Brief LTS Earth-Moon Transportation System Description

This system builds the equivalent of a two-way highway between Low Earth Orbit and the lunar surface. The system uses a small fleet of reusable spacecraft, supported by a small fleet of expendable spacecraft, to transfer payloads in LEO, to transfer cryogenic propellant tanks at relatively stable locations in cislunar space, and to transport payloads to and from the lunar surface. The system uses existing ELVs to transport all of its infrastructure from the Earth to Low Earth Orbit.

A New Lunar Architecture

Most of the concepts for lunar transportation architecture that are being considered today by NASA and the aerospace industry are based on decades of study of early spaceflight concepts. In our view these architectures are not an acceptable solution for a new lunar transportation system that will be required to support emerging lunar activities at reasonable cost. Genuine innovation is needed to achieve the goals of affordability and sustainability called for by the President.

LTS is developing a new lunar architecture concept that, we believe, is better suited for a state-of-the-art lunar transportation system. This architecture is characterized by modularity and extreme flexibility leading to reduced development cost and better evolvability. A hard look at this architecture will show that it enables NASA to meet its strategic objectives, including sending small payloads to the lunar surface in a few short years, sending larger payloads to the lunar surface in succeeding years, and sending crews to the Moon and back to the Earth by the middle of the next decade.

This new lunar architecture utilizes current ELVs to bring a new fleet of reusable spacecraft, lunar payloads, propellants, and eventually crews from the Earth to LEO. The reusable LTS spacecraft do the rest of the job. They take payloads from LEO to the Lunar surface and bring payloads back to Earth from the Moon. This architecture permits a "pay as you go" and a "technology development pathway" that allows NASA to achieve a series of its strategic objectives as funding and technology developments permit. The LTS approach reduces mission recurring cost by advancing in-space transportation technology, and later, lunar resource utilization, because this is much less costly than investing in new Earth to Orbit (ETO) transportation.

The size of the payloads delivered to and from the Moon depends on where and how many times Lunar Landers are refueled on their way to and from the lunar surface. The initial fleet of reusable spacecraft are sized to fit the payload capabilities of Delta II Heavy class launch vehicles. This architecture is capable of delivering 800 kg to the lunar surface directly from LEO without the need to refuel in space. It is capable of delivering payloads of 3 metric tons to the Lunar surface with refueling at L1 only. And it is capable of delivering 6 metric tons to the lunar surface with refueling at MEO, at L1, and in lunar orbit. Comparable payloads can be returned from the lunar surface to LEO or to the Earth by refueling the Lunar Lander at one or more of those locations. While this initial system is not meant to transport crews to and from the Moon, it is meant as a technology development testbed for a crewed Earth- Moon transportation system.

A key feature of this Earth-Moon transportation system is that the two principal LTS spacecraft, the Lunar Lander and the Propellant Transporter, are reusable. The Lunar Lander transports payloads from LEO to the Lunar surface and back. The Propellant Transporter transports cryogenic propellant tanks from LEO to any place in cislunar space where Lunar Landers need to be refueled.

This state-of-the-art architecture does not depend on the development of any new heavy-lift launch vehicles. It does depend on the development of six emerging technologies: 1) an autonomous rendezvous and docking system, 2) an autonomous payload transfer system, 3) a spacecraft-to-spacecraft cryogenic propellant tank transfer system, 4) an autonomous propellant tank tapping system, 5) an autonomous lunar landing system, and 6) an autonomous lunar payload offload system. Developing these technologies is less risky and less costly than investments in new ETO transportation or cryogenic propellant transfer technologies. These emerging technologies, except AR&D;, can be developed by ground test. The LTS program plan includes a flight demonstration program in LEO and early robotic missions to the Moon to validate these technologies.

This new lunar transportation system is scalable. A follow-on fleet of larger spacecraft, designed to fit the payload capabilities of Delta IV Heavy class launch vehicles, can transport payloads of up to 30 metric tons from LEO to the lunar surface, depending on where and how frequently they are refueled on their way to and from the Moon. These larger spacecraft will be capable of transporting crews to the lunar surface and returning them to the Earth. They will also have the capability to provide heavy cargo transportation to support a permanent lunar base.

LTS plans to develop a fleet of spacecraft that are sized to fit the payload envelope and the payload capabilities of Delta II Heavy launch vehicles to validate LTS concepts and to deliver payloads to and from the lunar surface.  Once LTS concepts are validated using Delta II Heavy launch vehicles in a series of flight demonstration missions, LTS plans to develop larger spacecraft that are sized to fit the payload envelope and payload capabilities of Delta IV Heavy class launch vehicles.  The larger spacecraft fleet will have the capability to bring crews and heavy payloads to and from the Moon.

A very important element of the LTS lunar architecture is crew safety. Commonality of modules and subsystems increases flight operations experience rapidly, leading to greater safety. Backup Lunar Landers can be prepositioned at L1, in lunar orbit, or even on the lunar surface to provide crew rescue capability in case of a mission abort situation.

The nonrecurring costs to develop this Earth-Moon transportation system are much lower than the cost of developing systems that use more traditional architectures because there are fewer unique developments and it relies on existing launch vehicles. A significant reduction in lunar mission costs comes from the reusability of the major elements of the LTS system.

The largest cost – perhaps as much as 70% of each lunar mission – is the delivery of the spacecraft, the propellants, and the lunar payloads from the Earth to LEO. LTS will complete this phase using existing expendable launch vehicles. While these are expensive to fly, the development cost of significant new launch capability represents dozens of launches and many years of flight operations experience. When propellants can be manufactured
on the Moon, Earth-Moon mission costs may be reduced by 60% or more. If and when reusable Earth-to-LEO launch vehicles become available, lunar mission costs may be reduced by a further 60% or more.

Because this system relies on existing technologies and existing ELVs and requires only the maturation of several enabling technologies, it can deliver payloads to the lunar surface relatively quickly and well within NASA's schedule for robotic and human lunar exploration.

The LTS lunar architecture is based on concepts that reduce lunar mission life-cycle costs and technical risks, improve reliability and crew safety, accelerate lunar mission schedules, and allow for the routine delivery of lunar payloads on the equivalent of a two-way highway between the Earth and the Moon.