An article describing the results of the study was published in the Acta Astronautica magazine. Since in December 1972, the crew of the Apollo-17 ship returned to Earth, humanity does not part with the dream to visit the moon again. In 2017, the US government launched the Artemis program, the purpose of which is the flight of the "first woman and the next man" on the South Pole of the Moon by 2024.
In Artemis program, it is planned to use the new Lunar Gateway's lunar orbital platform as a permanent space station, from where the reusable modules will deliver astronauts to the moon. The implementation of the new concept requested the development of new optimal landing schemes on the surface of the moon. Today, private companies on the request of NASA are conducting research to create new reusable landing modules, but the progress and results of the conducted studies have not yet been reported.
Master's student Skolteha Kir Latyshev, graduate student Nikola Garzaniti, Associate Professor Alessandro Garcar and Professor Mit Edward Crowley developed mathematical models to assess the most promising landing schemes for the Artemis program. In the historical program "Apollo", for example, a lunar module was used from the landing and take-off steps, which delivered two astronauts to the moon and back to the ship, leaving the landing step on the moon.
Researchers proceeded from the assumption that the LUNAR Gateway platform will be located on an almost straight-line halo orbit near Lagrange L2 point - this orbit today is the preferred location of the station that allows the astronaut landing on the southern pole of the moon. Scientists simulated a variant in which the crew in four astronauts will spend about seven days on the moon, varying the number of steps and fuel type. In total, 39 options for the future system of landing a person on the moon were analyzed. Including a comparison of the most promising options in the project cost
The team used an integrated approach to the assessment of alternative configurations of landing modules by analyzing the set of options using screening models. First, experts identified a basic set of architectural solutions, including the number of steps and fuel type for each stage of the landing module.
The data obtained were summarized in the form of mathematical models, with the help of which scientists conducted a comprehensive numerical study of the options for building a system, combining various architectural solutions. At the final stage, the received solutions was analyzed and preferred options that could be interesting to those involved in the design of lunar landing modules.
The analysis showed that for the disposable systems of the type of planting modules Apollo, the most successful solution from the point of view of the total mass of the fuel, the dry mass of the spacecraft and the launch value will be a two-stage architecture. However, for reusable ships, which are planned to be used as part of the Artemis program, single-stage and three-stage systems quickly begin to compete with two-stage.
Given all the assumptions made in the article, it can be argued that the "unconditional" leader among solutions for short-term lunar missions is a reusable single-stage module on liquid oxygen and liquid hydrogen (LOX / LH2). However, the authors emphasize that this is only a preliminary analysis, in which factors such as the safety of the crew, the likelihood of the mission, as well as the risks of project management are not taken into account. To account for these factors, more detailed simulation will be required at the subsequent stages of the program.
Kir Latyshev notes that, as part of the Apollo program, NASA engineers conducted a similar analysis and chose the two-stage module configuration. However, at that time, the lunar program was built on a fundamentally different architecture, in which there was no lunar orbital station, where it would be possible to place the lunar module in the interval between flights. This means that all flights had to perform from the ground using disposable lunar modules, that is, creating a new apparatus for each mission. In addition, in the absence of a lunar orbital station, the use of a three-step planting system, which is considered in our time, has not been possible.
"In the study, we received an interesting result: if we consider disposable devices, it turns out that even with the orbital station, you can create a two-step landing module (similar module" Apollo ") with a smaller mass of the apparatus and fuel and lower costs, which generally complies with the concept, Adopted in the program "Apollo". But the use of reusable modules changes everything.
Although single and three-stage devices still exceed two-stage by their mass, they allow us to repeatedly use most of their masses (approximately 70-100 percent, and not 60, as in the case of two-stage modules), while ensuring cost savings and delivery costs New devices per orbital station, which leads to the reduction of the lunar program as a whole, "says Latyshev.
It adds that an important factor in the design of manned space systems is the security of the crew, but the consideration of this issue goes beyond the research framework. "Security is an important factor on which the choice of landing scheme depends. The use of multistage modules can provide more opportunities for a safe return of the crew to the lunar orbital station in case of an emergency, which is advantageous distinguished by a multi-stage module from our "leader" - single-stage system.
Unlike a single-stage module, a two-or three-stage system allows you to use to return the crew both take-off and landing module. At the same time, it is expected that, due to greater complexity, two- and three-stage systems will be higher than the risk of technical failures compared to single-stage systems.
That is, the choice here is again ambiguous - each scheme has its advantages and disadvantages, "adds Latyshev. In the future, scientists plan to expand the framework of their work and conduct a comprehensive study of the systemic architecture of the entire research infrastructure, which is an integral part of all promising programs for manned space flights to the moon.
Source: Naked Science