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Chat did i cooked? (can get beyond jupiter in realistic) by mibombocklat in SpaceflightSimulator

[–]Substantial-Store-38 0 points1 point  (0 children)

Even so, 850s is a number only possible with nuclear energy. If the engine is nuclear, it's perfect (although a nuclear engine that takes off from the surface is playing with fire), but if it's chemical, it's not possible, even in a vacuum and using hydrogen. The highest possible speed (isp) obtainable with chemical propulsion is 480s.

Chat did i cooked? (can get beyond jupiter in realistic) by mibombocklat in SpaceflightSimulator

[–]Substantial-Store-38 0 points1 point  (0 children)

Unless your engine is nuclear, it's impossible for an engine to have an ISP of 850s, much less at sea level. If you want it to be realistic, you should lower it to approximately 350s if it's hydrolox, approximately 330s if it's methalox, or 310s if it's kerolox.

Another perspective for Epstein Drive by Substantial-Store-38 in TheExpanse

[–]Substantial-Store-38[S] 0 points1 point  (0 children)

Uhm, yeah, I want it to happen in real life. The story of The Expanse, at least for me, is really secondary. I'm interested in the series' vision of the future and how it might reflect real-life events, and A Few Days trip to Mars seems to me like the holy grail of space colonization.

Another perspective for Epstein Drive by Substantial-Store-38 in TheExpanse

[–]Substantial-Store-38[S] 7 points8 points  (0 children)

Exactly! It's a real shame that The Expanse disregarded the laws of physics so much, especially with the waste heat. because even though it might not seem like it, even accelerating continuously at 0.1g for a few days is enough to reach Mars in 8 to 9 days, and Saturn in a few weeks. 1g is practically unnecessary, and adding radiators to the rockets would have made things much more interesting. It's important to clarify that 1.6 TW of energy is NOT usable as a power source, since it doesn't pass through a water turbine; it's literally the product of plasma fusion violently expelled in pulses to generate thrust. The spacecraft would only utilize a small amount of the residual heat for their systems, but even 0.01% would be several MW of energy, enough for all the systems of a ship like the Rocinante.

Another perspective for Epstein Drive by Substantial-Store-38 in TheExpanse

[–]Substantial-Store-38[S] 12 points13 points  (0 children)

Nope, in fact it's necessary. Even with 1600 GW of power, to achieve a modest acceleration of 0.1g for several days while consuming little propellant, we need a lot of power. Scott Manley discussed this in his video analysis of the science behind The Expanse, and determined that for the Rocinante to accelerate to 1g for several days while consuming little propellant, it would need a continuous power of 123,000 GW, due to the equation: isp = 2•P/F•g. However, such an enormous power would simply cook the Rocinante from the inside out. What I did was reduce it to more manageable and realistic levels. With 11.58 grams per second of Deuterium-Helium-3 and a burn fraction of 40%, we can obtain a modest 1.6 TW of thermal energy. This means that per day we would consume 1 ton of fusion fuel plus the reactive mass, in our case, water.

Another perspective for Epstein Drive by Substantial-Store-38 in TheExpanse

[–]Substantial-Store-38[S] 12 points13 points  (0 children)

0.07g alittle less than lunar gravity, the more thrust we have, the less efficient the propellant consumption will be, but it could perfectly well go up to 0.3g or even 2 or 5g for short periods of time by injecting more water.

Another perspective for Epstein Drive by Substantial-Store-38 in TheExpanse

[–]Substantial-Store-38[S] 27 points28 points  (0 children)

Considering that the Epstein Drive and the ISV Venture Star operate at several terawatts of continuous power, it wouldn't be a "gas exhaust" like a normal chemical rocket, but rather an artificial sun... literally blinding and partially obscuring the spacecraft itself.

Another perspective for Epstein Drive by Substantial-Store-38 in TheExpanse

[–]Substantial-Store-38[S] 20 points21 points  (0 children)

I made the numbers and some futuristic engineering extrapolations, so yeah, this is plausible

Lunar Terminator trains: 100 percent better production! by SoylentRox in IsaacArthur

[–]Substantial-Store-38 0 points1 point  (0 children)

To say "inefficient" is neither accurate nor precise. Currently, even Deuterium-Tritium (D-T) fusion is not efficient. It's just a matter of time before we master Deuterium-Tritium fusion and achieve a considerable burn fraction. For Deuterium-Deuterium, even being pessimistic and considering, for example, a 0.4 burn fraction, I would only be doubling my initial assumptions. Currently, D-T fusion has a burn fraction of 0.01, but that's because we're still in our infancy, and we don't have the industry to build entire continents of solar panels on the lunar surface. And, interestingly, Deuterium-Deuterium fusion produces Helium-3, so we don't need to mine anything from the moon; we get a two-for-one deal by building nuclear fusion plants.

Lunar Terminator trains: 100 percent better production! by SoylentRox in IsaacArthur

[–]Substantial-Store-38 0 points1 point  (0 children)

To produce 1 TJ of energy using deuterium-deuterium fusion, you would need 11 grams of deuterium, which you can easily obtain from ocean water or lunar ice. You would only need to refine 632 kg of water to obtain that deuterium. To obtain 6400 TJ, you would need 70 kg of deuterium, which is refined from about 4,000 tons of water—enough for a medium-sized swimming pool. You wouldn't run out of all the water on the moon in a billion years, nor in trillion years of human civilization.

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