Why is The US Building Aluminum Warships?

traditionally speaking navies around the world built warships entirely from steel but the rapid advancement of computers and other electronics had a profound impact on the warships design and it's not what you think early computers and related equipment like radars sonars and weapon systems were quite bulky and required a lot of space the increase in the amount of electronic equipment that needed to be installed on ships had a significant impact on the size of the ships mostly due to the volume of space required but this new equipment and more importantly antennas had to be placed correctly in order to avoid interference you can't just place them anywhere moreover the radiation emitted by powerful radars also became of concern which further complicated superstructure and mast arrangements all of this new topside equipment resulted in a higher vertical center of gravity which affected the stability of the ship and that problem had to be fixed the solution was to build lighter aluminum megastructures on top of the steel hull which would lower the center of gravity despite warnings against using aluminum the us navy proceeded to build numerous classes of ships with steel hulls and aluminum superstructures but little did they know at the time that this decision was a ticking bomb that would affect the entire aluminum fleet the first reality check with aluminum occurred in november of 1975 when uss belknap collided with aircraft carrier uss john f kennedy that killed eight sailors the cruiser's aluminum superstructure simply perished in flames which lasted for two and a half hours while aluminum doesn't burn it has a melting point of just 640 celsius or 1184 fahrenheit compared to 1450 celsius or 2642 fahrenheit for steel more importantly aluminum starts losing its mechanical strength in temperatures as low as 150 celsius or 302 fahrenheit no wonder that aluminum decks and bulkheads melted and collapsed in the path of a fire two years later in 1977 the royal navy experienced its own reality check with aluminum aboard a new type 21 frigate which used aluminum alloy in its superstructure to reduce weight a fuel leak caused a major fire in the engine room of hms amazon the blaze distorted the aluminum ladders and that prevented firefighters from reaching the fire in a timely manner as a result of the incident the royal navy reverted back to using steel and ships megastructures in 1982 during the falklands war two more type 21 frigates were lost during combat the loss of both hms ardent and hms antelope was attributed to their aluminum superstructures but that is not what actually happened hms ardent was lost due to multiple waves of air attacks that disabled the ship's weaponry and propulsion systems the damage was catastrophic so a decision was made to abandon ship while hms antelope survived the air attacks he got hit by a 1 000 pound bomb that failed to explode the first three attempts to remotely defuse the bomb failed during the fourth attempt a small explosive charge was placed on the fuse in order to disable it but it ended up exploding the bomb which in turn split the ship in half the commanding officer gave the order to abandon ship and only five minutes after the last person left the missile magazine exploded another myth is that hms sheffield was lost due to aluminum superstructure that made her more vulnerable the truth is that hms sheffield had an all steel superstructure but even that didn't save the ship from a massive fire that eventually sunk the ship when it was hit by an exorcist missile in fact out of the royal navy's nine ships sunk during the fall clans war only three had aluminum superstructures if this tells us anything is that with modern weapons it just doesn't matter what the ship is made of as the weapons are just too lethal take a note of this incident as this will be pivotal when we later talk about why the u.s navy resumed building ships using aluminum in 1987 the u.s navy made headlines as it announced that it will build its new arleigh burke destroyers entirely from steel the aluminum industry was furious calling it a short fat ship with reduced speed and maneuverability in response the u.s navy defended their decision by citing that all of the 263 frigates destroyers and amphibious ships with aluminum superstructures had experienced cracking every single one of them the issue was twofold joining an aluminum superstructure with a seal hall sounds easier said than done due to dissimilar melting points and expansion coefficients welding aluminum to steel is very difficult but it can be done through special joints or friction welding galvanic corrosion also comes into play when joining two dissimilar metals but more on that later but once you get over the first issue of welding aluminum to steel the second issue is that steel is more resilient to stress compared to aluminum in heavy seas ships flex bending downward in wave troughs and upward on crests this puts a lot of stress on the ship and while the steel hull can absorb the energy by flexing and returning to its original form aluminum cannot as it stretches and cracks oliver hazard perry class frigates anti-kinderoga cruisers probably experienced the worst cracking of all according to the u.s navy the average cost of alterations was about 450 000 dollars per ship back in 1987. the aluminum industry once again fought back saying that cracking was a design problem and not a material problem putting the bias aside it appears that the industry was at least partially correct tyconderoga class design was simplified by putting a huge superstructure on the spruance-class destroyer hull which overloaded the ship the idea was to save money on design which resulted in waste of money in the long term due to cracks in the superstructure in 1985 the u.s navy's survivability review group officially concluded that aluminum ship structure was highly vulnerable to fire spread and loss of strength so the decision was made to require all deck houses and superstructures to be made of steel so engineers had to figure out a way to put all of the taiken deroga's gadgetry primarily the aegis combat system into a wider hall of a destroyer the shrinkage of electronic equipment helped with that goal in the early 2000s the government reversed its policy of requiring ships megastructures to be built from steel this impacted the two new classes of littoral combat ships lcs-1 freedom class was to have its megastructure built from aluminum but have a steel hull while lcs2 independence class was to be built entirely from aluminum but why build these ships from aluminum given the many issues that had already been experienced first thing to consider is that both lcs-1 and lcs2 are expendable vessels as they are graded at level one plus on survivability scale if you're not familiar there are three survivability standards in the us navy level one low survivability vessels that include replenishment ships mine and patrol craft level 2 medium survivability vessels such as frigates and amphibious ships and level 3 high survivability vessels such as cruisers destroyers and aircraft carriers level 1 plus refers to ships that need to rely on sensors and speed to avoid being hit if hit the ship would withdraw from battle or even conduct an orderly abandoned ship procedure unlike the ships designed for higher levels of survivability but critics say that in today's world of missiles it doesn't really matter how fast you can go as missiles will eventually get you in case you're curious how damage from missiles look like on an aluminum ship here is hsv swift from four reported shoulder-fired rockets the second reason that littoral combat ships use aluminum is that despite its shortcomings aluminum has some advantages the biggest of which is its density at one third that of steel a lighter ship means lighter overall displacement meaning that smaller engines can be used smaller engines mean more room for additional equipment such as weapons and sensors no bias here according to ostol the company that built the aluminum ships aluminum hulls offer 21 fuel savings per year on a 56 meter aluminum hull patrol ship versus the equivalent steel hulls aluminum is also non-magnetic which reduces susceptibility to mines the third advantage is that aluminum is inherently a corrosion resistant metal as a protective aluminum oxide layer forms on metal surfaces when it's exposed which actually protects the metal thus aluminum vessels do not need to be painted above the water line which reduces maintenance but what about all the downsides of aluminum such as galvanic corrosion low fire resistance and cracking well it's been decades since the first aluminum superstructures were installed on the u.s navy ships so many lessons have been learned or have they the first two ships of the independence class suffered from aggressive corrosion especially around the water jets the issue was caused due to galvanic corrosion caused by the aluminum hull being in contact with the stainless steel propulsion system with seawater acting as an electrolyte ostel the company that built the ships insisted that it was not poor craftsmanship that led to the corrosion but poor maintenance ostel ceo said in an interview that his company built 230 vessels of this type that had not suffered from this type of problem we actually checked and verified that statement as true as you have to look no further than the expeditionary fast transports or epfs built by ostol for the u.s navy which have aluminum hulls and do not suffer from corrosion as of march 2021 it appears that the corrosion problem on the independence class ships was fixed by installation of cathodic protection system and anti-corrosion surface treatments but still steel is undeniably superior to aluminum given its thermal properties but the thermal issues with aluminum can be mitigated a good example is the space shuttle which was built from aluminum the space shuttle experienced temperatures in excess of 1600 celsius or 3000 fahrenheit during its re-entry to the earth's atmosphere but thermal protective tiles prevented the shuttle from melting independence class ships use remote fire suppression systems and ceramic fiber wool systems in key areas based on the navy's testing of fire insulation on the lcs class ships it is unlikely that an internal fire would cause major damage to the aluminum structure however the u.s navy has not assessed the likelihood of a major structural damage caused by a weapon induced fire lastly the cracking of aluminum can be prevented by proper design and quality craftsmanship while there have been reports of mild stress cracks of the aluminum superstructure on the freedom class ships which were consequently addressed by design changes it was actually the steel hall below the water line that experienced the biggest cracks ranging from 3 to 6 inches it is possible to design a ship using aluminum that will last for a long time without major problems just look at the hamilton class cutters that lasted over 40 years with aluminum superstructures sailing in the roughs of the bering sea in fact all of the cutters are still in service either with the united states or other countries some cracking was noted but nothing that couldn't be fixed but that said the newest legend class cutter is made from steel so there's still some considerations for steel in 2016 the u.s navy conducted full ship shock trials and both freedom and independence classes performed outstandingly with no major damage both ships returned back to port on their own but if you dig a little bit deeper the shock trials did reveal critical shock deficiencies the details of which are classified what is publicly known is that freedom class shock trials stopped after two out of the three scheduled blasts the third blast which was designed at 66 percent of the maximum force the ship was designed to handle was deemed to be too risky and was subsequently cancelled the russians recently unveiled an admiral gorshkov class frigate which has a superstructure built from composite materials such as carbon fiber russians claim that carbon fiber exceeds steel in terms of physical properties but elon musk's spacex disagrees with that evaluation as they ditched carbon fiber and used stainless steel on the starships so what should we make of all this the reality is that if a small diesel submarine can sink an aircraft carrier during war gaming exercises is it really necessary to debate survivability of steel versus aluminum as the events during the fall clans war show a hard hit can sink any ship regardless of it being made of aluminum or steel with that said the united states navy is adding an extra 300 tons of steel to the design of the new constellation class frigate in order to increase its survivability but the question is is that enough to save a ship from modern anti-ship missiles during an actual war hopefully we'll never find out

Channel: Not What You Think

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Keywords: not what you think, navy, austal, lockeed martin, us navy, warships, arleigh burke, lcs, littoral combat ship, lcs independence, lcs freedom, USS Freedom, USS Independence, steel, aluminium, marine, frigate, destroyer, aircraft carrier, trimaran, Aluminum vs steel, Aluminium vs steel, Aluminium, Aluminum

Id: stzOqv9xS4M

Length: 14min 20sec (860 seconds)

Published: Fri Mar 26 2021