Screenshot from ULA Webcast of the launch of NROL-71. Why do they pull back from me?
Mission Rundown: ULA - Delta IV Heavy - NROL-71
Written: September 20, 2021 - Edit: December 2, 2022
Just keep trying that red button
United Launch Alliance’s Delta IV Heavy rocket launched Saturday with the mysterious NROL-71 mission for the National Reconnaissance Office from SLC-6 at Vandenberg Air Force Base in California. A series of technical and weather-related scrubs hampered the launch attempts, prior to a lengthy stand down to fix a hydrogen leak that scrubbed the final attempt of 2018 with just seconds remaining in the countdown.
With the issue finally fixed, the first launch of this year was realigned for January 19, 2019 with the window opening at 11:05 local time - 19:05 UTC. Launch occurred after another short delay five minutes into the window at 11:10 Pacific Standard Time PST.
The use of a Delta IV Heavy means that the NROL-71 payload must either be too heavy to be deployed by any of the other rockets qualified to carry out the NRO’s most expensive and critical missions or destined for a sufficiently high orbit to require the services of this behemoth rocket.
The NROL-71 Payload
Observations of the NROL-71 payload, which is expected to be named USA-289 once it reaches orbit, will likely reveal more about its identity and mission. A lack of observations could point towards it being another Misty satellite.
The following link puts forward what seems to me a good argument for NROL-71 being a "Lacrosse Follow-on" rather than a new KH-11.
A search of the web for applications of non-sun-synchronous orbits for imaging turned up an unfamiliar concept that just might explain a 74 deg KH-11 orbit.
It’s a Multi Sun-Synchronous Orbit (MSSO). The plane of an SSO rotates once per Earth orbit around the sun. An MSSO rotates multiple times during the same period.
SSO follows the Sun regardless of the Earth's rotation below. MSSO can follow the same orbit track along the ground by preceding 2, 3, 4, 6, 8, 12 and 24 times a day. The latter 24 means the orbit precedes 15 degrees each orbit following the Earth's rotation and will always follow the same track fx. along the Atlantic Ocean from Kap Horn to Nordkapp along the Russian Polar coast and down over the Pacific Ocean.
The following paper states that MSSO orbits could be adopted by those Earth science missions whose aim is to study the local hour effects on the observed object.
The Delta IV Heavy
The Delta IV Heavy that was used for the NROL-71 mission is the heaviest rocket currently certified to carry out national security launches of this nature.
The Delta IV Heavy uses three Common Booster Cores strapped together, with the center core operating at partial thrust for much of its flight to extend its burn beyond that of the two outboard cores.
After stage separation, the Delta Cryogenic Second Stage (DCSS), which like the first three common booster cores burns cryogenic propellant: Liquid hydrogen and liquid oxygen, will get the payload all the way up in its preliminary orbit and given that the payload isn’t too heavy initiate a second burn to a transfer orbit.
Graphic picture of Delta IV Heavy split in its major parts. The spacecraft is not NROL-71
This configuration of the Delta IV is created by taking three hydrogen-fueled common booster cores, each with an Aerojet Rocketdyne RS-68A main engine, and strapping them together to provide over two million pounds (9 MN) of Earth-shaking thrust at liftoff. The Delta Cryogenic Second Stage is powered by an Aerojet Rocketdyne RL10B-2 engine.
The Delta IV Heavy launches on the combined power of three RS-68A engines, burning liquid hydrogen and liquid oxygen to produce 702,000 pounds (3122 kN) of thrust each. The port and starboard boosters are more than 150 feet (45.7 m) tall, and the center core with the interstage attached is over 175 feet (53.3 m) in length. They measure 16.7 feet (5.1 m) in diameter.
The Delta Cryogenic Second Stage also burns liquid hydrogen and liquid oxygen to produce 24,750 pounds (110 kN) of thrust from the RL10B-2 engine. The powerplant features a deployable carbon-carbon nozzle that is 7 feet (2.1 m) in diameter.
The NROL-71 launch began with the ignition of the RS-68A engines that power the three Common Booster Cores.
The starboard core ignited seven seconds before the scheduled liftoff, with the port and center boosters igniting two seconds later at T-5. This staggered ignition is intended to mitigate a fireball that can form around the rocket on startup as a result of hydrogen boiling off the rocket. Liftoff occurred at the zero mark in the countdown.
After pitching over onto a south-easterly azimuth of about 168 degrees, Delta IV passed through the area of maximum dynamic pressure – Max-Q – shortly before it reached Mach 1 – the speed of sound – 82 seconds into the flight.
Notam for crash sites for Delta IV Heavy’s two side boosters at N25, main core booster just below Equator near W110 and DCSS deorbits at or about N40 x W147. It’s raining rocket parts.
The three CBCs powered the rocket for the first three minutes and fifty-six seconds of the flight, with the port and starboard boosters burning at full thrust and the center core at partial thrust. When the two outboard cores depleted their propellant, their engines shut down, and the spent cores separated two seconds later.
Once the port and starboard boosters separated, the center core throttled up and burned at full power for most of the remaining two minutes of first-stage flight. Seven seconds after main engine cutoff (MECO), the first stage was jettisoned and the second stage entered its prestart sequence. The RL10B-2 engine ignited twelve seconds after stage separation. Eleven seconds later, Delta IV payload fairing separated from the nose of the rocket, exposing the payload to space for the first time.
Owing to the classified nature of this mission, United Launch Alliance has not published a timeline for mission events following fairing separation and as is normal for NRO flights all official coverage of the mission is expected to conclude at this point other than a press release confirming a successful launch some time after spacecraft separation.
The second stage will likely make a single burn to circulize the orbit, lasting around 12 minutes, before separating its payload into low Earth orbit. An additional launch hazard area to the northwest of Vandenberg suggests that the second stage will with a third burn be deorbited into the Pacific shortly after separation.
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