The rocket in SteamWorld Build is presented as a scavenger hunt. It is not.
There are six old-tech rocket parts, exactly two per mine layer, and digging them out takes six Miners and about two minutes each. That is not a challenge. It is a chore you do six times.
The actual gate is the thing the part hunt distracts you from: you cannot finish the parts until you have 240 Scientists at Milestone 19, and you cannot launch until you have produced 100 units of rocket fuel — which is manufactured from the same farm slots that make your Plastics.
That is the endgame. It is a population problem wearing a mining costume.
The six parts, and why the last two feel impossible
| What gates it | Why it blocks a part |
|---|---|
| Bridges — 200 Engineers | Parts sit across chasms your Miners cannot cross. No bridge, no part |
| Layer doors | Each layer’s parts are behind doors that only open as you break through the layer |
| Milestone 19 — 240 Scientists | The deepest parts and the Jetshroom Farm both arrive here |
| Bridges and shafts | Hidden sections behind them hold the parts that “don’t exist” on your map |
The two-part-per-layer rule is consistent across guides, and so is the warning that positions vary by run and by map randomisation. If you have turned mine randomisation on, any walkthrough telling you a specific tile is wrong for your save.
So the search method matters more than a map:
- Fully clear a layer before descending — do not leave rubble pockets.
- Repair every Abandoned Mineshaft you unlock; the ones in the Marshy Ruins need at least 10 Scientists in the city.
- Bridge every chasm as soon as Bridges unlock at 200 Engineers.
- Put Guard Quarters and turrets around the part sites before you start digging. Excavating a part activates the hives in the area, and the attack is timed to your dig, not to your readiness.
And the mechanical detail that wastes the most time: extraction needs six Miners and takes minutes, and any other click reassigns them. Players start a dig, then go fix a production line, then come back to find the part half-excavated and the Miners elsewhere. Start the dig, then leave the mine alone.
The Astrodome
Collecting your first part reveals the Astrodome, usually a short distance from your main settlement. Each part is sent there automatically and shows as installed. You also get the Going Places achievement on the first one.
The Astrodome is also your launch button — and, importantly, the rocket needs Warehouse access to receive fuel. If the Astrodome sits outside your road network, the fuel cannot be delivered and the launch never becomes available. That is a layout mistake made hours earlier that only surfaces at the end.
The fuel is where the run actually ends
100 units of Rocket Fuel. Made in the Rocket Fuel Processing Plant at Milestone 19, from Gas plus Jetshrooms.
Three things about that:
1. Jetshrooms replace Plastishrooms. Both are farm slots in the mine. The endgame expects you to convert some Plastishroom farms to Jetshroom farms, and Plastics feed Aristobot buildings and Maglev Roads. So the moment you start fuelling the rocket, your highest-tier building material starts draining. Plan the conversion for after your town is finished, not during.
2. Gas needs its own extractor. The Gas Extractor unlocks at Milestone 13, well before the plant. If you never built one because you were not using Gas, the plant will sit idle at Milestone 19 while you build an extractor, connect it and staff it.
3. Fuel production is time, not skill. It runs like any other product. Production Chance and Production Speed items on the plant are the only lever — collected from the train store, which restocks every 4:45. Bank a few before Milestone 19 rather than after.
The real checklist
Most players finish the parts and then stall for an hour. The order that avoids it:
- Work the population cascade early. Scientists are the fourth tier: Workers → Engineers → Aristobots → Scientists, each requiring 100% satisfaction on the tier below before the upgrade is even offered. A housing shortage at Milestone 5 is what stops you at Milestone 19.
- Build the Gas Extractor when it unlocks at 13, not when you need it.
- Save Production Speed and Production Chance items for the fuel plant.
- Do not convert Plastishroom farms until the town is done. Plastics first, fuel second.
- Clear each layer completely before descending, and bridge everything.
- Start each part dig when you can leave the mine alone for two minutes.
- Check the Astrodome has Warehouse access before you start making fuel, not after.
If you are stuck at “5 of 6”
Nine times out of ten the sixth part is behind a bridge you did not build, in a pocket you wrote off as rubble, or behind an abandoned mineshaft you never repaired. In roughly that order.
The tenth time, it is on a layer you have already “finished” — the two-per-layer rule means a cleared layer with one part collected is not cleared.
Related guides
- SteamWorld Build milestones — the full 19-level unlock table this depends on
- SteamWorld Build guide — roads, coverage and the town-and-mine loop
- SteamWorld Build tools — the workforce bottleneck behind the population cascade
- SteamWorld Build glassware — the Engineer supply chain that feeds the tiers above
- SteamWorld Build worms — what actually comes out when you dig a part
- SteamWorld Build money — funding the Scientist upgrade wave