Alternate Ship Design Systems

[far-trader]

Further, in the realism mode and discarding "magic" gravity manipulation, you can forget turret mounted and hand held lasers and energy weapons. And space combat at anything more than a light second is likely going to be impossible without fast self guided/tracking missiles. It'll be a whole new ball game.

Laser and energy weapons are going to be huge, delicate, and very hard to aim. They'll also do little damage unless held on target for a while.

Anyway, just a couple more thoughts.

 

[Jamus]

ya know, I just google searched anti-grav and found a couple hundred sites discussing how it is done... I guess its drive plates on my ships after all.

I do however still believe gravitics should be represented in the ship design rules as a separate componant with its own tonnage/space req and its own power req.

I also feel it should be on the ship damage tables.


<grumble grumble>

Magic I say!!!

 

[far-trader]

<edit>

Originally posted by Jamus:
ya know, I just google searched anti-grav and found a couple hundred sites discussing how it is done... I guess its drive plates on my ships after all.

believe half of what you see Son, and none of what you read

Originally posted by Jamus:


I do however still believe gravitics should be represented in the ship design rules as a separate componant with its own tonnage/space req and its own power req.

I also feel it should be on the ship damage tables.

Then I'm sure you know TNE/FF&S is maybe your best choice

Originally posted by Jamus:
<grumble grumble>

Magic I say!!!

Of course, with the old caveat that any technology sufficiently advanced will be indistinguishable from magic. Hey, that means you're right!

Witches, all Engineers are Witches!

 

[Straybow]

Originally posted by Anthony:
Well, they could if those calculations were correct, which they aren't. The power requirement for applying 5 million newtons thrust (500T mass at 1G) is 5 MW x velocity relative to what you are pushing on. Your solution is only correct if what you are pushing on has a zero velocity relative to the ship at the beginning of every second, which is a pretty unlikely state of affairs.

You are trying to apply a reaction mass equation based on conservation of momentum. In theory a generated grav field would be exchanging momentum with the rest of the universe instead of a little bit of exhaust mass.

If the 500T ship is falling unpowered toward a 1G planet surface, what thrust is being applied? The answer is, "None." If the 500T ship is using grav tech to accelerate at 1G in an arbitrary direction, what thrust is being applied? Again: "None." Grav isn't thrust, it is reactionless.

 

[TKalbfus]

The Far Trader said,

"Well if its realism you want then you're going to have to accept your alternate maneuver drives are maybe 10% as powerful as thruster plates, and that's being generous. So you'll be putting around at fractions of a Gee.
"

Ever hear of Project Orion? The original idea was for a spaceship propelled by atomic bomb explosions to take off from the surface of the Earth. In fact a metal sphere was propelled skyward by a nuclear explosion in an atomic bomb test. That metal sphere had to undergo an accelleration of greater than 1-G for that to happen, so in principle a nuclear reaction can propell a spacecraft at accelerations of greater than one gee. This is called a pulse rocket. The way this works is that materials can survive higher temperatures if they experience them only briefly. A pulse fusion rocket creates a nuclear explosion that comes in contact with a solid rocket nozzle that ablates a minimum amount of mass to dissapate heat where a steady state fusion rocket would melt, this is because in between explosions the rocket nozzle has time to cool. There are various ways to go about this, one is a laser ignition system, glass pellets with fusion fuel inside are often used in this process, the pellets are imploded and heated by lasers, but its also possible to do this with collisions, electron beams, or even brief pinches by magnetic fields. You see the fusion reaction is brief and it is the explosion that comes afterwards that propells the ship. A Traveller fusion rocket can substitute liquid hydrogen droplets ejected into the reaction chamber and imploded by lasers. This should achieve higher accelerations than the steady state magnetic confinement fusion that you probably envision.

And of course you don't have artificial gravity either so your ship will need spin gravity or the crew and passengers will develop severe health problems on long trips.

"gravity" can be achieved by accelerating the ship at a steady 1-G. The fusion drive only has to operate long enough to get to 100 planetary diameters to engage the Jump Drive, then it has to operate long enough to slow down the space craft upon planetary approach. A week spent in zero-gravity in jump space is not going to hurt anybody, so there's no real need for "magic" artificial gravity generators, as the travelers won't spend enough time in space for their muscles to weaken or their bones to demineralize.

 

[Anthony]

Originally posted by Straybow:
You are trying to apply a reaction mass equation based on conservation of momentum.

No, I'm not, I'm simply assuming that the drive is pushing on something. By definition, Power = Force * Velocity.

If the 500T ship is falling unpowered toward a 1G planet surface, what thrust is being applied?

The 500T ship is being subjected to a force of roughly 5 million newtons, and is busy exchanging potential energy for kinetic energy. Assuming you want to avoid perpetual motion machines and devices that can draw power from nowhere, you have to use the power formula I posted.

 

[Straybow]

The 500T ship [falling unpowered in a 1G gravity well] is being subjected to a force of roughly 5 million newtons, and is busy exchanging potential energy for kinetic energy.

Neither the ship nor the occupants will detect the acceleration by inertial senses/sensors: it is in freefall. With gravity, the only force applied is one which resists the acceleration, such as drag forces once the ship enters the atmosphere, or ground pressure when resting on the surface.

That's the whole point of Relativity. You can't distinguish between force caused by gravitational acceleration meeting passive resistance and a thruster applying force.

No, I'm not [applying conservation of momentum], I'm simply assuming that the drive is pushing on something. By definition, Power = Force * Velocity.

…Assuming you want to avoid perpetual motion machines and devices that can draw power from nowhere, you have to use the power formula I posted.

What? I have a definition power P = iv, so that means the 500T ship must have a net charge, and there must be an electric potential which accelerates the ship.

See? Throwing out an equation is subject to conditions, and conservation of momentum is the condition of P = F·V just as Ohm's law etc is the condition of P = iv. We aren't using the EM force, therefore P = iv doesn't apply. "Pushing on something" is, exactly, conservation of momentum.

If you climb into a little red wagon and push off with your foot on the pavement to impart velocity, you are exchanging momentum with the Earth. The incremental change in the Earth's momentum is too small to measure directly, but that's where it is coming from. Therefore I can't tell how fast you are now moving by conservation of momentum.

I need some other way to determine the energy imparted. I can measure the final velocity after the push, and then back-calculate the change in momentum and change in kinetic energy. The momentum is assumed conserved. The energy comes from chemical power in your muscles, and is conserved if you include heat waste.

I used a one second average delta-vee to calculate change in KE instead of trying to figure out an instantaneous change of velocity equation (velocity relative to what for grav field manipulation??) for a proper calculus integral for delta-KE. We don't know how momentum exchange is mediated by artificial gravitation, therefore we have no way to evaluate conservation of momentum directly.

By my example grav drive was only 30% efficient at producing acceleration from input power (assumed electrical), which is hardly a "perpetual motion machine"

 

[Anthony]

Originally posted by Straybow:
Neither the ship nor the occupants will detect the acceleration by inertial senses/sensors: it is in freefall.

True if not relevant.

No, I'm not [applying conservation of momentum], I'm simply assuming that the drive is pushing on something. By definition, Power = Force * Velocity.

What? I have a definition power P = iv, so that means the 500T ship must have a net charge, and there must be an electric potential which accelerates the ship.
[/QB]

Well, since one volt is the electric field that will apply one newton of force to a one coloumb charge, these two definitions are in fact the same.

One watt = 1 joule/sec
1 joule = 1 kilogram m^2/s^2 = 1 newton x 1 meter.

See? Throwing out an equation is subject to conditions, and conservation of momentum is the condition of P = F·V just as Ohm's law etc is the condition of P = iv.

Actually, P = F*V is not dependent on conservation of momentum, it works just fine if you're pushing on an immovable object.

I used a one second average delta-vee to calculate change in KE instead of trying to figure out an instantaneous change of velocity equation

Here, I'll do it. This is first year calculus.

V = at +v0, where v0 is initial velocity.
F = ma
ke = 1/2 mv^2
= 1/2m(at+v0)^2
= 1/2m(a^2t^2 + 2 atv0 + v0^2)
power = d(ke)/dt
= 1/2m(2 a^2t + 2av0 + 0)
= 1/2ma(2at + 2v0)
= ma (at + v0)
= F * V

for a proper calculus integral for delta-KE.

.
Derivative, not integral.

By my example grav drive was only 30% efficient at producing acceleration from input power (assumed electrical), which is hardly a "perpetual motion machine"

Ok, you have a device that produces 5 million newtons of force, with a power input of 250 megawatts.

Put it on a rotating arm, which we will assume the tip rotates at 100 meters per second. To keep it from going faster, we will attach an electric motor to the axle.

Now, we have 5 million newtons force * 100 meters per second, and therefore the electric motor, assuming 100% efficiency (which it will come close to) will output 500 megawatts. Of which 250 megawatts are required to power the gravity drive, and the remaining 250 megawatts may be used as desired.

 

[Jamus]

The problem here is you really cant call it a gravity drive since gravity only exists as a product of mass, The drive would work by pushing aginst or pulling to a mass using some sort of advanced magnetism the down side is the farther from a mass and its gravity well the less return for power you would get from this sort of drive. mis-jump into the void with no mass to push or pull from and you are done.

Gravity is a product of mass and the effect of mass on space, even though the mass drive should theoritically work as would anti grav and contra grav there is no way i can see artificial gravity.

In order to create 1G arti-grav one would have to simulate or create a mass equil to the earth. I dont see that as a possibility. in effect Gravity as a energy form that can be manipulated doesnt exist.

at least imo, i could be wrong

 

[Straybow]

Actually, P = F*V is not dependent on conservation of momentum, it works just fine if you're pushing on an immovable object.

No, it doesn't. F=anything, V=0, no power. But if you are pushing on the immovable object with, say, a rocket, that rocket is putting out power. The V used is Ve, exhaust velocity, and it exerts a force which causes compression of the molecular structure around the contact area. Just like my example of pushing with your foot against the pavement to accelerate the little red wagon.

It is conservation of momentum. The "immovable_object"+rocket+fuel system has a net velocity of zero, so it's momentum doesn't change.

Put it on a rotating arm, which we will assume the tip rotates at 100 meters per second. To keep it from going faster, we will attach an electric motor to the axle.

Now, we have 5 million newtons force * 100 meters per second, and therefore the electric motor, assuming 100% efficiency (which it will come close to) will output 500 megawatts. Of which 250 megawatts are required to power the gravity drive, and the remaining 250 megawatts may be used as desired.

You are assuming grav tech works just like a physical force, but it does not. Being attached to an arm and braked by an electric motor essentially means you are trying to accelerate the object you've used for anchoring the motor (which must be large enough to not be incorporated and moved by the grav drive). The result may be no acceleration of the arm at all; just like pushing on the immovable object. All the input power just goes into heat.

Alternately, the mass effected by the grav drive (the field effect laps over into the anchor body) is now such that it is no longer capable of 1G acceleration; the behavior of the artificial warping of space-time is defined however we need to make it work without entropic contradictions. The effective force exerted by the constrained grav drive drops so that less than 250MW of F*V acts upon the motor.

Originally posted by Jamus:
Gravity is a product of mass and the effect of mass on space, even though the mass drive should theoritically work as would anti grav and contra grav there is no way i can see artificial gravity.

Well, mass is the only thing we know of at this time that effects the curvature of space. For example, we have no idea what electric charge is, and how it selectively works only on bodies (macroscopic, microscopic, subatomic, or quark) with net electric charge. If EM is also some kind of fabric-of-space effect, then we have a whole lot to learn before we can say what is and is not possible.

 

[Drakon]

Originally posted by Jamus:
The problem here is you really cant call it a gravity drive since gravity only exists as a product of mass,

Not according to General Relativity. Energy is also a cause of gravity. This is one of the reason why black holes are believed to be more than theoretical constructs.

As a star uses up its fuel, as it proceeds up through hydrogen and then oxygen and carbon, finally making stuff up to iron on the periodic table, it generates heat, which pushes against the weight of the material. When it runs out of fuel, the heat gets turned off.

The size of a star is a balance between the heat, trying to expand the star, and gravity which tries to pull the star into as small a mass as it can. What has been found out is that the gravitational field is stronger with increasing pressure. Pressure is a source of gravitation as well.

So not only do you have mass contributing to gravity, but that mass is creating pressure, which also produces gravity. So you get in a run-away kind of condition, where increasing pressure causes increasing pressure. This will stop only at the point where Pauli exclusion principle plays a role, and keeps the object from collapsing further.

 

[Drakon]

Originally posted by Straybow:
Well, mass is the only thing we know of at this time that effects the curvature of space. For example, we have no idea what electric charge is, and how it selectively works only on bodies (macroscopic, microscopic, subatomic, or quark) with net electric charge. If EM is also some kind of fabric-of-space effect, then we have a whole lot to learn before we can say what is and is not possible.

First off, there are two ways to correct this, both end up at the same place. The first way is to note that energy also affects manifold curvature.The second way is to note that mass and energy are equivalent, therefore, there should be some effect on the manifold geometry from energy alone, just as there is with mass.

Second, your comment about the EM field brings to mind the work of Kaluza and Klein. Shortly after GR came out, they proposed a theory in which the manifold was 5 dimensions. If you take this assumption, then in a very natural way, the formulas for gravitation and Maxwell's equation fall out.

Later this was expanded to include the Yang Mills equations governing the strong and weak nuclear forces. The big holdup is what are all these extra dimensions besides the 4 that we normally deal with? Why can't we see them?

Several different proposed work around have been advocated. The dimensions are curled up in some respect, (and there is some evidence to support this view) We are seeing a 4 D projection of this 10 D space. (Some theories go up to 11 or 26 dimensions.) To date, there is insufficient evidence to determine which proposed solutions are true and which are not.

And these ideas have evolved onward to string theory, which I admit is so unfamilar that I am not able to say much about it.

I think what needs to be done is to figure out the properties of the manifold. Unfortunately, the manifold is such that it can not be observed itself, but you must add some other object and track it, to track the manifold. Like a ship in a vaste ocean, one piece of water looks just like the next. You have to study it by putting something else in it.

 

[TKalbfus]

All we want is a way to push a spaceship around. I'm fairly much a minimalist and think that only Jump Drives are required. Magical space drives aren't necessary. Do you really need spaceships accelerating back and forth for 4 weeks in the vicintity of a planet for as long as its fusion drives have power? There is no reason to go into orbit then is there. A ship can simply hover an its maneuver drives for as long as it has fusion fuel. Space Stations can hover and they can just dip into the atmosphere and collect some more water vapor to refill their tanks with hydrogen.

 

[Drakon]

I am thinking that a warp drive will provide both hyperfast as well as more ordinary speed. I am not sure that jump drive will do it, will provide the low speed travel that is required.

Here is a problem I have. Jump drive is more "magical" than warp drive at this stage of development. So far there is no direct evidence of other dimensions, or other "spaces", let alone whether they are usable for FTL travel. There is some serious theoretical work (and for all I know, possibly several research attempts) on warp drive, based on what we observe today.

 

[TKalbfus]

Aside from theoretical physics reasons, one of the game problems is that once you have warp drive, you don't really need a maneuver drive. You can take off from a planet's surface on a warp drive unless you say something such as gravity cancelling out warp effects. I guess you can have a 100 diameter rule for warp drive as for jump drive. Once your in Jump space you have no problems, there is nothing around you except for the ship. When you engage warp drive, you still have to pilot the ship to make sure it doesn't crash into anything. Also how do you see ahead of you? If you are going faster than the speed of light, you don't know what's in front of you. The ship will have to remember what was in the space that the warp ship wants to travel. All the light and radiation will come from in front of the ship as light cannot overtake it. Even light from objects behind the ship will appear to come from in front. A receding warp ship will always be visible, even if the image from light reflected off of it is grossly out of date. A warp ship can be light years away, but it will still seem to be leaving the last solar system it left. The Warp ship can even return and see its image leave the solar system. Approaching warp ships cannot be detected until after they arrive or have passed.

 

[Straybow]

I would posit that the energy densities necessary for an Alcubierre type warp would prohibit use on the planet's surface or in low orbit&#133

 

[TKalbfus]

It seems to require splitting the vacuum and separating vitual particle pairs concentrating the positive mass ahead of the ship and the negative mass behind, the spaceship sits between these two where the intense tidal forces cancel out. The positive mass makes a black hole with an equal amount of negative mass behind. The negative mass pushes all matter and bends light rays away from itself; the positive mass attracts all matter and bends light rays toward itself. The negative mass also pushes away the ship and the black hole, while the black hole attracts the negative mass concentration and the ship inbetween. What keeps the ship from being pushed away from the negative mass and into the black hole is the fact that both objects are accelerating in the direction of the blackhole. The blackhole while acceleration is eating up space in fron of it, while the negative mass concentration is replacing the space eaten up by the black hole. I don't know how to concentrate negative mass as tightly as a black hole as the negative mass will gravitationally repell itself, its potential event horizon is turned inside out, it can never form because as that critical density is approached its pushes all matter and energy away from itself, it can never be squeezed tightly enough so that it repells light and that light cannot enter. White holes cannot form that way and so are impossible objects. Also time is accelerated in the vicintity of a negative mass concentration, perhaps it is tghis property that prevents time dialation from slowing down events onboard the starship. So long as the starship remains in the "sweetspot" it is safe. There are some technical difficulties with breaking out of warp once it gets going faster than the speed of light, but this is science fiction, so you can assume that they figure out something.

 

[Drakon]

Originally posted by Tom Kalbfus:
Aside from theoretical physics reasons, one of the game problems is that once you have warp drive, you don't really need a maneuver drive.

You maybe right here. I don't see how this is a problem. Also, if you demand a manuvering drive for some reason, I can see designing a smaller "defocus drive", which instead of building a full warp bubble, just defocus (for lack of a better term) the local gravity field.

A gravity field caused by a planet or star focuses the manfold toward a singular point. And so geodesics get deflected from a straight line path, etc. You know what I am trying to say here. Anyway, if you could defocus a portion of this manifold, your geodesics could be deflected in a reversed or upward direction, carrying your ship with you.

So 1) I don't see a problem with ditching manuvering drives, and 2) Even if their is a problem the same technology should be able to deal with it, by using defocus drives for manuvering.

Once your in Jump space you have no problems, there is nothing around you except for the ship. When you engage warp drive, you still have to pilot the ship to make sure it doesn't crash into anything.

Autopilot for one work around. Also, I see this as a feature not a bug. The idea of travelling on an unpiloted starship is a bit much for this old sophont.

Also how do you see ahead of you?

1) http://xxx.lanl.gov/PS_cache/gr-qc/pdf/9907/9907019.pdf " Null geodesics in the Alcubierre warp drive spacetime: the view from the bridge"
2) If this does not work, you stutterwarp it.

Also, in answer to one of Strawbows arguments, this is dealt with in http://xxx.lanl.gov/PS_cache/gr-qc/pdf/9905/9905084.pdf "A `warp drive' with more reasonable total energy requirements" and
http://xxx.lanl.gov/PS_cache/gr-qc/pdf/0107/0107097.pdf "Reduced Total Energy Requirements for a Modified Alcubierre Warp Drive Spacetime"

There are 13 papers listed on the LANL archives when one searches for the terms "Warp Drive" A lot of the theoretical issues have been dealt with, and right now it appears to be a matter of technology. Of implimentation.

Hmm.. did I miss anything? A lot of my argument has taken the form of "I think you are mistaken and even if you are right, I think there is a simple solution to such problems." What can I say, I watch too much lawyer TV.

 

[Drakon]

Originally posted by Tom Kalbfus:
It seems to require splitting the vacuum and separating vitual particle pairs concentrating the positive mass ahead of the ship and the negative mass behind, the spaceship sits between these two where the intense tidal forces cancel out.

First off, forget particle pairs, virtual or real. This has nothing to do with the creation of particles in any way, shape or form. It has to do with directly manipulating the manifold, which is going to be required for any kind of gravity technology anyway.

It bends the space, but in front and in back of the ship. Granted massive positive mass particles will bend space (for lack of a better term and alludign to the rubber sheet pedogogle device) "down". Negative mass OR ENERGY, will bend it back the other way, in an "up" direction.

But the bending actually occurs more in the transistion regions around the middle of the ship. Also, as I understand it, this is where the major constituent of your exotic or negative mass/energy needs to be. In this transition band between the contracting forward part of the bubble, and the expanding aft part.

Also, another problem with the particle pair thingy is that antimatter has positive mass, just like regular matter. So even particle pairs won't do the job for you.

Let me look through my notes at home. I have a paper from a Russian scientist on "Grazers" the gravitational equivalent of a laser, in that something that will produce gravitational waves, in a single coherent beam. It has 3 proposed methods of doing so, however 2 of them are technically unfeasable due to the weakness of gravity compared to electromagnetism. You end up burning up the unit before you can produce a measurable beam. The third method, I am not familiar enough with to judge.

Note: gravity waves ARE bending the actual manifold. This might produce particle pairs under extreme curvature, but that would be as a result, or an effect of the warp drive, not a cause or or part of its operating mechanism.

One of the things I had thought of was using some kind of interference method to achieve or construct the warp bubble. I don't know if it would work or not, yet. I need a good math or EM guy to help me work it all out.

 

[Drakon]

I don't think this is the paper I was referencing earlier, but here is another paper that may be of interest

http://xxx.lanl.gov/PS_cache/physics/pdf/9802/9802037.pdf "Grasers based on particle accelerators and on lasers"