Determination of Landing Sites for SpaceX Boosters: Drone Ship vs. Land

SpaceX launches its Falcon 9 rockets from launch sites in Florida, primarily to the east over water, and often employs different landing strategies depending on the mission requirements and payload.

How Are Landing Sites Determined?

Given the nature of the launches, the main decision factors for where SpaceX lands its boosters revolve around the launch profile and the target orbit. If the mission profile allows, boosters can land on solid ground, but for most launches, the process involves either landing at a designated spot on a barge, a drone ship, or in an expendable crash scenario.

The decision to land on a drone ship or on land is a complex one, influenced by various factors including the payload’s weight, the specific mission's objectives, and the desired orbit.

Primary Reasons Behind Different Landing Sites

Water-Based Launch Sites: In Florida, most launches take place over water, specifically to the east. This setup eliminates the option of landing on solid ground within the launch site, thus necessitating a water landing. The launch barge can be strategically moved to a suitable landing spot, which can be more advantageous in terms of safety and precision compared to fixed land sites.

Payload Appropriateness: The specific orbit targeted by the mission also plays a crucial role. Geostationary orbit (GTO) is a critical destination for many communication satellites. The payload capacity for delivery to GTO varies based on the landing strategy. For example, a Falcon 9 can deliver up to:

3500kg if the booster returns to the launch site and lands on land. 5500kg if the booster lands on a drone ship. 6500kg if the booster is expendable and crashes into the ocean.

Pricing and Flexibility

SpaceX prices its launches based on the chosen mode of the customer's needs, taking into account the payload mass to be delivered to orbit among several other factors. Each mode—land landing, drone ship landing, and expendable crash—has its own trade-offs regarding fuel consumption and payload capacity.

Landing on Land: This involves a complex sequence of events where the booster must perform a "boost back" maneuver to flip and land safely. This approach requires additional fuel and precision, but can be advantageous for specific missions that prioritize landing on solid ground.

Drone Ship Landing: To land on a drone ship, the booster follows a more straightforward, ballistics-based trajectory, reducing fuel consumption and increasing payload capacity. This is the most common method for missions aiming to deliver larger payloads to GTO.

Expendable Crash: This is the least fuel-efficient method but can be necessary for particularly heavy payloads, as it ensures that all fuel is used to get the payload into orbit.

Conclusion

The decision of whether SpaceX lands on a drone ship or on land is influenced by the launch profile and the required orbit. For most missions, the drone ship is a more suitable and fuel-efficient choice, maximizing payload capacity for missions targeting geostationary orbits. Each scenario involves different trade-offs, and SpaceX works closely with customers to determine the optimal landing site based on mission objectives and payload.