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17

Almost Certainly Not 6 MW is a lot of power, and all of the proposed mechanisms can only sip at available power. (Or wouldn't work at all.) Efficiency As with anything that moves through a medium, most efficiency gains are realized by aero or aqua-dynamics. So a knife-nosed submarine would see more efficient movement forwards, but would have enormous power ...


6

Dyson Sphere, hm, no if your prerequisite is energy to matter conversion. It may depend on how much matter they need to satisfy their needs, how many of them there are, and all that. But using 100% of sun energy, in a 100% efficient way - they can make 4 million tons of matter per second. Or about 1.2e14 tons per year. This is a significant number, as mass ...


5

There is no strict lower limit to energy use for propulsion: The slower your craft, the more energy efficient it is. If you want to make your sub super efficient, you just have to compromise on speed, and vice versa. Unfortunately, speed is essential for civilian uses: Passengers want to reach their destination yesterday, and they are generally willing to ...


5

What is a sub's role? Engineering anything involves maximizing strengths whilst minimizing weaknesses within a specific framework of constraints. Unfortunately, it seems the baby might have been lost with the bathwater when focusing specifically on size and power whilst ignoring (or at least understating) questions of mission-lifetime, surge-demand, and ...


3

On the energy content of human waste The amount of energy remain in the gently used food varies widely based on the person and type of food. But, the highest figures I found during my searches was that about 25% of the original calories passed through undigested in the case of some kinds of nuts - the overall average being considerably lower in people with ...


2

6.1-megajoule, millimeter-wide, millisecond-long (6.1 gigawatt), 1-picometer wavelength, 300-exahertz laser pulse 1 picometer wavelength gives a photon energy of ~1.24MeV. That's comfortably into the hard x-ray, gamma ray regime. From the relevant NIST tables, you can see that this gets a mass attenuation coefficient of somewhere between 1.8 and 2cm2/g. ...


2

Now, can a person live off solely energy? (since elements can be converted to a metal of choice via energy). Trivially, yes. You can synthesise all the materials you need, so ultimately you can support life as you see fit. As MolbOrg pointed out though, the total amount of matter available from a sunlike star if you're merely converting its electromagnetic ...


1

Unlimited Energy Doesn't Necessarily Mean Utopia From a theoretical standpoint, yes, you can take in sunlight and Hydrogen from the solar wind and combine the two into everything society needs. From a practical standpoint... Turning Hydrogen into Iron is going to require repeatedly fusing elements, then running the results through a separation process, since ...


1

No, no non nuclear method can generate useful levels of power. Ocean currents require you to be affixed in a location and have extensive support technology requirements that weigh a lot. Unless you want your submarine affixed to the ground floating in a hoop, the submarine won't generate useful powers. Submarines are required to move around, often in ...


1

The comments already explain that moving on the surface at similar speed will always require less energy. But if not so much extra energy is required and there are other problems to solve it might become plausible. A strong and constant stream is running along the coast. A couple of islands narrow and long break the stream in such a way that the current ...


1

One example: Say we count ambient temperature as kinetic energy. And say someone wants to lift 100 kg by 100 m. Acceleration due to gravity is about 10m/s^2. Multiplying to get the desired gravitational potential energy, they need to absorb 100 kJ. The specific heat capacity of air is about 1 kJ / kg K (https://www.ohio.edu/mechanical/thermo/property_tables/...


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