeeper ha scritto:

Which is why Space Islands are better than any planet
currently
available for terraformation either mars or Venus or
any moon for
which artificial colonies may be built.

Utimately it is the Space Island that is the Future
for man.

Unfortunately none of the Science articles I come
across mention
this. There are too many talking of Generation Ships
to Solar Systems
which we don't even know if they might have planets
that are
habitable or even if they might have populations of
their own.

Space Islands are safe bet in these aspects as well
and they're
available.

Man must move into space. If learning history has
taught me anything,
it is that viable cultures are those that are
constantly growing.
Meeting challenges and prevailing. Space is they
ultimate field to
provide man with these things.Ample room for expansion
and many
challenges without putting any indingenous peoples pr
species at
hazard.

Unfortunately No One of importance seems to realize
this.

Excuse me for going 'political' but The elite has
taken us down the
path of decadence and limited reproduction to deal
with limited
resources whent the correct path is to move into new
space for
reaching unlimited resources. All our elite has
achieved is narrowing
the human gene pool.

We need to move into space as a matter of human
survival.

--- In spacesettlers@yahoogroups.com, "Combs, Mike"

>
> From: spacesettlers@yahoogroups.com
> [mailto:spacesettlers@yahoogroups.com] On Behalf Of
terrierkeeper
>
> > Another critism I have for Mars is that because of
its
> > difference in atmosphere and Gravity any colonist
immigrating
> > to mars will be condemning his decendents to
permenant life
> > on Mars. Their bones will not be strong enough to
handle
> > Earth's gravity.
> >
> > Colonists of Space Islands will not have this
problem so
> > long as their colonies stick with a standard level
of gravity.
>
> Yeah, even on a completely terraformed Mars, not
only the level of
> gravity but also the intensity of the sunlight will
be different
from
> what we're used to. An orbital habitat can have
what we consider
normal
> levels of sunlight, even if built in the outer parts
of the solar
> system.
>
> Regards,
>
> Mike Combs
>

Science education
History of space
exploration My
Space exploration

>The elite has taken us down the path of decadence and limited
reproduction to deal with limited resources whent the correct path
is to move into new space for reaching unlimited resources.<

Unlimited resources, in a context of exponential growth!? I thought
we had beaten that dead horse enough. Do I need to do the
calculation about the sphere expanding at c?

--- In spacesettlers@yahoogroups.com, "terrierkeeper"
wrote:
>
> Which is why Space Islands are better than any planet currently
> available for terraformation either mars or Venus or any moon for
> which artificial colonies may be built.
>
> Utimately it is the Space Island that is the Future for man.
>
> Unfortunately none of the Science articles I come across mention
> this. There are too many talking of Generation Ships to Solar
Systems
> which we don't even know if they might have planets that are
> habitable or even if they might have populations of their own.
>
> Space Islands are safe bet in these aspects as well and they're
> available.
>
> Man must move into space. If learning history has taught me
anything,
> it is that viable cultures are those that are constantly growing.
> Meeting challenges and prevailing. Space is they ultimate field to
> provide man with these things.Ample room for expansion and many
> challenges without putting any indingenous peoples pr species at
> hazard.
>
> Unfortunately No One of importance seems to realize this.
>
> Excuse me for going 'political' but The elite has taken us down
the
> path of decadence and limited reproduction to deal with limited
> resources whent the correct path is to move into new space for
> reaching unlimited resources. All our elite has achieved is
narrowing
> the human gene pool.
>
> We need to move into space as a matter of human survival.
>
> --- In spacesettlers@yahoogroups.com, "Combs, Mike"

> wrote:
> >
> > From: spacesettlers@yahoogroups.com
> > [mailto:spacesettlers@yahoogroups.com] On Behalf Of terrierkeeper
> >
> > > Another critism I have for Mars is that because of its
> > > difference in atmosphere and Gravity any colonist immigrating
> > > to mars will be condemning his decendents to permenant life
> > > on Mars. Their bones will not be strong enough to handle
> > > Earth's gravity.
> > >
> > > Colonists of Space Islands will not have this problem so
> > > long as their colonies stick with a standard level of gravity.
> >
> > Yeah, even on a completely terraformed Mars, not only the level
of
> > gravity but also the intensity of the sunlight will be different
> from
> > what we're used to. An orbital habitat can have what we
consider

Planets (other than earth) are worthless junk until asteroids get so
scarce that it's worth taking the planets apart. Doing terraforming
as an intermediate step before orbital habitats is like doing
Everest as an intermediate step before the Appalachian Trail.

--- In spacesettlers@yahoogroups.com, giorgio gaviraghi
wrote:

Zubrin's jump for Mars is more like Mao's great leap forward rather
than a small step for mankind.

Space Island's give us the room for humanity to frow within our
grasp.

The moon is a source of raw materials, like asteroids, with which to
build those islands. Mars is a waste. Too much gravity to make any
mining affordable. Not enough to sustain atmosphere or human beings.

I believe our steps should be practical ones. Spacie SIlands give us
Endless Space. Mars is too limited.

--- In spacesettlers@yahoogroups.com, giorgio gaviraghi
wrote:

Terrierkeeper wrote:

...Excuse me for going 'political' but The elite has taken us down the
path of decadence and limited reproduction to deal with limited
resources whent the correct path is to move into new space for
reaching unlimited resources. All our elite has achieved is narrowing
the human gene pool....

Agree with you very much. We have to step on the gas with space exploration. Also, one has to worry about the status of men on our planet. Practically all jobs on planet earth - which now are of a housekeeping nature - can be done better by women. It has become a boring sight, seeing pictures of a smart woman executive flanked by two foolishly grinning men. Men are designed to do dangerous things. It is not surprising that women are not interested in men any more : - )

Selvaraj

From: terrierkeeper
To: spacesettlers@yahoogroups.com
Sent: Wednesday, November 02, 2005 7:47 PM
Subject: [spacesettlers] Re: Zubrin citisism

Which is why Space Islands are better than any planet currently
available for terraformation either mars or Venus or any moon for
which artificial colonies may be built.

Utimately it is the Space Island that is the Future for man.

Unfortunately none of the Science articles I come across mention
this. There are too many talking of Generation Ships to Solar Systems
which we don't even know if they might have planets that are
habitable or even if they might have populations of their own.

Space Islands are safe bet in these aspects as well and they're
available.

Man must move into space. If learning history has taught me anything,
it is that viable cultures are those that are constantly growing.
Meeting challenges and prevailing. Space is they ultimate field to
provide man with these things.Ample room for expansion and many
challenges without putting any indingenous peoples pr species at
hazard.

Unfortunately No One of importance seems to realize this.

Excuse me for going 'political' but The elite has taken us down the
path of decadence and limited reproduction to deal with limited
resources whent the correct path is to move into new space for
reaching unlimited resources. All our elite has achieved is narrowing
the human gene pool.

We need to move into space as a matter of human survival.

--- In spacesettlers@yahoogroups.com, "Combs, Mike"
wrote:
>
> From: spacesettlers@yahoogroups.com
> [mailto:spacesettlers@yahoogroups.com] On Behalf Of terrierkeeper
>
> > Another critism I have for Mars is that because of its
> > difference in atmosphere and Gravity any colonist immigrating
> > to mars will be condemning his decendents to permenant life
> > on Mars. Their bones will not be strong enough to handle
> > Earth's gravity.
> >
> > Colonists of Space Islands will not have this problem so
> > long as their colonies stick with a standard level of gravity.
>
> Yeah, even on a completely terraformed Mars, not only the level of
> gravity but also the intensity of the sunlight will be different
from
> what we're used to. An orbital habitat can have what we consider
normal
> levels of sunlight, even if built in the outer parts of the solar
> system.
>
> Regards,
>
> Mike Combs

> Mars is a waste. Too much gravity to make any mining affordable.

That depends on the value of the materials, and the technology
available to mine and launch them. By the time we deplete the main
belt, the Kuiper Belt, and various moons (assuming we don't kill
ourselves off first), mining Mars will definitely be feasible.

Possibly even before, depending on the technology. If mass drivers,
catchers, and energy sources all fulfill all our fondest hopes, then
it might be simpler, for many materials anyway, to throw stuff from
Mars than to go chasing down asteroids.

For the foreseeable, of course, planets other than earth are nothing
but scenery and gravitational assist.

--- In spacesettlers@yahoogroups.com, "terrierkeeper"
wrote:
>
> Zubrin's jump for Mars is more like Mao's great leap forward
rather
> than a small step for mankind.
>
> Space Island's give us the room for humanity to frow within our
> grasp.
>
> The moon is a source of raw materials, like asteroids, with which
to
> build those islands. Mars is a waste. Too much gravity to make any
> mining affordable. Not enough to sustain atmosphere or human
beings.
>
> I believe our steps should be practical ones. Spacie SIlands give
us

I am planet centric in this life time, but what you say is correct. One thing
that I have not seen said since I wrote it to Marshall Savage in 1985 is that
Space Islands will be able to survive the collapse of this Universe by being
able to move into neighboring Universe's thus extending the existence of
mankind to unlimited.

John Wayne Smith

speaking of necessary steps I am referring to the new
Nasa moon plans and Zubrin Mars Direct concept, not
terraforming or anything similar since the above
steps are possible with existing technology.
Mars terraforming is centuries away if ever, and will
certainly not be a necessary step for space
settlements, for such event we will need anyway such
technologies as an affordable space transportaion
system, a space infrstructural system, asteroid
deflection system , moecular assembler from local raw
materials and many others, still far away in the
future.
If is taking over 10 years to build a station for six
people at 300kms from Earth, to asssemble an island
along O'Neill ideas we will need centuries at current
rate of space technology progress.
In any event Zubrin is doing a very fine job in
promoting and keeping alive the concept of Mars manned
missions, what we are lacking is a similar exposure
for the space settlement concept.
--- terrierkeeper ha scritto:

Zubrin's jump for Mars is more like Mao's great leap
forward rather
than a small step for mankind.

Space Island's give us the room for humanity to frow
within our
grasp.

The moon is a source of raw materials, like asteroids,
with which to
build those islands. Mars is a waste. Too much gravity
to make any
mining affordable. Not enough to sustain atmosphere or
human beings.

I believe our steps should be practical ones. Spacie
SIlands give us
Endless Space. Mars is too limited.

--- In spacesettlers@yahoogroups.com, giorgio
gaviraghi
wrote:
>
> an old mountaineer told me that to reach the top you
> must climb one step at a time
> we all agree on the ultimate advantages of totally
> artificial space settlements, they can be located
> everywhere on the solar system or exosolar planetary
> systems, they can reproduce optimal
atmosphere,weather
> and gravity conditions for human habitat, they can
> expand endleesly and allow mankind to reach entire
> galaxies building artificial planets and not being
> subject to local planets conditions, most, if not
all,
> of them will certainly prove hostile to us.
> But entire generation s of sci fi culture has been
> based on interplanetary flight, and most of us are
> still planetcentric.
> To reach the ultimate goals of space settlements we
> still need to follow some necessary steps.
> The Moon and mars are certainly the next ones,
despite
> their disadvantages and hostility, we need to master
> such exraterrestrial habitats, use their resources
> develop an affordable space transportation system
> technologies before we could successfully use them
to
> build real space settlements.
> So despite most opinions i still believe that the
way
> to go is to proceed with small but well planned
steps
> for space development on such bodies and then to the
> asteroids in order to acquire all needee
technologies
> for more ambitiuos ones such as space settlements
> --- terrierkeeper ha scritto:
>
> Which is why Space Islands are better than any
planet
> currently
> available for terraformation either mars or Venus or
> any moon for
> which artificial colonies may be built.
>
> Utimately it is the Space Island that is the Future
> for man.
>
> Unfortunately none of the Science articles I come
> across mention
> this. There are too many talking of Generation Ships
> to Solar Systems
> which we don't even know if they might have planets
> that are
> habitable or even if they might have populations of
> their own.
>
> Space Islands are safe bet in these aspects as well
> and they're
> available.
>
> Man must move into space. If learning history has
> taught me anything,
> it is that viable cultures are those that are
> constantly growing.
> Meeting challenges and prevailing. Space is they
> ultimate field to
> provide man with these things.Ample room for
expansion
> and many
> challenges without putting any indingenous peoples
pr
> species at
> hazard.
>
> Unfortunately No One of importance seems to realize
> this.
>
> Excuse me for going 'political' but The elite has
> taken us down the
> path of decadence and limited reproduction to deal
> with limited
> resources whent the correct path is to move into new
> space for
> reaching unlimited resources. All our elite has
> achieved is narrowing
> the human gene pool.
>
> We need to move into space as a matter of human
> survival.
>
> --- In spacesettlers@yahoogroups.com, "Combs, Mike"
>
> wrote:
> >
> > From: spacesettlers@yahoogroups.com
> > [mailto:spacesettlers@yahoogroups.com] On Behalf
Of
> terrierkeeper
> >
> > > Another critism I have for Mars is that because
of
> its
> > > difference in atmosphere and Gravity any
colonist
> immigrating
> > > to mars will be condemning his decendents to
> permenant life
> > > on Mars. Their bones will not be strong enough
to
> handle
> > > Earth's gravity.
> > >
> > > Colonists of Space Islands will not have this
> problem so
> > > long as their colonies stick with a standard
level
> of gravity.
> >
> > Yeah, even on a completely terraformed Mars, not
> only the level of
> > gravity but also the intensity of the sunlight
will
> be different
> from
> > what we're used to. An orbital habitat can have
> what we consider
> normal
> > levels of sunlight, even if built in the outer
parts
> of the solar
> > system.
> >
> > Regards,
> >
> > Mike Combs
> >
> Science education

> History of space
> exploration My
> Space exploration

>
to:
>
10MB
>

Science education
History of space
exploration My
Space exploration

> From: giorgio gaviraghi
> speaking of necessary steps I am referring to the new
> Nasa moon plans and Zubrin Mars Direct concept, not
> terraforming or anything similar since the above
> steps are possible with existing technology.

Odd. People talk about Zubrin and 'his' idea to use resources in space to
reduce launch costs - but O'Neil came up with that idea back in the 70s, as
did many people before him.

> Mars terraforming is centuries away if ever, and will
> certainly not be a necessary step for space
> settlements, for such event we will need anyway such
> technologies as an affordable space transportaion
> system, a space infrstructural system, asteroid
> deflection system , moecular assembler from local raw
> materials and many others, still far away in the
> future.

Why do you lump an affordable space launch system, an astroid deflection
system - both of which are feasable with modern technology - with molecular
level assmblers which is not?

> If is taking over 10 years to build a station for six
> people at 300kms from Earth, to asssemble an island
> along O'Neill ideas we will need centuries at current
> rate of space technology progress.

You are confusing 'technology' with 'politics'.

> In any event Zubrin is doing a very fine job in
> promoting and keeping alive the concept of Mars manned
> missions, what we are lacking is a similar exposure
> for the space settlement concept.

Manned missions to Mars have always been practical. He just came up with a
particularly easy way to do it. Since then though he's rode rough shod over
almost all over considerations.His vision of Mars first Mars second Mars
third... and everythinhg else a distant hundredth place is not what I'd call
a good thing for space exploration, technology, or colonisation.

John

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of Dan Wylie-Sears

> > Mars is a waste. Too much gravity to make any mining affordable.
>
> That depends on the value of the materials, and the technology
> available to mine and launch them. By the time we deplete the
> main belt, the Kuiper Belt, and various moons (assuming we don't
> kill ourselves off first), mining Mars will definitely be feasible.

Yes, but by the time we've depleted all the various resources you've
mentioned, I think we'll be several millenniums into the future. In
which case technology will be so different that most any prediction we
make today will be wrong.

My viewpoint is that advances of technology will never change the fact
that obtaining resources from shallow gravity wells will require less
energy than from steep ones. That will always make a difference,
economically speaking. Marvelous technological advances may reduce the
magnitude of that difference, but will never eliminate it.

> Possibly even before, depending on the technology. If mass
> drivers, catchers, and energy sources all fulfill all our fondest
> hopes, then it might be simpler, for many materials anyway, to
> throw stuff from Mars than to go chasing down asteroids.

The problem with mass drivers for Mars is that while Mars doesn't have
much of an atmosphere, it's still enough to make horizontal EM launch
off the surface more difficult and problematic than launch through a
vacuum. Such launch from the Martian surface might be easier than from
the Earth's surface, but that's not saying much; it's fairly impractical
from the Earth's surface.

Regards,

Mike Combs

> Yes, but by the time we've depleted all the various resources
you've
> mentioned, I think we'll be several millenniums into the future.

Centuries, anyway. Exponential growth and all. But yes, long
enough that what we imagine now about the technology then is more
speculation or guess than prediction.

> My viewpoint is that advances of technology will never change the
> fact that obtaining resources from shallow gravity wells will
> require less energy than from steep ones. That will always make a
> difference, economically speaking.

It will indeed take more energy, and that will make a difference,
but if fusion works well, the additional energy well may be cheaper
than the time value of money to have your equipment moving from
asteroid to asteroid, for example. Then there's the recoil issue,
as with the moon: if you fling payloads from a colony or asteroid,
you've changed the orbit of the rest, whereas if you fling them from
mars or the moon you virtually haven't.

> The problem with mass drivers for Mars is that while Mars doesn't
> have much of an atmosphere, it's still enough to make horizontal
> EM launch off the surface more difficult and problematic than
> launch through a vacuum. Such launch from the Martian surface
> might be easier than from the Earth's surface, but that's not
> saying much; it's fairly impractical from the Earth's surface.

I recall reading some allegation that you would only lose about half
the energy of a telephone-pole-shaped payload launched from earth.
No idea whether that's accurate, though.

--- In spacesettlers@yahoogroups.com, "Combs, Mike"
>
> From: spacesettlers@...m
> [mailto:spacesettlers@yahoogroups.com] On Behalf Of Dan Wylie-Sears
>
> > > Mars is a waste. Too much gravity to make any mining
affordable.
> >
> > That depends on the value of the materials, and the technology
> > available to mine and launch them. By the time we deplete the
> > main belt, the Kuiper Belt, and various moons (assuming we don't
> > kill ourselves off first), mining Mars will definitely be
feasible.
>
> Yes, but by the time we've depleted all the various resources
you've
> mentioned, I think we'll be several millenniums into the future.
In
> which case technology will be so different that most any
prediction we
> make today will be wrong.
>
> My viewpoint is that advances of technology will never change the
fact
> that obtaining resources from shallow gravity wells will require
less
> energy than from steep ones. That will always make a difference,
> economically speaking. Marvelous technological advances may
reduce the
> magnitude of that difference, but will never eliminate it.
>
> > Possibly even before, depending on the technology. If mass
> > drivers, catchers, and energy sources all fulfill all our
fondest
> > hopes, then it might be simpler, for many materials anyway, to
> > throw stuff from Mars than to go chasing down asteroids.
>
> The problem with mass drivers for Mars is that while Mars doesn't
have
> much of an atmosphere, it's still enough to make horizontal EM
launch
> off the surface more difficult and problematic than launch through
a
> vacuum. Such launch from the Martian surface might be easier than
from
> the Earth's surface, but that's not saying much; it's fairly
impractical

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of Dan Wylie-Sears

> Then there's the recoil issue, as with the moon: if you fling
> payloads from a colony or asteroid, you've changed the orbit
> of the rest, whereas if you fling them from mars or the moon
> you virtually haven't.

No, I'd agree, and would never advocate mass driver launch of desired
payloads from a colony or asteroid. On the other hand, using asteroids
as reaction engines makes sense if we have some asteroidal material
containing some stuff we want to have, and more stuff that we don't
need.

> I recall reading some allegation that you would only lose about
> half the energy of a telephone-pole-shaped payload launched from
> earth. No idea whether that's accurate, though.

Oh, I'm sure it's a much better situation; less gravity and a whole lot
less atmosphere to punch through. Plus, Mars has these marvelous
volcanoes not far from the equator with long, sloping sides.

Regards,

Mike Combs

> No, I'd agree, and would never advocate mass driver launch of
> desired payloads from a colony or asteroid.

Having mentioned the problem, I'll turn right around and say that
it's not as bad as it sounds: for example, suppose you're in a
circular orbit, and you launch a payload in the direction you're
moving and then half an orbit later you launch one in the same
direction (which is now approximately opposite your direction of
motion) with the same amount of momentum relative to you. If I've
visualized it right, that puts you back into your original orbit.
By varying the masses of the payloads, you can launch them with any
speeds.

--- In spacesettlers@yahoogroups.com, "Combs, Mike"
>
> From: spacesettlers@yahoogroups.com
> [mailto:spacesettlers@yahoogroups.com] On Behalf Of Dan Wylie-Sears
>
> > Then there's the recoil issue, as with the moon: if you fling
> > payloads from a colony or asteroid, you've changed the orbit
> > of the rest, whereas if you fling them from mars or the moon
> > you virtually haven't.
>
> No, I'd agree, and would never advocate mass driver launch of
desired
> payloads from a colony or asteroid. On the other hand, using
asteroids
> as reaction engines makes sense if we have some asteroidal material
> containing some stuff we want to have, and more stuff that we don't
> need.
>
> > I recall reading some allegation that you would only lose about
> > half the energy of a telephone-pole-shaped payload launched from
> > earth. No idea whether that's accurate, though.
>
> Oh, I'm sure it's a much better situation; less gravity and a
whole lot

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of Dan Wylie-Sears

> Having mentioned the problem, I'll turn right around and say that
> it's not as bad as it sounds: for example, suppose you're in a
> circular orbit, and you launch a payload in the direction you're
> moving and then half an orbit later you launch one in the same
> direction (which is now approximately opposite your direction of
> motion) with the same amount of momentum relative to you. If
> I've visualized it right, that puts you back into your original orbit.

Actually, both impulses would have to be on the same side of the orbit,
but I get your point.

Regards,

Mike Combs

You're right that I visualized it wrong. I don't know whether
there's a solution for what I was trying to do. I wanted to find a
pair of impulses in the same direction that will cancel each other
out. To have zero net effect on angular momentum, they have to be
on opposite sides of the primary. But if I boost parallel to the
direction of motion, when I get around to the opposite side I'll be
higher, and I can't get back into the original orbit unless I'm at a
point where the two intersect.

To put it another way, I want to have a pair of orbits that
intersect at at two points. I start out in orbit one. When I get
to the first intersection point, I launch a payload such that the
impulse puts me into orbit two. Then when I get to the second
intersection point I launch another payload such that the impulse
puts me back into orbit one.

Of course, I don't really want to launch the payloads in the same
direction: I want to send them to the same destination. But trying
for the same direction was a simpler exercise to find out that I
didn't have it right.

--- In spacesettlers@yahoogroups.com, "Combs, Mike"
>
> From: spacesettlers@yahoogroups.com
> [mailto:spacesettlers@...m] On Behalf Of Dan Wylie-Sears
>
> > Having mentioned the problem, I'll turn right around and say
that
> > it's not as bad as it sounds: for example, suppose you're in a
> > circular orbit, and you launch a payload in the direction you're
> > moving and then half an orbit later you launch one in the same
> > direction (which is now approximately opposite your direction of
> > motion) with the same amount of momentum relative to you. If
> > I've visualized it right, that puts you back into your original
orbit.
>
> Actually, both impulses would have to be on the same side of the
orbit,

On 11/4/05, Dan Wylie-Sears wrote:
> You're right that I visualized it wrong. I don't know whether
> there's a solution for what I was trying to do. I wanted to find a
> pair of impulses in the same direction that will cancel each other
> out. To have zero net effect on angular momentum, they have to be
> on opposite sides of the primary.

You're thinking 2 dimensionally! (Insert geeky quote from Wrath of Khan here)

What you could do is arrange the initial orbit on a plane at 90
degrees to the final direction... That way the two kicks actually
cancel each other out perfectly... (It's a trick due to Bob Forward
AFAIK).

It's a bit inefficient of delta-v, but if you're high up in a gravity
well to start with, it doesn't matter quite so much.

-Ian Woollard

"People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

> You're thinking 2 dimensionally!

Good point. With orbits you often can, but no need to this time.

> It's a bit inefficient of delta-v, but if you're high up in a
> gravity well to start with, it doesn't matter quite so much.

Hey, the whole idea in this application is to burn off the delta-v
without messing with your orbit.

If I'm visualizing right (this time, for a change) it shouldn't
depend on the angle being 90 degrees. Any plane change and its
reversal half an orbit apart should work. In the case of launching
payloads from a colony without using reaction mass or messing with
the colony's orbit, the impulses are going to be small relative to
the colony's momentum. Roughly speaking, it seems as though you
ought to be able to launch at will in the direction perpendicular to
the plane of the orbit, and as long as launches happen at randomly
scattered points in the orbit it will all cancel out.

But having to launch in a single direction is a significant
constraint, so being able to get a component in the plane of the
orbit (with a solution to my 2D problem) would still be of value.

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
>
> On 11/4/05, Dan Wylie-Sears wrote:
> > You're right that I visualized it wrong. I don't know whether
> > there's a solution for what I was trying to do. I wanted to
find a
> > pair of impulses in the same direction that will cancel each
other
> > out. To have zero net effect on angular momentum, they have to
be
> > on opposite sides of the primary.
>
> You're thinking 2 dimensionally! (Insert geeky quote from Wrath of
Khan here)
>
> What you could do is arrange the initial orbit on a plane at 90
> degrees to the final direction... That way the two kicks actually
> cancel each other out perfectly... (It's a trick due to Bob Forward
> AFAIK).
>
> It's a bit inefficient of delta-v, but if you're high up in a
gravity
> well to start with, it doesn't matter quite so much.
>
> --
> -Ian Woollard
>
> "People are brilliantly stupid, and stupidly brilliant"-Robin
Abrahams

On 11/5/05, Dan Wylie-Sears wrote:
> If I'm visualizing right (this time, for a change) it shouldn't
> depend on the angle being 90 degrees.

No, it sort of does. If you angle it with the orbit too much you end
up changing apogee or perigee of your orbit- you're trying not to do
that I think.

You also have to be careful to put the projectile into escape-
otherwise it often comes back at you an orbit later- and at the same
speed you fired it at!

Me, I don't like punching holes in my windows, for one thing they keep
the suction out of the habitat. I'm funny like that.

-Ian Woollard

"People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

Me:
>> it shouldn't depend on the angle being 90 degrees.

Ian Woollard:
> No, it sort of does.

Ok, you well may be right, given the number of mistakes I've been
making lately. But where does the following reasoning go wrong?

(1) Given any orbit and any point on that orbit, you can draw a line
through that point and the center of the primary.

(2) That line intersects the orbit again an equal distance from the
primary on the other side (call it point two).

(3) Given any angle, there's a plane intersecting the plane of the
original orbit with that dihedral ange.

(4) In that plane, there's an orbit just like the original orbit
except for being in a different plane.

(5) That orbit (call it orbit two) also passes through point two.

(6) A body in orbit one at point one has a particular momentum (call
it m1). A body of the same mass in orbit two at point one has a
momentum (call it m2). The difference m2 minus m1 specifies an
impulse such that if that impulse is exerted at that point the
body will go from orbit one to orbit two. Because m1 and m2
have the same magnitude, this impulse is in the plane that
bisects the dihedral angle. It's also perpendicular to the line
through the primary.

(7) Likewise at point two.

(8) The two impulses do not in general have the same magnitude, but
they're in the same plane and perpendicular to the same line,
and hence have the same direction.

> You also have to be careful to put the projectile into escape-
> otherwise it often comes back at you an orbit later- and at the
> same speed you fired it at!

This is true when you're launching from a fixed location like the
lunar poles (although in that case it will hit the surface somewhere
else first unless you're launching horizontally). But otherwise it
will come back to where you were and you won't be there any more.
Still, it's a hazard because the orbital periods may have a small-
integer ratio, or close enough that your size makes up the
difference.

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
>
> On 11/5/05, Dan Wylie-Sears wrote:
> > If I'm visualizing right (this time, for a change) it shouldn't
> > depend on the angle being 90 degrees.
>
> No, it sort of does. If you angle it with the orbit too much you
end
> up changing apogee or perigee of your orbit- you're trying not to
do
> that I think.
>
> You also have to be careful to put the projectile into escape-
> otherwise it often comes back at you an orbit later- and at the
same
> speed you fired it at!
>
> Me, I don't like punching holes in my windows, for one thing they
keep
> the suction out of the habitat. I'm funny like that.
>
> --
> -Ian Woollard
>
> "People are brilliantly stupid, and stupidly brilliant"-Robin
Abrahams

"Combs, Mike" wrote:
> No, I'd agree, and would never advocate mass driver launch of
> desired payloads from a colony or asteroid. On the other hand,
> using asteroids as reaction engines makes sense if we have some
> asteroidal material containing some stuff we want to have, and more
> stuff that we don't need.

They might not *need* the "refuse" materials over the short term, but
eventually when settlements are being made from asteroids, on-site,
they might *want* those materials to be used for construction purposes
or something else.

I was thinking that sending the cargo via solar sails might be a way
to get around this. No recoil, the energy is "free", and no recoil
when the cargo arrives at the destination.

Dan,

Your making this way to complicated. A quick
tutorial on orbital mechanics should clear things up.
Here is a decnt one:
http://www.braeunig.us/space/orbmech.htm#maneuver

Basically, to do an orbital change to a higher
orbit, you do a delta-v change putting you at the
perigee of the new orbit which has an apogee of the
orbit you wish to be at. You then do a delta-v change
at the apogee of the orbit and you are now in the new
orbit. Switch apogee and perigee around and that is
how you move to a lower orbit.

Hope that helps!

Ryan

--- Dan Wylie-Sears wrote:

Good site. But a transfer orbit isn't relevant, because I'm
precisely trying *not* to change the apogee and perigee. I want to
launch payloads from a station while keeping the same orbit. Or to
catch payloads launched from somewhere else, again without messing
up your orbit.

What I'm talking about is illustrated nicely on that page, if you
scroll down slightly to the heading "Orbit Plane Changes". I'm
saying you can make a plane change, go around half an orbit, and
make another plane change back to the plane you started in. Ian
mentioned out that you can do it for a ninety-degree plane change,
and I'm trying to argue that you can do it for any angle.

--- In spacesettlers@yahoogroups.com, Ryan Z wrote:

No, no. I meant you fire the *projectile* at 90 degrees to the orbital
plane of the habitat!

The idea of trying to make a habitat do a 90 degree turn... that
wouldn't work at all in any short timescale.

On 11/7/05, Dan Wylie-Sears wrote:
> Good site. But a transfer orbit isn't relevant, because I'm
> precisely trying *not* to change the apogee and perigee. I want to
> launch payloads from a station while keeping the same orbit. Or to
> catch payloads launched from somewhere else, again without messing
> up your orbit.
>
> What I'm talking about is illustrated nicely on that page, if you
> scroll down slightly to the heading "Orbit Plane Changes". I'm
> saying you can make a plane change, go around half an orbit, and
> make another plane change back to the plane you started in. Ian
> mentioned out that you can do it for a ninety-degree plane change,
> and I'm trying to argue that you can do it for any angle.
>
> --- In spacesettlers@yahoogroups.com, Ryan Z wrote:
> >
> > Dan,
> >
> > Your making this way to complicated. A quick
> > tutorial on orbital mechanics should clear things up.
> > Here is a decnt one:
> > http://www.braeunig.us/space/orbmech.htm#maneuver
> >
> > Basically, to do an orbital change to a higher
> > orbit, you do a delta-v change putting you at the
> > perigee of the new orbit which has an apogee of the
> > orbit you wish to be at. You then do a delta-v change
> > at the apogee of the orbit and you are now in the new
> > orbit. Switch apogee and perigee around and that is
> > how you move to a lower orbit.
> >
> > Hope that helps!
> >
> > Ryan
> >
> > --- Dan Wylie-Sears wrote:
> >
> > > Me:
> > > >> it shouldn't depend on the angle being 90
> > > degrees.
> > >
> > > Ian Woollard:
> > > > No, it sort of does.
> > >
> > > Ok, you well may be right, given the number of
> > > mistakes I've been
> > > making lately. But where does the following
> > > reasoning go wrong?
> > >
> > > (1) Given any orbit and any point on that orbit, you
> > > can draw a line
> > > through that point and the center of the
> > > primary.
> > >
> > > (2) That line intersects the orbit again an equal
> > > distance from the
> > > primary on the other side (call it point two).
> > >
> > > (3) Given any angle, there's a plane intersecting
> > > the plane of the
> > > original orbit with that dihedral ange.
> > >
> > > (4) In that plane, there's an orbit just like the
> > > original orbit
> > > except for being in a different plane.
> > >
> > > (5) That orbit (call it orbit two) also passes
> > > through point two.
> > >
> > > (6) A body in orbit one at point one has a
> > > particular momentum (call
> > > it m1). A body of the same mass in orbit two at
> > > point one has a
> > > momentum (call it m2). The difference m2 minus
> > > m1 specifies an
> > > impulse such that if that impulse is exerted at
> > > that point the
> > > body will go from orbit one to orbit two.
> > > Because m1 and m2
> > > have the same magnitude, this impulse is in the
> > > plane that
> > > bisects the dihedral angle. It's also
> > > perpendicular to the line
> > > through the primary.
> > >
> > > (7) Likewise at point two.
> > >
> > > (8) The two impulses do not in general have the same
> > > magnitude, but
> > > they're in the same plane and perpendicular to
> > > the same line,
> > > and hence have the same direction.
> > >
> > > > You also have to be careful to put the projectile
> > > into escape-
> > > > otherwise it often comes back at you an orbit
> > > later- and at the
> > > > same speed you fired it at!
> > >
> > > This is true when you're launching from a fixed
> > > location like the
> > > lunar poles (although in that case it will hit the
> > > surface somewhere
> > > else first unless you're launching horizontally).
> > > But otherwise it
> > > will come back to where you were and you won't be
> > > there any more.
> > > Still, it's a hazard because the orbital periods may
> > > have a small-
> > > integer ratio, or close enough that your size makes
> > > up the
> > > difference.
> > >
> > > --- In spacesettlers@yahoogroups.com, Ian Woollard
> > > wrote:
> > > >
> > > > On 11/5/05, Dan Wylie-Sears wrote:
> > > > > If I'm visualizing right (this time, for a
> > > change) it shouldn't
> > > > > depend on the angle being 90 degrees.
> > > >
> > > > No, it sort of does. If you angle it with the
> > > orbit too much you
> > > end
> > > > up changing apogee or perigee of your orbit-
> > > you're trying not to
> > > do
> > > > that I think.
> > > >
> > > > You also have to be careful to put the projectile
> > > into escape-
> > > > otherwise it often comes back at you an orbit
> > > later- and at the
> > > same
> > > > speed you fired it at!
> > > >
> > > > Me, I don't like punching holes in my windows, for
> > > one thing they
> > > keep
> > > > the suction out of the habitat. I'm funny like
> > > that.
> > > >
> > > > --
> > > > -Ian Woollard
> > > >
> > > > "People are brilliantly stupid, and stupidly
> > > brilliant"-Robin
> > > Abrahams
> > > >
> > >

-Ian Woollard

"People are brilliantly stupid, and stupidly brilliant"-Robin Abrahams

From: spacesettlers@yahoogroups.com
[mailto:spacesettlers@yahoogroups.com] On Behalf Of wlm_efn

> They might not *need* the "refuse" materials over the short term,
> but eventually when settlements are being made from asteroids,
> on-site, they might *want* those materials to be used for
> construction purposes or something else.

When settlements are being made from asteroids, on-site, the problem of
moving the asteroidal material goes away.

But yes, I agree with you that there are very few materials for which we
can find no use at all. I did the most thinking about this scenario in
the context of somebody already involved in lunar mining, but wanting to
supplement it with raw material not commonly available from the moon.
So you might send an expedition to an asteroid (propelled by a mass
driver reaction tug), gather up some material, and process it on the
trip back, separating out the hydrogen, carbon, and nitrogen from the
oxygen and silicon. The parts you don't want (because you've already
got megatons of it from the moon) goes out the tailpipe as reaction
mass, and when you pull into HEO you've whittled your load down to tanks
of high-value volatiles.

Regards,

Mike Combs

Lol, it makes much more sense if I read it right. Turns out we're
saying essentially the same thing as far as I can tell. The only
difference is that you're implicitly assuming the impulse is small
relative to the momentum of the habitat, as in the case of an actual
colony launching any realistic payloads, whereas I'm interested in
allowing for the possibility of a small station that catches and
relaunces large payloads.

--- In spacesettlers@yahoogroups.com, Ian Woollard
wrote:
>
> No, no. I meant you fire the *projectile* at 90 degrees to the
orbital
> plane of the habitat!
>
> The idea of trying to make a habitat do a 90 degree turn... that
> wouldn't work at all in any short timescale.
>
> On 11/7/05, Dan Wylie-Sears wrote:
> > Good site. But a transfer orbit isn't relevant, because I'm
> > precisely trying *not* to change the apogee and perigee. I want
to
> > launch payloads from a station while keeping the same orbit. Or
to
> > catch payloads launched from somewhere else, again without
messing
> > up your orbit.
> >
> > What I'm talking about is illustrated nicely on that page, if you
> > scroll down slightly to the heading "Orbit Plane Changes". I'm
> > saying you can make a plane change, go around half an orbit, and
> > make another plane change back to the plane you started in. Ian
> > mentioned out that you can do it for a ninety-degree plane
change,
> > and I'm trying to argue that you can do it for any angle.
> >
> > --- In spacesettlers@yahoogroups.com, Ryan Z wrote:
> > >
> > > Dan,
> > >
> > > Your making this way to complicated. A quick
> > > tutorial on orbital mechanics should clear things up.
> > > Here is a decnt one:
> > > http://www.braeunig.us/space/orbmech.htm#maneuver
> > >
> > > Basically, to do an orbital change to a higher
> > > orbit, you do a delta-v change putting you at the
> > > perigee of the new orbit which has an apogee of the
> > > orbit you wish to be at. You then do a delta-v change
> > > at the apogee of the orbit and you are now in the new
> > > orbit. Switch apogee and perigee around and that is
> > > how you move to a lower orbit.
> > >
> > > Hope that helps!
> > >
> > > Ryan
> > >
> > > --- Dan Wylie-Sears wrote:
> > >
> > > > Me:
> > > > >> it shouldn't depend on the angle being 90
> > > > degrees.
> > > >
> > > > Ian Woollard:
> > > > > No, it sort of does.
> > > >
> > > > Ok, you well may be right, given the number of
> > > > mistakes I've been
> > > > making lately. But where does the following
> > > > reasoning go wrong?
> > > >
> > > > (1) Given any orbit and any point on that orbit, you
> > > > can draw a line
> > > > through that point and the center of the
> > > > primary.
> > > >
> > > > (2) That line intersects the orbit again an equal
> > > > distance from the
> > > > primary on the other side (call it point two).
> > > >
> > > > (3) Given any angle, there's a plane intersecting
> > > > the plane of the
> > > > original orbit with that dihedral ange.
> > > >
> > > > (4) In that plane, there's an orbit just like the
> > > > original orbit
> > > > except for being in a different plane.
> > > >
> > > > (5) That orbit (call it orbit two) also passes
> > > > through point two.
> > > >
> > > > (6) A body in orbit one at point one has a
> > > > particular momentum (call
> > > > it m1). A body of the same mass in orbit two at
> > > > point one has a
> > > > momentum (call it m2). The difference m2 minus
> > > > m1 specifies an
> > > > impulse such that if that impulse is exerted at
> > > > that point the
> > > > body will go from orbit one to orbit two.
> > > > Because m1 and m2
> > > > have the same magnitude, this impulse is in the
> > > > plane that
> > > > bisects the dihedral angle. It's also
> > > > perpendicular to the line
> > > > through the primary.
> > > >
> > > > (7) Likewise at point two.
> > > >
> > > > (8) The two impulses do not in general have the same
> > > > magnitude, but
> > > > they're in the same plane and perpendicular to
> > > > the same line,
> > > > and hence have the same direction.
> > > >
> > > > > You also have to be careful to put the projectile
> > > > into escape-
> > > > > otherwise it often comes back at you an orbit
> > > > later- and at the
> > > > > same speed you fired it at!
> > > >
> > > > This is true when you're launching from a fixed
> > > > location like the
> > > > lunar poles (although in that case it will hit the
> > > > surface somewhere
> > > > else first unless you're launching horizontally).
> > > > But otherwise it
> > > > will come back to where you were and you won't be
> > > > there any more.
> > > > Still, it's a hazard because the orbital periods may
> > > > have a small-
> > > > integer ratio, or close enough that your size makes
> > > > up the
> > > > difference.
> > > >
> > > > --- In spacesettlers@yahoogroups.com, Ian Woollard
> > > > wrote:
> > > > >
> > > > > On 11/5/05, Dan Wylie-Sears wrote:
> > > > > > If I'm visualizing right (this time, for a
> > > > change) it shouldn't
> > > > > > depend on the angle being 90 degrees.
> > > > >
> > > > > No, it sort of does. If you angle it with the
> > > > orbit too much you
> > > > end
> > > > > up changing apogee or perigee of your orbit-
> > > > you're trying not to
> > > > do
> > > > > that I think.
> > > > >
> > > > > You also have to be careful to put the projectile
> > > > into escape-
> > > > > otherwise it often comes back at you an orbit
> > > > later- and at the
> > > > same
> > > > > speed you fired it at!
> > > > >
> > > > > Me, I don't like punching holes in my windows, for
> > > > one thing they
> > > > keep
> > > > > the suction out of the habitat. I'm funny like
> > > > that.
> > > > >
> > > > > --
> > > > > -Ian Woollard
> > > > >
> > > > > "People are brilliantly stupid, and stupidly
> > > > brilliant"-Robin
> > > > Abrahams
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
> --
> -Ian Woollard
>
> "People are brilliantly stupid, and stupidly brilliant"-Robin
Abrahams