Slashdot Mirror
Navy Uses Railgun To Launch Fighter Jet
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.'"
n/t
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
Now they only need a more efficient way of catching the planes when they land.
while(1) attack(People.Sandy);
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.
"Convictions are more dangerous enemies of truth than lies."
"Dear Gaddafi, I sent you some EMAILS. I hope you get them."
-- President Sarah Palin.
Non impediti ratione cogitationus.
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, 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.
It is a miracle that curiosity survives formal education. - Einstein
USS Gerald R. Ford? You have to be kidding me. What's next. USS Chevy Chase?
because US Navy needs to launch large aircraft with significant payload (unlike the brits or russians)
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.
The concept has been advanced; but my understanding is that(beyond the capital costs of building a gigantic magnetic accelerator) there are issues, for most payloads because of the incredible acceleration needed.
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 vertical, thus travelling through more atmosphere to reach orbit). This means that your accelerator pod ends up pulling some hundreds of Gs for a few seconds, which cuts down on the sort of payloads you can launch. Water? sure. Food? some forms. Crew? only if you like meat paste...
The maximun launch weight on pure ski-jump systems are much much lower than catapult launches. The old British carriers for example were stuck launching Sea Harriers which had a max take off weight of 12000kg. The F-18 (the original one... they've all been replaced by heavier planes) had an EMPTY weight just 1000kg less than that. It's max take off weight from a US Carrier was almost over twice that of the Sea Harrier.
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.
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.
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
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.
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 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
Without catapults none of these aircraft would get off the deck.
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.
Do not mock my vision of impractical footwear
The Brits converted their F-35B order to F-35C's in October.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
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.