Technology news: November 2011
Linear motor railgun hits 1,000 firings
US researchers have notched up 1,000 firings of an electromagnetic railgun – effectively, a linear motor designed to launch missiles. The US Navy is hoping to use these guns to launch long-range weapons on future all-electric warships.
The railgun is being developed and tested at the US Naval Research Laboratory (NRL) Materials Testing Facility. At present, it is being used for about 15 test firings (like the one shown above) each week.
A railgun is a form of single-turn linear motor. Magnetic fields generated by high currents in parallel conductor rails, accelerate a sliding conductor (the armature) between the rails. The velocity generated by the system is limited by the strength of the rail and armature materials, and their response to the high currents and extreme pressures generated during launch.
Many of the 1,000 test shots fired using the NRL’s Materials Testing Facility railgun have been designed to test different barrel designs and to quantify the damage caused during high-power launches.
The heat generated during launches is sufficient to melt most metals, including the armature material. This heat and the extreme pressures can damage the rail surface and destroy the contact surfaces and the gun barrel. The NRL researchers have pioneered several barrel and armature designs to minimise or mitigate this damage, even during successive high-power launches.
When the NRL’s railgun was first fired in March 2007, it produced 0.5 megajoules of energy. Since then, the system has been modified and enhanced and now operates at around 1.5MJ. (A 1-tonne object moving at 160km/h has about 1MJ of kinetic energy.)
“A railgun weapons system must be able to launch hundreds of projectiles and withstand extreme pressures, currents and temperatures,” says the NRL’s commanding officer, Capt. Paul Stewart. “The firing of the one-thousandth shot demonstrates Navy researchers are steadily progressing toward achieving that goal, developing a more effective and efficient future ship combat system.”
Knowledge gained from the railgun testing programme is being fed into an electromagnetic railgun programme being run by the US Office of Naval Research, which is conducting full-scale railgun tests at the Naval Surface Warfare Center in Virginia.