The Japanese space agency is pushing for a domestic human spaceflight capability, proposing modifications to the country's International Space Station cargo delivery system to carry astronauts into orbit by 2025.

Artist's concept of the HTV spacecraft and a returnable cargo capsule. The proposed HTV-R spacecraft could launch by 2018, proving key technologies for a Japanese human spaceflight capability. Credit: JAXA
 
If approved by the Japanese government, the craft's development would follow a crawl-walk-run approach. Japan has already demonstrated its H-2 Transfer Vehicle can haul cargo and experiments to the space station, and next up could be developing a return capsule to bring equipment from the outpost back to Earth.

The Japan Aerospace Exploration Agency plans to fly seven HTVs in support of the space station through 2016. Two Japanese cargo freighters successfully flew in 2009 and 2011, and five more are due to launch at a rate of one per year.

JAXA's leadership is openly pitching the HTV as the foundation of a manned spacecraft, which could fly Japanese crews as soon as 2025. But the idea requires approval by Japanese lawmakers and the endorsement of the government agency in charge of JAXA.

Japanese spending priorities have shifted in the wake of the costly Tohoku earthquake and tsunami in March 2011, straining JAXA's budget in the process.

Keiji Tachikawa, president of JAXA, said developing a recoverable capsule for the HTV would be the next technological leap needed to make a Japanese manned spaceship a reality.

"If we can make the HTV retrievable, then we expect that we will be able to turn it into a manned spacecraft, too," Tachikawa said in an interview posted on JAXA's website. "However, the decision on whether or not Japan goes ahead with this rests with the Japanese government. So before we move in that direction, the government has to give us the go-ahead."

Japan is targeting fiscal year 2017, which ends in March 2018 in Japan, for the first flight of the HTV-R craft, which will bring back up to 3,500 pounds of cargo in a pressurized capsule on each mission.

Diagram of the proposed HTV-R spacecraft. Credit: JAXA
 
The HTV flights help cover Japan's share of the space station's operating costs. Instead of making financial payments to NASA, the station's program integrator, JAXA and the European Space Agency barter to meet their commitments by providing transportation services with the HTV and Europe's Automated Transfer Vehicle.

With the space station's life extension until at least 2020, the program's partners will owe more operating costs, and Japan plans to continue the HTV delivery service, but with the capability to return hardware to Earth.

JAXA has not disclosed the total cost of designing and building the HTV-R spacecraft.

The HTV now disposes of the station's garbage after leaving the outpost, plunging to a controlled fiery crash over the Pacific Ocean.

JAXA foresees a capsule-shaped lifting body for the HTV-R's return craft, enabling precision landing zones for the vehicle to parachute into the ocean.

If Japan proceeds with a crewed spaceship, engineers would need to human-rate the country's H-2B rocket or develop a new launcher. Officials are already investigating safety upgrades to the H-2B's hydrogen-fueled LE-7A engine, and a manned rocket will require an escape system yet to be developed.

"Personally, I think that if we continue to cooperate with the international community in space, our partners will ask Japan, a country with a highly developed space program, to help build an infrastructure for manned space transport," Tachikawa said. "This is another reason why I believe that we should develop a made-in-Japan manned spacecraft.

Europe and NASA are considering an ESA-supplied service module for the U.S. Orion Multi-Purpose Crew Vehicle to cover the agency's share of space station costs.

ESA's proposal for a retrievable cargo ship, called the ARV, did not gain enough support among European member states or NASA, leaving the space agency searching for a new barter element.