NASA says October test launch affirms Ares 1 concept
BY STEPHEN CLARK
Posted: December 3, 2009
Managers in charge of the Ares 1-X test flight told reporters on Thursday the $445 million October mission confirmed NASA's concept for the Ares 1 crew launch vehicle will work as designed.
Ess cautioned the data was preliminary, but officials provided remarkable detail on key measurements collected throughout the flight.
Data graphs show the 327-foot-tall rocket flew as predicted, with little dispersions from data from prelaunch simulations.
"The key point is that the green line (flight data) and the blue line (model data) are almost right on top of each other. In general, agreement is extremely good," said Marshall Smith, chief of the Ares 1-X systems engineering and integration office.
"The algorithms that we're testing for Ares 1 worked perfectly and flawlessly," Smith said.
The Ares 1 rocket, part of NASA's Constellation program to return humans to the moon, could fall victim to a review of the space agency's human spaceflight plans by the Obama administration.
A committee of space industry experts found the Constellation program was underfunded and unsustainable. The board, chaired by former industry executive Norman Augustine, recommended NASA consider using commercial solutions for crew transport to low Earth orbit after the space shuttle is retired.
But leaders directed NASA to continue with the program until the agency receives new direction.
Ess said the Ares 1-X flight showed engineers two major concerns, roll torque and thrust oscillation, may not be serious factors in the design of the Ares 1.
Roll torque is an induced spinning motion by the solid fuel-burning first stage motor and thrust oscillation is a phenomenon that can trigger intense and damaging vibrations.
"We converging on roll torque not really being a driver," Ess said. "Same thing with thrust oscillation."
A roll control system borrowed from the military's Peacekeeper missile program guided the slender rocket through a programmed 90-degree roll maneuver shortly after liftoff, but the thruster only briefly fired twice in response to roll torque or aerodynamic loads, according to NASA.
Engineers studied two periods of projected thrust oscillation and found maximum frequencies of 15 hertz and 29 hertz, one-third and one-half the predicted values, respectively.
Launch pad 39B suffered more extensive damage than seen during a typical shuttle launch because Ares 1-X was intentionally tilted away from the structure in a flyaway maneuver designed to spare the upper part of the pad from the fiery hot plume of the rocket.
The flyaway maneuver directed the plume toward lower levels of the pad, causing toxic propellant leaks and other damage. The information will be used in the construction of the Ares 1 mobile launcher and umbilical tower.
Information briefed to media Thursday closely matched what officials said two days after launch, but engineers continue to add more fidelity and details as data continues to analyzed from more than 700 sensors on the rocket.
One glitch that initially clouded the test flight was the failure of two parachutes designed to gently guide the rocket's first stage booster to a soft splashdown in the Atlantic Ocean.
Engineers now say they have identified a possible failure scenario for at least one of the chutes.
"We believe that possibly one of the parachutes may have disreefed or overinflated a little too quickly, which increases the load before the system is designed to take that load," Smith said.
The parachutes are designed to partially open to slow down the descending booster before fully inflating, or disreefing, a few seconds before splashdown.
Hardware in the Salt Water Activation Release, or SWAR, mechanism showed signs of an overload, Smith said.
Eight SWARs are installed on each parachute to transfer loads from the chute to attach points on the top of the first stage. They also help improve the safety of divers recovering the rocket.
The Ares 1-X parachutes, each 150 feet in diameter, are larger and made of a different material than chutes in the recovery systems of space shuttle solid rocket boosters.
With the chute issues, the first stage hit the water at a higher speed and steeper angle than expected, causing denting in the booster casing and a bend along the length of the rocket.
There was also significant cracking in the stage's aft skirt and an auxiliary power unit part was apparently jarred loose and lost during impact, according to Smith.
Other than the parachute failure, engineers found three connectors in the booster's recovery system did not separate as planned and flight damping results that were slightly lower than expected.
The connectors were inside the booster's forward skirt dome that jettisoned to unfurl the main parachutes. Swinging underneath a smaller drogue chute like a pendulum, the rocket could have experienced an off-center pull causing only some of the connectors to separate.
The rocket's damping characteristics were also put under the microscope during the Ares 1-X test. Engineers planned a programmed nozzle deflection to bend the rocket and gauge how long it took for the motion to dampen out.
Data shows the damping was about 20 percent lower than during simulations. Smith said engineers will further study the unexpected damping rate.
The Ares 1-X team plans two more intermediate reports in late January and late February before turning over the data to the Ares 1 rocket designers to incorporate in their work.
"At the end of January, we'll have a much better feel for what the sensors told us," Ess said. "I don't expect us to have any significant changes from what we told you today."
Ares 1-X data was beamed back to communications stations live and simultaneously stored in an on-board data recorder. The first four-and-a-half minutes have been recorded from the storage device and will be released to analysts within days.
Data from the last 80 seconds was not properly recorded to the disk, and engineers are attempting to retrieve pieces of that information. Smith estimated about three-quarters of the corrupted data could successfully be recovered.
"We not super concerned about getting that data, as opposed to the ascent," Smith said.
Ess also addressed studies to develop a new Ares test flight to launch in 2012 or 2013, possibly with a five-segment first stage motor and an operating launch abort system.
The test is unofficially called Ares 1-X Prime and would verify the design of the rocket's first stage and provide a valuable high-altitude demonstration of the abort system that would carry astronauts away from a failing booster.
Decisions on such a test launch are still months away, according to NASA.