NASA's new Mars Exploration Program: the trajectory of knowledge

NASA's newly restructured Mars Exploration Program (MEP) is finally on the way to Mars with the successful April 7 launch of the 2001 Mars Odyssey Orbiter. In addition, the announcement by the Bush Administration that the exploration of Mars will be a priority within NASA's Office of Space Science further cements the first decade of the new millennium as one of the major thrusts to understand the "new" Mars. Over the course of the past year and a half, an integrated team of managers, scientists, and engineers has crafted a revamped MEP to respond to the scientific as well as management and resource challenges associated with deep space exploration of the Red Planet. This article describes the new program from the perspective of its guiding philosophies, major events, and scientific strategy. It is intended to serve as a roadmap to the next 10-15 years of Mars exploration from the NASA viewpoint. [For further details, see the Mars Exploration Program web site (URL): http://mars.jpl.nasa.gov]. The new MEP will certainly evolve in response to discoveries, to successes, and potentially to setbacks as well. However, the design of the restructured strategy is attentive to risks, and a major attempt to instill resiliency in the program has been adopted. Mars beckons, and the next decade of exploration should provide the impetus for a follow-on decade in which multiple sample returns and other major program directions are executed. Ultimately the vision to consider the first human scientific expeditions to the Red Planet will be enabled. By the end of the first decade of this program, we may know where and how to look for the elusive clues associated with a possible martian biological record, if any was every preserved, even if only as "chemical fossils."     

Experiment LEND of the NASA Lunar Reconnaissance Orbiter for high-resolution mapping of neutron emission of the Moon

The scientific objectives of neutron mapping of the Moon are presented as 3 investigation tasks of NASA's Lunar Reconnaissance Orbiter mission. Two tasks focus on mapping hydrogen content over the entire Moon and on testing the presence of water-ice deposits at the bottom of permanently shadowed craters at the lunar poles. The third task corresponds to the determination of neutron contribution to the total radiation dose at an altitude of 50 km above the Moon. We show that the Lunar Exploration Neutron Detector (LEND) will be capable of carrying out all 3 investigations. The design concept of LEND is presented together with results of numerical simulations of the instrument's sensitivity for hydrogen detection. The sensitivity of LEND is shown to be characterized by a hydrogen detection limit of about 100 ppm for a polar reference area with a radius of 5 km. If the presence of ice deposits in polar "cold traps" is confirmed, a unique record of many millions of years of lunar history would be obtained, by which the history of lunar impacts could be discerned from the layers of water ice and dust. Future applications of a LEND-type instrument for Mars orbital observations are also discussed.     

Cost effectiveness requirements for space power stations

The concept of converting solar energy in orbital space stations and transmitting electrical power to Earth at radio frequency, is receiving increasing attention both in paper studies and experimental and development work. The projects conceived are large in scale and implications and will demand major resources in their development and deployment. In addition to the technological requirements, the problem of reaching international decisions at political levels to fund and operate such systems will be immense. It will therefore be essential to establish as accurately as possible the basic parameters which will lead to a viable project, particularly with regard to economics.

This paper, therefore, examines the requirements which together will determine the appropriate levels of cost effectiveness of space power stations and should assist in establishing critical or sensitive areas which will influence the operational validity of the concepts. The r.f. transmission of electric power to and from, or between, spacecraft may itself have wider implications and is another aspect considered in the paper.

In summary, the paper does not seek to introduce new design concepts, but appraises the situation and exposes indicators concerning cost effectiveness.     

Characterizing high-energy-density propellants for space propulsion applications

A technique for computationally determining the thermophysical properties of high-energy-density matter (HEDM) propellants is presented. HEDM compounds are of interest in the liquid rocket engine industry due to their high density and high energy content relative to existing industry-standard propellants. In order to accurately model rocket engine performance, cost and weight in a conceptual design environment, several thermodynamic and physical properties are required over a range of temperatures and pressures. The approach presented here combines quantum mechanical and molecular dynamic (MD) calculations and group additivity methods. A method for improving the force field model coefficients used in the MD is included. This approach is used to determine thermophysical properties for two HEDM compounds of interest: quadricyclane and 2-azido-N,N-dimethylethanamine (DMAZ). The modified force field approach provides results that more accurately match experimental data than the unmodified approach. Launch vehicle and Lunar lander case studies are presented to quantify the system level impact of employing quadricyclane and DMAZ rather than industry standard propellants. In both cases, the use of HEDM propellants provides reductions in vehicle mass compared to industry standard propellants. The results demonstrate that HEDM propellants can be an attractive technology for future launch vehicle and Lunar lander applications.     

嫦娥二号卫星技术特点分析

嫦娥二号卫星是我国的第二颗月球探测器,作为探月工程二期的先导星进行飞行试验,并试验探月工程二期的部分关键技术,以深化月球科学探测。文章介绍了嫦娥二号卫星在轨道设计、高灵敏度X频段深空应答机等6方面的技术特点及解决措施。     

Improved cost monitoring and control through the Earned Value Management System

As economic pressure and competition for budget among federal agencies has increased, there has been an increasing need for more granular data and robust management information systems. This is especially true for the execution of major civilian space programs. This need has resulted in new program management requirements being implemented in an attempt to limit cost and schedule growth. In particular, NASA Procedural Requirements (NPR) 7120.5D requires the implementation of an Earned Value Management System (EVMS) compliant with the requirements of American National Standards Institute (ANSI)/Electronic Industries Alliance Standard 748-B. The Radiation Belt Storm Probes (RBSP) program management team at The Johns Hopkins University Applied Physics Laboratory (JHU/APL) made a decision to implement an EVMS on RBSP during Phase B—a year earlier than specified in the contractual Phase C reporting requirement as defined in the NPR. This decision was made so that the project would have the benefit of 12 months of training and hands-on implementation during Phase B. Although there were a number of technical and process hurdles encountered during Phase B and into Phase C, the system was working well when the Integrated Baseline Review (IBR) was held in August 2009. The IBR was a success because it met the review requirements. It was also clear to all IBR participants that the EVMS was providing value to the project management team. Although the IBR pointed out some areas of concern regarding process and ANSI compliance, the system had markedly improved the project's ability to monitor cost and schedule. This, in turn, allowed the project team to foresee problems in advance, formulate corrective actions, and implement course corrections without causing significant adverse impact to the project. Opponents of EVMS systems often communicate the unfavorable opinion that EVMS systems create unnecessary cost and administration. Although it is undeniable that EVMS implementation does not occur without cost, the cost is minimal in comparison to the benefits of successful implementation. This paper will focus on the implementation of EVMS on the RBSP project, explain EV processes and the implementation's cost, and analyze the benefits of EVMS to provide insight into cost/benefit considerations for other projects considering EVMS implementation. This paper will do this by focusing on the following points: (1) RBSP is the first full-up implementation of earned value management (EVM) at JHU/APL; (2) RBSP EVM started in Phase B; (3) RBSP EVM implementation has been working well in Phase C/D; (4) RBSP EVM implementation has been recognized by Goddard Space Flight Center and NASA Headquarters as successful; and (5) an assessment of the benefits of EVMS to the project management team and sponsor shows that the system's benefits outweigh the cost of implementation.     

Space Phoenix

The US federal government is collaborating with a non-profit university consortium and its commercial project managers to develop the Space Shuttle fleet's expended external fuel tanks for scientific and commercial uses in space. Nearly a half dozen years in evolution, the Space Phoenix Program is a private-sector civil space programme with the long-term goal of opening the Earth's space to as many people, organizations and activities as possible, as soon as possible, and at the lowest cost to them as possible. In time it is expected to be a major focus for private-sector activities in space. This report describes how it will work.     

The Hidden Costs of Reliability and Failure in Launch Systems

In comparing the costs of different launch vehicles, the possibility of the risk of failure is assumed to be accounted for by the cost of insurance. The satellite may be insured against loss during launch, and the launch services provider may offer a free relaunch. However, actual costs of reliability and failure extend beyond this. Each failure necessitates an investigation and a get well programme by the operating agency, while putting the operations team on hold until services can resume. A commercial operator may also lose customer revenue and actual customers through loss of confidence or unavailability. Such costs tend to be hidden, and not evaluated in assessing the effectiveness of a system, but count towards total costs. Failure investigations help to improve system reliability, but this could equally have been achieved by expenditure in development and qualification. Reusable launch vehicles will have different costs associated with reliability and failure. The relationship between reliability and cost, properly assessed, ought to influence the design of both expendable and reusable launch systems.     

The hidden costs of reliability and failure in launch systems

In comparing the costs of different launch vehicles, the possibility of the risk of failure is assumed to be accounted for by the cost of insurance. The satellite may be insured against loss during launch, and the launch services provider may offer a “free relaunch.” However, actual costs of reliability and failure extend beyond this. Each failure necessitates an investigation and a “get well” programme by the operating agency, while putting the operations team “on hold” until services can resume. A commercial operator may also lose customer revenue and actual customers through loss of confidence or unavailability. Such costs tend to be hidden, and not evaluated in assessing the effectiveness of a system, but count towards total costs. Failure investigations help to improve system reliability, but this could equally have been achieved by expenditure in development and qualification. Reusable launch vehicles will have different costs associated with reliability and failure. The relationship between reliability and cost, properly assessed, ought to influence the design of both expendable and reusable launch systems.     

A Lunar Laser Ranging Retroreflector Array for the 21st Century

Over the past 40 years, the Lunar Laser Ranging Program (LLRP) to the Apollo Cube Corner (CCR) Retroreflector Arrays (ALLRRA) [1] has supplied almost all of the significant tests of General Relativity. The LLRP has evaluated the PPN parameters, addressed the possible changes in the gravitational constant and the properties of the self-energy of the gravitational field. In addition, the LLRP has provided significant information on the composition and origin of the moon. This is the only Apollo experiment that is still in operation. Initially the ALLRRAs contributed a negligible fraction of the ranging error budget. Over the decades, the ranging capabilities of the ground stations have improved by more than two orders of magnitude. Now, because of the lunar librations, the existing Apollo retroreflector arrays contribute a significant fraction of the limiting errors in the range measurements.The University of Maryland, as the Principal Investigator for the original Apollo arrays, is now proposing a new approach to the Lunar Laser Array technology [2]. The investigation of this new technology, with Professor Currie as Principal Investigator, is currently being supported by two NASA programs and by the INFN-LNF in Frascati, Italy. Thus after the proposed installation during the next lunar landing, the new arrays will support ranging observations that are a factor 100 more accurate than the current ALLRRAs.The new fundamental cosmological physics and the lunar physics [3] that this new Lunar Laser Ranging Retroreflector Array for the 21st Century (LLRRA-21) can provide will be described. In the design of the new array, there are three major challenges: (1) validate the ability to fabricate a CCR of the required specifications, which is significantly beyond the properties of current CCRs, (2) address the thermal and optical effects of the absorption of solar radiation within the CCR, reduce the transfer of heat from the CCR housing and (3) validate an accurate emplacement technique to install the CCR package on the lunar surface. The latter requires a long-term stable relation between the optical center of the array and the deep regolith, that is, below the thermally driven expansion and contraction of the regolith during the lunar day/night cycle.     

Recent advances in lunar base simulation

This article reports about the results of the latest computer runs of a lunar base simulation model. The lunar base consists of 20 facilities for lunar mining, processing and fabrication. The infrastructure includes solar and nuclear power plants, a central workshop, habitat and farm. Lunar products can be used for construction of solar power systems (SPS) or other spacecraft at several space locations. The simulation model evaluates the mass, energy and manpower flows between the elements of the system as well as system cost and cost of products on an annual basis for a given operational period. The 1983 standard model run over a fifty-years life cycle (beginning about the year 2000) was accomplished for a mean annual production volume of 78 180 Mg of hardware products for export resulting in average specific manufacturing cost of 8.4 $/kg and total annual cost of 1.25 billion dollars during the life cycle. The reference space transportation system uses LOX/LH₂ propulsion for which at the average 210 500 Mg LOX per year is produced on the moon. The sensitivity analysis indicates the importance of bootstrapping as well as the influence of market size, space transportation cost and specific resources demand on the mean lunar manufacturing cost. The option using lunar resources turns out to be quite attractive from the economical viewpoint. Systems analysis by this lunar base model and further trade-offs will be a useful tool to confirm this.     

Cospas-Sarsat: a quiet success story

This article will look at the origins of the Cospas-Sarsat International cooperative space program and its transition in the mid-1980s from a technical demonstration to an operational program. It will then attempt to identify some of the reasons for its success, with a view toward determining their applicability to other joint space applications projects.     

Psycho-social training for man in space.

In preparation for the international manned space station various international and national space agencies are already participating with the Russian MIR programme with short, medium, and long term presence on the MIR station. Although selection criteria for all crew include careful psychological screening, with some effort also regarding team build-up, this has proved insufficient; moreover. little or no effort is expended in the area of psycho-social- or team training. This paper propounds the authors' thesis that, in addition to the steps already being taken, psycho-social training is essential for long-duration flight. A concrete proposal is made for such a training program, with an overview of how such a program will look like; examples of past applications are given.     

基于SQP方法的常推力月球软着陆轨道优化方法

月球软着陆是未来月球探测中的一项关键技术。针对这项技术，本文给出了一种基于SQP方法的常推力月球软着陆轨道优化方法。该方法通过将常推力月球软着陆轨道离散化，利用离散点处状态连续作为约束条件，把常推力月球软着陆轨道优化问题归结为一个非线性规划问题，对于此问题的求解，其初值均为有物理意义的状态和控制量，从而避免了采用传统优化方法在解决此优化问题时对没有物理意义变量初值的猜测。最后，利用SQP方法求解了此轨道优化问题。仿真计算结果表明这种离散化的方法应用于此轨道优化问题可以避免传统轨道优化方法对初值敏感的问题。     

Self-propagating high-temperature reactions for the fabrication of Lunar and Martian physical assets

The development of a new process potentially useful for future manned Lunar and/or Martian space missions in the framework of the so-called ISRU (In-Situ Resource Utilization) and ISFR (In-Situ Fabrication and Repair) concepts is described and discussed in this work. This process involves the fabrication of physical assets by self-propagating high temperature synthesis (SHS) for construction applications in Lunar and Martian environments starting from different Lunar or Martian regolith simulants and aluminum, as reducing agent. In addition, although Moon and Mars already contain ilmenite (FeTiO₃) and iron oxides, respectively, the latter ones are also added to the initial mixtures to promote suitable SHS reactions. A complete scheme for the fabrication of physical assets to be used as protection against solar rays, solar wind and meteoroids, where all required stages are indicated, is finally proposed in the framework of a recently filed patent.     

A proposed strategy against cost overruns in the space sector: The 5C approach

The space sector has frequently been confronted with cost overruns, with a negative impact on its management reputation. There are many reasons for this effect, the main one being that space development contracts are unique and often do not allow proper cost benchmarking. On the other hand, tools have been developed to minimise this effect and it is important to train future space managers in applying such tools. In the International Space University, such methods are illustrated with workshops, which aim to be as close as possible to reality. This article will describe the different techniques, memo-technically called the 5C approach here, and develop the use of a computerised tool, PRICE, to support these techniques in the different phases of the projects.     

Scientific investigations at a lunar base.

Scientific investigations to be carried out at a lunar base can have significant impact on the location, extent, and complexity of lunar surface facilities. Among the potential research activities to be carried out are: (1) Lunar Science: Studies of the origin and history of the Moon and early solar system, based on lunar field investigations, operation of networks of seismic and other instruments, and collection and analysis of materials; (2) Space Plasma Physics: Studies of the time variation of the charged particles of the solar wind, solar flares and cosmic rays that impact the Moon as it moves in and out of the magnetotail of the Earth; (3) Astronomy: Utilizing the lunar environment and stability of the surface to emplace arrays of astronomical instruments across the electromagnetic spectrum to improve spectral and spatial resolution by several orders of magnitude beyond the Hubble Space Telescope and other space observatories; (4) Fundamental physics and chemistry: Research that takes advantage of the lunar environment, such as high vacuum, low magnetic field, and thermal properties to carry out new investigations in chemistry and physics. This includes material sciences and applications; (5) Life Sciences: Experiments, such as those that require extreme isolation, highly sterile conditions, or very low natural background of organic materials may be possible; and (6) Lunar environmental science: Because many of the experiments proposed for the lunar surface depend on the special environment of the Moon, it will be necessary to understand the mechanisms that are active and which determine the major aspects of that environment, particularly the maintenance of high-vacuum conditions. From a large range of experiments, investigations and facilities that have been suggested, three specific classes of investigations are described in greater detail to show how site selection and base complexity may be affected: (1) Extended geological investigation of a complex region up to 250 kilometers from the base requires long range mobility, with transportable life support systems and laboratory facilities for the analysis of rocks and soil. Selection of an optimum base site would depend heavily on an evaluation of the degree to which science objectives could be met. These objectives could include lunar cratering, volcanism, resource surveys or other investigations; (2) An astronomical observatory initially instrumented with a VLF radio telescope, but later expanding to include other instruments, requires site preparation capability, "line shack" life support systems, instrument maintenance and storage facilities, and sortie mode transportation. A site perpetually shielded from Earth is optimum for the advanced stages of a lunar observatory; (3) an experimental physics laboratory conducting studies requiring high vacuum facilities and heavily instrumented experiments, is not highly dependent on lunar location, but will require much more flexibility in experiment operation and EVA capability, and more sophisticated instrument maintenance and fabrication facilities.     

Economics of the solid rocket booster for space shuttle

Solid Rocket Boosters (SRB's) became viable contenders as the booster for the Space Transportation System (STS) early in the concept studies of Space Shuttle because of their low development cost compared with equivalent liquid propellant boosters. Program risks and costs have been held down by scaling and adapting existing technology to the 146 in. SRB selected for development. To retain this low cost edge for the operational phase, NASA has concentrated on maintaining or reducing the cost of expendables and has demonstrated the feasibility of reusing the expensive nonexpendable SRB hardware. Drop tests of Titan III motor cases and nozzles in 1973 proved that boosters could survive water impact at vertical velocities of approx. 100 ft/s. SRB components have been designed with reuse in mind. In most cases, hardware designed for ascent will withstand water impact loads with little modification.

Cost effective refurbishment is a foremost design consideration. Continuing review of each component assures that design for reusability and/or cost of refurbishment does not become so costly that a low-cost expendable approach may be more cost effective.

The cost of expendables has been minimized by selecting proven propellants, insulations, and nozzle ablatives whose costs are well known. The propellant, which is approx. 95% of the expendables, is the lowest cost composite formulation available. As lower cost ablative materials such as pitch carbon fibers become available in quantity and are reliably demonstrated, they will be introduced to reduce operations costs.

Thus, by use of proven technology, low cost expendables and reuse of more expensive non-expendables, the development and operations costs of SRB's are held to a level that make the SRB an economical booster for the Space Shuttle.