Sunday, February 19, 2017

SpaceX Postpones Capsule Launch Seconds Before Liftoff: Company blames problem with the propulsion system of the rocket’s second stage; Mission rescheduled for Sunday

The Wall Street Journal 
Updated February 18, 2017 6:32 p.m. ET

Space Exploration Technologies Corp. scrubbed the launch of an unmanned capsule destined for the international space station on Saturday, roughly 10 seconds before scheduled liftoff from a historic Florida pad.

The abort, which company officials attributed to a problem with the propulsion system of the rocket’s second stage, came after an uneventful countdown without any holds or technical issues.

Minutes after the countdown was halted, SpaceX issued a statement indicating that the launch team was “standing down to take a closer look at an engine actuator on the second stage.”

SpaceX said it would attempt to redo the launch Sunday.

It wasn’t immediately clear what type of warning launch officials received about engine-nozzle controls on the upper stage to prompt Saturday’s scrub.

Shortly before lifting off, the Falcon 9 rocket switches to a computerized launch-control sequence that automatically halts the countdown and alerts launch officials about unusual sensor readings or other problems.

Saturday’s launch was supposed to be the company’s second mission in 2017, following the January launch of 10 commercial satellites

that marked a return to flight in the wake of a September 2016 Falcon 9 explosion during routine fueling on the ground.

The cause of that accident was determined to be unexpected ignition stemming from swift, high-pressure loading of helium into vessels immersed in the rocket’s supercooled liquid oxygen tank for the second stage. SpaceX has said it opted to change fueling procedures to eliminate the hazard, but also plans longer-term design changes.

Saturday’s scheduled launch initially was intended to carry a commercial payload partly because National Aeronautics and Space Administration officials wanted to wait before launching a cargo mission from the newly-refurbished pad at Florida’s Kennedy Space Center. But in recent weeks, NASA officials decided to move up the cargo mission in light of the level of supplies and experiments on board the orbiting international laboratory.

The list of experiments headed into orbit includes an effort to see how certain bacteria behave and mutate in space, technology to study ozone levels in the atmosphere and a medical experiment to better understand how human tissue can regenerate in microgravity.

Sunday’s flight plan also will call for Dragon to rendezvous with the space station two days after launch, but the rocket’s main stage is intended to return to Earth and land vertically just miles from the launchpad.

After the thousands of people who gathered near Kennedy Space Center to observe the daytime launch had dispersed, entrepreneur Elon Musk, SpaceX’s founder, chairman and chief rocket designer, shed some light on what happened in a series of messages posted on his Twitter account.

Mr. Musk said engineers wanted to investigate the “slightly odd” position of hydraulic controls on an upper-stage engine. He said there was a 99% chance the system would have corrected itself, “but that 1% chance isn’t worth rolling the dice. Better to wait a day.”

Mr. Musk also said SpaceX experts needed “to make sure that it isn’t symptomatic of a more significant upstream” problem. The company’s chief indicated the problem “is not obviously related” to a tiny helium leak in the second stage that was detected on Friday, but he added it is “also not out of the question.”

Original article can be found here:

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