The challenge of interstellar travel

I am a fan of big engineering projects. Not that I do not like developing small lab experiments or participating in the development of middle-sized products. But giant projects are something different. It is where you can create dreams. Look at these examples: Apollo project, LHC, ITER. You need the workforce of thousands of people, the knowledge of various cultures, the know-how of different disciplines.

For me, the ultimate adventure in terms of engineering is certainly the achievement of interstellar travel. Yes, it not only sounds like science fiction, it is science fiction. This is an adventure that require the convergence of a huge amount of human knowledge. And it is for the moment impossible to realize it. However, it does not prevent people from thinking about it.

You can refer to several case studies, past or present: Orion, Long shot, Daedalus, Icarus. It is a very interesting exercise to imagine a mission which is not presently feasible.

First of all, it is a lot of fun: interstellar travel is pure dream: it consists in sending a man-made object between the star, in the void, at distances that our tought can not even grasp, where our sun is nothing more than a pale dot lost among thousand of others. It is like trying to reach the Big All. But I won’t try to give more words, Sci-Fi authors succeeded in a far more elegant manner and I let you refer to Alastayr Reynolds or Vernor Vinge for the magical description of these space vessels flying the sea of stars (I forgot to mention Gregory Benford too but there are others).

Second, it is a tricky exercise of design. Normally, when conceiving a big project, your basement has to be hard, made of solid proven technologies and you build your system, you integrate your components on this rocky basement. In the design of an interstellar mission, you have no solid basement: the technology that meets the requirements does not even exist. Therefore, you have two possibilities to solve this problem: either you look at the technologies and at all the possible ways to improve it to make it interstellar graded, or you take the present technology (that does not meet the requirements) and you develop a very complex system which remedies to the pitfalls of the technology. It is the classical trade-off between technology and system but here driven at its extreme end.  A representative of the first approach is the NASA Breakthrough Propulsion Physics program and one of the second approach is the Icarus project.

I must precise that, when I speak of these two methods, they are not exclusive. In the reality, it is a mix of them, a parallel approach to the same goal; the two methods feed each other in a design loop.

I won’t go in the technical problems. It is elsewhere better explained. But I want to a highlight a point which is often left in the shadow: the method to design the system itself.

The system is in charge to glue all the components together, it makes from the parts of the project something which is more than the sum of them. This work includes: defining the interfaces, the margins, the interactions between the components and the environment, justifying the safety, the reliability, the performance, making trade-offs between the sub-components and so on. Project management, quality assurance are for instance part of the system work, they are some of the tools, of the infrastructure.

Limitation of the technology is the main argument advanced to explain the difficulty of interstellar travel. But System Design is also equally limited for this purpose. In other words, there is clearly a lack of knowledge in the design methods of a system as complex as an interstellar spaceship. Have a look at the NASA Systems engineering handbook and imagine you try to apply these methods to a project like Icarus.

One advantage of this kind of utopian project is that you can think of it without much pressure: you know that you have time, people do not expect anything from you. Of course you have no money to work on it. But okay, it is only a thought exercise and the consequence is that only motivated people and dreamers step in. I want to use this blogs to make some comments or give some ideas, following the very interesting articles published either on Centauri Dreams or Icarus project. If you want more information there is also a dedicated website. of the Tau Zero Foundation.

And one last word, participating in such projects requires on fundamental quality: TO BELIEVE IN IT.

(ps: there is a hidden message in the last sentence to searchers in nuclear fusion)

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