Thrust modulation of solid propellant rockets by a fluidic vortex valve with secondary combustion

An analytical model for calculation of the thrust and pressure modulation of a solid propellant rocket by means of a fluidic vortex valve with secondary combustion has been developed. Thrust control by the vortex valve method was found superior to the axial injection of control flow. Addition of oxygen in the injected flow improves the energetic performance of the system as well as the thrust modulation capability. Experiments have been conducted using a mixture of nitrogen and oxygen as the injection gas. The two main parameters investigated in a series of experiments were the oxygen percentage in the injection gas and the ratio between the mass flow rates of the control gas and the solid propellant combustion products. The results show an increase of thrust by a factor of 2 for a 25% addition in mass flow rate by secondary injection at optimal conditions.     

Potential Effects of Surface Temperature Variations and Disturbances and Thermal Convection on the Mars InSight HP<Superscript>3</Superscript> Heat-Flow Determination

The HP³ instrument on the InSight lander mission will measure subsurface temperatures and thermal conductivities from which heat flow in the upper few meters of the regolith at the landing site will be calculated. The parameter to be determined is steady-state conductive heat flow, but temperatures may have transient perturbations resulting from surface temperature changes and there could be a component of thermal convection associated with heat transport by vertical flow of atmospheric gases over the depth interval of measurement. The experiment is designed so that it should penetrate to a depth below which surface temperature perturbations are smaller than the required measurement precision by the time the measurements are made. However, if the measurements are delayed after landing, and/or the probe does not penetrate to the desired depth, corrections may be necessary for the transient perturbations. Thermal convection is calculated to be negligible, but these calculations are based on unknown physical properties of the Mars regolith. The effects of thermal convection should be apparent at shallow depths where transient thermal perturbations would be observed to deviate from conductive theory. These calculations were required during proposal review and their probability of predicting a successful measurement a prerequisite for mission approval. However, their uncertainties lies in unmeasured physical parameters of the Mars regolith.     

Corotating interplanetary streams and associated ionospheric disturbances at Venus and Earth

During the summer of 1979, solar coronal structure was such that a sequence of recurrent regions produced a corresponding sequence of corotating solar wind streams, with pronounced downstream signatures. One of these stream events passed Earth on July 3, and was observed later at Venus late on July 11th, with similar characteristics. Corresponding in-situ measurements at Earth from the Atmospheric Explorer-E satellite and at Venus from the Pioneer Venus Orbiter are examined for evidence of comparable perturbations of the planetary ionospheres. The passage of the stream shock front is found to be associated with pronounced fluctuations in n(0⁺) which appear as pronounced local depletion of ion concentrations in both ionospheres. The ionosphere disturbances appear to be closely associated with large variations in the solar wind momentum flux. The implied local ionospheric depletions observed at each planet are interpreted to be the consequence of plasma redistribution, rather than actual depletions of plasma.     

Software assisted authoring and viewing of ISS crew procedures

The European Space Agency (ESA) initiated a joint project with the National Aeronautics and Space Administration (NASA) and industry partners for improved authoring and execution of Operations Data File (ODF) procedures. The system consists of an authoring tool and a viewer. The authoring tool is currently used by NASA and ESA to write/convert ODF procedures. The viewer will be used onboard the International Space Station (ISS) starting from Flight Increment 11. The new system, thanks to its interaction capability, will help astronauts and operators in the execution of checklist and logic flow procedures that ensure precise performance of experiments and smooth operation of the various systems.     

仍旧是最前沿的降地

NASA的马歇尔航空中心(位于阿拉巴马州的Hunstville)无疑要肩负更具挑战性的重要使命,因为他们需要负责研发一系列大型地月火箭发射至月球上的指定地点.时至今日,马歇尔航空中心已成为高级"地球至轨道"推进系统和技术方面的佼佼者. 1975年7月15日,马歇尔航空中心研发的Salum 1-B装载着美国和苏联首次合作的成果飞向了太空,此即Apollo-Soyuz计划.完成阿波罗项目后,马歇尔团队随即投入更有挑战性的工作中,设计一种代表革命性飞越的运载系统:航天飞机.     

The effects of maps and textual information on navigation in a desktop virtual environment

This study presents an experimentthat investigates how individuals perform anavigation test in a desktop virtualenvironment. The participants were randomlyassigned to one of the five test conditions:(C1) a map as information material during theentire test, (C2) the map only visible beforethe test, (C3) textual information during theentire test, (C4) textual information onlybefore the test and (C5) no additionalnavigational cues. The results were thatadditional information during the entire testwas more effective than short periods ofstudying the map or textual information onlybefore the test. However, participants weremore accurate in finding their route when anykind of navigational cues were used than whenno navigational cues were used. The results ofan additional questionnaire indicate thatbetween the test groups there were nodifferences in estimating the travelleddistances. The performance to draw the coveredpath into a sketch map of the landscape did notdiffer significantly between the test groupswith additional navigational cues. Theseresults indicate that in certain environmentstextual information may provide an effectivealternative to navigation training with a map.     

Extended Pile Driving Model to Predict the Penetration of the Insight/HP<Superscript>3</Superscript> Mole into the Martian Soil

The NASA InSight mission will provide an opportunity for soil investigations using the penetration data of the heat flow probe built by the German Aerospace Center DLR. The Heat flow and Physical Properties Probe (HP³) will penetrate 3 to 5 meter into the Martian subsurface to investigate the planetary heat flow. The measurement of the penetration rate during the insertion of the HP³ will be used to determine the physical properties of the soil at the landing site. For this purpose, numerical simulations of the penetration process were performed to get a better understanding of the soil properties influencing the penetration performance of HP³. A pile driving model has been developed considering all masses of the hammering mechanism of HP³. By cumulative application of individual stroke cycles it is now able to describe the penetration of the Mole into the Martian soil as a function of time, assuming that the soil parameters of the material through which it penetrates are known. We are using calibrated materials similar to those expected to be encountered by the InSight/HP³ Mole when it will be operated on the surface of Mars after the landing of the InSight spacecraft. We consider various possible scenarios, among them a more or less homogeneous material down to a depth of 3–5 m as well as a layered ground, consisting of layers with different soil parameters. Finally we describe some experimental tests performed with the latest prototype of the InSight Mole at DLR Bremen and compare the measured penetration performance in sand with our modeling results. Furthermore, results from a 3D DEM simulation are presented to get a better understanding of the soil response.     

Plant mineral nutrition,gas exchange and photosynthesis in space: A review

Successful growth and development of higher plants in space rely on adequate availability and uptake of water and nutrients, and efficient energy distribution through photosynthesis and gas exchange. In the present review, literature has been reviewed to assemble the relevant knowledge within space plant research for future planetary missions. Focus has been on fractional gravity, space radiation, magnetic fields and ultimately a combined effect of these factors on gas exchange, photosynthesis and transport of water and solutes.