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ft:planets [2015/08/30 16:45] – samft:planets [2020/07/08 21:27] (current) – sam
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 //More Thrust// provides some rules for handling planets (p.13), but they are very simplistic and don't fit in well with the vector movement system introduced in the //Fleet Book//. As such, I've made an attempt at modelling planets in a bit more detail and using the vectored movement rules. If you're using cinematic movement, then these rules won't make much sense. //More Thrust// provides some rules for handling planets (p.13), but they are very simplistic and don't fit in well with the vector movement system introduced in the //Fleet Book//. As such, I've made an attempt at modelling planets in a bit more detail and using the vectored movement rules. If you're using cinematic movement, then these rules won't make much sense.
  
-{{indexmenu>planets}} +All these rules assume that a scale of 1" = 1,000km and 1 turn = 1,000s. See the page on [[./planets/terrain|modelling planets]] for details.
- +
-===== Units of Measurement ===== +
- +
-Normally, Full Thrust doesn't care about real world measurements, and simply uses the 'turn' and the 'movement unit' (depicted as " in the rules, and often taken as an inch on the table top). If we start using real world objects though (such as planets), it becomes necessary to translate these abstract terms into real world units. +
- +
-A turn is taken to be fifteen minutes, and 1" is assumed to represent one thousand kilometres. From this, we can work out that a ship thrust factor of 1 is equivalent to an acceleration of approximately 1.125 ms-2. To keep things simple, I'll assume that 1g is equal to a thrust factor of 8. +
- +
-Unless you have a very big table, you might want to consider using 1" = 1cm on the table top. This provides a lot more room for manoeuvre around the planets, and also makes modelling planets easier. +
- +
-===== Modelling Planets ===== +
- +
-The easiest way to model a planet is to cut a circle out of a piece of cloth or paper, and simply place it on the table top. This also makes it very easy to place planetary installations on the planet, since they can be drawn/placed on top of the planet. +
- +
-Another easy way is to buy a polystyrene sphere from a craft shop, cut it in half to form a hemisphere and +
-paint it to look planet-like. Most craft shops don't see to have spheres larger than 10cm in diameter, though there's at least one online shop that does very large [[http://www.grahamsweet.com/polystyrene-balls/polystyrene-styrofoam-balls-spheres.php|Polystyrene Balls]], up to 2m in diameter. They can be pricey though, and take up a lot of space. +
- +
-Another technique is to use round MDF bases. I get mine from [[http://www.productsforwargamers.com/mdf_bases.html|Products for Wargamers]], who will do custom cut bases up to 60cm in diameter. Once painted, they are more sturdy and look better than a bit of cloth or paper, and are cheaper and easier to store than polystyrene hemispheres. +
- +
-====== The Effects of Gravity ====== +
- +
-Every large body, from planets to stars and black holes, +
-will exert gravitational attraction on nearby ships. This +
-attraction will act as an acceleration directly towards +
-the body, just as if the ship were thrusting towards it. +
-Since a thrust of 8 is considered to be equivalent to 1g, +
-so the force of gravity at the surface of an Earth-like +
-world will cause an acceleration of 8". +
- +
-Each planet is considered to have gravity bands which reach +
-from its surface out into space. The first band is out to 4", +
-the second to 8", the third to 16" - and so on, doubling in +
-distance each time. For an Earth-like world, the gravity in +
-the first 3 bands is 6"/turn, 2"/turn and 1"/turn. This means +
-that any ship that begins a turn within 4" of Earth will get +
-dragged towards the surface by 6". +
- +
-The steps to work out the effects of gravity are as follows. +
-We assume that vectored movement is being used, and that +
-a //vector marker// is used to show each ship's position +
-at the end of the next movement. +
- +
-At the beginning of movement, work out the distance +
-between the ship and the surface of the planet. If +
-the ship is outside any effective gravity bands for +
-that planet, then the planet has no effect (e.g., +
-outside 16" for an Earth-like world). +
- +
-Lookup the gravitational acceleration for that planet +
-for that range. There is a table below which lists +
-acceleration values for some common worlds. +
- +
-Work out the gravity vector from the ship towards the +
-centre of the planet for this acceleration. This vector +
-has a magnitude equal to the acceleration, and a +
-direction pointing to the centre of the planet. +
- +
-Apply the gravity vector to the ship's vector marker. +
- +
-Apply any acceleration due to the ship's thrust. +
- +
-Move the ship and its marker. +
- +
-It is the distance of the centre of the ship to the +
-surface of the planet that is important - the position +
-of the vector marker has no effect. +
- +
-===== Acceleration due to Gravity ===== +
- +
-The acceleration due to gravity on a ship depends on the size of the planet and the distance the ship is from it. For a planet of Earth size and mass, the following zones of influence are suggested. +
- +
- +
-^           ^                    ^ Acceleration at distance from surface      ^^^^^^^^ +
-^ Planet    ^ Diameter           ^  4"  ^  8" ^ 16" ^ 32" ^ 64" ^ 128" ^ 256" ^ 512" ^ +
-| Earth     | 13" (12,700km)     |  6"  |  2" |  1" | --  | --  | --   | --   | --   | +
-| The Moon  |  3" (3,475 km)     | 0.5" | --  | --  | --  | --  | --   | --   | --   | +
-| Mercury   |  5" (4,878 km)     | 0.5" | --  | --  | --  | --  | --   | --   | --   | +
-| Venus     | 12" (12,104 km)    |  4"  |  2" |  1" | --  | --  | --   | --   | --   | +
-| Mars      |  7" (6,787 km)     |  1"  | 0.5"| --  | --  | --  | --   | --   | --   | +
-| Jupiter   | 142" (142,200 km)  |  20" | 18" | 16" | 12" |  8" |  4"  |  2"  | 0.5" | +
-| Saturn    | 119" (119,300 km)  |   9" |  8" |  6" |  5" |  3" |  1"  | 0.5" | --   | +
-| Uranus    |  51" (51,200 km)   |   8" |  6" |  4" |  2" |  1" | 0.5" |  --  | --   | +
-| Neptune   |  49" (49,500 km)   |   8" |  6" |  4" |  2" |  1" | --   |  --  | --   | +
-| The Sun   |1392" (1,392,000 km)| 223" | 222"| 219"| 216"| 208"| 196" | 173" | 93"  | +
-| Model     | 10" (10,000km)     |   4" | 2"  | 1"  | --  | --  | --   | --   | --   | +
- +
- +
-Remember that the distances given above are the distance from the //surface// of the body. The Sun will not fit +
-into any sensible gaming area, and is given merely to show how insignificant everything else is. Even Jupiter would require at least 2.5m (at centimetre scales) to allow for manoeuvring at the edge of its gravity well. +
- +
-Where acceleration less than 1" is given, it can be ignored. However, this does mean that small worlds such as Mercury would have no effect, so it's listed anyway in case you want to use it. +
- +
-====== Examples ====== +
- +
- +
-===== Fast Fly-by ===== +
- +
- +
- +
-The following example shows the Light Cruiser +
-//Colbert// approaching a planet. At no point +
-does the //Colbert// apply any thrust of its +
-own. The world is slightly smaller than the Earth, +
-with statistics as follows: +
- +
-^           ^                    ^ Acceleration at distance from surface      ^^^^ +
-^ Planet    ^ Diameter           ^  4"  ^  8" ^ 16" ^ 32" ^ +
-| Model     | 10" (10,000km)     |   4" | 2"  | 1"  | --  | +
- +
-We begin the example with the //Colbert// 10,000 km (10") from the planet's surface. The //Colbert// has a current velocity of 12"/turn (as denoted by the red vector marker in the diagram). +
- +
-{{./graphics/orbits/orbit-1-1.jpg}} +
- +
-The gravitational acceleration at this point is 1"/turn, in a direction about 45 degrees to the //Colbert//'s current heading. This acceleration is applied to the vector marker (vector shown in green above). +
- +
-This moves the //Colbert// to its new location, somewhat closer to the planet but halfway around it.+
  
-{{./graphics/orbits/orbit-1-2.jpg}}+| {{:ft:graphics:planets_icon.png?nolink&160|}} | {{:ft:graphics:gravity_icon.png?nolink&160|}} | {{:ft:graphics:settlements_icon.png?nolink&160|}} | {{:ft:graphics:assault_icon.png?nolink&160|}} | 
 +|  [[./planets/terrain|Modelling Planets]]  |  [[./planets/gravity|Gravity]]  |  [[./planets/bases|Bases]]  | [[./planets/installations|Planetary Assault]]  |
  
-At the new distance of 6" (shown in red), the gravitational acceleration is 2"/turn. Again this is applied to the vector marker. Note that the marker is moved in the direction that the //Colbert// would be moved by gravity. 
  
 ====== Attacking a Planet ====== ====== Attacking a Planet ======
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 Heavy missiles aren't designed to enter an atmosphere, and have a chance of simply burning up on re-entry. For each missile, roll a die, modified by the 'torpedo' column above. On a 1+, the missile makes it through to the target. Heavy missiles aren't designed to enter an atmosphere, and have a chance of simply burning up on re-entry. For each missile, roll a die, modified by the 'torpedo' column above. On a 1+, the missile makes it through to the target.
  
-However, any missile that does hit the target is more effective, due to the extra shock wave produced by the atmosphere. Against unarmoured targets, //multiply// the damage by the missile column for that type of atmosphere. A typical heavy missile will do around 210 points of damage against a settlement (see below).+However, any missile that does hit the target is more effective, due to the extra shock wave produced by the atmosphere. Against **unarmoured** targets, //multiply// the damage by the missile column for that type of atmosphere. A typical heavy missile will do around 210 points of damage against a settlement (see below).
  
 === Salvo Missiles === === Salvo Missiles ===
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 Military installations may have point defence systems (against fighters or missiles) or Surface-to-Space weapons. An installation on an airless planetoid can use any weapon system used by ships, for the same cost. Military installations may have point defence systems (against fighters or missiles) or Surface-to-Space weapons. An installation on an airless planetoid can use any weapon system used by ships, for the same cost.
  
-See [[./planets/installations]] for some sample designs.+==== Other Rules ==== 
 + 
 +{{indexmenu>planets}} 
ft/planets.1440953114.txt.gz · Last modified: 2015/08/30 16:45 by sam