On-orbit refueling is crucial for the future of human spaceflight. Large crewed spacecraft, such as SpaceX’s Starship, will expend most of their fuel launching into Earth’s orbit. To travel to the moon, Mars, and beyond, they will have to dock with another spacecraft capable of supplying the fuel needed for the long journey ahead.

Now, a new NASA satellite will test a key technology for storing and transferring cryogenic fuels in space. The Liquid Oxygen Flight demonstration (LOXSAT), scheduled to fly later this year, could play a major role in the race to return humans to the moon.

LOXSAT: Testing on-orbit refueling tech in space

NASA’s LOXSAT is scheduled to fly to low Earth orbit (LEO) this summer aboard a Rocket Lab Photon satellite bus that will be lifted to space by an Electron small-lift rocket. The mission will launch from Rocket Lab’s New Zealand facility no earlier than July 17, according to NASA.

The satellite will test fluid management capabilities required to maintain cryogenic fuels in microgravity. These fuels are highly efficient, but they must be stored at super-cold temperatures, making them challenging to manage and transfer between spacecraft.

SpaceX, for example, has yet to demonstrate on-orbit refueling with its Starship rocket. Reports suggest the company is struggling to mitigate the effects of “boiloff”, where cryogenic propellants sublimate (turn directly into a gas from their frozen state) due to constant temperature fluctuations. As boiloff occurs, pressure builds, and Starship must vent gas and lose propellant to prevent damage.

According to a NASA statement, LOXSAT will demonstrate technologies that “were selected to address the core challenges of using cryogenic, or super-cold, propellants in microgravity, including reducing boiloff, transferring propellant, maintaining tank pressure, and gauging propellant levels.”

The space agency also noted that its technology could one day enable “in-space propellant depots,” which are “essentially gas stations in space, that could support long-term exploration.”

Towards a permanent base on the moon

The LOXSAT mission is a collaboration with Eta Space of Rockledge, Florida. It is set to last for roughly nine months. According to NASA, during that time, it will test 11 different cryogenic fluid management technologies. 

ETA Space was chosen under NASA’s Tipping Point initiative, which chose 14 companies to develop technologies required for the space agency’s Artemis program. The goal of Artemis is to build a permanent base on the Moon, which will serve as a stepping stone for further human exploration of the solar system.

The U.S. and China are racing to send humans back to the Moon by the 2030s. China has already reportedly demonstrated on-orbit refueling technologies in space with its Shijian 21 and 25 satellites.

Neither nation has demonstrated on-orbit refueling between two large spacecraft. For NASA, this is a particularly pressing concern. Both Artemis lunar lander commissioned under its Human Landing System (HLS) contracts—SpaceX’s Starship HLS and Blue Origin’s Mk1 lunar lander—rely on cryogenic propellants. Before NASA can land astronauts on the Moon with its Artemis IV mission—currently scheduled for 2028—it will have to show that at least one of those landers can refuel in Earth’s orbit.

Data collected by the LOXSAT mission may inform SpaceX’s and Blue Origin’s orbital refueling efforts, boosting the Artemis program as a whole.