Efficient Mega-Engineering (part 1)

July 22, 2011

Well, you probably know it, the space shuttle’s era is now over. Like many other space enthusiasts, I wonder what the future will be about: commercial space access, tourism are certainly part of this future, with, more particularly, the prodigious development of SpaceX and its launcher Falcon. But this is not what interests me in space, I like the exploration part, the discovery of new horizons, the possibility to travel even further away from mother planet. Consequently, I like projects like Icarus which thinks about the design of  an interstellar probe. With the present knowledge, it sounds unrealistic, at the limit of science fiction, but it is where the dream is, the excitation, the motivation.

This kind of project is what I call Mega Engineering: a project at the limit or even beyond technological or physics knowledge, with highly multidisciplinary interactions, all packed in a complex system, where several countries have to participate with intricate political issues. What is the difference with Big Engineering like the development of skyrockets, space shuttle, space telescopes, particle accelerators? These examples are mainly based on proven technologies and physics, the complexity comes from putting all these technologies together, the difficulty is there the system. Mega Engineering complexity comes both from the system and the technology and the physics. I think that nuclear fusion reactors can be put in this category, interstellar probes as well and even economical earth-to-orbit transportation. All these projects are based on a physics which is difficult to grasp, on a technology which is not mature and on an elaborate architecture.

I would like to have a look at the different stages of the development of a mega-engineering project, the difficulties associated to them,  and to explore the potential solutions to overcome these difficulties. Actually, for each problem, I will present two types of solution: one soft (by applying and improving existing methods) and one hard (nearing methods from science fiction).

Please, stay tuned for the first part, how the idea of a mega-engineering project comes to the light.

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Shuttle’s atmospheric reentry

July 22, 2011

While watching yesterday the last landing of a space shuttle, I heard that one of the astronauts on the ISS was observing the reentry from the cupola and I hoped that he had a camera with him. Today NASA has released the first photo of an orbiter’s reentry as seen from space, and it is spectacular!

Atlantis landing seen from the station
STS135 entering the atmosphere (Credits NASA)

The picture shows the ionization track of the air around the orbiter and . The interpretation of the picture can be misleading and can look like the photo of the ascent during launch. Actually we have to understand that the glow at the top is heading towards the back, the less brighter trail, which is already fading,  shows that the spaceship comes just from under the space station.


US to enter the Wendelstein 7X project

July 8, 2011

This is now official: several american labs will cooperate with the Max Planck Institute to the development of the stellarator Wendelstein 7X (W7X) located in Greifswald.

modul_4_umsetzung

Assembly of W7X - Credits Max Planck Institute for Plasma physics

You will find a good technical overview of the project in this presentation by T. Klinger.

One one hand, the physics of a stellarator is a bit simpler than the physics of tokamaks. On the other hand, the engineering can be seen as a nightmare because the facility is not axi-symmetric: just have a look at the shape of each coil: they all are unique.

Configuration of magnetic coils on W7X - Credit MPI-Plasma Physics

W7X will be the biggest stellarator in operation and has a budget of about 420M€; it should start in 2015.

The project was, at its beginning, controversial, because most of the funding was supported by Germany (with 30% help of the European Union) and it was seen as a competitor of ITER: some people did not see the point of spending some much on several big fusion facilities.  In addition, given the complexity, the project faced schedule and cost challenges. But the management was improved in the german way and now the construction is really on a good track. I find the smoothness very impressing, at least in comparison with ITER. But there is, I think, a good reason for this difference: there is only one main contributor, Germany. Just one head to drive and the management of interfaces becomes easier. Of course, there are other countries involved, especially Poland, but the decision process is far clearer than on ITER.

The participation of the US is a very good sign that the project is in good shape. Indeed, the budget allocated to magnetic confinement fusion is quite low (lower than on Inertial Fusion, which is also supported by military budgets) there and they already have several machines (DIII-D, Alcator C-Mod,… ) to run. I have, for instance, the feeling that ITER is not one of their priorities. That they are ready to collaborate in a foreign project, is really a very good news.

For those who are interested to work there (and they often have open positions), these are some pictures of the city of Greifswald (which has a big university):

But with hard winters!


Storm on Saturn

July 7, 2011

This picture is breathtaking!

Image credit: NASA/JPL-Caltech/SSI

They talk about it on Universe Today and Centauri Dreams.


EPS Conference: part II

July 4, 2011

I took an extended week-end to recover from the particularly busy month of June, a week-end far away from plasma physics and fusion research. But I was not finished with the summary from last week’s EPS conference in Strasbourg. This is the story of the second part of the conference.

The thursday’s session  had a taste of AIAA conference with a talk on reentry plasmas (more generally on kinetics in molecular gases) by Capitelli and one on plasma space propulsion. I must admit that I did not completely follow the  logic behind the presentation, it was a bit too fast for me; if someone has some complements, or an easy way to develop the presentation, he is welcome . I saw that there was a big consortium called Phys4entry organised for the 7th framework program of the european union. I should write a post on the issue of this FP: look at the list of participants and tell me how many they are: a lot, indeed! I would like that somebody from the EU explain me how to manage with limited funding so many interfaces between big companies, labs and startups. But this is another story.

The second talk on plasma thrusters, by E. Ahedo, had my full attention: the presentation of the requirements for space engines was good, with highlights on the two main drivers: specific impulse and thrust and the trade-off to do to achieve mission objectives. I was a bit disappointed by the presentation of the different types of thrusters. It was more an enumeration of the technical specs of each engine than an explanation of their principle. I think he should have narrowed the scope of its talk and focused on a small number of systems, for instance the Hall thruster and the Vasimr engine, which really have a lot of common parts with auxiliary systems for tokamaks and stellerators  (helicon source like in NBI, ICRF heating…). But well, he had a stringent time limit. Anyway, there also were some posters on the topic of helicon sources which have applications for these space thrusters.

We had again a full series of talks on transport (ok it is normal, it is issue #1), with ion heat transport on JET, and a special emphasis on the effect of plasma rotation. A particular noteworthy presentation concerned the I mode on Alcator C-Mod and ASDEX Upgrade by Hubbard. The I mode is an intermediate mode between the Low confinement mode and the High confinement mode, the famous H-mode. In the I mode, we have an independent control of energy and particle confinement, with a pedestal in Te and Ti but without density barrier: the energy is confinement but the particles not and fusion ashes can be swept out without extinguishing the reaction.

On the last day of the conference, we had a contact between two worlds: the world of plasma physics and the world of medicine,, with a presentation on synergistic effects in plasma-surface interactions by D. Graves and on application of non-equilibrium plasma by G. Kroesen. I won’t go into the details but the main idea is that a plasma is created in the air at the interface with the skin; the plasma enhances some  specific chemical reactions which can help, for instance, to treat wounds (with some nice pictures of them at 8.30, the day after the conference dinner!). I have a lot admiration for these people who create bridges between two continents of science: this requires to be open-minded, self-confident and of course  a bit crazy.

I followed, to finish, the parallel sessions dedicated to magnetic confinement fusion, to have a look at the numerical tools used to design and develop the plasma scenarii for ITER (by G. Giruzzi), with codes like CRONOS, METIS, HELIOS. The purpose is to develop scenarios with a strongly enhanced level of self-organization, with self-heating, Alfven eigenmodes and high bootstrap current. Well each time, I hear the phrase “self-organization”, I do not make a connection with tokamaks but with spheromaks.

Some other talks on current ramp on MAST and on current overshoot on ASDEX Upgrade to reach the improved H-mode were among the last noticeable talk I would like to mention.

All in all, an interesting conference which makes it possible thanks to a great effort of communication  to discover new areas of research. The big topic is transport driven by turbulence in tokamaks, with a subsection related to rotation. ASDEX Upgrade was very present with the use of RMF coils for the first time and it was the only big tokamak in Europe in operation last year.  People from CCFE had also very good talks, well prepared, cleared, proving once again the seriousness of this reference in scientific research.

I hope that I gave to people who were not present a feeling of the content of this conference and if you have some questions or comments, please do not hesitate.


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