SpaceX SES-9 Mission Overview

26th February 2016 at 11:29pm UTC,

Space Launch Complex 40, Cape Canaveral, Florida, Earth

It is the second launch of the upgraded Falcon-9 rocket, Falcon-9’s first GTO mission, first attempt to try to land on a droneship and I will be writing about the special challenges of that landing. I will also be writing about the SES-9 Spacecraft and about the upgrades that were made to the pad in order to launch this more powerful rocket.

Let’s do a brief walk-through of what we’re looking at:
  • Firstly, the upgraded rocket itself and the Space Launching Complex.

  • Rocket first stage (bottom part): Carries the satellite up to the edge of space, about a 100km high, moving at about 2,5 kilometers/seconds (at the time of separation). (Usually it’s lower of that about 2 km/s for some lower Earth orbit.)

  • Interstage (second stage): Going to carry the satellite, speed it up, and carry it further towards to geostationary orbit, which is its final position that is going to.

  • Payload (top): The fairing, or the nose cone, which is made of a carbon composite structure that actually holds the satellite inside of it.
  • Just next to it, there is the transporter erector or the strong backThis is what actually carries the Falcon-9 out from the hangar to the launch pad, and then raises it up to its current position.

  • There are several lightning towers surrounding it. Florida is one of the lightning capitals of the world, and these safely direct that energy to the ground, instead of affecting some of the sensitive electronics there that are actually on the vehicle.

The launch will be a potential autonomous space-board droneship landing. After the first stage, the second stage separates, the first stage will be continuing on a ballistic trajectory towards the “Of Course I Still Love You” droneship.

About the SES-9 Satellite:
SES-9 is the 9th telecommunication satellite in the SES family, and the second SES satellite that SpaceX is putting into orbit. They will be delivering SES-9 to GTO (Geostationary Transfer Orbit) at about 38000km high (or even higher). After they drop off the spacecraft, it will use it's on board thrusters to adjust its position and to transfer from GTO into its final Geostationary Orbit.
Geostationary Orbit is so high up that it orbits the planet at about the same speed that the Earth rotates, and this makes the satellite appear like a star in the star. So it is going to be a fixed point in the sky, whenever you look up.

Let's compare this to the ISS (International Space Station) which is in low-Earth orbit, at about 300km, which is much closer to the Earth, therefore it means that the GTO orbits much faster, this is why you can see that star moving, when you look up at the sky, and you can actually see the Station transmitting across the sky. They will be dropping SES-9 over a 100 times as higher as the ISS is. To get that high, a lot of propellant is needed. They are not going to have a tonne of it left over in the first stage, they're flying back down to the droneship. In given the needs, use every single last drop of that remaining propellant to burn the Falcon-9 engines to slow it down and orient it onto the droneship, this landing attempt is going to be one of the most challenging one.
The launch window for the launch day is 96 minutes long, and the reason for that is because as the Earth rotates, the final orbit of the target that they're trying to drop the satellites up to, isn't a fixed distance from the launch-pad, which means that there is a certain window where you can get to the same destination easier than others. If they had to try the launch outside of that 96 minute window, they'd run the risks of not having enough propellant to get them to a desired orbit. Within that window, SpaceX can make as many attempts as necessary.
If they have to hold the countdown between the time of liquid oxygen loading and T-0, they'll scrub for the day, and will try again on another day. It takes probably more than the time they have in the window to offload the cold liquid oxygen and load a new batch on board.

Let’s learn a bit about the satellite technology:
SES is one of the world’s largest satellites communication companies and with over 50 satellites in orbit. They are based at Luxemburg, in Europe. SES-9 is the latest satellite in their fleet and they have planned to launch 7 more satellites between now and 2017. SES-satellites offer all kinds of service, internet coverage, date services for mobile phones, airplane wifi, SES also broadcasts 7000 TV channels, more than any other media broadcasting in the world. They have satellites that they can mobilize in just 24 hours to help with disaster communications, with satellites that enable internet access in rural areas all around the world.
For today's launch, Falcon-9 is going to put SES-9 satellite at the highest possible orbit as it can, currently targeted for around 38000km or even higher. Then after it is separated from Falcon-9, SES will use its on board, liquid propellant thrusters to perform any major launch maneuvers or adjustments. A little it will use its electrical propulsion system to help finding its final position in GTO.

About the launching process:
SpaceX team monitors the temperature of liquid oxygen. It is important to keep the liquid oxygen cold enough under the rocket, especially in the second stage. When the team has the go/no go poll, they verify that everybody is ready to enter the launch out of sequence and begin propellant loading. Next step is a precision timing sequence between the ground computers and the Flacon-9 flight computers. They want to test as much as they can, as close to launch as possible, to make sure  that everything is working. So if that ends, the're moving the throttle valves on the engines. These set the power of the engines, so they are moving them to arrange the motion, to make sure if they are working. They're also setting the gimballing of the engines, making sure the actuators and the sensors are all connected and that the engines are able to steer the rocket throughout the flight.
In accordingly about T-10 minutes, the pre-valves will be opened and began chilling in the first stage engines. Getting the Merlin turbo pumps ready for the cold temperatures at ignition, just a couple of seconds before T0 (liftoff time).
When the Falcon-9 goes from ground power to internal power, it is possible to see the clamp arms, opening up on the second stage. The erector will then start to move always from the vehicle, that happens at T-4.5 minutes. Liquid oxygen loading is going to finish loading on the Falcon-9, between T-3 and T-2 minutes.

Upgrades made to the launch-pad system:

These upgrades allows the team to further improve the reliability at once with better processing time than ever before. One of the upgrades they have made are to the hold-down system, the hold clamps that physically hold the rocket to the ground while the engine comes up to full power. Right next to those hold-downs are the quick disconnects, these hold the electrical lines and the fuel plumbing that connects to the vehicle. They have made adjustments to those quick disconnects, changing the type of springs that they were using there so that they are not susceptible to a particular failure modes. 
The second big upgrade they have made is a much bigger increase of surge of liquid oxygen. As you know the rocket runs on liquid oxygen and RP-1 kerosene fuel and both of these fuels need to be as cold as possible before they are loaded into the rocket. The whole point of adding all of these capacity is to shorten the recycle time, which is the time it takes to completely empty and reload the rocket. Previously they just had one sphere that held the whole liquid oxygen (on Apollo testing). Now they have two much longer cylinders that keep that RP-1 at super cold temperature, and they have the ability to fill the first stage in 30 minutes.
They have also made upgrades to the transponder erector because the Falcon-9 is longer and heavier, and has a more powerful engine, they had to add blast place to the bottom, so that the transporter erector does not melt at the base.
They have also added more counter weights and more powerful lift cylinders, so they can have heavier payload on top of the Falcon-9 and still raise it to launch position without any problems. 

About the Mission Timeline:
On the spacecraft site, the SES spacecraft is gone on internal power. The range is good, the upper altitude winds are good.
At T-5 minutes accounting, everything seemed good.

At T-01:41, the SpaxeX team had to call for “hold-hold-hold” that stopped the count-down.

They were in the middle of propellant load, they were just loading up liquid oxygen on first and second stage. Falcon-9 was not in any significant concerns, static fires were revealed and lit down the engines and in additionally shut them down and then drained propellants.
The rocket then come back and the launch  was postponed for couple days later. 

Wish to see a successful launch in the near future.

Reference used:
  • SpaceX.com
  • SES-9 Full Webcast, narrated by: Lauren Lyons - Mission Integration Engineer, Michael Hammersley - Materials & Process Engineer, John Insprucker - Falcon 9 Product Director, Tom Praderio - Firmware Engineer

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