Screenshot of the Cygnus NG-20 launch. Blue sky. What’s not to like? An exact launch time for one
Mission Rundown: SpaceX Falcon 9 - Cygnus NG-20
Written: January 30, 2024
The flying Beer Keg
The NG-20 mission has flown the Cygnus spacecraft S.S. Patricia Hilliard Robertson to a path that will take it to the International Space Station. This will be the first of three Cygnus missions to fly aboard Falcon 9 for Northrop Grumman to fulfill its cargo delivery contract while the new Antares 330 is under development.
Lift Off took place on Tuesday, January 30, 2024 at 12:07 ET - 17:07 UTC from Space Launch Complex 40 at Cape Canaveral Space Force Station.
The Falcon 9 rocket will be composed of booster B1077-10, the 305th operational second stage and a pair of fairings containing the Cygnus NG-20 weighing in at 8100 Kg.
The Falcon 9 didn’t perform a static fire test of the engines. This has been omitted many times due to Falcon 9’s increasing reliability. Only after engine swabs and issues with the importance of the payload does a static fire test become necessary.
B1077-10 will have made its tenth flight after launching its next mission:
After separating from the second stage, the booster B1077-10 will return to Landing Zone LZ-1 located 9 km from the launch site.
The return to launch site ‘RTLS’ flight profile shows an easterly trajectory. NG-20 flies northeast
Besides NG-20, the NG-21 and NG-22 missions are also scheduled to fly on Falcon 9, with NG-23 becoming the first Cygnus mission aboard the Antares 330. Firm launch dates for NG-21 and NG-22 are not yet set. In the meantime, NG-20 was the 10th Falcon 9 launch of this month, and of 2024.
After refurbishment of the booster, it will be designated as B1077-11. The second stage will after payload deployment be deorbited in the Pacific Ocean east of New Zealand a couple of hours after the launch.
The fairings might both be reused, one has a hatch installed for last minute packing of perishable goods and is perhaps flying for the first time. The other fairing will have flown for the N’th time (Who’s counting?). Doug will recover them 465 km downrange.
The Cygnus NG-20 payload
Falcon 9 has seen some modifications to launch Cygnus NG-20. There is a 1.5 by 1.2 meter (five by four foot) door in the fairing that can be opened to allow for late loading of cargo, which has been a key feature of Cygnus operations with the Antares rocket family. Once the fairing door is opened, a platform is erected that allows access to the Cygnus craft’s hatch while the rocket is horizontal.
The Cygnus NG-20 named the S.S. Patricia “Patty” Hilliard Robertson is carrying 3,726 kilograms of cargo. The cargo onboard Cygnus includes the first surgical robot to be flown to ISS as well as a metal 3D printer that will test printing small metal parts. In addition, a 3D cartilage cell culture, the MSTIC autonomous semiconductor manufacturing platform, and three reentry capsules that will test out different heat shield materials are also aboard Cygnus, along with supplies for the Station crew.
In addition to the experiments, an iROSA solar array upgrade kit will be sent to the Station aboard NG-20. This is the seventh upgrade kit and the third of four modification kits needed to allow for the installation of the final set of these upgraded arrays.
Replacement units for station equipment, such as the hydrogen dome assembly, ARED exercise device, ion exchange bed, catalytic reactor, urine processing assembly, and others are also aboard Cygnus.
After the Cygnus spacecraft was separated and inserted into orbit, it will take around two days to get to the ISS if all goes as planned. As early as 4:20 AM EST (09:20 UTC) on Thursday, Feb. 1, the S.S. Patricia Hilliard Robertson is to be grabbed by the Station’s Canadarm2. Using the robotic arm, astronaut Jasmin Moghbeli will berth Cygnus to the nadir (Earth-facing) port on the Unity module.
Graphic with details about Cygnus NG-20 seen with solar panels, the ‘Tug’ spacecraft and the ‘Keg’
S.S. Patricia Hilliard Robertson is scheduled to remain berthed to the ISS until May and can be called upon to perform orbital re-boost maneuvers during its stay. Before unberthing, it will be loaded with trash and empty cargo bags from the Station.
After departure, Cygnus will be commanded to make a destructive reentry over the South Pacific after releasing the University of Kentucky’s KREPE-2 reentry experiment with three capsules equipped with different NASA-provided heat shield materials.
The rocket launch
A typical Starlink mission begins with the countdown that has a traditional 35-minute long propellant load sequence which begins with RP-1 (a refined form of kerosene) loading on both stages and liquid oxygen (LOX) loading on the first stage only.
Loading of RP-1 on the second stage wraps up first at the T-20 minute mark followed by the usual “T-20 minute vent” as the oxygen purging begins on the pipelines of the Falcon 9 Transporter/Erector (T/E) that supplies fluids and power to the vehicle. LOX load on the second stage begins about four minutes after that at T-16 minutes.
Engine chill commences at the T-7 minute mark with a small flow of LOX going into the turbopumps on all nine Merlin engines on the first stage. RP-1 loading on the booster then wraps up about a minute later at the T-6 minute mark.
LOX load on the first and second stages ends at around the T-3 minute and T-2 minute mark respectively, and the rocket takes control of the countdown at the T-1 minute mark.
Engine ignition is commanded at T-3 seconds allowing them to achieve maximum thrust and pass final checks before committing to launch and if engine checks look correct, the ground clamps release the rocket for liftoff at the expected T0 time.
After liftoff, Falcon 9 climbs away from the launch site, pitching downrange as it maneuvers along its pre-programmed trajectory. Approximately 72 seconds into the flight, the vehicle passes through Max-Q — the point of maximum dynamic pressure, where mechanical stresses on the rocket are the greatest.
The nine first-stage engines continue to power Falcon 9 for the first two minutes and 30 seconds of the mission, until the time of main engine cutoff (MECO), at which point all nine engines shut down nearly simultaneously.
Stage separation normally occurs 3-4 seconds later, with the ignition of the second stage’s Merlin Vacuum engine coming about seven seconds after staging.
While the second stage continues onward to orbit with its payload, the first stage coasts upward to apogee — the highest point of its trajectory — before beginning its trip back to Earth. The booster refines its course toward the landing zone before attempting to softly touch down on the deck of one of SpaceX’s three drone ships.
Two or three burns are required to secure the safe return and landing of a Falcon 9 booster depending on the chosen landing site. A boost back burn nullifies the horizontal speed from about 7000 km/h plus to a 1000 km/h negative if a return to launch site is chosen.
Normally a free fall trajectory is chosen which requires a re-entry burn designed to break the speed into the denser atmosphere. The Merlin 1D# engines start in a 1-3-1 sequence with the center engine 9 starting 4 seconds before lighting up engine 1 and 5 in a burn lasting 14-16 seconds ending with a 2 second center engine solo burn.
The re-entry burn last 20-22 seconds and the booster is now falling and steering through the denser atmosphere with the 6x8 feet grid fins. A last landing burn performed by the Merlin 1D# center engine is timed to the last millisecond securing the aiming and breaking of the boosters speed. Booster landings have been performed almost 270 times.
Using a drone ship for booster recovery allows SpaceX to launch more mass in a payload on Falcon 9 than it would be able to launch on a return-to-launch-site mission.
In the meantime, the second stage carries on with the primary mission. After stage separation and Merlin Vacuum engine ignition, the payload fairing halves are jettisoned, thereby exposing the satellites to space.
Much akin to the Falcon 9 first stage, the fairing halves can be recovered and reused, using a system of thrusters and parachutes to make a controlled descent into the ocean where they will be picked up by a recovery vessel.
Second-stage engine cutoff (SECO-1) takes place just over eight and a half minutes into the flight. Other engine burns to modify or increase the deployment orbit will follow if the mission requires it, such as on this commercial mission which used a second burn before deploying the Cygnus NG-20.
The Cygnus NG-20 are deployed into a low Earth orbit. The Cygnus NG-20 will raise itself into a higher orbit, where it will chase the International Space Station where it will undergo checkouts before moving into the final docking operations.
After Cygnus NG-20 separation, the second stage will, if it’s still in low earth orbit, perform a deorbit burn for proper disposal, ensuring that reentry takes place in the south Pacific or Indian Ocean.
When the second stage comes in contact with ground control station in either Hawthorne, California or Boca Chica, Texas after one orbit. The deorbit burn and a blow out command is given simultaneously to brake and empty the propellant tanks. 40-45 minutes later the second stage re-enters and crashes into the Ocean.
The rocket vehicle
The Falcon 9 Block 5 is SpaceX’s partially reusable two-stage medium-lift launch vehicle. The vehicle consists of a reusable first stage, an expendable second stage, and, when in payload configuration, a pair of reusable fairing halves.
The Falcon 9 first stage contains 9 Merlin 1D# sea level engines. Each engine uses an open gas generator cycle and runs on RP-1 and liquid oxygen (LOx). Each engine produces 845 kN of thrust at sea level, with a specific impulse (ISP) of 285 seconds, and 934 kN in a vacuum with an ISP of 313 seconds.
Due to the powerful nature of the engine, and the large amount of them, the Falcon 9 first stage is able to lose an engine right off the pad, or up to two later in flight, and be able to successfully place the payload into orbit.
The Merlin engines are ignited by triethylaluminum and triethylborane (TEA-TEB), which instantaneously burst into flames when mixed in the presence of oxygen. During static fire and launch the TEA-TEB is provided by the ground service equipment. However, as the Falcon 9 first stage is able to propulsively land, three of the Merlin engines (E1, E5, and E9) contain TEA-TEB canisters to relight for the boost back, reentry, and landing burns.
The Falcon 9 second stage is the only expendable part of the Falcon 9. It contains a singular MVacD engine that produces 992 kN of thrust and an ISP of 348 seconds. The Falcon 9 can put some or many payloads in different orbits on missions with many burns and/or long coasts between burns, the second stage is able to be equipped with a mission extension package.
When the second stage has this mission extension package it has a gray strip, which helps keep the RP-1 warm in sunlight, an increased number of composite-overwrapped pressure vessels (COPVs) for pressurization control, and additional TEA-TEB.
SpaceX is the first entity ever that recovers and reflies its fairings. After being jettisoned, the two fairing halves will use cold gas thrusters to orientate themselves as they descend through the atmosphere. Once at a lower altitude, they will deploy drogue chutes and parafoils to help them glide down to a soft landing for recovery.
The Falcon 9’s fairing consists of two dissimilar reusable halves. The first half (the half that faces away from the transport erector) is called the active half, and houses the pneumatics for the separation system. The other fairing half is called the passive half.
Comparison of Type 1 and 2 with measurements based on pixels - Type 2 are 5-6 inches thicker
As the name implies, this half plays a purely passive role in the fairing separation process, as it relies on the pneumatics from the active half.
SpaceX used boats with giant suspended nets to attempt to catch the fairing halves, however, at the end of 2020 this program was canceled due to safety risks and a low success rate. SpaceX will attempt to recover the fairing halves from the water with the recovery vessel Doug.
There are three known types of 34 x 17 foot fairings used by SpaceX to protect payload during ascent through the atmosphere. The first type had 10 evenly spaced ventilation ports in a circle on the bottom part of the fairings. This type was not aerodynamic enough to carry a parachute and ACS - Attitude Control System.
The aerodynamic balance during descent must have made them prone to stalling, or they burned up too easily. ACS gas tanks, flight orientation computers and ACS thrusters must have helped with these problems during development of type 2 fairings.
The second type is a slightly thicker fairing with only 8 evenly spaced ventilation ports in a circle on the bottom part of the fairings. The ventilation ports release the pressurized Nitrox gas during ascent, but let seawater in which makes it harder to refurbish the fairings after recovery from the ocean.
In 2021, SpaceX started flying a new “upgraded” version of the Falcon 9 fairing. The third type has 8 ventilation ports in pair’s near the edge of the fairings.
Some old type 2 fairings have been rebuilt and reused in Starlink launches. That have been a test program to develop the type 3 fairings to prevent saltwater from the ocean from flooding and sinking the fairing, and makes refurbishment toward the next flight easier.
Lately it’s apparent that the fairings are actively aiming for the droneship in order to speed up the recovery process and cut corners of the time table. The fairings are breaking their speed during reentry and before deploying the parachute at altitude or the last moment.
Another solution is a ‘vertical’ boost lifting the fairings apogee so the ballistic trajectory is changed aiming for a landing nearer the droneship. It’s equivalent to raising the angle on a water hose giving the water stream an higher arc but giving it a shorter reach.
It’s not clear whether or not the cold gas nitrogen thrusters alone are capable of doing a ‘boost back’ or a ‘push up’ so the fairings can alter their forward momentum mid-flight. Every landing within 50 km of the ASDS seems to be an aimed fairing landing.
The Cygnus NG-20 won’t be utilizing this ‘push up’ fairing recovery program, which seems not to be in use anymore due to the danger of a wayward fairing half landing to close.
