Superbird-8, GSAT-18 - Ariane 5 ECA (VA231) - Куру ELA-3 - 05.04.2018 21:34 UTC

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DutchSpace‏ @DutchSpace 2 мин. назад

18:29:00 [L-05:05:00] Last personnel evacuation from ELA3 #VA242 #Ariane5

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DutchSpace‏ @DutchSpace 6 мин. назад

19:51:00 [L-03:43:00] EPC filling lines cooling and tanks filling #VA242 #Ariane5

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DutchSpace‏ @DutchSpace 3 мин. назад

20:01:00 [L-03:33:00] ESC-A filling lines cooling and tanks filling #VA242 #Ariane5

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DutchSpace‏ @DutchSpace 2 мин. назад

20:11:00 [L-03:23:00] Vulcain 2 engine cooling #VA242 #Ariane5

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04/05/2018 21:34 Stephen Clark

T-minus 3 hours. The Ariane 5 rocket's first stage, known by the French acronym EPC, is currently being filled with liquid oxygen and liquid hydrogen. The second stage, or ESC-A, should also be receiving the same mix of liquid propellants. The first stage Vulcain 2 engine and the upper stage HM7B engine both consume the super-cold fuel.

The cryogenic propellant will be gradually pumped inside the rocket to maintain proper levels as the fuel evaporates over the rest of the countdown.

The Ariane 5's supply of cryogenic liquid helium, used to pressurize the rocket's propellant tanks, was loaded aboard the launcher Wednesday.

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http://spaceflight101.com/ariane-5-ready-for-comeback-mission-with-communications-satellite-pair/

Ariane 5 Ready for Comeback Mission with Communications Satellite Pair
 April 5, 2018

Photo: Arianespace/ESA/CNES/Optique Video du CSG

Europe's Ariane 5 rocket stands ready for its comeback mission a little over two months after taking a wrong turn and leaving a pair of communications satellites in a seriously-deficient orbit. Cleared to return to action via more stringent quality control checks, Ariane 5 is targeting liftoff on Thursday during a 50-minute window opening at 21:34 UTC with the Superbird-8/DSN-1 dual-use satellite fr om Japan and the HYLAS 4 high-throughput satellite for London-based Avanti Communications.

Спойлер

Ariane 5 last launched on January 25 on a rare Supersynchronous Transfer Mission with the SES 14 and Al Yah 3 communications satellites. For outside observers, the mission appeared to go by the book until communications with the climbing rocket were lost some nine minutes after liftoff and could not be regained for the rest of the planned 35-minute mission – sparking fears that the two satellites had been lost. Tracking stations went into search mode and successfully discovered both passengers in good health, but far off from their planned orbit.


Ariane 5 VA241 Liftoff – Photo: Arianespace/ESA/CNES/Optique Video du CSG

As it transpired over the weeks after the incident, Ariane 5 lifted off with an improper value programmed into its inertial guidance system which sent the rocket into a roll maneuver immediately after liftoff and caused a 20-degree shift to the south in the rocket's flight path.

The improper setting was the result of an unusual set of requirements for this mission that dictated a 70-degree azimuth setting instead of the usual 90 degrees that had been the norm for all recent GTO missions by the vehicle. Checks and re-checks did not reveal the error as all involved entities had gotten used to seeing the azimuth parameter as 90.

Going into a roll immediately after liftoff resulted in the rocket departing on a launch azimuth in the neighborhood of 110 degrees – taking it much closer to the city of Kourou than for a normal mission and leaving the satellites in a 21-degree inclined orbit instead of the planned orbital inclination of three degrees.


Ariane 5 Trajectory Deviation – Planned (North) vs. Actual (South)

Both satellites have since taken steps to correct their orbits – a difficult endeavor as they have to rotate their orbits in order to achieve circularization over the equator to reach a Geostationary Orbit, a process that requires time and/or additional maneuvering propellants.

The all-electric SES 14 satellite was expected to suffer a lesser impact than Al Yah 3 that relies on a hybrid propulsion system combining chemical and ion thrusters. Insurance claims have been submitted for Al Yah 3 and both satellites are still several weeks from reaching their operational orbits.

An investigation into the anomalous Ariane 5 flight was conducted by Arianespace, ESA and the French Space Agency CNES, recommending a number of steps to strengthen the quality control steps involved in generating the mission-specific parameter inputs for Ariane's navigation system.


Photo: Arianespace/ESA/CNES/Optique Video du CSG

"Recommendations to improve processes and quality control have been made. Furthermore, additional recommendations to enhance end-to-end verifications of mission-specific parameters used during the launch campaign were made," ESA said in a statement after the investigation had presented its findings.

ESA and Arianespace were somewhat tight-lipped on the specifics of the anomaly and corrective measures and the results of a CNES-led probe into the response of flight safety to the launcher deviating from its trajectory have also not been disclosed to the public. The launch of a Soyuz rocket in March had to be delayed by three days because range-related recommendations from the VA241 inquiry were still being implemented.

The VA242 mission was originally expected in the second half of March but was pushed to a new date of April 5th without a reason for the delay being made public.

Thursday's mission is carrying a total payload upmass of 10,260 Kilograms between the two satellites and their various adapter systems holding them in place in a stacked configuration, primarily enabled by the Sylda divider structure. Riding in the upper berth is the Superbird-8/DSN-1 satellite setting out on a dual-purpose mission delivering commercial and military communications services while HYLAS 4, affixed to the rocket's second stage, will provide high-throughput data services as part of Avanti Communications' satellite fleet.

Superbird-8/DSN-1 was commissioned as a dual-use satellite, outfitted with a Ku/Ka-Band payload to deliver commercial networking services while a military X-Band terminal provides encrypted communications for Japan's armed forces under the DSN project.


Superbird-8/DSN-1 Satellite – Image: SKY Perfect JSAT

DSN Corporation was instated as a joint venture between SKY Perfect JSAT, technology company NEC, telecommunications provider NTT Communications, and civil engineering company Maeda Corp. Under Japan's first Private Finance Initiative, these companies put up private funds to realize the DSN satellite constellation and ground infrastructure that is being leased to the Japanese government through 2031 and driving in revenue for the commercial partners.

The DSN Network comprises two space segment components – DSN-1 is a hosted X-Band payload on the Superbird-8 satellite and DSN-2 is a dedicated satellite. DSN-1 had been set for launch in 2016 but encountered an overpressurization event during the transfer to the Guiana Space Center and required extensive repairs; also resulting in DSN-2 becoming operational as the first constellation member following its launch atop an H-IIA rocket.

>> Superbird-8/DSN-1 Satellite Overview

Because of its partially military nature, no photos were released of the Mitsubishi Electric-built satellite and details on its mission are withheld from the public. The commercial part of the satellite's payload will be re-named Superbird-B3 once in orbit and replace the B2 satellite that launched in 2000 to deliver business telecommunications services and VSAT expansion services over Japan.


Photo: Orbital ATK

HYLAS 4 weighs in at 4,050 Kilograms and employs Orbital ATK's GEOStar-3 satellite platform that was inaugurated earlier this year as the company's most advanced satellite bus. Outfitted with a Ka-Band payload, HYLAS 4 will deliver high-throughput broadband and networking services to markets in Europe and Africa.

The payload delivers 66 fixed Ka-Band beams positioned over Africa and Europe with a total capacity of 28 Giga-Hertz; the addition of four steerable Ka-Band beams enables supplementary coverage to be directed wh ere it is needed within the satellite's footprint.

>> HYLAS 4 Satellite Overview

HYLAS 4 switched from a late 2017 launch slot on Ariane 5 to the VA242 mission to be paired with a slightly lighter upper berth passenger in order to gain a little bit of mass itself in the form of additional propellant loaded into its tanks. This additional propellant load allowed the satellite's orbit-raising scheme to be accelerated by eliminating 100 days of orbit topping with its electric propulsion system and so arrive on Station earlier while also saving stationkeeping propellant for a longer operational life.

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Трансляция Arianespace на ТыТрубе

youtube.com/watch?v=VDEQ4U89zzU

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DutchSpace‏ @DutchSpace 6 мин. назад

Nice picture while we wait... (yup its the wet season in CSG alright...) #Ariane5 #VA242

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DutchSpace‏ @DutchSpace 1 мин. назад

21:41:00 [L-01:53:00] ESC-A Helium sphere pressurization #VA242 #Ariane5

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DutchSpace‏ @DutchSpace 2 мин. назад

22:14:00 [L-01:20:00] Telemetry transmitters and Radar Transponders switch on #VA242 #Ariane5

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04/05/2018 23:49 Stephen Clark

Minus-45 minutes. Everything remains on track for launch at 2134 GMT (5:34 p.m. EDT; 6:34 p.m. French Guiana time).

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Spaceflight101 LIVE‏ @S101_Live 7 мин.назад

Riding in the upper payload berth is Superbird-8/DSN-1 - built by Mitsubishi Electric and operated by SKY Perfect JSAT and DSN Corp. under a dual-mission architecture. Commercial services are provided through Ku/Ka-Band, military comms use X-Band: http://bit.ly/2HbM0P1 

7 мин.7 минут назад

The satellite was originally planned to launch in 2016 but suffered an overpressurization within its transport container when traveling to French Guiana, necessitating extensive refurbishment and re-testing. This led to a delay of nearly two years.

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04/05/2018 23:59 Stephen Clark

Minus-30 minutes. The Ariane 5's first and second stages should now be loaded with cryogenic liquid hydrogen and liquid oxygen propellants.

Спойлер

The 17.7-foot-diameter first stage's Vulcain 2 engine burns 149.5 metric tons, or about 329,000 pounds, of liquid oxygen and 25 metric tons, or about 55,000 pounds, of liquid hydrogen. The cryogenic upper stage's HM7B engine consumes about 14.7 metric tons, or more than 32,000 pounds, of oxygen and hydrogen.

The fluids are stored at super-cold temperatures and naturally boil off in the warm tropical atmosphere in French Guiana. More propellant is slowly pumped into the rocket for most of the countdown to replenish the cryogenic fuel.

The topping sequence ends in the final few minutes of the countdown as the fuel tanks are pressurized and the fueling system is secured.

Built by a consortium of European contractors led by Airbus Safran Launchers in Vernon, France, the Vulcain 2 engine generates up to 300,000 pounds of thrust during its 9-minute firing. It burns about 320 kilograms, or 705 pounds, of liquid oxygen and liquid hydrogen propellant per second.

The engine's nozzle has an exit diameter of 2.1 meters, or about 6.9 feet. It weighs more than 4,600 pounds and its liquid oxygen and liquid hydrogen turbopumps spin at 12,300 rpm and 35,800 rpm, respectively.

The Vulcain 2 replaced the Vulcain engine used on the initial version of the Ariane 5. The newer engine produces 20 percent more thrust.

The Ariane 5's upper stage is powered by an HM7B engine, a modified version of the HM7 engine used on the upper stage of the Ariane 4 rocket. The 364-pound HM7B engine is manufactured by Airbus Safran Launchers in Ottobrunn, Germany.

The HM7B engine produces more than 14,500 pounds of thrust in vacuum.

The Ariane 5 configuration with a Vulcain 2 engine and HM7B-powered cryogenic upper stage is known as the Ariane 5 ECA.

The Ariane 5's twin solid rocket boosters are packed with propellant near the launch site in French Guiana before they are assembled and positioned on each side of the cryogenic core stage.

With the rocket now fully fueled for launch, the vehicle weighs 1.7 million pounds. At liftoff, the rocket produces 2.9 million pounds of thrust.

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DutchSpace‏ @DutchSpace 1 мин. назад

22:59:00 [L-00:35:00] Preparation of the synchronized sequence #VA242

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