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The United Launch Alliance canceled the planned launch of an Atlas 5 rocket on Wednesday in Cape Canaveral to fix a problem with the valves on the launch pad, while a SpaceX team a mile and a half south prepared a Falcon 9 rocket for takeoff. Thursday night with a GPS navigation satellite for the US military.
ULA’s launch team cleaned up the Atlas 5 launch attempt on Wednesday just before 6pm EST (2300 GMT) after failed attempts to fix the valve issue, first remotely and then with a team of technicians sent to the platform launch on the Atlas 5 sea.
The Atlas 5 rocket will carry into orbit a classified payload for the National Reconnaissance Office, the US government’s spy satellite agency. The launch is designated NROL-101, and the NRO has not disclosed any details about the payload’s mission, except that it will help the agency in its mission to gather and disseminate information for government intelligence agencies.
ULA started the Atlas 5 countdown late Wednesday morning, powered the rocket, and proceeded with guidance system tests and other checks before loading cryogenic propellants into the launcher before a scheduled 5pm takeoff: 54 EST (2254 GMT).
But the launch team stopped the countdown after an “unexpected system response from remotely operated ground system liquid oxygen valves,” ULA said in a statement.
“The team continues to analyze the system and will protect for our next launch attempt no earlier than November 6,” ULA said.
The next opportunity to launch the Atlas 5 rocket will be on Friday, ULA said. The exact time for Friday’s launch attempt wasn’t announced immediately, but the mission’s launch time moved about four minutes earlier per day. That would put Friday’s launch time around 5:46 PM EST (2246 GMT).
The Atlas 5 was previously scheduled to launch on Tuesday, but ULA returned the rocket to its vertical hangar near the launch pad to replace an environmental control system duct that fed air conditioning to the top-secret NRO payload atop the 206-foot tall (63-meter) vehicle.
Ground crews returned the Atlas 5 to its launch pad late Tuesday in preparation for the launch attempt on Wednesday.
Before the next Atlas 5 launch opportunity, SpaceX plans to launch a Falcon 9 rocket from nearby Pad 40 during a 15-minute window opening at 6:24 PM EST (2324 GMT) on Thursday.
The 229-foot (70-meter) tall Falcon 9 rocket stood on pad 40 on Wednesday in preparation for launch Thursday night. Pad 40 is located approximately one and a half miles (2.5 kilometers) south of the Atlas 5 Launch Pad in Cape Canaveral.
The Falcon 9 rocket is ready to load the US Space Force 3 SV04 GPS navigation satellite, supplying the fleet of positioning and timing stations used by billions of military and civilian users around the world.
SpaceX attempted to launch the GPS satellite on Oct.2, but an engine problem forced the automatic shutdown just two seconds before takeoff.
Engineers investigating the October 2 outage found that two of the rocket’s nine first stage engines had a tendency to fire a split second earlier than expected. Inspections showed that a stuck relief valve in the gas generators of the two engines caused the pressure to rise earlier than expected at startup, and the sensors on the engines detected the problem and stopped the countdown.
SpaceX engineers have identified a masking treatment left inadvertently in two Merlin engines as the cause of the interrupted countdown last month.
“When we looked at the data, we saw that two of the engines attempted to start early and the automatic shutdown prevented it,” said Hans Koenigsmann, SpaceX vice president of flight construction and reliability. “And in doing so, it prevented a possible hard start that could have damaged the engine hardware.”
Merlin engines ignite with the help of an ignition fluid known as TEA-TEB – or triethylaluminium-triethylborane – which emits a bright green flash at the start of the ignition sequence.
“And then we have liquid oxygen, and we have kerosene, or RP-1 as it is called,” Koenigsmann said on a conference call with reporters last week. “And you have to put these liquids in the right order. If you do it in the wrong order, if you happen to throw in the liquid oxygen and the RP-1 and the igniter fluid, then what would happen is we call it a hard start. “
A hard start would make the engine “shake” in most cases, but it could cause damage, Koenigsmann said. “So, in general, you don’t want that. You want a good startup. “
SpaceX sent the Merlin engines back to a test site in central Texas, where inspections revealed a substance that was blocking a line leading to a pressure relief valve in the gas generator on two of the engines.
Koenigsmann said the vent port, which means only one sixteenth of an inch wide, was clogged with a hardened protective paint. He said liquid lacquer – similar to red enamel – is used by a third-party vendor that anodizes aluminum engine components for SpaceX.
The lacquer protects some parts during the anodizing treatment process, but the vendor – which officials have not identified – should remove the material before shipping the components to SpaceX for engine production.
The gas generator on each Merlin engine drives a turbopump that feeds kerosene propellants and liquid oxygen into the main combustion chamber.
SpaceX’s McGregor test site engineers demonstrated that the engines operated normally after removing the blockage from the breather valve. Koenigsmann said the problem was “very subtle, but it can obviously have a negative impact on engine operation”.
“GPS 3-4 mission will still use the same booster as the first launch attempt,” said Walt Lauderdale, director of GPS 3-4 mission at the Space Force and Missile Systems Center. “The two engines that disrupted the launch have been replaced with those confirmed through inspection and pedigree review to have no masking paint residue.”
SpaceX and Space Force officials verified that all nine Merlin engines of the Falcon 9 rocket were ready for flight after a test launch at Pad 40 on Saturday.
In addition to the rocket for the GPS mission, the engine problem has also affected vehicles for a couple of upcoming NASA launches. So far, the problem has only impacted the missions planned for using the new Falcon 9 boosters.
The first operational flight of SpaceX’s Crew Dragon spacecraft is scheduled to take off on November 14 from Kennedy Space Center with three NASA astronauts and a Japanese mission specialist to kick off a six-month expedition to the International Space Station.
SpaceX is replacing two Merlin engines on the Falcon 9 rocket for the Crew Dragon mission that engineers found to suffer from the same initial start-up tendency shown by the rocket engines for the GPS mission. The issue delayed the launch of Crew Dragon from October 31st to November 14th.
Steve Stich, NASA’s commercial crew program manager, said last week that the agency’s engineers want to analyze engine data from the GPS launch before releasing the Crew Dragon for takeoff at the end of the month.
The engine problem also delayed the launch of the US-European Sentinel-6 Michael Freilich oceanographic satellite from Vandenberg Air Force Base in California. That mission was originally supposed to start on November 10, but is now scheduled for November 21.
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Follow Stephen Clark on Twitter: @ StephenClark1.
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