The Explorer was powered by steam , because her operational requirements were more easily met by the use of steam. Yes diesel electric and straight diesel were around when she was being built, but neither could compete when it came to noise and vibration. A research vessel then as now has to be as quiet as possible, and the diesel engines which were around at the time of her planning and building were quite noisy and had vibration problems as well , both of which were considered difficult to solve at that time. There was even a proposal that the generating sets should be steam as well, but difficulty in sourcing suitably heavy duty sets meant that reluctantly they fitted diesel sets.
In hindsight this was a fortuitous decision as no one in 1955 could have foreseen the massive demand for electricity for scientific use , which arose over the life of the vessel. This is something which is considered at the design stage of new research vessels now, calculate the demand then at least double it, preferably quadruple it.
It should be noted that Scotia three which succeeded Explorer had a raft on which her three British Polar vee engines were mounted. The theory was that the vibration from the engines would not be passed on to the ship . The sister ship to the Scotia also had this arrangement with three Allen in line engines and an acoustic hood for good measure as well to cut down on radiated noise.
The Scotia’s raft was initially an unmitigated disaster in that the inherent vibration produced by these vee engines caused significant and destructive vibration right through out the ship , resulting in the vessel being tied up for over a year while various engineering boffins searched for a solution. They eventually came up with tuned vibration sources which were bolted to the corners of the raft . These would be tuned to an equal and opposing vibration to that produced by the British Polars, and bingo this worked. However if it ever did go out of tune, the vibration was so severe that it broke whip aerials, damaged sensitive scientific equipment , and sheared deck lights off at the bulkheads.
So , the Sir William Hardy launched just before the Explorer was also a bit of an engineering disaster, the theory was that the small medium speed diesel generating sets could be easily removed from the ship and serviced ashore at Torry Research Lab. However in practice this proved to be way more complicated and troublesome than was initially envisaged, and was abandoned. The engine room also had ventilation problems when the ship was working hard and the soaring heat led to all sorts of mechanical and other problems which meant that the ship spent quite long periods of time in port. When she was launched she has D.S.I.R. on her funnel which stood for Department of Science, Innovation and Research , however most of the locals in Torry and around the hahrbour thought it meant “Don’t sail if raining”.
Therefore the choice of steam as the main propulsion system , given her stop start work a day existence and the requirements for smooth , quiet, flexible power was the right choice in 1955. Explorer gave excellent service over her long career while other ships of her age who had been fitted with either straight diesel or diesel electric all had significant engineering problems, which shortened their operational lives.
It should also be noted that the current Scotia set a new bench mark for quiet research vessels. In fact so quiet that it became the I.C.E.S. (International Council for the Exploration of the Seas) standard. This also one of the reasons that the current Scotia has been copied by so many countries all over the world, and that her good design has been incorporated into some of the largest and most prestigious research vessels .