ULA conducts eighth mission of the year with Delta IV flight of AFSPC-4
CAPE CANAVERAL, Fla — A United Launch Alliance (ULA ) Delta IV Medium+ 4,2 rocket announced its presence to the surrounding marshlands on Monday, July 28 at 7:28p.m. EDT (2328 GMT). Carried aloft on this flight were three satellites under the banner of AFSPC-4. Liftoff took place at Cape Canaveral Air Force Station’s Space Launch Complex 37 (SLC-37) in Florida. Tonight’s launch of the ULA Delta 368 (this rocket’s official designation), was the culmination of a series of scrubs caused primarily due to weather conditions at the Cape.
Today’s successful launch followed an attempt on July 23 which was scrubbed due to issues with a ground support equipment environmental control system used to support the Delta IV and the subsequent three launch attempts on July 24, 25 and 26 were all canceled due to severe thunderstorms in the vicinity of SLC-37.
Weather also played a hand in this evening’s launch, delaying the mission from getting underway by some 45 minutes. As the original T-0 of 6:43 p.m. EDT came and went, two weather rules remained until around 7:18 p.m. EDT (2318 GMT) – attached anvil clouds and lightning, the first one faded shortly thereafter and with the “Go” – “No-Go” poll was held, the launch team awaited the lightning rule to clear – which it did soon after. With the last of the bad weather fading off into the horizon, the Delta launch team moved ahead with the mission and AFSPC-4 was on its way.
The AFSPC-4 mission is comprised of two Geosynchronous Space Situational Awareness Program (GSSAP) satellites to near-geosynchronous orbit as well as the Automated Navigation and Guidance Experiment for Local Space (ANGELS) satellite. These spacecraft will take a closer look at the increasingly cluttered landscape on-orbit and provide data and methods for coping with navigating the hyper-velocity minefield that now exists above our world.
The two GSSAP spacecraft were constructed by Dulles, Virginia-based Orbital Sciences Corporation (Orbital) and will become a part of the U.S. Strategic Command’s space-based assets. In this capacity they will serve as a dedicated Space Surveillance Network (SSN) sensor. GSSAP will also be used by the Joint Functional Component Command for Space (JFCC SPACE).
The spacecraft duo is the first of their kind to be launched. This facilitated the need for the first use of the EELV Secondary Payload Adapter or “ESPA.” Once on orbit, the two GSSAP spacecraft will gather space situational awareness information. GSSAP is tasked with providing more accurate data concerning man-made objects orbiting Earth.
From their vantage point in near-geosynchronous orbit, the two satellites will observe objects in low-Earth-orbit (LEO) and aid teams on the ground in determining if thee is a potential risk of collision. Ground-based systems are hampered in these efforts due to Earth’s atmosphere.
Data gathered by GSSAP should provide more accurate insights and predictions regarding the geosynchronous orbit environment. This is beneficial in terms of more rapidly and precisely determining if objects on orbit are in danger of striking one another.
Data gained by GSSAP will be transmitted to the ground via the world-wide Air Force Satellite Control Network (AFSCN) ground stations. From there they will be relayed to Schriever Air Force Base, CO where 50th Space Wing satellite operations will oversee day-to-day command and control operations.
The other portion of the flight, the ANGELS satellite is designed to conduct maneuvering tests on orbit using the Delta IV’s upper stage as a target. The ANGELS spacecraft will be managed by the U.S. Air Force’s Research Laboratory (AFRL) Space Vehicles Directorate where it will work to gain a better understanding of the environment surrounding key space assets.
ANGELS’ mission will last approximately one year and will work to validate spacecraft technologies as well as operational methodologies for use in geosynchronous orbit. To accomplish this, ANGELS comes equipped with an SSA sensor which should allow it to detect, track and characterize the space around a predetermined object on orbit. In this case, it will be the Delta IV’s spent upper stage. ANGELS will test out concepts on how spacecraft can be maneuvered while in GEO and will use accelerometers to monitor its speed as well as a GPS system to track its relative location.
NASA-provided algorithms will be employed to receive GPS side lobe signals and to generate near continuous navigation solutions. The experimental on board safety system will help to confirm concepts which may dramatically reduce the risk of on-orbit collisions.
With a recent uptick in the amount of launches as well near misses by space debris, the importance of developing these and similar systems is becoming more and more vital in terms of space safety. Although highly-dramatized, the 2013 motion picture “Gravity” detailed a scenario which showed a runaway multiple impact event where a space shuttle, the International Space Station, the Chinese Tiangong space station and most on orbit satellites were destroyed.
Much like GSSAP, ANGELS is a part of what is known as Space Situational Awareness or “SSA” and will work to find solutions to issues that are somewhat specific to geosynchronous orbit (GEO). The Department of Defense (DoD) Space Test Program or “STP” has partnered with other organizations involved with ANGELS so as to manage launch integrations as well as flight operations.
The launch vehicle tapped to deploy the three spacecraft is the Delta IV Medium+ 4,2, one of the two primary launch vehicles used by ULA (the other being the Atlas V). This evening’s launch marked the 27th flight of a Delta IV.
Designed around a Common Booster Core (CBC) design, the Delta IV can fly in as many as five different configurations, each designed to handle payloads of various sizes. The Delta IV Medium booster is often tapped for either national defense or Global Positioning Satellite payloads. However, in December of this year, the Heavy version of the Delta IV will be used to power NASA’s next-generation crewed spacecraft, the Orion Multi-Purpose Crew Vehicle on its first unmanned test flight.
The Delta IV CBC utilizes a single RS-68 rocket engine, supplied by California-based Aerojet Rocketdyne. The engine uses a mixture of liquid hydrogen and liquid oxygen as propellant. Developed in the 1990s, the RS-68 has the capability of imparting some 660,000 lbs of thrust (2,950 kilonewtons).
The CBC’s primary components are comprised of an array of isogrid aluminum barrels, spun-formed aluminum domes and machined aluminum tank skirts. This is covered with a combination of sprayed-on and bonded-on insulation as well as helium-purged insulation blankets. The Delta IV’s flight is controlled via avionics located in the Delta Cryogenic Second Stage (DCSS).
The DCSS is 39 feet (12 meters) in length and 12 feet (4 meters) and is constructed in a similar fashion and materials as the CBC, with its structure being comprised of isogrid aluminum ring forgings and spun-formed aluminum domes. The DCSS uses a single RL10B-2 engine which is capable of producing some 24,750 lbs of thrust (110,093 kilonewtons). During the October 2012 flight of the GPS IIF-3 satellite, an RL10 engine developed a leak in the throat portion of the thrust chamber. This caused a series of delays with the root cause of the problem left largely undetermined. SpaceFlight Insider reached out to Aerojet Rocketdyne shortly before today’s launch about the RL10B as to whether-or-not the issue has been fully resolved.
“Yes. The investigation has been completed and some preventative process changes have been incorporated in the engine/vehicle operations to further improve the overall reliability of the launch system,” said Steve Bouley, vice president of Space Launch Systems at Aerojet Rocketdyne.
Assisting the Delta IV in its efforts to escape Earth’s gravity well are two ATK -provided GEM 60 solid rocket motors (SRM). Some 53 feet (16 meters) in height and 5 feet (1.5 meters) in diameter, the “2” in the 4,2 designation denotes that this version of the Delta IV uses two of these boosters. Constructed from a composite graphite-epoxy material, each is connected to the CBC via two ball-and-socket joints and structural thrusters. Each of the GEM 60 SRMs weighs approximately 74,494 lbs (33,790 kg), and impart some 185,692 lbs (826 kilonewtons) of thrust.
The trio of spacecraft will be shielded from the turbulent atmosphere by the Payload Fairing (PLF). Produced by ATK, the PLF is comprised of a composite two-piece shell composite bisector (two-piece shell) and a 13 foot (4-meters – the “4” in the 4,2 designation) diameter fairing. Almost 39 feet (12 meters) long, the PLF provides a good portion of the 206-foot-tall (63 meter) Delta IV’s overall height.
The Mobile Service Tower or “MST” that shields the Delta IV during stacking and integration of the spacecraft was rolled back at 11:05 a.m. EDT (1505 GMT) on July 23 (it was rolled back after the July 26 launch attempt and moved back out of the way this morning). The massive building moved back some 120 yards (110 m) – about the length of a U.S. football field. This was one of the last steps that the Delta IV has to undergo before traveling on the road to orbit.
Countdown for the launch of AFSPC-4 started at T-5 hours and 15 minutes with the normal built-in 15 minute hold taking affect at T-4 hours and 15 minutes. During this time, carious aspects of the mission to include the health of the spacecraft, launch vehicle, weather and range were reviewed.
Around this time the Flight Termination System and Redundant Inertial Flight Control Assembly were activated. A little less than four hours before launch and propellant loading began. The liquid hydrogen ground system was pressurized and the CBC underwent gas chilldown of its fuel tank – this is done to prevent metal shock when the super cooled propellant is added.
Once the first stage is loaded with propellant, the DCSS is then fueled for flight. About 50 minutes prior to liftoff the RS-68 underwent a gimbal steering test we well as spin start pressurization.
Forty-five minutes before liftoff, the launch sequence entered into a built-in hold to allow one final review of the systems. During this period a weather briefing was held. Conditions for launch had only been given a 30 percent chance of being favorable for liftoff. Also during this time, flight software was initiated.
At T-minus four minutes the pace picked up with the booster running on internal power. At three minutes before launch, the ground ordinance was armed and the CBC’s fuel tanks were at flight pressure.
As the countdown clock struck “zero” – a bright flame emerged from the base of the booster at SLC-37 with the loud roar of the RS-68 coupled with the two GEM 60 SRMs announcing to the surrounding Florida marshlands that AFSPC-4 was on its way.
A mere 83 seconds into the flight and the vehicle was traveling faster than the speed of sound. Some 11 seconds later and the mission encountered the roughest patch of its journey. Known as “mas-q” or maximum dynamic pressure, this is the portion of Earth’s atmosphere that conspires with the speed of the launch vehicle to place the rocket and its precious cargo under the greatest amount of stress. Shortly thereafter, their job complete, the two GEM 60 boosters were jettisoned and could be seen trailing flame as they fell back toward Earth.
A little more than four minutes into the flight (approximately 246 seconds) and main engine cutoff (MECO) occurred. With staging taking place five seconds afterward. It’s role in the flight complete, pyrotechnics were activated separating the CBC from the DCSS aided by springs.
About four-and-a-half minutes mission elapsed time, the DCSS’ engine fired to life, pushing the remaining components on their way to orbit. Ten seconds later, the majority of the atmosphere behind it, the PLF separated, exposing the ESPA and the spacecraft it carried.
This evening’s launch marked the 33rd launch that ULA has carried out on behalf of the United States Air Force, the 27th launch of the Delta IV and the first time that the EELV Secondary Payload Adapter or “ESPA” was used. It also marked the tipping point in terms of the amount of launches the company has on their 2014 manifest. This evening’s launch was the 8th of 15 planned launches which include various iterations of the Delta IV, Atlas V and the Delta II.
“The ULA team is focused on attaining Perfect Product Delivery for the AFSPC-4 mission, which includes a relentless focus on mission success (the perfect product) and also excellence and continuous improvement in meeting all of the needs of our customers (the perfect delivery),” said ULA’s Vice President, of Atlas and Delta Programs Jim Sponnick.
AFSPC-4’s delay mean that the planned launch of an Atlas V 401 with the GPS IIF-7 satellite will now launch no-earlier-than August 1.
Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology, Space.com, The Mars Society and Universe Today.