for a given amount of fuel, an
astronaut can get to a distant destination in less of his own subjective >time than he would if we lived in plain Newtonian space.
John Savard <quadibloc@invalid.invalid> wrote or quoted:
for a given amount of fuel, an
astronaut can get to a distant destination in less of his own subjective
time than he would if we lived in plain Newtonian space.
Yeah, that's right. The guy wouldn't just head out far away in space,
he'd be jumping way ahead in time too! If he ever made it back to
Earth after that, what he'd find here is anybody's guess, pretty
much all up in the air. Kind of like in "Sleeper" by Woody Allen,
"Freezing Down" by Anders Bodelsen, or something like that . . .
The bright side, basically, is that for a given amount of fuel, an
astronaut can get to a distant destination in less of his own subjective >time than he would if we lived in plain Newtonian space.
In article <108jlti$3ssu6$1@dont-email.me>,
John Savard <quadibloc@invalid.invalid> wrote:
The bright side, basically, is that for a given amount of fuel, an >>astronaut can get to a distant destination in less of his own subjective >>time than he would if we lived in plain Newtonian space.
Alas, some external source of fuel is needed to get close
to c. A ramscoop (if that could be made to work), or some
sort of beamed propulsion. See, at (iirc) .87c, you've had
to put the rest mass of the ship into its kinetic energy,
and that's a tau factor of only .5. And by Newton, you need
twice as much energy as that, becuase half of it goes into the
reaction mass. To get up into really useful time dialation,
it gets worse .. much, much worse.
Some authors (G. David Nordley, for instance) have had
particle beam propulsions of various kinds. One hopes the
home guys keep sending the particle stream.
At one time it seemed like dozens of copies of _Freezing Down_ were in
every used book store...
I read it and have virtually no memory other than it had more sex
than the usual US SF novel of the time, and I didn't like it much.
I also think I felt it read oddly, which since it was a translation
makes sense.
In article<108jlti$3ssu6$1@dont-email.me>,
John Savard <quadibloc@invalid.invalid> wrote:
The bright side, basically, is that for a given amount of fuel, an astronaut can get to a distant destination in less of his own subjective time than he would if we lived in plain Newtonian space.
Alas, some external source of fuel is needed to get close
to c. A ramscoop (if that could be made to work), or some
sort of beamed propulsion. See, at (iirc) .87c, you've had
to put the rest mass of the ship into its kinetic energy,
and that's a tau factor of only .5. And by Newton, you need
twice as much energy as that, becuase half of it goes into the
reaction mass. To get up into really useful time dialation,
it gets worse .. much, much worse.
Some authors (G. David Nordley, for instance) have had
particle beam propulsions of various kinds. One hopes the
home guys keep sending the particle stream.
On Aug 26, 2025, Mike Van Pelt wrote
(in article <108lli0$cdoa$1@dont-email.me>):
In article<108jlti$3ssu6$1@dont-email.me>,
John Savard <quadibloc@invalid.invalid> wrote:
The bright side, basically, is that for a given amount of fuel, an
astronaut can get to a distant destination in less of his own subjective >> > time than he would if we lived in plain Newtonian space.
Alas, some external source of fuel is needed to get close
to c. A ramscoop (if that could be made to work), or some
sort of beamed propulsion. See, at (iirc) .87c, you've had
to put the rest mass of the ship into its kinetic energy,
and that's a tau factor of only .5. And by Newton, you need
twice as much energy as that, becuase half of it goes into the
reaction mass. To get up into really useful time dialation,
it gets worse .. much, much worse.
Some authors (G. David Nordley, for instance) have had
particle beam propulsions of various kinds. One hopes the
home guys keep sending the particle stream.
I can think of two dealbreakers:
1. How is the beam aimed? A minute fraction of an arc fraction at a >light-year’s range equals a miss by a few million kilometers.
2. Related to that... how wide does the beam spread at a light-year, and, >consequent to that, what’s the power density? At a range of a light-year >your power density is going to suck even if you put all of the power >delivered by the Sun into it.
On Aug 26, 2025, Mike Van Pelt wrote
(in article <108lli0$cdoa$1@dont-email.me>):
Some authors (G. David Nordley, for instance) have had
particle beam propulsions of various kinds. One hopes the
home guys keep sending the particle stream.
I can think of two dealbreakers:
1. How is the beam aimed? A minute fraction of an arc fraction at a >light-year’s range equals a miss by a few million kilometers.
2. Related to that... how wide does the beam spread at a light-year, and, >consequent to that, what’s the power density? At a range of a light-year >your power density is going to suck even if you put all of the power >delivered by the Sun into it.
In article<0001HW.2E5F3F9101ECC7B070000D75C38F@news.supernews.com>,
WolfFan <akwolffan@zoho.com> wrote:
On Aug 26, 2025, Mike Van Pelt wrote
(in article <108lli0$cdoa$1@dont-email.me>):
Some authors (G. David Nordley, for instance) have had
particle beam propulsions of various kinds. One hopes the
home guys keep sending the particle stream.
I can think of two dealbreakers:
1. How is the beam aimed? A minute fraction of an arc fraction at a light-year’s range equals a miss by a few million kilometers.
2. Related to that... how wide does the beam spread at a light-year, and, consequent to that, what’s the power density? At a range of a light-year your power density is going to suck even if you put all of the power delivered by the Sun into it.
In some Nordley's stories, the beam was "brilliant pebbles"
fired at relativistic speed from a really big mass driver.
They had enough tracking/steering to keep them on target, and
vaporized to plasma just short of the ship so its magnetic
sail could get a push from them.
On Aug 28, 2025, Mike Van Pelt wrote
(in article <108q2hg$1gbm1$1@dont-email.me>):
In article<0001HW.2E5F3F9101ECC7B070000D75C38F@news.supernews.com>,
WolfFan <akwolffan@zoho.com> wrote:
On Aug 26, 2025, Mike Van Pelt wrote
(in article <108lli0$cdoa$1@dont-email.me>):
Some authors (G. David Nordley, for instance) have had
particle beam propulsions of various kinds. One hopes the
home guys keep sending the particle stream.
I can think of two dealbreakers:
1. How is the beam aimed? A minute fraction of an arc fraction at a
light-year’s range equals a miss by a few million kilometers.
2. Related to that... how wide does the beam spread at a light-year, and, >>> consequent to that, what’s the power density? At a range of a light-year >>> your power density is going to suck even if you put all of the power
delivered by the Sun into it.
In some Nordley's stories, the beam was "brilliant pebbles"
fired at relativistic speed from a really big mass driver.
They had enough tracking/steering to keep them on target, and
vaporized to plasma just short of the ship so its magnetic
sail could get a push from them.
Oh, my. The cost of this project, already Quite Substantial, has just increased by several orders of magnitude. Not only are the ‘brilliant pebbles’ going to be Very Expensive, making and, especially, powering the mass drive is going to cost Big Bucks, lots and lots of Big Bucks. What’s this thing’s cyclic rate, and given that Newton’s Laws still work, how fast is it going to be moving in the opposite direction to the ‘brilliant pebbles’?
On Aug 28, 2025, Mike Van Pelt wrote
(in article <108q2hg$1gbm1$1@dont-email.me>):
In article<0001HW.2E5F3F9101ECC7B070000D75C38F@news.supernews.com>,
WolfFan <akwolffan@zoho.com> wrote:
On Aug 26, 2025, Mike Van Pelt wrote
(in article <108lli0$cdoa$1@dont-email.me>):
Some authors (G. David Nordley, for instance) have had
particle beam propulsions of various kinds. One hopes the
home guys keep sending the particle stream.
I can think of two dealbreakers:
1. How is the beam aimed? A minute fraction of an arc fraction at a
light-year’s range equals a miss by a few million kilometers.
2. Related to that... how wide does the beam spread at a light-year, and, >>> consequent to that, what’s the power density? At a range of a light-year >>> your power density is going to suck even if you put all of the power
delivered by the Sun into it.
In some Nordley's stories, the beam was "brilliant pebbles"
fired at relativistic speed from a really big mass driver.
They had enough tracking/steering to keep them on target, and
vaporized to plasma just short of the ship so its magnetic
sail could get a push from them.
Oh, my. The cost of this project, already Quite Substantial, has just increased by several orders of magnitude. Not only are the ‘brilliant pebbles’ going to be Very Expensive, making and, especially, powering the mass drive is going to cost Big Bucks, lots and lots of Big Bucks. What’s this thing’s cyclic rate, and given that Newton’s Laws still work, how fast is it going to be moving in the opposite direction to the ‘brilliant pebbles’?
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