The first launch of the Starship super heavy was both a success and a failure, the success was the
rocket itself which did much more than Elon wanted and cleared the tower easily without blowing up
but in the process, it virtually destroyed the launch pad, which maybe was what Elon actually
feared might stop it from clearing the tower. Judging by the damage that the 15 odd million
pounds of thrust, if you factor in 3 engines not running, did to the pad it’s hard to
believe that no one at SpaceX didn’t expect something like this to happen, even though the
static fire test led them to false expectations. SpaceX has a large number of Ex NASA personnel,
and they will have been well aware that the power of Superheavy was well beyond the capabilities
of the Boca Chica site even more so with a very limited water deluge system and no flame trench.
Now many are saying that it doesn't matter and that it was never more than a tes t to
prove that the whole thing get off the ground and the damage can easily be repaired but if
they are to progress anywhere near to what they aspire to do they must have a proper
launch pad that is capable of handling what is the equivalent of two Saturn 5 strapped together,
again and again and again at intervals of maybe days or less without any major damage.
NASA launched 12 Saturn 5s and 82 Space shuttles and 1 SLS from Pad
39A over 56 years without any substantial damage,
so what can Spacex learn from NASA and hopefully do it better, cheaper and quicker.
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Whether or not debris thrown up from the launch pad at SpaceX’s boca chica location was the actual
cause of the Starship Superheavy’s ultimate demise is still a matter of conjecture that we might
not know the full answer to for some time. However, what is not in doubt is the damage
the thrust did to the concrete launch pad. Also keep in mind this was a normal launch
without any anomalies or explosions on the pad. If they were to launch again tomorrow
with a new rocket and pad of the same design then the same would happen again.
If you watch the launch you can see that at about 6 seconds, just the rocket starts
to lift off the pad, several huge pieces of what look like re-enforced concrete each at
least several meters in size are blown up along side the rocket to a height of about 200 meters.
Another view shows splashes in the sea just beyond boca chica beach as dozens of large
pieces of concrete are blasted up to 500 meters from the launch pad, but because there was no
flame trench to guide the exhaust, there was nothing to stop that debris from being ejected
to the same distance in every direction. The footage from cameras which was outside
the gate to the facility about 215 meters from the pad show the shower of concrete
and debris raining down and hitting a camera car before they are engulfed in a huge dust cloud.
That dust and sand started raining down on the surrounding area up to about 6 miles or 10km from
the pad within about 10 minutes of the launch. Just looking at the amount of concrete in sizes
ranging from pebbles to meter plus sized boulders that were blown up from the pad at probably near
supersonic speeds, it seems inconceivable none of that hit the rocket in some form or another and
possibly resulted in not only immediate damage to some of the engines but also the small explosion
and flames seen just above the main engines at T+29 seconds and T+33 seconds into the launch
and the shutdown of more engines slightly later. Why this happened is yet to be determined but
the super heavy booster did a static fire test in February 2023 which ran 31 of the
33 engines for about 7 seconds at about 50% power generating about 7.9 Million
lbs of thrust which is a little higher than the Saturn 5 which made 7.5 million lbs.
It is unknown if any damage occurred during the static fire test that weakened the heat
resistant high strength concrete known as FONDAG which was used to make the base of the launchpad.
If the concrete pad was compromised, then when the full power launch occurred it could have shattered
it rather than worn away abrasively. Once the concrete started to break up,
the extreme thrust would make its way through the cracks to lift it
from beneath and once the part of it was lifted the rest would follow. Once that
was out of the way there was nothing to stop it digging out the earth and sand beneath.
SpaceX said they had been working on a method that could have mitigated this three months ago. This
is a massive double-layer water-cooled steel plate that would cover the launch
pad area and could be kept cool enough for long enough to survive the launch.
However, it was deemed better to get the first test launch out of the way ASAP as the metal pad
wasn’t going to be ready in time. This would also need either a large pumping station or large water
tower to supply enough water to keep it cool. For whatever reason, SpaceX seems to have
concentrated on the rocket whilst treating the launchpad as an afterthought in order to get the
tests done but it has come back to bite them. So how has NASA been able to handle what was
the largest rocket launches ever made for the last 50 plus years up until the advent of the Starship
with only minor damage to the mobile launch Pad on the SLS launch and almost no issues prior to that.
Well, one thing both SpaceX and NASA facilities share is that they are next to the sea on land
which is just above sea level with a very high water table making digging out the
ground to make a flame trench very difficult and expensive but it’s not the only way to do it.
Back in 1961, the missile test site and launch site for the Mercury and Gemini
missions which was then called Cape Kennedy was chosen to be the launch
site for the Apollo missions and the largest rockets ever built at the time, the Saturn 5.
In total NASA acquired 141,336 acres of land for the additional launch facilities. Even though the
Saturn was going to be rated at 7.5 million lbs of thrust, they planned for the possible use of
rockets like the Nova with thrusts of 5 times that amount at up to 35 million lbs as well as
nuclear-powered rockets, both of which never came to fruition during or after the Apollo missions.
But now big rockets are back on the agender with the 17 million lbs thrust Starship.
Because of the large amount of fuel carried by the Saturn,
it was calculated that if it did blow up on the launch pad it would have the
equivalent explosive power of about 450 tons of TNT, about the same as a small
battlefield tactical nuclear weapon or about half that blew up the Port of Beirut in 2020.
So, each of the launch pads had to have a clear radius of 3.5 miles or 5.6 km around them which
is why the Launchpad 39A and B are that distance from the Vehicle assembly building.
When NASA acquired the land where pads 39A and B would be placed it
was a mixture of marshland or partly submerged of the intersection of the Banana and Indian Rivers
The main thing that NASA wanted was a flame trench to divert and control the exhaust from the Saturn
rockets at lift-off, this would direct it in a northeast direction towards the Atlantic ocean
and also divert some of the shock waves away from other nearby structures and fuel tanks. However,
because the ground was just above sea level or just below it, the water table was also very high.
This meant that if the launch pad was at ground level then the flame trench would have to be
dug into the ground to a depth of over 50 feet or 15 meters, keeping the water out
would become a very difficult and expensive job. So they decided to raise the whole launch pad and
build the flame trench under it at ground level. They dredged up 3.76 million cubic meters
of fill from the Banana river to fill the submerged areas and at the launch pad sites,
they built up truncated pyramids on what was merit island to a height of 80 ft or 24 meters.
This was left for several months to allow it to compress the soil underneath and make it
stable. After it had settled about 4 feet or 1.2 meters they removed the top of the giant sand pile
to bring it to a height of 55 feet or 16 meters for pad 39B and 44 feet or 12 meters at pad 39A.
The flame trench bisected the launch pad and had an inverted steel flame deflector directly
under the hardstand where the rocket would stand. That would deflect the exhaust down
the high-temperature brick lined concrete Shute and away from the rocket. The flame trench was
490 feet or 149 meters long, 58 feet or 17.6 meters wide and 42 feet or 12 meters deep.
To cool the flame deflector a water tower with capacity of 94,000 liters held enough water to
provide a flow rate of 188,000 litres per minute for 30 seconds. A second system provided cooling
for the flame trench and another for pad cooling and sound and shock wave reduction.
This is how NASA did it and it took 3 years to build and a lot of money
but the result has stood the test of time. The problem SpaceX face is they are using a rocket
with twice the power of the Saturn so maybe even the existing NASA pads might need some upgrading.
In 2014 SpaceX signed a 20 year lease for the exclusive use of pad 39A from NASA for
launches of the Falcon 9, Falcon Heavy and the Dragon 2 space capsule for eventual transporting
of crews to the International Space Station. In 2020 they started building what is almost a
copy of the Starship Boca Chica launch pad about 300 meters east of the main launchpad 39A. Elon
has said that they would like to launch all the NASA Artemis III missions from the NASA facility.
But with the performance of the pad at Boca Chica, NASA is less than happy at the thought of the same
thing happening at Pad 39A, as any damage could seriously impact the already busy launch schedule.
They could in theory use the NASA pad for Starship but because it has a different tower and
requirements, the Falcon would have to be moved elsewhere, possibly to where the Starship pad is
being built now or to another existing smaller pad elsewhere at the NASA site, adding more time
and money to an already very tight schedule. So back to Boca Chica, the addition of the
water-cooled pad plate may well save the pad from the damage we saw but without some form of flame
diverter and or better water deluge system, they still run the risk of further damage,
not just from the exhaust but the acoustic waves that this creates and that can resonate
with the body of the rocket and engines causing further unforeseen problems.
This is why they had the massive water deluge sound suppression system at the NASA pad 39A
in the shuttle days because these acoustic shock waves from the engines could damage
the shuttle’s payload. At the moment the exhaust just spreads out in every direction
which may be fine if they have some other form of deflector system but any they choose must
be able to withstand many launches without major rebuilding works on a regular basis.
Building a NASA-style pad might do the job but will be prohibitive from both a
cost and time perspective. It would mean a major change at Boca Chica and apparently,
SpaceX did apply to the Army Corp of Engineers to build such a pad but because of issues with
satisfying ecological requirements to allow dredging and pumping of what could be millions
of tons fill to build a raised launch pad near protected wildlife areas the application lapsed
and hasn’t as far as we know been reapplied for. After the last launch, the FAA will be mandating
many changes as well as enforcing mitigation strategies to reduce the ecological impact
of the launches and these will force SpaceX to consider its launch pad much
more than it has gotten away with so far. The Tank farm alone is only 100 meters from
the pad which took a hammering from the last launch. At Pad 39A the equivalent tank farm
is 370 meters from the main pad and much lower in height. Whether they can keep it at such a close
distance remains to be seen but it just looks like another problem that will have to be dealt with.
SpaceX have said that eventually, they want to be able to launch Starships several times a day
to bring the cost per launch to maybe just $10M instead of the $100M+, but for that,
they will have to have pads even more reliable than the NASA ones and this could to pose as big
an issue as developing the rocket itself if they don’t sort something out soon.