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PDF versions of YAGS can be downloaded for free from the links below. See Downloads for the full list of rules.

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YAGS is released under the GNU Public License, and as such the full set of source documentation is available, as well as the final PDFs above.

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All content on this site is copyright Samuel Penn, © 2019. All textual content is licensed under the GPL version 2. Original photographs may be considered public domain.

For questions and comments, contact sam@notasnark.net.

scifi:spacecraft:drives

Space Drives

Fuel Types

For a typical chemical rocket, the fuel and propellant are the same thing. For Nuclear rockets the fuel and propellant are different things. The fuel powers the reactor, and the propellant is thrown out the back.

See:

Kerolox

Density: 14
Max Impulse: 4.7

Liquid Oxygen and RP-1. Denser and requires less cryogenic cooling than liquid hydrogen.

Hydrolox

Density: 4
Max Impulse: 5.3

Liquid Oxygen and Liquid Hydrogen. Very low density but high efficiency without being insanely dangerous. The cryogenic needs complicate things though.

Methalox

Density: 10
Max Impulse: 4.6

Liquid methane and liquid oxygen.

Liquid Hydrogen

Density: 1
Impulse: ~

Generally used as propellant in nuclear or plasma engines.

Real Tech (TL 8)

Real Stats

From: https://youtu.be/D4SaofKCYwo?t=2180

Engine J-2 J-2S J-2T (250K) XRS-2200 RS-2200 RS-25 Raptor
Type Bell Bell Aerospike/C Aerospike/L Aerospike/L Bell Bell
Fuel Hydrogen Hydrogen Hydrogen Hydrogen Hydrogen Hydrogen Methane
Thrust (sl) 486kN 731kN 909kN 1,917kN 1,859kN 1,960kN
Thrust (vac) 1,033kN 1,138kN 1,112kN 1,184kN 2,201kN 2,278kN 2,150kN
Isp (sl) 200s 290s 339s 347s 363s 330s
Isp (vac) 424s 436s 441s 436s 455s 453s 355s
Expansion 27:1 40:1 80:1 58:1 173:1 69:1 35:1
TWR 73:1 69:1 63:1 35:1 83:1 73:1 107:1
Dimensions 3.4h2.1d 2mh 4.2h2.4d 3.1h1.3d
Weight 1.8t 3.5t 1.5t

Game Stats

The “/a” and “/v” engines are variants designed for optimal atmosphere (sea level) and vacuum operation.

The environment is where the engine is actually being used. “/a” engines tend to operate in both environments, though are less suited to vacuum. Most “/v” engines perform self-disassembly at sea level.

Aerospikes work well in both environments.

Modern Day (TL 8)

The following drive types are based on real technology, simplified for purposes of the game.

Engine dT Mass (t) Thrust Impulse Fuel Type Density Environment
Merlin/a ¼ 0.5 850 2.8 Kerolox 14 Atmosphere
Merlin/v ½ 1.0 980 3.1 Kerolox 14 Vacuum
Raptor/a ½ 1.5 1,960 3.3 Methalox 10 Atmosphere
Raptor/v 1 2.5 2,150 3.5 Methalox 10 Vacuum
F-1/a 2 8.4 6,770 2.6 Kerolox 14 Atmosphere

Plausible Future (TL 9)

Engine dT Mass (t) Thrust Impulse Fuel Type Density Environment
RD-4/a ¼ 1 900 3.9 Kerolox 14 Atmosphere
RD-4/a ¼ 1 900 4.2 Kerolox 14 Vacuum
RD-4/v 2 2 1,000 4.8 Kerolox 14 Vacuum
RD-2/a ½ 2.5 3,000 3.7 Methalox 10 Atmosphere
RD-2/a ½ 2.5 3,000 4.0 Methalox 10 Vacuum
RD-2/v 4 5 3,200 4.5 Methalox 10 Vacuum
Chem-B/a 1 10 4,000 3.5 Methalox 10 Atmosphere
Chem-B/a 1 10 4,000 3.8 Methalox 10 Vacuum
Chem-B/v 2 20 4,200 4.5 Methalox 10 Vacuum
Aerospike 1 15 1,000 3.8 Methalox 10 Atmosphere
Aerospike 1 15 1,000 4.5 Methalox 10 Vacuum
Aerospike 3 30 2,500 3.8 Methalox 10 Atmosphere
Aerospike 3 30 2,500 4.5 Methalox 10 Vacuum
Chem-3 3 30 7,500 4.0 Methalox 10 Vacuum
Chem-3X 3 30 5,000 4.2 Methalox 10 Vacuum
Nuclear-3 3 30 500 8.0 Hydrogen 2 Vacuum
RCS 1 100 3.2 Mono 12 Vacuum

Implausible Future (TL 10)

Engine Mass (dT) Thrust Impulse Fuel Type Density Environment
Chem-1 1 7,500 4.2 Methane 10 Atmosphere
Chem-3 3 7,000 4.5 Methane 10 Vacuum
Nuclear-3 3 700 12.0 Hydrogen 2 Vacuum

Far Future (TL 11)

Engine Mass (dT) Thrust/dt Impulse Fuel Type Density Environment
Nuclear-3 3 950 20.0 Hydrogen 2 Vacuum
scifi/spacecraft/drives.txt · Last modified: 2020/02/01 22:44 by sam