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A first blueprint for interstellar travel



 
 
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  #1  
Old August 31st 04, 11:05 AM
Abdul Ahad
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Default A first blueprint for interstellar travel

I was toying with this idea for a *possible* futuristic voyage to
Alpha Centauri, with a big emphasis on water and life support resource
mining from comets and planetoids encountered along the journey:-

http://uk.geocities.com/aa_spaceagen...ropulsion.html


Specifically, I would like to know if anyone has thoughts on whether
an inter-vessel, ship-to-comet robotic attachment of some kind could
be built (with technology easy to visualise in the current era), which
scoops up and proceses the frozen material from comets into water and
hydrogen/oxygen for power and life support. The robotic arm would dig
into the exterior ice of the comet upon a gentle, speed-matched
docking rendezvous in-flight.

My starship concept demands a large scale structure extending perhaps
a few kilometres in length. Is our current materials science
technology adequate to build and operate something on that scale that
would be robust enough for the job to take the stresses involved where
the asteroid has a spin as well?

A further complexity is to rotate my asteroid to create artificial
gravity. As the robotic mining "arms" are going to be erected to
either side of the cylindrical asteroid body, upon contact with comets
the spin rate would slow down due to the added mass of the comet. If
the asteroid is say 10km long and 5km wide (and highly dense e.g. 2.9
grams/cm^3), and the cometary nucleus captured by the arms is say just
2 or 3km in diameter (with a density equivalent to that of water,
since its "icy"), would the spin rate of the asteroid slow very
drastically in such an encounter?

My last point is if my asteroid is rotating along a spin axis which
runs through the *length* of its body (through the core), what are my
options of "pitching" the asteroid from side to side without
disrupting the spin rate (and the artificial gravity that it
generates)? Would it be feasible to use *pulse* thrust at favourable
intervals if I wanted to turn the body around?

Thanks for all thoughts.
Abdul Ahad
  #2  
Old September 4th 04, 11:31 PM
John Thingstad
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On 31 Aug 2004 03:05:11 -0700, Abdul Ahad
wrote:

I was toying with this idea for a *possible* futuristic voyage to
Alpha Centauri, with a big emphasis on water and life support resource
mining from comets and planetoids encountered along the journey:-

http://uk.geocities.com/aa_spaceagen...ropulsion.html


Specifically, I would like to know if anyone has thoughts on whether
an inter-vessel, ship-to-comet robotic attachment of some kind could
be built (with technology easy to visualise in the current era), which
scoops up and proceses the frozen material from comets into water and
hydrogen/oxygen for power and life support. The robotic arm would dig
into the exterior ice of the comet upon a gentle, speed-matched
docking rendezvous in-flight.

My starship concept demands a large scale structure extending perhaps
a few kilometres in length. Is our current materials science
technology adequate to build and operate something on that scale that
would be robust enough for the job to take the stresses involved where
the asteroid has a spin as well?

A further complexity is to rotate my asteroid to create artificial
gravity. As the robotic mining "arms" are going to be erected to
either side of the cylindrical asteroid body, upon contact with comets
the spin rate would slow down due to the added mass of the comet. If
the asteroid is say 10km long and 5km wide (and highly dense e.g. 2.9
grams/cm^3), and the cometary nucleus captured by the arms is say just
2 or 3km in diameter (with a density equivalent to that of water,
since its "icy"), would the spin rate of the asteroid slow very
drastically in such an encounter?

My last point is if my asteroid is rotating along a spin axis which
runs through the *length* of its body (through the core), what are my
options of "pitching" the asteroid from side to side without
disrupting the spin rate (and the artificial gravity that it
generates)? Would it be feasible to use *pulse* thrust at favourable
intervals if I wanted to turn the body around?

Thanks for all thoughts.
Abdul Ahad


Indeed you get a lot of fuel that way. But not in a very manageble form.
Breaking up the water into hydrogen and oxygen will require
you to use as much energy breaking the binding as you get when recombining
the elements. Altso the sheer mass of the comet is huge meaning
you would need a huge thrust.

The key to interstellar travel is to maximize the mass to energy ratio.
(the infamous antimatter motor perhaps)

Or you could get your energy as you go.

Robert Forward suggest not bringing it allong but focusing huge
lasers on a sun sail. (probaly the most plausible suggestion I
have seen so far)

Larry Niven prefers the Buzzard ramscoop, a fusion jet that uses a
huge magnetic field in front of the ship to scoop up interstellar hydrogen.
(Probaly won't work..)

From what I can see we are nowhere near solving the problem.
Even when fusing hydrogen, say, the energy to weight ratio is not
favorable.

--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/
  #3  
Old September 8th 04, 02:14 AM
T
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Default

John Thingstad wrote:

snip
Larry Niven prefers the Buzzard ramscoop, a fusion jet that uses a
huge magnetic field in front of the ship to scoop up interstellar hydrogen.
(Probaly won't work..)




Were you misspelling 'Bussard' on porpoise?

http://en.wikipedia.org/wiki/Bussard_ramjet


TBerk
  #4  
Old September 10th 04, 02:40 AM
Lizerd
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Default





"T" wrote in message
. com...
John Thingstad wrote:

snip
Larry Niven prefers the Buzzard ramscoop, a fusion jet that uses a
huge magnetic field in front of the ship to scoop up interstellar

hydrogen.
(Probaly won't work..)




Were you misspelling 'Bussard' on porpoise?

http://en.wikipedia.org/wiki/Bussard_ramjet


TBerk

Maybe not...
I think he wants to pick-up the dead birds is space to use a fuel for the
crew
as well....
(or, it could have been a tipeo....)

--
(All advice is checked, re-checked and verified to be questionable....)


  #5  
Old September 12th 04, 01:54 AM
Carey Sublette
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Posts: n/a
Default


"John Thingstad" wrote in message
news
On 31 Aug 2004 03:05:11 -0700, Abdul Ahad
wrote:

...
Robert Forward suggest not bringing it allong but focusing huge
lasers on a sun sail. (probaly the most plausible suggestion I
have seen so far)


Once you've got a stationary phased laser array to deliver power to a
distant vessel, the question becomes:
"What is the most effective way to use this energy?"

A reflector sail is a terribly inefficient way to use it (unless you are
already travelling at high relativistic speeds).

What makes the solar sail attractive is that it is a simple inexpensive way
to harness energy that is free, and which is also within the reach of
current technology.

Once one contemplates building a vast space laser energy projector the
energy is far from free, and you are working in the realm of future
technology anyway.

Roughly speaking, energy in a rocket propulsion system is used most
efficiently when the exhaust velocity is approximately equal to the burn-out
velocity. In this realm the mass ratios are not extravagant, and the
fraction of energy ending up in payload velocity is pretty good.

So capturing the beamed energy, converting it to electricity, and using it
to power what is essentially a low energy (but extremely high current)
particle accelerator would provide efficient use.

I envisage a modular "sail" of independent units that collect light, convert
it to electricity and power arrays of accelerators that are harnessed
together to pull the spacecraft.





Larry Niven prefers the Buzzard ramscoop, a fusion jet that uses a
huge magnetic field in front of the ship to scoop up interstellar

hydrogen.
(Probaly won't work..)

From what I can see we are nowhere near solving the problem.
Even when fusing hydrogen, say, the energy to weight ratio is not
favorable.

--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/


  #6  
Old September 12th 04, 06:58 AM
Trakar Shaitanaku
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Posts: n/a
Default

On Sun, 12 Sep 2004 00:54:20 GMT, "Carey Sublette"
wrote:

So capturing the beamed energy, converting it to electricity, and using it
to power what is essentially a low energy (but extremely high current)
particle accelerator would provide efficient use.

I envisage a modular "sail" of independent units that collect light, convert
it to electricity and power arrays of accelerators that are harnessed
together to pull the spacecraft.


For an interstellar system, however, we are talking about collimating
a very powerful "beam" over long distances, and even a focused
coherent beam is going to suffer considerable spread and diffusion
from even negligible system imperfections over this kind of distance.

Beamed power seems usable within the solar system, but beyond, I'd
want a contained power system, There have been several high dv
ablative solar sail systems, but they are mostly only good for initial
boosts. Couple this with a few MASER beamed power systems (which if
you'd rather convert to electrical power as opposed to just reflecting
them is fine) to continue the boost to the outer system, and you could
probably get some reasonable size payloads up to 10% or so c. More
than enough for first generation interstellar probes.
  #7  
Old September 13th 04, 03:37 AM
Parallax
external usenet poster
 
Posts: n/a
Default

"Carey Sublette" wrote in message nk.net...
"John Thingstad" wrote in message
news
On 31 Aug 2004 03:05:11 -0700, Abdul Ahad
wrote:

..
Robert Forward suggest not bringing it allong but focusing huge
lasers on a sun sail. (probaly the most plausible suggestion I
have seen so far)


Once you've got a stationary phased laser array to deliver power to a
distant vessel, the question becomes:
"What is the most effective way to use this energy?"

A reflector sail is a terribly inefficient way to use it (unless you are
already travelling at high relativistic speeds).

What makes the solar sail attractive is that it is a simple inexpensive way
to harness energy that is free, and which is also within the reach of
current technology.

Once one contemplates building a vast space laser energy projector the
energy is far from free, and you are working in the realm of future
technology anyway.

Roughly speaking, energy in a rocket propulsion system is used most
efficiently when the exhaust velocity is approximately equal to the burn-out
velocity. In this realm the mass ratios are not extravagant, and the
fraction of energy ending up in payload velocity is pretty good.

So capturing the beamed energy, converting it to electricity, and using it
to power what is essentially a low energy (but extremely high current)
particle accelerator would provide efficient use.

I envisage a modular "sail" of independent units that collect light, convert
it to electricity and power arrays of accelerators that are harnessed
together to pull the spacecraft.





Larry Niven prefers the Buzzard ramscoop, a fusion jet that uses a
huge magnetic field in front of the ship to scoop up interstellar

hydrogen.
(Probaly won't work..)

From what I can see we are nowhere near solving the problem.
Even when fusing hydrogen, say, the energy to weight ratio is not
favorable.

--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/


Carey:

Instead of having the starship carry the fuel and use on-board energy
to accelerate it, why not have the ship capture fuel packets that have
been previously been sent out in streams so that when the ship is
accelerating, it reaches a packet at very small relative velocity.
There is no net savings in energy but this does enable you to
investmost of your capital in the fuel mass driver close to home where
it is able to serve several ships. Of course, this does not solve the
problem of slowing down but does help in the acceleration phase. For
a "Mini-Mag Orion", I once did the calculation and found that if the
fuel was sent as a stream of fuel from a neutral particle beam, the
fuel current was reasonable as was the energy/atom in MeV of the fuel
kinetic energy (I dont remember the specifics). A fuel mass driver
close to home could use an energy source of large size that doesnt
need to be acclerated. Even a ion drive scaled up from the existing
Deep Space craft maybe becomes reasonable if you do not have to carry
the fuel but capture it in a stream sent to the craft which uses a
nuke reactor to provide electricity for the ion engine. I am sure
this idea isnt original but have never seen it elsewhere.

David OHara
  #8  
Old September 13th 04, 02:13 PM
Parallax
external usenet poster
 
Posts: n/a
Default

"Carey Sublette" wrote in message nk.net...
"John Thingstad" wrote in message
news
On 31 Aug 2004 03:05:11 -0700, Abdul Ahad
wrote:

..
Robert Forward suggest not bringing it allong but focusing huge
lasers on a sun sail. (probaly the most plausible suggestion I
have seen so far)


Once you've got a stationary phased laser array to deliver power to a
distant vessel, the question becomes:
"What is the most effective way to use this energy?"

A reflector sail is a terribly inefficient way to use it (unless you are
already travelling at high relativistic speeds).

What makes the solar sail attractive is that it is a simple inexpensive way
to harness energy that is free, and which is also within the reach of
current technology.

Once one contemplates building a vast space laser energy projector the
energy is far from free, and you are working in the realm of future
technology anyway.

Roughly speaking, energy in a rocket propulsion system is used most
efficiently when the exhaust velocity is approximately equal to the burn-out
velocity. In this realm the mass ratios are not extravagant, and the
fraction of energy ending up in payload velocity is pretty good.

So capturing the beamed energy, converting it to electricity, and using it
to power what is essentially a low energy (but extremely high current)
particle accelerator would provide efficient use.

I envisage a modular "sail" of independent units that collect light, convert
it to electricity and power arrays of accelerators that are harnessed
together to pull the spacecraft.





Larry Niven prefers the Buzzard ramscoop, a fusion jet that uses a
huge magnetic field in front of the ship to scoop up interstellar

hydrogen.
(Probaly won't work..)

From what I can see we are nowhere near solving the problem.
Even when fusing hydrogen, say, the energy to weight ratio is not
favorable.

--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/


People have proposed solar sails driven by laser or maser close to the
sun. Having the power source stay home has many advantages. However,
even a laser has some beam divergence so that as the sail gets VERY
far away the sail intercepts very little of the beam. You can imagine
concentrating the beam with some sort of lens but there is no material
that could withstand the required power densities. Furthermore, to
get good angular resolution of the beam with such a lens, you need
very large apertures, many tens of miles. People have proposed large
mirror systems consisting of very thin polymer but as these get very
large, they might be difficult to fabricate or control.
I propose an alternative to such a lens or mirror.

The so-called M2P2 drive has been proposed where a plasma is
"inflated" by a magnetic field that also traps the plasma. Int eh
M2P2 drive, the solar wind interacts with the plasma to produce
thrust. The M2P2 mag-sail can be VERY large, tens of Km or more.
Instead of using the M2P2 mag field/plasma sail to provide thrust, I
propose to use it as either a lens or collector of radiation.
As a lens, a plasma has an index of refraction that depends ont he
wavelength of the radiation and the plasma density. Such a lens would
have small index and probably very long focal length but could have
extremely large aperture. Such a lens could be placed in the outer
reaches of the solar system to direct more radiation from the power
source located near the sun onto the distant spacecraft. Such a lens
might also be used as a telescope collecting radiation from a distant
object for pure science. The lens could also be used to collect the
weak signal from the distant spacecraft. Of course, the lens needs a
power source and plasma media to replenish that that is lost as the
plasma leaks into space.
As a collector of radiation, teh trapped electrons in the plasma
interact with the incoming wave and gain energy and are collected and
the signal extracted from them. Obviously, the efficiency is
dependent on the plasma density.
Such lens systems (or even mirror systems) would have severe optical
aberrations and I am assuming this problem could be solved.


Any thoughts on this?
  #9  
Old September 13th 04, 07:54 PM
Mike Combs
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Default

"Carey Sublette" wrote in message
k.net...

So capturing the beamed energy, converting it to electricity, and using it
to power what is essentially a low energy (but extremely high current)
particle accelerator would provide efficient use.


If you ever get a chance, read "2081: A Hopeful View of the Human Future" by
Gerard K. O'Neill. He talks a bit about beamed-energy powered ion drives,
and projects them to be the drive of choice for passenger travel throughout
the system. I bet he went through the same chain of logic you just did.

--


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


  #10  
Old September 24th 04, 11:46 PM
Rodney Kelp
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Posts: n/a
Default

People like to think a star ship would look similar to the Enteprise in Star
Trek. It would probably look more like the Battlestar Galactica.

"Abdul Ahad" wrote in message
m...
I was toying with this idea for a *possible* futuristic voyage to
Alpha Centauri, with a big emphasis on water and life support resource
mining from comets and planetoids encountered along the journey:-


http://uk.geocities.com/aa_spaceagen...ropulsion.html


Specifically, I would like to know if anyone has thoughts on whether
an inter-vessel, ship-to-comet robotic attachment of some kind could
be built (with technology easy to visualise in the current era), which
scoops up and proceses the frozen material from comets into water and
hydrogen/oxygen for power and life support. The robotic arm would dig
into the exterior ice of the comet upon a gentle, speed-matched
docking rendezvous in-flight.

My starship concept demands a large scale structure extending perhaps
a few kilometres in length. Is our current materials science
technology adequate to build and operate something on that scale that
would be robust enough for the job to take the stresses involved where
the asteroid has a spin as well?

A further complexity is to rotate my asteroid to create artificial
gravity. As the robotic mining "arms" are going to be erected to
either side of the cylindrical asteroid body, upon contact with comets
the spin rate would slow down due to the added mass of the comet. If
the asteroid is say 10km long and 5km wide (and highly dense e.g. 2.9
grams/cm^3), and the cometary nucleus captured by the arms is say just
2 or 3km in diameter (with a density equivalent to that of water,
since its "icy"), would the spin rate of the asteroid slow very
drastically in such an encounter?

My last point is if my asteroid is rotating along a spin axis which
runs through the *length* of its body (through the core), what are my
options of "pitching" the asteroid from side to side without
disrupting the spin rate (and the artificial gravity that it
generates)? Would it be feasible to use *pulse* thrust at favourable
intervals if I wanted to turn the body around?

Thanks for all thoughts.
Abdul Ahad



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