What is Orbital Refueling and how does it work?

Whenever a spacecraft ascends toward space, it burns out most of its fuel before crossing the karma line to reach orbit. This is where the concept of orbital refueling emerges to soften the huge gap.

Let’s say the spacecraft is flying to a distant planet like Mars, it will still need some amount of fuel to safely land on the surface of the planet. The reason why space agencies do not consider using the concept at the moment is because they are launching only smaller robotic spacecraft to distance planetary bodies like Mars.

As space agencies prepare to launch heavier payloads to Mars, the concept of orbital refueling will be deployed frequently in low Earth orbit. Aside from refueling spacecraft going to Mars, space agencies are also planning to refuel satellites moving around Earth. What is orbital refueling and how does it work? Continue reading to find out.

What is Orbital Refueling?

Orbital refueling is simply the process of refueling spacecraft in orbit. The orbital propellant depot will be launched into the orbit around Earth. Once the spacecraft that requires refueling services arrives in orbit, the orbital propellant depot will dock into the deep space spacecraft and commence with the fuel transfer stage.

Once the refueling is completed, the propellant depot will undock from the spacecraft, and probably return to Earth. The refueled spacecraft will proceed with its journey to the planned destination.

How Does Orbital Refueling Work?

The concept of orbital refueling works by the docking of two spacecraft to transfer fuel from the orbital propellant depot to the spacecraft that requires refueling. The space agency planning to accomplish orbital refueling will first launch the depot propellant spacecraft into orbit. The depot will carry enough fuel that enable the exploring spacecraft to accomplish its mission requirements.

Once the deep space spacecraft arrives in orbit, engineers will remotely control it to dock with the propellant depot and commence with the fuel transfer process. It is important to note that the type of fuel to be refueled matters a lot.

The location and size of the propellant depot are also important. Most space agencies will use propellant sizes that are bigger than the exploring spacecraft to have enough fuel to be supplied. Space agencies will target delivering orbital refueling on a single load to the exploring space probe.

The location of the orbital refueling will be targeted at the low Earth orbit, to enable the space agency safely recover the depot when it is empty. Aside from refueling rockets traveling beyond low Earth orbit, space agencies are also researching ways to refuel satellites in active operation in space.

Once the concept of orbital refueling becomes a reality, we should expect space agencies to prolong the lifespan of satellites operating in low Earth orbit.

How Space Agencies Are Attempting Orbital Refueling

Some government and private space agencies have attempted to test the concept of orbital refueling in space to see how it would benefit satellites in low Earth orbit and future deep space missions. Now, let’s discuss how space agencies are preparing to conduct orbital refueling in space.

Orbit Fab

Orbit Fab is an American Space company that provides orbital refueling services to different companies. The company renders its services by refueling satellites in space using its Rapidly Attachable Fluid Transfer Interface (RAFTI) refueling technology and its GRIP refueling capabilities.

So, how does Orbit Fab’s systems work? Firstly, the RAFTI docking port docks with the target satellite. The Grip, which is an automated refueling technology will enable the RAFTI to connect firmly with the target satellite before the refueling operation commences.

This implies that the port of RAFTI will be connected perfectly to the port of the refueling satellite through the assistance of the grip. Orbit Fab has succeeded in testing its RAFTI and GRIP system on Earth. Now, the company is getting ready to launch its sophisticated technology into Space in late 2025.

As of today, Orbit Fav has been awarded contracts by the Space Force and other agencies to conduct in-orbit refueling. The company hopes to conduct the Space Force’s Tetra-5 experiment in late 2025 after launching its orbital refueling technology.

Orbit Fab plans two experiments by docking three satellites separately with its refueling vehicle before transferring propellant to the three satellites going around Earth in geostationary orbit.

SpaceX

SpaceX is an American aerospace company that has provided multiple launch services to both governmental and private space agencies. The company, founded by Elon Musk in 2002, is working towards achieving orbital refueling for its deep space missions to Mars.

SpaceX has already revealed its plan to demonstrate starship-to-starship cryogenic transfer by next year. The aerospace company plans to achieve this demonstration by launching two starships. One of these spacecraft will serve as a target, while the other will serve as the refueling tanker.

The outcome of this mission will determine how other space agencies are also interested in orbital refueling. Once the practice becomes common, we should expect more space companies to invest heavily in the concept. This implies that before the 2030s, space agencies must have mastered the act of orbital refueling. Hence, they may deploy it even beyond low Earth orbit.

FAQs

How will SpaceX refuel in orbit?

SpaceX plans to achieve refuel in orbit by docking two starships together. One of the starships will be the tanker carrying the propellant while the other will be a receiver. Both starships will remain docked to each other until the transfer is completed. Upon completion, the receiver will proceed with its deep space exploration while the tanker may return to Earth. It can also remain in orbit to refuel the next spacecraft.

How do spaceships refuel in space?

Spaceships often refuel in orbit by docking with each other. The tanker carrying the propellant will proceed to transfer the fuel to receiving spaceships. Once the transfer is completed, the two spaceships will separate and continue their mission.

Have we ever refueled in space?

Yes, spacecraft have been refueled in space before. The first orbital refueling occurred between two satellites in March 2007. It was achieved when DARPA launched its Orbital Express satellite, which consist of two satellites. When the two satellites arrived in orbit, they docked into each other and conducted the refueling testing. The two spacecraft also followed safety undocking procedures to separate from each other.