New trade tree for manned mars missions

Recent studies on human missions to Mars suggest revisiting the parameters that have the most important impact on the complexity, the initial mass in low Earth orbit, the risks and the development costs for the first journey to the red planet. In the last NASA reference mission, a trade tree is proposed.     

Roadmap to a human Mars mission

We propose a new roadmap for the preparation of the first human mission to Mars. This proposal is based on the work of ISECG and several recent recommendations on human Mars mission architectures. A table is proposed to compare the possible benefits of different preparatory missions. Particular attention is paid to the possibility of qualifying important systems thanks to a heavy Mars sample return mission. It is shown that this mission is mandatory for the qualification of Mars aerocapture at scale-1, EDL systems at scale 1 and Mars ascent. Moreover, it is a good opportunity to test many other systems, such as the heavy launcher and the transportation systems for the trips beyond LEO. These tests were not mentioned in the last ISECG report. This strategy is facilitated in the case of the simplified Mars mission scenarios that have recently been presented because it is suggested that relatively small vehicles with small crew sizes are used in order to optimize the payload mass fraction of the landing vehicles and to avoid the LEO assembly. An important finding of the study is that a human mission to the surface of the Moon is not required for the qualification of the systems of a human mission to Mars. Since affordability is a key criterion, two important missions are proposed in the roadmap. The first is a heavy Mars sample return mission and the second is a manned mission to a high Earth orbit or eventually to the vicinity of the Moon. It is shown that both missions are complementary and sufficient to qualify all the critical systems of the Mars mission.     

Debris area distribution of spacecraft under hypervelocity impact

Cross-sectional area is an important parameter for spacecraft breakup debris as it is the directly measured data in space observation. It is significant for observing and analysing the spacecraft breakup event to accurately modelling the area distribution of the breakup debris. In this paper, experimental study has been performed on debris area distribution characteristics of spacecraft under hypervelocity impact. The tests are carried out at the ballistic ranges of CARDC. Aluminium projectiles are launched to normally impact the simulated spacecrafts at about 3.0 km/s. The simulated spacecrafts are made up of aluminium plates, filled with some simulated electronics boxes, each of which was installed with a circuit board. “Soft-catch” devices are used to recover the breakup fragments. The test results show that: 1) the relationship between the cross-sectional area and the characteristic length of debris, which can be obtained in the logarithmic coordinates by linear fitting, represents the debris shape characteristic in a certain extent; 2) the area-to-mass ratios of fragments show normal distributions in the logarithmic coordinates; 3) debris made of different materials can be distinguished by different peaks on the distribution curves; 4) the area-to-mass ratio distributions can be expressed by a linear superimposition of several normal functions which represent the main materials of the spacecraft.     

Human space exploration - A global trans-cultural quest

This Viewpoint is a slightly edited version of the ‘Statement by Space Explorers on Human Space Exploration’ produced in the wake of a workshop organized by the European Space Policy Institute and held in Vienna in May 2010. While noting the cultural differences in understandings of ‘exploration’ around the world, it also affirms the phenomenon as a globe-wide, human urge, emphasizing that only the physical presence of a human being can assure the full emotional quality of exploration. It calls upon decision makers to regard human space exploration as a global trans-cultural quest that should be supported and furthered.     

Dawn′s exploration of Vesta

On 16 July 2011, after completing nearly four years of interplanetary flight, Dawn entered orbit around (4) Vesta, the second most massive body in the main asteroid belt. Dawn used solar electric propulsion to spiral to six different orbits to accomplish its science campaign. Although the transfers to progressively lower orbits presented significant challenges, all were executed smoothly. During its nearly 14 months in orbit, Dawn spiraled down to 210 km above the surface and back up before initiating the gradual departure to travel to dwarf planet (1) Ceres for a 2015 rendezvous. Dawn′s exploration of Vesta has shown it to be geologically complex and fascinating, resembling terrestrial planets more than typical asteroids. Among the principal features is a 500-km-diameter impact basin within which is the second tallest mountain known in the solar system. This paper presents Dawn′s operations at Vesta and summarizes the principal findings.     

Space solar arrays and concentrators

This paper presents some research activities conducted at the Centre Spatial de Liege (CSL) in the field of space solar arrays and concentration.With the new generation of high efficiency solar cells, solar concentration brings new insights for future high power spacecrafts. A trade-off study is presented in this paper. Two different trough concentrators, and a linear Fresnel lens concentrator are compared to rigid arrays. Thermal and optical behaviors are included in the analysis.Several technical aspects are discussed:

• Off-pointing with concentrators induces collection loss and illumination non uniformity, reducing the PV efficiency.

• Concentrator deployment increases the mission risk.

• Reflective trough concentrators are attractive and already proven. Coating is made of VDA (Aluminum). A comprehensive analysis of PV conversion increase with protected silver is presented.

• Solar concentration increases the heat load on solar cells, while the conversion efficiency is significantly decreasing at warm temperatures.

To conclude, this paper will point out the new trends and the key factors to be addressed for the next generation of solar generators.