Latest generation of military airships to use solar electric power
The North American Aerospace Defense Command has joined forces with the U.S. Army and other agencies to develop the 21st-century High Altitude Airship to help defend U.S. airspace, control its borders, and possibly provide global surveillance capability to military theater commanders.
by J.R. Wilson
Peterson AFB, Colo. — The North American Aerospace Defense Command (NORAD) has joined forces with the U.S. Army and other agencies to develop the 21st-century High Altitude Airship to help defend U.S. airspace, control its borders, and possibly provide global surveillance capability to military theater commanders.
"It's an old idea with new technology applied," explains U.S. Navy Cmdr. Pat Lyons, chief of ISR and NORAD J-5 Directorate. "This airship is unmanned, untethered, and electric powered. We expect it to be composed of solar cells, a fuel cell, and electrolyzer for nighttime operations."
The new airship's command-and-control links most likely will involve satellite communications channels. All of these technologies will probably enable the airship to remain on station for as long as one year, Lyons says.
The airship will be electrically powered — possibly using a hydrogen fuel cell — with DC brushless motors and propellers as the likely propulsion system, although the final design will be up to the contractor; Lyons says there are several other possible concepts for program managers to consider. That includes the number of motors, which also would determine the number of propellers.
"The concepts we've seen show speeds up to 100 knots for the objective airship," Lyons explains. "The winds at 70,000 feet are fairly benign; you're above the weather and the jet stream, but occasionally, depending on where you are, they can get up to 100 knots, building for 24 hours, peaking for a day, then diminishing for a day. With a 100-knot airspeed, the airship can remain geostationary," Lyons says.
A variety of sensors are being considered for the airship's Advanced Concept Technology Demonstration (ACTD), including a small communications relay. In operation, the vehicle could be used to enable communications 600 or more miles apart, including over a mountain. Currently, ground troops with handheld communications must post a relay unit on a water tower or other tall structure to avoid losing contact in the field.
For an operational system, NORAD is interested in different radars, but with an equipment pod Lyons describes as "the size of a very large room," the airship could handle almost any sensor. In addition, sensor designers will be able to take advantage of the massive surface of the airbag itself for locating antennas, cameras, or other devices.
The pod is to be of the same material as the airbag, not a rigid metal structure, which Lyons says is one of the challenges. It probably would be maintained at about half an atmosphere to maintain a standard environment, so the pressure and temperature are not changing constantly.
"We're trying to match today's requirements with future capabilities," Lyons says. "The technologies we're using are off-the-shelf, as are the materials and solar cells, but we are still helping the technology base (with a new application and market). Some of the components also have space applications. The challenge is a huge integration issue. To take a very thin solar film cell and integrate it with this airship's bag material is a significant challenge."
NORAD, which is located at Peterson Air Force Base, Colo., will be the operational manager, with Army as the lead service. The U.S. Space and Missile Defense Command in Huntsville, Ala., will be the executing agent, while Army Space Command in Colorado Springs, Colo. will be the user unit.
Military planners are coordinating the effort with the U.S. Navy, mostly in terms of payload, but the Navy is not a key player in the airship development — at least not yet. The same is true of other agencies, such as the U.S. Coast Guard and U.S. Customs Service, as well as interest and support across a broad range of non-military agencies. Other nations, such as Japan and Germany, also are exploring the concept.
"We've estimated the cost of the project, but don't want to advertise that because we will be asking for industry proposals. You do have to separate the cost of the vehicle from the payload, which is more variable," Lyons says. Program officials say they hope to have the new airship flying by Spring 2004. The first flights of the airship "could be just in and out of the hangar and up to a low altitude before taking it up to altitude for a few days, then back," he says.
"We will fly for six months, then we have two years of sustainment," Lyons continues. "The residual airship can be used as a test bed for sensors, for future airship development, and helps lead to an acquisition path, if we desire."
Air Force Gen. Ralph Eberhart, NORAD commander-in-chief, recently told a news conference in Colorado Springs that a successful prototype could lead to delivery of two more airships by 2005. "Theoretically," he predicts, "you could start fielding an architecture by 2010."
The goal of the airship's ACTD is to determine engineering feasibility for a 500-foot long, 150-foot-wide helium-filled airship that could operate at 70,000 feet (roughly the same altitude as the U2 and Global Hawk). The payload requirement is 4,000 pounds and on-station requirement from days to weeks.
Experts estimate that a fleet of 10 such airships could improve NORAD's monitoring capability against air and maritime threats to U.S. territory.
"The concepts I've seen look like traditional airships, because it still needs to be an aerodynamic, lighter-than-air vehicle operating within the atmosphere," Lyons says. "The real difference will be the technology in the airbag. Different vendors have different ideas on the specific material, but it probably will be Kevlar-like rather than a cloth, but very strong and lightweight, much more so than traditional airships. This is not a blimp, which in military terms has tended to be low altitude and tethered. And at 70,000 feet, the line-of-sight to the horizon is a radius of 325 miles, which would be extremely beneficial to whatever sensors are onboard, be they radars or communications."
Technicians will monitor and sometimes control the airship and its sensors from the ground round the clock. The ground system is included in the vendor's design, with specifications currently under development.
NORAD officials are proposing that the ground station be a permanent facility at a remote location in Colorado Springs, which would handle the airship no matter where it is deployed.
"Also inviting to the folks in theater is the logistics trail — there is none," Lyons points out. "Everything else remains in Colorado Springs. They don't have to take care of it, refuel it, or repair it. To them, it is just like a satellite. It will become an asset. Even if it is used only for communications relay, anyone in theater needing that help would request it, just as they now do for satellites, but these are a lot more maneuverable than satellites, which have limited fuel for maneuvering."
It also has another similarity to a satellite; even when not in use, it probably will remain airborne, so sending it to a new theater would only be a retasking effort, with the airship flying itself to its new destination rather than being deflated, crated, shipped, re-inflated, and launched.
"During ACTD we are required to develop potential operational applications, architectures, all of which will vary depending on payload. So it is very hard at this point to put a number on how many airships we might build. The potential payoff, if this concept works, is worth all the risk. If this really is a very, very low geosynch satellite, it is very appealing, from a cost standpoint. We know users are always fighting over SATCOM, so even if it only becomes a communications relay, the benefit is huge."
The airship concept was under consideration before 9/11, but is now under consideration for homeland defense applications, as well. "We have coordinated with the Office of Homeland Security. The applications are endless and they have expressed considerable interest," Lyons says.