Hard start, tough finish
by Jeff Foust
|“It would take extraordinarily bad luck not to walk away with at least the Level 1 prize,” John Carmack, chief of Armadillo Aerospace, said early in the day Saturday.|
However, Mod failed to lift off on its first flight attempt Saturday morning, remaining on the pad; Armadillo scrubbed the launch shortly thereafter. Carmack said later in the morning, after he and the rest of the Armadillo team returned to their staging area on the flightline, that the igniter had become clogged with some sort of foreign particles, preventing it from working properly, possibly simply from dirt or other debris that got lodged into the igniter during the 12-hour drive from Dallas to New Mexico. With the igniter now thoroughly cleaned, Armadillo was ready for another flight Saturday afternoon.
Saturday afternoon’s attempt got off to a good start, as Mod performed the first leg of the Level 1 flight flawlessly, landing near the center of the pad after being in the air for a little over 90 seconds. Now, though, the process of preparing the vehicle was taking longer than expected, for reasons that weren’t immediately clear to the audience, and Armadillo was in danger of running out of time to make the flight within the allotted window.
Carmack later explained that the team found that the igniter was clogged again. “Out there in the field we were trying to fix it, and all we would up being able to do is file down a paper clip and we jammed it in there and routed it around the igniter orifice,” he said. “We were afraid that any time you were messing with the igniter there, that’s the opportunity for something to go wrong on startup.”
And something did go wrong on startup: a “hard start” caused by an excess of fuel in the chamber at ignition. “We thought it was over right there, but the engine was still burning,” Carmack said, so he decided to fly the return leg as quickly as possible, getting Mod to the other pad and hovering just above it, hoping the engine would last for the 90 seconds needed to complete the flight and win the prize. However, with just seven seconds to go “we lost half the nozzle and flipped over,” he said. Mod landed on its side, but since the engine shut down and the vehicle was already low to the ground, it sustained little damage beyond its engine, which had to be replaced using one in a spare Mod vehicle Armadillo brought to New Mexico.
By late Saturday fuel contamination was the leading explanation for the igniter clogging issue; Carmack said they were using locally-provided ethanol rather than bringing their own. Overnight the team planned to clean out all the fuel systems to purge it of any contamination. Another Lunar Lander Challenge team at the event, Unreasonable Rocket, also offered one of their filters to help contain any contamination, “an unbelievable show of good sportsmanship here,” Carmack said. Those measures, he said, led him to conclude that they still had a 70-percent chance of winning Level 1 on Sunday, down from 90 percent at the beginning of the day.
Armadillo’s third attempt at winning the Level 1 prize came Sunday morning, and like the attempt Saturday afternoon, appeared to start off well: Mod made the first leg of the trip without incident, landing on the other pad and quickly turning around the vehicle for the return leg. However, upon ignition, the engine suffered another hard start, and this time instead of continuing to fly, Armadillo performed a powered abort and brought the vehicle back down on the pad after being in the air for only a few seconds.
|“We were afraid that any time you were messing with the igniter there, that’s the opportunity for something to go wrong on startup,” said Carmack about repair efforts on the pad Saturday afternoon.|
This time it didn’t appear that contamination was an issue, but instead an unexpected consequence of a slight design change. Phil Eaton, another member of the Armadillo team, said late Sunday morning that Armadillo made a slight change in the design of the injector, using a different O-ring. This new design, he said, didn’t appear to allow fuel vapors to dissipate as rapidly after use as the old design. Since Armadillo was trying to turn around the vehicle quickly, it’s possible that there were still vapors present when the engine was ignited for the return flight, causing the hard start. That theory would also explain why the hard starts were taking place on the return legs of the flights and not the initial ones. As a precaution, Eaton said that they would purge the injector of fuel during preparations for the return flight on their final attempt Sunday afternoon.
At the same time, Armadillo was lobbying for a possible fifth flight window late Sunday to make one attempt at the Level 2 challenge. They could not use the additional window for Level 1, since the challenge rules allow for no more than four flight attempts per level, but they could use it to fly Pixel. A fifth opportunity would have to wait until the airshow that was sharing the day with the X Prize Cup wound down at around 5 pm. With sunset at 6:30 pm, that meant that flight operations would likely be taking place at night, which wasn’t a problem for Armadillo but required approvals from the Air Force and the FAA.
First, though, was the final attempt by Mod to win the Level 1 prize. The vehicle was carried out to the pad, fueled, and readied for launch. At launch, though, the audience watching the vehicle on Jumbotrons saw what appeared to be a fireball and sustained fire. Mod, using an engine cannibalized from Pixel, had suffered yet another hard start, this one more violent than any of the previous ones. Despite the catastrophic appearance on the TV screens, the vehicle was not seriously damaged, nor anyone injured, but the engine was destroyed, wrecking Armadillo’s shot at the Level 1 prize. Shortly thereafter, Carmack notified X Prize officials that he did not plan to use the additional late-day window, if offered, bringing the 2007 Lunar Lander Challenge to an unfortunate end.
Later in the day Eaton explained that the fire was fed by liquid oxygen (LOX): while the fuel valves had closed off, the force of the hard start had yanked the cables to the LOX valves before they could close fully; that kept the flow of LOX going, feeding the fire. Beyond the engine, there was little additional damage to the vehicle, mostly involving cabling and other minor components. “This could fly again in a week,” he said.
What remains a mystery, though, is why the hard starts are occurring. The same engine design had flown 30 times without similar problems, making it all the more puzzling that the engine would then suffer three hard starts in five attempts in a two-day period. “I can’t believe we were lucky 30 times,” said Russ Blink, another Armadillo team member.
One complicating factor is that, while Armadillo had flown Lunar Lander Challenge-class test flights in the past, they had not done so under the same time and competition pressures as were present at the Cup. Carmack noted that the early start time in the morning, and the presence of thousands of spectators (the Air Force estimated 85,000 people attended over the two days) “added some stress” to their efforts. “It’s not practice makes perfect,” advised Ken Davidian of NASA’s Centennial Challenges program, “it’s perfect practice makes perfect.”
“This weekend, we’ve had more problems than we’ve had in the last six months,” Neil Milburn, also of Armadillo, said in an official statement released Sunday night by the X Prize Foundation recapping the event. “We know what went wrong, but not why.”
Armadillo’s failure to win the cup, after coming so close on Saturday and with the high expectations going into the event, was clearly a major disappointment not only to the team and its supporters, but to the broader emerging NewSpace industry as well. A victory would have given Armadillo and the industry a positive boost at a time when it clearly could have used one, given recent setbacks like the fatal accident in Mojave in July and Rocketplane Kistler’s loss of its NASA COTS award. A win could also have benefited NASA’s Centennial Challenge program by giving it added visibility, and also boosted the X Prize Cup, which suffered the loss of its title sponsor, mobile phone retailer Wirefly, not long before this year’s event.
|“The Cup has given us an opportunity to show what we can do in front of multiple audiences, which we would not have been able to do otherwise,” said Milburn. “We know we’ll be back again, and we’ll nail it next time.”|
However, both Armadillo and the X Prize Foundation put the best possible face on the event. “I think this was a success,” said Brett Alexander, the foundation’s executive director for space and the X Prize Cup, during a press conference after Armadillo’s final flight attempt. “This shows what entrepreneurs can do,” he added, referring to Armadillo’s two successful flights and third nearly-successful flight, as well as the resourcefulness of the team to keep trying after multiple problems. The displays by other Lunar Lander Challenge teams who, while not yet ready to fly, brought their flight hardware, “showed that there are a lot of people out there trying to do this, really taking risks, doing things differently,” he added.
This was the second year in a row that Armadillo was the only competitor for the prize; eight other teams registered for the competition but all had dropped out by the time of the Cup. The progress those other teams are making—two or three of them got close and one got “really close” to competing this year, according to Alexander—coupled with the fact that the $2 million in prize money remains available, should mean that multiple teams will be able to compete next year. The prize money, he said, “is an incentive for those still pushing, and it’s an incentive for us to hold the Cup and have a great event and have multiple teams compete.”
Armadillo expects to be back again next year, hoping the third year is the charm to winning the prize. “Each time we fly we do a little better, learn a little bit more,” said Eaton. Added Milburn: “The Cup has given us an opportunity to show what we can do in front of multiple audiences, which we would not have been able to do otherwise. We know we’ll be back again, and we’ll nail it next time.”