Falocn 9 first stage ocean landing
A still from a video posted by SpaceX CEO Elon Musk showing the Falcon 9 first stage touching down on the ocean just offshore of the company's Landing Zone 1 site after a problem with the stage's grid fins prevented a normal landing. Credit: Twitter @elonmusk

WASHINGTON — The failure of a Falcon 9 first stage to make its planned landing after a Dec. 5 launch shouldn’t affect plans for upcoming launches, a SpaceX executive said.

The Falcon 9 first stage used on the launch of a Dragon cargo spacecraft to the International Space Station was intended to land at the company’s Landing Zone 1 at Cape Canaveral, several kilometers to the south of Space Launch Complex 40, where the rocket lifted off.

However, the booster suffered a problem with the grid fins on the first stage, used to control the vehicle during its descent. The stage, at one point spinning rapidly, ended up touching down on the surface of the ocean a few kilometers offshore. The booster toppled over but remained afloat, and SpaceX was sending out boats to tow the stage back to the harbor at neighboring Port Canaveral.

Tracking shot of Falcon water landing pic.twitter.com/6Hv2aZhLjM

— Elon Musk (@elonmusk) December 5, 2018

Elon Musk, the chief executive of SpaceX, said in a series of tweets that a hydraulic pump used for the grid fins malfunctioned, which prevented them from working properly and leading to the stage spinning up. “Some landing systems are not redundant, as landing is considered ground safety critical, but not mission critical,” he wrote.

Hans Koenigsmann, vice president of build and flight reliability, offered a similar explanation at a post-launch briefing at NASA’s Kennedy Space Center. The stage, he noted, continued to work even after tipping over into the water, going through a standard post-landing safing sequence and transmitting data.

“It looks like what happened is some malfunction with the grid fins,” he said. “The important part here is that we have a safety function on board that makes sure that the vehicle does not go on land until everything’s okay, and that worked perfectly.”

The booster targets a point just offshore, he explained, shifting to the landing pad on the coast closer to touchdown. “Even if it is on land it avoids buildings. It knows where buildings are, so it’s pretty smart in that aspect,” he said of the landing system on the booster. “The vehicle kept well away from anything where it could pose even the slightest risk to population or property, so public safety was well protected here.”

The booster is equipped with an autonomous flight safety system, but that was disabled as planned prior to when the booster started to spin up. Koenigsmann said the flight termination system is turned off when the booster no longer poses a threat to the public.

A solution to the problem, Koenigsmann said, could involve redundancy by adding a backup hydraulic pump system, something Musk also suggested, but he said the company needs to study the problem more before making any decisions. “I think it’s too early to say” how it can best be fixed, he said. “I think we need to actually investigate that first and figure out what actually was wrong and what is the smartest solution.”

Koenigsmann anticipated no delays to SpaceX’s next missions. The company’s next launch, of the first GPS 3 satellite for the U.S. Air Force, is scheduled for no earlier than Dec. 18, followed by the launch of the final 10 Iridium Next satellites from Vandenberg Air Force Base in California no earlier than Dec. 30.

“I don’t think this has any impact on GPS 3,” he said. That Falcon 9, he noted, won’t attempt a landing, since it needs the booster performance that would be reserved for a landing to carry out the mission.

He also didn’t expect any effect on the final Iridium launch, although he suggested that launch may slip until early January for other reasons. “I do not anticipate any impact on that schedule here,” he said. “We have enough time between now and then to bring in corrective actions and to make sure that we land that booster safely.” That mission will feature a droneship landing, like several previous Iridium launches.

Koenigsmann also revealed at the briefing that the rocket’s upper stage, which successfully placed the Dragon cargo spacecraft in orbit, used redesigned composite-overwrapped pressure vessels (COPVs) used to store helium to pressurize the stage’s propellant tanks. SpaceX redesigned those COPVs after a September 2016 pad explosion in order to meet NASA safety requirements for future commercial crew missions.

NASA requires SpaceX to perform at least seven launches with the redesigned COPVs before the agency will allow its astronauts to fly on the vehicle. Koenigsmann said he believed this was the second launch to use the redesigned COPVs, after the launch of the Es’hail-2 communications satellite Nov. 15.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...