The High-speed Sea Service, or Stena HSS is the name commonly given to type of high-speed craft developed and operated by the Stena Shipping Line. Currently, Stena has four catamaran HSS ferries. The HSS 1500 are the largest "fastcraft" in the world, with an in-service speed of 40 knots (75 km/h). Several patents were registered to Stena Line in the development of the HSS.
- 900 passengers + 208 cars, or 151 cars + 10 coaches
- 89.75 m × 30.47 m × 3.9 m draft
- 8,631 tonnes
- 33,500 kW (2 × ABB–STAL GT35)(Siemens SGT 500)
Fuel Heavy oil fuel IF-100
Originally two HSS 900 vessels were ordered, the second one was scrapped—whilst being only partially (30%) complete—following bankruptcy of the shipyard.
Since the start of 2007, two identical 1500 passenger versions remain in operation from the United Kingdom
on routes across the Irish Sea
, whilst a smaller, 900 passenger version operates a route across the Baltic:
Withdrawal of Stena Discovery in 2007
was taken off the Hoek van Holland
route on 8 January 2007
, with her final in-service trip being the 10:40 ex-Harwich, returning to her home port of Hoek van Holland.
Taking a route via Dover and the Isle of Wight she arrived in Belfast, Northern Ireland on 24 January 2007 "to join her sisters on the Irish Sea", pending use as spare parts or possible sale. Any future use is still uncertain, with Pim De Lange, Stena Line's director of North Sea operations quoted as stating that Stena Discovery has been returned to the care of Stena Ro Ro—the Swedish-based organisation's chartering arm—but that it is unlikely any other north-west European company would want to operate her.
The HSS service has been replaced with twice daily—one day, one night—sailings on a pair of traditional super ferries. The Stena Hollandica and Stena Britannica vessels are now accepting foot-passengers and were each stretched to 240 m in length at the Lloyd Werft shipyard in Germany in the spring of 2007. In addition to passenger traffic, the HSS service is believed to have been carrying around 25,000 units of freight per year—about 15% of the 165,000 units that Stena Line transport across the North Sea annually.
The reasons cited for the replacement by conventional ferries has been decreasing passenger patronage, coupled with escalating fuel costs. A report in International Freighting Weekly following the withdrawal stated that Stena Discovery operation on the North Sea route was using more fuel than Stena's seven other conventional ferries on the North Sea put together. Fuel costs for the HSS were noted in the article to have risen 40% from 2004–2005 and again by another 15% in 2005–2006, something that was "unsustainable".
- A year after Stena Carisma had been delivered, the presence of corrosion was detected at certain locations on the hull structure where welds joined aluminium alloy sections together. Stena AB were unhappy about this, but gaining compensation proved unsuccessful. In the time since delivery, the ship-builder had gone bankrupt, the deadline for notifying the alloy supplier had passed and Stena's insurers, The Swedish Club, pointed out that Stena AB's "all risks" insurance excluded "constructional defects and rust/etching". Similar corrosion had been observed on other ships using the same alloy, so the fault was found to be in the choice of material used, rather than a defect of material itself. An Adjuster ruled non-appealably in favour of the insurer—corrosion was a "construction defect" and therefore exempt. (As it happens, the Det Norske Veritas safety authority had approved the supplier, but not the alloy in question. DNV subsequently approved the particular aluminium alloy, but only for use in moisture-free areas—eg. not a ship hull).
- Upgraded Imtech N.V. UniMACS 3000 bridge navigation and control systems were fitted to Stena Explorer and Stena Carisma in early 2006. The UniMACS 3000 system includes fifteen (15) computers, five (5) display screens and dual uninterruptible power supplies. Many of the components of the new system were installed in the electrical room below the bridge during a parallel testing, development and verification phase. The remaining two HSS ships were scheduled to receive their systems at the start of 2007.
- Stena Carisma undertook a charter with the Swedish Infrastructure Minister, Ulrica Messing, to inaugurate new and upgraded marine fairways leading to Port of Göteborg on 17 November 2004.
- Following her introduction in 1997, Stena Discovery was nicknamed the The Wave Machine by locals around Harwich and Felixstowe. Certain critical ranges of speeds caused the HSS ship to produce breaking beach waves of up to 0.5 m in height, often sweeping possessions around or knocking over fully-grown adults. Over the following two years, several changes to the HSS' Harwich approach route were undertaken along with strict guidelines to minimise the duration of time spent in the critical speed range between 16 knots-34 knots found to induce significant waves. Signs were erected along affected beach-fronts along with a warning siren on the approach of the HSS.
- On 24 March 1997 Stena Explorer made a detour after departing Dún Laoghaire in order to pass close to Baily Lighthouse. Baily was the last manned lighthouse in Ireland and this day represented hand-over from keepers Eugene O’Sullivan and Anthony Burke to automatic remote operation..
- On 23 August 1998, Stena Discovery suffered berthing issues at Harwich on the incoming evening service. Docking should have taken taken place at 19:00, but passengers were off-loaded at 01:00 and sent to hotels before berthing with the Linkspan finally succeeded at 02:00. The 19:40 return trip to Hoek van Holland was cancelled, along with the what would have been the 07:20 departure. The 10:40 ex-Harwich service was also cancelled and Stena Discovery returned to Hoek van Holland light as the crew were tired and "they had run out of hamburgers".
- On 20 September 2001, Stena Explorer suffered a generator fire in one of her pontoons. Whilst reversing to dock at her berth in Holyhead, a fire was detected in her auxiliary (generator) engine room in the port pontoon. Shortly after, the CCTV system normally used for visual docking cut-off. Knowing that just-completed checks showed that fire doors (lasting at least one hour) were closed, permission to shut off the engine in question was (correctly) denied by the Master of the Ship until final approach line up with the Linkspan was confirmed. At this point the failing Cummins generator was shut-off.
In lieu of the CCTV system, docking distances were relayed to the bridge by portable radio. Berthing was complete within 5 minutes of the original fire alarm and fresh water was taken on board to replenish the Hi-fog fire suppression system whilst all 551 passengers were safely off-loaded. The fire brigade attended and the Hi-fog water mist was deactivated at their request. A 9-month Marine Accident Investigation Branch investigation found the fault to be incorrect fitting of a compression-fitting used for a high-pressure fuel line leading to fuel spraying and igniting upon contact with the hot turbo-charger unit.
- On 20 February 2007, a woman walking on the shore in Holywood, Northern Ireland claimed she and her two young children had almost been swept out to sea by a wave she believed was caused by a passing HSS ferry.
- On 15 October 2007, fire broke out in a sealed turbine unit on-board the Stena HSS Voyager en route from Stranraer to Belfast. 555 passengers and 46 crew were issued lifejackets on the 0955 BST sailing. The fire was extinguished in less than an hour by an automatic system. Nobody was injured. The service continued to travel to Belfast and later services followed as normal after the vessel was checked by authorities.