Spacecraft Flight Research Articles

Approach and Entry, Descent, and Landing Operations for Mars Science Laboratory

On 5 August 2012, at 2231 hrs, Pacific Daylight Time, the Mars Science Laboratory rover Curiosity landed safely within Gale Crater. The successful landing depended not only upon the flawless execution of the numerous critical activities during the 7 min. entry, descent, and landing but also upon the operational preparations and decisions made by the flight team during approach the final weeks, days, and hours before landing. During this period, decisions made by the flight team balanced operational risk to the spacecraft in flight with any resulting risks incurred during entry, descent, and landing as a result of those decisions. The operations plans made in preparation for approach and entry, descent, and landing readied the operations team for the decisions and actions executed in flight that balanced the operational and entry, descent, and landing risks and prepared the vehicle for a successful landing.

Optical stimulator for vision-based sensors

Abstract We have developed an optical stimulator system for vision-based sensors. The stimulator is an efficient tool for stimulating a camera during on-ground testing with scenes representative of spacecraft flights. Such scenes include starry sky, planetary objects, and other spacecraft. The optical stimulator is used as a test bench to simulate high-precision navigation by different types of camera systems that are used onboard spacecraft, planetary rovers, and for spacecraft rendezvous and proximity maneuvers. Careful hardware design and preoperational calibration of the stimulator result in high precision and long-term stability. The system can be continuously used over several days. By facilitating a full camera including optics in the loop, the stimulator enables the more realistic simulation of flight maneuvers based on navigation cameras than pure computer simulations or camera stimulations without the involvement of the actual optics.

Geomagnetic effect of launches and flights of large spacecraft

The results of observations of variations in the geomagnetic field that accompanied launches and flights of rockets of different types have been analyzed. The launches were performed in 2002–2010 from different space launch facilities of the world (237 events in total), and variations in the range of periods 1–1000 s were studied. Measurements were performed near the city of Kharkov (distance from the spaceports ranges from 1500 to 9500 km). Statistical analysis and spectral estimations have been made, and three groups of disturbances were revealed. Time delays and disturbance durations increased with increasing distance from spaceports. Typical periods were equal to 6 to 14 min, while amplitudes varied in the range 1–3 nT.

COMPARISON OFPIONEER 10,VOYAGER 1, ANDVOYAGER 2ULTRAVIOLET OBSERVATIONS WITH ANTI-SOLAR LYMAN-ALPHA BACKSCATTER SIMULATIONS

Observations made by ultraviolet (UV) detectors on board Pioneer 10, Voyager 1, and Voyager 2 can be used to analyze the distribution of neutral hydrogen throughout the heliosphere, including the interaction regions of the solar wind and local interstellar medium. Previous studies of the long-term trend of decreasing intensity with increasing heliocentric distance established the need for more sophisticated heliospheric models. Here we use state-of-the-art three-dimensional (3D) magnetohydrodynamic (MHD) neutral models to simulate Lyman-alpha backscatter as would be seen by the three spacecrafts, exploiting a new 3D Monte Carlo radiative transfer code under solar minimum conditions. Both observations and simulations of the UV backscatter intensity are normalized for each spacecraft flight path at {approx}15 AU, and we focus on the slope of decreasing intensity over an increasing heliocentric distance. Comparisons of simulations with Voyager 1 Lyman-alpha data results in a very close match, while the Pioneer 10 comparison is similar due to normalization, but not considered to be in agreement. The deviations may be influenced by a low resolution of photoionization in the 3D MHD-neutral model, a lack of solar cycle activity in our simulations, and possibly issues with instrumental sensitivity. Comparing the slope of Voyager 2 and the simulatedmore » intensities yields an almost identical match. Our results predict a large increase in the Lyman-alpha intensity as the hydrogen wall is approached, which would signal an imminent crossing of the heliopause.« less

A solar sailcraft simulation application

An application was created to encourage students’ practical knowledge of gravitational fields, the law of conservation of energy and other phenomena, such as gravitational slingshots. The educational software simulates the flight of a solar sail spacecraft between two planets of the Solar System using the laws of gravity and radiation pressure. The students’ goal can, for example, be to fly from the Earth to Mars.

Modeling Rare Events: Using a Fixed/Variable Rate Model for an Arctic Oil Spill Rate Example

:Occurrence rates for rare events must often be estimated with limited data of unknown and changing applicability; thus, many risk models rely on average measures of risk even though more accurate possibilities may exist. A generalized approach is presented for selecting the best model of the rare event risk and for matching how the results are presented to decision-making needs. The process is illustrated using a case study of estimating oil spill rates from undersea pipelines that serve production platforms on the Outer Continental Shelf areas of the Gulf of Mexico. Existing models use average oil spill rates from these undersea pipelines, but many of these spills occur at a platform; thus, a new approach using a fixed/variable rate framework is suggested. We review the literature on modeling of Outer Continental Shelf oil spill rates, analyze historical oil spills for the estimated rates for both models, and contrast the results (that can differ by up to a factor of 2) for Arctic applications. Other quantitative applications for deeper, more distant wells in the Gulf of Mexico, air and spacecraft flights, maintenance of nuclear facilities, and failure of project activities are suggested. The proposed model is based on estimating average rates for the fixed and variable components. This model is placed on a continuum of risk models based on their data requirements, which provides a new conceptual framework for risk model “levels.” Implications for qualitative mental models of risk are also suggested; thus, there are many potential applications in risk models used by managers and operators.

The methodology of variable management of propellant fuel consumption by jet-propulsion engines of a spacecraft

Traditionally, management of propellant fuel consumption on board of a spacecraft is only associated with the operation of jet-propulsion engines (JPE) that are actuator devices of motion control systems (MCS). The efficiency of propellant fuel consumption depends not only on the operation of the MCS, but also, to one extent or another, on all systems functioning on board of a spacecraft, and on processes that occur in them and involve conversion of variable management of propellant fuel consumption by JPEs as a constituent part of the control of the complex process of spacecraft flight.

A requirements-based, bottom-up SLOC estimate and analysis of NASA’s Orion crew exploration vehicle spacecraft flight software

Estimating the size and amount of resources required to develop a large and complex software system is challenging. Early in a project lifecycle, requirements for the system may be immature and fun...

Impulsive Control for Formation Flight About Libration Points

The concept of formation flight of multiple spacecraft, near the libration points of the sun-Earth system, offers many possibilities for space exploration. This study focuses on the use of impulsive control to maintain formation flight in the circular restricted three-body problem. Two specific tasks are accomplished in this paper. First, the tangent targeting method, based on a two-level differential correction, is formulated to fully exploit the predetermined error bound. A comparison between the tangent targeting method and traditional targeting method shows that the number of maneuvers can be significantly reduced and the length of time between successive maneuvers can be greatly increased by using the tangent targetingmethod. The study of the practical convergence of the algorithm is also discussed. The second task is the proposal of a tangent targeting method-based formationkeeping strategy for handling uncertainty introduced by the thrust implementation error. A tradeoff between the formation-keeping accuracy and the number of maneuvers is achieved. Monte Carlo analysis, including 100 trials, demonstrates the effectiveness of this strategy.

Fuzzy incremental control algorithm of loop heat pipe cooling system for spacecraft applications

Reliable and high precision thermal control technologies are essential for the safe flight of advanced spacecraft. A fuzzy incremental control strategy is proposed for control of an LHP space cooling system comprising a loop heat pipe and a variable emittance radiator with MEMS louver. The generating and performing algorithm of the fuzzy control rules is provided with an analytical form based on the understanding of dynamics and control mechanisms of the space cooling system. This paper also presents a novel integrated mathematical model for the dynamic analysis of the LHP space cooling system and a numerical evaluation of the investigated control schemes. Numerical simulation results on the closed loop control effects suggest that the proposed control strategy takes advantage of no steady error, small overshoots and short settling times; thus benefiting safe, highly accurate and reliable operation of the entire space cooling system. The overshoots of the most important operating parameters (Tob, Qr, and P) under the proposed fuzzy incremental control have been reduced to 16.3%, 17.6% and 18.6% of the compared PID control’s, while the respective settling times have been shortened to 33.9%, 42.3% and 30.5% of the reference values.

A historical compilation of software metrics with applicability to NASA’s Orion spacecraft flight software sizing

Estimating the size of a large and complex software system is a challenging task. Early in a project's life cycle, when requirements for the system may be immature and functionality defined only at a high level, resource profiles are necessary for appropriate funding, staffing, and development of a viable project plan. Similar project historical software size data and trends provide a tool to predict software size, creating a feasible estimation approach. To confidently estimate the flight software required for the Orion Spacecraft, NASA conducted an analysis of similar space and aircraft software systems. This paper presents the results of a study that compiled data from over 400 spacecraft, aircraft, and submarine software projects, which were functionally similar in nature to the Orion spacecraft flight software. The study includes the analysis and summary of overall trends in software size, development strategies, and processes. The results indicate a well-correlated upward trend in software size over time for both crewed and uncrewed space and aircraft. This trend was used to predict the estimated completed size of the Orion flight software at approximately 2.3 million Source Lines of Code (SLOC).

飞船光学瞄准镜分划板位置误差分析

The optical sight,as a measurement unit for the manned spacecraft,is used to observe the earth.It helps to determine the spacecraft's flight path and flight profile for the astronaut.The optical projector screen reticle plays an important role in the optical sight.Its position accuracy directly affects the determination to the spacecraft profile for the astronaut.The detailed analysis of the position error factors on the optical sight reticle is conducted.The main factor on the reticle position error is determined.The maximum translation amount between the actual position and the ideal location of the reticle is obtained by calculations.

Modelling ion propulsion plume interactions with spacecraft in formation flight

AbstractThis paper presents a simulation study of ion thruster plume effects on formation flying spacecraft. Two formation flight applications using micro-ion propulsion are considered: an L2-Halo orbit interferometer formation and a LEO micro-satellite formation. Worst case scenarios in both missions have been investigated. We focus our study on thruster configurations resulting in possible indirect plume impingement on satellites outside of the direct impingement zone. Indirect impingement which cannot be predicted except through plasma simulation or in-flight measurements might expose critical spacecraft elements such as optical sensors to a harsh contamination environment. A high-fidelity electrostatic plasma simulation code for parallel computing platforms was used in the study.In our study, we found that using miniature scale ion propulsion in both formation missions creates a very low charge-exchange plasma environment which results in tolerable contamination environment for other spacecraft in the formation.

Influence of anisotropic fluctuations of the ionosphere plasma density on deep radio sounding by a ultra wide band radar with synthesized aperture

The problem of deep sounding of planet interior using ultra wide band radar with synthesized aperture is considered for the case when anisotropic fluctuations of the ionosphere plasma density take place. Modeling is performed for a number of values of the medium and radar characteristic parameters. The degree of influence of mutual orientation of the anisotropy direction of ionospheric fluctuations and of the spacecraft flight trajectory is estimated. It is demonstrated that widening of radar pulses is determined by characteristic spatial scale of ionosphere plasma disturbances in the transverse direction relative to the spacecraft flight trajectory. On the other hand, attenuation of the peak power of the pulses is shown to be determined basically by the longitudinal scale of disturbance correlations.

Challenges and Solutions for Embedded and Networked Aerospace Software Systems

Aerospace systems are increasingly dependent upon software for their functionality, with associated software spanning a wide range of application domains. These include aircraft and spacecraft flight controls, mission computing, weapons management, command and control, surveillance, sensor management and processing, telemetry, and more. Understanding of their unique challenges has driven technology development on many fronts associated both with the products - such as real-time component-based application frameworks, supporting middleware, and algorithms - and the processes and tools by which they are created - such as model-based development and integration, automated code generation, simulations, and desktop test environments. This paper describes a number of these domains and challenges, future directions associated with networking and systems of systems, and technologies facilitating their development within The Boeing Company.

Laser corrective propulsion plant for spacecraft

This paper discusses questions of using laser reactive thrust for conducting flights of spacecraft both in near-earth orbit and in interplanetary flights as a corrective propulsion plant with an aerospace laser reactive engine.

Reliability enhancement of digital combinational circuits based on evolutionary approach

Reliability has become an integral part of the system design process, especially for those systems with life-critical applications such as aircrafts and spacecraft flight control. The recent rapid growth in demand for highly reliable digital circuits has focused attention on tools and techniques we might use to enhance the reliability of the circuit. In this paper, we present an algorithm to improve the reliability of digital combinational circuits based on evolutionary approach. This method generates a global VHDL file for the selected initial set of components based on inserting multiplexers at the gate inputs of the circuit which helps to perform the simulations in only one session. This simulation framework is combined with single-pass reliability analysis approach to implement the evolutionary algorithm. The search space of the genetic algorithm is limited by the idea of slicing the initial set of components and also circuit partitioning could be used to further overcome the scalability limitations. The framework is applied to a subset of combinational benchmark circuits and our experiments demonstrate that higher reliabilities can be achieved while other factors such as power, speed and area overhead will remain admissible.

Complex diagnostics of disturbances in the ionospheric plasma parameters far from the trajectories of launched rockets

Large-scale disturbances in the ionospheric plasma, caused by the spacecraft launches from the Baikonur site, have been analyzed based on the incoherent scatter radar measurements. The altitude-time dependences of the main plasma parameters (electron density and electron and ion temperatures at altitudes of ∼100–600 km) have been analyzed. It has been indicated that spacecraft launches and flights are accompanied by the generation of wave-like disturbances in all considered parameters. It has been obtained that the relative amplitudes of these wave-like disturbances were usually 0.03–0.10, and the variation period was 20–60 min. The variations were shifted in phase relative to each other. The propagation velocities of wave-like disturbances were ∼0.5–0.6 and 1.5–2 km/s. The up-to-date methods of spectral analysis, including the wavelet analysis, were used to estimate the parameters of the wave-like disturbances.

The Herschel/Planck programme, technical challenges for two science missions, successfully launched

The two science missions Herschel, an observatory-type mission, and Planck, a survey mission, are combined in one programme within ESA long-term science programme. Herschel, an observatory mission, will target the largely unexplored infrared and sub-millimetre part of the electromagnetic spectrum from 60 to 670 μm with three scientific instruments. As a survey mission, the objective for Planck is to image systematically the whole sky simultaneously with two scientific instruments in nine frequency channels between 30 and 900 GHz to unravel the temperature fluctuations, the anisotropy, of the cosmic background radiation. For both satellites, which have been launched from the European Space Port in Kourou, French Guiana, on a single Ariane 5 launcher, the orbits are Lissajous orbits around the 2nd Lagrange Point L2 of the Earth–Sun system. Having surpassed the technological problems and the validation of the instruments, this paper will recall the Herschel and Planck spacecraft's characteristics, the mission aspects and the science requirements. The integration and acceptance verification of both spacecraft flight models being complete, this paper will highlight the development and spacecraft level acceptance tests status and focus on the major milestones up to the launch from Kourou on Ariane 5 successfully achieved on May 14, 2009.

Minimum-time Earth–Moon and Moon–Earth orbital maneuvers using time-domain finite element method

In this paper, the minimum-time orbital trajectories for Earth–Moon and Moon–Earth flights of a continuous-thrust spacecraft are obtained by the time-domain finite element method. The problem is formulated using a simplified version of the restricted three-body model at the Cartesian coordinate system. Moreover, the performance index is considered as the minimum-time problem with free final time. Through the calculus of variation, the problem is discretized in the time-domain and the resulting equations are constructed in finite element form. Finally, by setting out the discrete equations, a set of nonlinear algebraic equations is generated. The optimum answer is then attained using the Newton–Raphson method. The capability of the time-domain finite element method is examined to verify its accuracy. The trajectory results are also compared with the published results and good agreement is observed. Numerical simulations highlighting the effects of the effective exhaust velocity parameter on the shape of flight trajectory and time-of-flight are presented.