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U.S. Companies Advance Critical Human Lander Technologies

By Doug Messier
Parabolic Arc
June 11, 2020
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Compilation of artist’s renderings representing NextSTEP Appendix E work. Top row, left to right: Dynetics, Lockheed Martin, Blue Origin. Bottom row, left to right: Aerojet Rocketdyne, Northrop Grumman, Masten Space System, Boeing. (Credit: NASA)

HUNTSVILLE, Ala. (NASA PR) — NASA and 11 commercial partners recently completed a series of technical studies, demonstrations and ground prototypes for 21st Century human landing systems. The Next Space Technology Exploration Partnerships (NextSTEP) Appendix E work helped the agency refine its Artemis program requirements for the companies competing to build the landers that will take American astronauts to the Moon throughout this decade.

NASA’s Human Exploration and Operations Mission Directorate and Space Technology Mission Directorate funded the 11 companies that led the Appendix E work: Aerojet Rocketdyne of Canoga Park, California; Blue Origin of Kent, Washington; Boeing of Houston, Texas; Dynetics of Huntsville, Alabama; Lockheed Martin of Littleton, Colorado; Masten Space Systems of Mojave, California; Maxar Technologies of Westminster, Colorado; Northrop Grumman of Dulles, Virginia; Orbit Beyond of Edison, New Jersey; Sierra Nevada Corporation of Louisville, Colorado; and SpaceX of Hawthorne, California.

Through the Appendix E contracts, NASA gained valuable insight into architecture options and key technologies necessary for the new human landers, with a focus on spacecraft elements for lunar descent, in-space transfer, and refueling.

“The Appendix E results have made us smarter buyers for the human landing systems now under development, one of which we expect will ultimately land the first humans on the Moon since 1972,” said Nantel Suzuki, human landing system program executive at NASA Headquarters in Washington. “By engaging a broad cross-section of the space industry in these studies, we were able to improve and validate our lander requirements, and we now have a much deeper understanding of the greatest technological challenges involved with safely landing our astronauts on new locations of the lunar surface and returning them home.”

Since the vice president directed NASA in March 2019 to return humans to the Moon by 2024, America’s space industry has been bustling to help the agency realize this ambitious goal.

“Under Appendix E alone, the amount of work completed in less than a year is very impressive,” said  Suzuki, who led the formulation of Appendix E as well as the follow-on Appendix H solicitation to industry for the human landing system. “The 2024 mission timeline has focused NASA to find the most efficient ways to work with the private sector and meet this challenge.”

Seven out of the 11 companies conducted demonstrations or built prototypes to address cryogenic fluid management. Cryogenic propellants are gases such as oxygen, methane, and hydrogen that are cooled to very cold (cryogenic) temperatures until they are in a liquid state that requires less volume—i.e., more usable energy in smaller tanks. Cryogenic space propulsion systems exhibit very high performance, but even the slightest source of ambient heat generated by the vehicle itself, or changes in pressure due to the vacuum of space, can lead to “boil off” or loss of fuel as it reverts to its gaseous state and vents from the tank.

NASA saw the companies develop new approaches for cryogenic tank design and insulation, improvements to filling and draining the tanks in a vacuum, and cryocooler implementation to address cryogenic boil off challenges. Some companies also focused on storable propellants like hydrazine, which do not boil off like cryogenics and are often used for long duration space missions. NASA’s Voyager 1 spacecraft, for instance, has been cruising the solar system for more than 42 years on the same tank of hydrazine in its propulsion system.

Appendix E propellant transfer studies provided keen insight into the challenges of moving propellants, including cryogenics, between lander elements in space—so they can be replenished after boil off, or refueled between missions and reused.  

Automated rendezvous and proximity operations and docking (RPOD) was another area of focus for the companies. RPOD will be a key procedure in lunar operations, where much of the vehicle aggregation of separately-launched lander elements may happen without crew aboard to oversee vehicle dockings. Companies used ground-based testbeds to validate rendezvous and proximity operations technology, and also examined common sensors like optical cameras and LIDAR that are useful for proximity operations, precision landing, and hazard avoidance.

Precision landing and hazard avoidance technologies also earned well-deserved attention in Appendix E. Apollo 11 enthusiasts may recall the harrowing landing  during which Neil Armstrong and Buzz Aldrin found themselves off-course and quickly descending into an alarming combination of a crater field littered with boulders. They were able to take manual control and land safely on the surface with less than 6% fuel in the tank.

“We want human landers that rely on modern precision landing and hazard avoidance technologies,” said Greg Chavers, human landing system deputy program manager at NASA’s Marshall Spaceflight Center in Huntsville, Alabama. “Our astronauts will be trained to fly these spacecraft, but we believe industry can build on existing technologies to refine these systems and reduce the need for human control.”

In fact, much of the Appendix E precision landing and hazard avoidance work extended the capabilities of proven flight heritage systems. Other studies examined newer technologies, incorporating precision landing sensors into conceptual lander designs and performing software demonstrations to match real-time imagery with detailed lunar surface maps.

“It’s difficult to articulate the sheer quality and quantity of data that has been revealed through Appendix E,” remarked Chavers. “Perhaps equally important are the ways that we learned to work with the companies to remove traditional barriers and use more streamlined methods to share data between the government and private sector. That will be chiefly important as we focus the same NASA workforce to team with Blue Origin, Dynetics and SpaceX as they develop their human lander concepts. To land humans on the Moon in 2024, we need the best of U.S. industry and the best of NASA to work together to achieve such a monumental goal.”

Charged with returning to the Moon in 2024, NASA’s  Artemis program will reveal new knowledge about the Moon, Earth and our origins in the solar system. The human landing system, and its core technologies, are a vital part of NASA’s deep space exploration plans, along with the Gateway, Space Launch System (SLS) rocket, and Orion spacecraft that will send astronauts to the Moon. Gaining new experiences on and around the Moon will prepare NASA to send the first humans to Mars in the coming years, and the human landing system will play a vital role in this process.

For more information about NASA’s Moon to Mars exploration plans, visit:

2 responses to “U.S. Companies Advance Critical Human Lander Technologies”

  1. Terry Stetler says:

    The image gallery is missing Lunar Starship


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