Ariane 5 set to launch Astra 5B and Amazonas 4A satellites tomorrow – UPDATE

Arianespace has cleared one of the European firm's Ariane 5 boosters to launch the Astra 5B and Amazonas 4A spacecraft tomorrow from Kourou, French Guiana. Liftoff is currently set for 7:04p.m. EST (22:04 GMT). Photo Credit: Arianespace

Jason Rhian

Arianespace is preparing to launch mission VA-216, the flight of the Astra 5B and Amazonas 4A satellites on the second Ariane 5 flight of the year for the Paris, France-headquartered aerospace firm. Liftoff is currently slated to take place from the Kourou, French Guiana spaceport at 19:04 p.m. EDT (22:04 GMT) on Saturday. Arianespace has approximately 58 minutes in the launch window to get the booster off the pad and on its way to orbit.

The launch had been scheduled for Friday. However, weather at the Spaceport in French Guiana tomorrow caused flight controllers to decide to push back the rollout from the Final Assembly Building to the pad by 24 hours.

This is not the first slip of the launch however. The flight of these two telecommunications satellites had originally been planned to take place in December of last year. The launch vehicle processing “flow” began for the 151 foot tall rocket in fall of last year. The Ariane 5’s cryogenic main “core” stage, avionics and two solid rocket motors were integrated and the rocket was ready to ferry its precious cargo to orbit.

Originally the Ariane 5 which was tasked with carrying the ABS-2 and Athena-Fidus spacecraft was supposed to launch first, this past January, with Astra 5B and Amazonas 4A conducting their flight in February. This however did not pan out due to issues with the VA-217’s second stage engine which required it to be swapped out. Other issues crept into the normal procedure and VA-216’s launch date was schedule for its current March 22 launch date.

The Flight Readiness Review (FRR) board had already given the green light for the launch to take place on Wednesday, March 19. The deteriorating weather conditions caused a reassessment of the flight. An FRR is conducted prior to any launch of the Ariane 5. During which, the readiness of not only the launch vehicle, payload and pad are conducted – but the spaceport and down range tracking stations as well. If everything proceeds according to plan, Saturday will see the 73rd flight of the Ariane 5 and the 217th launch conducted by Arianespace.

Ariane 5 is rolled out one day prior to launch to what is known as the “Ensemble de Lancement Ariane” – more commonly referred to as ELA-3. Once at the pad, normal pre-launch procedures will take place. The rocket will be hooked up to the various communications and essentials to ensure that it is primed and functioning properly before lifting off the pad.

The first stage’s Vulcain engine burns a mixture of liquid oxygen (LOX) and liquid hydrogen. The cryogenic main stage is comprised of a 100 foot tall (30 meters) tank which has two compartments, the first carries the 130 tons of LOX, the other the 25 tons of liquid hydrogen. Even when dry (empty) this part of the first stage weighs in at a hefty 15 tons.

Affixed to either side of the Ariane 5 are two Étages d’Accélération à Poudre, or “EAPS.” These solid rocket motors provide the extra push needed to thrust the launch vehicle and its cargo out of Earth’s gravity well.

If the engineers have done every thing correctly? The following should be what one can expect to see come launch time. Almost five hours prior to launch, the 310,000 lbs of rocket fuel will be loaded onto the Ariane 5. 260,000 lbs of which is LOX, the remainder is liquid hydrogen.

Four minutes before launch, the fuel tanks will be brought up to flight pressure. Ariane 5 will then be placed on internal power. Engineers will peer over every last bit of data to see if anything is even remotely “off-nominal” (out of the ordinary).

When the clock hits zero, the Vulcain will announce its presence to the surrounding jungle. It will continue to do so from the ground until about eight seconds at which point it should receive the go-ahead from the rocket’s computers that everything is functioning as advertised. At this point the two EAPS will be ignited. Each of which will unleash almost one-and-a-half million pounds of thrust. Less than 10 percent of the thrust needed to get the rocket on its way is provided by the Vulcain.

At about 4.5 seconds into the flight, Ariane 5 will conduct its pitch and yaw program so as to place it on the proper azimuth to place its two payloads in orbit. One minute into the flight and the rocket will be passing through “max q” the point in the flight where the launch vehicle’s speed conspires with the pressure of the atmosphere and places the rocket under the greatest amount of stress. The Ariane 5 will be traveling supersonic at this point – faster than the speed of sound.

Two minutes and 23 seconds into the mission, the two EAPS will have been jettisoned and will tumble back to splash down in the ocean. Although they can be recovered, they normally are not, sinking down into the Atlantic (occasionally EAPS are equipped with parachutes so as to bring them back for review and study – but they are not reused). No one is in danger of being struck with the two spent motors as they crash somewhere between 280-320 miles away from the launch site.

After clearing much of Earth’s tumultuous atmosphere, the payload fairing which the two spacecraft were safely cocooned in on ascent – will be jettisoned. This should take place at about three-and-a-half minutes into the flight.

Just shy of nine minutes elapsed time, the Vulcain engine will shut down and mark the “staging” point of the launch. The core stage will separate from the second stage where it too will impact the ocean – the core stage however, having traveled farther and faster than the EAPS – will impact off the African Coast.

The task of completing the delivery of the spacecraft to their destinations falls to the second stage and its Aestus rocket engine. Aestus is capable of being restarted. It provides an estimated 6,100 lbs of thrust.

At this point in the flight, Astra 5B and Amazonas 4A will be more than 100 miles above the surface of the Earth. They should achieve Geostationary Transfer Orbit and a speed of 5,700 miles per hour some 24 minutes after liftoff.

The orbit planned for the two spacecraft extends out to 22,205 miles (apogee) and 155 miles at their lowest (perigee). The first of the duo to be deployed from the SYLDA (Système de Lancement Double Ariane) payload carrier will be Astra 5B. This should occur 27 minutes after liftoff. Amazonas 4A will follow about eight minutes later. All total, the flight – from launch to deployment will last about 47 minutes.

The Rocket:

The Ariane 5 is a two-stage rocket which conducted its first flight back in June of 1996. As with so many new launch vehicles – it was not a successful launch with the rocket self-destructing less than a minute into the flight. The Ariane V is of a similar class to the U.S. Delta IV Medium, Atlas V and Falcon 9 family of launch vehicles.

Astrium, an EADS company, is the prime contractor on the Ariane 5 which has been used to launch deep space missions such as Rosetta as well as all of four the European Space Agency’s (ESA) Automated Transfer Vehicles (ATV) which have currently flown to the International Space Station. The Ariane 5 is described by Arianespace as being capable of lifting payloads weighing more than 10 metric tons to geostationary transfer orbit (GTO) and over 20 metric tons into low-Earth orbit (LEO).

The Spacecraft:

Astra 5B was built by Airbus Defence and Space for SES. It will orbit at 31.5 degrees east. It is based off the Eurostar E3000 platform. As it is designed for telecommunications purposes, it is equipped with some 40 Ku-band and 6 Ka-band transponders. Astra 5B will be the 56th satellite in SES’ fleet.

Amazonas 4A, which will occupy the lower rack on the SYLDA, was built by Dulles, Virginia-based Orbital Sciences Corporation. Amazonas 4A has 24 Ku-band transponders. It will be controlled by HISPASAT and orbit at 61 degrees west.

Saturday’s launch comes at a time when Arianespace faces growing competition from Space Exploration Technologies (SpaceX) as well as International Launch Services, these two launch service providers were detailed in a recent interview appearing on SpaceFlight Now as developing systems which actively compete with those provided by Arianespace. Two more Ariane 5 flights are planned for this year including ESA’s Georges Lemaitre ATV scheduled to launch in July.

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