Screenshot from ULA Webcast of NROL-68. Dark days ahead until the last Delta IV Heavy launch
Mission Rundown: ULA - Delta IV Heavy - NROL-68
Written: June 20, 2023
Just one more from Florida
United Launch Alliance (ULA) will be launching another satellite for the National Reconnaissance Office (NRO), the NROL-68, atop a Delta IV Heavy. This mission will mark the 15th mission of a Delta IV Heavy and 11th Delta IV Heavy mission for NRO.
Liftoff of the NROL-68 mission from Space Launch Complex 37B — at the Cape Canaveral Space Force Station in Florida — took place at 5:18:00 AM EDT - 09:18:00 UTC.
NOTAM with three splashdown areas. Nearest red is launch failure. Second is Delta side boosters. Third area is the Delta core booster and fairing parts. Flight path similar to NROL-37 and NROL-44
This was the 15th launch of a Delta IV Heavy from SLC-37 on June 22, 2023.
Thursday’s mission with NROL-68, is the second to last Delta IV launch from Florida’s Cape Canaveral Space Force Station, with the Delta IV Heavy’s last mission to be executed next year from the same pad SLC-37B on Cape Canaveral Space Force Base.
The NROL-68 Payload
Due to the NRO being a government agency, there is no publicly available information regarding the parameters and function of the NROL-68 satellite. It is also difficult to speculate on the purposes, size, mass, and function of the satellite. The NRO has chosen ULA because of their successful and highly accurate launches for all customers.
The NRO operates satellites that fill a variety of roles – including optical and radar imaging of Earth’s surface, detection and tracking of ships on the high seas and interception of radio signals and communications. The two types of satellites which require the largest rockets are a series of optical imaging satellites – known as Crystal – and a series of large signals intelligence (ELINT) satellites known as Orion.
Crystal satellites typically operate in near-polar sun-synchronous orbits, while Orions operate in an equatorial geostationary orbit.
Despite the top-secret nature of the mission, Notices to Airmen (NOTAMs) and Mariners (NOTMARs) must be published before every rocket launch. These include an immediate hazard area around Cape Canaveral, as well as areas downrange where debris may fall as the rocket sheds its lower stages and payload fairing on the way uphill.
These hazard areas show Delta IV Heavy will be heading in an easterly direction out over the Atlantic Ocean – and is therefore almost certainly heading to a geostationary orbit.
Because of the chosen orbit, which is similar to the NROL-44 mission 3 years earlier, it’s speculated that NROL-68 is an Orion intelligence satellite designated USA-345.
With NROL-68, NROL-44 and NROL-37 all in similar orbits, it is speculated they are ‘sister ships’ who might be replacing an aging USA-xxx satellite launched on a previous NROL mission ten to fifteen years earlier.
Orion itself appears to have gone through at least two generations of satellites, with the first two satellites being deployed from Space Shuttle Discovery with the aid of an inertial upper stage during its STS-51C and STS-33 missions in 1985 and 1989 respectively.
After national security missions transitioned back to expendable launch vehicles, two more NROL satellites were launched in 1995 and 1998 using Titan IV rockets with Centaur upper stages to geostationary orbits.
Leaked documents published by the news website The Intercept in 2017 showed that these first four satellites were designated Mission 7605 to 7608, while later satellites began a new series beginning with 8301.
These documents also indicated that the 8300-series satellites included communications intelligence capabilities allowing them to take over this role from a previous series of dedicated satellites which had been known by several codenames including Rhyolite, Aquacade, Chalet, Vortex and Mercury.
A report that suggested some of the NRO missions on Delta IV Heavy required the extra performance from the RS-68A upgrade. That said, the fact they still need the legacy Titan fairing suggests this is probably an evolution rather than a revolution compared to the earlier 8300 series spacecraft.
While the National Reconnaissance Office (NRO) keeps details of its satellites classified, the use of a Delta IV Heavy and the fact the launch is taking place from Cape Canaveral speak volumes. Delta IV Heavy missions carry satellites that have too great a mass for the most powerful Atlas V configurations to place into their destined orbits, indicating the satellite is very heavy, bound for a high orbit, or both.
From its location on the East Coast, Cape Canaveral is an ideal launch site for GTO and GEO intelligence/reconnaissance satellites operating in geostationary orbits, as well as some signal relay - intelligence - reconnaissance satellites placed in elliptical orbits.
The Delta IV Heavy Launch
Wednesday’s countdown saw the Delta IV rocket filled with cryogenic propellants while critical systems are powered up and tested as the count proceeds toward liftoff. The ignition sequence for the three RS-68A engines began seven seconds before liftoff with the starboard booster before the port and center cores ignited two seconds later. This staggered start helps mitigate the effects of hydrogen build-up around the base of the vehicle, which has scorched the rocket or set fire to insulation on previous missions.
Graphic of Delta IV Heavy with inserted details as close to current known facts about the vehicle
Liftoff occurred at T0. After Delta IV cleared the tower, it began a series of pitch and yaw maneuvers to attain its planned orbit, with the first of these beginning about 10 seconds after liftoff. Flying downrange, Delta 388 throttled down its center core to its partial thrust setting. It passed through the area of maximum dynamic pressure, or Max-Q, 89.6 seconds into the mission and reached Mach 1, the speed of sound, about 1.4 seconds later.
With the side boosters firing at full thrust and the center core operating in partial thrust mode, the port and starboard cores depleted their propellant first. As they approached burnout, they began to throttle back before shutting down at the three-minute and 56.3-second mark in the mission. The spent boosters separated 2.2 seconds later, falling away from the center core as it throttled up to full thrust.
Booster Engine Cutoff (BECO), the end of first-stage flight, occurs five minutes and 37 seconds after liftoff. Six and a half seconds after BECO, the first stage separates and the DCSS begins preparations to ignite its RL10C-2-1 engine, including deployment of the extendible nozzle. RL10 ignition occurs under 13 seconds after stage separation. 10 seconds into the burn, Delta IV payload fairing separates, and the NROL-68 payload is exposed to space for the first time.
With fairing separation complete, NRO missions tend to enter a news blackout, with further mission details remaining classified other than a brief press release to confirm the successful deployment of the satellite.
The DCSS can be expected to continue firing its engine for about 12 minutes as it inserts the satellite into orbit. A second transfer burn followed by spacecraft separation will occur at equator, before the DCSS restarts its engine for a third deorbit burn.
Graphic of the Delta Cryogenic Second Stage prior to payload attachment with a similar tank cage
DCSS will crash into the Indian/Pacific Ocean after less than one orbit. A short but sweet life of the Delta Cryogenic Second Stage. Unless it’s a direct GEO mission.
The Delta IV Heavy rocket
The Delta IV Heavy is a 725,7 ton reliable heavy lift launch vehicle, meaning that it can take bigger and heavier payloads into orbit. It can launch up to 28,370 kg (62,540 lbs) to a 90 degree - meaning compass course - inclination into Low Earth Orbit (LEO) and 14,210 kg (31,330 lbs) to a geostationary transfer orbit (GTO).
To accommodate payloads of all sizes, ULA offers two different payload fairing types with three heights both at 5.1 m (16 ft) in diameter. A 14 meter (47 ft) tall fairing and a 19.1 m (62.7 ft) tall fairing. As types go it's a three part Titan fairing and a two part Delta fairing.
The Delta IV Heavy first stage consists of three nearly identical 40.8 meter - 170 foot boosters strapped together. The Hydrogen and Oxygen tanks hold together 470 000 gallon of liquid propellant in 6 tanks measuring about 1 792 m3 in needed tank volume.
Each booster has one RS-68A engine also manufactured by Aerojet Rocketdyne. Together with DCSS and fairing they stand 71,6 meters - 235 feet tall on the launch pad.
Graphic showing ULA rocket Delta IV Heavy’s capacity to loft various payloads to different orbits
The Hydrogen tanks hold 330 000 gallon of liquid Hydrogen chilled to -252,8 0C Celsius or -423 0F Fahrenheit in 3 tanks measuring about 1 254 m3 in estimated tank volume. The three Hydrogen tanks each hold at least 418 m3 cubic meter liquid Hydrogen.
The Oxygen tanks hold 120 000 gallon of liquid Oxygen chilled to below -182,96 0C Celsius or -297,33 0F Fahrenheit in 3 tanks measuring about 454,2 m3 in estimated tank volume. The three Oxygen tanks each hold at least 151,4 m3 cubic meter liquid Oxygen.
NROL-82 states that 120 000 gallons of liquid Oxygen is loaded. NROL-44 gave me these numbers. Second source found. Is it 470 000 gallon of liquid propellant with DCSS?
Using a calculator dividing 33 with 15 gets you a ratio of 2,75 in hydrogen to oxygen. Doing the same with DCSS gets you a ratio of 1,33. 13,750 gallon LH2 divided with 5,000 gallon LOX gives you the same ratio of 2,75. Ergo 10,000 gallon LH2 and 6,000 gallon LOX are both wrong numbers. 1,250 gallons of liquid propellant is unaccounted for.
That is if the limit to DCSS volume is 20,000 gallons liquid propellant also includes X gallons of pressurized Helium + 150 kg Hydrazine N2H4. 146.9 liters or 38.8 gallons of Hydrazine.
The first stage is infamously known for lighting itself on fire just before launch to burn off extra hydrogen. It does this because it needs to get rid of any hydrogen so it does not explode unintentionally during liftoff.
The hydrogen comes from the purging or chilling of the engines prior to ignition. The engine can’t handle the freezing chock of liquid Hydrogen and Oxygen and will split itself apart especially in the turbopump bearings. They will become brittle and shatter.
Each RS-68A engine has the capability to produce 3,160 kN (705,000 lbf) of thrust for a combined 9,420 kN of total thrust. The RS-68A engine has a specific impulse of 362 seconds and uses a combination of liquid hydrogen (LH2) and liquid oxygen (LOx).
During the flight, the center booster burned at a slightly slower throttle setting - 80% - than the two side boosters. This is because the Delta IV Heavy needs all three boosters in order to get enough velocity to pass through the thick parts of the atmosphere. However, after that, they are expended and jettisoned as to not carry any extra weight.
As the vacuum optimized Delta second stage is very efficient, but not very powerful, the Delta IV Heavy burns its center booster longer than other rockets so the second stage will be able to put its payload into orbit.
Continuing up the rocket comes the second stage. The Delta Cryogenic Second Stage (DCSS) is powered by a single, vacuum optimized RL10C-2-1 engine with an extendable nozzle aka. enginebell. For its fuel, the DCSS too uses liquid hydrogen (LH2) and for the oxidizer, liquid oxygen (LOX).
The LH2 tank - volume of 38 m3 holding 10 000 gallon LH2 - being on top, it has the job of supporting the payload and the payload fairing and is structurally separated from the other ‘half’ of DCSS. The clearly smaller LOX tank - volume of 23 m3 holding 6 000 gallon LOX - is suspended below it and is responsible for structurally supporting the RL10B-2 engine.
The LH2 tank - volume of 52.0 m3 holding 13 750 gallon LH2 - being on top, it has the job of supporting the payload and the payload fairing and is structurally separated from the other ‘half’ of DCSS. The clearly smaller LOX tank - volume of 18.9 m3 holding 5 000 gallon LOX - is suspended below it and is responsible for structurally supporting the RL10B-2 engine.
With 20,000 gallons of liquid propellant reserved for the DCSS there should be room for 1,250 gallons of Hydrazine and pressurized Helium gas for orbit maneuvers and back filling of the empty propellant tanks.
The numbers of DCSS are found to be wrong. It must be double checked first.
The RL10C-2-1 was originally built by Aerojet Rocketdyne and first flew in 2022. It has the capability to produce 110 kN (24,700 lbf) of thrust in a vacuum and has a specific impulse of 465.5 seconds. It will light up at least four times with 18 minutes 15 seconds of burn time at an unknown throttle setting during the mission.
In order to save costs and weight, the gimbal system uses electromagnetic actuators over normal hydraulics; this also increases reliability.
Facts on this Delta IV Heavy launch vehicle
Height of Delta IV Heavy: 235 feet (71.6 meters)
Fuel onboard: 470,000 gallons of cryogenic liquid propellant
3 x Core stage Delta IV Heavy: 110,000 gallon LH2 - 40,000 gallon LOX
Second Stage 5 meter DCSS: 10,000 gallon LH2 - 6,000 gallon LOX
DCSS RL10C-2-1 thrust in orbit: 24 750 pounds - 106.7 Newtons
150 kg (340 lb) of Hydrazine is stored - Unknown so far - in a 50 gallon tank?
Helium storage tanks: Unknown so far - in four 300 gallon pressure vessels?
Mass at liftoff: 1,6 million pounds (725,750 kg)
Thrust at liftoff: 2.1 million pounds (9.4 mega-Newtons) 3 x 3123 kiloNewton
Orbit: Geostationary Orbit - 21 993 x 22 000 miles (35 218 x 35 500 km)
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