Space Cryomagnetics Ltd
The mystery of the whereabouts of antimatter in the universe is a question that has plagued astrophysicists for many years. Whilst recent experiments have indicated that antimatter does exist, the results have not been strong enough to prove conclusive.
A NASA–DOE supported international experiment is now being conducted in an attempt to solve this riddle. In 2003/2004 a superconducting magnet will be launched into space onto the International Space Station as part of a device to detect any particles of anti-matter that might exist.How can we help you?
The device will work by detecting particles coming in, deflecting them in a strong magnetic field and then measuring them on exit. The superconducting magnet, which will be stronger than any of the previous ones used in experiments on earth, will remain on the International Space Station for three years unattended, where it will be remotely controlled from Houston space centre.
The design, manufacture and testing of this magnet and its cryogenic system have been contracted to Space Cryomagnetics Ltd, (Scientific Magnetics is a trading name of Space Cryomagnetics Ltd) an independent Oxfordshire based company, which has been set up to produce custom-designed magnets for this and other demanding projects.
With a team of 12 people, including four engineers, it has extensive expertise in space cryogenics. Its Oxfordshire base is now considered a worldwide centre of excellence for this technology and subsequently, the only place capable of performing this complex engineering challenge on a global scale.
The challenges facing the team were abundant. The superconducting magnet needs 2500 litres of liquid helium, surrounded by an extremely high vacuum. The liquid helium will be cooled to 1.8 degrees above absolute zero and must remain at this constant temperature throughout the three-year project. If the magnet field failed to operate properly once it was in orbit, there would be no opportunity to investigate or remedy the problem, leaving the magnet irreparable in space. Furthermore, the experiment would be ruined. One thing was clear, there was to be no margin of error, in any circumstances.
Another consideration was the mechanical strength of the magnet assembly. Despite the fact that it needed to be as light as possible, and is constructed with special materials and aluminium, the magnet and vacuum case still weighs around 3.5 tons. The design would have to be strong enough to withstand the severe vibrations and acceleration of 10g at launch and on landing.
The bespoke nature of the project also meant that specialist machinery was needed to manufacture the magnet. The task of designing and manufacturing this equipment was also undertaken by the team at Space Cryomagnetics (Scientific Magnetics).
Testing and building various designs of the magnet prior to the launch would be impossible. It would be unthinkable in terms of cost, time and practicality. Furthermore, there were many and varied conditions under which the magnet needed to be tested; different pressure loads, eddy current forces, loading conditions and gravitational and magnetic pressures for it to withstand; none of these factors could be tested in total on earth. The team at Space Cryomagnetics Ltd, therefore, had one option; it was to rely on Finite Element Analysis (FEA) to underpin the entire project.
Analysis was to drive the design process; it was to become key to everything; not just a means of justifying the design, which is so often the case. However, in order to undertake the intricate analysis involved, John Ross the team leader at Space Cryomagnetics (Scientific Magnetics) needed some expert input and help.
The team has enjoyed a long-standing business partnership with Desktop Engineering; an Oxford-based IT and engineering solution provider. Desktop Engineering has vast expertise in FEA, the chosen analysis tool, and therefore it was the obvious port of call.
Bob Greensmith, Desktop Engineering’s consultant seconded to the project approached the design simply. Owing to the complexities involved, basic concept ideas in 2D were produced. These were then analysed before the concept was developed and before further analysis in an iterative loop took place.
Bob explained his methodology,
Although my approach was probably in contrast to traditional methods of design engineering, which tend to use analysis after the design is complete, this method really is the most effective way to use analysis. It ensures that mistakes are eradicated at the earliest stage possible. It speeds up the design process and helps find an optimal solution quickly.”
The most critical element of the work undertaken by Desktop Engineering was to analyse the magnet in worst-case scenarios; the most extreme conditions that the magnet could possibly encounter. These included launching the magnet with a full helium vessel, landing after an aborted launch, landing with the helium vessel half-full (which involves sloshing loads) and landing with the magnet warm (with no helium). It was crucial that the magnet was able to withstand these pressures at the analysis stage before any thought of manufacture could be entertained.
“We needed to push the magnet to its limitations in terms of stresses and applied critical pressure. We therefore input the various pressure loads, eddy forces, loading conditions and gravitational and magnetic pressures into the software to determine how much pressure the magnet could withstand,” says Bob.
Once analysis had been completed, the results needed validating. By using traditional basic hand calculations, Space Cryomagnetics (Scientific Magnetics) found that most of the results were reasonable. However, surprise results were found when analysing the effects of the rotational acceleration. The results were completely unexpected and apparently illogical. Consequently, the team had to investigate further, which complicated the proceedings. These results were later confirmed as correct by other software packages and from the experiences of companies who had encountered similar problems.
The project is still underway and broadly on schedule. There is now a firm confidence in the results that the software has produced and in the design process. Both Space Cryomagnetics (Scientific Magnetics) and Desktop Engineering are continuing to move the project forward and anticipate the day when this magnet is launched into space. Perhaps their work will become an integral piece of history of astrophysics, who knows and only time will tell.Find out more
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