Landing legs to fly aboard SpaceX's next Falcon 9 rocket
BY STEPHEN CLARK
Posted: February 23, 2014
The next Falcon 9 rocket, scheduled to blast off in March on a space station resupply flight, will sport a landing gear to take the next leap in making the commercial launcher reusable, according to SpaceX officials.
When the rocket takes off March 16, engineers will program the first stage to guide itself to a soft splashdown in the Atlantic Ocean, where a recovery team will try to pluck the spent rocket from the sea several hundred miles northeast of Cape Canaveral.
The rocket's second stage will continue into orbit with a Dragon cargo craft heading for the International Space Station.
SpaceX's ultimate objective is to fly the first stage back to a vertical landing near the launch pad, but Musk said Sunday on Twitter that the Falcon 9 will return to water landings until the company can prove "precision control from hypersonic [through] subsonic regimes."
Musk has said a reusable Falcon 9 rocket would slash SpaceX's launch costs. The company's advertised launch prices already undercut domestic and international competitors.
The first stage will carry four landing legs designed to deploy after separation from the Falcon 9's second stage a few minutes after liftoff. Made of carbon fiber with aluminum honeycomb, the legs are stowed along the side of the rocket during launch and extend down and outward for landing, according to information posted on SpaceX's website.
During a September launch from Vandenberg Air Force Base in California, SpaceX retrieved fragments of the Falcon 9 rocket's first stage from the Pacific Ocean. After shutting down its nine Merlin 1D engines and separating from the second stage, the first stage restarted three of its engines in a braking burn to reduce the rocket's velocity during the fall through the atmosphere.
The stage's center engine ignited a few minutes later to further slow the rocket's speed just before splashing into the ocean, but the burn was cut short when the booster's spin starved the engine of fuel. SpaceX blamed centrifugal forces for keeping propellant out of pipes leading to the fuel-starved engine, causing it to switch off prematurely as the rocket hit the water and broke apart.
The September flight, which did not include landing legs, was the first test launch of an upgraded Falcon 9 launcher known as Version 1.1. The Falcon 9 v1.1 features more powerful Merlin engines, stretched propellant tanks, a simplified stage separation system and triple-redundant avionics to improve reliability.
It successfully delivered Canada's Cassiope satellite to orbit for space weather and data relay experiments.
The Falcon 9's two subsequent launches, both carrying commercial telecommunications satellites from Cape Canaveral, did not attempt a fully controlled re-entry profile and splashdown with the first stage.
"Given all the things that would have to go right, the probability of recovering the first stage is low," SpaceX spokesperson Emily Shanklin wrote in an email. "There was maybe a 10 percent chance of recovery on the first flight of v1.1; this time there's maybe a 30 percent to 40 percent chance. Given that, it probably won't work, but we are getting closer."
SpaceX founder Musk has committed to fielding a reusable rocket for a decade.
The first stage of the company's first satellite launcher, the Falcon 1 rocket, was designed to parachute into the ocean and be collected for refurbishment, but the booster was never recovered.
The Falcon 9's planned rocket-assisted landing on the ground would ease the job of readying the first stage and its engines for another launch, avoiding potential contamination by salt water that the space shuttle's solid rocket boosters encountered, according to SpaceX.
Follow Stephen Clark on Twitter: @StephenClark1.