I am doing some world building for a space game setting, and want to run
an idea past people.
My setting is not too distant future. I want easy surface to orbit launch to
explain why people are in space, which means using up a lot of energy
on each launch.
BUT once in space I want engines to be rather limited, so it isn't easy
to, say, divert asteroids into planets.
My idea is counter gravity, an updated version of HG Wells Cavorite, or
the liftwood in Space 1889. Not artificial gravity, but some kind of field
that INSERT HANDWAVING HERE creates an equal and opposite thrust reaction. So
within the gravity of a planet you get lots of thrust, near an asteroid very
little, and from a spaceship hull something only measurable in nanometres per
hour.
What am I missing? Would this make space travel economical? What else would it
be good for?
I think you'd end up using gravity wells to "sail" with. This would be an
adaptation of the current slingshot navigation used by spacecraft in the solar
system except once you have built up as much forward momentum as the gravity
well provides (I have no idea what the proper term is)
the pilot switches on his counter-gravity generator to get a further
boost.
My guess, and orbital mechanics are well out of my field (which is soda),
would be that this would result in a limited number of optimum
space-lanes (which would shift due to the way all the planets move in
relation to each other) but that exta-system travel would be barely more
efficient than before.
I think popping a counter-gravity engine on an asteroid would probably
prevent any Armageddon scenarios quite readily though...
Just some thoughts as my brain warms up this morning so the above may in fact
be nonsense...
Richard
________________________________
From: Gzg <gzg-bounces@firedrake.org> on behalf of Hugh Fisher
<laranzu@ozemail.com.au>
Sent: 08 November 2017 08:54
To: gzg@firedrake.org
Subject: World building: implications of counter gravity
I am doing some world building for a space game setting, and want to run an
idea past people.
My setting is not too distant future. I want easy surface to orbit launch to
explain why people are in space, which means using up a lot of energy on each
launch.
BUT once in space I want engines to be rather limited, so it isn't easy to,
say, divert asteroids into planets.
My idea is counter gravity, an updated version of HG Wells Cavorite, or the
liftwood in Space 1889. Not artificial gravity, but some kind of field that
INSERT HANDWAVING HERE creates an equal and opposite thrust reaction. So
within the gravity of a planet you get lots of thrust, near an asteroid very
little, and from a spaceship hull something only measurable in nanometres per
hour.
What am I missing? Would this make space travel economical? What else would it
be good for?
Years ago a mate and I did some thinking about various space drives for an RPG
setting we were dreaming up. We didn't think of counter gravity but we did
think of a magnetic drive using superconductors that could push against the
magnetic field of a planet to get lift and motion. So in Earth's gravity you
could lift off and achieve orbit relatively efficently but it dropped off
rapidly as you moved away. Wouldn't work for most bodies as there is no
significant magnetic field to push against but bodies like Jupiter it would
work a charm. This would also stop people throwing asteroids about as there is
no magnetic field for the asteroid to push against except that of the Sun
which would be pretty weak that far out. Also it would require a reasonable
amount of power run so that might be another reason to limit asteroid bombs.
Just a thought or two.
Tony.
> On 8/11/2017 8:02 PM, Richard Kirke wrote:
> an adaptation of the current slingshot navigation used by spacecraft
> prevent any Armageddon scenarios quite readily though...
------------------------------------------------------------------------
> *From:* Gzg <gzg-bounces@firedrake.org> on behalf of Hugh Fisher
> On Wed, Nov 08, 2017 at 07:54:48PM +1100, Hugh Fisher wrote:
Er, rockets and ion drives?
All the real-world engine tech we currently know or theorise about has
_either_ good thrust to weight _or_ good specific impulse (thrust per
fuel consumption). (Or neither, but never both.) To get off a planet you need
thrust to weight, but to go between planets you need specific impulse.
The main thing to avoid is reactionless drives, which IMO rapidly turn a
setting into Asteroid Bombardment War: every spaceship is a potential WMD.
The magnetic drive would work better as you could, presumably, control it via
how much power you feed into the unit and you wouldn't need lots of energy to
fight against it on the way down.
________________________________
From: Gzg <gzg-bounces@firedrake.org> on behalf of Tony Wilkinson
<twilko@ozemail.com.au>
Sent: 08 November 2017 09:40:59
To: gzg@firedrake.org
Subject: Re: World building: implications of counter gravity
Years ago a mate and I did some thinking about various space drives for an RPG
setting we were dreaming up. We didn't think of counter gravity but we did
think of a magnetic drive using superconductors that could push against the
magnetic field of a planet to get lift and motion. So in Earth's gravity you
could lift off and achieve orbit relatively efficently but it dropped off
rapidly as you moved away. Wouldn't work for most bodies as there is no
significant magnetic field to push against but bodies like Jupiter it would
work a charm. This would also stop people throwing asteroids about as there is
no magnetic field for the asteroid to push against except that of the Sun
which would be pretty weak that far out. Also it would require a reasonable
amount of power run so that might be another reason to limit asteroid bombs.
Just a thought or two.
Tony.
> On 8/11/2017 8:02 PM, Richard Kirke wrote:
I think you'd end up using gravity wells to "sail" with. This would be an
adaptation of the current slingshot navigation used by spacecraft in the solar
system except once you have built up as much forward momentum as the gravity
well provides (I have no idea what the proper term is)
the pilot switches on his counter-gravity generator to get a further
boost.
My guess, and orbital mechanics are well out of my field (which is soda),
would be that this would result in a limited number of optimum
space-lanes (which would shift due to the way all the planets move in
relation to each other) but that exta-system travel would be barely more
efficient than before.
I think popping a counter-gravity engine on an asteroid would probably
prevent any Armageddon scenarios quite readily though...
Just some thoughts as my brain warms up this morning so the above may in fact
be nonsense...
Richard
________________________________
From: Gzg <gzg-bounces@firedrake.org><mailto:gzg-bounces@firedrake.org>
on behalf of Hugh Fisher
<laranzu@ozemail.com.au><mailto:laranzu@ozemail.com.au>
Sent: 08 November 2017 08:54
To: gzg@firedrake.org<mailto:gzg@firedrake.org>
Subject: World building: implications of counter gravity
I am doing some world building for a space game setting, and want to run an
idea past people.
My setting is not too distant future. I want easy surface to orbit launch to
explain why people are in space, which means using up a lot of energy on each
launch.
BUT once in space I want engines to be rather limited, so it isn't easy to,
say, divert asteroids into planets.
My idea is counter gravity, an updated version of HG Wells Cavorite, or the
liftwood in Space 1889. Not artificial gravity, but some kind of field that
INSERT HANDWAVING HERE creates an equal and opposite thrust reaction. So
within the gravity of a planet you get lots of thrust, near an asteroid very
little, and from a spaceship hull something only measurable in nanometres per
hour.
What am I missing? Would this make space travel economical? What else would it
be good for?
If you have a strong light rigid material that can contain a vacuum you could
get to the edge of space by buoyancy.
The material might also be useful for solar sails. Add some ion drives
(solar powered) and regular rockets for final orbital insertion and you may
have a cheaper system.
Andy.
________________________________
From: Gzg <gzg-bounces@firedrake.org> on behalf of Tony Wilkinson
<twilko@ozemail.com.au>
Sent: Wednesday, November 8, 2017 4:40 AM
To: gzg@firedrake.org
Subject: Re: World building: implications of counter gravity
Years ago a mate and I did some thinking about various space drives for an RPG
setting we were dreaming up. We didn't think of counter gravity but we did
think of a magnetic drive using superconductors that could push against the
magnetic field of a planet to get lift and motion. So in Earth's gravity you
could lift off and achieve orbit relatively efficently but it dropped off
rapidly as you moved away. Wouldn't work for most bodies as there is no
significant magnetic field to push against but bodies like Jupiter it would
work a charm. This would also stop people throwing asteroids about as there is
no magnetic field for the asteroid to push against except that of the Sun
which would be pretty weak that far out. Also it would require a reasonable
amount of power run so that might be another reason to limit asteroid bombs.
Just a thought or two.
Tony.
> On 8/11/2017 8:02 PM, Richard Kirke wrote:
I think you'd end up using gravity wells to "sail" with. This would be an
adaptation of the current slingshot navigation used by spacecraft in the solar
system except once you have built up as much forward momentum as the gravity
well provides (I have no idea what the proper term is)
the pilot switches on his counter-gravity generator to get a further
boost.
My guess, and orbital mechanics are well out of my field (which is soda),
would be that this would result in a limited number of optimum
space-lanes (which would shift due to the way all the planets move in
relation to each other) but that exta-system travel would be barely more
efficient than before.
I think popping a counter-gravity engine on an asteroid would probably
prevent any Armageddon scenarios quite readily though...
Just some thoughts as my brain warms up this morning so the above may in fact
be nonsense...
Richard
________________________________
From: Gzg <gzg-bounces@firedrake.org><mailto:gzg-bounces@firedrake.org>
on behalf of Hugh Fisher
<laranzu@ozemail.com.au><mailto:laranzu@ozemail.com.au>
Sent: 08 November 2017 08:54
To: gzg@firedrake.org<mailto:gzg@firedrake.org>
Subject: World building: implications of counter gravity
I am doing some world building for a space game setting, and want to run an
idea past people.
My setting is not too distant future. I want easy surface to orbit launch to
explain why people are in space, which means using up a lot of energy on each
launch.
BUT once in space I want engines to be rather limited, so it isn't easy to,
say, divert asteroids into planets.
My idea is counter gravity, an updated version of HG Wells Cavorite, or the
liftwood in Space 1889. Not artificial gravity, but some kind of field that
INSERT HANDWAVING HERE creates an equal and opposite thrust reaction. So
within the gravity of a planet you get lots of thrust, near an asteroid very
little, and from a spaceship hull something only measurable in nanometres per
hour.
What am I missing? Would this make space travel economical? What else would it
be good for?
If you have a strong light rigid material that can contain a vacuum you could
get to the edge of space by buoyancy.
The material might also be useful for solar sails. Add some ion drives
(solar powered) and regular rockets for final orbital insertion and you may
have a cheaper system.
Andy.
________________________________
From: Gzg <gzg-bounces@firedrake.org> on behalf of Tony Wilkinson
<twilko@ozemail.com.au>
Sent: Wednesday, November 8, 2017 4:40 AM
To: gzg@firedrake.org
Subject: Re: World building: implications of counter gravity
Years ago a mate and I did some thinking about various space drives for an RPG
setting we were dreaming up. We didn't think of counter gravity but we did
think of a magnetic drive using superconductors that could push against the
magnetic field of a planet to get lift and motion. So in Earth's gravity you
could lift off and achieve orbit relatively efficently but it dropped off
rapidly as you moved away. Wouldn't work for most bodies as there is no
significant magnetic field to push against but bodies like Jupiter it would
work a charm. This would also stop people throwing asteroids about as there is
no magnetic field for the asteroid to push against except that of the Sun
which would be pretty weak that far out. Also it would require a reasonable
amount of power run so that might be another reason to limit asteroid bombs.
Just a thought or two.
Tony.
> On 8/11/2017 8:02 PM, Richard Kirke wrote:
I think you'd end up using gravity wells to "sail" with. This would be an
adaptation of the current slingshot navigation used by spacecraft in the solar
system except once you have built up as much forward momentum as the gravity
well provides (I have no idea what the proper term is)
the pilot switches on his counter-gravity generator to get a further
boost.
My guess, and orbital mechanics are well out of my field (which is soda),
would be that this would result in a limited number of optimum
space-lanes (which would shift due to the way all the planets move in
relation to each other) but that exta-system travel would be barely more
efficient than before.
I think popping a counter-gravity engine on an asteroid would probably
prevent any Armageddon scenarios quite readily though...
Just some thoughts as my brain warms up this morning so the above may in fact
be nonsense...
Richard
________________________________
From: Gzg <gzg-bounces@firedrake.org><mailto:gzg-bounces@firedrake.org>
on behalf of Hugh Fisher
<laranzu@ozemail.com.au><mailto:laranzu@ozemail.com.au>
Sent: 08 November 2017 08:54
To: gzg@firedrake.org<mailto:gzg@firedrake.org>
Subject: World building: implications of counter gravity
I am doing some world building for a space game setting, and want to run an
idea past people.
My setting is not too distant future. I want easy surface to orbit launch to
explain why people are in space, which means using up a lot of energy on each
launch.
BUT once in space I want engines to be rather limited, so it isn't easy to,
say, divert asteroids into planets.
My idea is counter gravity, an updated version of HG Wells Cavorite, or the
liftwood in Space 1889. Not artificial gravity, but some kind of field that
INSERT HANDWAVING HERE creates an equal and opposite thrust reaction. So
within the gravity of a planet you get lots of thrust, near an asteroid very
little, and from a spaceship hull something only measurable in nanometres per
hour.
What am I missing? Would this make space travel economical? What else would it
be good for?
If you have a strong light rigid material that can contain a vacuum you could
get to the edge of space by buoyancy.
The material might also be useful for solar sails. Add some ion drives
(solar powered) and regular rockets for final orbital insertion and you may
have a cheaper system.
Andy.
________________________________
From: Gzg <gzg-bounces@firedrake.org> on behalf of Tony Wilkinson
<twilko@ozemail.com.au>
Sent: Wednesday, November 8, 2017 4:40 AM
To: gzg@firedrake.org
Subject: Re: World building: implications of counter gravity
Years ago a mate and I did some thinking about various space drives for an RPG
setting we were dreaming up. We didn't think of counter gravity but we did
think of a magnetic drive using superconductors that could push against the
magnetic field of a planet to get lift and motion. So in Earth's gravity you
could lift off and achieve orbit relatively efficently but it dropped off
rapidly as you moved away. Wouldn't work for most bodies as there is no
significant magnetic field to push against but bodies like Jupiter it would
work a charm. This would also stop people throwing asteroids about as there is
no magnetic field for the asteroid to push against except that of the Sun
which would be pretty weak that far out. Also it would require a reasonable
amount of power run so that might be another reason to limit asteroid bombs.
Just a thought or two.
Tony.
> On 8/11/2017 8:02 PM, Richard Kirke wrote:
I think you'd end up using gravity wells to "sail" with. This would be an
adaptation of the current slingshot navigation used by spacecraft in the solar
system except once you have built up as much forward momentum as the gravity
well provides (I have no idea what the proper term is)
the pilot switches on his counter-gravity generator to get a further
boost.
My guess, and orbital mechanics are well out of my field (which is soda),
would be that this would result in a limited number of optimum
space-lanes (which would shift due to the way all the planets move in
relation to each other) but that exta-system travel would be barely more
efficient than before.
I think popping a counter-gravity engine on an asteroid would probably
prevent any Armageddon scenarios quite readily though...
Just some thoughts as my brain warms up this morning so the above may in fact
be nonsense...
Richard
________________________________
From: Gzg <gzg-bounces@firedrake.org><mailto:gzg-bounces@firedrake.org>
on behalf of Hugh Fisher
<laranzu@ozemail.com.au><mailto:laranzu@ozemail.com.au>
Sent: 08 November 2017 08:54
To: gzg@firedrake.org<mailto:gzg@firedrake.org>
Subject: World building: implications of counter gravity
I am doing some world building for a space game setting, and want to run an
idea past people.
My setting is not too distant future. I want easy surface to orbit launch to
explain why people are in space, which means using up a lot of energy on each
launch.
BUT once in space I want engines to be rather limited, so it isn't easy to,
say, divert asteroids into planets.
My idea is counter gravity, an updated version of HG Wells Cavorite, or the
liftwood in Space 1889. Not artificial gravity, but some kind of field that
INSERT HANDWAVING HERE creates an equal and opposite thrust reaction. So
within the gravity of a planet you get lots of thrust, near an asteroid very
little, and from a spaceship hull something only measurable in nanometres per
hour.
What am I missing? Would this make space travel economical? What else would it
be good for?
If you have a strong light rigid material that can contain a vacuum you could
get to the edge of space by buoyancy.
The material might also be useful for solar sails. Add some ion drives
(solar powered) and regular rockets for final orbital insertion and you may
have a cheaper system.
Andy.
________________________________
From: Gzg <gzg-bounces@firedrake.org> on behalf of Tony Wilkinson
<twilko@ozemail.com.au>
Sent: Wednesday, November 8, 2017 4:40 AM
To: gzg@firedrake.org
Subject: Re: World building: implications of counter gravity
Years ago a mate and I did some thinking about various space drives for an RPG
setting we were dreaming up. We didn't think of counter gravity but we did
think of a magnetic drive using superconductors that could push against the
magnetic field of a planet to get lift and motion. So in Earth's gravity you
could lift off and achieve orbit relatively efficently but it dropped off
rapidly as you moved away. Wouldn't work for most bodies as there is no
significant magnetic field to push against but bodies like Jupiter it would
work a charm. This would also stop people throwing asteroids about as there is
no magnetic field for the asteroid to push against except that of the Sun
which would be pretty weak that far out. Also it would require a reasonable
amount of power run so that might be another reason to limit asteroid bombs.
Just a thought or two.
Tony.
> On 8/11/2017 8:02 PM, Richard Kirke wrote:
I think you'd end up using gravity wells to "sail" with. This would be an
adaptation of the current slingshot navigation used by spacecraft in the solar
system except once you have built up as much forward momentum as the gravity
well provides (I have no idea what the proper term is)
the pilot switches on his counter-gravity generator to get a further
boost.
My guess, and orbital mechanics are well out of my field (which is soda),
would be that this would result in a limited number of optimum
space-lanes (which would shift due to the way all the planets move in
relation to each other) but that exta-system travel would be barely more
efficient than before.
I think popping a counter-gravity engine on an asteroid would probably
prevent any Armageddon scenarios quite readily though...
Just some thoughts as my brain warms up this morning so the above may in fact
be nonsense...
Richard
________________________________
From: Gzg <gzg-bounces@firedrake.org><mailto:gzg-bounces@firedrake.org>
on behalf of Hugh Fisher
<laranzu@ozemail.com.au><mailto:laranzu@ozemail.com.au>
Sent: 08 November 2017 08:54
To: gzg@firedrake.org<mailto:gzg@firedrake.org>
Subject: World building: implications of counter gravity
I am doing some world building for a space game setting, and want to run an
idea past people.
My setting is not too distant future. I want easy surface to orbit launch to
explain why people are in space, which means using up a lot of energy on each
launch.
BUT once in space I want engines to be rather limited, so it isn't easy to,
say, divert asteroids into planets.
My idea is counter gravity, an updated version of HG Wells Cavorite, or the
liftwood in Space 1889. Not artificial gravity, but some kind of field that
INSERT HANDWAVING HERE creates an equal and opposite thrust reaction. So
within the gravity of a planet you get lots of thrust, near an asteroid very
little, and from a spaceship hull something only measurable in nanometres per
hour.
What am I missing? Would this make space travel economical? What else would it
be good for?
The question that popped into my mind is whether you could use your drive to
actually generate thrust, or if it's only good for getting away from the
'strongest' gravitational field. Otherwise, to actually get somewhere
once you're in space would be a struggle - getting to orbit is easy, but
how would you generate the delta-V to end up somewhere else? (If memory
serves, Space 1889 liftwood ships had ether sails to generate this propulsive
force, and I think there was some handwaving somewhere so journeys to Mars et
al took weeks and months, not years.)
I suppose you could set it up as 'dial a gravity field' i.e. you setup
repulsion against whatever gravity source you want, and so you could probably
find something aligned to whatever vector you want, but this starts to get
real handwaving even for handwaving.:)
JGH
> On 2017-11-08 03:54, Hugh Fisher wrote:
So
> within the gravity of a planet you get lots of thrust, near an
Don't recall from the actual book, but from the movie First Men on the Moon,
the Cavorite did use a 'directional' gravity attraction, blocking the Earth's
and using the moon's. Did ignore the whole inverse square thingy, but I can be
picky. Might help avoid using it AS a thrust, though. As for slingshot, as
there's as much gravity on both approach and withdrawal from a body, so that
you can use to increase or brake, depending on moving with or against the body
as you pass. Cutting the gravity on either leg would be HUGE. I think. Can't
do the math. Can't even do the math as to whether 'as much gravity on both' is
true as you are accelerating as you approach, and decelerating after you've
passed. After half a century, calculus is a bit rusty.
Combining a launch system, say a canon or XL-5's trolley, with gravity
blocking would get something off the ground without lot of reaction material.
Does that help?
Course, the whole Hyperloop talk has re-energized an idea I had for
reusing a long distance tube system for launches...
> On 08/11/2017 08:54, Hugh Fisher wrote:
If all your Handwavium Drive does is produce an equal and opposite force
to the local gravity vector, then that just means that you've negated
gravity -- all gravity -- on your ship. So you won't stay in orbit, for
instance, which is great for leaving orbit (but not so good for getting into
it), but tricky if you actually want to go somewhere, because you'll have to
be pointing in exactly the right direction when you turn it on, and it won't
speed you up (or slow you down) at all. This means that your flight path, for
want of a better word, is going to be a straight line rather than the usual
conic section, so it's shorter but has its own problems. Left to itself, your
ship will travel with the velocity it had when the HD was activated, which
isn't going to be very fast in interplanetary terms. You also won't be able to
go from place A to place B unless they're in the correct positions, so there
will be small launch windows for the trip and large periods when "you can't
get
there from here" -- not least of which will be the times when there's
something else in the way (like the Sun)! You're really going to need a
manoeuvring drive to turn the ship and alter its velocity vector until it's
pointing at the desired destination (and maybe to boost the speed a
bit); kinda reminds me of /BattleFleet/ /Mars/, where you could expend
manoeuvre fuel to shorten interplanetary trips that were predominantly
powered by low-thrust ion drives.
Unless, of course, you can throttle the thing and/or vector it. If what
the magnitude of the local gravity field does is control the magnitude of the
thrust that you can produce without putting restrictions on where
it's pointing, and the thrust can be greater or lesser than the local gravity,
then you've got something that's not unlike a rocket with
endless fuel -- just one where the thrust produced is smaller out in
space than near a mass. This is great for manoeuvres like slingshots
because the thrust is at its maximum right where you want it to be -- at
and near "perigee" of the body you're slingshotting around! So you do most of
your manoeuvring near planetary masses, where you have the
thrust, and you don't have much delta-V out in the black, but may have
enough for course corrections en route. Of course, any thrust at all can
build up over the sort of distances we're talking about, so your trip time
will be reduced from a pure Hohmann orbit, and with enough thrust at the ends
(near the big masses), you can go almost any time you like.
That works fine for planets, but you'd have to run some numbers to see how the
HD would work with smaller masses like, say, the asteroids.
Jerry Pournelle once worked out that the semi-traditional idea of
Belters zipping around the asteroids but never entering planetary gravity
wells ("holes", as Larry Niven called them) doesn't really make
sense because the delta-V needed to move between the bigger asteroids is
pretty much the same as is involved in planetary launches and landings.
With the HD, though, you wouldn't have the thrust (and hence delta-V)
near an asteroid as you would around a planet, so Belters might be out of
luck. Of course, he also came up with the idea of replacing a Belt
civilsation with one based on the moons of Jupiter, where the delta-V
requirements are much lower, so the HD might well suit that setting rather
neatly.
On Wed, 08 Nov 2017 23:16:39 +1100, Steve Gill <Steve@caws.demon.co.uk>
wrote:
> The magnetic drive would work better as you could, presumably, control
> it via how much power you feed into the unit and you wouldn't need
Liftwood in Space 1889 was directional so you could reduce the countergrav
effect to descend or land by tilting the panels. Which fitted well for that
setting, not so much for a plausible future.
Hmm. Since it's a field, there's some kind of generator powering it. (And
not just a couple of AA batteries - don't want to make it too easy.)
Turning down the power reduces the effect.
On Thu, 09 Nov 2017 01:17:55 +1100, Jerry Han <ghoti221@gmail.com>
wrote:
> The question that popped into my mind is whether you could use your
Definitely only for pushing away from the strongest gravity field. Add in an
inverse square law and yes that's how I want it to work, getting into orbit is
easy but after that it's back to rockets.
> If all your Handwavium Drive does is produce an equal and opposite
The HD drive is not intended to be the only drive in use. My thought was that
it's a launch technology only. Interplanetary spaceships would be built in
orbit and never land on planets, so they'd use a different drive technology
altogether.
> Unless, of course, you can throttle the thing and/or vector it. If
I'm thinking throttle magnitude but not vector.
Originally I'd intended that space travel, as opposed to launch, would need
rockets and/or ion drives. It hadn't occurred to me that it would work
for interplanetary travel as a very low thrust drive too.
> That works fine for planets, but you'd have to run some numbers to see
I'm fine with the HD only working well with planets. The setting I'm thinking
of is a plausible near future / RocketPunk style (well, baring the one
miracle allowed that is the HD drive itself) where there are still rockets
(possibly nuclear now we can launch heavier payloads) and ion drives.
Sorry if this is duplicated; not sure if it came through the first time.
One thing I failed to point out was that simply 'turning off gravity' would
cause a limited 'lift' from inertia, the false 'centripetal' force. The fact
that a planet is spinning means that a body tends to move away unless gravity
holds it 'down'. Some time in the last few years, Frank Chadwick suggested it
as a form of liftwood propulsion. Liftwood allows the craft to 'rise', and
then shutting off the liftwood panels would cause the craft to 'fall',
allowing it to use a form of gliding to move. The 'rise' is actually so slow
that winds would be far more a cause of moving than the
up-and-down, so he was being a bit silly trying to use the violation of
conservation of momentum for horizontal movement, especially on the even
smaller Mars, but I didn't try to dissuade him.
I think elsewhere, I even mentioned my take was that sail craft could remain
at the turbulent boundary between different wind flows and use the
differential for directed movement.
Still, it IS a 'rise' from the surface. All the quotes are from the handwavium
involved. Doug
On Wednesday, November 8, 2017, 9:21:29 AM CST, Doug Evans via Gzg
> <gzg@firedrake.org> wrote:
Don't recall from the actual book, but from the movie First Men on the Moon,
the Cavorite did use a 'directional' gravity attraction, blocking the Earth's
and using the moon's. Did ignore the whole inverse square thingy, but I can be
picky. Might help avoid using it AS a thrust, though. As for slingshot, as
there's as much gravity on both approach and withdrawal from a body, so that
you can use to increase or brake, depending on moving with or against the body
as you pass. Cutting the gravity on either leg would be HUGE. I think. Can't
do the math. Can't even do the math as to whether 'as much gravity on both' is
true as you are accelerating as you approach, and decelerating after you've
passed. After half a century, calculus is a bit rusty.
Combining a launch system, say a canon or XL-5's trolley, with gravity
blocking would get something off the ground without lot of reaction material.
Does that help?
Course, the whole Hyperloop talk has re-energized an idea I had for
reusing a long distance tube system for launches...
My first thought was to go in a different direction - Space Elevator.
https://www.extremetech.com/extreme/176625-60000-miles-up-geostationary-
space-elevator-could-be-built-by-2035-says-new-study
The Space Elevator would be able to get people, supplies, etc into orbit
with a lot less effort than disposable rockets, don't need as much magic
handwavum to work, and allow you to keep rocket engines less powerful so
they can't zip all over the solar system.
Dean
> On 11/8/2017 2:54 AM, Hugh Fisher wrote:
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> On Wednesday, 8 November 2017 19:54:48 GMT Hugh Fisher wrote:
What I use in my own setting are repulsor fields (terminology taken from Star
Wars), which are a sort of reverse tractor beam. This is what is used by
flying cars, 'grav tanks' and the like, and is also used by space craft for
take off and landing.
It works by pushing against another mass (just like an SF tractor beam pulls
against a mass). Vehicles can use it to push against a planet. They can also
use them to push against incoming missiles in a defensive fashion. They can't
use them once they're actually in empty space, but could use it against an
asteroid.
They are relatively short range (especially at low tech levels, where they are
limited to a few tens of metres), so many space craft only use them for final
approach so they have better fine grained control on landing/take off
without burning the landing zone. They tend to have problems on bridges as
well (which
don't have sufficient mass to 'push' against - the push is against
actual matter, not against the gravitational field).
Even high tech craft tend to be limited to a few kilometres altitude with this
technology, so then switch to main drives to get up to orbital velocity. A few
specialist craft can reach tens of kilometres.
You could use something similar, maybe increasing the range, but even being
able to 'hover' above the thickest part of the atmosphere would be enough to
make it a lot easier for a primary drive to get a ship into orbit.
On Thu, 09 Nov 2017 15:08:32 +1100, Star Ranger <dean@star-ranger.com>
wrote:
> My first thought was to go in a different direction - Space Elevator.
https://www.extremetech.com/extreme/176625-60000-miles-up-geostationary-
space-elevator-could-be-built-by-2035-says-new-study
> The Space Elevator would be able to get people, supplies, etc into
Space elevators aren't space ships though. They're very big and limited in
possible locations, so only one or a handful per planet. I'd prefer for game
design purposes something that's about as affordable as a current day
Delta/Soyuz/Ariane rocket.
(And yes I'm aware that rockets also benefit from being launched near the
equator - but as Baikonur demonstrates, it's not essential.)