Nobody has visited the moon since 1972. But with the advent of commercial human space travel, the urge to return is rising again, creating a new space race. NASA has selected the private company SpaceX as part of its commercial spaceflight, but the company also has its own space exploration agenda.
To enable flights to the moon and beyond, both NASA and SpaceX are developing new heavy-lift rockets: the SpaceX spaceship and NASA’s Space Launch System.
But how do they differ and which one is more powerful?
Rockets go through several stages to enter orbit. Disposing of spent fuel tanks in flight makes the missile lighter and therefore easier to accelerate. Once operational, SpaceX’s launch system consists of two phases: the launch vehicle known as the Super Heavy and the spaceship.
Super Heavy is powered by the Raptor rocket engine, which burns a combination of liquid methane and liquid oxygen. The basic principle of a liquid fuel rocket engine is that two propellants – a fuel such as kerosene and an oxidizing agent such as liquid oxygen – are brought together in a combustion chamber and ignited. The flame creates hot gas under high pressure which is expelled through the engine nozzle at high speed to generate thrust.
The rocket will deliver 15 million pounds of thrust upon launch, which is roughly twice as much as the Apollo-era rockets. On the launcher is the spaceship, which is itself propelled by six other Raptor engines and is equipped with a large mission bay to accommodate satellites, compartments for up to 100 crew members and even additional fuel tanks for refueling in space long time interplanetary human space travel.
Super Heavy separates from the spaceship. Wikipedia, CC BY-SA
The spaceship is designed in such a way that it can be operated in the vacuum of space as well as in the atmosphere of Earth and Mars. Small movable wings are used to glide to the desired landing zone.
Once over the landing area, the spaceship tilts to a vertical position and uses its built-in Raptor motors to perform a powerful descent and landing. It will have enough thrust to lift itself off the surface of Mars or the Moon, overcome the weaker gravity of these worlds, and return to Earth – another powerful soft landing. The spaceship and the Super Heavy are both fully reusable and the entire system is designed to lift more than 100 tons of payload onto the surface of the Moon or Mars.
The spaceship is maturing quickly. A recent test flight of the Starship prototype SN8 successfully demonstrated a number of maneuvers required for this function. Unfortunately there was a malfunction in one of the Raptor’s engines and the SN8 crashed on landing. Another test flight is expected in the coming days.
NASA’s space launch system
NASA’s Space Launch System (SLS) will take over the crown from the discontinued Saturn V as the most powerful rocket the agency has ever deployed. The current incarnation (SLS block 1) is almost 100 meters high.
The SLS core stage, which contains more than 3.3 million liters of liquid hydrogen and liquid oxygen (equivalent to one and a half Olympic swimming pools), is powered by four RS-25 engines, three of which were used on the previous space shuttle. Their main difference from the Raptors is that they burn liquid hydrogen instead of methane.
Levels of the SLS. NASA
The rocket’s core stage is augmented by two side-mounted solid rocket boosters that deliver a combined total of 8.2 million pounds of thrust at launch – about 5% more than the Saturn V at launch. This will put the spaceship into low earth orbit. The upper stage is designed to lift the attached payload – the astronaut capsule – out of orbit and is a smaller liquid fuel stage powered by a single RL-10 engine (already used by ATLAS and DELTA rockets) and smaller and lighter than is the RS-25.
The Space Launch System will send the Orion crew capsule, which can support up to six crews for 21 days, to the moon as part of the Artemis 1 mission – a task that current NASA rockets cannot currently perform.
It is said to have large acrylic windows so that astronauts can watch the journey. It will also have its own engine and fuel supply, as well as secondary propulsion systems for the return to Earth. Future space stations such as the Lunar Gateway will serve as a logistical hub, which can also include refueling.
The core stage and booster missiles are unlikely to be reusable (instead of landing, they fall into the ocean), so the SLS system is more costly in terms of both materials and the environment. It was designed to evolve into larger stages capable of carrying crew or cargo weighing up to 120 tons, which is possibly more than the spaceship.
NASA’s SLS and the SpaceX spacecraft on the right could take us both to the moon and beyond. Ian Whittaker / NASA / SpaceX, author provided
Much of the technology used in SLS is called “legacy equipment” as it has been adapted to previous missions, reducing research and development time. However, earlier this month a Test fire the SLS core stage was stopped one minute after the eight minute test began due to a suspected component failure. No significant damage has occurred, and SLS program manager John Honeycutt stated, “I don’t think we’re considering a significant design change.”
And the winner is…
Which spaceship that is likely to be reached will carry a crew to the moon first? Artemis 2 is slated to be the first crewed mission to fly by the moon with SLS, and is expected to launch in August 2023. While SpaceX has not scheduled a specific date for a crewed launch, they are running #dearMoon – a project that includes lunar tourism slated for 2023. Musk has also stated that a manned mission to Mars could take place as early as 2024, including with Starship.
Ultimately, it’s a contest between an agency that has years of testing and experience but is limited by fluctuating changes in tax budget and administrative policies, and a company relatively new to the game but already using 109 Falcon 9 missiles Has started 98% success rate and has a dedicated long-term cash flow.
Whoever reaches the moon first will usher in a new era of exploration of a world that still has much scientific value.
This article by Gareth Dorrian, Postdoctoral Researcher in Space Science at the University of Birmingham, and Ian Whittaker, Lecturer in Physics at Nottingham Trent University, is republished by The Conversation under a Creative Commons license. Read the original article.