Falcon 9 Launches with SES-11; Completing its Second Double-Header

By Kai Farrimond

Falcon 9 launch on a late-Wednesday evening for the second time in three days, successfully sending the SES-11/EchoStar 105 satellite to Geostationary Transfer Orbit.

This launch came just 58 hours after the Iridium-3 Launch from Vandenberg Air Force Base, marking the second quickest turn around between two SpaceX launches. (The medal for first is held by the turnaround between BulgariaSat-1 and Iridium-2 back in June of this year.)

Payload

Although the name suggests otherwise, the SES-11/EchoStar 105 Satellite is actually one satellite. The satellite is owned by SES who will rent out transponders on the satellite to EchoStar, making it a joint-organisation satellite. The payload weighs in at 5200kg at launch, quite near the upper limit for Falcon 9’s reusable GTO capacity.

Once in Geostationary Orbit, the satellite will provide Ku-band and C-band capabilities to North America.

Booster Reflight

The First Stage of this mission was originally launched SpaceX’s 10th Commercial Resupply Services Mission (CRS-10) in February of this year. Following a successful first burn, the booster, B1031, performed a landing at Landing Zone 1 in Cape Canaveral.

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CRS-10 Landing, February 2017

Following the landing, the booster was secured and took into a hangar where it underwent refurbishment and a long series of checkouts and testing to confirm that it was in good condition for re-flight.

Following this, the booster was took to the LC-39A Horizontal Integration Facility where it awaited the arrival of the Second Stage. Once the stage arrived, they were mated together and integrated to the TEL. The TEL is responsible for rolling out the Falcon 9, taking it to the vertical position, and keeping it structurally stable until a few minutes before launch. Hence the name; Transporter Erector Launcher.

Launch Campaign

On October 2nd, Falcon 9, lacking its payload, rolled out of the HIF to the 39A Pad. Here it went vertical and ran through a full countdown dress rehearsal. When the clocks reached T-0, the nine Merlin Engines on the First Stage ignited for the first time in 8 months, for just 7 seconds. Once this was complete, the vehicle was de-tanked of its Rocket Propellant 1 and Liquid Oxygen propellants and rolled back into the HIF around 400 metres away.

Shortly after the Static Fire, SpaceX announced that the SES-11/EchoStar 105 Mission was delayed from October 7th to October 11th, without specifying the cause. We now believe this was down to a combination of an Atlas V launch with NROL-52 being delayed, and an engine leak on the Falcon 9.

Over the 9 days following the Static Fire, SpaceX engineers worked on securing the SES-11/EchoStar 105 payload to the Falcon 9.

Once this was complete, about 24 hours before the launch, the vehicle was rolled out to the pad yet again and erected into the vertical position.

Launch

At around T-3 Hours, the area around Launch Complex 39A was evacuated and the vehicle entered the ‘business end’ of the countdown.

At T-78 Minutes, Rocket Propellant 1 began to load onto the vehicle, followed by Liquid Oxygen at T-35.

At T-7 Minutes, Liquid Oxygen from Falcon’s First Stage tank began to pass through the turbo-pump on each of the 9 Merlin Engines, getting them ready for ignition.

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At T-5 Minutes, the tanks on Falcon pressurised to a level where the TEL was not necessary to support the vehicle anymore and at T-4, the arms that cradle the Second Stage were opened.

Shortly after that, the Strongback (TEL) began to retract. Over the next 2 minutes, it slowly reclined away from the rocket to the 88.5° position.

At T-2 Minutes, the vehicle transitioned to internal power, and it was no longer relying on ground-side batteries. The LOX load on Stage 2 also ended at this point.

At T-60 Seconds, the AFTS was announced to be ready for launch and the Falcon 9 Flight Computer entered what is known as startup. The Launch Director also announced that all systems were go for launch.

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At T-50 Seconds, the Second Stage was pressurised for flight.

At T-3 Seconds, the 9 Merlin 1D engines began their ignition sequence by first using the TEA-TEB Ignition System and then at T-2, Igniting the Engines.

At T-0, Four clamps holding down the rocket were released and the Falcon 9 and SES-11/EchoStar 105 Satellite left the pad.

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At T+1 Minute, 10 Seconds, the vehicle passed through Max-Q. This is where the maximum stress is applied onto the vehicle.

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At T+2 Minutes, 35 Seconds, the 9 Main Engines shutoff and a few seconds later, the First and Second Stages separated.

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At T+2 Minutes, 48 Seconds, the Second Stage Engine, Merlin Vacuum (MVAC) Ignited and the Second Stage began its powered flight.

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Shortly after, the fairing around SES-11 was separated due to it no longer being needed in the upper layers of the atmosphere.

At T+6 Minutes, 30 Seconds, the First Stage began its Entry Burn. As this was a GTO Mission, there was no Boostback Burn as the payload needed as much fuel as possible to get to its destination.

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The burn then shutdown 10 seconds later, followed shortly after by LOS on Stage 1.

 

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The three-engine landing burn began at T+8 Minutes, 13 Seconds, followed by touchdown on the deck of ‘Of Course I Still Love You’ at T+08:29.

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SECO-1 occured 12 Seconds later and the vehicle entered a roughly 20 minute coast phase.

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At T+27 Minutes, 13 Seconds, the MVAC Engine re-ignited for just short of 60-seconds to place the payload into a Geostationary Transfer Orbit.

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Following the burn, the Second Stage entered a final, 8-minute coast phase before deployment of the satellite.

At T+36 Minutes, 11 Seconds, the SES-11/EchoStar 105 Payload was successfully deployed, marking the end to another successful Falcon 9 Mission.

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Up Next

Next up for SpaceX is the Koreasat-5 Mission on October 30th. Static Fire is currently scheduled for October 26th from Launch Complex 39A. If repair work on LC-40 continues as expected, this launch may be the last from LC-39A before its final conversion work for Falcon Heavy and the re-activation of Launch Complex 40 following the AMOS-6 mishap in September 2016.

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