SpaceX, the company started by PayPal co-founder and tech entrepreneur Elon Musk, is stepping up its pursuit of a reusable rocket with a suborbital craft named "Grasshopper."
Based on the company's Falcon rocket, the 106-foot tall launcher will have an extra motor to practice cushioning its return trip to Earth, with the aim of landing on the launch pad, a draft environmental assessment issued by the Federal Aviation Administration shows.
From a launch site in McGregor, Texas, Grasshopper will fly as high as about 11,500 feet above ground, and as often as 70 times a year. In addition to a Falcon 9 first stage and a Merlin engine, Grasshopper would be outfitted with four steel landing legs and a steel support structure, the FAA document shows.
The Grasshopper could hold as much as 6,900 gallons of propellant, but most would serve as ballast.
The California-based company is seeking government clearance to build a launch pad at its 650-acre rocket test facility in McGregor for flying the Grasshopper. The program is expected to last three years.
SpaceX declined to disclose details of the Grasshopper program, but rather than developing a new suborbital launch vehicle for sale, Grasshopper most likely is a testbed for SpaceX to chase the elusive holy grail of rocket scientists — reusable launchers.
Musk has repeatedly said rocket reusability is the key to making huge cuts in the cost of space launches, which currently carry a price tag of about $10,000 per pound to orbit.
The company has flown its Falcon 9 rocket twice, and plans to launch a third time before the end of the year on a practice cargo run to the International Space Station. Both Falcon 9s splashed back into the Pacific Ocean after the successful flights and were recovered, but could not be reused.
"There's a reason that no one has invented a fully reusable rocket before. It's super damn hard," Musk said after a speech last month at an industry technical conference in San Diego.
When asked about SpaceX's progress on reusable rockets, Musk replied, "Well, so far, it has sucked ... but we have learned a lot."
The Falcon 9's last flight sent a Dragon capsule into orbit. It was recovered in good condition and ready to fly again with just new parachutes. Adding that level of shielding to the rocket, however, would make it so heavy it couldn't deliver the capsule into orbit, Musk said.
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"The real tricky thing here is essentially constructing a suit of armor that is just exactly tailored to the forces (the rocket) is going to need to resist on re-entry, and those forces are higher than we anticipated," he said.
Among the tricks in SpaceX's design team's bag is restarting the Falcon 9 engines to slow the rate of descent, which would cushion its landing.
But that would mean the rocket would have to carry more propellant.
"It's a tough trade on propellant versus dry mass," Musk said. "We've got something that on paper closes and we'll see if that turns out to be reality as well."
Although NASA's recently retired space shuttles flew repeatedly in orbit, each required a standing army of thousands to refurbish before flight. The Air Force is calling for its next generation of heavy-lift rockets to be reusable as well. The military figures it can cut launch costs by at least 50 percent based on a flight rate of eight missions per year. The savings comes from reusing the first-stage booster which would be designed to land itself on a runway near the launch site.
The Grasshopper would join a menagerie of SpaceX-developed spacecraft being tested at McGregor, including Merlin rocket engines and the Falcon 9 expendable launch vehicles.
The FAA's draft environmental assessment of SpaceX's Grasshopper can be found here.
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