speaking of comets

At 2346278400000 miles Proxima Centauri (using 4 x 5,865,696,000,000 miles
(9,460,800,000,000 kilometers)) might be reached if a chain of "spaced out"
asteroids could be found.




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on Sat, 29 Nov 2003 10:51:04 -0500, Lynndel Humphreys sez:

` Was thinking more along the lines of harpooning a large deep space comet or
` asteroid. After attaching, it could be reeled onto the surface. BTW, what
` asteroids would fit the requirements? --really deep space One advantage
` would be unlike Voyager it might eventually return if in a "galactic orbit".
` Not held by the sun but by the galaxy itself. Probably would need an
` asteroid relay system.
` --with thousand(s) year energy source.


You are failing to appreciate the magnitude of the difference in
velocities. If something was travelling close enough to your
velocity that you could actually "harpoon" it, you are already
pretty much going the same speed. Think more in terms of the
velocity differential typically being such that any harpoon you
tried to use which actually contacted the passing object would be
instantly vapourized by the impact.

With considerable effort you might be able to get a slightly
different result, but even were you to launch some sort of
harpoon with the required velocity, the mass of cable required
- we're talking several kilometres per _second_ here - strong
enough to carry your probe along, would be impossibly large
to manage. See, the longer it takes for your harpoon to get
up to speed, the farther the cable has to stretch. The more
cable you need, the more mass it weighs, the more mass which
has to be accelerated along with the harpoon, so the longer
it takes the harpoon to get up to speed, etc etc. And that's
not to even begin to talk about the engineering required to
slowly engage a clutch on a cable paying out at multiple
kilometres per second, so that the cable starts to pull the
probe along rather than simply snapping or destroying the
probe with explosive acceleration.

--
================================================== ========================
Pete Vincent
Disclaimer: all I know I learned from reading Usenet.

on Sat, 29 Nov 2003 10:51:04 -0500, Lynndel Humphreys sez:

` Was thinking more along the lines of harpooning a large deep space comet or
` asteroid. After attaching, it could be reeled onto the surface. BTW, what
` asteroids would fit the requirements? --really deep space One advantage
` would be unlike Voyager it might eventually return if in a "galactic orbit".
` Not held by the sun but by the galaxy itself. Probably would need an
` asteroid relay system.
` --with thousand(s) year energy source.


You are failing to appreciate the magnitude of the difference in
velocities. If something was travelling close enough to your
velocity that you could actually "harpoon" it, you are already
pretty much going the same speed. Think more in terms of the
velocity differential typically being such that any harpoon you
tried to use which actually contacted the passing object would be
instantly vapourized by the impact.

With considerable effort you might be able to get a slightly
different result, but even were you to launch some sort of
harpoon with the required velocity, the mass of cable required
- we're talking several kilometres per _second_ here - strong
enough to carry your probe along, would be impossibly large
to manage. See, the longer it takes for your harpoon to get
up to speed, the farther the cable has to stretch. The more
cable you need, the more mass it weighs, the more mass which
has to be accelerated along with the harpoon, so the longer
it takes the harpoon to get up to speed, etc etc. And that's
not to even begin to talk about the engineering required to
slowly engage a clutch on a cable paying out at multiple
kilometres per second, so that the cable starts to pull the
probe along rather than simply snapping or destroying the
probe with explosive acceleration.

--
================================================== ========================
Pete Vincent
Disclaimer: all I know I learned from reading Usenet.

Lynndel Humphreys wrote:
At 2346278400000 miles Proxima Centauri (using 4 x 5,865,696,000,000 miles
(9,460,800,000,000 kilometers)) might be reached if a chain of "spaced out"
asteroids could be found.




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The Oort cloud is thought to extend for a long ways. I like to imagine
humankind spreading out from the solar system just as a colony of mold
will spread out from a single slice to neighboring slices of bread.

But to use bodies past 5 A.U. or so I'd think you would need a better
energy source. If practical fusion power is devised, maybe humans could
colonize the Trojans, Kuiper, Oort and beyond.



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

Lynndel Humphreys wrote:
At 2346278400000 miles Proxima Centauri (using 4 x 5,865,696,000,000 miles
(9,460,800,000,000 kilometers)) might be reached if a chain of "spaced out"
asteroids could be found.




-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

The Oort cloud is thought to extend for a long ways. I like to imagine
humankind spreading out from the solar system just as a colony of mold
will spread out from a single slice to neighboring slices of bread.

But to use bodies past 5 A.U. or so I'd think you would need a better
energy source. If practical fusion power is devised, maybe humans could
colonize the Trojans, Kuiper, Oort and beyond.



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

"Lynndel Humphreys" wrote in message ...

Not held by the sun but by the galaxy itself. Probably would need an
asteroid relay system.

Lynndel, do you understand that asteroids do not get any free
transport?

By the time you harpoon an asteroid, you've basically spent the fuel
necessary to travel in the same direction and speed as the asteroid.
You'll be flying in formation with the asteroid before you land on it.
Landing on it gives you no boost in speed, not like hopping on a
passing bus.

Mike Miller, Materials Engineer

"Lynndel Humphreys" wrote in message ...

Not held by the sun but by the galaxy itself. Probably would need an
asteroid relay system.

Lynndel, do you understand that asteroids do not get any free
transport?

By the time you harpoon an asteroid, you've basically spent the fuel
necessary to travel in the same direction and speed as the asteroid.
You'll be flying in formation with the asteroid before you land on it.
Landing on it gives you no boost in speed, not like hopping on a
passing bus.

Mike Miller, Materials Engineer

"Lynndel Humphreys" wrote in message
...
Was thinking more along the lines of harpooning a large deep space
comet or asteroid. After attaching, it could be reeled onto the
surface. BTW, what asteroids would fit the requirements?

The deltaV between the vehicle and the comet or asteroid has to be
very small, like under 1 km/sec. A tether for harpooning just would
not be reasonable for much more than this (too heavy relative to
vehicle). You want the asteroid going in the direction that you want
to go. A random comet may be doing more like 20 km/sec and not the
way you want to go. Outside the asteroid belt it would take too long
for another suitable asteroid to come along.

-- Vince

"Lynndel Humphreys" wrote in message
...
Was thinking more along the lines of harpooning a large deep space
comet or asteroid. After attaching, it could be reeled onto the
surface. BTW, what asteroids would fit the requirements?

The deltaV between the vehicle and the comet or asteroid has to be
very small, like under 1 km/sec. A tether for harpooning just would
not be reasonable for much more than this (too heavy relative to
vehicle). You want the asteroid going in the direction that you want
to go. A random comet may be doing more like 20 km/sec and not the
way you want to go. Outside the asteroid belt it would take too long
for another suitable asteroid to come along.

-- Vince

Vincent Cate wrote:

"Lynndel Humphreys" wrote in message
...
Was thinking more along the lines of harpooning a large deep space
comet or asteroid. After attaching, it could be reeled onto the
surface. BTW, what asteroids would fit the requirements?

The deltaV between the vehicle and the comet or asteroid has to be
very small, like under 1 km/sec. A tether for harpooning just would
not be reasonable for much more than this (too heavy relative to
vehicle). You want the asteroid going in the direction that you want
to go. A random comet may be doing more like 20 km/sec and not the
way you want to go. Outside the asteroid belt it would take too long
for another suitable asteroid to come along.

-- Vince

Indeed. If whales were hypersonic....well, you see the problem, even
if you got a successful hit...


--

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