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3 Questions: Desire of Artemis I for a return to the moon | MIT News

This week, NASA will attempt to launch the Artemis I mission. Artemis I is an uncrewed test flight that will launch the Space Launch System (SLS) rocket and send the Orion spacecraft around the moon and back to test the system and the material thoroughly before future flights with astronauts.

The first of several missions, Artemis I will pave the way for subsequent missions with the ultimate goal of establishing the first long-term human robotic presence on and around the moon to enhance international and commercial collaboration. So far, a total of seven astronauts with ties to MIT – including Raja Chari SM ’01, Woody Hoburg ’08, Jasmin Moghbeli ’05 and Kate Rubins in 2020 and Marcos Berríos ’06, Christina Birch PhD ’15 and Christopher Williams PhD ’12 in 2021 – have been appointed to the Artemis program. Through the partnerships and insights gained from Artemis, NASA will look to the future of human space exploration – Mars.

Here, Olivier de Weck and Thomas “Joey” Murphy discuss the new features of the Artemis launch system, the process of planning (and sometimes rescheduling) such a large mission launch, and the overall impact of the Artemis program on the world. space exploration. De Weck is Professor of Astronautics and Apollo Program Engineering Systems in the Department of Aeronautics and Astronautics at MIT (AeroAstro) and Editor-in-Chief of the Spacecraft and Rocket Journalwhile Murphy is a doctoral student and rocket launcher and works with Kerri Cahoy, professor of aeronautics and astronautics at AeroAstro and associate editor of the Spacecraft and Rocket Journal in the STAR lab at MIT.

Q: What are the main differences between Artemis I and previous generations of launch vehicles we used to go to the Moon, and what are some of the new features and capabilities that the space community is excited about for this mission?

Murphy: There have only ever been two launchers capable of launching humans to the moon. The previous two were the Saturn V and the N1, which was the Soviet attempt to reach the moon. The N1 attempted to launch four times (unmanned), all of which ended in disaster. Artemis I will fly on the Space Launch System (SLS), which has been in development for about a decade. One of the main differences in the new approach to the moon is that the Saturn V flew fully autonomous missions. They put a command module (the main space capsule), a service module (fuel tank, engine and other equipment) and a lunar module (the lander) on a single rocket. This trio traveled to the Moon, landed, and finished with a re-entry to Earth. The Artemis program is different. Artemis relies on the Lunar Gateway, which is basically a small space station orbiting the moon. Before the astronauts leave Earth, Gateway will be waiting up there, with the lander module (a modified SpaceX Starship) docked at the station. This means that all that needs to be launched on SLS is the Orion capsule with the crew inside. Since they don’t need to bring the lander with them, more useful gear can be taken. Orion supports a crew of four, compared to Apollo’s maximum crew size of three. The Artemis I mission is primarily a test of the SLS rocket and the Orion capsule, to ensure they can successfully travel to the moon and back. Artemis II, scheduled for 2024, will add astronauts, who will fly around the moon, but not land there, before returning, followed by the Artemis III mission.

From Weck: The correct comparison for the SLS is the now retired Saturn V rocket, which was developed as part of the Apollo program and active between 1967 and 1973. Here are some comparisons in terms of numbers: height, 363 feet (Saturn V) against 322 feet (SLS block 1, then goes to 365 feet); payload in low Earth orbit, 310,000 pounds (Saturn V) compared to 209,000 pounds (SLS Block 1, then increases to 290,000 pounds); and then there’s the fact that the Saturn V first stage used RP-1 (kerosene) and liquid oxygen (LOX), versus cryogenic hydrogen (LH2) and LOX for the SLS. In terms of ultimate capability, the SLS Block 2 and the Saturn V are very comparable. The difference is that Saturn V was a clean sheet design and SLS reuses a lot of Space Shuttle hardware, including the solid thruster segments (five versus four), RS-25 main engines, as well as the fuel tank design external . In retrospect, we estimated that congressionally mandated Shuttle hardware reuse increased systems engineering effort by 43% over a clean sheet design. So, personally, I would have preferred to see a new rocket design, instead of a mandatory reuse of 1970s technology.

Q: What are some of the factors considered in determining whether to delay a launch attempt?

From Weck: There are essentially two major launch delay factors: (1) technical problems with the rocket, of which hydrogen leaks, particularly at the fill point interface between the first stage and the launch tower, are the more important. Hydrogen is very volatile and difficult to contain. Already, the shuttle program is experiencing frequent delays due to problems with hydrogen leaks. And (2) weather-related delays. The latest example is Hurricane Ian in Florida, where the rocket had to be rolled into the vertical [Vehicle] Assembly Building. All of this reminds us that there is nothing “routine” about safely launching large rockets. It’s a great collective effort, and each rocket has its own personality and idiosyncrasies.

Murphy: If NASA sees reason to believe the mission will not go completely as planned, it will cancel a launch attempt. Any launch failure is an extremely costly setback – plus the work required to resolve the failure and ensure it never happens again on a future flight. SLS is unlikely to fly more than 10 times, so we really want to get the most out of every flight it takes. With this rocket, even more so than any other rocket, there really is no room for error. With Artemis I, the issues we have seen are mostly related to hydrogen leaks. The rocket is fueled with liquid hydrogen, which is the most efficient chemical to use as rocket fuel. The problem is that hydrogen is an extremely small molecule, which means that it is very difficult to contain it. If you put hydrogen in a steel container, it can literally squeeze between the atoms of the metal. Even the tiniest of pinholes will leak hydrogen. These are the main problems SLS has encountered during recent launch attempts and why the rocket did not launch in early September. NASA made adjustments to the rocket to stop the hydrogen leak, and the leaks appear to be resolved now. One of the problems they are currently facing is the Flight Termination System (FTS) – this is a system of explosives attached to the rocket, so that if the mission goes wrong in flight, the rocket will self-destruct, to prevent any danger to people on the ground. Because this system is so critical and sensitive, it is only certified for a few weeks. If SLS continues to sit on the launchpad, the FTS may “time out”, meaning it will need to be replaced. Unfortunately, we find ourselves in a system where launch delays can lead to more launch delays.

Q: What can we expect from this mission and why is this an exciting step for human exploration/space transportation?

From Weck: This mission is essentially a dress rehearsal for the first human mission around the moon with Artemis II. In Artemis I, the Orion capsule does not house human astronauts, but instrumented dummies to ensure the life support system works as intended. This is an approximately 35-day “slingshot” mission where the Orion capsule will exit Earth’s gravity, swing around the moon in a highly elliptical trajectory, then return to Earth and crash into the Pacific Ocean. in a controlled manner. It should be noted that this mission is significantly longer than an Apollo mission where the astronauts took about 10 to 12 days for the return trip to the moon.

Murphy: The most important thing we will learn about this system is whether SLS is fit to launch astronauts. Astronauts for the Artemis II mission have not yet been selected, but when they are, they will be assured that the rocket they are piloting has had its design validated by the Artemis I mission. In addition, Artemis I carries 10 Onboard CubeSats as secondary payloads, all of which will study various aspects of the environment around the moon. This mission lays the foundation for our return to the Moon, proving that the last 10 years of SLS rocket development have all resulted in a vehicle ready for prime time.