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--- drawingboard:components:propulsion:air [2024/06/05 15:31] – tailkinker
+++ drawingboard:components:propulsion:air [2024/06/06 11:25] (current) – [Jet Engines] tailkinker
@@ Line 40: / Line 40: @@
 |   0  |Modern Turbofan    |  Thrust \[di] 45 + 45   |  Thrust \[di] 750  |  Mass \[mu] 20  |  Yes  |
 |  +1  |Hydrogen Turbofan  |  Thrust \[di] 45 + 25   |  Thrust \[di] 60   |  Mass \[mu] 20  |  Yes  |
-|  +2  |Fusion Turbofan    |  Thrust \[di] 90 + 25   |  --                |  Mass \[mu] 40  |       |
+|  +2  |Fusion Turbofan    |  Thrust \[di] 90 + 25   |  \[dg]             |  Mass \[mu] 40  |       |
+\[dg]Fuel is not needed for the fusion turbofan, but burning reaction mass allows it to exceed its service ceiling
-Volume for all engines listed above, in cubic meters, is equal to their mass divided by 75.
+Fuel is in liters per hour.  Volume for all engines listed above, in cubic meters, is equal to their mass divided by 75.
 ==== Afterburner ====
 Some jet engines can be fitted with an afterburner.  If you choose to fit a compatible engine with an afterburner, increase the mass by 10% and the cost by 50%.  While the afterburner is running, your vehicle's top speed is increased by 25%, but your engine drinks fuel //five times faster!//
+==== Service Ceiling ====
+Some of the jet engines in the table above might look sub-optimal.  In the case of the pulse jet, this is correct:  This is just an awful system, with its only benefit being its cost.  But in other cases, the tradeoff is service ceiling.  Beyond a certain altitude, there isn't enough air pressure or oxygen content to keep the engine running.
+Of course, technology helps with this, and better engines allow for higher service ceilings.
+^  TR  ^Type               ^  Service Ceiling  ^
+|  -1  |Pulse Jet          |  1,000m           |
+|  -1  |WWII Turbojet      |  15,000m          |
+|  -1  |Cold War Turbojet  |  20,000m          |
+|  -1  |Cold War Turbofan  |  18,000m          |
+|  -1  |Ramjet             |  23,000m          |
+|   0  |Turbo-Ramjet       |  26,000m          |
+|   0  |Modern Turbofan    |  20,000m          |
+|  +1  |Hydrogen Turbofan  |  25,000m          |
+|  +2  |Fusion Turbofan    |  28,000m          |
+=== Fusion Turbofans and Fuel ===
+A fusion turbofan burns no fuel when below 28,000 meters, where there's sufficient air to use as reaction mass.  However, you can carry reaction mass for it, and just toss it into the heating chamber.  This will allow your fusion turbofan to exceed its service ceiling and travel into space, effectively becoming a fusion //rocket//.  When used in this mode, a fusion turbofan will burn water as though it were fuel, at a rate equal to its Thrust divided by 600.
+===== Space Drives =====
+If your vehicle is a spacecraft that is capable of operating in atmosphere, you may want to use your space drive as though it were an aircraft engine.  This is allowed, for certain types:  chemical fuel rockets, metal oxide rockets, fission and fusion rockets, and antimatter thermal rockets.
+In such cases, you'll need to find your vehicle's maximum speed in atmosphere.  To find this, divide your Thrust by your Drag, and multiply by 7,000.  Then take the square root of the result.  Drop fractions, just to make your life easier.