Screenshot from ULA Webcast of the AFSPC-4 launch. The weather a few days ago was like this
Mission Rundown: ULA - Delta IV M+4,2 - AFSPC-4
Written: January 24, 2023
Think of it as Space Traffic Cops
United Launch Alliance’s Delta IV rocket successfully deployed a pair of space surveillance satellites and a technology demonstrator for the US Air Force on Monday July 28, 2014 when the weather eventually cleared, allowing for a launch at 19:28 EDT - 23:28 UTC.
The Air Force Space Command 4 (AFSPC-4) mission comprises two Geosynchronous Space Situational Awareness Program (GSSAP) spacecraft and the Air Force Research Lab’s Automated Navigation and Guidance Experiment for Local Space (ANGELS).
NOTAM showing the booster debris field some 2500 km downrange from SLC-37B. The two SRB’s land near the second red dot. The fairing parts land about 1000 km downrange. No area marked
The launch of AFSPC-4 took place from Space Launch Complex 37B (SLC-37B) at the Cape Canaveral Air Force Station in Florida.
The DCSS deployed the satellites off in a near-geosynchronous orbit, an unusual mission for a small Delta IV M+4,2 configuration but the low payload mass made it possible.
The AFSPC-4 payload
GSSAP is a four-satellite constellation being developed by the US Air Force to conduct visual monitoring of geosynchronous satellites. The first two spacecraft are being carried by today’s launch, with the remaining two expected to ride an Atlas V into orbit next year.
The satellite pair is built by Orbital Sciences Corporation, many details of the GSSAP spacecraft remain classified, however each spacecraft must have a mass of less than 1,000 kilograms (2,204 pounds) in order for the selected configuration of Delta IV to be able to deliver them into geosynchronous orbit. The spacecraft will fall under the control of the US Air Force’s 50th Space Wing.
The ANGELS satellite, which has a mass of around 70 kilograms (150 lb), is a technology demonstrator which will be operated by the Air Force Research Laboratory. Also constructed by Orbital Sciences, this satellite is designed for one year of service.
It was attached to the Delta IV upper stage by means of an EELV Secondary Payload Adaptor (ESPA), from which it separated after the Delta deployed its primary payload and made its disposal burn. The Delta IV’s spent second stage will serve as a target for rendezvous and station keeping trials as part of ANGELS’ mission.
The Delta IV M+4,2 launch
According to its user guide, the Delta IV M+(4,2) is capable of placing 2,208 kilograms (4,870 lb) of payload into geosynchronous orbit.
The Delta IV’s first stage is a Common Booster Core (CBC), powered by a single RS-68 engine. Burning liquid hydrogen and liquid oxygen, the CBC ignited five second before launch, powering up to full thrust by the time the countdown reached zero.
At this point, the two GEM-60 solid rocket motors strapped to the first stage ignited and Delta 368 began her ascent, initiating a series of pitch and yaw maneuvers eight seconds into flight in order to attain its planned trajectory for the ride into orbit.
Flying East, Delta 368’s speed reached Mach 1 46.5 seconds after liftoff and the rocket passed through the area of maximum dynamic pressure, max-Q, 12.8 seconds later.
The twin solid rocket motors burned for 94.1 seconds, separating 5.9 seconds later; exactly 100 seconds after liftoff. The first stage’s RS-68 engine continued to burn until the four-minute, 5.3-second mark in the flight, with stage separation occurring six seconds later. Following staging the second stage began its pre-start sequence.
For this mission the second stage was the four-meter version of the Delta Cryogenic Second Stage (DCSS). Based on the second stage of the short-lived Delta III rocket, the four-meter DCSS is the smaller of the two upper stages used by the Delta IV, with a five-meter version used on some missions.
The DCSS is propelled by a single RL10B-2 engine which features an extendable nozzle to improve its specific impulse, or fuel efficiency. Following deployment of its nozzle, the RL10 was lit fourteen and a half seconds after staging.
Separation of the payload fairing, which occurred 10.2 seconds into the first burn of the second stage, is the last event whose time has been confirmed in the mission profile.
As is typical for missions carrying intelligence satellites for the US military, coverage of the flight ended at this point, other than a statement on the outcome of the launch after spacecraft separation.
To accomplish a direct insertion, the Delta needed to fly for six to eight hours, making three upper stage burns.
The first burn of the Delta Cryogenic Second Stage placed the vehicle and its payload into a low Earth parking orbit; cutoff is likely to have occurred around twelve minutes after launch. The rocket was then expected to enter a coast phase ahead of the second burn, which will have likely occurred just before the vehicle flies over the equator.
Such a burn can occur at either the descending node, as the rocket passes from the Northern hemisphere into the Southern hemisphere, or the Ascending node as it crosses from South to North.
An Ascending Node profile, given as a typical geosynchronous mission in ULA’s user guide, would call for this burn to occur on the first ascending node, around an hour and ten minutes after liftoff. The burn will have been shorter than the first, raising the apogee of the orbit to the altitude of the geosynchronous belt.
Following the end of the second burn, the rocket will have entered an extended coast, flying for over five hours to reach the apogee of its orbit. After attaining apogee, the third burn would have been conducted to circularize the orbit.
On an ascending node profile spacecraft separation would have likely occurred six and a half hours after liftoff, with the rocket subsequently making a collision avoidance maneuver to avoid adding to the debris in geosynchronous orbit. ULA confirmed the conclusion to the mission at around 07:00 GMT on Tuesday.
The Delta IV M+4,2 rocket
United Launch Alliance used a Delta IV rocket to conduct the AFSPC-4 mission, with the rocket flying in the Medium+(4,2) configuration and with a 2 208 kg payload.
Facts gathered about Delta IV M+4,2 give the following sets of data.
Delta IV M+4,2 stands 62.79 meter - 206.0 feet tall with a short 4 meter fairing
Delta IV M+4,2 stands 66.20 meter - 217.1 feet tall with a medium 4 meter fairing
Delta IV M+4,2 carry 470 000 gallons of liquid propellant - 1792 m3 tank capacity
Delta IV M+4,2 carry liquid Hydrogen, Oxygen, Hydrazine and Helium as propellants
Delta IV M+4,0 weighs 292 732 kilogram - 645 364 pounds alone without boosters
Delta IV M+4,2 weighs 327 040 kilogram - 721 000 pounds with two GEM-60 SRB’s
Delta IV M+4,0 produces 2 850.0 kilonewtons - 663 000 pounds of thrust
Delta IV M+4,2 produces 4 183.20 kilonewtons - 940 421 pounds of thrust with SRB’s
325 696 kg Rocket = 226 400 kg Core + 24 170 kg DCSS + 67 596 kg SRB + 5 898 kg fairing
The 5.9 ton ‘fairing’ part must consist of the Interstage ring, the PAF and the fairing halves which can be extended by one to two 3.66 meter - 12 feet sections depending on payload volume size. The interstage is estimated by me to weigh a third 1.5 ton, the fairings 3.2 ton and the Payload Attach Fitting weighs in this case 1 221 kg given a small payload size.
Payload to Low Earth Orbit 185 km x 185 km x 28.5o - 11 700 kilogram - 25 700 pounds
Payload to ISS 400 km x 405 km x 51.6o - 11 920 kilogram - 25 700 pounds
Payload to GTO 185 km x 35 400 km x 28.5o - 6 270 kilogram - 11 600 pounds
Payload to GEO 35 585 km x 35 600 km x 0.00o - 1 611 kilogram - 3 544 pounds
GEM-60 stands 13.20 meter - 43.16 feet tall with a diameter of 1.5 meter - 5 feet
GEM-60 weighs 33 798 kilogram - 74 511 pounds mounted and fully fueled
GEM-60 weighs 3 849 kilogram - 8 485 pounds empty at jettison after 91 second
GEM-60 produces 826.6 kilonewtons - 185 800 pounds of thrust at sea level
Delta IV Core Booster stands 40.80 meter - 133.8 feet tall - diameter 5.1 meter - 16.7 feet
Delta IV Core Booster carry 110 000 gallon LH2 - 416.4 m3 tank capacity
Delta IV Core Booster carry 40 000 gallon LOX - 151.4 m3 tank capacity
Delta IV Core Booster weighs 226 400 kilogram - 499 100 pounds fully fueled 195700
Delta IV Core Booster weighs 26 760 kilogram - 58 990 pounds empty at jettison
Delta IV RD-68 produces 2 950 kilonewtons - 663 000 pounds of thrust at sea level
Delta IV RD-68A produces 3 137 kilonewtons - 705 000 pounds of thrust at sea level
Delta Cryogenic Second Stage - 4 meter DCSS stands 12.20 meter - 40.0 feet tall
DCSS - LH2 tank diameter 4.0 meter - 13.1 feet - LOX diameter 2.44 meter - 8.0 feet
DCSS carry 10 000 gallon LH2 - 37.85 m3 tank capacity - uncertain volume
DCSS carry 4 000 gallon LOX - 15.14 m3 tank capacity - uncertain volume
DCSS weighs 24 170 kilogram - 53 290 pounds fully fueled + 195 700 kg core
DCSS weighs 2 850 kilogram - 6 280 pounds empty after 850 seconds of burn time
DCSS RL-10B-2 produces 110 kilonewtons - 25 000 pounds of thrust in vacuum
This consists of a Common Booster Core first stage with an RS-68 engine, augmented by two GEM-60 solid rocket motors, and a four-meter Delta Cryogenic Second Stage powered by an RL10B-2. The rocket uses cryogenic propellant – liquid hydrogen oxidized by liquid oxygen – in both liquid-fuelled stages.
The Medium+(4,2), or M+(4,2) is the second-smallest of the five Delta IV configurations to have flown; however the smallest, the Delta IV Medium, has not been used since 2006 and is not expected to fly again. The M+(4,2) is the most-flown version of the Delta IV; Friday’s mission will be its thirteenth launch and the twenty-ninth Delta IV overall.
The AFSPC-4 launch of the Delta IV M+(4,2) that flies with the RS-68 engine which it was designed with since the first launch in 2002. New Delta IV configurations are flying with the upgraded RS-68A engine; the Medium+(5,2) and Medium+(5,4) and the Delta IV Heavy.
Delta IV M+4,2 split in its major parts. Data points added from the graphic configurations
The Delta IV was integrated in the pad’s Horizontal Integration Building before being transported to the launch pad and raised to vertical. The AFSPC-4 satellites, already encapsulated within the payload fairing, were mounted atop the rocket at the pad.
The rocket that conducted Friday’s launch was numbered Delta 368, indicating that it was making the 368th launch of a Delta-family rocket; derived from the Thor-Delta vehicles first launched in the 1960s consisting of a first stage derived from the Thor missile and a second stage derived from the AJ-10-powered Delta.
Known facts about Delta IV M+5,2
Delta IV M+5,2 stands 67.0 meter - 220.0 feet tall with a medium 5 meter fairing
Delta IV M+5,2 weighs 340 194 kilogram - 750 000 pounds with two GEM-60 SRB’s
Delta IV M+5,2 produces 4 450.0 kilonewtons - 1 000 000 pounds of thrust + SRB’s
340 194 kg Rocket - 226 400 kg Core - 30 700 kg DCSS - 67 596 kg SRB = 15 498 kg
Payload to Low Polar Orbit 1 054 km x 106.59o - 9 600 kilogram - 21 164 pounds
Delta IV M+5,2 Cargo - ‘Bullitt’ with 9 600 kg Payload and 5 898 kg medium fairing
Payload Attach Fitting weighs 240 kg to 1 221 kg depending on payload size
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