Screenshot from ULA Webcast of the launch of NROL-37. Standing here with nothing better to do
Mission Rundown: ULA - Delta IV Heavy - NROL-37
Written: January 1, 2023
A life in the Shadows awaits you
A United Launch Alliance (ULA) Delta IV Heavy rocket finally beat the Florida weather and launched a top secret payload - NROL-37 - into space for the US National Reconnaissance Office on Saturday June 11, 2016.
Launch from Space Launch Complex 37 (SLC-37) at Cape Canaveral was on schedule at the very start of the window that opened at 13:51 EST (17:51 UTC).
Google Earth screenshot of Delta IV Heavy flight path with the core booster crash landing zones - The little red zone is a smoke hazard zone, 2nd red zone is side booster crash site about 950 km downrange and 3rd red zone is the core booster crash site about 4 100 km downrange ± 100 km
Flying in its Heavy configuration, the Delta IV is the largest and most powerful rocket currently in service with the United States. NROL-37 will be the thirty-second Delta IV mission and the ninth for the Heavy version of the rocket.
Typically launch broadcasts and official coverage of NRO missions will end shortly after separation of the payload fairing from around the satellite.
The Medium and Medium+ versions of the Delta IV are expected to be retired by the end of the decade; although additional Heavies will be manufactured and placed into storage to serve as a stopgap to launch payloads too heavy for the Atlas V – typically just Orion satellites and Improved Crystal imaging spacecraft.
The NROL-37 Payload
As is usual for an NRO mission, details of the NROL-37 payload are kept classified by the US Government, as are specifics of the Delta IV mission profile.
Despite this, most NRO spacecraft can be identified long before launch from an analysis of information that has been made public, previous missions and past leaks. In the case of NROL-37, the use of a Delta IV Heavy indicates that significant performance is required.
Launching from Cape Canaveral, the rocket will be unable to reach high-inclination trajectories – such as polar, sun-synchronous and retrograde orbits – used by optical and radar imaging satellites.
Notices to airmen and mariners show the rocket will fly East after lifting off, towards geosynchronous orbit.
The Delta IV Heavy is capable of placing a payload of 6,750 kilograms (14,900 lb) directly into geosynchronous orbit or upwards of 14,000 kg (31,000 lb) into a geosynchronous transfer orbit.
Few satellites are large enough to require a Delta IV Heavy to reach geosynchronous transfer orbit; past NRO launches to use the vehicle from the Cape have all gone directly to geosynchronous orbit.
This suggests the payload will be an Orion electronic signals intelligence ELINT satellite.
The Delta IV Heavy Launch
Delta’s first stage is a Common Booster Core (CBC), powered by a single RS-68A which burns liquid hydrogen oxidized by liquid oxygen. In the Heavy configuration two further Common Booster Cores are attached at the side of the first stage, providing additional thrust during the early stages of flight.
All three ignited five and a half seconds before liftoff, building up to full thrust by T-0, when launch occurred.
After lifting off, the rocket pitched and yawed to attain its planned easterly trajectory. About fifty seconds after launch the center Common Booster Core’s engine throttled back to limit acceleration and conserve fuel.
Flying downrange over the Atlantic Ocean, Delta 374 passed through the area of maximum dynamic pressure around eighty seconds into flight. Shortly afterwards it achieved a speed of Mach 1, equal to the speed of sound.
Two and a half minutes into flight the vehicle rolled into an attitude at which the three CBCs were parallel to the horizon, in preparation for staging.
About 230 seconds after lifting off, the outboard boosters began to throttle down before burnout fifteen seconds later. Separation of the two spent boosters took place three seconds after cutoff, with the core engine throttling back up to increase thrust.
The core booster burned at full power for about seventy seconds, before throttling down again ahead of its own burnout and separation.
At five minutes and thirty-three seconds mission elapsed time the RS-68A shut down and seven seconds later the spent first stage was jettisoned.
The Delta IV second stage, a five-meter Delta Cryogenic Second Stage (DCSS), is powered by a single RL10B-2 engine also burning liquid hydrogen and liquid oxygen.
The engine has an extendible nozzle which will be deployed following first stage separation; the RL10 will ignite about 13.5 seconds after staging has been completed.
Ten seconds into second-stage flight, the payload fairing separated from the rocket.
Delta IV launches of Orion satellites make use of a modified Titan IV metallic payload fairing, in place of the Delta’s usual composite fairing.
This has a trisector design, meaning that it separates into three segments instead of two pieces like the fairings of most modern rockets.
Once the fairing separated, it was not expected that any further updates would be given on the status of the launch, other than to confirm whether it was successful or not.
Following fairing separation Delta 374 will likely follow a similar flight plan to Delta 310 – the first Delta IV launch – which attempted to carry a demonstration payload to geosynchronous orbit.
Although Delta 310 failed to achieve its planned orbit, details of its mission profile were published ahead of the launch and it is rumored that the mission was specifically a simulation of the Orion satellite launch profile.
The DCSS will need to make three burns; the first to achieve a low Earth parking orbit – requiring about seven minutes burn time – followed by a coast phase of about seven minutes, 40 seconds.
An eight-minute second burn will then be used to achieve geosynchronous transfer orbit.
Once the transfer orbit has been established, Delta 374 will coast to the apogee of its orbit, which will take around five hours, before making a three-and-a-quarter minute circularisation burn to raise its perigee and establish geosynchronous orbit.
After deploying the NROL-37 payload into this orbit, the stage will maneuver itself away from the geosynchronous belt at its best effort, as the remaining propellant allows, to limit the chances of colliding with an operational satellite.
ULA confirmed the successful conclusion to the mission around seven hours after launch.
The Delta IV Heavy rocket
One of the more powerful rockets currently in operation, the Delta IV Heavy has launched payloads including NROL satellites and the Parker Solar Probe, a mission to study the Sun. All of the previous Delta IV Heavy launches have been successful.
From another source we hear this.
The Delta IV Heavy rocket stands 71 meters - 233 feet tall, is 16.15 meter - 53 feet wide and weighs 725.75 tons - 1.6 million pounds fully fueled. It will launch on 9.34 Mega Newtons - 2.1 million pounds of thrust from the three RS-68A main engines.
Customers can choose between different payload fairing sizes to better optimize for their specific payload. There is a metallic trisector fairing available for special payloads.
To accommodate payloads of all sizes, ULA offers two different payload fairings both 5.1 meter (16 ft) wide. A 14 meter (47 ft) tall fairing and a 19.1 m (62.7 ft) tall fairing.
The Delta IV Heavy first stage consists of three nearly identical 40.8 meter - 170 foot boosters strapped together. Each booster has one RS-68A engine also manufactured by Aerojet Rocketdyne. 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 residual hydrogen so it does not explode unintentionally during liftoff.
The Delta IV Heavy first stage consists of three 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.
NROL-82 states that 120 000 gallons of liquid Oxygen is loaded. NROL-44 gave me these numbers. Second source found. Is 470 000 gallon of liquid propellant with DCSS +?
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.
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.
Screenshot of Delta Heavy IV split in its major parts. Known vehicle details have been inserted
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.
The hydrogen comes from the purging of the engines prior to ignition. 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 burns liquid hydrogen (LH2) and liquid oxygen (LOx).
During the flight, the center booster burned at a slightly slower throttle setting 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, the side booster pair is expended and jettisoned so as to not carry any extra weight.
As the vacuum optimized 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.
Graphic demonstration of Delta IV Heavy’s cargo capacity is thanks to the DCSS boost. link
Continuing up the rocket comes the second stage. The Delta Cryogenic Second Stage (DCSS) is powered by a single, vacuum optimized RL10B-2 engine. For its fuel, the DCSS 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, has the job of supporting the payload and the payload fairing with a strut gage of two rings and is also structurally separated from the other ‘half’ of DCSS. The clearly smaller LOX tank - volume of 23 m3 holding 6 000 gallon LOX - is suspended in a strut gage of two rings below it and is responsible for structurally supporting the RL10B-2 engine.
The RL10B-2 was originally built by Aerojet Rocketdyne and first flew in 1998. It has the capability to produce 110 kN (24,700 lbf) of thrust in a vacuum and has a specific impulse of 462 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 rocket engine's gimbal system either uses battery powered or fuelcell powered electromagnetic actuators over normal hydraulics; this also increases reliability.
With the propellant already consisting of liquid hydrogen (LH2) and liquid oxygen (LOx). I suspect that pumping gasses through a fuel cell to produce electric power is more weight economical than a massive lithium battery pack. But what do I know about that?
CBC RS-68A Spin Start Pressurization is complete and the CBC helium bottles are at flight pressure. ??? - Status comment heard once on flight controllers comm radio net.
The engine's turbo pumps fan blades are started with Helium gas pressure forced through them from a ground supply compressor and a Helium gas tank. I’m guessing here.
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