Twostrokes
The scorched iron world closest to the star, the game's Mercury: bare rock, no air, and a day two weeks long.
The numbers
These are the figures the map's card shows when you hold your finger on Twostrokes, plus the two speeds that decide what a flight there costs. Low orbit speed is how fast you must be going, sideways, to stay up just above the surface. Escape speed is how fast you must be going to leave altogether. Sphere of influence is how far Twostrokes's pull reaches before something bigger takes over.
| Figure | Value |
|---|---|
| TYPE | Planet |
| ORBITS | Sun |
| DISTANCE FROM SUN | 5.26 Gm |
| ORBIT PERIOD | 25d 16:16:43 |
| ORBIT SHAPE | slightly oval (eccentricity 0.206) |
| RADIUS | 229.8 km |
| GRAVITY | 3.70 m/s² |
| DAY | 14d 15:54:00 |
| STATIONARY ORBIT | none — it spins too slowly |
| LOW ORBIT SPEED | 903 m/s |
| ESCAPE SPEED | 1,304 m/s |
| SPHERE OF INFLUENCE | 10.24 Mm |
| ATMOSPHERE | NONE |
Stationary orbit is the height where one trip round takes exactly one of the world’s days, so a ship there hangs over the same spot on the ground. See Stationary orbits.
What it is made of
What the world is built from. It is not something a ship measures, but it is why the ground looks and behaves as it does — an ice moon takes an impact differently from an iron one.
| Material | Share |
|---|---|
| Iron core | 70 % |
| Silicate rock | 30 % |
The air
None. Twostrokes has no atmosphere whatsoever, and that decides most of what a flight here is like. There is nothing for a parachute to catch, so the whole descent is flown on the engine and the last metres are taken on the landing legs. There is nothing to heat a hull on the way in, so a heat shield is dead weight. And there is nothing to slow a ship on the way up, so the climb off the surface is as cheap as the gravity allows.
It also means there are no air bands to survey: leave the ground and you are straight into low space. See Science and readings for what that is worth.
The ground
More iron than rock, and the ground shows it. The band across the terminator is the roughest, throwing up ridges over a kilometre and a half from the mean; the slag basins on the other side sit 300 m below the datum.
| Biome | Where | Typical height | Roughness |
|---|---|---|---|
| Sunward Flats | −180° to −108° | 120 m | ± 400 m |
| Slag Basins | −108° to −36° | −300 m | ± 700 m |
| Terminator Ridges | −36° to 36° | 400 m | ± 1,532 m |
| Nightside Frost | 36° to 108° | 150 m | ± 500 m |
| Iron Plains | 108° to 180° | 0 m | ± 300 m |
Where is the band's place round the world, in degrees from the world's own 0°, running out to ±180° on the far side. Typical height is where that biome's ground sits against the datum the map measures altitude from, and roughness is how far it wanders either side of that.
On the map Twostrokes is drawn from a painted picture, and every band on it is named for where the sun puts it. The Sunward Flats are pale baked rock; the Slag Basins beside them are the darkest and lowest ground, pooled where the surface has run. Facing 0° the Terminator Ridges stand 400 m up and are far the roughest thing here, wandering 1,532 m either way — the ground to avoid on the way down. Round the far side the Nightside Frost is the one pale band that is not baked, and the Iron Plains complete the circle at the datum. The colour under you as you come down is the colour of that band.
Named landforms
Twostrokes's ground is drawn from a table of named features rather than noise alone, as every world you can stand on is. Where you come to rest is recorded by name, which is why some achievements ask for a summit, a crater floor or a plateau rather than just a landing. All 8 of them are below, in order round the world, from the far side back to 0° and on round.
| Landform | Kind | Where | Height | Flat ground |
|---|---|---|---|---|
| Caloris Floor | Plateau | −150° | 300 m | 30,000 m |
| Caloris Rim | Mountain range | −124° | 2,600 m | 60 m |
| Slag Basin | Crater | −95° | 1,800 m | 12,000 m |
| Rembrandt Scarp | Escarpment | −60° | 1,200 m | 8,000 m |
| Terminator Wall | Mountain range | −18° | 3,600 m | 55 m |
| Discovery Rupes | Escarpment | 12° | 1,500 m | 6,000 m |
| Frost Hollows | Crater | 60° | 1,400 m | 5,000 m |
| Iron Plain | Plateau | 140° | 200 m | 40,000 m |
Where is the landform's place round the world, and height is how far it stands above (or below) the ground around it. Flat ground is the level run it promises — the width of the ledge, floor or summit a ship can set down on.
Getting there
No air, so every metre of the descent is paid for on the engine, and a day two weeks long: a landing site stands in full sun or in full dark for a very long time, which decides everything for a ship running on solar panels. Reaching its sphere of influence pays Two Strokes Off Your Game.
Twostrokes has no line of its own on the Δv ladder. The nearest figure is its own planet's orbit. Getting down from there and back up again costs about its escape speed — 1,304 m/s — each way on top of that, less whatever you can save by coming in shallow.
What it pays
Every place nobody has measured before pays discovery the first time an instrument reads it, and how much depends on how far from home the world is. Twostrokes counts as 3.61 against Earth's 1.00, so every place on it pays that many times what the same place at home would.
| Figure | Value |
|---|---|
| PLACES TO SURVEY | 14 |
| WORTH IN ALL | 56 discovery |
| CREDITS BESIDE IT | 1,120 |
A place is a world, a band of altitude and — on the ground — the biome you are standing in, and each instrument surveys each place separately. Science and readings explains the whole of it.
What it pays out for
One achievement names Twostrokes: Two Strokes Off Your Game.
The full list, with what each one pays, is on the Achievements reference.