The Space Launch System (SLS)the rocket of 98 meters of NASA containing the capsule Orionreached the launch pad 39B Kennedy Space Center at Cape Canaveral ahead of the mission’s upcoming launch Artemis II which will bring man back to the Moon for the first time since 1972. The slow 6.4 km journey from Vehicle Assembly Building at the launch pad it took place via the Crawler-Transporter 2 – the heaviest self-propelled vehicle in the world – and lasted about 12 hours. We are now awaiting the final tests of the pre-launch operations which simulate what could happen between 6 and 11 February.
In addition to being the most powerful rocket built by NASA since the Apollo missions, SLS is theonly existing rocket currently unable to send the Orion capsuleits crew and payload directly to the Moon with a single launch. Unlike the Saturn V of the Apollo missions designed only to go to the Moon, this rocket was designed fordeep space explorationtherefore not only the Moon, but also Mars and in prospect the external planets. High 98 meters and heavy 2604 tons at full load, the SLS generates thrust from well 39 million newtonsenough to push the Orion capsule and its cargo to 36,484 km/h in the direction of the Moon. The Artemis II mission will use the initial SLS configuration, called Block 1while future missions will see a evolution of the rocket that will become increasingly larger and more powerful.
How the Artemis II Space Launch System program was born
The SLS program was officially born in 2010 when NASA, on the eve of the decommissioning of the Space Shuttle program, decided to return to focusing onhuman exploration of deep space. However, it was necessary to develop a new one super-heavy launcher capable of leaving Earth’s gravity. In defining SLS, NASA has evaluated different configurationswhich differed in number of stages, propellant types, boosters, performance, development and operating costs, reliability, and ability to maintain key industrial competencies.
NASA opted for a evolutionary designnot a launcher capable of carrying out a single task, like the Saturn V of the Apollo missions, but a rocket adaptable to different configurations of crew and cargo, and which leveraged the decades of expertise developed during the Space Shuttle program. To reduce costs, risks and development times, SLS inherits many elements from the Space Shuttle such as RS-25 enginesarchitecture a side boosters and compatibility with the Kennedy Space Center’s ground infrastructure. This provides the SLS with greater safety, lower risks and a higher probability of mission success in the dynamic and unforgiving environments of spaceflight.
How the rocket that will take man back to the Moon is made
In its configuration Block 1that of the Artemis I, II and III missions, the SLS is configured as a super-heavy launcher capable of carrying 27 tons of payload towards the Moon thanks to the push provided by four RS-25 engines And two side boostersboth borrowed from the Shuttle program, and fromInterim Cryogenic Propulsion Stagewhich gives the final push into space to place the capsule with the astronauts en route to the Moon.
The main stage of the rocket
The main stadiumorange in color due to the thermal coating, is the heart of the SLS. Produced by Boeing, it is the highest single stage of a rocket never built, with well 65 meters in height. Inside it houses the avionics, the flight computer (equipped with a processor slightly more powerful than a Pentium II) and the fuel tanks. liquid hydrogen (at –253 °C) e liquid oxygen (at –183 °C) which act as fuel for the four RS-25 engines produced by L3Harris Technologies. These engines are among the most reliable that exist in the aerospace sector as they have flown successfully for many years 135 times during the Shuttle program.
Together, the engines generate 8.896 million newtons of thrust and work for approx 480 secondsbringing the rocket up to Mach 23 (i.e. 23 times the speed of sound!) and at an altitude of 161km before separation from the higher stage. To give an idea of the power of these engines, just think that they burn beyond 5600 liters of propellant per second providing enough thrust that eight Boeing 747s could fly at the same time. Unlike the Shuttle, however, the SLS’s RS-25 engines they are not reused: recovery would be too complex and expensive given the speed and altitude reached by the main stage.
The two solid rocket boosters
Providing most of the initial thrust are two solid rocket boosters manufactured by Northrop Grumman. Each one is made up of five segmentsone more than the Shuttle’s boosters, and is powered by a fuel based on polybutadiene acrylonitrile and ammonium perchlorate. Each booster generates up to 16,014 million newtons of thrust and, in the first 126 seconds of flight, provides approximately the 75% of the total thrust necessary for take-off. At this stage the rocket consumes approximately 5 tons of fuel per second. After two minutes, a 45 km altitude ea Mach 4.3the boosters separate via explosive bolts and fall into the ocean. Again, the project is optimized for single use. The engines produce so much power, 2.3 million kWh, that they could power 92,000 homes for an entire day.
The Integrated Spacecraft/Payload element
Between the central stage and the Orion capsule is theIntegrated Spacecraft/Payload Elementwhich houses adapters, separation systems and secondary loads. The stage that performs the crucial maneuver is theInterim Cryogenic Propulsion Stage (ICPS)produced by Boeing and United Launch Alliance. Also powered by liquid hydrogen and oxygen, the ICPS provides a boost of 110,000 newtons and is responsible for Trans-Lunar Injection (TLI)the ignition that pushes Orion from Earth orbit towards the Moon. During Artemis II, Orion and ICPS will orbit Earth three times before final ignition. After Orion’s separation, the ICPS will release secondary payloads and re-enter the atmosphere over the Pacific Ocean.
The future evolution of the Space Launch System
SLS is a carrier that yes will evolve over time to support the growth and complexity of future missions. Each subsequent variant of the SLS block becomes more powerful thanks to upgrades made to the engines, boosters and upper stage, providing a flexible platform for a variety of human and robotic space missions, rather than requiring the development of entirely new rockets to increase performance.
Its first variant SLS Block 1 it was used for Artemis I, and will be used for Artemis II and III bringing man back to the Moon. The evolution, SLS Block 1BAnd more powerfulas large as the Saturn V and will be used from Artemis IV onwards. SLS Block 2 will be even more powerful, increasing the cargo carrying capacity to the Moon by up to 46 tons. All variants have a basic design that follows that of the SLS Block 1, namely a central stage that houses propellant tanks, engines, avionics and attachment points for a pair of solid rocket boosters, four liquid propellant engines powered by liquid hydrogen and cryogenic liquid oxygen and an upper stage that is activated in space powered by liquid hydrogen and liquid oxygen.
Main differences with the Saturn V of the Apollo missions
The main difference between the SLS and the Saturn V rocket of the Apollo missions is of concept: Saturn V is a “vertical” rocket, created for the sole purpose of sending man to the Moon, SLS, on the other hand, is versatile. With a fraction of the budget of the Apollo missions, which reached 4.4% of American GDP in 1966, the SLS has the ability to send larger payloads to the ISSthe opportunity to send multiple crews or even a research station on the Moonor the ability to send a crew (along with food, water and other necessary resources) on another planet. Additionally, the SLS capitalizes on five decades of technological advancement in aerospace, offering a well-proven technology with the Shuttle minimizing the risks for the crew. Putting astronauts on “dangerous” capsules like the Apollo ones is unthinkable nowadays.
Wanting to focus instead on the purely technical differences, we SLS is less high (98 meters compared to 110 for the Saturn V), lighter and with less load capacity (27 vs. 41 tons) in its Block 1 configuration. However, the thrust provided by its engines is 15% greater than that of the Saturn V, allowing it to reach top speeds of 39,500 km/h against i 28,000 km/h of the Saturn V. Spending on building the SLS is also less than the Saturn V, less than half adjusted for inflation.
