Spaceflight Insider

Expendable Falcon 9 launches Inmarsat-5 F4

KENNEDY SPACE CENTER, Fla. — Clear skies and a setting sun provided a stunning backdrop as SpaceX launched an expendable Falcon 9 with the last of four Inmarsat-5 Global Xpress (GX) telecommunications satellites.

The Falcon 9, in an increasingly rare expendable configuration, lifted off at 7:21 p.m. EDT (23:20 GMT) from Launch Complex 39A (LC-39A) and deposited the Inmarsat-5 F4 satellite into a geosynchronous transfer orbit (GTO) around 32 minutes later.

An expendable Falcon 9 soars skyward. About a minute into flight, the vehicle has passed though the area of maximum stress on the rocket. Photo Credit: Michael Deep / SpaceFlight Insider

An expendable Falcon 9 soars skyward. About a minute into flight, the vehicle has passed though the area of maximum stress on the rocket. Photo Credit: Michael Deep / SpaceFlight Insider

The 45th Space Wing, which manages all rocket launches on the Eastern Range, said in a statement: “We truly have a tremendous team on the Space Coast and it’s my honor to be a part of this mission supporting the commercial space industry and helping to bring flexible high-speed mobile broadband communications to maritime, aeronautical, enterprise and government customers.

“Today’s mission is just another example of our unwavering focus on mission success and guaranteeing assured access to space while showcasing why the 45th Space Wing is the Premier Gateway To Space.”


With only 14 days separating Inmarsat-5 F4 and NROL-76, which also launched from LC-39A, the pad infrastructure and ground crews showed no ill-effects of a quickening launch pace. Moreover, there were no issues leading up to the final minute of the countdown when the flight computer initiated its pre-launch checks.

Weather for today’s liftoff was predicted by the 45th Weather Squadron as having a 90 percent chance of favorable conditions. The only concern was cumulus clouds. However, those never materialized.

About three seconds from liftoff, the nine Merlin 1D engines ignited with a telltale green flash. The engines, which burn a mixture of liquid oxygen and a highly refined kerosene called RP-1, produce a combined 1.71 million pounds-force (7,600 kilonewtons) of sea-level thrust. This provided enough power to propel the rocket and the 13,000-pound (5,900-kilogram) Inmarsat-5 F4 satellite off the pad. The vehicle cleared the tower shortly thereafter.

Eventually taking a turn due east, the rocket and its payload began the steady climb to orbit.

As the vehicle accelerated, the forces experienced by the rocket – atmospheric pressure combined with velocity, a condition known as maximum aerodynamic pressure (max Q) – reached their greatest at approximately 77 seconds into the flight.


The first stage’s nine Merlin 1D engines continued to power the vehicle for nearly another 90 seconds, shutting down at 2 minutes and 45 seconds after launch, followed four seconds later by separation of the first and second stages.

Artist’s depiction of the Inmarsat-5 F4 satellite in orbit. Image Credit: Boeing

However, unlike most SpaceX launches nowadays, this was an expendable Falcon 9 and the first stage was not recovered. As such, there were no in-flight acrobatics from a returning booster orchestrating a series of flips and engine burns so that it could return safely for a ground landing or on a ship at sea.

According to SpaceX, mission requirements prevented a recovery attempt; therefore, the booster was allowed to splash down in the Atlantic Ocean, not to be recovered.

Shortly after stage separation, the second stage’s lone Merlin 1D-Vacuum (MVac) came to life. The vacuum-optimized engine – similar to the power plants on the first stage, but with a larger nozzle extension – continued to accelerate the stage and payload with its 210,000 pounds-force (934 kilonewtons) of thrust.

Nearly 40 seconds after the MVac ignition, the protective payload fairing separated from the second stage. Designed to protect the spacecraft from acoustic, thermal, and atmospheric loads during liftoff and flight, the fairing is no longer needed once the vehicle is above most of the atmosphere.

Separation at GTO

The flight profile for this mission called for two burns of the MVac engine, separated by a nearly 18-minute 20-second coast. The first burn, lasting just short of 6 minutes, placed the satellite in a temporary orbit.

“Inmarsat-5 F4 joins our existing Global Xpress constellation, which is already being adopted as the new standard in global mobile broadband connectivity by companies, governments, and communities around the world,” said Michele Franci, CTO, Inmarsat through a Boeing-issued release. “Boeing has been an outstanding partner in our journey to make Global Xpress a reality.”

After the coast phase of the flight profile, the MVac was ignited once more. This second burn, lasting less than a minute, placed Inmarsat-5 F4 in a geosynchronous transfer orbit.

Approximately four minutes after the completion of the second burn, and nearly 32 minutes after liftoff, the Inmarsat-5 F4 satellite separated from the second stage. The satellite will use its onboard propulsion system to raise its orbit to 22,236 miles (35,786 kilometers) above the equator.

“Our partnership with Inmarsat has enabled the creation of the world’s only commercial global, mobile Ka-band network,” said Mark Spiwak, president, Boeing Satellite Systems International via a release issued by the company. “This unique achievement is an example of Boeing’s continuing commitment to deliver reliable, affordable and innovative solutions for our customers.”

This marks SpaceX’s sixth launch of 2017, with their next launch, the CRS-11 Dragon capsule, scheduled for 5:52 p.m. EDT (21:52 GMT) June 1, 2017.

Video courtesy of SpaceX



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.

Reader Comments

Can you confirm that this payload was actually put into a ” supersynchronous ” orbit , with an apogee well ABOVE the final intended apogee of 22,300 miles give or take ? The satellite will incrementally raise its perigee in coming months, but use the energy from the much higher supersynch orbit to help do that. I think the initial GTO parameters whould show an apogee of something in the 35,000 to 50,000 mile zone if I recall how this technique works. It’s also explains why there was no fuel available for booster flyback since the idea is to generate the greatest amount of energy going uphill to bleed back to the final orbit.

I’m no rocket scientist but makes sense to me.

It seems recently that SpaceX’s launch schedule performance is tangibly improving relative to its marketing predictions.

That said, from the SpaceFlight Insider launch schedule, it appears they wish to launch the Falcon Heavy first (Demo) flight some time in the July-August time frame. Is there any other metric other than F9 flight schedule adherence to believe or predict, that SpaceX will hit that time window for the heavy-lift capability?

Matt McClanahan

July isn’t going to happen, August would be pretty optimistic. Before they can launch FH, 39A needs additional work done. This is a knock-on effect from the 2016 failure which diverted pad work from 39A to SLC-40.

In an effort to return to flight sooner than later, they postponed the FH-specific bits at 39A so that they could get it operational for F9 and return to SLC-40 repairs. Once that’s done, F9 launches can flip back to SLC-40,
and FH work at 39A can resume without conflicting with launch operations.

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