Screenshot from the launching of SARah 2 & 3. SARah-1 took off last year, now it’s the twins turn
Mission Rundown: SpaceX Falcon 9 Block 5 - SARah 2&3
Written: December 24, 2022
Flying side by side
Sunday, December 24 a SpaceX Falcon 9 launched the SARah-2 & -3 missions from Space Launch Complex 4 East (SLC-4E) at Vandenberg Space Force Base in California. The instantaneous launch window is at 05:11:00 PST − 13:11:00 UTC.
The Falcon 9 first stage booster supporting this mission previously launched the SDA-0A and six Starlink missions. Following stage separation, Falcon 9’s first stage will return to land on Landing Zone 4 at Vandenberg Space Force Base in California.
SpaceX successfully launched the SARah 2 & 3 radar satellites for Bundeswehr on their Falcon 9 into a 750 km Sun-Synchronous Orbit.
SARah 2 & 3 is a secret mission, so no video footage will be shown beyond the 1st stage top bulkhead. Only 2nd stage engine views can be expected.
NGA from Raul concerning SARah’s flightpath out of Vandenberg flying almost due south
B1075-8 will have made its eighth flight after launching its next mission:
B1075-8 didn’t perform a static fire test after refurbishment and waiting for a west coast launch out of SLC-4. SpaceX has omitted this safety precaution 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.
The fairings are both reused flying for the N’th time with no known previous missions flown together. Go Beyond will recover them 493 km downrange.
After lift-off from Space Launch Complex 4E, SLC-4E, Falcon 9 took a southward trajectory as it climbed through the atmosphere. The first stage’s nine Merlin 1D# Engines cut off around the T+2 minutes 20 seconds mark, with stage separation and a 1st stage 150° flip maneuver following within seconds after MECO. The 1st stage performed a 44 second long and flat boost back burn to put it on a course back to the launch site.
While B1075-8 flew back towards the launch site, Falcon 9’s second stage and its single Merlin Vacuum (MVac) engine placed the SARah-2 & 3 satellites into orbit and will operate in a circular orbit inclined at 98.4 degrees to the equator, with an altitude of about 750 kilometers above the surface of the Earth.
Unlike most recent Falcon 9 launches from Florida, the SARah-1 flight’s booster did not need a drone ship sent out to the Pacific Ocean to recover it. Instead it flew a return to launch site (RTLS) profile, with the booster softly touching down on the concrete pad at Landing Zone 4 (LZ-4) back at Vandenberg Space Force Base.
After the boostback burn was completed, B1075-8 positioned itself for atmospheric entry before conducting an entry burn to protect the stage from excess heating — a technique of fighting fire with fire — by using rocket thrust as both a heat shield and to slow the stage down. The final landing burn - timed to counter the gravity drag - began 23 seconds before touchdown, slowing the booster to a midair hover and a soft landing at LZ-4.
SLC-4 is Falcon 9’s launch and landing site at VSFB. The entire complex is composed of two launch sites: SLC-4E (East) and SLC-4W (West). SLC-4E is used as Falcon 9’s launch site. It was first used for Falcon 9 in September 2013 on the CSA’s CASSIOPE mission. Since then, it has been used 59 more times, with SARah-2 & 3 as the 60th SpaceX launch from the pad at Vandenberg Space Force Base in California.
SLC-4W was unused for Falcon 9 launches. It was instead converted from a Titan launch site to a landing pad in the mid to late 2010s. Now named LZ-4, it was first used in a first-stage, West Coast Return to Launch Site (RTLS) landing in October 2018 on the SAOCOM-1A mission. Since then, it has now been used fourteen times.
The Payload from the past
The development contracts were signed in 2013 back in the days when Falcon 1 was the only active asset to SpaceX. The launches of the SARah satellites were planned in 2018 and 2019. But satellite-related technical problems, efforts to improve encryption on the spacecraft, and delays caused by the COVID-19 pandemic pushed back the first SARah spacecraft launch until 2022.
Another delay was the grounding and destruction of the heavy Antonov cargo planes caused by the Russian invasion of Ukraine. An-225 Mriya was the only 6 engine cargo plane built to carry the Buran Space Shuttle, and was making a existence by flying heavy cargo worldwide for all purposes. The Antonov cargo fleet was grounded.
SARah 1 was driven to Bremen, sailed by ship on ARC Defender to Baltimore, USA and driven cross-country by truck all the way to Vandenberg Space Force Base in California, a 25 day journey which was documented by SpaceX.
SARah 1 is the first of three radar imaging satellites the German government ordered from industry in 2013. OHB, based in Bremen, is the lead contractor on the SARah program and is building the second and third satellites in the series. Airbus teams in southern Germany manufactured the first and largest satellite in the program, named SARah 2 & 3, which awaits launch Sunday from California.
The SARah 2 & 3 satellite is a radar reconnaissance satellite that is built by Airbus Defense and Space and operated by the German armed forces, called Bundeswehr. The satellite is set to replace the aging SAR-Lupe constellation, which, as the name implies, is a Synthetic Aperture Radar (SAR) constellation that the German government and defense ministry currently uses for reconnaissance.
The SAR-Lupe constellation will be replaced by the SARah1, SARah 2, and SARah 3 satellites; the first satellite, SARah 1, will be equipped with a phased array antenna which will increase the resolution of the SAR constellation, past that of SAR-Lupe. SARah 2 and SARah 3 will be two “reflector antenna” satellites, meaning they will fly in formation with SARah 1 to increase the resolution of the constellation.
SARah 2 & 3 are each equipped with solar panels and batteries to provide power to the spacecraft. It is unknown what kind of propulsion the satellite uses.
The Falcon 9 launch
A typical Falcon 9 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 steeply away from the launch site, pitching downrange as it maneuvers along its pre-programmed trajectory. Approximately 62-72 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 near-simultaneously.
Stage separation normally occurs four 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 4x5 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. The booster landing has now been performed over 200 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. The fairings can be recovered and reused, using a system of gas thrusters and parachutes to make a controlled descent into the ocean.
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. SARah 2 & 3 will require a circularization of its initial orbit.
After spacecraft separation, the second stage will, if it’s still in low earth orbit, perform a deorbit burn for proper disposal, so that reentry takes place in the Pacific Ocean.
When the second stage comes in contact with the ground control station presumably in Nome, Alaska. 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 central Pacific Ocean east of New Zealand.
The Falcon 9 rocket
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 paint 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. It’s suspected that the passive fairing unlocks the twelve hooks in the fairing hinge locking mechanism by rotating them.
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. On Starlink Group 7-9 , SpaceX will attempt to recover the fairing halves from the water with the recovery vessel GO Beyond.
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 was letting in seawater 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 50 km from the ASDS doesn’t seem to be an aimed fairing landing.
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