Aerospace Engineering Sandbox becomes free on 2 November at 18:00 UTC. Until then it is a paid game. From that day on, anyone can download it and play it for free.

Update 1.3 comes out at the same time, with five new DLC packs.

Short-range, long-range and hypersonic missiles, the Bomb and Big Bomb, TNT, the Minigun and Flares, all unlocked right away, plus a free Strike Fighter in Prebuilt Planes.

https://store.steampowered.com/app/5448220/

The Nuclear Core, Nuclear Generator, Nuclear Jet Engine and Nuclear Rocket Engine: unlimited power and no fuel. The pack gives only one Nuclear Bomb, with a blast the size of a country. More bombs can be bought later.

https://store.steampowered.com/app/5448240/

Two fighter jets on call that fly at your wingtips and fight for you, and a refuelling tanker whose autopilot flies you onto its boom and fills your tanks in the air.

https://store.steampowered.com/app/5448250/

Twelve new worlds and the Ringed Giant, six bosses to beat, and the Rocket Engine and Compressed Air right away. Land at a world's base once to start there any time. This pack is not available in multiplayer mode.

Every part and every prize in the game right away, every base on every world to start at, and the Weapons, Nuclear, Royal Escort and Planets packs, for less than the four bought separately. Only one Nuclear Bomb (more can be bought later), and the Planets Pack is not in multiplayer mode.

https://store.steampowered.com/app/5448260/