To this end, the defence research organisation has launched the Principles of Undersea Magnetohydrodynamic Pumps (PUMP) programme, a 42-month effort aiming to build on the success of MHD at small scale by overcoming fundamental challenges.
An MHD drive would propel a boat using electric and magnetic fields with no moving parts, accelerating an electrically conductive propellant with magnetohydrodynamics.
According to DARPA, the first challenge has been the inability to generate powerful enough magnetic fields to enable high-efficiency pumps. The second has been lack of electrode materials that can withstand corrosion, hydrolysis, and erosion caused by the interaction of magnetic fields, electrical current, and saltwater. Breakthroughs in generating high magnetic fields have been demonstrated in recent years, but the electrode remains challenging.
“The best efficiency demonstrated in a magnetohydrodynamic drive to date was 1992 on the Yamato-1, a 30m vessel that achieved 6.6 knots with an efficiency of around 30 per cent using a magnetic field strength of approximately four Tesla,” said Susan Swithenbank, PUMP programme manager in DARPA’s Defence Sciences Office. “In the last couple years, the commercial fusion industry has made advances in rare-earth barium copper oxide (REBCO) magnets that have demonstrated large-scale magnetic fields as high as 20 Tesla that could potentially yield 90 per cent efficiency in a magnetohydrodynamic drive, which is worth pursuing. Now that the glass ceiling in high magnetic field generation has been broken, PUMP aims to achieve a breakthrough to solve the electrode materials challenge.”
A major problem when electric current, magnetic field, and saltwater interact is the development of bubbles over the electrode surfaces, which reduce efficiency and can collapse and erode the electrode surfaces. PUMP will address different approaches to reduce the effect of hydrolysis and erosion. The programme also will enable modelling of interactions between the magnetic field, the hydrodynamic, and the electrochemical reactions, which all happen on different time and length scales.
“We’re hoping to leverage insights into novel material coatings from the fuel cell and battery industries, since they deal with the same bubble generation problem,” said Swithenbank. “We’re looking for expertise across all fields covering hydrodynamics, electrochemistry, and magnetics to form teams to help us finally realise a militarily relevant scale magnetohydrodynamic drive.”
DARPA held a PUMP Proposers Day on May 31, 2023, to outline PUMP’s objectives.
Poll: Should the UK’s railways be renationalised?
If only the track is nationalised then it is an emasculated one with limited function and improvements will be focused on existing commuter and large...