GPS IIF-3 = Delta-IV-M+(4,2) - 4.10.12 16:10 ЛМВ -Canaveral

[Salo]

http://www.spacenews.com/launch/121012-shelton-investigation-delta-anomaly.html

Fri, 12 October, 2012
Shelton Orders Investigation of Delta 4 Anomaly
By Titus Ledbetter III

WASHINGTON — U.S. Air Force Gen. William Shelton, commander of Air Force Space Command, has ordered an "accident investigation board" to review an upper-stage thrust anomaly that occurred during the successful Oct. 4 launch of a GPS satellite aboard a United Launch Alliance (ULA) Delta 4 rocket, the service announced Oct. 11.

Meanwhile, ULA said Oct. 5 that the scheduled Oct. 25 launch of the Air Force's X-37B reusable military spaceplane is on hold while ULA and upper-stage maker Pratt & Whitney Rocketdyne investigate the cause of the anomaly. The robotic X-37B is slated to launch atop ULA's Atlas 5 rocket, whose RL-10 upper stage is similar to the one used on the Delta 4.

Denver-based ULA, a Boeing-Lockheed Martin joint venture, said telemetry showed lower-than-expected performance of the Delta 4's RL-10 upper stage during the GPS 2F launch from Cape Canaveral Air Force Station, Fla. The rocket's guidance system and flight computers compensated for the lower thrust, delivering the Boeing-built navigation satellite to its proper orbit with the help of reserve fuel, ULA said.

ULA and the Air Force must determine the cause of the glitch before they can proceed with the launch of the X-37B on what will be that program's third flight to date, the ULA press release said. Details of the so-called Orbital Test Vehicle-3 mission are classified.

Pratt & Whitney Rocketdyne of Canoga Park, Calif., builds different versions of the RL-10 for the Delta 4 and Atlas 5, the workhorse launch vehicles of the U.S. Department of Defense.

The results of the Air Force-ordered investigation will be presented to Shelton before being made public, the service said.

[instml]

http://www.glonass-ianc.rsa.ru/GPS/

Новый спутник GPS IIF-3 работает в системе. В GPS теперь 31 КА, по 5 в пяти плоскостях, и 6 в пятой плоскости.

[Salo]

http://www.spaceflightnow.com/delta/d361/investigation.html

Investigation finds Delta 4 rocket engine issue
BY JUSTIN RAY
SPACEFLIGHT NOW
Posted: December 9, 2012

The Delta 4 rocket's cryogenic upper stage engine persevered through a fuel leak and the resulting low-thrust condition by autonomously engaging techniques that kept the mission on track to successfully launch a Global Positioning System satellite in October.


Animation of the upper stage firing. Credit: United Launch Alliance
 
The dramatic ascent began at 8:10 a.m. EDT Oct. 4 fr om Cape Canaveral's Complex 37, roaring into the morning sky on the combined power of the RS-68 main engine and twin solid motors.

It was a flight being conducted by United Launch Alliance for the U.S. Air Force to deliver a next-generation GPS navigation satellite into orbit where it would replace an aging, 19-year-old craft.

But four-and-a-half minutes into the launch, after the first stage had shut down and separated, the trouble began as the RL10B-2 engine on the upper stage extended its nozzle and fired to life.

When the powerplant was igniting and reached its peak chamber pressure, a leak started above the narrow throat portion of the thrust chamber, setting off a series of ramifications that would endure over the next three hours as the vehicle made its climb to the GPS constellation.

The mission sequence planned three burns of the upper stage, initially reaching a low-altitude parking orbit, then a highly elliptical transfer orbit and eventually achieving a circular orbit in line with the GPS network 11,000 nautical miles up.

Throughout those burns, however, the engine was feeling the effects of the leak by producing less thrust than expected, firing longer than planned to compensate and having to adjust its trajectory.

"With the fuel leak, the thrust was lower than nominal, and the Delta 4 closed loop guidance system measured this in real time and revised the trajectory that was being flown and also the burn durations to achieve the required orbital conditions and other requirements," said Jim Sponnick, ULA vice president of mission operations.

"Also, the fuel leak in the thrust chamber resulted in a slight offset to thrust direction fr om the engine. The launch vehicle control system adapted to this by adjusting the engine gimbal angle to compensate for the slight offset in the thrust."

Despite all of that, the rocket's resilience allowed the launch to achieve success in the face of adversity, hauling the 3,400-pound GPS satellite exactly where the cargo wanted to go.

"We were later informed by our GPS customer that this was the most accurate placement of the three GPS 2F spacecraft that have been launched, which enabled a short on-orbit checkout period following the launch," Sponnick said.

Using the margins in the rocket's fuel supply and calling upon the flight software to handle the off-nominal situation, the rocket kept clawing onward on each of its three burns.

"The three burn durations ranged from 20 to 36 seconds longer than nominal predictions. Various parameters are targeted for each burn, and the flight results generally did meet our expectations. The final orbit was quite precise," Sponnick said.

The first burn was supposed to last nearly 8 minutes to put the vehicle into a low-altitude parking orbit. The rocket coasted over the central Atlantic for about 9 minutes before restarting the engine to run for a scheduled three-minute firing to inject itself into an elliptical orbit with a high point near the GPS constellation's altitude 11,000 nautical miles, while leaving the low point around 130 nautical miles.


Animation of the upper stage firing. Credit: United Launch Alliance
 
On the ground, mission managers realized they had a problem on their hands but were not quite sure how the ascent was going to turn out. A worst-case scenario was the upper stage running out of fuel before getting to the proper orbit, casting fears of a "bad day."

The rocket was in the midst of a quiet, three-hour coast as the rocket motor traveled away from Earth toward the high-mark of the orbit for one final firing.

"While we knew in real-time about the lower than expected engine performance, we were not able in the lim ited time to perform detailed analyses that would be needed to accurately quantify the propellant leak. As a result, we had rough analyses ranging from predictions of a nominal final orbit to some conservative worst-case analyses showing that there might not be adequate performance to achieve the required final orbit," Sponnick recalls.

The third burn ignition time arrived and the RL10 again restarted, giving all of the propulsion needed to fully circularize the orbit by raising the low point up to the GPS network's altitude.

"The thrust in the first burn was approximately 5 percent below nominal, and it stepped down several percent more in each of the second and third burns. During each of the three burns, the thrust levels were constant," said Sponnick.

Three-and-a-half hours after leaving the launch pad, Delta released the satellite cargo into an approximate 11,047-nautical-mile perch tilted 55 degrees to the equator, marking a full mission success.

"It was a relief to the team that there was plenty of propellant margin and the final orbit was accurately achieved," Sponnick says.

And, in fact, there was "pretty substantial margins" still left in the tank when the mission was completed. Analysis now shows more than 1,000 pounds of propellant remaining, which would have enabled approximately 30 seconds of additional burn time, is necessary, Sponnick says.

Fed with supercold liquid hydrogen and liquid oxygen, the RL10B-2 is the latest in a long line of upper stage engines dating back a half-century. The original version of the RL10 debuted successfully on an Atlas rocket in 1963 and has been part of Centaur for more than 200 space missions.

The RL10 has dispatched robotic expeditions to every planet in our solar system, plus multiple missions to the moon and countless military spacecraft and commercial communications satellites in orbits around Earth.

This latest RL10 variant was introduced in 1998 as part of Boeing's Delta 3 program, which served as a stepping-stone to the Delta 4 rocket and development of its cryogenic upper stage.

The engine has been fired in space 23 times to date.

Its specs include a nominal thrust of 24,750 pounds, mass of 664 pounds, an overall length of 13.6 feet, including 7 feet just for the nozzle extension and a specific impulse of 465.5 seconds.


An upper stage of the Delta 4 rocket. Credit: NASA
 
Coupling the Delta 4 with the relatively light-weight GPS 2F satellite provided a bit greater margin for the launch than other rocket and payload combinations.

"There are missions that would not have reached their prescribed orbit with the kind of performance degradation that occurred in the last launch," Sponnick says. "That illustrates why we must thoroughly investigate and implement corrective actions for an anomaly such as this."

Investigators used extensive analysis and the reconstruction of flight data to find the leak location and when it began. But the ongoing inquiry continues to work through the credible "candidate causes" to determine why the leak happened.

The team had 2,000 measurements from the GPS launch that were analyzed in great detail and technicians performed tests on production engines to aid the investigation and crossover assessments. More than 500 "candidate causes" have been thoroughly assessed in the process of zeroing in on a small number of credible physical causes.

Pratt & Whitney Rocketdyne produces the RL10B-2 engine and the RL10A-4 powerplant used by the Centaur upper stages on Atlas 5 rockets. Although the two engines have their differences, they do share commonality through the evolution of the venerable RL10.

The list of "candidate causes" of the leak includes some pertaining only to the Delta 4 version and others that have "crossover" implications that could touch Atlas as well. Those potential causes common to both vehicles have been put to the test against the Atlas engine that will power Tuesday's launch of the X-37B spaceplane, known as Orbital Test Vehicle Flight 3, and officials Friday formally cleared that RL10A-4 for flight.

"For each cause that has potential crossover to the RL10A-4 engine, comprehensive flight clearance assessments have been performed for the OTV 3 mission," said Sponnick. "Wh ere applicable, specific mitigating actions have been implemented -- such as detailed visual and borescope inspections of the engine and launch vehicle systems."

The Atlas 5 rocket will be wheeled to the launch pad Monday for a targeted blastoff Tuesday at 1:03 p.m. EST, weather permitting. See our Mission Status Center.

It will get the Atlas family back in action, which paused its manifest in light of the RL10 situation and delayed the X-37B mission from the targeted late October launch.

The Delta 4 rocket had planned mid-January for its next mission will carry the Wideband Global SATCOM 5 military communications satellite to orbit. That vehicle's engine has undergone the same visual inspections that the X-37B launcher did, and some additional work on the Delta is being evaluated before it is cleared for flight. A new launch date is pending.

Atlas plans to launch NASA's Tracking and Data Relay Satellite K on Jan. 29 from Cape Canaveral and return to its original schedule with the Feb. 11 flight from California's Vandenberg Air Force Base carrying the next Landsat remote-sensing spacecraft.

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http://forum.nasaspaceflight.com/index.php?topic=31289.msg1050143#msg1050143

ULA presser:

United Launch Alliance Clears WGS-5 Mission for May 22 Launch

Cape Canaveral Air Force Station, Fla., (May 10, 2013) – United Launch Alliance (ULA) has cleared the launch of the WGS-5 mission, after a thorough flight clearance process was executed following a flight data anomaly that occurred on the Global Positioning System (GPS) IIF-3 launch on Oct. 4, 2012.

            "This will be the first Delta IV launch following the low engine performance that was identified on the successful Global Positioning System (GPS) IIF-3 launch last October," said Jim Sponnick, ULA vice president, Mission Operations. "Although the GPS IIF-3 spacecraft was accurately placed into the required orbit, ULA, Pratt & Whitney Rocketdyne (PWR) and our U.S. Air Force teammates embarked on an investigation to determine why the upper stage engine performance was lower than expected. ULA completed a flight clearance assessment recently for the WGS-5 mission and our Air Force customer also assessed and approved flight clearance for this Delta IV mission."

            The ULA/PWR investigation concluded that a fuel leak within the upper stage RL10 engine system was the direct cause of the lower than expected engine performance on the GPS IIF-3 launch. To prevent a recurrence of this sort of fuel leak, the engine and vehicle systems have been very thoroughly inspected and also launch vehicle hardware modifications and changes to how the engine is operated during launch were implemented.

            "I thank our customer community and senior technical advisors for working with us throughout this very extensive investigation and flight clearance process," said Sponnick. "Given the comprehensive investigation that included extensive analyses and engine testing, along with the mitigating actions that have been implemented, we have concluded that the risks have been mitigated and that it is safe to proceed with the WGS-5 launch."

            Engine testing that was performed to support this ULA investigation replicated fuel leaks like those observed in the GPS IIF-3 launch.  The mitigations that have been implemented include extensive engine and launch-vehicle inspections to ensure that there is no damage and that there are no foreign objects that could cause problems for the operation of the engine system during launch.  Additionally, launch vehicle hardware modifications and operational changes have been implemented to mitigate risks for the WGS-5 mission and future launches.  The hardware modifications include the addition of in-flight helium purges to critical areas of the engine system.  The operational changes to reduce risk include changes to how the engine is thermally conditioned in-flight to prepare for the first engine start following the booster phase of flight.