Tuesday 11 December 2018

Rocket, Satellite And Rocket In Orbit Refueling

By Arthur Brooks


When it comes to space travel, the International Space Station and trips to the Sun, Moon, Mars or other places in the Universe, it is often necessary to refuel before a space vehicle returns to earth. As such, an orbital depot containing fuel has been placed near the earth or another body so that in orbit refueling can take place.

Without a cache of fuel stored somewhere in orbit, the resources necessary for space travel and exploration would likely be non-existent. Whereas, if these new concepts for depots can come to fruition and be placed in the infrastructure of space, space exploration and space travel could both become more frequent in the future. Although, as there are different types of depots required for the types of fuel necessary to replenish various space vehicles, it will not be an easy task.

The various types of depots include on location, or a tanker which can deliver a single load to a spacecraft while at a specific location in orbit, then depart. In most concepts and designs, in-space fuel depots do not necessarily have to be positioned at or near a space station.

Several space agencies, defense ministries, communication satellites and commercial companies such as Virgin could eventually benefit from these in-orbit storage and refilling facilities. Whereas, the life of satellites could be extended which would result in the time those satellites spend in geosynchronous orbit. As a result, space agencies have the ability to save a great deal of time, money and other resources if and when this type of refueling becomes a reality.

In the case of satellites, the satellite would participate in a rendezvous with the depot, then transfer the propellant for continued orbital maneuvers. While there had been some plans for replenishing satellites while in geosynchronous orbit in 2011, all such plans have been canceled. As such, it is hoped that these new concepts may actually be able to complete such tasks.

As more than 1/2 of a spacecraft is generally fuel, the plans call for delivery of full or partial transfers. While this is the case, there are some considerations as to how the depots could impact various rockets and spacecraft. For example, a separately launched spacecraft with a crew or payload could use a smaller launch vehicle if depots and refueling were available in orbit.

Concepts also suggest that depots could be placed behind the Moon to help reduce the costs of trips to the Moon or Mars. Whereas, others suggest that placing a depot in the orbit of Mars could also be useful with regards to reducing costs and making such missions more likely. For, only when crews can assure a safe return from Mars, the Moon or the Sun can such missions take place.

When it comes to spacecraft and rockets, 1/2 or more of the total mass is often fuel. Whereas, the larger a rocket, the more likely the engine will need to use a cryogenic fuel like liquid nitrogen or oxygen as an oxidizer due to the size and likely impulse. Still, the transfer of such materials must be done with caution due to the risk that the engine will experience boil off in the process.




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