Asteroid probe, rocket get nod from Japanese panel
BY STEPHEN CLARK
Posted: August 11, 2010
The board governing Japan's space program last week formally approved a successor to the Hayabusa asteroid explorer and the Epsilon small satellite launch vehicle to continue development.
The government space panel, which has oversight of the Japan Aerospace Exploration Agency, only gave the go-ahead for preliminary design work on Hayabusa 2, a mission projected to cost nearly $200 million.
The commission recommended proceeding with full development of the Epsilon rocket, a new Japanese launcher to send small satellites into orbit beginning in 2013.
The Hayabusa 2 mission would blast off as soon as 2014 and reach a carbon-rich asteroid in 2018 for a touch-and-go approach to collect samples. After spending a few months in the vicinity of the asteroid, the probe would return to Earth in 2020.
The spacecraft's mission would replicate the feat accomplished by Hayabusa, the mission that completed the first round-trip journey to an asteroid in June. During its seven-year journey to and from asteroid Itokawa, Hayabusa suffered major glitches in its sample collection device, propulsion system and reaction wheels.
But the probe released an entry capsule that landed in Australia, possibly with the first microscopic dust grains from the surface of an asteroid.
Hayabusa 2 would incorporate improvements to the faulty systems that plagued its predecessor, but the craft would rely on the same fundamental design to slash costs.
Junichiro Kawaguchi, Hayabusa's project manager, said a "good indication was shown by the government" in negotiations and hearings over the past few weeks.
"Precisely speaking, still we need some more time to make it actually appropriated. But most opinions say the mission shall be performed," Kawaguchi wrote in an e-mail to Spaceflight Now.
Kawaguchi is managing the Hayabusa 2 proposal team, but he will relinquish leadership once the mission enters full development.
Hayabusa 2 would target an asteroid named 1999 JU3, a C-type body with a diameter of about 1 kilometer, or 0.6 miles. Scientists say C-type asteroids are the unspoiled relics of the early solar system, which was dominated by small bodies as the planets coalesced.
Itokawa, the destination for Hayabusa, is a stony rubble pile asteroid that formed from separate objects fusing together over time.
Japan is moving forward with Hayabusa 2 after the Marco Polo mission, a joint asteroid probe with Europe, was not selected by an international panel of scientific advisors earlier this year.
The budget decisions for JAXA are being considered as an economic stimulus, according to Kawaguchi.
"We've already spent three years on the preliminary design," Morita said. "This is the actual start of the development. This is a good time for us."
Now finished with preliminary development, engineers are focusing on a critical design review planned about 18 months from now.
The Epsilon rocket will launch about once per year with small technology demonstration and scientific missions, starting with a craft named Sprint-A that will place a telescope into a 300-mile-high Earth orbit to observe Venus, Mars and Jupiter.
The three-stage launcher is designed to lift more than 2,600 pounds to low Earth orbit. The M-5 rocket could haul about 4,000 pounds to a similar trajectory.
Morita, who is also the former manager of the M-5 rocket program, said it will cost approximately $200 million to finish developing the Epsilon rocket, but it's much less expensive than the M-5, which carried a $70 million price for each launch. He would not discuss the Epsilon's cost per flight.
"For example, the M-5 first stage rocket motor was very expensive because it uses a big chamber and is in two segments. We had to assemble the two segments at the launch site," Morita said.
Engineers will also design the Epsilon with more autonomy, making the rocket less labor-intensive and reducing the workforce required for launches.
"The launching performance of the M-5 was the best in the world for a solid rocket at the time, but operations took a lot of time and labor," Morita said in an interview with Spaceflight Now. "As far as the Epsilon rocket, the sales point is its responsiveness. This is far beyond the M-5's capacity, so we can extend the solid rocket technology in Japan, not only in the launching capacity but also in operations."
JAXA's goal is to have an inexpensive rocket ready to answer the needs of scientists and engineers building low-cost satellites.
Epsilon designers are reusing technology from the M-5 and H-2A rockets to cut costs. The Epsilon's first stage is based on the H-2A's solid rocket booster, while the second and third stages will use heritage solid-fueled motors from the M-5's upper stages.
According to Morita, JAXA has still not decided where to launch the new rocket.
Another option is Japan's main launching base at the Tanegashima Space Center, the home of the much larger H-2A and H-2B rockets. One of two active launch pads there could be outfitted for the Epsilon rocket, or a vacant Tanegashima launch pad used by the N-1 and N-2 rockets more than 20 years ago could also host Epsilon missions, according to Morita.
"One of the most remarkable features of the Epsilon rocket is its mobility, so the vehicle can be launched by Uchinoura as well as by Tanegashima, and the government has not yet decided its launch site," Morita said.
Morita said high construction costs might limit the Epsilon to just one launch site.
IHI Aerospace Co. is the Epsilon rocket's prime contractor. The company builds the H-2A solid rocket boosters and previously held the lead contract for the M-5 rocket.
"The small rocket will be required for small satellite missions," Morita said. "The H-2A is too big to support small satellites. We need a small launcher with the responsiveness to support small satellites."