A version of this article appears in the July 14 edition of Aviation Week & Space Technology.

With the F-35 taking far longer to field than planned, its F-22 numbers stemmed at 183 and little money on the horizon for new programs, the U.S. Air Force now faces decades before it can achieve its long-held goal of an all fifth-generation fighter fleet.

In the meantime, the service has two stealthy fighters—each costing more than $100 million per aircraft—that cannot effectively share data with the fleet (or each other) without compromising the very stealthiness that drove up their cost.

U.S. Air Force Chief of Staff Gen. Mark Welsh challenged the service and industry to begin looking at a so-called “fifth-to-fourth” capability during his annual Air Force Association speech in February. This refers to transferring data collected by the F-22 and F-35 sensor suites to fourth-generation fighters, the F-15 and possibly F-16, that cannot survive the most complex defensive systems. The operational concept would call for these forward, stealthy fighters to transmit data to forces outside the threat “bubble” of air defenses, providing them with an up-to-the-minute threat picture. Older fighters could then use Link 16 to proliferate data to other assets, such as intelligence platforms.

At issue, however, is a decades-long haphazard approach to data links. By design, the F-22 was developed to communicate only with other F-22s via the in-flight data link (IFDL). During the Cold War, the Air Force expected to have hundreds of the stealthy, twin-engine fighters operating against the most hostile systems. So communication would be limited but precise.

The single-engine F-35, by contrast, uses the Multi-function Advanced Data Link (MADL) system, which employs a different waveform and retains its low probability of intercept/low probability of detection (LPI/LPD) by using directional antennas and operating over short distances; the F-35 is slated for Air Force operational debut as early as August 2016.

The F-22 can receive on Link 16 and the F-35 can both transmit and receive on the system, but in terms of detection, data delivery via Link 16 is “like turning on a big light bulb in the sky,” an industry source says.

The F-22 issue has already become a hindrance. It was considered for use in the Libya campaign in 2011, but planners were stymied by an inability to deliver data collected by the F-22s back to other forces, according to one industry source, forcing the Air Force’s premier asset to sit on the sidelines. 

It is unclear how the stealthy RQ-180 intelligence-collection platform—slated for operational use as early as next year—could connect with F-22s and F‑35s, if at all. But, ideally, all stealthy aircraft, including the B-2 and future long-range bomber, should communicate as they operate in defended airspace.

The Air Force had planned to equip all aircraft with the F-35 MADL to facilitate fleetwide connectivity, but its cost proved prohibitively high. “The interest is in finding a course of action that provides the capability at a better cost,” says Capt. A.J. Schrag, spokesman for Air Combat Command; officials declined multiple interview requests but eventually provided written answers. The plan seems more focused on fifth-to-fourth and not connecting the stealthy systems.

The service is crafting the Multi-Domain Adaptable Processing System (MAPS) program that appears to be aimed at a gateway capability. The Air Force plans to issue a draft request for proposals (RFP) by the end of the second quarter of fiscal 2015 for what will likely be a pod for fourth-generation fighters, says Col. Anthony Genatempo, program director at the Air Force’s Electronic Systems Center. He hopes to announce competitive awards by the end of fiscal 2015.

In addition to the communications gateway, the service aims to potentially include an infrared search and track sensor (IRST) in the final MAPS hardware, he says. Air Force planners want to spend less than $100 million developing MAPS, though a final cost has yet to be refined. “The biggest part I am trying to keep a cost control on is the development piece,” Genatempo says. Production numbers would be dictated by the available budget.

Requirements recently approved for MAPS, however, are raising questions. Schrag says the need is “for a gateway” to connect the fleet, adding: “We anticipate an enduring requirement for [such] gateways.” But a gateway relies on an aircraft, likely a fighter that is costly to operate, to circle in range outside of air defenses while a stealthy aircraft operates inside them. This could minimize the ability of the gateway aircraft to do its primary mission and would add to the total campaign price. It would connect fifth to fourth-generation assets but offer no direct connection between the two.

As described, MAPS is an incremental step from a quick-reaction Talon Hate gateway, which aims to field four pods in the middle of fiscal 2015 to provide IFDL connectivity from the F-22 to fourth-gen fighters. Boeing is building these pods for use on the F-15C, which it manufactures.

The Talon Hate pods are expected to be about 17 ft. long and 1,800 lb. They will include the IRST (lacking on the F-22), a Multifunctional Information Distribution System (similar to Link 16), a satellite communications capability and air-to-ground link.

Talon Hate is being spearheaded by the Air Force’s Tactical Exploitation of National Capabilities (Tencap) office, a congressionally mandated program designed to field capabilities across various service offices. Tencap also focuses on how to feed data from “national” assets—such as classified satellites and aircraft—to the fleet.

Air Combat Command declined an interview request on Talon Hate but provided some data on the subject. Boeing deferred all questions about the system to the Air Force.

Some question whether a pod tied to a fourth-generation fighter is the best answer for MAPS. Ultimately, stealthy Air Force aircraft could communicate among themselves independent of an external gateway, a capability notionally referred to as an advanced data link. For MAPS, though, “we are talking about a similar capability to Talon Hate in a different fashion—trying to reduce the size, weight and power of the components,” Genatempo says. “It may be a pod, it may be partially in a pod; it may not be in a pod at all.”

MAPS will not facilitate direct communications between the F-22 and F-35. Though Welsh’s challenge was to connect fifth- and fourth-generation assets, some in the service and Congress believe the time is right to develop a comprehensive data link strategy that will address how to connect the F-22, F-35 and other stealthy assets. “I don’t think they know what they want,” says one industry source. “The process that we call requirements has not had the opportunity and the time to digest what they really need.” Changes in the name of MAPS—the “P” now refers to “processing” but once was “podded”—reflect Air Force ambivalence about the project.

Boeing, Northrop Grumman and Lockheed Martin are expected to submit concepts for MAPS. Northrop Grumman has demonstrated a gateway capability through the Jetpack joint capability technology program that is designed to translate F-22 and F-35 messages into Link 16 messages without the use of a pod to distribute to fourth-generation fighters (or forces operating on Link 16).

Lockheed Martin, by contrast, has demonstrated the ability to use a new waveform developed by L-3 Communications called Chameleon for a direct link among F-22s and F-35s without the use of a gateway or pod without revealing the location of the stealthy aircraft. It demonstrated Chameleon during flight trials in December; officials say the waveform can be transmitted via L-band antennas already on both platforms.

 The company used its own research and development funding to develop the system, dubbed Project Missouri. 

The Chameleon waveform transmits on the Link 16 signal and the data is “spread” below the background noise. Only the receiver can “pull it out.” There are also up to 60 countermeasures developed with Chameleon to address jamming or detection.

Lockheed and L-3 have proven point-to-point connectivity and eventually hope to demonstrate a “multimode” Chameleon capability. The operational concept would be for F-22s and F-35s to “talk” using Chameleon and then send data to an F-18, F-16 or the U-2 (which could act as a high-altitude test surrogate to the RQ-180). A single F-35 could also transmit from the rear outside the bubble to other Link 16 assets.

Without a requirement to connect the F-22 and F-35—picking up where the cratered MADL plan left off—the Air Force is focused on connecting with fourth-generation assets only.