Lockheed Martin

Comparison of Deimos and Phobos as Destinations for Human Exploration and Identification of Preferred Landing Sites

A human mission to one of the two moons of Mars has been suggested as an easier precursor before a mission to land on Mars itself. Astronauts would explore the moon in person and teleoperate rovers on the surface of Mars with minimal lag time, returning samples to Earth. Lockheed Martin evaluated such a mission as part of its Stepping Stones sequence of missions in the spirit of the “Flexible Path” approach advocated by the Augustine Committee. In this paper, we compare Deimos and Phobos as potential destinations, including trajectory design, communications access to Earth and the Martian surface, solar illumination, expected radiation environment, planetary protection issues, and physical access to and from the Martian surface. While prior mission concepts have tended to focus on Phobos, we conclude that Deimos is the better destination for an early teleoperation mission largely because it is farther from Mars than Phobos. This reduces the required mission ΔV by 400 m/s, provides longer communications access and line of sight to 15 deg higher latitudes on the Martian surface, and reduces the frequency and cumulative duration of eclipses by Mars so that a solar powered mission is easier on Deimos than on Phobos. Using a shape model of Deimos, we performed global lighting and communications access analysis and determined that there are two specific regions on Deimos which are the most favorable landing sites. Small areas along the North and South arctic circles on the Mars-facing side of Deimos experience a continuous view of Mars, continuous sunlight for up to ten months during polar summer, and continuous line of sight to Earth during most of the sunlit season. These sites are centered near 60° N 0° W, and 51° S 7° E. A timeline for a mission to these two sites is provided for the 2033-2035 opportunity. This is the easiest opportunity during the next few decades because optimum Earth-to-Mars orbital geometry will likely coincide with the phase of the solar activity cycle that provides the most protection from galactic cosmic rays, reducing the effective radiation dose. During this mission, the crew would land at the southern hemisphere site first, during the middle of the southern summer season. After a four month stay, the crew would depart the surface of Deimos to orbit for 50 days during the equinox and eclipse season, when lighting is unfavorable at any location on the Deimos surface. At the beginning of northern summer, the crew would land at the northern site and stays for ten months before returning to Earth. In this way, the crew can explore both hemispheres of Deimos without requiring advanced power systems.

Stepping Stones: Exploring a Series of Increasingly Challenging Destinations on the Way to Mars

,The Stepping Stones plan for human space exploration is a series of increasingly challenging exploration missions to develop technologies and demonstrate new capabilities that enable subsequent missions to push farther into space and explore for longer durations. Step by step, at a sustained pace, astronauts will journey beyond Low Earth Orbit (LEO) to the Moon, then to distant asteroids, and finally to the outer moon of Mars. At each destination, astronauts will address key science objectives relating to the formation of the solar system and the origins of life. The Stepping Stones plan demonstrates the Orion MultiPurpose Crew Vehicle’s capability beyond LEO and provides opportunities to perform and perfect telerobotic surface operations from orbit, space maneuvers near small bodies, and sample return. The missions will test and improve upon existing technologies for astronaut protection and health, forging the way for the future of human space flight.

Plymouth Rock: Early Human Missions to Near Earth Asteroids Using Orion Spacecraft

In the last decade, astronomers have discovered a few dozen very small asteroids whose orbits around the Sun are similar to Earth’s. Round trip missions to these asteroids are therefore much easier than to previously known Near Earth Asteroids, and roughly as easy as landing on the Moon. The authors have investigated the feasibility of conducting an asteroid mission that would complement NASA’s lunar exploration architecture, using the Orion spacecraft now being developed for lunar exploration. The proposed mission concept, dubbed Plymouth Rock, combines a pair of enhanced Orion spacecraft to provide the necessary propulsion, living space, and life support capability for two astronauts. We have concluded that the dual-Orion configuration can be modified to support deep space mission durations of five to six months. Longer missions would be more difficult due to radiation exposure, volumetric packaging limits for life support consumables, and the small habitable volume available. There are at least three opportunities between 2015 and 2030 when such a mission could be performed with the capabilities of a dual-Orion spacecraft. These occur in 2019-2020, 2028, and 2029. However, the number of opportunities will likely increase as more asteroids are discovered. All of the asteroids in question are very small, between 5 m and 50 m in diameter. Propulsion capability and mission duration are the most limiting factors in the mission design. Typical missions have reentry inertial velocities of 11.1-11.3 km/s which are compatible with Orion’s existing thermal protection systems. Mission design data for two preferred asteroid targets, 2008 EA9 and 2000 SG344 are provided.

Centaur Extensibility For Long Duration

The Centaur LOX/LH2 cryogenic stage has been used as an upper-stage for most of the deep space missions because of its high ISP. Now with the advent of Lunar and Mars initiatives, Centaur-like vehicles are being considered for trans-Lunar, Earth-return, and Mars missions with quiescent coast durations lasting from a month, up to one year. This paper reviews the results of a funded study by NASA/KSC NAS10-00-060 done by Lockheed Martin Space Systems titled: Advanced Cryogenic Evolutionary Stage (ACES). This study is an assessment of the Centaur integrated with new technologies in an effort to accommodate these longer duration missions. Study specifics include: avionics, environmental effects, attitude controls, active/passive thermal controls, passive thermal Vacuum Insulation Panel applications, advanced MLI, sun-shield, RL10 engine (cold-soak, restart and long duration effects), and operations.

Commercial Launch Services: an Enabler for Launch Vehicle Evolution and Cost Reduction

This paper proposes that NASA commercially purchase all future launch services, including ISS service and the launch requirements for all phases of lunar exploration and beyond. This commercial purchase of launch services will provide the foundation of a robust commercial launch industry and dramatically lower cost. This paper also shows how NASA’s currently planned exploration architecture readily accommodates and even benefits from commercial launch services. NASA’s use of commercial launch services is consistent with President Bush’s mandate for the Vision for Space Exploration: “Promote international and commercial participation in exploration to further U.S. scientific, security and economic interests.” This is also consistent with Griffin’s public remarks: “We believe that when we engage the engine of competition, these services will be provided in a more cost-effective fashion than when the government has to do it.”

Space Power Systems for the 21 st Century

Space power systems upon entering the 21 century are primarily based upon photovoltaic solar arraybattery power for most earth and planetary orbiting satellites and smaller scale systems for planetary landers. Nuclear powered systems using radioisotopes have been reserved for outer planetary science and exploration with space nuclear reactors not being launched since the early 1980s. The recent interest in nuclear space power systems for very high power missions have relegated the development of advanced solar power systems to the study mode. However, these concepts are now emerging for more detailed examination. We review the current concepts for advanced high power solar systems and compare to proposed space nuclear power systems that have been under consideration. We identify the technical and feasibility issues for future development and project other relevant emerging technologies which may be developed in the latter part of the 21 century.

Electromechanical Motion Control Systems in Spacecraft Applications

This paper presents an overview of the fundamental concepts underlying the architecture, design and development of electromechanical motion control systems in spacecraft applications. It draws from applications in the EPS, GNC mainly, motion control through the transfer of energy between an electrical system (motor winding) and a mechanical system (motor load). Section II is devoted to the various types of electrical motors used in these applications including 2 and 3phase steppers, brushless DC and voice coil motors. Section III considers the fundamentals of mechanical systems and in particular, the complex interactions between the load dynamics and the electrical system and how these can have a strong influence in the overall performance of the system. Section IV describes the more common powertrain topologies used to control the transfer of energy from and to the mechanical load including the full bridge, half bridge, and single-ended drive circuits and lastly, Section V describes some of the classical and modern control techniques used to achieve the required control.

Comparison of Propulsion Options for a Lunar Lander Ascent Stage

The propulsion system for the ascent stage of a lunar lander will be required to meet some unusual requirements, including extreme thermal environments and difficult safety objectives. This paper presents the results of an initial study of candidate propulsion options for the ascent stage. The study considered pump-fed and pressure-fed engines using eight propellant types: LOX/hydrogen, LOX/methane, LOX/ethanol, LOX/kerosene, LOX/monomethyl hydrazine (MMH), LOX/silane, nitrogen tetroxide/MMH, and chlorine pentafluoride/hydrazine. The delta-V and thrust to weight requirements for the stage were determined via trajectory simulation. Thermal analysis determined that passive storage of liquid hydrogen and oxygen is feasible for mission durations of a few months. A trade study comparison concluded that pump-fed engines were preferred over pressure-fed engines, and that LOX/LH 2, LOX/ethanol, and N2O4/MMH were the most promising propellant options. Silane and chlorine pentafluoride were found to be impractical, with few desirable systemlevel characteristics and do not merit further consideration.

Benefits of Integrated System Health Management for Increased Operational Responsiveness of Reusable Booster System Launch Vehicles

Air Force plans for future spacelift feature the development of a Reusable Booster System (RBS) to achieve lower flight cost and increased operability. It is expected that the inclusion of Integrated System Health Management (ISHM) will result in significant improvement in the system’s capability to achieve these goals. The present study develops and assesses the ground operations segment for two variations of an RBS vehicle; one which includes ISHM and one which does not. The investigation is conducted using a Lockheed Martin developed flexible discrete-event simulation model for RBS operations analysis. Metrics employed during evaluation include turnaround time, call-up time, and maintenance labor hours per sortie. The model permits Monte Carlo simulation of probabilistic events, resolution of resource contention among parallel processes, determination of need for task performance in a given cycle, and ensures predecessor tasks are completed. Additionally, the model enforces constraints arising from hazardous operations, access, space limitations, and available resources. Given that high variability in task time completion is an inherent feature of launch vehicle processing, task durations are calculated using uncertainty and variability distributions. Simulation results indicate a 34% reduction in turn time hours and a 38% reduction in turn time labor with the inclusion of ISHM capabilities. ISHM-generated knowledge of internal component states results in a reduction of required inspection and needless disassembly operations increasing Operational Responsiveness. ISHM-enabled reductions in call-up time were more modest with a 3% improvement in call-up time and labor versus the No-ISHM RBS system. Additional results indicate that operations tasks such as main engine servicing, commodity loading, structural inspections, and lift and mate operations rank among the longest operations tasks and drive the system turn time. The scope of the present investigation was strictly for nominal ground operations that occurred from horizontal landing through vehicle launch and the results indicate a clear operational advantage for the inclusion of ISHM for RBS. Additional ISHM benefits are expected for flight operations, mission success, and contingency scenarios in either flight or ground segments and would be the recommended direction for additional investigation.

A Space Access Architecture Supporting Large -Scale Space Tourism

The research described in this paper identified reasons why space launch costs are currently in the thousands o f dollars per pound to orbit, identified a potential market for a very high number of launches, and proposed a new space access architecture that may offer two orders of magnitude reductions in per -pound launch costs. The architecture described includes l aunch vehicles, payload carriers, launch vehicle factories, launch sites, orbital facilities, passenger vehicles and orbital transfer vehicles. It is designed to support high volume (100,000 passengers per year) space tourism. The architecture and a cost analysis for it were presented to space industry experts, who were then asked to respond to a questionnaire regarding their opinions of the material presented. The primary result was that the experts found the architecture worthy of more in -depth governm ent - or industry funded study.