SpaceX makes another leap toward rocket reusability
Sen—SpaceX has been making progress toward its goal of reusable rockets in recent flights of its upgraded Falcon 9 rocket and Falcon 9 test rig, codenamed Grasshopper.
On October 7 Grasshopper completed its highest leap to date, reaching an altitude of 744 metres, hovering and then returning to land on its launchpad. The test flight lasted 78.8 seconds and was conducted at the company's rocket development facility in McGregor, Texas.
Grasshopper is a prototype for Vertical Takeoff Vertical Landing (VTVL) technology that will be fitted to future Falcon rockets to enable them to return to their launchpad for a vertical landing, reducing launch costs and turnaround time for the next launch.
The pioneering US rocket and spaceship builder, founded by entrepreneur Elon Musk only 11 years ago, has already established its technology credentials having completed two commercial resupply missions to the International Space Station (ISS) using its unmanned Dragon spacecraft.
As well as developing a crewed version of Dragon, the company is determined to build reusable rockets to reduce launch costs and increase frequency.
Some of the reusable technology components have already been fitted to the company's Falcon 9 rocket. The updated Falcon 9 lifted off on September 29 from SpaceX's launchpad at Vandenberg Air Force Base. The launcher put four satellites into orbit whilst demonstrating several new technologies. The upgraded Falcon 9's first stage was powered by nine Merline 1D engines, generating nearly twice as much thrust compared to the previous Merlin 1C engines. A new stage separation system reduced the number of connection points from 12 to 3, and the vehicle also flew with a stronger heat shield designed to allow the rocket to re-enter Earth’s atmosphere and ultimately land propulsively. Although excessive roll occurred as the first stage returned to Earth, the company put out a confident assessment of the demonstration flight, stating:
"The [first] stage ended up spinning to a degree that was greater than we could control with the gas thrusters on board and ultimately we hit the water relatively hard. However, SpaceX recovered portions of the stage and now, along with the Grasshopper tests, we believe we have all the pieces to achieve a full recovery of the boost stage."
The updated Falcon 9 did not fly with landing legs, which the company believe could have helped stabilize the stage "like fins would on an aircraft."
"Between this flight & Grasshopper tests, I think we now have all the pieces of the puzzle to bring the rocket back home" announced SpaceX founder Elon Musk on Twitter.
Grasshopper, which consists of a Falcon 9 first stage, a Merlin-1D engine, four steel and aluminium landing legs and a steel support structure, had its maiden flight on September 21, 2012, hopping about 2 metres off the ground.
The second test came in November 2012 when it flew to 5.4 metres (17.7 feet) and hovered briefly before landing as planned.
During its third test flight, held on December 17 last year, Grasshopper reached 40 metres (131 feet) during a 29 second test flight. After hovering, the rocket successfully landed on its legs. A 6 foot tall dummy cowboy was strapped to the Grasshopper to put the rocket's size -- about 110 feet tall -- into perspective.
On its fourth test flight on March 7 this year the test rig reached 80.1 metres (262.8 feet), hovering for about 34 seconds before landing safely. In April the vehicle reached 820 feet, tripling the height achieved in March.
On June 14, the Grasshopper flew 325 m (1066 feet) before smoothly landing back on the launchpad. For the first time in this test, Grasshopper made use of its full navigation sensor suite with the F9-R closed loop control flight algorithms to accomplish a precise landing.
On August 13 Grasshopper demonstrated direction change, flying to a 250m altitude with a 100m lateral manoeuvre before returning to the centre of its launchpad.
October's flight was the last scheduled test for the Grasshopper. The next test of the technology will be low altitude tests of the Falcon 9 Reusable (F9R) development vehicle in Texas followed by high altitude testing in New Mexico.