Mach Effect progress

[birchoff]

I don't know if what Dio was suggesting was that the only requirement to generate a Mach Effect is to charge a capacitor, but the two requirements are this large change in internal energy (shape change materials like perovskite crystals being charged as capacitors) and that the material needs to be accelerated relative to the distant stars. Dio is certainly correct that smaller is better and this is in Jim's book. Not only do you reduce spurious resonances that kill your mechanical Q by reducing the thruster cross section, but you mitigate heating issues and solve a handful of other practical concerns. We don't know if the gravinertial flux propagating from these things at c can be constructively and destructively interfered with yet, so we know what we don't know about arrays. It may turn out there are very specific concerns for large arrays that limit how they're designed, as well as create new possibilities depending upon how they're designed. In fact, the bootstrapping method of running two wormhole generators out of phase that are linked at a distance that causes them to constructively interfere, that is explained in Jim's book; is one possible way of using arrays, but as I have said to those holding this position, I don't then see a salient distinction between small elements in an array, and the very molecules of any particular element. This quickly turns into a nightmare of calculation. We'll have to wait and see what we see.

Oh and BTW Dio, all 1/4 wave acoustic resonators have an inverse proportional relationship between their thickness and their frequency, so at 1 Mhz, you have to have very small elements, at least in their thickness. At 500 Mhz, these thicknesses are measured in microns and microwave resonators are near the limits of how thin we can make things.

The problem facing the Mach Effect experimenters today is the magnitude of the thrust is not big enough to offset the weight of just the thruster (much less the thruster and its power source).

Surprisingly, not. What you're describing is what I like to distinguish as between "low thrust efficiency" and "high thrust efficiency" applications. Low thrust efficiencies where the thruster is much more massive than the force it generates, are still quite useful. Hall thrusters on geosynchronous orbit telecommunications satellites weigh much more on Earth than the thrust they put out, but in microgravity they can still achieve the results needed. So really when you look at thrust to mass, you are looking at general classes of applications. (Same with thrust to power so I lump these two together into the high and low classes.) If you want a flying car, or a spaceship that can fly direct from the surface of the planet, then yes, the thruster has to produce several times more thrust than the weight of the thruster and power supply. If all you want to do is create a space tug to tote Dragon 2 to the Moon or Mars, then you can make due with far less thrust. In fact someone did some decent calcs here in the forum a few weeks ago and found that it doesn't take much thrust at all to reposition all of ISS from its highly inclined orbit to equatorial, given 6 months to do this. Even I was surprised how easy things can be when you can't run out of propellant. And really the calcs that describe what we would be able to do with a nanosat with just a few mN's continuous thrust are astonishing. If you can loiter in the VAB without being cut to shreds, you can send 15,000 nanosats to LEO with a single Falcon 9 and fly them to the asteroid belt. THAT is the kind of thing that can make space exploration cheap, even without high thrust efficiencies.

But of course we want the high thrust efficiencies, flying cars and Millenium Falcon's too. Just they need to wait a bit.

If we can produce 20 mN thrust continuously, that can be reversed on command, with very little power and from a thruster and power supply that can last hours on a smallish battery, we will have hundreds of millions in development funds available. It is EASY to sell such things, when people cannot doubt what they're looking at, and have explained to them what is suddenly possible. For instance, DARPA has been looking for years for some method of repositioning sats on command and constantly maneuvering on orbit with sat killer craft, etc. This is probably what X-37 is all about but it still runs out of propellant and needs to come home. Even very low efficiency METS can make X-37 obsolete, because they cannot run out of propellant.

Yeah I lost sight of the microgravity applications. Which leads me to ask. Which approach has the easiest path forward? Increased durability to allow use in micro gravity applications or Increased thrust?

[Diogenes]

If you accept that you can get a transient mass fluctuation from charging and discharging a capacitor, the rest of it automatically follows as a self evident method of exploiting this effect. Now while I don't follow how you can assert that charging and discharging a capacitor will result in a mass fluctuation (other than from the tiny electron mass being shuttled back and forth) it is not necessary that I understand such a thing in order to consider methods for making it useful.


...


Instead of making 1 big unit with all of the compressive mushiness and inter-electrode capacitance and binding issues, it would seem that it might be feasible to make arrays of small ones.


Each one may produce a miniscule effect, but acting in concert and cumulatively, they could collectively produce an effect significant enough to give a good signal.


Etch them on substrates. It's not like we haven't been doing stuff like this for a long time.

...

GiThruster please correct me if I am wrong here. But it is my understanding that simply charging and discharging a capacitor is not enough to create a Mach Effect. It is simply one step in the many that need to be executed at the exact right time to result in the "Impulse" Mach Effect.

Yes, I forgot to mention "While under acceleration" and I after I had posted it I thought about going back to re-edit that, but then I said "ah, they'll know what I meant." Obviously I was mistaken.

Hope this doesn't derail the essential point, but it looks like it did.

Additionally while I think your idea in general is what would be applied in the end. The problem facing the Mach Effect experimenters today is the magnitude of the thrust is not big enough to offset the weight of just the thruster (much less the thruster and its power source). In the end I think the question becomes what is the sweet spot of thruster Size/Mass where you get enough thrust to lift the thruster plus some additional amount. When they start getting the excess thrust is when they can being lashing these things into arrays(assuming the mass needed the array does not consume the excess).

Well see, here's the deal. It's a lot easier to accelerate many teeny tiny capacitors at the frequencies being discussed than it is to move one big one. Acoustical response works in our favor if we go smaller but not if you go bigger. It's easier to drive a smaller mass at higher frequencies than it is to drive a larger mass.


Judging by the pictures i've seen of the devices, I would say that driving them at 1 mhz+ would be difficult because of the sponginess of such a large mass. My experience with piezo crystals is that a 1 mhz piezo device has a natural resonance in a much smaller footprint than what it appears they are using. You rigidly bond a mass to it and you lower it's resonance frequency even more.

If you go smaller, you can get piezos that resonant at much higher frequencies. I believe i've seen 50 mhz piezo devices, but they are pretty small and thin.


I used to know people that manufactured crystals for radio oscillators, I'll see if I can get back in contact with them and see what they have to say on this.

[Diogenes]

I don't know if what Dio was suggesting was that the only requirement to generate a Mach Effect is to charge a capacitor, but the two requirements are this large change in internal energy (shape change materials like perovskite crystals being charged as capacitors) and that the material needs to be accelerated relative to the distant stars.

Yup. I erroneously forgot to mention the acceleration requirement. Dumb oversight.

Dio is certainly correct that smaller is better and this is in Jim's book. Not only do you reduce spurious resonances that kill your mechanical Q by reducing the thruster cross section, but you mitigate heating issues and solve a handful of other practical concerns.

Exactly. You put the mass of a capacitor on the side of a piezo crystal and it instantly messes with the natural resonance of it, and that's if you don't have any issues with a good bond between the piezo device and the capacitor.


I do not currently know how the capacitor is being attached to the piezo device, and perhaps you can clue me in on this, but it would seem to me that it would need a very strong bond to enable it to work properly. From what I can see of the devices that have been built, this does not appear to be the case. It *LOOKS* like they are simply pressed together and bolted in place, and if this is the case, I cannot see how this will work properly because the two devices will separate at the joint and the piezo device will end up pounding it like a soil compactor on concrete, but will not actually move it very efficiently.





It needs to pull it as well as push it. A tensile bond is also important, and this is one of those things which would seem easier with a smaller mass than a larger one.


I am going to see if I can find some people I used to know who were experts at making piezo crystal resonators and ask them for some ideas.

[Diogenes]

...

Another problem is, that if you have a 1N/W thruster, you don't need the fuel cells because they're efficient enough you can just strap them to a flywheel and generate your own power from the gravinertial field. We didn't look at that because we're both firm believers in "one impossible thing at a time" but you need to understand that according to theory, METs are not electrical to kinetic transducers that are limited in their output to the electrical energy in. They're gravinertial transistors that control the flow of momentum into the device, and the real power being handled is in the universe's gravity field. So you can actually harvest energy from the field (not too different from an electrical alternator" or a sail) and when you do this, you don't need fuel cells.
...

So I am intrigued that you have touched on this possibility. As you are pretty much the first person that I would consider close to this effort that has mentioned it. Is it accepted by Woodward and his collaborators that this is a natural outcome?

I cringe when stuff like this gets mentioned. This is exactly the sort of thing which can be expected to drive people away from the idea. Anything that smacks of "free energy" is instantly categorized as "scam" propagated by "nutburgers" in the minds of a lot of otherwise potentially interested people.

I would put a hiatus on extrapolations of "worm holes" and "free energy" because those are simply a bridge too far for many serious minded people. As GIThruster says, "one impossible thing at a time." If the basic idea works out, we'll all have plenty to celebrate about.

[birchoff]

...

Another problem is, that if you have a 1N/W thruster, you don't need the fuel cells because they're efficient enough you can just strap them to a flywheel and generate your own power from the gravinertial field. We didn't look at that because we're both firm believers in "one impossible thing at a time" but you need to understand that according to theory, METs are not electrical to kinetic transducers that are limited in their output to the electrical energy in. They're gravinertial transistors that control the flow of momentum into the device, and the real power being handled is in the universe's gravity field. So you can actually harvest energy from the field (not too different from an electrical alternator" or a sail) and when you do this, you don't need fuel cells.
...

So I am intrigued that you have touched on this possibility. As you are pretty much the first person that I would consider close to this effort that has mentioned it. Is it accepted by Woodward and his collaborators that this is a natural outcome?

I cringe when stuff like this gets mentioned. This is exactly the sort of thing which can be expected to drive people away from the idea. Anything that smacks of "free energy" is instantly categorized as "scam" propagated by "nutburgers" in the minds of a lot of otherwise potentially interested people.

I would put a hiatus on extrapolations of "worm holes" and "free energy" because those are simply a bridge too far for many serious minded people. As GIThruster says, "one impossible thing at a time." If the basic idea works out, we'll all have plenty to celebrate about.

Dont get me wrong I completely agree that trumpeting what could be possible before we have even taken the first step to making the impulse term useful is a waste of time. I just couldnt help myself since GiThruster mentioned the flywheel in his response. That said, while I understand how hard it is for the human mind to accept something they have ZERO experience with, I wonder if free energy is even the correct term to be used to describe such a device. It is only free energy as much as the sun is free energy. The problem as I see it is free energy means more than that when people use it and come across it.

[birchoff]

Dio & GiThruster:

Taking what you both said as true. What would the design look like then? For example what would a miniturized version of either the single bolt or size bold configuration of the thruster in the deck below look like.

http://aspw.jpl.nasa.gov/files/ASPW2014 ... /Fearn.pdf

[kunkmiester]

Time averaged, is smaller really that much better? A larger thruster would run at a lower frequency, but that doesn't mean it's a bad idea. Fewer thrusters would make control easier(as well as the lower frequencies needed), and larger mass would make up for thermal management to some extent. Larger is also easier to manufacture in some ways. For experiments, I can see it making a lot of sense, but once things get going, I'd imagine there would be some research done, and the sweat spot will probably be larger than you think.

[GIThruster]

Which approach has the easiest path forward? Increased durability to allow use in micro gravity applications or Increased thrust?

IMHO, it can't be either or. For a commercial application we need a durability measured in years, which is completely reasonable given the history of the performance of these kinds of materials, and we need to have mN thrusts to have a working technology. We need to do both and the best answers answer more than one of these requirements I've listed above, including thrust to power, thrust to mass, durability, reversibility, etc.

So I am intrigued that you have touched on this possibility. As you are pretty much the first person that I would consider close to this effort that has mentioned it. Is it accepted by Woodward and his collaborators that this is a natural outcome?

Yes. We don't often speak of it because of exactly the concern Dio has offered. Thing is, with Jim's book out, anyone who thinks clearly through the technology knows about these energy harvesting applications. After all, this is what Tom Mayhood was talking about back in the 90's when he hung the sign the lab door that read "Tomorrow's Momentum Today". It's in the book.

It's a lot easier to accelerate many teeny tiny capacitors at the frequencies being discussed than it is to move one big one. Acoustical response works in our favor if we go smaller but not if you go bigger. It's easier to drive a smaller mass at higher frequencies than it is to drive a larger mass.

This is only part of the issue. Size doesn't matter. What matters is the thickness of the resonating material--the cross section is unimportant so far as resonance is concerned, save the stray harmonics that occur with certain sizes and geometries. Any given thickness will provide a natural resonance of precisely one frequency, and driving above that frequency cannot ever give the mass enough time to reach full extension and thereby generate max acceleration. Frequencies below the natural resonance are possible, but these do not have the enhanced mechanical Q of operation on resonance. Despite this, since the device has to oscillate at two frequencies, one of them will not be optimized. There's no way around this, even with more than one element in a stack. That's just the way acoustics works.

My experience with piezo crystals is that a 1 mhz piezo device has a natural resonance in a much smaller footprint than what it appears they are using. You rigidly bond a mass to it and you lower it's resonance frequency even more.

Yes, this is a measure of what is called the resonator's "damping". By both definition and design, you want an underdamped device with a mechanical Q of at least 1/2. Langevin transducers like Jim's design, have mechanical Q's up to 700 on resonance. The Q is much lower off resonance. Note too, Jim's device operates around 30 Khz. He's never built a Mhz design since he only has access to LF power equipment.

I do not currently know how the capacitor is being attached to the piezo device, and perhaps you can clue me in on this, but it would seem to me that it would need a very strong bond to enable it to work properly.

In the current iteration, the capacitor is the piezo device, so you don't need to worry about bonding. The bonding Jim does is merely to segment the stack in order to accommodate lower voltages to run the stack by interleaving the electrodes, and to insert accelerometers, but he is running an essentially single element stack and the stack is confined by clamping so it can't go through explosive decomposition. However, were you to use a multi-component design with separate force generation and M-E generation elements, you can't glue stuff like that together and use it at HF, VHF and UHF frequencies. You need to use molecular diffusion bonding, sputtering, some form of molecular deposition such as chemical vapor deposition or even molecular beam epitaxy (very expensive and slow). These are all the processes I've studied the last 9+ years and I hope you can understand why I can't discuss much more on this subject. I already know what we need to do. I just need to gather a team to do it.

I wonder if free energy is even the correct term to be used to describe such a device.

It is the correct term only in as much as a windmill is a "free energy device". And yeah, especially because of all the ZPF nonsense, it is best to avoid the use of the term altogether. It's enough to say MET's harvest momentum from the universe's future. That's much more accurate and descriptive, and yet is in many ways too much to get one's arms around. It's only because we observe the universe's accelerating expansion and that this is explained by M-E technology in our past and/or future, that I will even consent to discuss it at all. Best to leave the subject and talk about what the technology is capable of in the short term. But make no mistake--Jim has let the cat out of the bag. He wrote a book on how to build wormhole generators for cryin' out loud! Those are time machines, folks! What sounds too incredible after that?! Read the book.

What would the design look like then?

Did you want to sign an NDA?

Time averaged, is smaller really that much better? A larger thruster would run at a lower frequency, but that doesn't mean it's a bad idea.

Thrust scales linearly with frequency. Faster is better.

[birchoff]

So I am intrigued that you have touched on this possibility. As you are pretty much the first person that I would consider close to this effort that has mentioned it. Is it accepted by Woodward and his collaborators that this is a natural outcome?

Yes. We don't often speak of it because of exactly the concern Dio has offered. Thing is, with Jim's book out, anyone who thinks clearly through the technology knows about these energy harvesting applications. After all, this is what Tom Mayhood was talking about back in the 90's when he hung the sign the lab door that read "Tomorrow's Momentum Today". It's in the book.

I wonder if free energy is even the correct term to be used to describe such a device.

It is the correct term only in as much as a windmill is a "free energy device". And yeah, especially because of all the ZPF nonsense, it is best to avoid the use of the term altogether. It's enough to say MET's harvest momentum from the universe's future. That's much more accurate and descriptive, and yet is in many ways too much to get one's arms around. It's only because we observe the universe's accelerating expansion and that this is explained by M-E technology in our past and/or future, that I will even consent to discuss it at all. Best to leave the subject and talk about what the technology is capable of in the short term. But make no mistake--Jim has let the cat out of the bag. He wrote a book on how to build wormhole generators for cryin' out loud! Those are time machines, folks! What sounds too incredible after that?! Read the book.

I did read the book, cover to cover. Though now that I have run through most of the papers I should make some time to read it again. The "Tomorrow's Momentum Today" sign didn't really sink in till this discussion. Does anyone know what will happen when this technology begins being exploited to its fullest? With a windmill the side-effect is those down wind encounter less wind energy, same with hydro electric, same with solar. However, the source remains unaffected (for the most part) could the same be said in this instance?

[GIThruster]

There are two ways of understanding the consequence of tapping the gravinertial field for momentum and energy. One is to note you're stealing momentum and mathematically, this means you're causing the universe to accelerate in its expansion. The other is to note you're decreasing entropy locally, which means you must be increasing entropy globally. This also is a measure that the universe should accelerate in its expansion. (See Entropy, thermodynamics and the "arrow of time" on this.) So no matter how you look at the issue, the adverse effect of using the technology in all its iterations should be the universe should be rushing ever faster toward its end.

Of course if it turns out that cosmological topological change is possible, then wormholes can reach backward in time, and we can escape the heat-death end of the universe. And who knows how many quadrillions of people might do this billions of years into the future? Certainly if that were to happen, the signs in our times would be an otherwise inexplicable acceleration in the universe's expansion.

[AcesHigh]

I remember some speculation years ago, here at TP, that the ideal design for a ME Spaceship would be somewhat like... a flying saucer?

[AcesHigh]

There are two ways of understanding the consequence of tapping the gravinertial field for momentum and energy. One is to note you're stealing momentum and mathematically, this means you're causing the universe to accelerate in its expansion. The other is to note you're decreasing entropy locally, which means you must be increasing entropy globally. This also is a measure that the universe should accelerate in its expansion. (See Entropy, thermodynamics and the "arrow of time" on this.) So no matter how you look at the issue, the adverse effect of using the technology in all its iterations should be the universe should be rushing ever faster toward its end.

Of course if it turns out that cosmological topological change is possible, then wormholes can reach backward in time, and we can escape the heat-death end of the universe. And who knows how many quadrillions of people might do this billions of years into the future? Certainly if that were to happen, the signs in our times would be an otherwise inexplicable acceleration in the universe's expansion.

any time travel to the past is mind bending...

1 - does the wormhole opening accelerates the expansion of the universe time-locally (your end of the wormhole) or also in the other mouth of the wormhole (in the past)?

2 - are we dealing with multiverses (each time you go to the past you open a new branch universe) or with a single universe? In this case, the temporal paradoxes are really mind bending, including the fact each time civilizations travel to the past from the distant future, they are accumulating population in the past who can use technology that increases entropy. The process, if it´s the same universe (how we deal with the paradoxes I have no idea), could have happened already a trillion times. And each time more advanced populations of the far future travel back in time and populate the universe in the past, somehow adding to other migrations from the future to the past. And each time we have more and more beings tapping into the universe future and accelerating the expansion... ?

[GIThruster]

I remember some speculation years ago, here at TP, that the ideal design for a ME Spaceship would be somewhat like... a flying saucer?

I've considered this now for many hours over the years and I don't think there is one design that meets a "best" criteria. I think there are several.

For making space travel as ubiquitous as possible, one wants to build the equivalent of a Ford Model T or DC-3. IMHO, the best way to make space travel "safe, quick, convenient and economical" is to go immediately for economies of scale, by producing a basic assembly line that can actually build many different kinds of craft by fitting together modules of various different sorts. The skin of the craft seems at this time best made of composite, because composite's high moisture content aids in protecting from space weather (radiation), and because unlike metals, it does not convert gamma into far more dangerous forms of radiation. You don't want to use metal.

When it comes to composites, by far the most cost effective means, and the one that produces by far the highest strength to weight is either dry or wet-filament winding. Wet filament was the preferred method 10 years ago, but new resins have been created in the last decade that make dry winding a legitimate option. (Both have made advances that no longer require baking in a vacuum.) In both cases, you are winding a thread around a mandrel that gives the shape to what is wound, and you want that shape to be common for as many spacecraft modules as possible. Also note you can't wind concave surfaces this way. You need a convex surface. The simplest is the cylinder. This is the most basic module. If you want to give a head nod to some aerodynamic concerns, you might make a truncated cone instead of a cylinder for one end. The other end you would want your docking/air lock module. So the simplest form would be one pointy end module and one docking module gives a space taxi. Put a cylinder with rows of seats between and you have a bus. I've noted 16 different kinds of modules to this sort of assembly that can easily yield millions of different configurations, each owner ordering what they want from this group of choices. You have communications rings that can turn an antenna assembly to any point on the circumference of the craft so the deck always stays normal to the direction of travel, and sleeping quarters, galleys, science facilities, medical, etc. I'm sure the list will grow longer. Basically though, you are looking at a cigar shape for the vast majority of craft.

For larger assemblies like this, it makes sense to have a "T" connector module available so all your builds don't require linear progression, and force people to walk through every module to get from one end to another. This is really just for the bigger craft. A pair of T connectors in a pair of linear progressions makes it possible to join two linear fuselages in parallel. It also makes it possible to dock at other than one end. A very complex arrangement of these relatively cheap modules can have as many docking rings as one likes, so the lines between spaceship and space station begin to blur. Note though, that every module has as many systems in common as is useful. So propulsion can be distributed for example, throughout the entire ship; say under the flooring for easy access should you need to replace ceramic drive units. Power can be in the ceiling. Life support can be in the walls. Common power busses can link modules so that if a single section takes an asteroid impact, the airtight doors at each end of every module can seal it off, and redistribute power and the ship automatically uses its redundancies to continue to fly. BTW, the doors in Star Trek make good sense if you can make them airtight, since they don't take up floorspace where they have to swing open. With two doors in every module, this makes a huge difference.

This is all cheap to build, but modular construction has one down side--it replicates systems in an inefficient manner such that it is not nearly as high performance as something built as a single unit. There are reasons to build other shapes. For instance, suppose you want to build a Hilton on the Moon, Mars or Titan (or all three). The most efficient method is surely to build hotel rooms on Earth, fly them to their homes and snap them together like Legos. Each room is similar to the modular construction above except there is now utility in a square or rectangular cross section, and you don't need things like propulsion systems. You can filament wind these rooms too, and you can even wind them with a trapezoidal cross section for assembly into ring-cities in the sky. These aren't spacecraft though they would likely have their own life support, but the point is to move them economically, you need an external cargo carrier like the S-64 Skycrane or even resembling a tractor trailer. You design the rooms so your transport can pick them up from the parking lot at the factory, fly them straight to their destination and snap them into place. If you want to fly them with people aboard, at one Gee it's 9 days to Titan. If you want to fly them robotically, you can choose any plausible acceleration in vacuum to get shorter travel times for each hauler. If you can make it to Mars in a few hours, all the better to optimize your transport ship's scheduling. Keep it flying fast and cheap. No pilots required. Especially since you'd expect the return trips to all be empty, why limit the travel accelerations to those a person can endure comfortably? Pull 10 Gees on the homeward trip while the ship is unladen. That saves money.

When it comes to special needs that you can't serve with modular construction, perhaps the best need to represent that class is any ultra-high performance ship, such as what the military sails and flies. The military is one of the few groups who could have a pressing need to fly fast in atmo so they might prefer a triangle or saucer shaped ship. While these shapes can move through atmo fast on edge, its when they're in vacuum the shape really comes into its own. You want the largest cross sectional area to be normal to travel so there's room for lots of thrusters, so short and wide makes good sense. Also saucers are a good shape for fitting a wormhole generator should you take the technology that far. In Nembo Budrini's depiction on the cover of Woodward's book, The Journey Home; you see a ring generator fitted around the ship, but there is really no reason to have empty space inside the ring at all. If you fill that space with spacecraft, and make it thin on edge for atmo, and as wide a cross section as possible for fitting the most thrusters as possible, you get a saucer geometry and the best way to construct it, is as a single unit--not modularly.

Cigars, triangles and saucers--pretty much your best options save for the robotic trucks that one supposes might resemble the S-64 Skycrane, though even that presumes a need to extend the ship below the top of the external cargo and that might not be necessary at all. Depends how you grapple the cargo. Might look closer to the Eagle Transporter in Space 1999.

[birchoff]

I remember some speculation years ago, here at TP, that the ideal design for a ME Spaceship would be somewhat like... a flying saucer?

I've considered this now for many hours over the years and I don't think there is one design that meets a "best" criteria. I think there are several.

For making space travel as ubiquitous as possible, one wants to build the equivalent of a Ford Model T or DC-3. IMHO, the best way to make space travel "safe, quick, convenient and economical" is to go immediately for economies of scale, by producing a basic assembly line that can actually build many different kinds of craft by fitting together modules of various different sorts. The skin of the craft seems at this time best made of composite, because composite's high moisture content aids in protecting from space weather (radiation), and because unlike metals, it does not convert gamma into far more dangerous forms of radiation. You don't want to use metal.

When it comes to composites, by far the most cost effective means, and the one that produces by far the highest strength to weight is either dry or wet-filament winding. Wet filament was the preferred method 10 years ago, but new resins have been created in the last decade that make dry winding a legitimate option. (Both have made advances that no longer require baking in a vacuum.) In both cases, you are winding a thread around a mandrel that gives the shape to what is wound, and you want that shape to be common for as many spacecraft modules as possible. Also note you can't wind concave surfaces this way. You need a convex surface. The simplest is the cylinder. This is the most basic module. If you want to give a head nod to some aerodynamic concerns, you might make a truncated cone instead of a cylinder for one end. The other end you would want your docking/air lock module. So the simplest form would be one pointy end module and one docking module gives a space taxi. Put a cylinder with rows of seats between and you have a bus. I've noted 16 different kinds of modules to this sort of assembly that can easily yield millions of different configurations, each owner ordering what they want from this group of choices. You have communications rings that can turn an antenna assembly to any point on the circumference of the craft so the deck always stays normal to the direction of travel, and sleeping quarters, galleys, science facilities, medical, etc. I'm sure the list will grow longer. Basically though, you are looking at a cigar shape for the vast majority of craft.

For larger assemblies like this, it makes sense to have a "T" connector module available so all your builds don't require linear progression, and force people to walk through every module to get from one end to another. This is really just for the bigger craft. A pair of T connectors in a pair of linear progressions makes it possible to join two linear fuselages in parallel. It also makes it possible to dock at other than one end. A very complex arrangement of these relatively cheap modules can have as many docking rings as one likes, so the lines between spaceship and space station begin to blur. Note though, that every module has as many systems in common as is useful. So propulsion can be distributed for example, throughout the entire ship; say under the flooring for easy access should you need to replace ceramic drive units. Power can be in the ceiling. Life support can be in the walls. Common power busses can link modules so that if a single section takes an asteroid impact, the airtight doors at each end of every module can seal it off, and redistribute power and the ship automatically uses its redundancies to continue to fly. BTW, the doors in Star Trek make good sense if you can make them airtight, since they don't take up floorspace where they have to swing open. With two doors in every module, this makes a huge difference.

This is all cheap to build, but modular construction has one down side--it replicates systems in an inefficient manner such that it is not nearly as high performance as something built as a single unit. There are reasons to build other shapes. For instance, suppose you want to build a Hilton on the Moon, Mars or Titan (or all three). The most efficient method is surely to build hotel rooms on Earth, fly them to their homes and snap them together like Legos. Each room is similar to the modular construction above except there is now utility in a square or rectangular cross section, and you don't need things like propulsion systems. You can filament wind these rooms too, and you can even wind them with a trapezoidal cross section for assembly into ring-cities in the sky. These aren't spacecraft though they would likely have their own life support, but the point is to move them economically, you need an external cargo carrier like the S-64 Skycrane or even resembling a tractor trailer. You design the rooms so your transport can pick them up from the parking lot at the factory, fly them straight to their destination and snap them into place. If you want to fly them with people aboard, at one Gee it's 9 days to Titan. If you want to fly them robotically, you can choose any plausible acceleration in vacuum to get shorter travel times for each hauler. If you can make it to Mars in a few hours, all the better to optimize your transport ship's scheduling. Keep it flying fast and cheap. No pilots required. Especially since you'd expect the return trips to all be empty, why limit the travel accelerations to those a person can endure comfortably? Pull 10 Gees on the homeward trip while the ship is unladen. That saves money.

When it comes to special needs that you can't serve with modular construction, perhaps the best need to represent that class is any ultra-high performance ship, such as what the military sails and flies. The military is one of the few groups who could have a pressing need to fly fast in atmo so they might prefer a triangle or saucer shaped ship. While these shapes can move through atmo fast on edge, its when they're in vacuum the shape really comes into its own. You want the largest cross sectional area to be normal to travel so there's room for lots of thrusters, so short and wide makes good sense. Also saucers are a good shape for fitting a wormhole generator should you take the technology that far. In Nembo Budrini's depiction on the cover of Woodward's book, The Journey Home; you see a ring generator fitted around the ship, but there is really no reason to have empty space inside the ring at all. If you fill that space with spacecraft, and make it thin on edge for atmo, and as wide a cross section as possible for fitting the most thrusters as possible, you get a saucer geometry and the best way to construct it, is as a single unit--not modularly.

Cigars, triangles and saucers--pretty much your best options save for the robotic trucks that one supposes might resemble the S-64 Skycrane, though even that presumes a need to extend the ship below the top of the external cargo and that might not be necessary at all. Depends how you grapple the cargo. Might look closer to the Eagle Transporter in Space 1999.

I like the general ark but why would you do construction in a gravity well. I get that it will be necessary in the short term. But it seems to me it would be much easier overall to eventually migrate all manufacturing into space. especially when I have a free fusion reactor that I don't have to do maintenance on(not entirely true would need maintenance on the energy collectors, but you get my point).

In addition. another constraint on the materials used for hull would be micro-metoerite hits. The faster your going the stronger your hull needs to be.

[birchoff]

There are two ways of understanding the consequence of tapping the gravinertial field for momentum and energy. One is to note you're stealing momentum and mathematically, this means you're causing the universe to accelerate in its expansion. The other is to note you're decreasing entropy locally, which means you must be increasing entropy globally. This also is a measure that the universe should accelerate in its expansion. (See Entropy, thermodynamics and the "arrow of time" on this.) So no matter how you look at the issue, the adverse effect of using the technology in all its iterations should be the universe should be rushing ever faster toward its end.

Of course if it turns out that cosmological topological change is possible, then wormholes can reach backward in time, and we can escape the heat-death end of the universe. And who knows how many quadrillions of people might do this billions of years into the future? Certainly if that were to happen, the signs in our times would be an otherwise inexplicable acceleration in the universe's expansion.

any time travel to the past is mind bending...

1 - does the wormhole opening accelerates the expansion of the universe time-locally (your end of the wormhole) or also in the other mouth of the wormhole (in the past)?

2 - are we dealing with multiverses (each time you go to the past you open a new branch universe) or with a single universe? In this case, the temporal paradoxes are really mind bending, including the fact each time civilizations travel to the past from the distant future, they are accumulating population in the past who can use technology that increases entropy. The process, if it´s the same universe (how we deal with the paradoxes I have no idea), could have happened already a trillion times. And each time more advanced populations of the far future travel back in time and populate the universe in the past, somehow adding to other migrations from the future to the past. And each time we have more and more beings tapping into the universe future and accelerating the expansion... ?

True lots of potential repercussions. That said there is alot we can begin exploiting before those repercussions become something we need to start thinking about.