As Virgin Galactic prepares to roll out its suborbital passenger spaceship, U.S. military officials seeking low-cost, responsive access to space are studying the company's latest exotic concept to deliver small satellites to orbit.

File photo of WhiteKnightTwo in flight. Credit: Virgin Galactic

Peter Wegner, director of the Pentagon's Operationally Responsive Space program, said the private firm's conceptual air-launched rocket design is "attractive" for potential military missions.

Virgin Galactic will unveil its suborbital SpaceShipTwo spacecraft Monday in a ceremony in Mojave, Calif.

Part of the Virgin Group led by Richard Branson, the space tourism company will use SpaceShipTwo to ferry paying passengers to the edge of space more than 60 miles above Earth.

Virgin Galactic's plans for a small satellite launcher were given a significant boost in July, when Abu Dhabi's Aabar Investments took an equity stake in the company.

Aabar is investing $280 million and taking a 32 percent stake in Virgin Galactic's holding company. Aabar may also commit up to $110 million more to fund Virgin Galactic's satellite launch vehicle, dubbed LauncherOne.

The ORS program has so far contracted for launches with the missile-based Minotaur 1 and 4 rockets and the privately-developed Falcon 1 booster.

"The other area that we're starting to look at from the launch aspect is the commercial entrepreneurial space industry," Wegner said. "Virgin Galactic has announced they're going to develop a small launch vehicle capability off the WhiteKnightTwo, and we're very interested in that and watching what comes from that."

The WhiteKnightTwo is the mothership for Virgin Galactic's SpaceShipTwo passenger spacecraft. Like SpaceShipTwo, the LauncherOne rocket would be fired from the WhiteKnightTwo at an altitude of about 50,000 feet.

LauncherOne reportedly would lift 110-pound satellites to orbit for less than $2 million. The first flight of the rocket is still several years away.

"They talked about launch costs for a 50-kilogram (110-pound) payload down in the single digit millions, so that's really attractive," Wegner said.

The ORS program is tasked with fielding small satellites to test inexpensive space technologies with on-demand capabilities for military commanders on the battlefield.

Officials hope to eventually put small satellites on call for rapid launch as needed.

Low-cost launch providers are imperative to achieve such objectives. An enhanced version of SpaceX's Falcon 1 can haul more than 2,200 pounds to orbit for $10.5 million, according to company documents.

Launch prices for the Minotaur 1 and 4 rockets, mostly derived from stockpiled missile hardware, are not readily available.

Wegner said there are more than 100 Minotaur 1 motor stacks and parts for approximately 44 Minotaur 4 rockets.