They were seen on the most significant missions like Apollo, Skylab, the Space shuttle, they’ve been used for the SpaceX Falcon Heavy and they’ll be there on the upcoming SLS missions but they are hardly ever talked and without them, we simply wouldn’t be able to get the rockets off the ground. What are they?, they were the gateway to the moon and starting point for every Space Shuttle mission, NASA launchpads 39A and 39B, so just what do these massive feats of engineering do and just how important are they ?.
NASA has over 40 launchpads in various locations from the US mainland to the Pacific, their position is chosen to best get the spacecraft into the correct orbit and to be safely away from population centres. Cape Canaveral in Florida is better for launching spacecraft requiring a west-east orbit and others like Vandenberg in California are preferred for spacecraft requiring a north-south orbit.
But where ever they are, the launchpads themselves are vitally important pieces of equipment for first and foremost holding the rocket vertically, which is no mean feat when you consider the size of the Saturn V which at launch weighed 2,938 tons and stood 17.6 meters taller than the statue of liberty at 110 meters, the same as a 36 story building.
The Launch complex at Cape Canaveral started its rocket career in 1948 after the Naval air station there was transferred from the Navy to the Airforce for testing of captured German V2 rockets. This went on to testing missile and rocket technology through the 1950s until NASA was formed and it became future for manned and unmanned missions including Projects Mercury and Gemini.
In 1961 when President Kennedy announced the moon missions, Cape Canaveral was chosen to be the base for Apollo, this also meant that it would need a massive expansion with NASA taking over an extra 550 square km of land and launch complex 39 would be designed to handle the most powerful rocket yet designed, the Saturn V.
Work started in 1962 and was completed in 1965. There were to be 3 launchpads 39A, B and C and then two more, D and E later. In the end, only two ended up being built and named 39A and just north of that, 39B.
Because the area is just above sea level the flame trenches could not be placed below ground level due to the water table being very close to the surface, so the launchpads are raised by 13 meters and look like concrete hills.
Because of the way NASA designed the Saturn V, there was no permanent Launch Umbilical Tower at the launchpad. That’s the part which is next to the rocket at take-off and supplies it with fuel, electrical power and access for the crew.
Instead, the Tower was integrated into a Mobile Launcher Platform. The Saturn V would be assembled directly on to the platform along with the tower. This was part of NASA’s assembly schedule that meant that the rocket was assembled vertically and then moved along with its Tower to the launchpad. This contrasts with the Soviets which assembled their rockets as they lay on their side and moved them to the launch pad horizontally where they were then lifted to the vertical position before launch.
Now you may well ask, why did NASA choose vertical integration and the Soviets horizontal. Well, when the Saturn was being designed it was thought that even bigger rockets like the NOVA would follow. NASA concluded that it would be easier to assemble the rocket vertically directly on to a Mobile Launcher Platform and move the whole thing to the launch area rather than assembling and moving it on its side and then lifting up at the launchpad. This was because they thought the engineering challenges of lifting a 110 meter or larger rocket were just not worth it and that it would place too much stress on the body of the rocket.
Now some of you will be saying that the Soviet N-1 was almost as big as the Saturn V and that was a built horizontally and cranked up to the vertical position, but it also required a huge mobile complex structure to lift it and it was moved on two parallel railway lines with two locomotives.
Building the Saturn vertically required the largest single-story building in the world. The VAB or Vehicle Assembly Building is 160 meters tall and this is where the new SLS rocket will also be assembled. Built between 1962 and 1965 the VAB was capable of preparing up to four Saturn V’s at the same time and each of the four doors are the largest in the world to allow a complete Saturn rocket assembly to go to the launchpad.
For Apollo, the prebuilt sections of the Saturn V were delivered to the Vehicle Assembly Building from around the US, where they were stacked on top of each other to form the rocket. On the Saturn V, the rocket was held down to the launch platform by massive hold down arms which would release at launch, were as the Shuttle was bolted down to the platform through the Solid Rocket Boosters using flangable nuts. These are nuts which are explosively split at lift-off rather than using explosive bolts.
In order to get the rocket and the Mobile Launcher Platform from the VAB to the launch area there are two crawler-transporters which drive under the Mobile Launcher Platform, lift it up and move it to the launch complex. When these 2700 ton vehicles were delivered in 1965 for the Apollo program they were the largest self-powered land vehicles in the world.
Not only do they carry the rocket and the Mobile Launcher Platform at about 1.6km/h they also keep the whole assembly level as it ascends the 3% ramp to launch pads 39A and B. Its laser guided levelling system could keep the top of the Saturn V within 30cm vertically of the base. Once the Mobile Launcher Platform has reached the launchpad it is set down and the crawler-transporter returns to the Vehicle Assembly Building and no it doesn’t need to do a massive 3 point turn, it can be driven from both ends so it just returns the way it came.
Even the road that connects the VAB to the launchpad, known as the crawler way had to be specially built with a very low friction surface due to the weight of the rocket, launch platform and crawler that came in at 8,165 tons. The material chosen was Alabama river gravel for its unique combination of qualities and it is still in use today.
With the Apollo launches, the Saturn V was attached to the Launcher Platform and the Launch Umbilical Tower or LUT. Although it looks like the tower is holding the Saturn up, that was done by the hold-down arms at the base. The tower is actually there to supply fuel, electrical power and crew access via the nine service arms, which can be seen swinging away from the rocket at launch.
At the top of the LUT was the crew access walkway and the white room from which the crews would then enter the command module. The Pad leader for every manned Apollo mission was Guenter Wendt. He would perform the final checks, strap the crew into the capsule, shake their hands and offered words of support and then close the hatch.
The last major piece of infrastructure was the Mobile Service Structure (MSS), this was a large lattice-like platform that was also moved around by the crawlers. At the top of this which was a little shorter than the Launch tower, was a section that would completely enclose the top of the Saturn V and the command module to provide weather protection and access for technicians as well as a clean room for preparations before the flight.
The Mobile Service Structure was also used to place the linear explosive charges that would separate the stages in flight and the charges along the fuel and oxidiser tanks for “fuel dispersion” in the event that the rocket had to be destroyed if it veered off course during the launch. The MSS would be moved away from the Saturn 8 hours before the launch and parked between pads 39A and B on the crawler way when not in use.
One of the other jobs that the Launcher Platform had to do when it was in position was to precisely match up with the pipework for the fuel and electrical supply system, which can be seen running up the LUT. The fuel which the Saturn V used was RP-1, a highly refined version of kerosene and LOX or liquid Oxygen. This was for the first stage and Liquid Hydrogen and liquid Oxygen were used for the second and third stages, this was pumped onboard whilst the Saturn was at the launchpad. Other hypergolic fuels, those that combust on contact with each other were also pumped onboard at this time and were for the ignition of the F1 engines and for the lunar lander’s descent and ascent engines.
In the event of a problem like a major fuel leak whilst the Saturn was being prepared and providing that it didn’t just blow up on the spot, technicians and crews were trained in an escape procedure that uses a special high-speed elevator that would get them from the top of the launch tower to the launcher platform in under 30 seconds.
From there they would slide down a 61-meter deceleration slide to the rubber room 12 meters under the launch pad and so called because it was lined with rubber as a shock absorber. This antechamber led via 15cm thick steel blast door to a dome-shaped blast-proof room mounted on giant springs that were designed to withstand the explosion of a fully fuelled Saturn V on the launchpad above. This room could hold up to 20 people with food and water and an air filtration system for 24 hours. Each of the seats could hold a fully suited astronaut until such time it was safe to leave the room via an escape tunnel that emerged some 366 meters away from the pad.
Now the launch platform under the rocket was not a flat surface, it had a 13.7-meter blast shielded square hole for the rocket exhaust which allowed it to pass down and over the flame deflector. This double-sided ramp is there to deflect the exhaust and stop it coming back up and enveloping the rocket. The 13-meter high ramp which was covered in flameproof concrete and mounted on rails so it could more easily be replaced, deflected the exhaust down the two 18 meter wide flame trenches which stretched 174 meters and also were made from concrete and lined with refractory bricks to protect is from the heat.
The huge amount of smoke seen at launch isn’t rocket exhaust. It’s mostly water from the deluge system flashing to steam from the heat of the exhaust. This water was pumped on the on to the Launch Platform just before lift-off to help protect the platform and also act as an acoustic dampener.
In 1974 launchpad 39A was decommissioned and was reconfigured for the space shuttle, the same happened to pad 39B in 1977. The reason for the 3-year gap was just-in-case congress reinstated the Apollo program.
Pad 39B wouldn’t be used for the shuttle until 1986 when its first mission was the ill-fated Challenge STS-51.
After the Apollo missions, the Mobile Launcher Platforms were redesigned for the shuttles. The Launch Umbilical Tower was removed and a permanent two-piece access tower system, the Fixed Service Structure (FSS) and the Rotating Service Structure (RSS) were built at the launchpads 39A and B. This new structure also replaced the old Mobile Service Structure. Some of the old structure was preserved, in particular, the white room from Launchpad 39A which in now in the Kennedy Space Centre Visitor’s Centre.
Now just the shuttle stack, that’s the Shuttle, the SRB’s and the external fuel tank would be carried on the Launcher Platform. The platform was also modified for the solid rocket boosters, the exhaust bay was expanded, and the flame deflectors were also replaced.
As the Shuttle was been tested it became clear that huge acoustic shockwaves were bouncing off the launch platform and could endanger both the crew and the delicate insulation tiles on the shuttle. This also happened during the Apollo launches too but in the Saturn, the crew were much higher and farther away from the engines and the Saturn didn’t have the delicate heat-resistant tiles.
So a new expanded deluge system was also added. This was supplied by a 90-meter high water tower which held 1.1 million litres of water and ran through twin 2 meter wide pipes to 16 nozzles that sprayed the water over the launch platform and on to the frame deflector. The deluge system would be activated 6 seconds prior to lifting off and would empty the 1.1 million litres of water in around 41 seconds and reduced the sound level by about half to around 142db.
With these massive metal structures like the Apollo Launch tower and the Saturn rocket itself, there was the ever-present danger of lightning strikes hitting a fully fuelled rocket or causing electronic failures. To mitigate against this the Apollo Launch tower used a lightning conductor at the top of the tower. This proved a cone of protection for the vehicle and equipment within it, but the lighting could still be quite close to sensitive electronics.
When the Shuttle came into service the electronics had shrunk in size but was also became more sensitive, so the lightning conductor was attached to two catenary wires to direct the electrical discharge farther away. For the now cancelled Constellation program, it was upgraded once more to the rolling spheres system. Here three 150 meter towers are topped with 17m fibreglass insulators and linked together with multiple catenary wires around the launchpad which keeps the lighting much farther away.
After the cancellation of the Constellation program in 2010, the final flight of the space shuttle in 2011 the future of the Launch complex 39 was in doubt so in 2013 NASA allowed bidding for the first commercial flights from 39A and a 20-year lease was awarded to SpaceX for the exclusive use of Launchpad.
Unlike the Apollo and shuttle, SpaceX rockets are built horizontally and then lifted up at the launchpad so a new Horizontal Integration Facility was built at pad 39A.
Pad 39B will be used for the SLS system and will use the same vertical integration method first used with the Saturn V and when its not in use for the SLS 39B will be available for commercial launches.
In 2015 a new launch pad 39C was built and is for use with smaller launch vehicles, there are also plans for two more launch complexes, LC-48, LC-49 as the market for commercial space increases with other rockets like the Blue origin New Glenn.
What’s you’re thoughts the America’s gateway to space, maybe you worked there or witnessed some of the launches, let me know in the comments.
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