Reference velocities in space in BECMI
by LoZompatoreAs per Immortal Box (DM's Manual page 3) the "The fourth dimension defines the relation between two objects, finding all points of similarity, or convergence", thus enabling instantaneous travelling between two points of space in the same Plane of Existence, as per the Teleport spell.
The Immortal Box also states (Player's Manual page 10) that the error in the use of teleportation by mortal beings is due to the fact that mortals are three-dimensional beings, so they cannot see through the 4th dimension while teleporting. The Immortals, being fourth-dimensional beings instead, can see through the 4th dimension while teleporting, so they can instantly move without error between two points of space.
I guess this is the same difference as being shot from a cannon to a destination laying beyond the horizon (a very imprecise and risky business) and being able to take a plane to reach the same destination.
Said so, some food for thought about movement in space, from Immortal Set, Champions of Mystara Designer's Manual and M4 Module final section:
Immortal Set, Page 10 Player's Guide:
The maximum Universal rate for an incorporeal Immortal is 24 miles (the width of a standard large-scale campaign map hex) in one round, or 8,640 miles per hour. This amazing speed results from the character's relative freedom from the limits of matter and time while in this form. When incorporeal, a character may pass freely through material objects and magical effects.
Immortal Set, Page 7 DM's Guide:
A teleport or dimension door effect opens a pathway across the fourth dimension, allowing the user to bypass the first three dimensions and apparently cross any amount of space in very little time
M4 page 35:
Travelling from Earth to the Sun in any practical time requires either special equipment or a well-cast Teleport spell (a Wish can be used with this spell to affect an entire group of characters). PCs can only Teleport to the surface of the Sun, though; trying to reach the interior counts as teleporting into a solid object.
Other spells, such as Travel, transport the caster very slowly. If the PCs have no way to Teleport, the DM may opt to increase movement rates for such spells outside the Earth’s atmosphere by a factor of a million. Even then, the party may need days or weeks to cross the 93 million miles of vacuum to the Sun.
Once at the Sun’s surface, the characters have another 450,000 miles to go to reach the core (and teleport spells won’t work now). To keep the adventure moving, assume Travel or a Wish can transport the party as far as 100,000 miles a day. The increase in speed can be explained by the vast magical and physical energies which the Sun generates.
Champions of Mystara Designer's Manual page 33:
Speeds in space are significantly greater than those possible within gravitational fields and atmospheres - they have to be to allow Voidships to cover the vast distances between worlds. A Voidship's speed varies with the proximity of large gravitational bodies. The farther away such bodies are, the faster the ship can travel. There is no actual limit to a ship's speed in the Void.
Travelling to a planet to one of its moons should take about two weeks for a Voidship powered with a Fly spell or equivalent magic.
...
Travelling to another planet within a solar system should take a month or more.
Travelling to another solar system may take two or three months. Although solar systems are much farther away from one another than are planets within a system, Voidships can reach incredible speeds in the gravity-free space between systems. The actual travel time is up to the DM, and should be wathever is necessary to facilitate the pace and plot of the adventure.
...
Impulse Speed: Voidships near gravitational bodies drop to roughly 10x their Air Speed - call this "impulse speed" if you like. This change in speed is automatic, instantaneous, and unhampered by inertia and other physical laws. It allows for encounters in the Void, and avoid the need for complicated formulas and calculations dealing with velocity, acceleration and deceleration.
Encounter distance - the point at which a Voidship's movement drops to impulse speed - is 10x the radius of ship's own gravitational field.
Summarizing, some reference velocities in space in BECMI are as follows:
1) Draeden speed in space (Immortal Set): 6 miles / round
2) Flying Saucer speed (IM1 module): 8 miles/ round
3) Travel Spell in space (M4 module): approx. 12 miles / round
4) Incorporeal Immortal Speed (Immortal Set): 24 miles / round
5) DM's option of M4: Travel speed in space of 120 feet / round is increased by a 1,000,000 factor: 22727 miles / round. This means 1 AU in 4092 rounds i.e. 40920 seconds = 11.3 hours. It could be rounded down in 1 AU in 12 hours, meaning that 1 light-year (63241 AU) can be crossed in 31620 days, or 86.6 years.
6) Champions of Mystara: faster than light travelling is possible between star systems, with speeds at least 10 times the speed of light. With respect to M4 option of point 5) this is a further increment of speed by a factor of 1000. As no upper speed limit is set, higher speeds can be reached in regions of intersellar space farther away from significant gravitational fields.
Possibly, to harmonize M4 module and Champions of Mystara figures, the following maximum speeds in space can be set:
Assuming Champions of Mystara figures, an average Air speed of 240 miles / day (120 yards / round) can be considered.
- Void just above a planetary body Skyshield: Impulse Speed (10x the Air Speed of the ship): 2400 miles / day
- High planet orbit and up to the planet moons: 100x Air Speed: 24000 miles / day
- Space between inner planets of a star system: 10,000x Air Speed: 2,400,000 miles /day
- Space between outer planets of a star system: 100,000x Air Speed: 24,000,000 miles / day (approx. 1/4 of the speed suggested in M4 module)
- Outskirts of a star system (cometary clouds, etc.): 10,000,000x Air Speed: 2,400,000,000 miles /day
- Interstellar space, crowded with stars: 1,000,000,000x Air Speed: 240,000,000,000 miles /day (approx 10 times the speed of light)
- Interstellar space, with sparse stars: 100-1000 times the speed of light