The Gross Takeoff Weight (GTOW) of a spacecraft, often referred to as the Gross Launch Mass, is the total weight of the spacecraft at the moment of liftoff or launch. It includes not only the spacecraft’s payload, which may be scientific instruments, satellites, or cargo, but also all the other components and systems needed for the mission, such as the spacecraft structure, propulsion system, fuel, and other equipment.
The formula for calculating the Gross Takeoff Weight (GTOW) of a spacecraft is relatively straightforward:
GTOW=Payload Mass+ Spacecraft Structural Mass+ Propellant Mass+ Other Equipment Mass
Where:
- is the Gross Takeoff Weight of the spacecraft (typically measured in kilograms or pounds).
- is the mass of the payload or cargo that the spacecraft is intended to carry.
- is the mass of the spacecraft’s structure, including the spacecraft’s body, frames, and other structural components.
- is the mass of the propellant (fuel) needed for the spacecraft’s propulsion system, which can include both the fuel and oxidizer.
- includes the mass of all other necessary systems, components, and equipment required for the mission, such as power systems, avionics, thermal control, and scientific instruments.
The GTOW is a critical parameter for spacecraft design, engineering, and mission planning. It impacts the selection of launch vehicles, the design of the spacecraft’s structure and propulsion system, and the determination of the mission’s overall cost and feasibility. Reducing the GTOW while maintaining mission requirements is a common goal in spacecraft design, as it can lead to more cost-effective and efficient missions.