Playing the waiting (and winning) game
by Jeff Foust
|“At least we don’t have to worry about grassfires,” quipped Carmack, referring to the pouring rain.|
That, however, was predicated on the weather cooperating, and Saturday morning that looked doubtful. A steady rain started Saturday morning, forcing Armadillo to put its plans to make its attempt late in the morning on hold. “Nothing much we can do about the weather,” quipped Armadillo’s Neil Milburn during a mid-morning safety briefing inside the hangar. “Somebody with a higher pay grade than me is taking control of that one.” Worse, the forecast was no better for Sunday.
“At least we don’t have to worry about grassfires,” added team leader John Carmack.
So while visitors—about a hundred or so, primarily friends and family of the team along with a few other curious people—waited out the rain by exploring the Armadillo hangar, where a number of Armadillo’s other vehicles were on display, the team kept a close eye on the weather radar. They initially hoped that the line of rain, drifting to the northwest, would clear in an hour or so after the briefing, but the rain lingered into the afternoon as moisture filled in the back edge of the storm.
Finally, at around 3 pm Saturday afternoon, the rain subsided. The team sprang into action, heading out to the pads they built between the airport’s two runways. As the team set up Scorpius on the pad, those who remained after the long rain delay wandered out into a muddy field outside the hangar, up to a perimeter 1,500 feet (450 meters) from the pads—a distance considerably closer than the public had been allowed at previous Lunar Lander Challenge flights in New Mexico. Then, a little over an hour after departing the hangar, Scorpius lifted off.
One key difference between Level One of the LLC, which Armadillo won first place in last October, and Level Two is that the vehicle must remain aloft for at least 180 seconds. Carmack explained the flight profile in the morning briefing. “It’s going to lift off and go to maybe three or four meters to make sure things are swinging around wildly. I’ll then take it up to ten meters and burn off 20 seconds” to lighten the vehicle’s propellant load. The vehicle would then fly to 55 meters before translating over 60 meters to be above the other pad. “Then I’ll back down to about ten meters, still well off the pad, and them I’m going to run out the clock to 140 seconds. With 40 seconds to go I’m going to drop it down to only a couple of meters above the pad, and that’s when I’m going to try and basically sit there and burn the X off the center of the pad.” At 180 seconds the vehicle would go into an auto-land mode and touch down on the pad.
That appeared to be the flight profile Scorpius flew on its first leg, from the flat pad to a pad with simulated lunar terrain (the other key difference between the two levels of the LLC). As expected, for much of the 180 seconds the vehicle simply hovered above one pad or the other. When it touched down, the crowd at the safety perimeter applauded and cheered.
There was, though a bit of drama with the flight. One of the vehicle’s roll control thrusters wasn’t working, causing the vehicle to slowly roll during the flight. It didn’t prevent a safe and accurate landing, but did pose a bit of a challenge to Carmack during the descent. “It rotated completely around, which made it backwards for me,” he said in a post-flight interview. “When I was looking at the final terminal guidance on there, I was actually making it going the wrong way” initially because of that 180-degree rotation.
|Towards the end of each flight, the vehicle would hver just anobe the pad “and basically sit there and burn the X off the center of the pad,” Carmack explained.|
After landing the Armadillo team found the problem with the roll control thruster and Carmack handled it with a software fix. That ended up creating another problem that became evident when the vehicle’s engine failed to ignite for the return trip. “I had actually introduced another error in there; I accidentally killed the igniter,” he said. He had to go back and correct the problem in the code and recompile it, all while the fully-fueled vehicle was sitting on the pad and the clock was running.
“It was extremely stressful because when when you’re making the changes at that point, you’re boiling off three pounds of LOX [liquid oxygen] a minute,” Carmack said. The vehicle has sufficient margin to allow some loss of LOX before launch, but had the problem taken more than a few minutes to fix, they could have potentially run out of LOX before completing the required 180 seconds of flight. “If we been waiting 15 minutes, we would have been marginal on the landing. We might have been sitting over the pad, sputter out of LOX, and drop the last couple of feet.”
But the code fix was made in just a few minutes, and Scorpius flew an incident-free return trip, landing on its pad with over a half-hour to spare in the 135-minute flight window. Once the vehicle had been hoisted back onto its trailer and the judges confirmed that the flight was a valid Level 2 attempt, Carmack communicated the news to the elated crowd over his walkie-talkie: “We won!”
That assessment is, strictly speaking, premature. Under the new rules for the Lunar Lander Challenge this year, the once-a-year competition previously held in New Mexico (as part of the X PRIZE Cup, which has been discontinued) has been replaced with a window of flight opportunities that started in July and runs through the end of October. Rather than travel to a central venue, teams can compete at the site of their choice, in Armadillo’s case its home airport.
Armadillo had welcomed that rule change, allowing them fly when they’re ready and in a familiar setting. “It’s hugely better to do this with the home field,” Carmack said. Armadillo had spend days leading up to the event practicing their landings with another vehicle. “It would have been much more stressful approaching a rocky, cratered pad for the very first time coming in for the contest.”
However, Armadillo isn’t the only team planning a Level 2 flight this year. Two other teams, Masten Space Systems and Unreasonable Rocket, have filed plans with the X PRIZE Foundation, who runs the competition for NASA, to make Level 2 attempts next month in California. With the deadline for registering for the 2009 competition closing on Tuesday, one or more additional teams may yet register. With landing accuracy the tiebreaker if more than one team makes a Level 2 flight, it’s possible in a worst-case scenario that Armadillo could come away empty-handed if two other teams also make successful flights and land closer to the center of the pad than Armadillo.
That, however, is an unlikely scenario. No other team has yet performed a successful Level 1 flight, let alone a Level 2 one, and Armadillo’s past experience—falling short of Level 1 in 2006 and 2007 and barely getting off the pad for Level 2 last year—suggests that making a successful flight is harder than it appears. And even if a team does perform a successful Level 2 flight this year, they’ll have a challenge beating Armadillo’s accuracy, which the X PRIZE Foundation reported as “below one meter” in a blog post after Saturday’s flight. All that suggests that Armadillo will likely be getting a check of some kind, if not the $1-million Level 2 first prize award, later this year.
|“I’m perhaps maybe not so overwhelmed as people might expect,” Carmack said afterwards. “We’ve done so many flights of this—we were practically flying this every day—we felt, ‘Okay, it’s going to work.’”|
While Armadillo waits to see how the rest of the competition plays out, they plan to press ahead with vehicle development. Carmack said after the flights that once they modify their FAA waiver that permits these flights in the coming weeks, Armadillo plans to press ahead with “boosted hops”, where the vehicle accelerates off the pad to higher altitudes, using the same flat pad they used for LLC flights. “We have a slow and steady incremental program here, but we expect to be able to work to up to 6,000-foot (1,800-meter) altitude flights here, and we will learn an immense amount,” he said. “We will probably work all the way up to attempting an engine restart.”
Saturday, though, the team and it supporters were celebrating the accomplishment, if not yet their victory, although Carmack was a little subdued. “We think it’s well-earned,” Carmack said after the flights. “I’m perhaps maybe not so overwhelmed as people might expect. We’ve done so many flights of this—we were practically flying this every day—we felt, ‘Okay, it’s going to work.’”
That might sound a bit overconfident, but it’s one rooted in years of work, including several past failed efforts to win LLC prizes. It’s also a reminder to the other teams competing in the competition, and other companies trying to develop suborbital and orbital spacecraft, that none of this will come easy, but over time and with enough effort it can come.