PDA

View Full Version : High Energy Laser on the F-35 Joint Strike Fighter



Midav
01-20-2005, 02:06 AM
One of the biggest challenges facing Lockheed Martin in its efforts to install a high-energy laser on the F-35 Joint Strike Fighter (JSF) is the question of what to do with all the excess heat generated by the system, according to the company's lead for directed energy programs.
Laser systems use electricity to produce highly focused beams of light, as well as considerable amounts of waste heat that must be dissipated. Lockheed Martin believes that a 100-kilowatt laser is the minimum power level needed to be an effective weapon for a fighter.

However, "to get 100 kilowatts of light out, you've got to put a megawatt of electrical power in, so somewhere along the way you've got to deal with 900 kilowatts of cooling," Tom Burris, lead for directed energy at Lockheed Martin Aeronautics, told The DAILY. "That's a ton, for a fighter that normally does tens of kilowatts of cooling."

To dissipate the heat, cooling loops will be employed to take heat from the laser system and transfer it into the aircraft's fuel tank, where it can be burned away.

"Just like a radiator in your car takes the heat from the cooling that goes into your engine and puts it into the air, this just puts it into the fuel," Burris said.

This process won't compromise the JSF's stealth, Burris said, because it will have no appreciable effect on its infrared signature.

"If you think about the amount of fuel onboard a jet aircraft, if you put all that heat in the fuel, you might raise it by a degree, something on that order," he said. "So in terms of signature, it has no impact."

Lockheed Martin plans to make space for the laser system by pulling out the Rolls-Royce-built shaft-driven lift fan in the Marine Corps short takeoff/vertical landing (STOVL) variant of the JSF (DAILY, Sept. 23). Within that 100-cubic-foot space, used largely for fuel storage in the other variants, the laser can draw wattage from a shaft connected directly to the aircraft's JSF119-611 engine.

Solid-state lasers, which use a solid material such as crystal or glass as the lasing medium, are the most mature and promising laser technology for this application, according to Lockheed Martin. Single-digit-wattage solid-state lasers already are commonplace on today's fighters, where they perform tasks such as rangefinding and target designation.

Over the summer, Lockheed Martin signed an agreement with the Air Force Research Laboratory's (AFRL) Directed Energy Directorate to cooperatively explore high-energy laser concepts for fighters (DAILY, June 6). AFRL will furnish the laser, while Lockheed Martin concentrates on integration into the aircraft.

Lockheed Martin anticipates the JSF using lasers against both air and ground targets, at a typical range of 10 kilometers (6.2 miles). The laser itself would be housed in a dome that would emerge from the aircraft when needed, Burris said.

"When you want to use it, you'll deploy the turret, so it'll pop out into the airstream," he said. "You'll get a target cue from somewhere, just like all weapons do. It'll slew over to where you think the target is, acquire the target, and then it'll start lasing it."

The earliest opportunity the company will have to place a high-energy laser system on the JSF will be beginning with the Block Four version around 2012, according to Burris.

Optics

The other major challenge in putting lasers on the JSF is keeping the laser beam focused properly as it passes through the turbulent air around the Mach 1 aircraft.

"That flow field around the aircraft will distort the laser beam," Burris said. "So you'll have to have some sort of system onboard ... that'll sense that distortion and then correct for it."

The solution is adaptive optics - a technology developed by AFRL that is already in use on the Airborne Laser (ABL) program and at many astronomical observatories around the world. An adaptive optics system performs real-time compensation for atmospheric distortion by using deformable mirrors that can "pre-distort" the beam in such a way that the atmosphere itself straightens it out.

From (http://www.aviationnow.com/avnow/news/channel_military.jsp?view=story&id=news/masd0926.xml)

Bit older article, but interesting, nonetheless.

Ratamacue
01-20-2005, 02:13 AM
Pretty cool. My question, though, is what kind of range a weapon like this would be effective over. That of a Sidewinder missile, Sparrow, AMRAAM, infinite range, etc.? I'm not terribly knowledgeable in the physics of lasers, but would its energy dissipate over longer distances or become less focused or something of that sort?

Hiroshima
01-20-2005, 03:29 AM
WTF? Why do I picture a planner doing the Dr. Evil pinky thing when this was discussed?!?

As for range, laser (being a focused beam of light) actually have a surprisingly limited range given the enviroment they're deployed in, the intensity of the light, and a few other factors.

And what is it's function beyond the obvious thing of being a weapon...what do they want to do with it? I didn't see anything in the article...

Midav
01-20-2005, 12:40 PM
Lasers Being Developed For F-35 and AC-130

DAVID A. FULGHUM/WASHINGTON

Directed-energy devices are emerging from the 'black' world as weapons for manned and unmanned aircraft

Lockheed Martin is tailoring a laser for the F-35 Joint Strike Fighter that could be ready as early as 2010 for demonstration and the start of a full-scale development program.


Lockheed Martin produced this artist's rendering of a laser-weapon-equipped F-35. Lasers will be put on manned aircraft, while the tougher to control high-power microwave weapons are slated for unmanned combat vehicles.
Variants of the solid-state laser, powered by a drive shaft from an aircraft's engine instead of batteries, also are being considered for use on AC-130 gunships and Lockheed Martin-designed unmanned aircraft. The high-energy laser system is being designed in a joint project with Raytheon.

An advantage of a directed-energy weapon is that it can shoot indefinitely and is limited only by the ability to cool it, and it's covert. "There's no huge explosion associated with its employment," a Lockheed Martin official said. "There are no pieces and parts left behind that someone can analyze to say, 'This came from the U.S.' The damage is very localized, and it's hard to tell where it came from and when it happened. It's all pretty mysterious."

A foe would be left largely clueless trying to analyze what happened and why. Planners envision scenarios where fires are set, electronic components are damaged and computer memories are erased with no collateral damage or injury to those near the target.

A Defense Science Board study last year said that several technology breakthroughs have moved high-energy lasers on fighters into the realm of the possible. Among them was increased electrical power-generation capability achieved under the "More-Electric Aircraft Project." The DSB contends that aircraft systems will be able to provide one megawatt of power in less than five years. Other rapidly developing technologies allow smaller packaging of systems. These include advanced solid-state lasers, chemical lasers with electro-regeneration of chemicals and fiber lasers.

The technical hurdles include compensating for vibrations and high g-forces that can punish the laser and beam-control system and turbulence around the aircraft. "The beam control system must be extremely dynamic to account for these fast transient processes occurring at kilohertz rates," the report said.

Lockheed Martin looked at laser concepts from TRW, Boeing and Textron, but Raytheon's appeared to be the most advanced, a company official said. Raytheon's solid-state design is "particularly suitable for JSF because it's very compact and shows promise for achieving the necessary power levels and beam quality," the Lockheed Martin official said. "The other companies don't appear to feel as confident in their ability to buy or develop a suitable laser." Company officials are also hoping that the Air Force Research Laboratory's directed-energy directorate at Kirtland AFB, N.M., or the Defense Advanced Research Projects Agency would fund some of the solid-state laser development.

A first-generation laser weapon would be able to engage aerial targets such as cruise missiles and enemy aircraft, as well as ground targets such as antiaircraft missile sites and ground vehicles. These capabilities would likely require laser power of 100 kw., analysts predict.

"That's about the minimum threshold to be a weapon," the Lockheed Martin official said. "Less than that and it's only useful against soft targets. One hundred kilowatts would also let targets be engaged at tactically significant ranges."

Except for self-defense, laser weapon designers think the minimum effective range is about 6 mi. for a fighter aircraft. As the power of solid-state lasers improves with the maturation of new technology, the range of directed-energy weapons would increase. Ideally, the laser-equipped aircraft would also carry conventional munitions. The F-35, for example, won't give up any weapon-carriage capability when the laser is installed, and it will allow a combination of effects. Lasers can provide low collateral damage and covert attack. Conventional weapons would provide longer range strike.

"Laser and HPM [high-power microwave] weapons are more like an avionics system," a company official said. "You don't go out, drop three and go home. It's always on the air vehicle, you use it when you want and, at least with solid-state technology, you're not going to run out of power."

The concept for F-35 is to have a turret, centered on the lift-fan cavity, which would extend when needed from the bottom of the aircraft. The system would be installed in the space just aft of the cockpit that was carved out to hold the vertical lift fan. With a single turret, the directed-energy weapon would be most effective against ground targets, low-flying airborne targets and for self-defense.

While conceptually the one-turret aircraft could be maneuvered to fire at other aircraft or air-to-air missiles, planners are dubious. "There's not always time to maneuver, especially in close-in self-defense situations, so you want multiple apertures," a Lockheed Martin official said. Therefore, company designers are considering a second turret that would extend from the top of the lift-fan space to cover the upper hemisphere around the aircraft. They don't yet know if they can make both turrets fit into the space that they must share with target trackers, laser, optics, power and cooling. "It will be a trade of coverage versus internal volume," he said. There also would be the option of flying a mix of aircraft, some specialized for air-to-air and others for ground attack. For demonstration purposes, the laser system would likely be installed first on a pod and later on an early model JSF airframe.

Lockheed Martin believes it has a distinct advantage in getting directed-energy weapons into the field because the F-35's unique design will allow it to supply a great deal of electrical power. Instead of having to rely on heavy, short-lived batteries to run the laser, it will be fed electrical power generated by a drive shaft run from the main engine. In the Marine Corps' short-takeoff, vertical-landing version of the F-35, the drive shaft will power the vertical lift fan. But for the Air Force and Navy versions, the empty spaces designed for the lift fan and cannon could be used for the laser weapon.

"The drive shaft has the [potential] of producing multi-megawatts of power in real time without hurting the aircraft's performance," the Lockheed Martin official said. The shaft from the engine can produce more than 27,000 shp. to drive a generator. But the rate of fire and recycle time for a laser weapon, particularly against targets at long range, may be limited by the need for thermal cooling. "You can't fire forever," he said. "The challenge is doing the cooling in near real time." What the duty cycle will be has still to be determined, but some specialists suggest that at least initially it might be a 4-sec. burst, followed by 4 sec. of cooling, then another 4-sec. burst and finally a 30-sec. cool-down before engaging two more targets.

Directed-energy, self-defense weapons with a fast recycle time for multiple shots (since two or more antiaircraft missiles are usually fired together) is considered a key concept for future warfare. By 2025, many U.S. Air Force planners believe multispectral sensor technology will overtake the ability of stealth designs to protect aircraft from air defenses.

Directed-energy weapons fall into two categories so far: high-energy lasers and HPM. Farther in the future is a plasma of ionized gas molecules that might resemble a bolt of lightning.

Lasers use thermal effects to quickly blow holes in targets, and they are being designed for use in manned aircraft, say Air Force and aerospace industry officials. A laser beam can be focused on a fuel tank to produce catastrophic damage, or it can be focused on a vehicle's engine to simply disable it. Generally, however, it is a lethal, longer range weapon.

HPM is most effective in attacking electronics, particularly computers where spikes of high power can damage components and erase computer memories. This kind of technology is seen as the weapon of choice for unmanned aircraft because spurious emissions might affect safety of flight.

From (http://www.aviationnow.com/content/publication/awst/20020708/aw32.htm)

Hope that answers the questions.

usa320
01-20-2005, 02:10 PM
id feel better with an M61A1 20mm...

AFACadet
01-20-2005, 09:04 PM
I'd go with the laser any day. The possibilites it opens up for the JSF are amazing.

Better range than a sidewinder, instantanious time to cover the distance to target, no lead needed to correct for bullet travel time or bullet drop, 360 degree coverage. Kills both air and ground targets. Nothing an enemy aircraft can do to spoof or out turn a laser beam.

Think off-boresight AA-11, ASRAAM, AIM-9X, or Python performance is amazing?

These aren't hollywood lasers. You can't see it with the eye. You can't detect it coming, and if the fire control systems are working like they should, you won't miss.

Even more, you can shoot down all incoming missiles.

The only thing they will not do very well in is low visibility or bad weather. You wont be dogfighting in bad weather though.

LazerLordz
01-20-2005, 11:32 PM
The laser should complement and not replace kinetic weapons like cannons or missiles.

Midav
01-21-2005, 01:42 AM
The laser should complement and not replace kinetic weapons like cannons or missiles.

AFACadet makes a great point.

Lasers won't replace kinetic weapons. They will accommodate them. That's also in the article.

Flagg
01-21-2005, 02:12 AM
I'm too ADD at the moment to read the whole thing but a couple of questions I have are:

Use F35 fuel tank contents as a heat sink...what about when the tanks are low? Less effective heatsink I guess

I wonder how much impact inclement weather will have on the laser's effectiveness.......especially at lower altitudes with more particulate matter in the air(like water).

Midav
01-21-2005, 02:35 AM
I'm too ADD at the moment to read the whole thing but a couple of questions I have are:

Use F35 fuel tank contents as a heat sink...what about when the tanks are low? Less effective heatsink I guess

I wonder how much impact inclement weather will have on the laser's effectiveness.......especially at lower altitudes with more particulate matter in the air(like water).

If you are low on fuel you shouldn't be in combat anyway. The lasers would be operational, just the firing in between times would be longer.

In hazy weather is a good question. Then again, that's why kinetic weapons will still be used.

Flagg
01-21-2005, 03:07 AM
I'm too ADD at the moment to read the whole thing but a couple of questions I have are:

Use F35 fuel tank contents as a heat sink...what about when the tanks are low? Less effective heatsink I guess

I wonder how much impact inclement weather will have on the laser's effectiveness.......especially at lower altitudes with more particulate matter in the air(like water).

If you are low on fuel you shouldn't be in combat anyway. The lasers would be operational, just the firing in between times would be longer.

In hazy weather is a good question. Then again, that's why kinetic weapons will still be used.

It's not a question of low, but lower.......I doubt most fighter engagements occur with full tanks.......ask any pilot, they'll tell you they are ALWAYS in the process of running out of gas ;)

Midav
01-21-2005, 03:17 AM
I'm too ADD at the moment to read the whole thing but a couple of questions I have are:

Use F35 fuel tank contents as a heat sink...what about when the tanks are low? Less effective heatsink I guess

I wonder how much impact inclement weather will have on the laser's effectiveness.......especially at lower altitudes with more particulate matter in the air(like water).

If you are low on fuel you shouldn't be in combat anyway. The lasers would be operational, just the firing in between times would be longer.

In hazy weather is a good question. Then again, that's why kinetic weapons will still be used.

It's not a question of low, but lower.......I doubt most fighter engagements occur with full tanks.......ask any pilot, they'll tell you they are ALWAYS in the process of running out of gas ;)

Good point and in the older scenarios, yes that was true. Todays drop tanks and better fuel economy negate that to a greater degree.

Then again, todays fighters hold less than 500 rounds of ammo, whilst lasers are unlimited ;)