Many deep-space, missions, especially those that return material or crews to near-Earth space, are severely limited by the need to carry propellants and heat shields to achieve their mission goals. Lifting these assets from the surface of Earth, landing them on the target body, launching them from there into an Earth-intercept trajectory, and capturing them into Earth orbit requires Earth launch of masses of propellant that increase exponentially with the mission’s total delta V requirement. Preliminary studies of the logistics of gathering material from the Moon and selected Near-Earth Asteroids (NEAs) have demonstrated very large enhancements of mass-retrieval capabilities using propellants derived from sources in space rather than propellants launched from Earth and carried throughout the mission. They also have clearly shown the enormous advantages inherent in deriving propellants from NEAs. This study examines water-based propulsion using NEA volatiles to manufacture storable chemical propellants. The problem of storable propellants on Earth has been solved by the use of hydrazine derivatives as fuel and N2O4 as oxidizer, both made possible by Earth’s nitrogen-rich atmosphere. Nitrogen is scarce on asteroids, and would be best devoted to creating fire-retardant atmospheres for crews. There are plausible paths known for making asteroid-derived carbon-based storable fuels, but the provenance of a suitable storable oxidizing agent that does not employ nitrogen is an unsolved and difficult problem.
Deep Space Industries will develop asteroid regolith simulants for use in terrestrial testing of DSI’s harvesting and processing technologies. This simulant will also be commercially available for scientific and industrial uses throughout the space resource community. Image: Artists concept of DSI’s harvesting technologies. Credit: Bryan Versteeg, Deep Space Industries
DSI is planning a series of reconnaissance spacecraft such as this Mothership craft, which will be sent in search of mineral-rich asteroids. Mothership will deliver nanosats to deep space destinations, acting as the power and communications hub while daughter craft perform exploratory and scientific missions. Credit: Bryan Versteeg, Deep Space Industries
Carbonaceous chondrite asteroids contain 10 to 30 percent water and other volatiles. Dormant comets may contain up to 75 percent volatiles. Early ideas for using the water harvested from these resources as an in-space propellant envisioned splitting water into hydrogen and oxygen and then drastically chilling them to create liquid hydrogen and liquid oxygen. Currently, these cryogenic fuels must be used almost immediately after launch, before they warm up and boil off. By contrast, the NIAC award will look into creating room-temperature fuels such as methane, by combining the hydrogen from water with the carbon available on many asteroids. Storable propellants such as these will not boil off during deep space missions that may take months or years to complete.
“The ability to produce long-life propellants from near Earth asteroids will enable expanded robotic and human exploration of the solar system,” said Faber. “Delivering propellants to high Earth orbit from the ground now costs $20 million to $30 million per ton, while asteroid-derived fuel, delivered to high Earth orbit, may cost as little as one tenth of current prices, making long-term space missions more practical and affordable.”
A Small Business Innovation Research (SBIR) grant, titled “Task-Specific Asteroid Simulants for Ground Testing” will fund the first phase of research into creating asteroid regolith simulants. These simulants will be used in the terrestrial testing of harvesting and processing technologies. Working in conjunction with the University of Central Florida (UCF), DSI will design, prototype, and test a variety of asteroid simulants needed to validate most aspects of asteroid ISRU processes. These include physical simulants for excavation, transfer, and preparation; chemical/mineralogical/volatile simulants for processing tests such as propellant production, metals extraction, and oxygen production; and simulants to evaluate scientific and commercial instrumentation. The simulants created from this project will be commercially available in the near future, improving the validity of any number of scientific and technological experiments in both the private and public sectors.
“Simulants are needed in order to adequately test equipment and processes prior to launch to an actual asteroid. The simulant may need to adequately reproduce the physical characteristics of an asteroid to validate sampling techniques, anchoring methods, or to test hazards such as dust production,” said DSI Chief Scientist and SBIR principal investigator, Dr. John Lewis. “A simulant may need to reproduce the appearance and spectrum of an asteroid, in any of several wavelength ranges. It may need to replicate the mineralogy and possibly the volatiles content to test related instrumentation. Creating accurate and standardized simulants is a vital step in ensuring the consistency of scientific data in the testing of in-space harvesting and processing technologies.”
Deep Space Industries will complete the first phase of the SBIR by the end of the year, and the NIAC by early 2016, in conjunction with ongoing spacecraft development projects.