Hi it’s me, Tim Dodd, the Everyday Astronaut
It’s ALIVE!!!!!
For the very first time, the Falcon Heavy has successfully lit all 27 of its mighty
Merlin engines in preparations for its maiden launch.
Once it flies, the Falcon Heavy will be the most powerful rocket currently in operation.
SpaceX does a hold down test of all their rockets called a static fire and today we’re
going to give you a quick rundown on what that is, how it works, and why they do it.
Let’s get started!
Now that Falcon Heavy has successfully gone through static fire, hopefully we’ll have
a more concrete date on the calendar for it’s maiden launch.
Elon Musk even tweeted “Falcon Heavy hold-down firing this morning was good.
Generated quite a thunderhead of steam.
Launching in a week or so.”
Meanwhile, I’ve had a lot of questions about static fires.
SpaceX likes to test stuff.
Like, all of the stuff.
As a matter of fact, SpaceX avoids using anything that can’t be tested beforehand, like pyrotechnics
or explosive bolts and tends to rely on hydraulics and things that can tested before the launch.
This philosophy is repeated throughout the company and testing their engines and rockets
as a whole is no exception.
SpaceX has fired their workhorse Merlin engines over 5,600 times to date.
That’s a lot of a data.
Considering they’ve built hundreds of these engines, SpaceX has learned the limits of
the Merlin very well and feels confident that testing ensures no errors in manufacturing
and doesn’t cut into the lifespan of the engine any more than planned.
Don’t forget, the Merlin engine is designed to eventually be reused for several launches,
and SpaceX has continually evolved the engine to last longer and produce more power as well.
They first test fire each engine on its own at a test stand in McGregor, Texas to make
sure there are no issues in manufacturing.
They'll often test the single engines for the full duration of the mission, so around
2 and a half minutes for the Merlin 1D and 6 to 8 minutes for the Merlin 1D vacuum engine.
Then they take the engines back to their headquarters and manufacturing plant in Hawthorne, CA to
be integrated onto the bottom portion of the rocket, known as the octaweb.
The octaweb is then mated to the rest of the first stage core which is then shipped back
out to McGregor, Texas via a semi for a long duration static test fire.
They hold the rocket down via massive hold down clamps and perform around a one minute
test fire.
Occasionally you may see them use a cap with cables for additional support if they need
to test the vehicle longer.
Remember, the rocket weighs a lot when fully fueled!
So at first, the clamps only need to hold the difference between the weight of the rocket
and the thrust of the rocket engines.
But as the rocket burns up fuel, it gets lighter and the load on the clamps increases.
Once they’re sure everything is in good working order, they then ship the core out
to its launchpad, either launch pad 39A at Kennedy Space Center in Florida, Space Launch
Complex 40 at nearby Cape Canaveral Air Force Station or at Space Launch Complex 4 at Vandenberg
Air Force Base in California.
Once the rocket is at the launch site, they mate the first stage with the upper stage
and do one more shorter static fire on the launch pad to ensure everything is in good
working order, including ground systems, the vehicle and the procedures.
These static fires tend to last anywhere from 3 seconds to 7 seconds.
And although the video from SpaceX’s official tweet made it appear as though the static
fire was only around 6 seconds, more continual shots make it appear to last closer to 11 seconds.
This practice is fairly unique to SpaceX, but some other vehicles have done static fire
tests such as the Space Shuttle and Orbital ATK’s Antares.
Other companies, occasionally perform a wet dress rehearsal which is everything but the
firing of the engines.
The Falcon Heavy went through several wet dress rehearsals leading up to its actual
static fire.
Remember, there’s a lot of new things at play here, so practicing how to synchronize
loading three first stage cores, and checking their alignment and loads probably took a decent
amount of tweaking to get to where they’re very confident with the procedure.
Testing hardware this often is a little different philosophy than others in the space industry.
As a matter of fact, there’s some things that just simply can’t be tested before
they’re used in space because they can only be used once.
My favorite and most terrifying example, is the engine that got astronauts off of the
moon.
That’s right, the ascent engine on the Lunar Module Ascent Stage known as the APS could
only be used once because the fuel and oxidizer were so corrosive the engines had to be rebuilt
after each firing.
This means every sing engine that got astronauts off the moon had not been test fired before flight!!!
It’s one and only use was the life or death ignition on the surface of the moon.
That's terrifying!
So in regards to the Falcon Heavy static fire, there’s a few things we need to note.
First off, each of the three cores of the Falcon Heavy were already tested at McGregor
on its own, just like a standard Falcon 9.
But seeing as there’s three times as many things to fuel, check and ignite, there’s
a lot of new procedures taking place.
One of these procedures is the fact that the Falcon Heavy doesn’t actually light all 27 engines simultaneously
It was assumed that the Falcon Heavy would stagger the ignition of its engines, similar
to how the Space Shuttle staggered ignition of its RS-25 main engines.
Something you could only see in high speed film.
But that’s yet to be confirmed and they may have performed a different procedure during
for the static fire.
It appears as though the side cores were actually first followed soon after by the center core
as a way of staggering the ignition.
They do this so the engines don’t create too much torque thrust along the octawebs.
After static fire, the remaining fuel is then pumped out of the vehicle, rechilled and recycled
for next time.
And don't forget the two side core boosters of the Falcon Heavy are reused, meaning they've
already been to space and back, so they've gone through a lot of tests.
With SpaceX having static fired and launched so many vehicles, they’re continually trying
to speed up the process to be both more automated and quicker.
Since the Falcon 9 and the Falcon Heavy uses super chilled propellants, there’s only
a short window of time where the vehicle will operate within its full potential.
As the fuel and oxidizer warm up, they decrease in density which in turn decreases the performance
of the rocket.
The desire to speed up propellant loading, and decrease preparations is what led to the
AMOS - 6 pad anomaly on September 1st, 2016.
SpaceX used to do static fires with the payload on top, which was seen as a good way to reduce
launch preparation times since they didn’t have to integrate the payload after static fire.
If you want to know more about what went wrong during the Amos 6 pad anomaly, I suggest you
watch Scott Manley’s awesome summary of the events.
Static fires have a time window just like a launch and nearby roads are blocked off.
Personnel are kept miles away in case of an accident.
The eastern range or the western range run by the Air Force Station is there to make
sure there are no boats and planes within the exclusion zone as well.
Static fires.
Like a launch, minus the let go part.
We're one step closer to the first flight of Falcon Heavy!
I CAN'T WAIT!
Make sure you’ve watched my video all about Falcon Heavy so you know what to expect on
the maiden flight!
Let me know what questions you may have leading up to the inaugural launch of Falcon Heavy!
Will you be at the Cape to see it fly?
You’d better believe I’ll be there, streaming live!
As always thanks to my Patrons for helping make this and other Everyday Astronaut content possible.
I owe a special thanks to those Patrons in our exclusive discord channel who help script
and research.
If you want to help contribute please visit patreon.com/everydayastronaut Thank you!
Thanks everybody, that's going to do it for me, I'm Tim Dodd, the Everyday Astronaut,
bringing space down to Earth for everyday people.