The United Launch Alliance launched an Atlas 5 rocket into Cape Canaveral on Wednesday to fix a problem with the valves on the launch pad, while the SpaceX team prepared a Falcon 9 rocket a mile and a half south. Thursday evening with the GPS navigation satellite for the U.S. military.

Attempts to fix the valve problem failed and the ELA (2300 GMT) ULA launch team scrubbed at 6pm on Wednesday, first remotely and then sent a team of technicians to the Atlas 5’s beach launch pad.

The Atlas 5 rocket will be launched into a classified payload orbit at the National Reconnaissance Office, the U.S. government’s spy satellite agency. NROL-101 has been designated for the launch and has not disclosed any specific details about the NRO payload mission, which will enable the agency to collect and disseminate information for government intelligence agencies.

The ULA launched the Atlas 5 countdown on Wednesday morning, strengthened the rocket and conducted guidance system checks and other check outs before loading the cryogenic propellants into the launcher at 5:54 pm EST (2254 GMT)

“The launch team stopped the countdown clock after an unexpected system reaction from the remotely commanded ground system liquid oxygen valves,” the UAE said in a statement.

“The team is continuing to analyze the system and will save it for our next launch attempt before November 6,” the UAE said.

The ULA said the next opportunity to launch the Atlas 5 rocket would be on Friday. The exact time for Friday’s launch attempt was not immediately announced, but the mission ‘s launch time was moved four minutes earlier each day. It will make its launch time on Friday at 5:46 pm EST (2246 GMT).

The launch of the Atlas 5 was scheduled for Tuesday, but the ULA rocket returned to a vertical hanger near its launch pad, replacing the environmental control system with a conditioned air-fed (meter) vehicle mounted on a secret NRO payload 206 feet (63) above.

The ground crew returned to the Atlas 5 launch pad late Tuesday in preparation for the launch attempt.

SpaceXX plans to launch a Falcon 9 rocket from the nearby Pad 40 during a 15 – minute window opening at 6:24 pm EST (2324 GMT) on Thursday, ahead of the next Atlas 5 launch.

The 229-foot (70 m) Falcon 9 rocket was spotted on Pad 40 on Wednesday evening in preparation for launch. Pad 40 is located 1.5 miles (2.5 km) south of the Atlas 5 launch pad in Cape Canaveral.

The Falcon 9 rocket is equipped to lift the GPS3SV01 navigation satellite for the U.S. space force, filling the number of positioning and timing stations used by millions of military and civilian users worldwide.

On October 2, SpaceX attempted to launch a GPS satellite, but the engine malfunction forced Liftoff to make an automatic stop two seconds earlier.

Engineers investigating the October 2 abortion found that two of the rocket’s first nine engines had a tendency to burn a split second earlier than expected. The relief valve check on the gas generators of both engines caused the pressure to increase faster than designed at startup, and the sensors in the engines detected the problem and stopped the countdown.

SpaceX Engineers A masking treatment was identified Two Merlin engines are left unattended due to a countdown that stopped last month.

“When we checked the data, we found that two engines had tried to start earlier, and the auto shutdown prevented it,” said Hans Koenigman, vice president of build and flight reliability at SpaceX. “In doing so, it prevented a harsh start that could damage the engine hardware.”

Merlin’s engines are powered by an igniter fluid known as TEA-TEB – or triethylalumium-triethylborene – which gives off a bright green flash at the start.

“Then we have liquid oxygen, which we call kerosene or RP-1,” Koenigsman told a news conference last week. “You need to present these fluids in the correct order. If you do this in the wrong order, and you’m throwing out liquid oxygen, RP-1 and igniter liquid, we’m going to call it a tough start to what happens. ”

A rough start will “bother” the engine in most cases, but will cause damage, Koenigsman said. “It simply came to our notice then. You need a good startup. ”

The SpaceX Merlin engines were shipped to a test site in Central Texas, where two engines were found to be blocking a line leading to the pressure relief valve in the gas generator.

Koenigman said a strict masking lacquer blocked the vent port, which means one-sixteenth of an inch wide. Liquid lacquer, similar to red nail polish, is used by a third-party vendor to anodize aluminum engine components for space space.

Lacquer protects some parts during the anodizing treatment process, but the vendor – not identified by officials – must remove the material before sending the components to SpaceX for engine construction.

The gas generator in each Merlin engine directs a turbopamp feeding kerosene and liquid oxygen propellants to the main combustion chamber.

Engineers at SpaceX’s McGregor test site proved that the engines performed normally after the blockage was removed from the vent valve. Koenigman said the problem was very subtle but could adversely affect engine performance.

“The GPS 3-4 mission will continue to use the same booster as the first launch attempt,” said Walt Lauderdale, GPS 3-4 mission director at the Space Force’s Space and Missile Systems Center. The replacement of the two engines that caused the launch suspension was confirmed by the absence of masking lacquer, which was confirmed by inspection and pedigree review. ”

SpaceX and Space Force officials said all nine Merlin engines on the Falcon 9 rocket were ready for flight after a test firing on the Pad 40 on Saturday.

In addition to the rocket for the GPS mission, the engine problem has also affected a couple of upcoming NASA launch vehicles. So far, the problem has only affected missions that intend to use the new Falcon 9 boosters.

SpaceX’s Crew Dragon spacecraft’s first flight begins on November 14 with three NASA astronauts and a Japanese mission spacecraft from the Kennedy Space Center, marking the half – year expedition to the International Space Station.

The SpaceXX replaces two Merlin engines on the Falcon 9 rocket as a crew dragon mission, and engineers have been found to be struggling with the same early startup trend that the rocket engines displayed for the GPS mission. The Crew Dragon launch issue was delayed from October 31 to November 14.

NASA’s Commercial Crew Program Manager Steve Stitch said last week that the agency’s engineers want to analyze engine data from the GPS launch before clearing the crew dragon for the liftoff later this month.

US-European Sentinel-6 Michael Friedrich oceanographic satellite delayed from launching from Vandenberg Air Force Base in California. That mission was originally scheduled to explode on November 10, but has now decided to launch on November 21.

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