By considering a proposal to put filling stations in the sky, NASA is looking to accelerate plans to send astronauts to distant destinations.

The filling stations — NASA calls them propellant depots — would refuel a spacecraft in orbit before it headed out to the moon, an asteroid or eventually Mars. Currently, all of the fuel needed for a mission is carried up with the rocket, and the weight of the fuel limits the size of the spacecraft.

Next month, engineers will meet at NASA headquarters in Washington to discuss how propellant depots could be used to reach farther into space and make possible more ambitious missions using the heavy-lift rocket that NASA is planning to build. The discussions grow out of a six-month NASA study of propellant depots, completed in July.

However, the space agency has rejected the study’s most radical conclusion: that NASA could forgo the heavy-lift and use existing smaller rockets, combined with fuel depots, to reach its targets more quickly and less expensively. Those targets, for the next two decades at least, include a return to the moon or a visit to an asteroid. (A trip to Mars is unlikely until at least the 2030s.)