We are going to produce a complete design for a cargo airship. The requirements are that it should be able to carry at least 500 metric tons of cargo at least 12,000 km at least 90 km/h in 15 km/h headwinds. It should be fully lighter than air, have rigid structure, and use hydrogen lifting gas. What is the first step?  The first step in designing a cargo airship to meet your requirements is to define the conceptual design framework. This includes establishing the basic parameters and understanding how they interrelate to ensure that the final airship design will meet the performance criteria. Here are the steps you should follow initially:
1. Define Mission Requirements and Parameters:
 Cargo Capacity: At least 500 metric tons.
 Range: At least 12,000 km.
 Speed: At least 90 km/h in 15 km/h headwinds (effectively 75 km/h relative to the ground).
 Altitude: Understand the operational ceiling as it might influence aerodynamic and structural design.
2. Research and Selection of Lifting Gas:
 Hydrogen: As specified, you will be using hydrogen, which is lighter and provides more lift compared to helium but poses greater safety risks due to its flammability.
3. Review Aerodynamic and Structural Considerations:
 Rigid Structure: Since the airship will use a rigid structure, understand the materials and geometric considerations for creating a strong but lightweight frame.
 Aerodynamics: Initial estimations of shape (e.g., streamlined ellipsoid) to minimize drag and optimize lift.
4. Preliminary Volume and Buoyancy Calculations:
 Calculate the volume of hydrogen gas needed to lift the total weight of the airship, including its structural mass, payload, fuel, and other systems.
Example Calculation:
 Hydrogen Lifting Capacity: Hydrogen can lift approximately 1 kg per 11 m³.
 Total Lift Requirement: Must include cargo (500,000 kg), structure, fuel, and additional subsystems.
5. Draft Initial Layout:
 Sketch an initial design outline focusing on:
 Hull Design: Shape and size to accommodate the volume of hydrogen required.
 Cargo Bay: Placement and structural integration.
 Propulsion Systems: Determine the type and placement of engines necessary to achieve the required speed and range.
6. Structural Material Selection:
 Research strong, lightweight materials (e.g., aluminum alloys, carbon fiber composites) suitable for constructing the rigid frame and skin.
7. Initial Systems Design:
 Propulsion: Consider hybrid systems that integrate internal combustion engines or fuel cells with electric motors.
 Flight Control: Aerodynamic control surfaces like fins and ballast systems.
With these initial steps, you would establish a strong foundation for subsequent detailed design, analysis, and optimization. The first concrete task would be to carry out detailed volumetric calculations to determine the exact dimensions and layout of the airship necessary to support its estimated total weight and to ensure adequate lift with hydrogen gas. 
We are going to produce a complete design for a cargo airship. The requirements are that it should be able to carry at least 500 metric tons of cargo at least 12,000 km at least 90 km/h in 15 km/h headwinds. It should be fully lighter than air, have rigid structure, and use hydrogen lifting gas. What is the first step?  The first step in designing a cargo airship with these specifications is to conduct a preliminary sizing analysis. This will help determine the approximate dimensions and volume of the airship needed to meet the cargo capacity and range requirements. Here's how to approach this initial step:

Calculate the required lifting gas volume:
 Determine the total mass that needs to be lifted (cargo + airship structure + fuel + crew + equipment)
 Calculate the lifting force of hydrogen at the operating altitude
 Estimate the volume of hydrogen needed to provide sufficient lift

Estimate the aerodynamic characteristics:
 Determine the rough shape and dimensions of the airship
 Estimate the drag coefficient based on the shape
 Calculate the power required to maintain the specified cruise speed in given wind conditions

Perform an initial weight estimation:
 Estimate the weight of the rigid structure
 Estimate the weight of propulsion systems, fuel, and other necessary equipment
 Ensure the total weight plus cargo capacity can be lifted by the calculated hydrogen volume

Conduct a basic range analysis:
 Estimate fuel consumption based on the power required
 Calculate the fuel needed for the specified range
 Verify that the airship can carry enough fuel for the required range

Iterate and refine:
 Adjust the initial estimates as needed to meet all requirements
 Balance between size, weight, and performance
This preliminary sizing analysis will provide a starting point for more detailed design work in subsequent steps. It's important to note that this process may require several iterations to find a feasible initial design that meets all the specified requirements. 