Most space mission systems have historically used a single spacecraft designed to complete an entire mission independently. Whether it was a weather satellite or a human-manned module like Apollo, almost every spacecraft was deployed and carried out its single mission completely independently.
But now, organizations in the space industry are exploring missions with many satellites working together. SpaceX’s Starlink constellations, for example, include thousands of satellites. And new spacecraft could soon have the ability to connect or contact other satellites in orbit for repairs or refueling.
Some of these spacecraft are already operational and serving customers, such as Northrop Grumman’s Mission Extension Vehicle. This spacecraft has extended the life of several communications satellites.
These new design possibilities and the capabilities of space are making space missions increasingly resemble large logistical operations on Earth.
We are researchers who have been studying the space industry for years. We have investigated how the space industry can learn lessons from companies like Amazon or FedEx about managing complex fleets and coordinating operations.
Lessons from the ground transportation network
Space mission designers plan routes to get their payloads to the Moon or Mars, or to get into orbit efficiently within a set of cost, time, and capacity constraints. But when they have to coordinate multiple spacecraft working together, route planning can get complicated.
Ground-based logistics companies solve similar problems every day, transporting goods and resources around the world. So researchers can study how these companies manage their logistics to help space companies and agencies figure out how to successfully plan their missions.
A NASA-funded study in the early 2000s had an idea to simulate logistics operations in space. These researchers viewed orbits or planets as cities and the trajectories connecting them as routes. They also viewed cargo, consumables, fuel and other items to be transported as commodities.
This approach helped them reframe the space mission problem as a freight flow problem – a type of question that ground logistics companies are constantly addressing.
Lessons from the Ground Logistics Infrastructure
New possibilities for refueling and repairing spacecraft in space create new opportunities, but also challenges.
Namely, space operators usually don’t know which satellite will fail next or when it will happen. To make these new technologies useful, space mission designers would have to come up with an infrastructure system. That might look like a fleet of service vehicles and depots in space that can respond quickly to unpredictable events.
Fortunately, space mission designers can learn from operations on the ground. City planners and emergency response organizations think about these kinds of challenges as they decide where to locate hospitals or fire departments. They also consider the capabilities of these facilities to respond to unpredictable calls.
We can draw an analogy between the design of a ground logistics system and the design of an in-space servicing system. In this way, researchers can use theories developed for ground logistics to improve the practice of space mission design.
One study published in November 2020 developed a framework for operating spacecraft in orbit using what logistics experts call spatial queuing theory. Researchers typically use this modeling theory to analyze the performance of a ground logistics system.
Lessons from ground warehouse management
In the past, individual spacecraft would carry out their missions independently. If a satellite failed, mission engineers would develop and send up a replacement satellite.
Today, in multi-satellite missions such as the Iridium satellite network, operators often keep one or more spare satellites in space.
This gets complicated for constellations consisting of hundreds or thousands of spacecraft. Mission designers want to make sure they have enough spare satellites in orbit so they don’t have to abort the mission if one fails. But sending too many spare satellites gets expensive.
When dealing with these kinds of large constellations, mission designers can learn from the methods that Amazon and other ground companies use to manage their warehouses. Amazon places these warehouses in specific locations and fills them with certain items to ensure that deliveries are handled efficiently.
Theories about ground inventory management can help guide how space companies address these challenges.
A study published in November 2019 developed an approach that space companies can use to manage their reserve strategies. This approach can help them decide where in orbit to allocate their spare satellites to meet their needs while minimizing service disruptions.
International dimensions
Spacecraft operate in a complex and rapidly changing environment. Operators need to know where other missions are operating and what rules to follow when refueling or repairing in space. In space, however, no one has defined these rules.
Ships, aircraft, and ground vehicles all have clear traffic rules that they must follow when interacting with other vehicles. For example, civilian ships and aircraft must share their location with other vehicles and officials to regulate traffic.
Some researchers are exploring what similar rules might look like for space. One study examined how developing rules based on a spacecraft’s size, age, or other characteristics could make future space operations run more smoothly. For example, a rule might require the spacecraft that launched most recently to take responsibility for maneuvers when another craft is in its path.
With more satellites and spacecraft being launched than ever before, companies and government agencies need new technologies and policies to coordinate them. As space activities become more complex, researchers can continue to apply what they’ve learned on the ground to new missions in space.
This article is republished from The Conversation, a nonprofit, independent news organization that brings you facts and reliable analysis to help you understand our complex world. It was written by: Koki Ho, Georgia Institute of Technology and Mariel Borowitz, Georgia Institute of Technology
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Koki Ho receives funding from NASA, AFRL, NSF, and industry. He is affiliated with the American Institute of Aeronautics and Astronautics (AIAA) and the Consortium for Space Mobility and In-Space Servicing, Assembly, and Manufacturing Capabilities (COSMIC).
Mariel Borowitz has received funding from the National Aeronautics and Space Administration, the National Science Foundation, and the U.S. Department of Defense. In addition to her work at Georgia Tech, she is currently affiliated with the U.S. Office of Space Commerce. However, the views expressed here are her own and do not represent any organization.