Vehicles operating in a section of the atmosphere known as “near space” might be providing communications services to U.S. government users before the end of the year, according to officials at U.S. Air Force Space Command.

The initial customers could be homeland security officials preparing for disasters that disrupt or destroy local communications infrastructure , as Hurricane Katrina did in 2005, the officials said during an April 3 interview at Schriever Air Force Base in Colorado Springs, Colo.

Space Command issued a draft request for proposals April 20 on the Federal Business Opportunities Web site seeking small, lighter-than-air vehicles that operate in near space, which the Air Force defines as the section of the atmosphere between 19 and 31 kilometers above the Earth’s surface. Such vehicles could dramatically extend the range of UHF and VHF radios already in the field today for voice and low-data-rate communications, according to the notice.

The procurement is a set-aside for companies with no more than 750 employees, and the contracts will have a minimum value of $600,000 and a ceiling of $50 million, according to the notice.

Space Command already is working with one company, Space Data Corp. of Chandler, Ariz., on a near-space system called Combat SkySat that features a communications relay payload. Space Data Corp. conducted 15 flights of hydrogen-filled Combat SkySat balloons from November 2004 through May 2005, according to Lt. Col. Rich Lane, director of demonstration initiatives at Air Force Space Command’s Space Battle Lab.

Combat SkySat balloons also are getting a demonstration in the Air Force’s Joint Expeditionary Forces Experiment 2006, which began April 22 and is intended to examine prototype systems that could be fielded quickly, Lane said.

Near-space vehicles would be launched upwind of a disaster or combat zone and drift slowly over the area, providing four to 12 hours of continuous coverage, depending on wind speeds, Lane said. The coverage period could be extended by launching multiple balloons several hours apart, he said.

Each vehicle would cost roughly $7000, and the unit price could decrease with volume, Lane said.

“It simply changes the line of sight,” Maj. Shawn Bratton, detachment commander of the Air Force’s 111th Space Operations Squadron, said in an article posted April 24 on the Air Force’s official Web site . “The standard ground radio range is roughly 5 to 10 miles, but with Combat SkySat, warfighters can exchange information over more than 600 miles [956 kilometers].”

Near-space vehicles also can overcome buildings, hilly terrain and other obstacles to terrestrial radio communications , Bratton said.

The military is examining a variety of near-space systems, and formed the Joint Near Space Council in 2005 to avoid duplication of effort, Lane said. The council includes representatives from the military services and organizations like Special Operations Command and the U.S. Coast Guard, he said. Its next quarterly meeting is scheduled for June at Naval Air Systems Command at Patuxent River, Md., he added .

The most capable near-space system in development today is the High Altitude Airship, a prototype sensor platform that Lockheed Martin Corp. of Bethesda, Md., is building for the Missile Defense Agency, Lane said. As envisioned, the blimp-like, propeller-driven airship would linger over areas for months at a time to provide missile warning and other functions, and may be demonstrated for the first time around 2008.

However, the future of the High Altitude Airship is in doubt, as the House Armed Services strategic forces subcommittee denied the Pentagon’s entire $40.7 million budget request for the program in 2007.

Initial versions of Combat Skysat and other balloon-based systems would be at the mercy of prevailing winds, but are simple enough that they could be fielded relatively soon, Lane said. That would give the military time to design more sophisticated systems with longer dwell times, he said.

However, Gary Payton, deputy undersecretary of the Air Force for space programs, said the Air Force faces a “long learning curve” when it comes to long-duration near-space vehicles. In addition to wind, there are hazards in the upper atmosphere like ultraviolet rays that could damage a vehicle’s balloon fabric, Payton said in a February interview.

In addition, such vehicles likely would rely on solar arrays for power, and keeping that hardware attached to the balloon as its fabric expands and contracts based on changing temperatures could prove problematic, Payton said. “There are a huge number of unknowns, and I think that is why the Air Force is being prudent about jumping on the [near-space] bandwagon until we learn the ramifications of flying at that altitude,” he said.

Air Force Space Command also is exploring long-duration unmanned aircraft operating at near-space altitudes that would be less vulnerable to some of the hazards associated with balloon platforms, Lane said. These vehicles, which would linger over an area for five to seven days, are ideally suited to surveillance and intelligence gathering, he said.

While these vehicles would resemble unmanned aerial vehicles like the Global Hawk built by Northrop Grumman Corp. of Los Angeles, they would have different requirements such as specially designed power systems for long-duration missions, according to Lt. Col. Kelly Anderson, director of concept development at the Space Battle Lab.

Officials from Boeing Co. of Chicago and AeroVironment Inc. of Monrovia, Calif., have made presentations on such vehicles at recent Joint Near Space Council meetings , Anderson said.

Long-duration unmanned aerial vehicles capable of flying at near-space altitudes likely will be more expensive than those in use today, but the added cost would be offset at least in part because fewer of them would be needed to conduct the same missions, Anderson said.