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Old 08-04-2020, 12:33 AM   #21
Say, it isn't that bad!
 
Join Date: Dec 2013
Default Re: In which I post about a TL9 solar system

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Originally Posted by maximara View Post
I think that is more due to the limitation on what you can do with a CISC based chip. The iPhone uses a 7nm ARM chip (A12) and the A14 (a Bionic-based, 5 nm 12-core CPU) is supposed to show up in a Mac in 2021.

Though we are going to hit the quantum tunelling wall soon even with functional prototype 3 nm chips due out in 2021. I'm not sure if the gate-all-around FETs for 2nm chips is going to pan out and that may be the limit with RISC based instruction sets.
CISC or RISC doesn't change the fundamental size of transistors; although Arm being a (relatively) modern design with little baggage does help decrease the number of transistors needed.

Ultimately, though, Apple changing from x86 to Arm may be an indication that they are attempting to get around the soft wall of transistor size as much as practical.
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Old 08-04-2020, 01:04 AM   #22
AlexanderHowl
 
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Default Re: In which I post about a TL9 solar system

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Originally Posted by Say, it isn't that bad! View Post
I'm not sure what you mean by "fusion engine"; the Fusion Pulse Drive on Spaceships p22 gets 5 mps per fuel tank at TL9 and 10 mps at TL10, while the Fusion Rocket on p23 gets 12 mps at TL9, and 60 mps at TL10; neither seem to match the numbers you gave.

I'm using an auto-calculating spreadsheet that seems to have come with "Pyramid 3/079:Space Atlas" to calculate transfer times. It seems lacking on places to enter the minimum or maximum delta-V you're using.

Tolerances over time; although I'd worry more about peak exposure.
A fusion engine is just another name for a fusion rocket. 8 fuel tanks give 12 mps per tank, times 1.2 for eight tanks, for a total of 115.2 mps. It is 3 billion miles to Saturn and, when you divide 3 billion miles by 55 mps, you get ~55 million seconds or 1.72 years. It takes 0.06 years to accelerate at 0.005g to 55 mps and 0.06 years to decelerate from 55 mps. Hoffman transfers are fine for unmanned missions, but no one wants to spend 10 years traveling to Saturn (2 years is bad enough).
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Old 08-04-2020, 01:27 AM   #23
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Default Re: In which I post about a TL9 solar system

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Originally Posted by AlexanderHowl View Post
A fusion engine is just another name for a fusion rocket. 8 fuel tanks give 12 mps per tank, times 1.2 for eight tanks, for a total of 115.2 mps. It is 3 billion miles to Saturn and, when you divide 3 billion miles by 55 mps, you get ~55 million seconds or 1.72 years. It takes 0.06 years to accelerate at 0.005g to 55 mps and 0.06 years to decelerate from 55 mps. Hoffman transfers are fine for unmanned missions, but no one wants to spend 10 years traveling to Saturn (2 years is bad enough).
...I completely forgot about the Delta-V increase for having more fuel tanks.

Excuse me, need to revise that post about Brachistochrone Transfers and Ceres-Jupiter transfer stations...

Edit: Done.
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Old 08-04-2020, 01:44 AM   #24
AlexanderHowl
 
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Default Re: In which I post about a TL9 solar system

Anyway, 55 mps is around the best that you can do with a TL9 fusion rocket without compromising protection or capacity. If we assume one control room, one fusion rocket, three armor, and eight tanks, that leaves us with seven systems. You can try a two year mission without armoring the entire spaceship, but I doubt that anyone will come along for the trip.

If you are transporting human passengers at TL9, I would not really use anything less than SM+12 for interplanetary travel in the Inner Sol System or less than SM+14 for interplanetary travel in the Outer Solar System (radiation protection and spin gravity are required). At TL10, medicine can fix radiation damage and counter zero-g degeneration, and the propulsion technology improves, so you can reduce the minimum size to SM+6 and SM+8 respectively.
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Old 08-04-2020, 01:56 AM   #25
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Default Re: In which I post about a TL9 solar system

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Anyway, 55 mps is around the best that you can do with a TL9 fusion rocket without compromising protection or capacity. If we assume one control room, one fusion rocket, three armor, and eight tanks, that leaves us with seven systems. You can try a two year mission without armoring the entire spaceship, but I doubt that anyone will come along for the trip.

If you are transporting human passengers at TL9, I would not really use anything less than SM+12 for interplanetary travel in the Inner Sol System or less than SM+14 for interplanetary travel in the Outer Solar System (radiation protection and spin gravity are required). At TL10, medicine can fix radiation damage and counter zero-g degeneration, and the propulsion technology improves, so you can reduce the minimum size to SM+6 and SM+8 respectively.
The TL9 advanced fusion pulse drive gets 20mps, so I'm somewhat confused on that wouldn't be used.

That is good to know; however, it sounds like I'll need to hold off on designing crewed ships in general until I get Spaceships 5, if I want to take cosmic rays into account (which I do).

Edit: I had a question which wasn't answered; cosmic rays have an armour divisor of (100); how does hardened armour affect it? B47 suggests the armour divisor becomes (10).
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Old 08-04-2020, 02:12 AM   #26
AlexanderHowl
 
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Default Re: In which I post about a TL9 solar system

Cosmic radiation ignores Hardened, it is, by definition, Cosmic. More seriously, armor does not protect against radiation accept as extra mass, so Hardened is worthless against radiation, as cosmic radiation only divides PF by 100, rather than DR by 100.

With the fusion pulse engine, the problems are engine expense, reaction mass expense, and in-situ resource utilization. Advanced pulse engines cost twice as much as fusion rockets, which means that a single one would be 2/3 the cost of the vehicle. Hydrogen costs 4% the cost of nuclear pellets but produces 60% of the delta-v, so the fuel is 15 as expensive per mps. Finally, any refinery can turn ice into hydrogen, meaning that the spaceship could potentially refuel on its own or that colonies could resupply them easily, while nuclear pellets require a massive industrial complex to produce.

Last edited by AlexanderHowl; 08-04-2020 at 02:24 AM.
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Old 08-04-2020, 02:23 AM   #27
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Default Re: In which I post about a TL9 solar system

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Cosmic radiation ignores Hardened, it is, by definition, Cosmic. More seriously, armor does not protect against radiation accept as extra mass, so Hardened is worthless against radiation, as cosmic radiation only divides PF by 100, rather than DR by 100.
Good to know.
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With the fusion pulse engine, the problems are engine expense, fuel expense, and in-situ resource utilization. Advanced pulse engines cost twice as much as fusion rockets, which means that a single one would be 2/3 the cost of the vehicle. Hydrogen costs 4% the cost of nuclear pellets but produces 60% of the delta-v, so the fuel is 15 as expensive per mps. Finally, any refinery can turn ice into hydrogen, meaning that the spaceship could potentially refuel on its own or that colonies can resupply them easily, while nuclear pellets require a massive industrial complex to produce.
...I completely missed this when reading about fuel-tanks: "and the cost of each fuel tank system without fuel".

...Yeah, there is a difference between $75 million to fill a 1.5kt fuel tank, and $3 million. I can see a government paying the former for their warships; but for a private enterprise, the latter fee is much more palatable.
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Old 08-04-2020, 02:55 AM   #28
Say, it isn't that bad!
 
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Default Re: In which I post about a TL9 solar system

It appears that, for cosmic rays, an active electrostatic field could provide "viable" protection:

https://ntrs.nasa.gov/archive/nasa/c...0090022229.pdf

https://www.nasa.gov/pdf/718390main_...Protection.pdf
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Old 08-04-2020, 06:05 AM   #29
dcarson
 
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Default Re: In which I post about a TL9 solar system

Inspiration art, http://3mpub.com/mccollum/images/cloudsat.jpg art for The Clouds of Saturn by Michael McCollum.
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Old 08-04-2020, 06:29 AM   #30
maximara
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Default Re: In which I post about a TL9 solar system

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Originally Posted by Say, it isn't that bad! View Post
CISC or RISC doesn't change the fundamental size of transistors; although Arm being a (relatively) modern design with little baggage does help decrease the number of transistors needed..
I was thinking more along the number of transistors to do the some thing.

"The RISC ISA emphasizes software over hardware. The RISC instruction set requires one to write more efficient software (e.g., compilers or code) with fewer instructions. CISC ISAs use more transistors in the hardware to implement more instructions and more complex instructions as well." - RISC vs. CISC Architectures: Which one is better?

Though this is no few lunch: "The RISC architecture will need more working (RAM) memory than CISC to hold values as it loads each instruction, acts upon it, then loads the next one."

This explains why the A12z WWDC 2020 Special Event Keynote Mac had 16 GB of RAM compared to 8 GB one tends to se in the i5 and i7 low end Macs.

IIUC one of the issues Intel is having at going below 14 nm is heat and in space heat is a problem as the only option for cooling things off is radiation. The x86 architecture hasn't exactly been cool (I still remember the jokes about the Pentium space hear with the very first PC to use that chip)

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Ultimately, though, Apple changing from x86 to Arm may be an indication that they are attempting to get around the soft wall of transistor size as much as practical.
If that is the case then Apple planned for the really long game as the A4 (2014) used a 45 nm process while its x86 (Haswell-DT) used a much smaller 22 nm process. The fact that the WWDC mac handled x86 optimized code as well as it did shows how far software has come (the RISC PowerPC chip's emulation was annoyingly slow)
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