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.'"
Re:A linear induction motor is not a railgun. (Score:3, Interesting)
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: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, 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: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.
Re:Carrier stumbles over chair, 1000's Embarresed (Score:3, Interesting)
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.
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: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.
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.
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.
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).
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.