The goal
You fly a small orbital tug. Each contract asks for an orbit with a target periapsis (PE, the low point) and apoapsis (AP, the high point). Match both within the displayed tolerance and coast without thrust for three seconds. The satellite deploys automatically, your fuel is replenished, and the next contract arrives.
Your first transfer
- Choose Prograde and hold the burn button. This accelerates in the direction you are already travelling. Watch AP rise towards the target. Release the button as it enters the tolerance band.
- Coast to apoapsis, the highest part of your orbit. The flight computer gives a countdown. Use 3x or 10x while coasting, then return to 1x as you approach.
- Burn Prograde again near apoapsis. This lifts the low side, PE, towards the target. Short 20 m/s pulses or a lower throttle help you finish accurately.
- When both readings match, release thrust and hold steady for three seconds.
Four thrust directions
Prograde adds orbital speed. Retrograde reduces it. For a lower orbit, burn retrograde near the high point to lower PE, then near the low point to lower AP. Radial in/out point towards/away from Earth and reshape the orbit; they are useful for corrections but less efficient for a simple circular transfer.
A burn changes the whole orbit, not just your current altitude. Watch the blue predicted orbit against the lime target. Elliptical contracts accept any orientation; only the low and high altitudes matter.
Fuel, time and recovery
Your propellant budget is shown as remaining velocity change in metres per second. Efficient transfers earn a higher score. Deployment supplies another 1,500 m/s, up to a 3,600 m/s capacity. Thrust always returns time warp to 1x. A burn stops on pointer release, focus loss, pause or tab change.
Entering the atmosphere, escaping beyond the display's recovery region, or exhausting propellant outside the target orbit ends the run. Sandbox gives unlimited fuel and restores a safe orbit after a crash; it does not award score or points.
Modes, controls and records
Endless generates new contracts for as long as you survive. The daily shift is a shared sequence lasting five minutes of unpaused play, independent of coast speed. Deploy three satellites in an endless run for 20 DEXM points, up to three qualifying runs per UTC day. Finish the daily shift with at least three deployments for 100 points once that day.
Hold W for prograde, S for retrograde, A for radial in and D for radial out. Or select a direction and hold the burn button with a mouse, touch, Space or Enter. P pauses. Your run pauses on focus loss; best scores and settings are stored locally, but live runs are not saved.
The model
This is a two-dimensional two-body gravity simulation, with deliberately accelerated time and simplified propulsion. It omits atmospheric drag above the loss boundary, orbital inclination, other bodies, debris and many real-world effects. It is a game, not a navigation or mission-planning tool. Earth imagery is adapted from the NASA Blue Marble texture already used by Skywave. NASA does not endorse this game.