Navy Uses Railgun To Launch Fighter Jet 314
Phoghat writes "In 2015 the aircraft carrier USS Gerald R. Ford will take to the seas and the plan is to use a railgun to launch planes, instead of steam powered catapults. From the article: 'The Navy developed its Electromagnetic Aircraft Launch System as a replacement for the steam catapults currently used on aircraft carriers. The EMALS is a linear induction motor that's capable of accelerating a 100,000 pound aircraft to 240 miles per hour in the space of 300 feet. Compared to a steam catapult, the railgun catapult is much smaller, more efficient, simpler to maintain, gentler on airframes, and can deliver up to 30% more power. It's also capable of being cranked down a whole bunch, meaning that it can also launch smaller (and more fragile) unmanned drones.'"
A linear induction motor is not a railgun. (Score:5, Informative)
n/t
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Same accelerator concept though. Maybe what they have built is flexible enough to handle both roles.
Linear induction motor that's capable of accelerating a 100,000 pound aircraft to 240 miles per hour in the space of 300 feet.
One wonders how is that any easier on the airframe?
Anyone know how you calculate G-forces in this kind of acceleration?
Re:A linear induction motor is not a railgun. (Score:5, Insightful)
Re:A linear induction motor is not a railgun. (Score:4, Interesting)
I also wonder if it is simply a smoother curve, with less bumps and jarring. This would seem to be much better for a controlled acceleration, not just at G force or final speed, but for the entire range in between. With steam, it would seem they just pushing it at full throttle for the whole distance.
Re:A linear induction motor is not a railgun. (Score:4, Informative)
Probably not, as the steam piston moves down the bore, it takes increasing volumes of steam to be delivered to maintain the constant presure and that is unlikely to be possible. The gas flowing through the pipes is going to encounter resistances which will cause presure and temperature flucuations, the nice dry superheated steam is going to have areas where condesation occures and saturated steam results causing even more flocuations. Most of these effects will be chaoic and erratic so they build some over-kill into the system to compensate. The video of the launch looked real nice and smooth, regualar steam catpults launches seem much more jerky.
Re:A linear induction motor is not a railgun. (Score:5, Interesting)
Perhaps. But depending on the capacity of the steam reservoir - which is presumably huge on a nuclear aircraft carrier - the pressure drop is almost certainly negligible. What the motor permits (just looking at the performance aspects) is the acceleration curve to be tailored to the airplane.
Re:A linear induction motor is not a railgun. (Score:5, Informative)
Perhaps. But depending on the capacity of the steam reservoir - which is presumably huge on a nuclear aircraft carrier - the pressure drop is almost certainly negligible.
It's not. I've manned the steam generator control station on an aircraft carrier, and the drop in water level and steam pressure is dramatic and it takes several minutes to recover. Of course, we had 16 steam generators on the USS Enterprise in the 80's. Perhaps the newer carriers with just 4 steam generators (2 per reactor) are more efficient. But I do recall flight ops were a very very busy time for the MMs in the hole.
This looks like a big improvement. Electricity generation is a much closer to a steady-state kind of operation for a naval nuclear power plant.
Re:A linear induction motor is not a railgun. (Score:5, Interesting)
Perhaps. But depending on the capacity of the steam reservoir - which is presumably huge on a nuclear aircraft carrier - the pressure drop is almost certainly negligible.
It's not. I've manned the steam generator control station on an aircraft carrier, and the drop in water level and steam pressure is dramatic and it takes several minutes to recover. Of course, we had 16 steam generators on the USS Enterprise in the 80's.
32. Eight reactors, 4 steam generators per reactor.
Perhaps the newer carriers with just 4 steam generators (2 per reactor) are more efficient. But I do recall flight ops were a very very busy time for the MMs in the hole.
...
Nope. Somebody was lying to you. We just needed to watch our water levels in the secondary. Which on the EnterPig you had to be on top of anyway - and that was 20+ years ago. I can't imagine how bad that ship is now.
Of course, some could fuck up even the watching of water levels. One PPWO "lost" 7,000 gallons of water - and it wasn't even during flight ops. Since the 4 steam plants on the Enterprise could be interconnected in some ways, he was calling around to the other EOS's trying to find his lost water. The joke in the wardroom later was, "How the hell can you lose 7,000 gallons of water? And not be able to find it? 7,000 gallons of water will find YOU!" Prior to this incident, this one officer's nickname was "Rock" - as in "dumb as a". After someone remarked "He's not a rock, he's a fucking boulder" because of the "lost" water, he was known as "Boulder".
The full nickname has been redacted to protect the not-so-innocent.
Re:A linear induction motor is not a railgun. (Score:4, Informative)
To accelerate a 100000 pound object to 240 mph requires an energy of 260 MJ (sorry I converted all units to SI before I started calculating so you have to convert it back to BTU or kcal or whatever the right unit for energy you want to use yourself). Assuming a linear acceleration over 300 feet to 240 mph gives an acceleration time of 1.7 s. This results in an average power of 153 MW. AFAIK there is no electrical turbine that will supply an extra 153 MW at the flip of a switch. Electrical energy has to be stored somewhere to let the catapult work.
Nyh
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They can't, but the system stores energy in flywheels, not capacitors.
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My understanding of the reason that they reduced the number of reactors after the Enterprise was that anything that took even one of them out of commission was pretty much going to reduce it to fleeing and you don't need a grip of reactors for that. The plan for a carrier is for it to be well-defended enough to not need that kind of redundancy.
The Enterprise, as the first nuclear naval vessel, went with a very conservative design - they put in one reactor to replace each of the diesel engines on the previous design, ending up with 8 reactors.
Re:A linear induction motor is not a railgun. (Score:5, Interesting)
Not necessarily. Multiple injection steam pusher is a concept old as the world. Most submarine launchers are like that - as the missile goes up more nozzles come into play on the sides giving it a good enough kick to clear the submarine and the water above it without breaking it in the process.
The article misses the biggest advantage of electric vs steam. Electric has a much lower chance of failures in sub-zero temperatures. Steam is a nasty business at -5 or less. It condenses and freezes at all the inevitable leaks along the catapult pusher path. A couple of launches and the pusher is bound to get stuck damaging the aircraft in the process.
IMHO, A ship with an electric catapult (or a ramp) has "Arctic/Antarctic war" stickered all over it. On the positive side this means that we are done with the Gulf and its surroundings. On the negative side this is one place which has seen very little war (except the North Atlantic portion of the Arctic in 1941-44).
It's more than just the weather (Score:5, Informative)
Steam systems are a nightmare to maintain in any weather conditions - switching from steam to electricity has been an ongoing process in the Navy for decades. The old Charles Adams class DDGs had all-steam propulsion plants - meaning that every oil pump, fuel pump, and every other system ran on some kind of steam. Those guys spent their lives maintaining steam turbines. As time has gone by, the Navy has gotten away from steam in a big way for exactly that reason - all that steam technology required a lot of sailors to keep running, and sailors are expensive. For what it's worth, I'm qualified as a Navy Engineering Officer of the Watch (EOOW) in 1200 lb steam, so I have some considerable personal experience with this.
I also think that you're likely to get performance improvements from EMALS. So I really doubt that this move has much to do with an anticipated Arctic war - there are big advantages to moving away from steam in any weather conditions.
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Jerk [wikipedia.org] is probably what you should look at, not acceleration.
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Agree. It looked like the acceleration could be smoother at the beginning, in the first 10th of a second. There was a big jerk at first.
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No details provided but I'd assume you can vary the current with a high degree of [computer] control. Increasing the inertia gradually, rather than an instantaneous kinetic release of steam.
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v = 400km/h = 111m/s
s = 100m
v^2 = 2as
a = v^2/2s
a = 12321/200
a = 61m/s^2
g = 9.8m/s^2
a = 6.3g
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This calculates the average acceleration over the distance. What if the acceleration is not constant. As has been stated by another poster, steam catapults accelerate better at the start than at the end. What if the initial acceleration was 8.3g at the start and linearly declined to 4.3G at the end. The final velocity would be the same and the average acceleration would be the same but the stress on the aircraft and pilot would be higher.
Another poster touched on a valid point about jerk. Nothing instantane
Re:A linear induction motor is not a railgun. (Score:5, Informative)
Same accelerator concept though.
No, it is not. It is far more similar in concept to a mass driver.
A railgun consists of two parallel, electrically conductive rails, each connected to one terminal of a charge storage device (usually a capacitor, but if you've got something better, go with it). The charge storage device is charged to full power, and then a conductive projectile is placed across the rails, completing a circuit.
The completed circuit resembles a large inductor, in that it is a large conductive loop with current flowing through it, whose inductance is proportional to the area enclosed by the loop. The magnetic field generates a force upon all the components of the railgun, but since the projectile is the only part not rigidly fixed, it is moved by the force. The force acts to increase the size of the inductive loop, driving the projectile away.
The key component to note here is that the projectile needs to be conductive, not ferromagnetic, and the rails must be exposed in order to pass current. This limits military applications because the presence of dirt in the rails could break the circuit, causing an electric arc flash, causing the system to act more like an arc welder. Also, the rails wear out due to the heating caused by the lack of superconductivity.
Read the Wikipedia articles for Railgun and Mass Driver more details.
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A mag-lev train works in the same way, but of course these use the magnetic fields for friction-free bearings as well.
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One wonders how is that any easier on the airframe?
Anyone know how you calculate G-forces in this kind of acceleration?
It isn't the total acceleration, it is the change in acceleration (jerk) that stresses the airframe. The steam catapult has a lot of jerk, the induction system can minimal jerk.
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No, they're not the same concept, and the electromagnetic plane launcher that they are building here cannot readily be re-purposed as a railgun.
The EMALS [navy.mil] (electromagnetic air launch system) is a Linear Induction Motor which works just like a standard AC motor except it has been laid out flat instead of in a circle. The launch carriage has a set of alternating magnetic poles (the stator) and it is driven by a
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Actually, it's a linear synchronous motor.
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Right you are, thanks for the correction. A linear induction motor would actually be closer to a railgun, although still not quite there.
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"I could see a role for LIM directly as a weapon only..."
It fires armed airborne bomb/missile launchers, sounds like a weapon to me.
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"I could see a role for LIM directly as a weapon only..."
It fires armed airborne bomb/missile launchers, sounds like a weapon to me.
Actually they are developing railguns for launching projectiles and weapons. If the weapon doesn't need to have a chemical propellant it makes it much smaller and you can carry a lot more. All electric propulsion is being worked on as well. This is all part of the larger Navy initiative towards all-electric ships. Electricity is cheap and plentiful when you have up to 8 reactors onboard.
As a side note, the Navy did a study for converting smaller ships to nuclear instead of oil. The cross-over point for
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I wonder if you could get a LIM up to enough velocity to launch shore bombardment shells? Then again I'm not sure enough electro-chemical storage for such a system would be any less dangerous than a powder magazine if it should be hit =)
Biri biri (Score:2)
With all this talk of railguns, vectors and accelerators, I am dissapointed that no one has posted Mikoto Misaka.
http://www.youtube.com/watch?v=Iv2v6WpuUG0 [youtube.com]
Is no one here a Raildex fan?
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Yeah, I was wondering what advantages this has over steam. Maybe it's easier to route cables than pipes? On the other hand, you're already producing steam for the engines and steam pipes don't short when they get wet.
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They are switching to the linear motors for the reliability. Steam catapults need extensive maintenance on a regular basis which cuts down on the available capacity to launch planes
Re:A linear induction motor is not a railgun. (Score:4, Informative)
A lot fewer moving parts and better control over the stroke energy
Looks like they've done over 220 test fires of this already in 2010
http://www.navair.navy.mil/NewsReleases/index.cfm?fuseaction=home.view&id=4468 [navy.mil]
http://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launch_System#Advantages [wikipedia.org]
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Much easier.
They are producing steam for the generators that produce electricity for the engines.
The Navy has been using large electrical machines on shipboard for over 100 years. I think they know how to keep seawater out of them.
Re:A linear induction motor is not a railgun. (Score:5, Interesting)
They are producing steam for the generators that produce electricity for the engines.
Are you sure about that? Isn't the Gerald Ford one of the Nimitz class carriers? Those have steam turbines to turn the screws. ...after Wikipedia lookup...
Nope, it's the first of a new class. How about that. Last time I saw an electric motor turning a screw was at prototype training following nuclear power school.
Damn! They're going to launch it with systems installed that only use half the available generating capacity. They expect to be able to put lasers on it in the future and have the juice to fire them. Sci Fi is no longer Fi.
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Uh, not so fast. The US Navy boasts almost all-weather ops.
http://www.youtube.com/watch?v=EZRMpxUniOw [youtube.com]
http://www.youtube.com/watch?v=ZoBZUQLBrp8 [youtube.com]
Launching aircraft or not, the equipment is still right there in the same spot.
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When my brother was on the USS America (1973) they had a few waves break over the flight deck during a cruise that took the ship north of the Arctic circle. He took some really spectacular pictures so not just "a story." The America was only a tad smaller than the Nimitz and Ford. They wouldn't have been there if they didn't think they could operate aircraft.
Cheers,
Dave
Re:A linear induction motor is not a railgun. (Score:4, Informative)
Re:A linear induction motor is not a railgun. (Score:5, Interesting)
As being an MM many years ago, I can attest that steam is a real bitch to deal with. First there's a lot of maintenance involved to keep the cat risers in top order. And the steam to operate them places a lot of demand on the plants. If it's hard to "make water" for some reason, some birds may not be flying that day. (Running generators to charge capacitors means you could keep a lot more of that water in closed loop and a lot more held in reserve.) Not only that, but steam isn't exactly the most efficient working medium. Steam or at least the heat associated with it has a funny tendency to leak out in places and thermal insulation isn't perfect, so you have a lot of spaces on a carrier that can inadvertently become saunas. (And it's already too F'ing hot in places like the Persian Gulf. A/C can't always win when adjacent to some steam system.) A slow leak (as opposed to a much more noticeable one that's jetting out), is going to end up with a lot of water or condensation pooling around somewhere. (There's usually catch trays for that, but that means more plumbing. And those drains can and will plug up at times. Not to mention extra valves for DZ and all that.) Also with the rush of steam in pipes, there's a LOT of noise generated. Just the whoosh of the mass moving, or constant tic-tic-tic of thermal expansion and places where water hammer may be occurring in the lines. Then of course with the steam catapult systems, there's these huge pistons. So those things are massive in their own right in addition to the weight of the aircraft. And they're not exactly easy to work on and require a whole lot of grease. If there's a big enough problem with one of those, the carrier pretty much has to go back to the shipyard.
Now some old timers may look at it with disdain, as it makes A-Div less needed aboard ship. Not to mention there'd be less talk between M-div and topside. But from my perspective, anything that means less running outside of the plant for engineering means that the ship would be operating much more efficiently. Less shit to fix, and therefore less shit to go wrong. Then again life in E-Div on a carrier will probably get more interesting, as more and more systems go from steam to electric and require EMs where MMs used to be involved.
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It's certainly an interesting post, but with all the mysterious acronyms scattered around, it kinda feels like reading the latest treatise on agile software development. Can you explain what DZ, MM, EM, A-Div, M-Div and E-Div are for better understanding?
Re:A linear induction motor is not a railgun. (Score:5, Informative)
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> EM = Electrician's Mate, think Electrical Engineer
The "Mates" are skilled technicians, not engineers.
Re:A linear induction motor is not a railgun. (Score:4, Interesting)
You know that the starting velocity is zeroish(maybe a little bit of taxiing; but negligible) and that the end velocity is 240mph; this makes calculating average acceleration over those 300 feet trivial; but it doesn't much help you in determing the actual shape of the acceleration/time graph.
It is quite possible, for instance, that an electrical system has a nearly perfectly constant acceleration, while getting the same out of a steam driven system(whose volume is presumably changing continuously) would be some fairly tricky plumbing.
From an airframe maintenance perspective, I assume that it is the sharp spikes of peak acceleration that cause the most trouble, and those are what a system capable of neatly constant acceleration could avoid...
Re:A linear induction motor is not a railgun. (Score:5, Informative)
You know that the starting velocity is zeroish(maybe a little bit of taxiing; but negligible) and that the end velocity is 240mph; this makes calculating average acceleration over those 300 feet trivial;
Actually, it doesn't. Average acceleration is defined as the change in velocity divided by the time interval over which the velocity changes: a_avg = delta v / delta t. The problem here is that you aren't given delta t, but rather the distance through which the jet accelerates. Now, if you know the acceleration is constant, it is easy to calculate the acceleration by means of the formula v_f^2 = v_i^2 + 2a delta x, but for non-constant acceleration, delta t over a fixed distance will depend on the shape of the acceleration curve. Therefore the average acceleration will also depend on the shape of the curve.
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I'll round 240 mph to 100 m/s and 300 ft to 100 m. Why? Because I don't do imperial (born and bread in the US, and use SI whenever I can).
That makes the average acceleration 100 m/s^2. Trivially. If you think that wrong, then come up with a better answer. "I think that requires too m
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Bread? Yep, you have an education from the states.
You are presuming that it was a spelling error rather than a simple typo.
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You've missed the second derived acceleration formula. a = (v^2 - u^2)/2s
Makes me sad for physics education in schools these days.
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I meant he missed the point of it. Average acceleration is a average line through the entire acceleration profile and can be simply calculated by the formula as stated by the GGGP.
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I think you meant to say "peak acceleration". You graph the acceleration at a bunch of time intervals during the launch and the peak is the highest value. (or there's a way to figure it out using calculus if you have an equation for acceleration vs time)
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- Dan.
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or the entire plane would, but it would be a small pile of metal, oil, fuel, and human remains.
Very cool (Score:3)
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I'm imagining a giant electro magnet.... :)
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Re:Very cool (Score:5, Interesting)
When I was working on the arrestor portion in 2001, we had a system controlling two linear induction motors attached to the arrestor cable. Turns out that yes, you can use this type of system to stop planes, it is effective in many situations where planes come in at odd angles (the system pulls the plane towards the center of the deck), and you can recover power from it.
However, if you wire the position encoders backwards, the motor cores eject quite violently as soon as the control system is turned on. Thankfully, interns are surprisingly good at dodging.
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So what you need then are arrestor cables for the induction motors.
Yo dawg! I heard you like stopping dawg! So I put an arrestor on your arrestor so you can stop while you stop.
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Couldn't wedge an "I" in there? (Score:3)
"Dear Gaddafi, I sent you some EMAILS. I hope you get them."
-- President Sarah Palin.
Carrier stumbles over chair, 1000's Embarresed (Score:3, Funny)
Re:Carrier stumbles over chair, 1000's Embarresed (Score:5, Informative)
USS Gerald R. Ford? You have to be kidding me. What's next. USS Chevy Chase?
Trust me, many Navy vets (including this one, who served on a carrier) are tired of the Navy naming our biggest capital ships after politicians. Layups like George Washington or Thomas Jefferson, no problem. But Gerald Ford? Really? There's a feeling in the Navy that we should stick to traditional names.... the Essex, the Hornet, the Lexington, etc, for our most prominent ships. But don't look for this practice to end, because appealing to political egos helps grease the Congressional appropriation machine.
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Maybe if they shared similar characteristics to the people they were named for.
I can see the USS Dubya never leaving dock.
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Re:Carrier stumbles over chair, 1000's Embarresed (Score:4, Informative)
Really? Not even a simple google search?
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You know that Gerald Ford had a naval career right? He lead a fire control team that saved the escort carrier USS Monterey.
Ford, Carter and George H.W. Bush all had naval careers, both Ford and Bush were on carriers and have carriers named for them, Carter was in the submarine service and has a submarine named for him.
The USS Gerald R. Ford was sunk today (Score:2)
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They did name one after Daddy Bush though. (And fair enough because he did fight in WWII in the Navy. Carter got a sub named after him because he was a sub captain.
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They did name one after Daddy Bush though. (And fair enough because he did fight in WWII in the Navy. Carter got a sub named after him because he was a sub captain.
There's a great political cartoon that came out when the Carter was commissioned... "An attack submarine???".
Re:Carrier stumbles over chair, 1000's Embarresed (Score:5, Informative)
Carter was never a sub captan. He served on a submarine but was not a commander.
Actually the shouldn't have named the sub after Jimmy Carter or the Carrier after Bush. It is tradition that no Navy ship is named after a living person. It was broken by the Burke class. It was unintentional because it takes so long to design a new ship that the Navy was sure that Burke would have passed on by the time the Burke was launched. He lived to a very ripe old age and mess up tradition.
There is no reason to not name a ship after a President of the US and what most people don't know is that Gerald R. Ford was actually a very good president under considering what he had to work with. He as also a very good and honorable man as politicians go. I don't think you can find a single blemish on his record and historians today say his pardon of Nixon was the right thing to do.
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> Ford was actually a very good president under considering what he had to work with.
Yeah! I mean, unless you consider the fall of Saigon or "Whip It Now" failures...
I'd say his greatest achievement was picking Stevens for the Supreme Court. But that only worked out so well because Stevens utterly betrayed Ford.
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The US was out of Vietnam, Congress had stopped funding the South Vietnamese military in the fall of '74, so how exactly is the Fall of Saigon Ford's fault?
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My apologies, I assumed everyone would know that, but you are right, we should explain that here.
In the US Navy's defense, they do have a "theme" where many aircraft carriers are named after U.S. Presidents:
USS John F Kennedy
USS Dwight D Eisenhower
USS Thodore Roosevelt
USS Abraham Lincoln
USS George Washington
USS Harry S. Truman
USS Ronald Reagan
USS George H.W. Bush
USS Gerald R. Ford
"Daddy Bush"
But why have a catapult at all? (Score:2)
What I'm curious about is why they're using catapults at all - the Russians [wikimedia.org] and the Brits [wikimedia.org], for example, use a "ski jump" instead. And I read somewhere (unfortunately, I can't remember where - damn you, source blindness!) that that approach is actually better, in terms of aircraft launch rate, as you don't have a complex catapult system that has to be reset for every plane.
So... why are US carriers using catapults, when they seem to me to be just another point of failure? Can someone enlighten me?
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Re:But why have a catapult at all? (Score:5, Insightful)
The new British carriers (suppose to launch Eurofighter variant) will also have a catapult.
The catapult is another point of failure. That's one reason there's 4 on a ship. And that's reason why US had an advantage. They had an unbroken string of experience designing, building, and maintaining catapult systems since the end of WW2.
Re:But why have a catapult at all? (Score:5, Informative)
Yes because cats are a better solution.
You can launch heavier aircraft with a cat than with a ski jump. The Russians and UK can not operate aircraft like the E-2. Also the UK is going to put cats on their latest carrier because the F-35b may fail.
Also a Ski jump can not launch while the carrier as at a stop which can be useful.
So yes the sky jump has one benefit but a lot of drawbacks. The Russians used them because it was a low risk for their first real carrier. The brits used them because they only had the Harrier. It did work very well for the Harrier but the Harrier was not as good of a fighter as the F-14 or F-18. It also was not as good of an attack aircraft as the F-18, A-6, or A-7. But it was better than nothing.
Re:But why have a catapult at all? (Score:5, Informative)
Where fighter and bombers get all the glory there are a few equally important heavy aircraft that need catapults to launch:
AEW:
Aircraft such as the the E-2 Hawkeye http://en.wikipedia.org/wiki/Northrop_Grumman_E-2_Hawkeye [wikipedia.org] are critical to hiding the location of the fleet. If the enemy sees a ship based radar they know where the ship and usually the fleet is. If they see an airborne radar the fleet could be very far away. Also airborne radar can see further.
COD;
Carier Onboad Delivery, Need those critical parts or personel delivered outside of helicopter range? Need to evacuate critically injured personnel? You need a long range aircraft to do it.
Tankers;
Need to extend range to a target? Need to loiter for long periods on CAP. Need a sip of fuel to get back to the carrier because you used to much afterburners in the fight? Tankers are your friend. This role is currently done in the US Navy by the F/A-18E/F http://en.wikipedia.org/wiki/F/A-18E/F_Super_Hornet#Tanker_role [wikipedia.org]
Without catapults none of these aircraft would get off the deck.
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Steam Power for the Win (Score:2)
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Anyone been to Cedar Point? (Score:2)
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And since we're talking about carrier based planes here. Imagine that you stop the car by catching the axels on a cable while going full speed.
Fighters - Railguns (Score:2)
We use railguns to shoot them up.
We use railguns to shoot them down.
Drones are more fragile? (Score:2)
Drones are more fragile? I thought they should be more robust as there are no humans in them.
But, of course, if they are built essentially as a glider with a mini engine it may well be the case.
Steam catapults can be fun (Score:2)
I used to work with an old guy whose job was to run the catapult on a carrier during the Korean War. He had some good stories about stuff they launched off the deck to "test" the catapult. The best one was an aircraft tractor that had been wrecked during a drag race below decks. Boredom and sailors don't mix.
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Isn't one of the problems with railguns that sometimes the projectile will weld itself to the rail?
Only at sufficient speeds/friction. There's no reason a railgun-based aircraft launcher would be more prone to this problem than a steam-based one.
What happens if that occurs with a jet launcher on the rail, and a plane hooked to that?
Same thing that happens now if the thing gets stuck.
Re:Rail Gun Weld (Score:5, Informative)
Only at sufficient speeds/friction. There's no reason a railgun-based aircraft launcher would be more prone to this problem than a steam-based one.
As I understand the issue, it has nothing to do with friction. In fact it's probably more likely to get welded if it's going too slowly.
A rail gun is basically an arc welder in a way, you're passing massive amount of energy in the form of electricity through the interface between the rails and projectile. A high power rail gun has enough energy passing through to basically vaporize nontrivial amounts of metal off the rails every time it's fired. If you're unlucky on the other hand it'll simply weld the projectile to the rails.
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As I understand the issue, it has nothing to do with friction. In fact it's probably more likely to get welded if it's going too slowly.
A rail gun is basically an arc welder in a way, you're passing massive amount of energy in the form of electricity through the interface between the rails and projectile.....
Think of a long, overpowered Jacob's Ladder with a slug where you'd expect the expanding arc.
Re:Rail Gun Weld (Score:5, Informative)
Isn't one of the problems with railguns that sometimes the projectile will weld itself to the rail? What happens if that occurs with a jet launcher on the rail, and a plane hooked to that?
As another poster pointed out [slashdot.org], this technically isn't a railgun. It's a linear motor. This is more like a mag-lev train. The other big advantage is that in a real railgun, the rails need frequent replacement.
If you were expecting technical accuracy from our esteemed professional Slashdot editors, that day has not yet arrived. They're still trying to figure out how to work a spell-checker and how to use basic English grammar. As long as the ad revenues and the paid account revenues keep on flowing, I suppose they don't feel much pressure to get these things right.
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Isn't one of the problems with railguns that sometimes the projectile will weld itself to the rail? What happens if that occurs with a jet launcher on the rail, and a plane hooked to that?
The pilot is in for a short, yet highly interesting flight.
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Rockets output power evenly over the entire take off. Electromagnets need a structure around the projectile to continue propelling it but there is no way to make it that tall.
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Rockets output power evenly over the entire take off. Electromagnets need a structure around the projectile to continue propelling it but there is no way to make it that tall.
You don't need "tall". You can make do with a straight, horizontal structure tangent to the planetary (or lunar) sphere. You have to punch through more atmosphere (if from the Earth, and let's not talk about noise ordinances), but you can certainly achieve orbit from a horizontal electronic accelleration structure. From the Moon, no-brainer. Less structure, make it longer. As long as it's straight enough at the muzzle you'll get your escape velocity.
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A rocket enjoys continuous thrust, so it can be relatively leisurely about reaching escape velocity. A magnetically accelerated pod has only the length of its accelerator track(and, unless you want that track to be very short or very expensive, you are likely launching at an angle other than vert
Re:Space Flight? (Score:5, Interesting)
Don't forget fuel. The least 'sci-fi' way to really open up the solar system is to use something like railguns to get fuel (and water too) to orbit for cheap, and get the crew and food to orbit using cheap things like the Dragon/Dream Chaser/Orion Lite capsules.
Most of the Saturn V stack was fuel. If we can get a reliable on-orbit refueling infrastructure in place, you could launch a moon landing on a Saturn I and do it easily within the current NASA budget. No heavy lift needed.
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A ten kilometer long track at a survivable 4g acceleration gets you to about Mach 8. Discounting air friction all the way up, you've still only got enough energy to make it about a third of the way to orbit. You can't dig down to arbitrary depths for obvious reasons. A shallow launch angle is just going to increase your frictional losses. You can't build a ramp at the end of the track without killing your crew.
Magnetic launch is a nice idea and may work fine for bulk materials that can withstand very hi
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