The future of space exploration includes some rather ambitious plans to send missions farther from Earth than ever before. Beyond the current proposals for building infrastructure in cis-lunar space and sending regular crewed missions to the Moon and Mars, there are also plans to send robotic missions to the outer Solar System, to the focal length of our Sun’s gravitational lens, and even to the nearest stars to explore exoplanets. Accomplishing these goals requires next-generation propulsion that can enable high thrust and consistent acceleration.
Focused arrays of lasers – or directed energy (DE) – and lightsails are a means that is being investigated extensively – such as Breakthrough Starshot and Swarming Proxima Centauri. Beyond these proposals, a team from McGill University in Montreal has proposed a new type of directed energy propulsion system for exploring the Solar System. In a recent paper, the team shared the early results of their Laser-Thermal Propulsion (LTP) thruster facility, which suggests that the technology has the potential to provide both high thrust and specific impulse for interstellar missions.
Within the next fifteen years, NASA, China, and SpaceX plan to send the first crewed missions to Mars. In all three cases, these missions are meant to culminate in the creation of surface habitats that will allow for many returns and – quite possibly – permanent human settlements. This presents numerous challenges, one of the greatest of which is the need for plenty of breathable air and propellant. Both can be manufactured through electrolysis, where electromagnetic fields are applied to water (H2O) to create oxygen gas (O2) and liquid hydrogen (LH2).
While Mars has ample deposits of water ice on its surface that make this feasible, existing technological solutions fall short of the reliability and efficiency levels required for space exploration. Fortunately, a team of researchers from Georgia Tech has proposed a “Magnetohydrodynamic Drive for Hydrogen and Oxygen Production in Mars Transfer” that combines multiple functionalities into a system with no moving parts. This system could revolutionize spacecraft propulsion and was selected by NASA’s Innovative Advanced Concepts (NIAC) program for Phase I development.
As part of the Artemis Program, NASA intends to establish all the necessary infrastructure to create a “sustained program of lunar exploration and development.” This includes the Lunar Gateway, an orbiting habitat that will enable regular trips to and from the surface, and the Artemis Base Camp, which will permit astronauts to remain there for up to two months. Multiple space agencies are also planning on creating facilities that will take advantage of the “quiet nature” of the lunar environment, which includes high-resolution telescopes.
As part of this year’s NASA Innovative Advance Concepts (NIAC) Program, a team from NASA’s Goddard Space Flight Center has proposed a design for a lunar Long-Baseline Optical Imaging Interferometer (LBI) for imaging at visible and ultraviolet wavelengths. Known as the Artemis-enabled Stellar Imager (AeSI), this proposed array of multiple telescopes was selected for Phase I development. With a little luck, the AeSI array could be operating on the far side of the Moon, taking detailed images of stellar surfaces and their environments.
In the coming years, NASA plans to send several astrobiology missions to Venus and Mars to search for evidence of extraterrestrial life. These will occur alongside crewed missions to the Moon (for the first time since the Apollo Era) and the first crewed missions to Mars. Beyond the inner Solar System, there are ambitious plans to send robotic missions to Europa, Titan, and other “Ocean Worlds” that could host exotic life. To accomplish these objectives, NASA is investing in some interesting new technologies through the NASA Innovative Advanced Concepts (NIAC) program.
This year’s selection includes solar-powered aircraft, bioreactors, lightsails, hibernation technology, astrobiology experiments, and nuclear propulsion technology. This includes a concept for a Thin Film Isotope Nuclear Engine Rocket (TFINER), a proposal by senior technical staff member James Bickford and his colleagues at the Charles Stark Draper Laboratory – a Massachusetts-based independent technology developer. This proposal relies on the decay of radioactive isotopes to generate propulsion and was recently selected by the NIAC for Phase I development.
Mars is the next frontier of human space exploration, with NASA, China, and SpaceX all planning to send crewed missions there in the coming decades. In each case, the plans consist of establishing habitats on the surface that will enable return missions, cutting-edge research, and maybe even permanent settlements someday. While the idea of putting boots on Martian soil is exciting, a slew of challenges need to be addressed well in advance. Not the least of which is the need to locate sources of water, which consist largely of subsurface deposits of water ice.
Herein lies another major challenge: Martian ice deposits are contaminated by toxic perchlorates, potent oxidizers that cause equipment corrosion and are hazardous to human health (even at low concentrations). To this end, crewed missions must bring special equipment to remove perchlorates from water on Mars if they intend to use it for drinking, irrigation, and manufacturing propellant. This is the purpose of Detoxifying Mars, a proposed concept selected by the NASA Innovative Advanced Concepts (NIAC) program for Phase I development.
In Dante Alighieri’s epic poem The Divine Comedy, the famous words “Abandon all hope, ye who enter here” adorn the gates of hell. Interestingly enough, Dante’s vision of hell is an apt description of what conditions are like on Venus. With an average temperature of 450 °C (842 °F), atmospheric pressures 92 times that of Earth, and clouds of sulfuric acid rain to boot, Venus is the most hostile environment in the Solar System. It is little wonder why space agencies, going all the way back to the beginning of the Space Age, have had such a hard time exploring Venus’ atmosphere.
Despite that, there are many proposals for missions that could survive Venus’ hellish environment long enough to accomplish a sample return mission. One such proposal, the Sample Return from the Surface of Venus, comes from aerospace engineer and author Geoffrey Landis and his colleagues at the NASA Glenn Research Center. Their proposed concept was selected for this year’s NASA Innovative Advanced Concepts (NIAC) program. It consists of a solar-powered aircraft that would fashion propellant directly from Venus’ atmosphere and deploy a sample-return rover to the surface.
The day when human beings finally set foot on Mars is rapidly approaching. Right now, NASA, the China National Space Agency (CNSA), and SpaceX have all announced plans to send astronauts to the Red Planet “by 2040”, “in 2033”, and “before 2030”, respectively. These missions will lead to the creation of long-term habitats that will enable return missions and scientific research that will investigate everything from the geological evolution of Mars to the possible existence of past (or even present) life. The opportunities this will create are mirrored only by the challenges they will entail.
One of the greatest challenges is ensuring that crews have access to water, which means that any habitats must be established near an underground source. Similarly, scientists anticipate that if there is still life on Mars today, it will likely exist in “briny patches” beneath the surface. A possible solution is to incorporate a system for large-scale water mining operations on Mars that could screen for lifeforms. The proposal, known as an Agnostic Life Finding (ALF) system, was one of thirteen concepts selected by NASA’s Innovative Advanced Concept (NIAC) program this year for Phase I development.