The subject of Full Steam:1889 is aerial combat in the Martian Skies between the wooden cloudfleets of the Martian princes and the armored aerial gunboats of Queen Victoria's Royal Navy.  This game is set in the background of the out of print RPG Space:1889 by Game Designers Workshop.  I use the miniatures from Sky Galleons of Mars, a related game.  There are only a few different types of miniatures provided with the game, but they are plastic so conversions are easy.

BACKGROUND HISTORY

In 1870, Thomas Edison crash lands on Mars in an ether flyer of his own invention.  He discovers the existence of an ancient and exotic Martian civilization.  When he returns, the Earth is electrified by his discovery.  Soon, dozens of companies are building Edison Flyers and trips to Mars become more frequent.  The race for colonization has begun.

Nineteen years later, the Belgians and British have established major colonies on Mars and several other countries have created smaller outposts.  However, not all of the Martians tolerate their new neighbors.  Cloudships and screw galleys, kept aloft by liftwood, strike at the colonial invaders.  Steam-powered aerial gunboats defend the colonies against attacks by the Martians, marauding pirates and forces from other human powers as well.

RULES CHANGES AND ADDITIONS

Of all the backgrounds I use Full Thrust for, Full Steam:1889 presents the most radical departure from the original rules.  Since battles are fought in atmosphere over the planet Mars, the addition of altitude has been added to movement.  This allows for some interesting weapons including dropping ordinance on a ship below.

Movement
Fighting in atmosphere results in the following rules changes.  Maximum speed is limited to 16 for aerial gunboats and 14 for Martian cloudships.  Gunboats may use half of thrust for maneuvering and cloudships may use all thrust for maneuvering.  Only half of current velocity, rounding up, is carried over from one turn to the next.

Altitude
There are five altitude levels: VL (Very Low), L (Low), M (Medium), H (High), VH (Very High).  It costs 1 thrust to move up or down a level.  Either UP (to increase altitude) or DN (to decrease altitude) should be written in the orders section to indicate the altitude change.  Ships may make only 1 height change per turn.  Current height level should be marked on the board.  You are free to use anything you like such as counters or stacks of chits.  More inventive gamers may want to mount miniatures on vertical poles or slides to create a true 3-D environment.

Systems
All ships receive damage control parties as per the More Thrust rules.  Armor is available on aerial gunboats only.  Firecons are not used since each weapon will have its own gun crew.  No other systems are available.

Some weapons may attack ships that cross each others path (see below).  For this purpose, string may be used to trace the movement path of ships  Changes in altitude occur at the midpoint of each ship's movement.  All 'path' based attacks occur where the ships' paths cross.

Weapons
Unless otherwise specified, weapons have targeting limitations based on the distance to target, as follows:
  0-12"  Can fire at targets on the same altitude level
12-24"  Can fire at targets up to 1 level lower or higher in altitude
24-36"  Can fire at targets up to 2 levels lower or higher in altitude

Following are the only weapons that may be used in this game.  An H (Human) and/or an M (Martian) in parentheses will indicate which races can use that weapon.  Rear arc weapons are allowed.

Breach Loading Cannon Battery (H)
  Use beam weapon battery rules
  May use multiple arcs (i.e., turrets)

Muzzle Loading Cannon Battery (HM)
  Use railgun rules
  Broadside mounted (side only, single arc only)

Martian Lob Gun (M)
  Fires a very large, heavy boulder in a high-trajectory
  Use AA-mega battery rules
  360 degree fire arc
  May not fire at targets closer than 6"
  Beyond 6", may fire at targets within 2 altitude levels higher or lower
  Only 1 may be mounted on a ship (capital class only)

Smutts Discharger (H)
  Fires a Smutts Aerial Torpedo with liftwood vanes for neutral buoyancy
  Use pulse torpedo rules
  May only be fired at a target at the same altitude or 1 level lower
  Forward arc only

Hale Rocket Battery (H)
  Brass tubes filled with solid propellant, fired as a salvo
  Use submunition pack rules

Tether Mines (M)
  Explosive charges equipped with contact detonators, attached to liftwood buoys
  TM must be written in orders when tether mines are raised, LM to lower
  Only 1 tether mine may be raised at a time, once it hits a target, it is destroyed
  Ships that have deployed tether mines may not move at a velocity faster than 8
  May only attack targets at 1 altitude level higher and have crossed attacker's path
  Will hit any enemy ship whose path it crosses on a D6 roll of 5+, damage is 1D6
  -1 to hit if target 3 or more velocity faster, +1 to hit if 3 or more velocity slower
  For 3 mines - Mass: 2  Points Cost: 5

Drogue Torpedoes (HM)
  Explosive charges equipped with contact detonators, dangled below the ship
  DT must be written in orders when tether mines are raised, LT to lower
  Only 1 tether mine may be raised at a time, once it hits a target, it is destroyed
  Ships that have deployed tether mines may not move at a velocity faster than 8
  May only attack targets at 1 altitude level lower and have crossed attacker's path
  Will hit any enemy ship whose path it crosses on a D6 roll of 5+, damage is 1D6
  -1 to hit if target 3 or more velocity faster, +1 to hit if 3 or more velocity slower
  For 3 mines - Mass: 2  Points Cost: 5

Martian Liquid Fire (M)
  Burning oil poured on targets below the attacking vessel
  May attack targets at 1-2 altitude levels lower and have crossed attacker's path
  Will hit any enemy ship whose path it crosses on a D6 roll of 5+
  -1 to hit if target 3 or more velocity faster, +1 to hit if 3 or more velocity slower
  Damage:  1 Hull Damage, Kills 1D6 Crew Factors

Spike Dropper (HM)
  Heavy, razor sharp spikes dropped on targets below the attacking vessel
  May attack targets at 1-2 altitude levels lower and have crossed attacker's path
  Will hit any enemy ship whose path it crosses on a D6 roll of 5+
  -1 to hit if target 3 or more velocity faster, +1 to hit if 3 or more velocity slower
  Damage:  2 Hull Damage, Kills 1D6-2 Crew Factors

Power Grapnel (M)
  Adds +2 to the chance to grapple

Crew
All ships have a number of crew equal to their current damage points divided by 2 minus crew lost in failed boarding attempts and from special weapons (see above).  A ship will always have at least 1 crew factor.

Boarding Actions
Only ships within 6" may be boarded.  To board, an attacking ship must first use grapnels to grab its target.  Roll 1d6 with the following modifiers: +1 if target's course is within 2 points and +1 if target's velocity is within 2.  An enemy will be grappled on a roll of 6+ and the smaller ship will be pulled into contact with the larger ship.  The attacker may choose to board with less than his full number of crew factors.  The boarding action proceeds as per the normal rules.  After each round of combat, either side may attempt to cut grapnels, ending the boarding action.  Grapnels may be cut on a D6 roll of 6+ with the following modifiers:  +1 if the last roll was just won, -1 if the last roll was just lost and -1 if a power grapnel was used.  If a boarding action fails, the defender may now choose to retaliate and board the attacking ship.  After the second boarding attempt is resolved, the boarding action ends and the ships are cut free.