WASHINGTON — Rocketplane Kistler and Space Exploration Technologies (SpaceX), both recipients of NASA funding to develop commercial alternatives to Russian Progress spacecraft for re supplying the international space station, recently passed early but important milestones on their way to separate demonstration flights in 2008.

El Segundo, Calif.-based SpaceX successfully completed a preliminary design review Feb. 8 for the first orbital demonstration of its Falcon 9 rocket and Dragon reusable spacecraft. Two days earlier, Oklahoma City-based Rocketplane Kistler completed a systems requirements review for its K-1 reusable cargo transportation system.

Alan Lindenmoyer, manager of the Commercial Crew and Cargo Program Office at NASA’s Johnson Space Center, Houston, said the companies are making “genuine progress” on the development of their rival systems.

“If these companies can continue this rapid pace, the first demonstration launches are right around the corner,” Lindenmoyer said.

NASA selected SpaceX and Rocketplane Kistler from among a field of six finalists to share $485 million in Commercial Orbital Transportation Services (COTS) funding to help finance their competing space station re supply systems.

SpaceX intends to conduct its critical design review this summer and begin manufacturing the hardware it needs to conduct in September 2008 the first of three orbital demonstrations of its Dragon cargo transport system. Elon Musk, SpaceX’s chief executive, told Space News Feb. 19 the company has built a structural engineering model of the Dragon capsule and manufactured other spacecraft components, including its heat shield support structure and nose cone.

Musk said development of the Falcon 9 rocket is progressing, with assembly of the rocket’s first stage under way and dozens of test firings it its higher thrust Merlin-1C engines already completed. Musk said the first stage should be substantially completed, minus the engines and internal plumbing, by the end of March.

SpaceX also is gearing up to conduct its second demonstration launch of its smaller Falcon 1 rocket around mid March from the company’s private launch facility in the Pacific Ocean’s Kwajalein Atoll. The Falcon 1’s first demonstration launch — conducted March 24, 2006 — was cut short when its engine caught fire soon after the rocket cleared the launch pad. Musk said SpaceX currently does not have permission to use the U.S. Army-run launch range before March 9, but said that could change. “Previously they had said mid to late February was okay but then they ran short of key personnel,” he said.

Rocketplane Kistler also remains busy following its systems requirement review, which established technical specifications for the interface between its K-1 cargo system and the international space station. The company managed to raise $45 million last fall to restart K-1 development and is making good progress toward an undisclosed financial milestone it must reach by May, according to Bob Seto, Rocketplane Kistler’s chief of staff.

Seto also said in a Feb. 21 interview that the company was close to concluding a reimbursable Space Act Agreement with NASA’s Marshall Space Flight Center for use of the Michoud Assembly Facility to build the K-1 rocket and its unmanned cargo module.

Seto said some K-1 hardware is already on site at the New Orleans facility, held in storage since work stopped on the K-1 several years ago. Rockeplane Kistler plans to pay Michoud to bring that hardware out of storage and to start receiving the shipments of hardware it needs to build the rocket. Seto said the company expects to have the first stage of the K-1 assembled by September, followed sometime later by the second stage. Once the full two-stage rocket has been fit-checked and tested, Seto said, the rocket would be partially disassembled and transported by airplane to Australia in time for a mid- to late-2008 launch. Beginning in early 2009, Rocketplane Kistler plans to conduct the first of two demonstration flights to the international space station.

NASA also announced in February that it had signed unfunded Space Act Agreements with Chicago-based PlanetSpace and Reston, Va.-based Transformational Space Corp. to monitor the development of their privately financed cargo delivery systems. The agreements are intended to keep both companies in the loop so that they can better compete for NASA space station re supply contracts when they are put out for bid around 2010.