First AEHF Satellite’s Orbital Maneuvers Delayed By Turner Brinton
WASHINGTON — The U.S. Air Force is investigating an anomaly with the propulsion system on its first Advanced Extremely High Frequency (AEHF) secure communications satellite and may alter its orbital maneuvering plan, the service announced Aug. 20.
The satellite was launched Aug. 14, and an unspecified problem occurred when operators fired the spacecraft’s thrusters to boost it to its designated testing orbit, Air Force Col. Dave Madden, the service’s military satellite communications program director, said in a press release. The satellite and all its subsystems remain safe and stable, and engineers are considering possible changes the orbital boosting process, it said.
The long-delayed AEHF constellation, built by Lockheed Martin Space Systems of Sunnyvale, Calif., will replace the military’s existing Milstar fleet for handling the most critical U.S. military communications. Lockheed Martin is under contract to deliver four AEHF spacecraft.
Japan’s IHI Aerospace is cooperating with the U.S. Air Force as it investigates the failure of its first Advanced Extremely High-Frequency (AEHF) satellite to reach orbit after an Aug. 14 launch, according to U.S. government sources.
IHI made the satellite’s model BT-4 liquid apogee engine (LAE).
The engine failed during two firing attempts to raise the spacecraft’s orbit shortly after launch. Air Force officials are now in the midst of a new effort to get the satellite into geosynchronous orbit after declaring the LAE useless for this mission (Aerospace DAILY, Aug. 27, 31).
Air Force officials had declined to say who made the LAE, noting that the cause of the failure is still being investigated.
“We don’t actually know what . . . is not allowing us to use the LAE engine,” says one government official. “It could be the fuel system, the fuel itself, an installation procedure used by any number of contractor teams, a flawed software routine controlling the propulsion system, or any number of other things; it is far too soon to start speculating on a specific manufacturer’s product at this time.”
U.S. officials also want to be sensitive to the Japanese company’s concerns, and they want to maintain a strong relationship to find the root cause and potentially implement fixes, if needed, in other LAEs for additional AEHF satellites.
AEHF is the next generation of protected military communications satellite. Lockheed Martin is the prime contractor on AEHF; Northrop Grumman is the payload provider.
Gen. Kevin Chilton, who oversees U.S. Strategic Command, says he is “not disappointed in AEHF,” noting that he is confident the satellite will eventually reach its intended orbit. “I don’t give up. I am very far from that,” he said Sept. 13 at the annual Air Force Association conference near Washington. The service is “blessed” that the Milstar constellation, which now handles the mission, is performing well, he adds.
If the Air Force’s orbit-raising process, which will use two other onboard thruster systems, goes well, the $2 billion satellite likely will reach operational status seven to eight months later than planned. With the use of the LAE, the satellite was slated to reach its orbital testing position in about 90 days.
A launch date for the second AEHF satellite has been tabled pending the mishap investigation.
Patience required as AEHF 1 recovery begins new mode[/size:7f8df4736f] BY JUSTIN RAY SPACEFLIGHT NOW Posted: October 17, 2010
Moving into the next phase of its orbital rescue, the Air Force's Advanced Extremely High Frequency satellite is warming up exotic electric thrusters to begin 10 months of propulsion-with-persistence that's needed to save the craft's life.
An artist's concept of AEHF 1. Credit: Lockheed Martin
This first bird in the U.S. military's new series of ultra-secure communications satellites was afflicted by a major problem soon after the August 14 launch that rendered its primary maneuvering engine useless.
A United Launch Alliance Atlas 5 rocket successfully dispatched the craft into a supersynchronous transfer orbit with a high point of 31,200 miles, low point of 140 miles and inclination of 22.2 degrees. From there, the satellite's own Liquid Apogee Engine was supposed to fire three times to ascend into an intermediate orbit.
The electric propulsion system using Hall Current Thrusters then would finish shaping the orbit into a circular, geosynchronous altitude 22,300 miles high and inclined 4.8 degrees by December.
That was the plan. But a fault somewhere in the main propulsion system for the Liquid Apogee Engine meant the 100-pound-thrust motor couldn't generate acceleration.
Satellite-maker Lockheed Martin and the Air Force quickly scrambled to devise an alternate strategy using other ways to propel AEHF 1 into an operational orbit.
The emergency plan to salvage the satellite called upon the craft's tiny five-pound-thrust steering engines to begin lifting the orbit higher. They couldn't reach the altitude target the Liquid Apogee Engine should have achieved, but the so-called Reaction Engine Assembly thrusters would deliver a worthwhile step in the right direction.
By late September, AEHF 1 had performed a dozen firings that resulted in boosting the orbit's low point to 2,900 miles and reducing inclination to 15.1 degrees.
"I'm massively pleased with where we ended up," said Dave Madden, Military Satellite Communications Systems Wing program director at the Air Force's Space and Missile Systems Center.
"We actually did significantly better, I'd say 10-15 percent better, than we thought we were going to do. As we kept doing it, we found better ways to optimize how we were pulsing those thrusters to optimize getting the maximum orbit raising out of them based on the fuel we were using. So each time we burned, we actually got better at our modeling on how to get the most out of what we were doing to minimize fuel usage."
After the Reaction Engine Assembly phase of the rescue was completed, the satellite's power-generating solar wings were unfurled and the Hall Current Thrusters were deployed.
"We're getting exactly the power out of the solar panels that we would expect to get. We're just working on the preps to go into the Hall Current phase," Madden said in an interview October 14.
The HCTs, produced by Aerojet, are 4.5-kilowatt units that use electricity and xenon to produce thrust for maneuvering satellites in space.
Unlike conventional chemical engines that deliver substantial boosts with each brief firing, the electric system needs the stamina to operate for exceptionally long periods of time to harness its whisper-like 0.06-pound-thrust into orbit-changing power.
The divergent systems have their advantages and drawbacks. Although typical engines can maneuver satellites rapidly, they use large amounts of heavy fuel that in turn require a bigger, more expensive rocket to carry the spacecraft. Electric propulsion gives up timeliness for efficiency since its xenon fuel weighs a mere fraction of conventional hydrazine, but you must have patience to reap the rewards.
"The beauty of them is for size, weight and power, it's an extremely efficient system - if time is okay," Madden said.
Commercial communications satellites built by Boeing began using small ion thrusters in the late 1990s. The company's Wideband Global SATCOM satellites for the U.S. military also employ them. NASA's Deep Space 1 and the Dawn space probes have relied on large ion engines for interplanetary propulsion as well.
But it's the electric thrusters on AEHF 1, which are different and haven't flown before, that ultimately hold the key to saving the mission. The satellite cannot reach its intended orbit and operate for a full 14- year life using only conventional hydrazine with its tiny Reaction Engine Assembly thrusters.
Activities underway the past few weeks have focused on readying the HCTs for their extensive usage.
"To be able to utilize them, we have to go through a series of checkouts and conditioning of some of the components," Madden said.
"I would have loved to have seen us just jump right into HCT operations, turn them on and go. But knowing it's a new, first-of-a-kind system, we have to methodically work our way through this and get ourselves on our way."
Controllers have been commanding the thrusters on and off for short bursts, slowly working towards longer and longer burn times.
"Components in the system absorb moisture when they are at atmosphere. So we have to burn that stuff off because it causes perturbations in operations if we don't burn it off first. Right now, we're going through this phase called conditioning of the HCTs and making sure we have the incremental steps right to bring them into operation," Madden said.
"When we get done with doing that, hopefully in a week, a week-and-a-half, if the conditioning goes well, then we will go into a full 10-hour burn a day for probably about seven months."
The satellite's present elliptical orbit takes nearly 17 hours to complete a full revolution around the planet. The HCTs will burn for 10 straight hours per orbit every day through next spring.
This critical seven-month period will increase the altitude at the orbit's low point, or perigee, and reduce the orbital inclination closer to the equator.
"What we are going to do in the first seven months is push out the perigee, then bring down inclination. So the heavy lifting is in the first seven months. Then what we're going to be doing in the last three months is circularizing and aligning it," Madden said.
That subsequent three-month phase in late spring and early summer does what the original pre-launch plan for the HCTs envisioned by burning the thrusters non-stop to reduce the orbit's high and low points into a circular 22,300-mile, geosynchronous altitude where the satellite can match Earth's rotation.
"We're anxious to get into this seven-month phase so we can get into more of a rhythm with the vehicle," Madden said.
Despite the crisis that prompted the heroics to recover the satellite's mission, the Air Force remains confident the craft will achieve the correct orbit and have enough residual fuel for operations to fulfill its 14-year life to relay communications between the president, military commanders and troops on the battlefield.
"We have adequate hydrazine left over from the last burn to be able to do full operations, and all of our projections associated with the xenon that we have available for the Hall Current Thrusters (show) we will have adequate xenon available when we get on-orbit to also sustain a 14-year life or longer," Madden said.
After the cumulative 10 months of HCT thrusting concludes next summer, the satellite will be parked over the equator at 90 degrees West longitude for activation and testing of its communications package. Once that is accomplished, flight controllers will slide the craft east or west in geosynchronous orbit based on where the military needs the craft.
"The operators are trying to decide after we get to 90 degrees what final location that they want us put the satellite and what's the exact inclination they want to us to put it at. But right now all indications are we can go anywhere they want us to go and we can support any inclination they want and do that for a 14-year life.
"We just have got to get through this phase of getting our HCTs checked out," Madden said.
Main engine probably not to blame for AEHF 1 trouble[/size:e89df3e190] BY JUSTIN RAY SPACEFLIGHT NOW Posted: October 19, 2010
As investigators narrow the list of potential culprits in the Advanced Extremely High Frequency satellite's main propulsion system problem, the Air Force has decided to delay launching the follow-up spacecraft and rearrange its upcoming Atlas rocket manifest.
The AEHF 1 satellite was carried aloft August 14 aboard a United Launch Alliance Atlas 5 rocket from Cape Canaveral, beginning a new era for secure military communications.
But the original plan of maneuvering the spacecraft toward geosynchronous orbit was aborted after the satellite's onboard Liquid Apogee Engine failed to accelerate AEHF 1 during two attempted burns on August 15 and 17.
The system detected that the proper boost wasn't being generated and immediately terminated the operations. Engineers have since created a rescue plan that's being implemented to use AEHF 1's smaller thrusters, but it will take nearly a year to accomplish.
The on-going investigation into the misfire indicates the main engine wasn't the cause of the problem and that the fault resides somewhere else in the overall propulsion system.
"I will tell you that I have high confidence it was not the engine itself and that it was part of the propulsion system that we think we are going to end up looking closely at," said Dave Madden, Military Satellite Communications Systems Wing program director at the Air Force's Space and Missile Systems Center.
"I don't want to speculate on the answer because right now we're going through some red team reviews. But right now I feel very, very confident that the IHI engine that we use was not the cause of this issue," Madden said in an interview October 14.
The engine, built by the Japanese aerospace firm IHI, is capable of producing 100 pounds of thrust while burning hydrazine fuel and nitrogen tetroxide. It was supposed to fire three times to propel AHEF 1 into an intermediate orbit after launch.
The second and third satellites in the AEHF series are undergoing pre-flight testing at the Lockheed Martin factory in Sunnyvale, California. Madden says the AEHF 1 investigation thus far isn't prompting any significant changes to the satellites before they are launched.
"We are not expecting any major redesigns to Vehicles 2 or 3 associated with this issue," Madden said. "I think it's going to be more (like) some tests and visual inspections that we have to do."
Looking at specific components on AEHF 2 and AEHF 3 or constructing special tests for the satellites will determine if they are trouble-free.
"My inclination is the only changes that it'll probably require is we'll probably have to do some testing to verify that we don't a similar condition because there's a couple potential root causes they're looking at and some of them exonerate themselves very well because it has to do with workmanship-type issues," Madden said.
The Air Force foresees the AEHF 1 investigation being wrapped up shortly.
"We all would have preferred not to have to deal with this issue and would have had a good firing of the engine. But it turns out it doesn't appear it was the engine itself that caused the problem, that it had something to do with the propulsion system," Madden said.
"We have a number of root causes that we are looking at, that we're going to try and close on in the next couple of weeks and we should be done with that and be able to move forward."
The AEHF 2 satellite had been slated for launch atop another Atlas 5 rocket next February. But the complex maneuvering of AEHF 1 using its tiny thrusters to achieve the correct orbit won't be finished until next summer and its communications payload can't be activated for testing until after that.
Given the AEHF 1 recovery schedule, Madden decided it was prudent to keep AEHF 2 on the ground until the first satellite passes the in-space testing.
"What I expressed to the senior leadership is I don't feel comfortable launching the second Advanced EHF until the first Advanced EHF gets to orbit and we can check out the payload," Madden said.
"We don't want to end up in a situation where we launch two satellites and we got some issue with the (communications) hardware of the first one that we haven't been able to verify. Obviously our confidence is extremely high that we don't have a problem, but I would feel much better checking it out before I launch the second satellite."
That decision automatically delays the AEHF 2 launch an entire year because of the Atlas 5 rocket's full schedule at Cape Canaveral. Complicating matters that prevent AEHF 2 from jumping into the lineup in late 2011 are two time-critical planetary probes that must launch during very specific windows.
Lockheed Examining Sats For Contamination[/size:92d3f7ecd1] Feb 2, 2011
By Amy Butler
SUNNYVALE, Calif. — Lockheed Martin officials are confident the suspected cause of a liquid apogee engine failure on the first Advanced Extremely High Frequency (AEHF) satellite — the introduction of foreign object debris (FOD) in the manufacturing process — will not pose a problem for other satellites built on the A2100 bus.
The company has been conducting “exoneration” exercises for other A2100-based satellites in various stages of manufacturing, including the U.S. Navy’s Mobile User Objective System, the Space-Based Infrared System (Sbirs) series, other AEHF spacecraft, and the Japanese Broadcasting Satellite Corporation System series, says Kevin Bilger, vice president of global communications for Lockheed Martin Space Systems here. These satellites are worth billions of dollars and took years to build.
The exoneration exercises are required to ensure that FOD was not introduced into the fuel or oxidizer lines for the propulsion systems of these satellites during manufacturing.
FOD in the oxidizer line is thought to have caused the failure of the liquid apogee engine (LAE), made by IHI Aerospace, on the first AEHF satellite shortly after launch Aug. 14, according to Bilger. “We have most probable cause as FOD,” he says. “In our business, you never have a smoking gun, but we have been able to replicate what we think the most probable cause is in the laboratory.”
AEHF is estimated to have cost the government more than $2 billion. Though the LAE failed, operators are using two of four onboard Hall Current Thrusters to slowly raise the perigee of the satellite. It is slated to reach orbit in the summer, months later than planned (Aerospace DAILY, Aug. 31, 2010).
The propulsion system for AEHF-1 was built at Lockheed Martin’s facility at the John C. Stennis Space Center in Mississippi in 2006. “During the manufacturing process, somehow [FOD] was introduced,” Bilger says. “The only known enemy to satellites is man. So, the longer you have them on the ground, the more opportunities there are for errors.” AEHF had a long buildup time owing to development issues and delayed delivery of encryption equipment from the National Security Agency.
Though the various A2100-based satellites share a similar core propulsion system, they do not all have the electric Hall Current Thrusters that are now raising AEHF-1’s orbit. This underscores the need to eliminate the risk of an FOD problem because not all models have other onboard resources for propulsion.
First to go through the exercise was the initial Sbirs satellite, GEO-1, which is slated for launch April 30. Lockheed Martin officials are now focusing on AEHF-2.
In each case, officials examine X-ray films taken of the propulsion system, including fuel lines, and all of the paperwork generated in the satellite manufacturing process. “As a result of our review, we made changes in our process,” Bilger says.
In the summer, Lockheed Martin will pressurize and test the fuel and oxidizer lines on AEHF-2 to validate their confidence that FOD is not present. “The actual test is not that long,” Bilger says. “But it is the test setup, it is the monitoring — getting all of the equipment and the electronics in place — and then looking at that data itself” that will require some time. AEHF-2 is slated for launch Jan. 30, 2012.
Чистящее вещество в топливной магистрали, которая не была должным образом промыта, является наиболее вероятной причиной отказа двигательной системы на борту AEHF - Richard McKinney, deputy under secretary of the Air Force for space programs.
Fri, 10 June, 2011 | Submitted by: Los Angeles Times | in commentaries AF Modifies AEHF Orbit-Raising Plan and Recoups Anomaly Cost [Los Angeles Times][/size:0349743746]
“LOS ANGELES AIR FORCE BASE, EL SEGUNDO, CALIF. — U.S. Strategic Command has approved Air Force Space Command's modification of the orbit-raising plan designed to transfer the first Advanced Extremely High Frequency space vehicle to its geosynchronous orbit. Furthermore, the Air Force has secured consideration from Lockheed Martin Space Systems Company to recoup anomaly costs through productivity improvements.
“To further optimize fuel usage during the orbit-raising process, the timeline for orbit-raising has been extended from Aug. 31 to Oct. 3, 2011, enabling a more efficient Hall Current Thruster burn strategy. This extension does not affect the initial operational capability date and provides additional fuel reserves to support potential future contingency operations.
“To address the costs associated with the modified orbit-raising plan, SMC and Lockheed Martin SSC have agreed to a $15 million reduction in available award fee and a contract restructure that incentivizes cost performance by the contractor team that will offset anomaly investigation and recovery costs. This restructure is consistent with ongoing DoD initiatives to improve weapon system affordability.
“Shortly after launch Aug. 14, 2010, an anomaly in its bi-propellant propulsion system thwarted the satellite's baseline plan to achieve its operational orbit. A joint SMC/Lockheed Martin team quickly developed a work-around plan enabling the satellite to reach its operational orbit. The satellite is expected to achieve full mission life and capability. The orbit-raising process for AEHF SV-1 using the Hall Current Thruster propulsion system is proceeding well. As of June 6, AEHF SV-1 perigee altitude had been increased to 28,187 km and the inclination reduced to ~6.2 degrees. AEHF's HCTs are built by Aerojet of Redmond, Wash.
“AEHF is a joint service satellite communications system that will provide survivable, global, secure, protected, and jam-resistant communications for high-priority military ground, sea and air assets. The AEHF System is the follow-on to the Milstar system, augmenting and improving on the capabilities of Milstar, and expanding the MILSATCOM architecture. AEHF is developed by the MILSATCOM Systems Directorate, which develops, acquires and sustains space-based global communications in support of the President, Secretary of Defense and combat forces.”
One year later: Air Force craft still fighting adversity[/size:e6419ca7b4] BY JUSTIN RAY SPACEFLIGHT NOW Posted: August 14, 2011
Launched from Cape Canaveral a year ago Sunday, the first satellite in the U.S. military's next-generation secure communications network continues its arduous journey to reach the correct orbit.
A manufacturing mishap prevented the Advanced Extremely High Frequency satellite's main propulsion system from firing once the craft reached space, prompting ground controllers to devise emergency plans for salvaging the mission.
Burning its exotic electric thrusters daily for the past 10 months, AEHF 1 has reached an orbit of 22,000 by 27,400 miles inclined 5.1 degrees to the equator, according to hobbyist satellite observers who continue to keep tabs on the craft's trek.
It should achieve the desired circular orbit with a 4.8-degree inclination on October 3, allowing payload activation and testing to begin in preparation for entering service at long last.
It has been a painstaking effort to save the spacecraft's life by working around the main engine problem and still climbing to the necessary orbital perch where it can match Earth's rotation to cover a large swath of planet.
The Lockheed Martin-built satellite was carried aloft on August 14, 2010 aboard a United Launch Alliance Atlas 5 rocket. But the original plan of maneuvering the spacecraft toward its operational orbit was aborted after the satellite's onboard Liquid Apogee Engine failed to accelerate AEHF 1 during two attempted burns on August 15 and 17.
The system detected that the proper boost was not being generated and immediately terminated the burns. According a Government Accountability Office report issued this summer, investigators probing the problem determined that debris mistakingly left inside the craft was the culprit.
The report cited "blockage in a propellant line that was most likely caused by a small piece of cloth inadvertently left in the line during the manufacturing process."
The Atlas 5 rocket successfully put the craft into a supersynchronous transfer orbit with a high point of 31,060 miles, low point of 170 miles and inclination of 22.1 degrees.
The satellite's main engine was supposed to produce 100 pounds of thrust while burning hydrazine fuel and nitrogen tetroxide during three firings to propel AHEF 1 into an intermediate orbit after launch.
The satellite's novel electric propulsion system using Hall Current Thrusters then would finish shaping the orbit into a circular, geosynchronous altitude about 22,300 miles high and inclined 4.8 degrees within 100 days of liftoff.
But with the Liquid Apogee Engine knocked out, the team designed a plan to use the craft's tiny five-pound-thrust steering engines to begin lifting the orbit higher. They would not reach the altitude target the Liquid Apogee Engine should have achieved, but the so-called Reaction Engine Assembly thrusters did deliver a dozen firings that resulted in boosting the orbit's low point to 2,900 miles and reducing inclination to 15.1 degrees.
The satellite's power-generating solar wings then unfurled and the Hall Current Thrusters were deployed. The 4.5-kilowatt HCT units that use electricity and xenon to produce thrust for maneuvering satellites in space.
But instead of simply finishing the altitude maneuvers as originally envisioned, the HCTs have been required to perform a much larger share of the work to position the satellite into a useful orbit.
The drawback for the electric system is the patience required to accumulate the whisper-like 0.06-pound-thrust into orbit-changing power over many months.
They burned about 12 hours per day from late-October through this June. Near-continuous firings have been underway this summer.
Despite the extra-long wait to get the satellite into the proper orbit, the Air Force says the satellite will have enough remaining fuel to function for its full 14-year service life.
This and future AEHF spacecraft will replace the aging Milstar satellite fleet to provide faster communications simultaneously to more users through modernized technology.
One AEHF spacecraft has more capacity than Milstar's five-satellite constellation combined and its faster data rates will benefit tactical military communications, enabling higher quality maps, targeting data and live video to be transmitted without being detected by the enemy.
AEHF was envisioned to keep communications flowing between the military and civilian leadership in any extreme wartime environment, giving the U.S. information superiority.
Assuming the AEHF 1 on-orbit activation and checkout goes well later this year, the Air Force plans to launch the AEHF 2 satellite atop another Atlas 5 rocket from Cape Canaveral next April.[/size:e6419ca7b4]