Abstract
With their future vision, military planners are leaving no space behind.
“Moon, Mars, and beyond” is how NASA summarizes current U.S. space exploration goals. But the U.S. military is focusing on a neglected swath of space much closer to home. Forty-six years after the launch of the first U.S. space reconnaissance satellite, the Defense Department is developing a new fleet of military aircraft that can operate in the much lower, mostly unexploited area above Earth “near space.”
“There is a gap in not only capability, but also in operating location and medium, that we are not exploiting right now,” says retired Lt. Col. Edward Tomme, a physicist and leading near-space proponent who served at the air force's Space Warfare Center. That gap is near space, the region roughly between 20 kilometers (12 miles) and 100 kilometers (62 miles) above Earth. Above civil airspace and far below orbiting satellites, near-space operations could afford military and intelligence officials a range of new capabilities–including better reconnaissance, missile launch detection, and communications–at a much lower cost than satellites and aircraft, proponents argue. That is, if the future craft, most of which are types of airships, can perform as envisioned in relatively uncharted territory. “You don't have to operate in every possible niche if the benefit of operating in a given niche isn't there,” argues George Lewis, a senior research associate at Cornell University's Peace Studies Program.
Despite heightened interest in the potential of near-space craft, there are inherent limits to their operations. Many experts believe that arming near-space craft is unlikely because of the challenge of lifting heavy armaments so high into the air. It would also be complicated for an airship to maintain its equilibrium after dropping a payload. And while reconnaissance satellites are not fettered by international borders, near-space craft would be required to respect other nations' sovereign airspace during peacetime–just like traditional surveillance aircraft.
Civilian-controlled airspace
Unlike satellites, whose primary missions are typically assigned long before they are blasted into space, military aircraft and unmanned aerial vehicles (UAVs) can be mission-flexible and “responsive.” But because they (or more specifi cally, their onboard sensors and equipment) fly relatively close to the ground, their “footprints” (coverage areas) are smaller than satellites'. Another limitation: Most aircraft and UAVs can loiter above a target for only so long before needing to refuel.
Space
Intelligence satellites, orbiting hundreds of kilometers above Earth, can deeply probe another country's territory without violating its sovereign airspace. But the movement of these satellites is largely determined by orbital mechanics, which can limit their ability to stay over a single area for long periods of time.
Craft of the future?
The largest airship of a handful undergoing testing is Lockheed Martin's prototype High Altitude Airship (depicted below), which is being built under a $149 million Missile Defense Agency contract. The prototype is planned to carry a 500-pound payload (likely some kind of communications or surveillance gear). But scaling up the craft-which will be topped with photovoltaic cells and maneuvered by four large electric-powered propellers-so that an operational payload can be larger will require some advances in materials science to offset the extra weight, according to Lock-heed offi cials.
Other in-development projects include the Advanced High-Altitude Aerobody (top) and the air force's Combat SkySat (right), a free-floating balloon that has no propulsion capability. The balloon carries equipment that is being tested for its ability to extend beyond-line-of-sight military communications. When its mission is complete, it parachutes back to Earth, abandoning the balloon. The craft could be economically attractive; a commercial version of the balloon costs less than $100.
Near space
At 20 kilometers above Earth, a near-space craft would be above most weather and the jet stream, and below the ionosphere, which can refract electromagnetic satellite signals sent from space, affecting accuracy, according to Tomme. Though winds exist at near-space heights, designers envision some of the near-space craft as outfi tted with propellers so they can fly against the wind and hover longer.
Proponents say that near-space craft will be high enough to substantially improve their footprint compared to lower-flying aircraft but still be low enough to capture higher-resolution imagery than satellites. They could also be able to stay airborne for months at a time and be more responsive than typical satellites, needing less time to deploy on a variety of missions; both traits make such craft suitable for tactical operations.
Supplementary Material
To Infinity and Beyond