The U.S. Air Force has kick-started a major study on quick-to-launch boosters capable of enhancing the nation's warfighting abilities, such as dropping munitions from space onto enemy targets here on Earth. The analysis is also delving into payloads that begin their on-orbit duties far more rapidly than satellites lofted today.

Called the Operationally Responsive Spacelift Analysis of Alternatives, Air Force-led study teams are looking into space planes, air-launched boosters, fully reusable, as well as toss-away or partly-reusable spacelifters.

Given a Pentagon go-ahead and funding, the Air Force could first fly a multi-staged system by 2014. In addition, a low-cost expendable upper stage booster and an orbital transfer vehicle capable of handling spacecraft servicing would be developed.

However, while technologies may find utility in both civil and military camps, the Air Force must be geared for far more rapid access to space than NASA is pursuing, Stewart said.

"As some point we have to take our technologies that have synergy, and then divide off and complete our final project. So I doubt, seriously, we'll be building the same vehicle," Stewart said.

"We have very specific requirements of responsive lift in order to be responsive to crisis," Stewart said. "The goal is hours to days versus weeks to months in order to have an asset on orbit."

Stewart said that a single-stage-to-orbit space plane is not in the cards to meet a 2014 milestone. Rather, a multi-stage vehicle appears more promising.

"We are looking at more of a pragmatic or more practical approach versus trying to reach so hard in the near-term for the technology," Stewart told SPACE.com. A fleet of spacelifter vehicles will be needed, capable of launching from multiple locations. But as for the total bill, that is yet to be determined, she added.

Also underway, Stewart said, is a spacelifter payload study. A set of "notional" payloads -- built for rapid launch in surge mode, as well as quickly put in service once in space -- have been identified for further assessment.

Speculative payloads include:

• Common Aero Vehicle (CAV) munitions that can be deployed from a military space plane to hit deeply buried, hard, and mobile targets on Earth.
• A navigation payload to augment or replenish an out-of-service Global Positioning System satellite.
• An electro-optics payload designed for high-resolution surveillance.
• A special-purpose payload built to take out an enemy satellite, or protect a spacecraft by moving it out of harms way.

Stewart said that additional looks into these representative payloads are meant to help size spacelifter vehicles. Also, being weighed is how best to make payloads serviceable. The value of telerobotic refueling in orbit, changing out sensors and other equipment is under consideration, she said.

Details of the Operationally Responsive Spacelift Analysis of Alternatives are being presented during an upcoming Responsive Space Conference and Workshop. The program is being held April 1-3 in Redondo Beach, California, and is sponsored by the Los Angeles Section and the Space Systems Technical Committee of the American Institute of Aeronautics and Astronautics.

"In my mind, recent events have clearly demonstrated the need for a level of responsiveness far greater than now exists in space," said James Wertz, President of Microcosm, Inc. of El Segundo, California. He is also general chair of the April workshop.

As current events demonstrate, Wertz said, new technology has made the coalition war effort "responsive and flexible" and that is key to modern military strategy.

"Clearly, space is critical to much of the war effort. But unless it becomes dramatically more 'responsive and flexible,' it will become much less relevant," Wertz told SPACE.com.

A second example of this is the Columbia tragedy, Wertz added. "It now seems fairly certain that no dramatic action could have been taken that would have averted this particular disaster. But that may not be the case with future problems. A responsive launch capability, not necessarily to rescue the crew but perhaps to bring what is needed to resolve the problem, could make future spaceflight significantly safer."

Wertz said that a business example of this same issue is evident by the Iridium experience - a constellation of commercial satellites that went bankrupt.

"The Iridium system worked very well, but simply got overcome by events because of the long time required to develop and field it. This is not a criticism of Motorola. They built the system in record time for a major space asset. Unfortunately, space systems just aren't built and launched responsively in today's world," Wertz said.

"In my view," Wertz concluded, "these are the challenges that we need to address: How do we make space dramatically more responsive and what can we do with it if we succeed?"