A project can be seen as a compound of two ingredients: physics and engineering. It is a distinction that I dislike but which is all the same useful to understand how big project starts. In nuclear fusion, the physics tells which plasma configurations are the best to keep the particles confined and reach the ignition and engineering tells what kind of magnetic coils and of infrastructure is necessary to achieve this configuration. There is actually a balance to find between physics and engineering: the less you understand the physics, the more you have to use heavy engineering to palliate this lack of knowledge.
We can take the example of toroidal magnetic confinement configurations for fusion research: one possible solution is the spheromak
, where the plasma self-generates its own magnetic field, a kind of dynamo effect. It requires almost no external structure to keep confined; the problem is that it is in a permanent turbulent state which is hard to understand and to control; as a result, its confinement time is quite low (and the reduced amount of time and money accorded to this kind of projected prevented any significant progress on this type of facility). The solution chosen was to reduce the freedom of plasma by containing it inside a magnetic field. A lot of more engineering is involved and to limit its complexity, an axi-symmetric configuration was favoured; it was the birth of the tokamak
. The problem is that this configuration is stable only if you induce a toroidal current inside the plasma, which has a deep impact on its physics (creation of instabilities). Therefore, another idea was to go a step further in engineering complexity with the stellarator
and to give up the idea of axi-symmetry by twisting the magnetic field so that no more plasma current is necessary for the confinement. This short overview of the different types of fusion facilities show the difficulty to find the right balance between engineering and physics.
Aerospace is also a significant example: what prevents us from reaching Mars or even the other stars? The fact that it is impossible to find a balance between physics and engineering. Either you want to use a well-known physics based on chemical or electrical propulsion and, in this case, the cost of engineering necessary to solve the obvious shortcomings of these methods is too huge to be realistic. Or you want to use advanced physics (antimatter, warp drive or whatever exotic engines) and you areconfronted with the lack of knowledge.
Consequently, a project can start when the physics is sufficiently understood to be implemented in an engineering infrastructure with a limited level of complexity, i.e. which is tractable in terms of cost and of management (of interfaces).
Different scenarios can happen and trigger the start of a project: an unexpected discovery (for instance the H-mode confinement in tokamaks in 1982), the improvement of the technology (advances in superconductors), improvement of engineering tools (CAD, collaborative frameworks) and so on. In most cases, we have iterations over long times where both physics and engineering indicate the direction to follow in their respective fields of research.
One major difficulty in mega-projects is that the physics is multifaceted, involving many areas of interest with different conceptual tools; people in charge of preliminary designs need to have a large general culture both in physics and engineering and adequate tools to survey experiments and theoretical works with a possible impact on their projects.
The pre-design of a project is the first milestone in the connection of physics and engineering. We will see in a next post that it is the point where most of the difficulties met by a project in the later steps are rooted in.