Keeping with its mantra of fly, fix and fly again, SpaceX says its engineers have resolved an engine valve problem that kept one of its Falcon 9 boosters from successfully touching down on a barge in the Atlantic Ocean in April, ahead of another landing attempt planned after a launch from Cape Canaveral scheduled for Sunday.
The landing tests are classified by SpaceX as purely experimental maneuvers, but they have garnered wide attention from launch industry competitors and space enthusiasts around the world.
SpaceX says the experiments should lead to the reusability of Falcon 9 booster stages, an achievement that engineers say will cut launch costs and open up access to space to more companies, governments and universities with lean budgets.
Sunday’s launch — set for 10:21 a.m. EDT (1421 GMT) — will be the third time SpaceX has tried to recover a Falcon 9 first stage on a specially-outfitted ocean-going barge. Landing attempts in January and April got close, but the rockets landed too hard — and at tilted angles — and disintegrated in fireballs.
On both attempts, the rocket’s first stage flipped around after separating from the Falcon 9’s upper stage, which continued into orbit with Dragon cargo ships heading for the International Space Station.
The boosters fired three of their nine Merlin first stage engines for two burns — first to guide the booster back toward the landing zone downrange from Cape Canaveral, then to slow down for re-entry into the atmosphere. A third ignition of the rocket’s center engine is supposed to brake for landing.
Engineers blamed the first crash landing in January on insufficient hydraulic fluid for the 14-story booster’s aerodynamic grid fins used to steer the rocket during descent.
In April, the first stage descended toward the landing barge and the rocket fired for its final braking maneuver, but a stuck valve thwarted the touchdown.
“That controlled descent was spectacular, but about 10 seconds before landing, a valve controlling the rocket’s engine power (thrust) temporarily stopped responding to commands as quickly as it should have, ” SpaceX said in a post on its website Thursday. “As a result, it throttled down a few seconds later than commanded, and — with the rocket weighing about 67, 000 lbs and traveling nearly 200 mph at this point — a few seconds can be a very long time.
“With the throttle essentially stuck on ‘high’ and the engine firing longer than it was supposed to, the vehicle temporarily lost control and was unable to recover in time for landing, eventually tipping over, ” SpaceX said.
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