Mass Fraction

In 2188 a nine-day war in low orbit destroyed most of Earth's satellites. Their fragments still circle the planet. This shell of debris is called the Lid, and every launch has to cross it.

It is 2509. You run the Office of Second Ascent, with one launch pad on the Guiana coast, a few dozen staff, and a budget that depends on results. Research shielding, build modules, choose launch windows, train crews, and assemble a station above the Lid. Then send a ship to geostationary orbit to restore a weather satellite.

The Harrow are self-replicating machines, sent to the asteroid belt in 2161 to build homes for settlers. They dismantle anything missing from their registry. The registry was last updated on 18 March 2188, so everything you put above 20,000 km counts as debris.

What you do

• Plan burns with the rocket equation. Each plan shows delta-v, propellant and mass fraction.
• Launch through the Lid. Each crossing shows its risk. Tracking, shielding and better launch windows lower it.
• Train named crew. Everyone has a radiation dose record, and the dead are listed on the Roll.
• Expand from Earth. Build Tare station between the radiation belts, then a depot at L1. Mine ice and make propellant on the Moon. Then go on to Mars and beyond.
• Keep the Harrow's attention low. Recover pieces of the registry's root key, and find a way to give the machines orders.

The campaign

There are four acts: The Lid, The Gap, The Dead and The Harrowed. The story ends with the Broadcast, which has two possible endings. After that you can keep playing in Continuance Mode.

The Continuance is what remains of Earth's governments, and it funds the Office. You lose if:

• the Continuance loses confidence in the Office and closes it;
• Earth's capacity runs out and the Continuance breaks apart;
• the Office has no working launch pad and no crew above the Lid for 180 days.

Orders in the LEDGER always show the next goal. The first time something new comes up, a member of staff explains it.

Presentation

640×512 pixels in sixteen colours. Each location has its own ambient sound. Four original pieces play on the title, at the launch site, on the act cards and when the Harrow move against the Office. Flight control announces launches, losses and arrivals.

Web demo

A free web demo lets you play Act I in the browser. It ends when Act II begins or at the end of 2512, whichever comes first.

Controls

• Everything can be done with the mouse.
• F1–F10 open the ten screens.
• Space pauses. 1, 2 and 3 set the speed.
• Esc or right-click goes back.
• Ctrl+S saves. Ctrl+L loads.
• F11 toggles fullscreen.