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01/01/14 11:59 PM
67.239.109.174
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So there's ASF and conventional fighters. The conventional fighters further divide into ICE and fusion. I specify this because there is a Strategic Operations rule that makes fusion conventionals more efficient than ASF conventionals, which makes them different than I.C.E. conventionals(That or it brings the two types of engines in line in terms of fuel consumption... I don't know.).
I don't own the Strategic Operations rulebook, and every attempt to find a download of it just leads to the offering party to make prerequisites such as installing some other thing which I don't care about. So, basically, how do you determine how much fuel is consumed by each type of fuel consuming fighter per thrust point? How can you determine combat radius with the previous information?
Other stuff about fuels and ranges would be appreciated.
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Cray
01/02/14 06:38 PM
71.47.122.85
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So, basically, how do you determine how much fuel is consumed by each type of fuel consuming fighter per thrust point?
Aerospace fighters get 80 points of fuel (hydrogen) per ton. That's 12.5kg per fuel point.
Conventional fighters (fusion) get 160 points of fuel (hydrogen) per ton. That's 6.25kg per fuel point.
Conventional fighters (turbine) get 320 points of fuel (petrochemical) per ton. That's 3.125kg per fuel point.
You have to check TROs for the capacity of individual fighters. Aerospace fighters mostly have 5 tons of fuel, but conventional fighters are all over the place (usually 2 to 4 tons).
Using overthrust points increases fuel consumption to 2 fuel points per thrust point, if I recall correctly.
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How can you determine combat radius with the previous information?
Well, let's start with basic range calculations.
When you're traveling on the low altitude maps, you'll be covering 0.5km per hex (one BT map) per turn (10 seconds). That burns fuel fast and represents serious afterburning dodging and jinking. For long-range flight, forget low altitude maps. Move to the high altitude scale.
The high altitude scale basically uses the atmospheric hexes of the space map. You're covering 18km per hex per turn (60 seconds.) The various altitude levels range from 0 to "interface." Conventional fighters can use row 0 (ground level to 18,000m) and row 1 (up to 36,000m). Aerospace fighters can use any altitude band and, of course, go into space.
Movement on the high altitude map is not like a BattleMech on the ground. You don't spend 6 thrust points and move 6 hexes. Rather, it's more like spending thrust in space (where velocity can build up until you run out of fuel) but with an aerodynamic drag component (that both limits maximum velocity and steals some velocity points per turn). How's that work? Step by step...
Maximum velocity: this is listed in the high altitude movement rules of Total Warfare. The ones I recall offhand are 2 hexes per turn for the ground row and 3 hexes per turn for row 1. (It gets up to 15 hexes per turn at the interface, but if you're going to fly higher than row 1 then you might as well skip up to space and avoid the drag problem. For Earth, low orbital velocity is about 26 hexes per turn.) Fighters have plenty of thrust and could exceed a row's maximum velocity, but doing so inflicts, like, 5 points of damage per hex/turn of velocity over the row's limit. So obey the speed limit.
Drag: Drag is treated as a speed penalty of 1 every turn. If you want to offset that, you need to spend a point of thrust.
Alright, so you've got maximum velocity for an altitude and drag. How do they play together with thrust?
Well, basically, you spend thrust points to accelerate (2 thrust points to increase speed by 1 hex/turn of speed, per p. 79 TW). After reaching your desired cruising speed, you need spend 1 thrust point per turn to offset drag. Then you get to cruise at your set speed for merely 1 fuel point per turn (per thrust point).
So, say you're taking your turbine-powered MechBuster on an intercontinental deployment limited to internal fuel (2 tons) only. That's 640 points. Figure (arbitrarily) you burn 80 points taxiing, climbing, accelerating, circling, and landing, leaving 560 points for travel. How far can you go?
Well, as a conventional fighter, the MechBuster can only get to row 1 and a max speed of 3 hexes per turn. But that's good: after spending 6 fuel points to reach speed 3, you can sustain speed for 1 thrust point to fight drag until the cows come home. In other words, you cover 3 hexes per turn for 1 fuel point.
So, 560 fuel points could let you cover (560 x 3) = 1680 hexes in 560 turns. What's that in real world numbers?
A high altitude hex is 18km. A turn is 1 minute. So that's 1680 x 18 = 30,240km in 560 minutes (9 hours, 20 minutes). Not quite around the world, but not bad.
Notice you cover 30,240km in less than 10 hours? Fast, right? Well, look at the hex size and turn length:
18,000 meters / 60 seconds = 300 meters per second.
In other words, 1 hex per turn is just under mach 1. The 'MechBuster supercruised at mach 2.7 a distance of 30,240km without refueling or using drop tanks, and only using about 2 tons of fuel.
Meanwhile, an aerospace fighter could've used 40 points of fuel (0.5 tons to an aerospace fighter) to climb to orbit, circled the globe for days at mach 25, and glided to a landing.
Combat radius is rather different and depends on your assumptions: how many fuel points do you reserve for combat? How much emergency reserve fuel do you leave? What altitude does the fighter cruise at before and after combat, and at what speed? Even if a fighter only uses half its fuel to fly to and from combat, that 'MechBuster would have a combat radius of about 7,500km.
Do you have a specific fighter or situation you'd like analyzed?
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I don't own the Strategic Operations rulebook, and every attempt to find a download of it just leads to the offering party to make prerequisites such as installing some other thing which I don't care about.
DriveThruRPG.com and BattleCorps offer downloadable copies of Strategic Operations without the baggage, just the hit on your bank account.
Mike Miller, Materials Engineer
Disclaimer: Anything stated in this post is unofficial and non-canon unless directly quoted from a published book. Random internet musings of a BattleTech writer are not canon.
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Retry
01/02/14 10:30 PM
67.239.109.174
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So one thrust point is equal to one fuel point, except with overthrust? Your fighter's tonnage has no effect on fuel consumption?
So for conventional fighters, for getting around the surface of a planet(via high alt map) having a big engine is useless. Hmm... Maybe with the exception of retreating to the low altitude map to avoid getting intercepted by some ASF, perhaps.
How about the alternate rule that makes conventional fighters(fusion) more fuel efficient than ASF(fusion)?
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Retry
01/02/14 11:00 PM
67.239.109.174
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So Conventional fighters can cover 3,240 kilometers per hour. I think?
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Cray
01/03/14 12:13 PM
97.101.96.171
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So one thrust point is equal to one fuel point, except with overthrust? Your fighter's tonnage has no effect on fuel consumption?
Correct. Heavier fighters are more fuel efficient. This is not true for support vehicle aircraft, though.
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So for conventional fighters, for getting around the surface of a planet(via high alt map) having a big engine is useless.
For long-range travel, yes. For having thrust reserves for bomb payloads and combat maneuvering, extra thrust is useful.
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How about the alternate rule that makes conventional fighters(fusion) more fuel efficient than ASF(fusion)?
Oops, I need to update fuel consumption estimates. My last post was wrong. Per p. 34 Strategic Operations, the rules for conventional fighters is as follows:
First, notice the top of my last post for fuel points-per-ton by fighter type. Conventional fighters get more fuel per ton than aerospace fighters to begin with.
Second, per p. 34, normal fuel consumption for any flying, fuel-using vehicle is 1 fuel point per safe thrust point and 2 fuel points per maximum thrust point. That applies to DropShips, aerospace fighters, and conventional (fusion) fighters. However, conventional fighters (turbine) always use half a fuel point per safe thrust point, or 1 fuel point per maximum thrust point. (This means that my estimate for the MechBuster was only half its actual range.)
Optionally (i.e., players must agree to this), page 34 StratOps allows conventional fighters (fusion) to use 0.5 fuel points per safe thrust and 2 fuel points per maximum thrust point.
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So Conventional fighters can cover 3,240 kilometers per hour. I think?
60 minutes x 3 hexes / minute x 18km/hex = 3,240 km per hour. So, yes.
Edited by Cray (01/03/14 12:22 PM)
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Retry
01/04/14 01:29 AM
67.239.109.174
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Thanks, that helps.
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