[silverslith]

Designed to explore and claim space for the enjoyment of the interstellar community of all lifeforms, the IPCS is a diamond skinned transatmospheric starship with a no onboard reaction mass electromagnetic drive. The main powerplant is a nuclear fission unit based on the proton fission of lead (very low radioactivity of fission products). An auxilary propulsion system uses the proton/ion cannon of the main fission reactor.
The liquid helium skin and superconductor coolant is used to transfer heat to a nanotech energy extractor/refrigeration system capable of extracting the kinetic energy of gas molecules and storing it in nuclear isomer batteries.
The craft has the ability to enter and leave the atmosphere of any planet or star with a magnetic field, and can accelerate at human limits within the heliosphere of any decent star. In interstellar space the acceleration achievable will be less but 1g is expected.

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[TheBigDog]

silverslith said:

Designed to explore and claim space for the enjoyment of the interstellar community of all lifeforms, the IPCS is a diamond skinned transatmospheric starship with a no onboard reaction mass electromagnetic drive. The main powerplant is a nuclear fission unit based on the proton fission of lead (very low radioactivity of fission products). An auxilary propulsion system uses the proton/ion cannon of the main fission reactor.
The liquid helium skin and superconductor coolant is used to transfer heat to a nanotech energy extractor/refrigeration system capable of extracting the kinetic energy of gas molecules and storing it in nuclear isomer batteries.
The craft has the ability to enter and leave the atmosphere of any planet or star with a magnetic field, and can accelerate at human limits within the heliosphere of any decent star. In interstellar space the acceleration achievable will be less but 1g is expected.

Cool idea, but do I see propellers?

Bill

[silverslith]

TheBigDog said:

Cool idea, but do I see propellers?

Bill

Could be the EM thrusters:D

Nah I just tacked them on for our worldwide publicity tour. After the proton-lead reactor and nanofridge's are sorted they can go.

Fixed:

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[silverslith]

An interesting property of the Superconducting EM drive is that the craft can (provided the planets mag field is strong enough) choose whatever combination of orbit altitude and velocity it likes without consuming energy.
Either it can orbit in excess of gravitational orbital velocity, generating a g force for the crew to enjoy by maintaining a stable current in its superconductors (no energy input) to generate the centripetal force.
Or it can orbit at any fraction of grav orbital v or zero velocity relative to the ground by magleving.
It could even turn potential energy into stored energy in its NukeIsomer batterys as it decended like a space elevator and reuse it to ascend again.

[CraigD]

Re: Prophesy Designs

silverslith said:

Have you guys considered an electromagnetic drive?
like superconducting loops with their return path shielded. No on-board reaction mass need apply. Any reason why that shouldn't work?

We considered this in some detail in ”can we fly in air”. Though this thread discusses the engineering of a “a car-sized, saucer-shaped aircraft massing 1000 kg and diameter of 5 meters”, it’s applicable to other shapes and intended uses, including spacecraft.

Despite a brief bit of excitement on my part when my omission of an important calculation understated electrical resistance by a factor of about 1 million, the discussion ended in the conclusion that such a vehicle is possible in principle, but not with any currently known materials. The basic problem is that ordinary conductors have such high resistance that they require huge amounts of power (and powerful cooling systems). All know superconductors cease to superconduct at much lower magnetic flux densities than are required. So the design must wait for a “supermaterial” that superconducts in an intense magnetic field, which current superconductor theory suggests is impossible.

Superconductivity has been a field filled with surprises and revisions of theory, so I’m inclined to take pronouncements of the “impossibility” of such a superconductor with a grain of salt (or would that be sugar?). However, I’m a loss to suggest a direction in which to pursue it.

Given this roadblock, I think we’re locked for the time being into spacecraft designs that are rockets (like the Prophesy) and ones where the power source is not part of the vehicle (such as starwisps and other naturally and artificially powered “light sails”).

[silverslith]

Thanks for linking that thread craigd, I've been thinking about this basically since a university lecture back in 89 when we got to fool around with some liquid nitrogen superconductors and button magnets (able to hang in the air over a coin sized piece of SC.
I did a flurry of research on it a few years ago and came to pretty much the same current requirement conclusions as you. I'm chuffed to see I wasn't losing some decimal places somewhere or other.
Precisely my conclusions about aerodynamic interactions.
The Solar systems mag field is quite wavey so course changes any direction seem plausible.
My conclusions were identical to yours regarding the problem of flux density killing superconductivity. I need to revise the limits of type one and two superconductors in this respect but engineering solutions are:
-minimise the density of the craft and distribute the wires as widely as possible.
-use liquid helium coolant as flux limits are much higher as temperature drops.

The nanofridge tech may not be as far off as you might think. Theres a lot going on in the field of on-chip cryogenics (I'll try dig out some links) and useful extraction of molecular kinetic energy seems entirely possible. This would be the breakthrough that would make engineering something like this practical.

here we go:
Superconductivity

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[silverslith]

So with your flying car example CraigD, say it was 10cubic metres and 10kg total weight (about the overall density of air). Then how much current would be needed to lift it and could the flux density be managed within limits of current superconductors?

Of course a flying car that only lifts its own weight of 10kg would be pretty useless, but as scale increases, lower density becomes easier and easier.

Appreciate your feedback.

[CraigD]

silverslith said:

So with your flying car example CraigD, say it was 10cubic metres and 10kg total weight (about the overall density of air). Then how much current would be needed to lift it and could the flux density be managed within limits of current superconductors?

The short answer to the last of this question appears to be “no”. Here’re some details:

From standard references, such as this wikipedia section, and the fundamental definition of force, we have:
,
where: is mass of vehicle, 10 kg in this example;
is acceleration of gravity, about 9.8 m/s/s at Earth’s surface;
is force, 98 N in this example;
is magnetic flux density, about 0.00003 and 0.00006 T at Earth’s surface;
is current;
is length of the conductor. The given 10 m^3 can be interpreted as many possible lengths, so I’ll just use a reasonable “big ship” size of 100 m.

So , which calculates to between roughly 16000 and 33000 A.

Rather than a working vehicle, let’s imagine a basic engineering experiment: Somewhere not close to Earth’s magnetic poles, we lay a length of superconductive wire (chilled to its operating temperature) on an insulating surface in an east-west direction, attaching each end to a powerful positive and negative terminal. We then pass a current thought it sufficient to lift it from the surface.

American Superconductors sells superconducting wire with a cross-section area of about .000002 m^2 and a maximum current capability of about 160 A. It’s made mostly of bismuth and silver, so should have a density of about 10000 kg/m^3.

Notice that ,
where is the wire’s density times its cross-section area, .025 kg/m for the American Superconductor wire.
So we can rewrite the current equation as: ,
and calculate a current required to levitate just the wire of about 3200 to 6500 A, about 20 to 40 times its capability.

Note that, with no changes in the wire’s direction, it shouldn’t induce a magnetic field that intersects itself, so loss of superconductivity due to magnetic field should not be an issue (as it would be in a self-contained vehicle). The issue here is the material’s ability to move electrons. Although superconductors have zero resistance, they have a finite current-carrying capacity.

It’s worth noting that, while it doesn’t appear practical to use the Earth or other bodies’ magnetic fields to lift objects from their surfaces, such technology is very promising for maneuvering objects already in orbit. Know as “tether propulsion”, some preliminary experiments have already flown, with others scheduled. These systems are “reversible” – electric energy, such as from a solar cell, can be used to increase the craft’s kinetic and potential energy, boosting it into a higher orbit, or they can be used to generate electricity while braking the craft into a lower (or different eccentricity) orbit.

A drawback to tether propulsion is that “popular destination” bodies like the Moon and Mars have effectively no magnetic field, so it can’t be used around these bodies. Jupiter and the other giant planets, on the other hand, have greater magnetospheres than Earth, and are, IMHO, prime locations to use electromagnetic tethers for both navigation and power generation. (I elaborate on this in a “big picture” manner in “Sheer human fecundity”, and ”Relevance of space elevators in a 1,000,000 times more energy rich civilization”) in the ”Colonizing the Solar System” thread)

The Sun’s magnetic field (the IMF), while about .0001 T (, about twice the Earth’s) at its surface, decreases with distance (though not as sharply as simple theory predicts). At 1 AU, the distance of the Earth’s orbit, it’s about , about 1/5000th that of Earth’s surface strength, so interplanetary maneuvering using electomagnetics appears impractical.

[silverslith]

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.000002 m^2 and a maximum current capability of about 160 A

Thats 2 square mm cross section. Or 80A per sqmm.
Seems like a pretty poor superconductor that can't carry more than a conventional one.

Looks like we can use our structure weight as the superconductor:
Get Wired for Superconductivity

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Get Wired for Superconductivity
P. Adams/LSU
Live wires. These 7-micron-thick wires carry current without resistance and have an unprecedented combination of strength and light weight.

A research team has created a new type of superconducting wire that not only carries a high electric current without resistance but also is remarkably strong, light, thin, and long. As the team reports in the August Physical Review B, the wires are made from an unusual magnesium-carbon-nickel compound layered around a carbon fiber. Experiments with the wires strongly suggest that the compound is an "exotic" superconductor whose properties can't be explained by the standard theory of superconductivity. Improved versions of the wires could be used in the electromagnets needed in a new class of spacecraft propulsion systems.

The explanation for superconductivity in standard materials such as niobium and lead has been in textbooks for decades, but unconventional superconductors--known as exotics--remain mysterious. Some researchers believe that the recently discovered superconductor MgCNi3 may bridge the gap between conventional superconductors and the most important class of exotic compounds, called cuprates, which can superconduct at temperatures higher than 100 degrees Kelvin. MgCNi3, which superconducts up to only about 8 degrees Kelvin, has a crystal structure similar to the cuprates, but it is simpler and does not contain copper or oxygen.

If MgCNi3 exhibits its own distinct exotic properties, it could help researchers understand electron behavior in cuprates and other materials. But the difficulty of synthesizing it has meant that not everyone can agree on whether it is unconventional, much less on the details of its behavior. "The experiments fall on both sides of the question," says Bob Cava of Princeton University, the material's inventor.

Phil Adams and David Young from Louisiana State University in Baton Rouge have now synthesized this superconductor in a new, thread-like form, which is better for testing its electrical properties than the flat films and powdery pellets that researchers have made before. The team put 3- to 5-millimeter-long nickel-coated carbon fibers in an evacuated tube with magnesium vapor and then heated the whole package in a 700-degree-Celsius oven for up to 30 minutes. The result was a core of carbon covered by an 80-nanometer-thick sheath of the new compound. The structure is "kind of like a cannoli," Adams says.

The team then measured the critical current--the current above which the fibers' superconductivity breaks down. When the researchers subjected the fibers to increasing temperatures and magnetic fields, the critical current dropped much more abruptly than predicted by the standard superconductivity theory, adding to the growing evidence that the material is exotic.


Adams and his colleagues were surprised by the size of the critical current: They extrapolated to an absolute zero value of 40 million amperes per square centimeter, 10 times higher than predicted from previous experiments with packed powders and almost as high as the theoretical maximum for non-high-temperature superconductors. Such a current would produce a magnetic field of up to 15 tesla in these wires--powerful enough to use in several futuristic spacecraft propulsion systems, which is why the Army has awarded Adams' team a grant to develop the technology.

A hot time for cold superconductors

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"With a smaller conductor, the cost of wire used in MRI magnets could be reduced from $3-10 per kiloampere of current per meter of wire to only $1-2," Peterson said. "Because many miles of wire are wound into the coils in a typical MRI, the development of less expensive wires by the private sector could put an MRI machine in every doctor's office and even in veterinary hospitals."

Today's MRI machines use niobium-alloy wires that are much more expensive than MgB2 wires and require costly liquid helium refrigeration to maintain superconducting properties. Los Alamos scientists fabricated a prototype MgB2 coil that generated magnetic fields in the range useful for MRI applications (above 1 tesla) operating at a temperature of 25 degrees above absolute zero. This temperature can be reached using commercially available refrigeration units at much lower operating costs.

https://www.furukawa...clead0412_e.htm

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Development of 20-kA Class Oxide Superconductor Current Leads, Demonstrating the Highest Current Rating in the World

ScienceDirect - Fusion Engineering and Design : High temperature superconductors for the ITER magnet system and beyond

Quote

For this purpose, we give a short summary of results that have been obtained from an ITER conform 70 kA HTS current lead that was designed, built and tested by the Forschungszentrum Karlsruhe and the CRPP Villigen in the frame of the European Fusion Technology Programme and in cooperation with industry. This current lead consists of an HTS part that covered the temperature range from 4.5 to 70 K and a conventional part, making the connection to room temperature. Because the HTS part had no ohmic losses and poor thermal conduction, the refrigerator power necessary for cooling the current lead was reduced drastically. The saving factor could be calculated to be 5.4 at zero current and 3.7 at 68 kA. The current lead could even be operated at 80 kA and with respect to safety criteria of ITER, a complete loss of He flow was simulated showing that the HTS current lead could hold a current of 68 kA for 6 min without active cooling. These results demonstrate that today existing HTS materials can be used in ITER for current leads or bus bar systems.

[silverslith]

Up to 5000 times your figure above seems a pretty good result.

[silverslith]

I'm interested in how the magnetic field is packed tightly inside the Heliopause. It seem to me that a solarpolar orbit in this layer could be one of the best trajectories for achieving Intersteller velocities.
Despite being 4 times the orbital radius of pluto still amazingly limited by the centipetal force:

Fcentr= m (v^2)/r
force/kg=(v^2)/r
F(0.1c)/kg=9e14/~2e13

=45 newtons/kg = 4.5g

Of course if we make our first port of call a blue giant then we could probably launch at >0.9c from its much larger heliosphere (provided the landing solar system has enough field to catch us. Neutron stars have enormous ones.) Not sure what relativistic effects would do. It'd be nice if our magforce increased along with mass but I doubt it.

It may be that getting most of your speed at slower accelerations in Interstellar space is still better.

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[CraigD]

silverslith said:

Quote

.000002 m^2 and a maximum current capability of about 160 A

Thats 2 square mm cross section. Or 80A per sqmm.
Seems like a pretty poor superconductor that can't carry more than a conventional one.

80 A/mm^2 (8*10^7 A/m^2) seems very high to me, compared to conventional conductors – about 13 times the Handbook of Electronic Tables and Formulas rating for copper wire.

Still, the links silverslith provides give impressive current carrying ratings – or predicted ratings, as I get the impression from them that, as of 8/2004, the “cannoli-like” .000007 m diameter MgCNi3 wires with a maximum current density of 4*10^11 A/m^2, had yet to be grown to more than a few mm in length.

Searching Furukawa Electric reveals recent success with a 500 m long test power cable with a cross-section of about .00009 m^2 (superconducting tape wrapped around a .028 m diameter hollow copper pipe, surrounded by a lot of cooling equipment) and a 1000 A current, about 10^7 A/m^2. I couldn’t find any data on the cross-section area of their 20 kA-class superconductors, so have not idea of its current density.

I get the impression, however, that a superconductor capable of the simple experiment I describe in post #8 may be available now or in the near future. Though just the first of several challenges involved in making a vehicle like the IPCS, this information make me optimistic, and curious for more details. Better yet, I wonder if some superconductor with better than 3*10^9 A/m^2 is available to the amateur, to actually conduct such an experiment.

[CraigD]

silverslith said:

Fcentr= m (v^2)/r
force/kg=(v^2)/r
F(0.1c)/kg=9e14/~2e13

=45 newtons/kg = 4.5g

I don’t follow what this calculation is getting at. For a constant acceleration of 4.5 gs (about 45 m/s/s) to produce a velocity of .1 c (3*10^7 m/s) requires about 7.7 days ((3*10^8 m/s)/(45 m/s/s) = 666667 seconds), and a distance of about 67 AU (.5 * 45 m/s/s * (666667 s)^2 = 10^13 meters) . There’s not much Interplanetary Magnetic Field for most of that distance – between about 10^-11 T at 1 AU to 3 *10^-17 T at 67 AU (compared to 3*10^-5 T at the Earth’s surface). So about a 10^12 increase in current over the previous “flying car” example is necessary – a pretty mind-boggling figure.

Another fact of which to be mindful is that electrodynamic propulsion, though much more efficient than rocket propulsion – with superconduction, essentially 100% efficient – still requires mechanical energy to accelerate a body. Even a tiny manned spacecraft – say 1000 kg – would require about 10^18 J, peaking at about 1.4*10^12 W – about the same as the world’s electrical power consumption.

Cramming the electrical generating capability of the whole planet Earth into a 1000 kg vehicle is clearly an engineering challenge – but not, I think, an insurmountable one. 1.4*10^12 W is equivalent to only about .000015 kg of matter and antimatter annihilating every second, while the entire energy requirement to accelerate it to .1 c requires the annihilation of only about 5 kg of matter and antimatter.

No matter its immediate engineering feasibility, the idea of “slingshotting” from strong magnetic field to strong magnetic field is an intriguing one, and not too implausible. It appears to require advances in three areas of technology – superconduction, electrodynamic propulsion, and very high, very high efficiency power generation – almost certainly based on antimatter. Such technology could be complimented by other very-high-power propulsion, such as the photonic rocket.

[silverslith]

My calculation regarding centripetal force required to keep the IPCS in a circular path at the distance of the heliopause (~4x plutos orbit) was intended to show that the velocity of 0.1c is pretty darn fast. Obviously to accelerate to that speed with such a path the g's required for maintaining the circular path will climb to 4.5g at 0.1c(unless I fluffed the calc). This would have to be supplied by the EM drive (though requiring no energy) in addition to the acceleration needed to get there. I've no idea whether the mag field is strong enough out there to make it possible.

I'm not sure that your energy requirement calc is valid. Or a motorcycle of 100kw couldn't accelerate at 1g. Which they clearly do. I think maybe momentum is a better tool than energy for these totals but I'm no expert with only stage1 uni physics 20years ago. Or does it take more energy to accelerate a cannon shell to 1000m/s muzzle velocity from a plane flying at 1000m/s than one sitting on a tarmac:evil: . Maybe you're talking about induced current in the conductors moving thru the magnetic field. Once again I only know enough to know I don't know all the ramifications of this.

The conventional conductor rating you've quoted is probably for wires with plenty of plastic thermal insulation wrapped around them. I kept blowing the 0.25sqmm 20A resistance wire in my fuse box when I used my arcwelder. Replacing it with a 0.25sqmm copper wire fixed the problem, so I have personal experience that 80A/sqmm is fine for copper. If you cooled it to a couple of kelvin then a fair bit more would be handled.

I did calcs a few years ago based on vapor deposited type II's on mylar that gave me figures of 10x the weight for force supplied by earthmag. I'm finding it a lot harder to get info of the web now as every decent paper seems to need subscriptions these days. I'm sure the experiment you express interest in would be worthy. Nothing like a physical demo to capture peoples imagination.
If anyones wondering why the solar mag field looks so strange and is compressed against the heliopause, Its because its carried by the solar wind.

[silverslith]

Hard, slippery, and gives us electrons when heated:

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Technical Background
Amorphic Diamond is an acronym composed from syllables of "Amorphous Ceramic Diamond." It was intended to lower the tension of an apparent self-contradiction between the terms "diamond" which is crystalline and "amorphous" which means there is no long-range order to a material.
While crystalline diamond is immediately recognized in almost every society at all levels, it is almost unknown that there are actually two naturally-occurring crystal forms; cubic and hexagonal. Cubic is the "common" variety, while hexagonal diamond is truly rare. In nature diamonds grew slowly from liquid "melts" as the material cooled under extreme pressure. There was time for one single crystal pattern, usually cubic, to grow throughout the sample.

When a laser beam is focused upon a carbon surface a "fireball" of extremely hot carbon ions explodes outward. Upon striking a surface their impact briefly creates an impulse of very high pressure and the carbon material cools under this pressure to become diamond. The process is too fast for one crystal form to dominate and structures alternate randomly on a molecular scale between cubic and hexagonal. The result is a coating with the unique properties immediately associated with diamond, but without the long-range order that insures crystalline geometry.

In summary Amorphic Diamond is made from graphite carbon and laser light without toxic waste or noxious byproducts. As a conformal coating it is harder than natural diamond and "slicker" than Teflon. Because it condenses from such energetic precursors, there is chemistry at the interface with the material it coats; and Amorphic Diamond coatings become chemically bonded to almost any material compatible with the vacuum in which it must be deposited. Metals such as Ti, Al, Co, Fe, and most steels have been coated directly. Optical materials such as quartz, Ge, ZnS, and ZnSe; electronic materials such as Si and GaAs; and miscellaneous compounds such as plastic, glass, and even paper are routinely coated. Against abrasive wear, coatings of 1 mm (i.e. 1/10 the diameter of a hair) increase service lifetime by factors of 3 to 10. This means that wear lifetimes can be increased by factors of 1000 to 10,000 with Amorphic Diamond coatings thinner than the diameter of a human hair. Even more remarkable is that these coatings emit more electrons at a given temperature than any other material or artificial fabrication.

http://www.hafniumis...org/TechBkg.htm