What Is Spacium's Open Port? The $1 Refueling Standard
Spacium's Open Port is an open spacecraft refueling interface licensed for $1. How it works, the 2027 xenon test at the ISS, and why it matters.
What is Spacium's Open Port?
Open Port is a refueling connector for spacecraft, designed by the Y Combinator startup Spacium and released as an open standard. It lets one spacecraft pass fuel to another in orbit, and the same port can also be used to fill a spacecraft with fuel on the ground before launch. Spacium shares the technical drawings and part of the software. Any space company can buy a license for $1 and build the port itself.
TL;DR
- Open Port is a refueling interface, not a whole spacecraft. It is the connector two spacecraft use to transfer fuel.
- The license costs $1, and the buyer gets technical drawings and part of the software to manufacture the port in house.
- The design targets three hard problems: high operating pressure, tolerance for misalignment between spacecraft, and an androgynous design where both sides are identical.
- Its first in-orbit test is planned for Q2 2027, docked outside the International Space Station (ISS), with a xenon transfer.
- Spacium sells fuel as a service, so a widely adopted port helps its core business instead of competing with it.
- A refueling station mission is booked for mid 2028, according to the founders.
Why does spacecraft refueling need a standard?
Today most spacecraft launch carrying every drop of fuel they will ever use. Spacium's founders describe the cost of that: a spacecraft can't go as far, can't carry as much payload, and gets discarded when the fuel runs out, even if the hardware still works. These spacecraft can cost hundreds of millions of dollars and take a long time to build, so replacing one is slow as well as expensive.
The comparison the founders use is a car. Nobody scraps a car after driving between two cities because the tank is empty. Refueling in orbit would work like a service station, which is how Spacium describes its plan: a network of automated refueling stations where a spacecraft docks, refuels, and leaves with no humans involved.
The missing piece is a common connection. Every spacecraft has a valve for loading fuel on Earth, but that valve is useless once the spacecraft is in orbit. There is no agreed way to transfer fuel in space, and without one, a refueling station has nothing reliable to connect to. Think of USB-C on phones: the charger is only useful because everyone agreed on the plug.
How does Open Port work?
The transfer happens in three stages:
- First contact. The two spacecraft meet through a probe and drogue. A probe is a protruding part that slides into a funnel-shaped receiver (the drogue). This is a long-established way to join two vehicles.
- Hard lock. Once the spacecraft are together, locking features hold them rigidly.
- Fuel transfer. Fuel moves through the valves in the port.
Spacium says three design choices set Open Port apart:
| Feature | What it means | Why it matters |
|---|---|---|
| High pressure range | The port is designed to operate at higher pressures | Customers told Spacium that some of the fuels they use work best at high pressure |
| Misalignment tolerance | The seal can make a connection even when two spacecraft are poorly lined up | Perfect alignment in orbit is hard, so the port has to forgive errors |
| Androgynous design | Both sides of the connection are identical | One spacecraft can both give and receive fuel |
The androgynous design matters more than it sounds. Some customers want to buy fuel from Spacium's station and then move it between spacecraft in their own fleet. With identical ports on every vehicle, any spacecraft can play either role. A conventional connector with a "male" and "female" side would force you to choose.
Why does Spacium license it for $1?
The founders say Spacium's core business is selling fuel as a service, not selling refueling interfaces. They kept running into the same bottleneck: no standardized interface existed to transfer fuel to customers. So they built one and decided to make it an open standard.
The founders say existing refueling interfaces are expensive, around $30,000 for one side of the connection, and that nobody wants to pay $30,000 to $50,000 for an interface that has never been tested in space. A $1 license removes the price objection.
On why $1 and not free, the founders said the number came up during YC office hours. They want customers to go through Spacium to get the license. A nominal fee keeps a direct relationship without making cost a barrier.
There are two routes to the hardware:
- Small fleets can get the port from Spacium. According to the founders, the port comes free when a customer buys fuel from them.
- Large fleets can buy the license, take the drawings and software, and have their own manufacturers build ports whenever they need them.
Asked what happens if a competing refueling company adopts Open Port, the founders called it a win. More refueling activity grows the market they sell into.
Why would anyone trust a port that has not flown yet?
This is the real obstacle for any new spacecraft part. The founders point out that no one wants to put something on a spacecraft that has not already been to space and been tested. That is why a standard needs flight history before it spreads.
Spacium's answer is a staged plan. Each mission adds risk on purpose, so the team can remove it step by step.
| Mission | What happens | Timing (per the founders) |
|---|---|---|
| First | Flew robotic actuators and tested avionics, actuator movement and thermal systems | Flew the previous November |
| Second | Open Port docks outside the ISS and transfers xenon in orbit | Q2 2027 |
| Third | First full refueling station, refueling a customer who has already bought the mission | Mid 2028, launch booked and confirmed |
Some details from the first mission: the founders say the actuators for their in-house robotic arm became the most accurate robotic actuators ever flown in space, and that they expect to beat that record on the second mission. They also said preparation for the first mission was rough, with test after test failing, even though the mission itself succeeded. Lessons from that carried into the second mission, and an engineering model taken to Houston for a fit check with the ISS went better than expected.
The xenon transfer would be a first. The founders say no one has transferred xenon in orbit before. If it works, other companies get a port with flight history and a record of moving fuel in orbit.
Why xenon, and what about cryogenic fuels?
Spacium started with cryogenic fuel architecture, meaning very cold propellants like liquid oxygen and liquid hydrogen. After two years of customer conversations, the founders found that early customers wanted xenon, so they began there. The initial customers are orbital transfer vehicles, which carry payloads between orbits and deploy satellites. Moon mission customers are mostly interested in cryogenic fuels, and Spacium is still working on those.
Cryogenic fuels have a known problem called boil off. If they are not kept cold enough, the fuel evaporates and has to be vented. The founders say they developed a way to store cryogenic fuel without loss during their YC batch. I have no independent data on that claim, so treat it as the company's statement. They also say Open Port works with multiple fuel types. Spacium says its stations can store anywhere from 2,500 kg to 30,000 kg of fuel.
What does this mean for you?
Most readers will never buy a spacecraft part, but the story has useful lessons.
If you work in aerospace, procurement or engineering: an open, low-cost interface changes the calculation for fleet planning. You can compare a $1 license plus in-house manufacturing against buying proprietary hardware. Before committing, ask about flight heritage. Open Port's main selling point is a test planned for 2027, so check whether that milestone has happened and how it went.
If you work in any industry with competing formats: the pattern is worth recognizing. A company gives away the part that holds the market back so it can sell the service that depends on it. Look for it in your own field when evaluating vendors. A free or near-free standard from a vendor usually has a business model attached, and here the founders state theirs openly: selling fuel.
If you are following startups: the plan is a clear sequence of milestones with dates. Those dates are targets from the founders, not guarantees. Space schedules slip, so watch for the actual ISS test result.
Could you build your own tracker for a standards-driven project?
Teams evaluating something like an open interface end up juggling a spreadsheet of vendors, license status, test milestones and open questions. You could describe that tracker to Remy, which builds and deploys full-stack business apps from a plain-English description. It could hold a vendor comparison, a license and approval checklist, a milestone timeline with owners, and a request form for engineers to submit questions. Because the app is yours to run, you don't need another subscription for something this specific. Remy has a 7-day free trial, and the flat platform fee covers unlimited projects.
Frequently Asked Questions
What is Spacium?
Spacium is a Y Combinator startup. It builds automated in-orbit refueling stations where a spacecraft docks, refuels and leaves without humans in the loop. Its business is selling fuel as a service.
Is Open Port really open source?
Spacium says it is sharing the technical drawings and part of the software, and any company can license the design for $1 and build it. It is described as an open standard, but the license is still obtained through Spacium, so read the terms before assuming it works like a typical open source project.
When will Open Port be tested in space?
The founders say the second Spacium mission, planned for Q2 2027, will dock Open Port outside the ISS and transfer xenon in orbit. They describe this as the first xenon transfer in orbit. Launch dates can change, so check for updates.
Who needs in-orbit refueling first?
Spacium's initial customers are orbital transfer vehicles, which move payloads and deploy satellites. It also reports interest from moon missions, launch vehicles and geostationary satellites.
Why does Open Port need to be androgynous?
Because both sides of the connection are identical, any spacecraft can give or receive fuel. That lets a customer buy fuel from a station and then pass it between spacecraft in their own fleet.
How we source, write, and correct our articles. Editorial standards
Related articles
Why Did Jensen Huang Resign as Nvidia CEO? What We Know
Fable 5.2 vs Opus 5.5: Which Claude Model Should You Use?
How Much Should You Spend on AI? Hormozi's Budget Lesson
