Curt Godwin

June 28th, 2017

Ariane 5, Flight VA238, launch. Image Credit: Arianespace webcast

After a minor technical glitch interrupted the countdown for five minutes, Arianespaces Ariane 5 rocket left the pad at the Spaceport in Kourou, French Guiana, at 5:15 p.m. EDT (21:15 GMT) on June 28, 2017. Flight VA238, as the mission was named by Arianespace, deployed two satellites Hellas Sat 3 / Inmarsat S EAN and GSAT-17 into a geostationary transfer orbit (GTO) 39 minutes after lifting off, completing the fourth Ariane 5 launch of the year.

Ariane 5, Flight VA238, ascends from the Spaceport in French Guiana on Arianespaces seventh mission of 2017 with Hellas Sat 3-Inmarsat S EAN and GSAT-17 aboard. Photo Credit: S. Martin / ESA / CNES / Arianespace

While tropical thunderstorms threatened to delay the mission, conditions improved enough to allow for an (almost) on-time launchat five minutes after the opening of the 77-minute window.

At T-minus 0 seconds, the core stages Vulcain 2 engine roared to life. Approximately seven seconds after main engine ignition, and after passing health checks and allowing the main engine to reach flight thrust levels, the flight computer signaled the twin P241 solid rocket boosters (SRBs) to ignite.

The output from the triowas more than enough to lift 20,408pounds (9,257 kilograms) of satellites, plus the mass of the rocket and its propellant, off the pad.

With a combined 2.92 million pounds-force (13,000 kilonewtons) of liftoff thrust, the 180-foot (54.8-meter) tall Ariane 5 climbed fromthe pad and soared into a cloudy nighttime sky, with the roar and crackle from the three engines echoing across the jungle.

Shortlyafter clearing the launch tower, the Ariane 5turned eastward and climbed over the Atlantic Ocean.

As the rocket climbed and gained velocity, atmospheric pressure reached its maximum impact on the vehicles structure. This region of high stress is called max Q and is a function of the vehicles speed combined with the pressure exerted on the rocket by the surrounding air. At nearly the same time, the Ariane 5surpassedMach 1 the speed of sound as it continued its rapidlyacceleratingclimbto orbit.

After passing through this part of its flight profile the most stressful on the rocket throughout its ascent the dynamic forces began to rapidly dissipate.

Slightly more than two minutes after ignition, and at more than37miles (60 kilometers) in altitude, the Arianes pair of solid-fueled boostersexhausted their propellant and were jettisoned. Unlike the boosters from the now-retired U.S. Space Shuttle program, the spent motors were not recovered after splashing down into the Atlantic Ocean.

Though only operating for marginallymore than two minutes, the SRBs accounted for more than 90 percent of the Arianes thrust at liftoff. However, with the vehicle weighing significantly less than it did on the pad, the core stages Vulcain burning through approximately 700 pounds (317.5 kilograms) of fuel and oxidizer per second was able to supply the power necessary to continue accelerating the lightened rocket and its payload.

Approximatelythree-and-a-half minutes into the flight, and at68 miles (110 kilometers) in altitude, the Ariane jettisonedits 55.8-foot (17-meter) long protective payload fairing. Though the aerodynamic shell protectsthe vehicle and its payload from acoustic, aerodynamic, and thermal stresses in the lower, thicker parts of the atmosphere, it becomes unnecessary mass and a barrier to payload deployment once in the vacuum of space.

The Vulcain main engine powered the vehicle for nearly nine minutes, and, once the core stage was depletedof its liquid oxygen (LOX) and liquid hydrogen (LH2) propellant, itseparated from the ESC-A (second) stage and fell into the Atlantic Ocean off the coast of Africa in the Gulf of Guinea.

The ESC-As highly efficient HM-7B engine, burning a cryogenic mixture of LH2and LOX, startedits 16-minute long burn to place the two satellites in their intended GTO delivery spot.

Twenty-eightminutes after lifting off, the ESC-Awas in a position to deliver the first of its two passengers to the 155-mile (250-kilometer) by 22,236-mile (35,786-kilometer) transfer orbit.

Hellas Sat 3 / Inmarsat S EAN was the first of the satellites to separate from the vehicles SYLDA payload adapter. After the Thales Alenia Space-built satellite was clear and at a safe distance, SYLDA was jettisoned, exposing GSAT-17.

Following a short coast, the Indian Space Research Organization (ISRO) GSAT-17 satellite was free to deploy.

Both satellites will raise their orbit with their onboard propulsion system while undergoing a set of checkout procedures by theground crew before being declared operational.

Flight VA238 marks the seventh overallmission for Arianespace in 2017, with fivemore left on the manifest for the year. Coming next for the French multinational launch provider is the launch of their lightweight Vega launch vehicleon Flight VV10, carrying Optsat 3000, scheduled for July 25, 2017.

Video courtesy of Arianespace

Tagged: Ariane 5 ArianeSpace GSAT Hellas Sat Inmarsat Kourou French Guiana Lead Stories Urgent VA238

Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.

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Arianespace closes the first half of 2017 with launch of Flight VA238 - SpaceFlight Insider