The electromagnetic rail aircraft launch system: Implementation and issues

Part 1 of this FAQ explored the basics of the EMALS “railgun” technology being implemented for launching aircraft from carriers; this part details the actual installation on a carrier.

Q: What are the various subsystems the EMAL system?

A: The overall design has six major functional blocks, (Figure 1).

The Prime Power Interface, which is the interconnect to the ship’s electrical distribution system (which is sourced by nuclear reactors) and delivers power to drive the energy-storage rotors;
The Launch Motor (the linear-induction motor discussed above);
The Power-Conversion Electronics, which takes the energy stored in the rotors and converts it to the carefully timed wave to energize the series of windings of the launch motor. The power switches which control the windings are located below deck; the switching for each winding is controlled by a module built of solid-state SCR and IGBT devices;
The Launch Control, which manages the current delivered to the launch motor windings for smooth, tailored acceleration, with closed-loop feedback for precision as conditions vary;
The Energy Storage motor-generator rotors (also discussed above);
The Energy Distribution System, which includes the cables, disconnects, and terminations needed to deliver the energy from the power-conversion system to the launch motor.

Electromagnetic Aircraft Launch System — Fig 1: The EMALS design consists of closely linked functional blocks which generate, manage megawatts in a confined space, under stressful conditions. (Image: Defense Industry Daily, LLC)

Q: What are some of the technical innovations?

A: There are many, of course. On the electrical side, one key component is the multi-component IGBT/SCR module which switches megamps to the windings of the motor (one per winding) in milliseconds, as well as the components of the circuitry which controls those modules. Mechanically, the EMALS needs high-strength, defect-free materials for the motor-generator’s rotor, along with advanced bearings for the rotor.

Clearly, in a system of this complexity and power levels, there are no minor details. Every “wire” (actually, huge bus bars), every connection, every action is of a physical size and electrical magnitude where any mistake, imperfection, or oversight has serious and likely disastrous consequences. Any action or “fix” must be carefully evaluated, as there is no tolerance for hasty, improvised, or temporary solutions. For those used to thinking in terms of volts, amps, and watts representing far lessor amounts of power and energy, it’s a very different world in every respect.

Q: What about the landing arresting system?

A: The related landing-arresting subsystem, called the Advanced Arresting Gear (AAG) sub-program, will replace the present hydraulic-ram based system and provide adjustable firmness and flexibility in managing the shock absorption and retarding of carrier’s arresting wires. It uses energy-absorbing water turbines and a large induction motor to provide the adaptable, fine-tuned control of the forces and payout on the wires. It is designed to handle a wide range of aircraft (including some which are heavier than the present arresting system can accommodate), and reduce staffing and maintenance while adding self-diagnosis, performance analysis, and detailed system-status indicators.

Q: What has been the progress of the EMALS system thus far?

A: In short, very difficult. There are implementation issues as well as some possible fundamental architectural flaws.

Q: What are some of the specifics of the evaluation phase?

A: On May 15, 2015, after a series of land-based tests, the Navy conducted its first shipboard full-speed EMALS catapult test shots called “no-load” (there was no weight attached to the launching shuttle). The purpose of the test was to verify the integration of the catapult system. The next test phase began several days later with a series of “dead load” launches, using wheeled steel vessels weighing up to 80,000 pounds to simulate the weight of an aircraft, to verify that the catapult and each of its components were working properly.

The first successful dead load weighed 15,000 pounds and launched at 140 knots; the second one was 8,000 pounds and traveled at 180 knots. Over the three days, 15 sleds of varying weights and speeds were launched. (As a testament to “Murphy’s law/stuff happens,” the media was present for that first test launch; when the button was pushed, absolutely nothing happened — apparently some miscommunication between various subsystems and software. All the successful tests were done after the media left.)

Q: So far, sounds OK — so what has happened since?

A: The first system is installed on the $10 billion-plus carrier USS Gerald R. Ford. One of the many issues that have plagued the ship — causing years of schedule slippages and cost overruns — has been the reliability of the electromagnetic catapults and arresting gear, which a Pentagon report said has proven unreliable thus far under all but the best conditions. In January of 2018, the Pentagon’s test and evaluation office released a report saying that the electromagnetic catapults suffered a critical failure after an average 455 launches — a rate nine times higher than the Navy’s threshold requirement.

To put it another way, that failure rate means a Ford-class carrier has approximately a 70 percent chance of completing one day of sustained operations without a failure. When a problem does occur, the crew must wait about 90 minutes for the system’s generators and motors to shut down before they can even begin looking into the system to see what went wrong.

Q: What about the landing and arresting systems?

A: The first arrested landing aboard the ship took place on July 28, 2018, and the Ford has seen over 750 F/A-18 landings.

Q: Sounds like normal “start-up pains” for an advanced technology — is that it?

A: Apparently not. The underlying design requires that all four launch rails and the entire system be shut down for repair or maintenance. With steam-based systems, a single catapult can be taken offline while the others remain in use. Changing that EMALS constraint requires a major redesign and re-build.

Q: What’s the latest development?

A: Even President Trump has gotten involved, declaring in May 2019 that the electromagnetic system is way too complicated, too digital, needs an “Einstein” to operate, and too risky for a combat role. He further insisted that future carriers should use steam, including the post-Ford carriers now under construction. Both the EMALS technical issues and news of the president’s comments have received extensive coverage, see References.

Of course, redesigning a carrier under construction to go back to steam is an enormous undertaking (time and cost), but there are many experienced carrier officers who agree and who are quite skeptical of this radically new approach. It is definitely a system with many “issues” remaining and which is untested under full-engagement, high-intensity, full-on situations.

Q: So, what’s the long-term prognosis?

A: Check back in three-to-five years…or maybe longer. Then we’ll know more!

References (both technical and “news”)