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Sidera Caeli
A first-person multiplayer space sim with no loading screens: gear up at the station, walk to your ship, power it up and take off. Fly in six degrees of freedom, jump between worlds, land and explore on foot or by rover, and take contracts with your squad in a persistent shared universe.

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Features
Languages:
Interface Full Audio Subtitles
English ✔ ✔ ✔
Spanish - Spain ✔ ✔ ✔

Coming Soon To Early Access

The developers of this game intend to release as a work in progress, developing with the feedback of players.

Note: Games in Early Access are not complete and may or may not change further. If you are not excited to play this game in its current state, then you should wait to see if the game progresses further in development. Learn more

What the developers have to say:

Why Early Access?

“Sidera Caeli is a persistent multiplayer universe. Its systems (flight, combat, economy, missions) need real players and real load to be tuned properly. Early Access lets the community shape the game while it grows.”

Approximately how long will this game be in Early Access?

“While most of the core systems are already in place, there is still a long road of content and stability work ahead before Sidera Caeli can be called a complete game. It is currently developed by a solo developer (with AI help), so we expect to leave Early Access roughly by December 2027.”

How is the full version planned to differ from the Early Access version?

“Fuel and refuelling, component swapping and ship customisation, a player-driven economy, mining, refining and salvage, industry and service drones, base building, capital ships with internal hangars, and a social module (chat, friends, organisations).”

What is the current state of the Early Access version?

“Fully playable sortie loop: station, gear, contracts, boarding, six-axis flight, quantum travel, ATC and hangars, landing on planets with oceans, weather and fauna, rovers, crewed turrets, EVA, combat against NPCs, inventory, shops and loot, and squads of up to eight players.”

Will the game be priced differently during and after Early Access?

“Sidera Caeli will be free during Early Access, 1.0 launch, and after. There will be no subscription. Optional cosmetic items may be offered in the future, but nothing that affects gameplay.”

How are you planning on involving the Community in your development process?

“We gather feedback through the Steam forums and the official website, where the public roadmap is updated each time a system becomes playable. The community is welcome to help shape the game: proposing and helping design new components, ships, weapons, planets or anything else they can imagine. The Steam discussions are open for questions, feedback and ideas to help Sidera Caeli reach its full release.”
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This game is not yet available on Steam

Planned Release Date: 2027

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About This Game


You don't pick a mission from a menu. You gear up at the station, accept a contract, cross the hangar on foot and take the controls. From there, the whole system is yours: asteroid rings, planets with seas and clouds, vehicles to roam them and creatures that weren't expecting you.


From inside a hangar to orbit and down to a planet's surface without a single loading screen. Stations, ships, orbits and surfaces share the same world, in the same session, with the same players.


  • Gear up: helmet, suit, backpack and weapon. What you wear decides your oxygen, the temperatures you can take and how much you can carry.
  • Take a contract: escort, defend, investigate or haul, alone or with your squad.
  • Board and power up: walk-in ships with real ramps and doors.
  • Fly: six axes, thrust, inertia and heat. Coupled or decoupled.
  • Jump: plot the route, align the nose, calibrate and correct the drift by hand.
  • Land and explore: on foot, by rover or swimming. Each planet has its own weather, sea and fauna.
  • Fight and get paid: waves in space, on foot or from the air, loot and payout at the station.


Interactive cockpit screens, a volumetric spherical radar with up to 128 contacts, traffic control with hangar reservation, quantum travel with manual calibration, crewed turrets, EVA with magnetic boots and rovers with per-wheel suspension.


You approach planets, orbit them and land on them. Clouds, seas you can swim in, asteroid rings to thread with your radar and creatures native to each biome. Watch the dunes: something moves under the sand.


Modular suits by piece and tier, a backpack with real capacity, shop and trade terminals, cargo crates you move with a tractor beam and loot after every fight. Form squads of up to eight pilots: the work and the pay are shared. The server decides position, seats, contracts and inventory, so everyone sees the same thing.


Sidera Caeli is built with Martin Space Industries' own tools. Planets, sectors, maps, ships and missions are placed and tuned by hand.


Sidera Caeli is in open development. Each roadmap system joins the game once it works inside it.

AI Generated Content Disclosure

The developers describe how their game uses AI Generated Content like this:

Sidera Caeli is developed with the help of AI tools, always under human direction.

Code: A large part of the game’s code was written with AI assistance. All specifications, design decisions, code review and quality assurance are carried out and supervised by our human team (me). Nothing reaches the game without human review.

3D models: Some of the 3D models in the current build are AI-assisted placeholders. We used them to build and test the game’s systems early. Professional 3D artists are already creating final models, and we are also licensing third-party asset packs. Together these will progressively replace every AI placeholder with human-made art.

World building and procedural content: Map placement, system tuning and the parameters behind procedural generation (planets, terrain, scatter and points of interest) are authored by hand by our team, using our own in-house tools. None of this is generated by AI.

Mature Content Description

The developers describe the content like this:

Players fight human NPCs and creatures with firearms and ship weapons. Defeated characters leave bodies that can be looted. No blood or gore is depicted.

System Requirements

    Minimum:
    • Requires a 64-bit processor and operating system
    • OS: Windows 10 22H2 / Windows 11, 64-bit
    • Processor: Intel Core i5-8400 / AMD Ryzen 5 2600
    • Memory: 16 GB RAM
    • Graphics: NVIDIA GeForce GTX 1660 SUPER 6 GB / AMD Radeon RX 5600 XT 6 GB
    • DirectX: Version 12
    • Network: Broadband Internet connection
    • Storage: 10 GB available space
    • VR Support: Experimental OpenXR support. Headset compatibility and VR performance are still being tested
    • Additional Notes: Need more feedback on the lower specs floor
    Recommended:
    • Requires a 64-bit processor and operating system
    • OS: Windows 11, 64-bit
    • Processor: Intel Core i5-12400 / AMD Ryzen 5 5600
    • Memory: 16 GB RAM
    • Graphics: NVIDIA GeForce RTX 3060 12 GB / AMD Radeon RX 6600 XT 8 GB
    • DirectX: Version 12
    • Network: Broadband Internet connection
    • Storage: 10 GB available space
    • VR Support: Experimental OpenXR support. Headset compatibility and VR performance are still being tested