The Design Process

The design of a new aircraft or spacecraft is a complex, time consuming and expensive venture. There are some differences between commercial and military ventures, but both processes follow a similar pattern. The aerospace company assembles a team of engineers from all of the necessary disciplines to support the development. A chief designer who handles the technical development and a program manger who manages the overall process typically lead these teams.

Customer Requirements
This is the starting point. For a commercial aerospace product, the manufacturer will perform a market analysis to determine the needs, features and performance criteria of the customer. This differs from a military or government product for which the customer provides this information to aerospace contractors at the start of a program. It’s then up to the design team to develop the product that meets the agreed-upon performance requirements.

Conceptual Design Phase
Engineers, working with a good understanding of the customer requirements, start the "conceptual design." The objective is to determine the general size and configuration of the vehicle, which includes information such as the general body, wing and tail configurations.
 
The engineers also make estimates of the vehicle’s design parameters, such as thrust loading and wing loading, and the vehicle’s performance specifications, that include range, speed, weight and payload. At this stage, the engineers develop 3-D geometry models of the vehicle and conduct performance testing that includes computer simulations and wind tunnel testing. The goal is to select the best conceptual design and move it to the next development phase.

Preliminary Design Phase
In this phase, the engineers begin systems integration. This includes laying out the major systems of the vehicle, performing internal systems and structural arrangements, and analyzing the major loads and stresses. From this information, the engineers can accurately estimate the major characteristics of the vehicle, including its weight, stability and control, and aerodynamic performance. They then compare these major characteristics to the customer requirements. If need be, revisions are made here to ensure that the vehicle will meet its predicted performance requirements. This is typically a very iterative process and depends on the complexity of the vehicle.

Detailed Design Phase
When program leaders are satisfied with the preliminary design, a decision is made to move into the detailed design phase. In this phase the detailed structural, system design and installation drawings are developed. These drawings are used to manufacture and assemble the vehicle for flight.

Flight Test
Once the vehicle has been assembled, the flight test engineers will perform function tests on all of the systems. If the vehicle is the first of its kind, it is called a prototype. Prototypes demand special attention, as the systems need to be certified for flight. The flight test engineers must be certain the vehicle is safe for its first flight. For commercial and civil aviation aircraft in the U.S., FAA inspectors must certify the vehicle before its flight.
 
If the vehicle is in what is called Full Scale Development (FSD), which is the production version, the vehicle still must undergo a flight test program to assure that it is safe to fly. After successfully passing all testing requirements, the vehicles are turned over to the customer to be placed in operational mode.

Delivery
The delivery process is often challenging, especially with customers expecting an aircraft that is "service ready" or ready to be used immediately after delivery. Aircraft customers often have tickets sold on their delivery flight home. Every system must be working flawlessly, ready to delight the flying passenger.

Note: The process described above used an aircraft as the example, but the phases are similar for any type of aerospace vehicle, including missiles and spacecraft. The design process, from customer requirements to an operational vehicle, can take as long as ten years and typically involves thousands of people and hundreds of companies.