The historic Launch Complex 39 consists of the Vehicle Assembly Building for final stack assembly and testing, a crawlerway connecting the VAB to the launch pads, the Launch Control Center with firing rooms, and two launch sub-complexes — Pad 39A and Pad 39B. Pad 39B supports all SLS/Artemis launches.
Originally built for the Apollo Saturn V, the iconic VAB is one of the largest buildings in the world by volume and serves as the central hub of NASA's multi-user spaceport.
For Artemis, NASA replaced shuttle-era platforms in High Bay 3 with 10 new levels of work platforms (20 platform halves) providing 360° access to the SLS/Orion stack. Each platform weighs 300,000–325,000 lbs and measures ~38 × 62 ft.
For Artemis II, High Bay 2 was equipped with a new vertical integration center tool — allowing the fully assembled core stage to be suspended 225 ft in the air for vertical processing while booster stacking continued separately in High Bay 3. This dual-bay approach doubles usable assembly space.
Upgraded from Apollo and Shuttle era to a "clean pad" concept — providing the basics all rockets need (power, water, flame trench) while keeping other infrastructure rocket-agnostic. 1.3 million feet of copper cable was replaced with 300,000 feet of fiber-optic cable during refurbishment.
A water tower holding ~400,000 gallons dumps its entire reservoir onto the mobile launcher and into the flame trench in under 30 seconds at ignition. Peak flow rate: 1.1 million gallons per minute — enough to empty two Olympic swimming pools in one minute.
450 ft long (1.5 football fields). The flame deflector — 57 ft wide × 43 ft high × 70 ft long — is made of 112 steel plates and redirects exhaust north at liftoff. Peak temperature: 2,200°F (1,204°C). More than 96,000 heat-resistant bricks were installed prior to Artemis I.
Three 600-ft-tall masts with catenary overhead wires protect the pad perimeter. During Artemis I wet dress rehearsal, the system intercepted the most powerful lightning strike ever recorded at Kennedy — with zero damage to the rocket or spacecraft.
Liquid oxygen sphere: 850,000+ gallons. For Artemis II, EGS constructed the world's largest liquid hydrogen tank — an 83-ft-diameter sphere holding 1.25 million gallons. It uses microsphere (hollow glass bubble) insulation reducing boiloff by 46%, and has a built-in heat exchanger that can eliminate boiloff entirely when connected to a cryogenic refrigeration unit. Together with the existing 850,000-gallon LH₂ tank, this enables 24-hour turnaround between launch attempts.
New for Artemis II. Four baskets — each carrying up to 5 personnel — slide ~1,700 ft of steel catenary wire from the mobile launcher tower to a terminus outside the pad perimeter in ~30 seconds at ~50 mph. Magnetic braking controls speed in varying weight and weather conditions. At the terminus, armored transport vehicles evacuate personnel to a safe haven through a crash-out gate.
The mobile launcher is the 400-ft-tall, 11-million-pound ground structure used to assemble, process, and launch SLS from Pad 39B. It consists of a two-story base (25 ft high × 165 ft long × 135 ft wide) and a tower.
Key umbilicals on the tower supply SLS and Orion with power, communications, coolant, propellant, and purge gases. All umbilicals release at liftoff. The Crew Access Arm at 274 ft provides the path astronauts walk to enter Orion before launch.
The crawler-transporter carries the fully stacked SLS/Orion on the mobile launcher from the VAB to Pad 39B — a journey of 4.2 miles that takes approximately 8 hours at roughly 1 mph. Originally built for the Apollo Saturn V and space shuttle, the crawler has been upgraded for SLS. It picks up the mobile launcher at the VAB, sets it down on pad-mount mechanisms, and returns to a parking position before launch.
After splashdown in the Pacific Ocean off San Diego, an interagency team recovers Orion and crew:
U.S. Navy amphibious specialists and Air Force weather specialists from the Department of War
NASA's Sasquatch mapping team and engineers from Kennedy and Johnson
Forward bay cover and three main parachutes recovered from the ocean to port side of the Navy ship via crane
Orion transported to U.S. Naval Base San Diego on the recovery ship, then trucked back to Kennedy for post-flight processing
NASA practiced recovery procedures on USS Somerset during Underway Recovery Test-12, March 2025
After return to Kennedy, Orion is inspected and analyzed to inform future missions — completing the full launch-to-landing cycle.