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 back. This 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
