Hard Vacuum Research Articles

Indonesia Space Program : Future Soft Power

This paper discusses Indonesia's space / aerospace industry program as the nation's future Soft Power. The term 'soft power', coined by Joseph S. Nye of Harvard University in the United States, is the ability of a country to influence another country not through coercive means but through attractiveness or reputation. This research uses a literature research approach, which is a method by collecting data by understanding and studying theories from various literature related to research There are four stages of literature study in research. Space, or simply space, is the expanse that exists beyond the Earth and between celestial bodies. Space isn't completely empty it's a hard vacuum containing low particle densities, especially hydrogen and helium plasma, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays. Recent developments show that in the future, not only professional astronauts can go into space but also all citizens of the world can afford to pay.

The war in Ukraine, the EU’s geopolitical awakening and implications for the “contested neighbourhood”

ABSTRACT This article looks at how the Russian invasion has reshaped the EU's Eastern neighbourhood policy and subsequently how has the new policy affected the strategies of the Eastern Partnership (EaP) countries. We systematically review policy responses to the war of the EU and the countries of the EU-Russia contested neighbourhood and identify new patterns in foreign policy behavior of these states and key domestic policy changes. We specifically highlight the shift in two key attributes of the EU's foreign policy, which has traditionally defined its neighbourhood policy: its relations with Russia and the inclusiveness of the EaP countries in the European project. We make two arguments: first, the crisis and new risks in the region has created a demand and opened a geopolitical dimension to the EU neighbourhood policy, which required Brussels to fill a hard security vacuum in its own policies in the neighbourhood, which invoked an application of new instruments to deter Moscow and support EU's Eastern allies. Second, the crisis contributes to even faster erosion of the post-Soviet space and a new regional fragmentation along geopolitical lines. Finally, the question of sustainability of these changes and their effect on the EU as an actor remains open.

Size and charge distribution characteristics of fine and ultrafine particles in simulated lunar dust: Relevance to lunar missions and exploration

Astronaut anecdotal data, biologic studies, and multi-perspective reports indicate that lunar dust will be a significant hindrance to exploring the Moon, both robotically and by humans. Hence, important characteristics of the lunar dust must be established. Critically needed are detailed particulate matter size, dust cloud concentration, and charge distribution analyses to determine the viability of methods for real-time measurement on the lunar surface. In this study, we applied various state-of-the-art aerosol measurement techniques to characterize fine (0.1–2.5 ​μm) and ultrafine (<0.1 ​μm) JSC-1A lunar simulant particles. The different techniques were assessed at 1 ​atm and evaluated for viability on the lunar surface (i.e., hard vacuum). To represent suspended dust, the simulant was dispersed as an aerosol and size distributions were measured in real-time using multiple aerosol instruments. Results show a unimodal distribution centered at approximately 0.2 ​μm, in fair agreement with previously reported measurements. To demonstrate portability and networkability, two low-cost particulate matter sensors were evaluated for measurement of suspended dust concentration. Strong correlations with an industry standard instrument support the potential candidacy of these sensors for future in-situ measurements on the Moon. Evaluating the capability of compact, low-cost instruments and larger, more robust instruments to precisely and accurately measure particle size distributions is a critical step to determine the prospect of measuring particulate matter with lightweight sensors in multiple lunar environments. In addition, assessing the compact instrument mass, power, portability, complexity, and measurement speed will provide key guidance into mitigating dust-related challenges to future lunar missions.

A Scalable Solution Route to Porous Networks of Nanostructured Black Tungsten

This paper studied the feasibility of a new solution-processed method to manufacture black tungsten nanostructures by laser conversion of tungsten hexacarbonyl precursor on the Inconel 625 substrate under argon atmosphere at ambient pressure. The results show that sublimation of the precursor can be prevented if the decomposition temperature (>170 °C) is achieved using the laser heating method. Three different laser powers from 60–400 W were used to investigate the role of laser parameters on the conversion. It was found that lower laser power of 60 W resulted in a mixture of unconverted precursor and converted tungsten. Higher laser powers >200 W resulted in α-W (BCC) in one step without further heat treatment. Different oxygen concentrations from 0.5 ppm to 21 vol% were used in the laser canister to investigate the effect of oxygen concentration on the conversion. It was found that the hard vacuum (>10−4 torr) or hydrogen is not necessary to obtain α-W (BCC). The solar absorptance varied from 63–97%, depending on the amount of precursor deposited on the substrate and oxygen content in the laser canister. This solution-based laser conversion of tungsten precursor is a scalable method to manufacture tungsten coatings for high-temperature applications.

Radiation-induced transformations of difluoromethane in noble gas matrices

Difluoromethane (CH2F2) is considered as an ecologically friendly alternative to conventionally used chlorofluorocarbons for various applications. Being photochemically inert in the broad UV range, this molecule can be decomposed only through the action of hard vacuum UV or ionizing radiation, while the corresponding mechanisms are poorly studied. In this work we report the results of model investigations of the X-ray induced decomposition of isolated CH2F2 in solid noble gas matrices at 6 K. The radiation-chemical yields of difluoromethane were found to decrease from 1.3 to 0.1 molecule/100 eV with decreasing the ionization energy of matrix (from Ne to Xe), which indicates significance of the “hot” ionic channels. Difluorocarbene (CF2) was detected as one of the principal radiolysis products in all the matrices, whereas the CHF⋯HF complex was detected in Ne, Ar, and Kr. Annealing of the irradiated samples results in thermally induced reactions of trapped H and F atoms yielding a number of various species, including the noble gas compounds. The radiolysis mechanism, nature of matrix effects and possible implications for atmospheric chemistry are discussed.

Fabrication of an efficient structured packing for hard vacuum distillation processes and calibration by Carbon tetrachloride-Benzene mixture

In vacuum distillation processes, pressure drop per unit of theoretical plate (Δp) is an important parameter because overall pressure drop of distillation column must be lower than one atmosphere (0<ΔP<1 atm.). Besides, in hard distillation processes having small relative volatility coefficient (1<αi<1.1), minimum number of theoretical plates per unit length (nmin) is another important parameter as total height of distillation column cannot exceed the maximum of technologically attainable height. Moreover, by increasing total height of the column its thermal control will be extremely hard. In this work, an efficient structured packing for hard vacuum distillation processes has been fabricated and also calibrated using the binary mixture of Carbon tetrachloride-Benzene, with very low relative volatility coefficient (1.128<αi<1.142). In hard vacuum distillation processes both parameters, Δp and nmin, are important. Therefore, the effects of three main variables including reflux volumetric flow rate, the number of distributors within the packed-bed and average height of each element of the structured packing on these parameters have been studied. The best amounts of Δp and nmin found to be 1.394 mmHg/tray and 14.2175 tray/m respectively. This vividly indicates that the newly introduced structured packing is appropriate for hard vacuum distillation processes.

Effect of blending protocol on the performance of SBS/sulfur/soybean-derived additive composite modified hard asphalt

ABSTRACT This paper explores the feasibility of using SBS/sulfur/soybean-additive in combination in a hard asphalt binder to produce a composite modified asphalt binder. The modification effects of the additives and the influence of different blending protocols were comprehensively studied through laboratory investigations. The rheology of the asphalt binders was evaluated via viscosity, bitumen grading, master curve, Black diagram, isochronal plot, Han diagram, fatigue, creep stiffness and m-value using a bending beam rheometer (BBR), and Multiple Stress Recovery (MSCR) test using a Dynamic Shear Rheometer (DSR). The modified binder’s susceptibility to aging effects and thermal stability were also determined by calculation of the aging index (AI) and degree of separation. The results showed that the additives were able to enhance the overall performance of the hard neat Vacuum Tower Bottoms (VTBs) binder by increasing its resistance to rutting, fatigue cracking, and thermal cracking. It was also found that the additives reduced the aging susceptibility of the VTBs binder without any thermal stability or degradation issues after aging conditions. According to the overall performance of the modified binders, a blending protocol for producing a composite modified binder with optimal performance achieved through a well–developed cross-linked polymer elastic network was recommended.

Decreasing of Profile Air Drag to the Train Movement Inside the Tube Transport

Background: The movement of the train in an insulated space with the natural atmospheric pressure is accompanied by energy losses for unproductive work to overcome the profile air drag from the front and rear surfaces of the vehicle. At the same time, there is also a considerable increase of energy costs for overcoming the growing force of oncoming air drag. In order to exclude these energy losses, it is proposed to organize synchronous and volume-balanced pumping of air from the front part of the tube transport and injection of the air into the back part of the tube transport.&#x0D; Aim: To develop a method of organising air exchange inside the tube transport, which will ensure the reduction of air resistance to the movement of the train.&#x0D; Methods: The proposed developments are based on well-known national and foreign designs of high-speed tube transport systems, the results of a comparative analysis of tube transport with varying degrees of air pumping (backing vacuum and hard vacuum), taking into account the experience of redistributing the residual air volume in the Hyperloop and TransPod tube transport systems. The operating parameters of the compressor units that pump air into the internal cavity of the tube when the train is in motion is regulated on the basis of process models of gas dynamics.&#x0D; Results: A new method and device has been developed for reducing the air drag to the movement of the train by forced air exchange, which provides for the redistribution of air from the front to the rear of the transport tube relative to the vehicle travel direction. For the air redistribution, the external air exchange unit, consisting of air ducts, compressor units, gate valves, and air collectors is used. The process of external air exchange takes place only when the vehicle is in motion, for the movement of the vehicle no prior air exhaust is required. The air redistribution is controlled taking into account the speed of the train, its location in the tube, the design features of the tunnel and vehicle. The speed of the train for each segment of the speed section is normalised depending on the actual performance of the components of the air exchange system. Modes of operation of the compressor units must ensure synchronous redistribution of air from the front to the rear of the tube. The movement of a vehicle along a tube with normal atmospheric pressure in the internal cavity provides conditions for the safe transportation of goods and passengers.&#x0D; Conclusion: The developed method is designed to reduce the force of air resistance when the train is in motion inside the airtight tube without creating vacuum. The presented developments have good prospects for use in projects of high-speed transport systems of both underground and underwater designs.

Significant depletion of volatile elements in the mantle of asteroid Vesta due to core formation

Vesta, the second-largest body in the asteroid belt, is believed to be a prime example of a rocky protoplanet. Studies of the HED (Howardite–Eucrite–Diogenite) meteorite suite, considered to be sourced from the mantle of Vesta, provide insight into protoplanet differentiation processes. Eucrites and diogenites are depleted in many volatile elements, but the depletions of many volatile siderophile elements are not well constrained. Although previous work indicated that the Vestan core equilibrated with its mantle in a global melting event, the possible contribution of core formation to the volatile budget of HED meteorites has not been assessed to date. This prohibits an assessment of the overall volatile depletion systematics of Vesta.Here, we use a compilation of published volatile siderophile element (VSE; C, S, Zn, As, Se, Cd, In, Sb, Te, Tl, Pb, Bi) abundances in diogenites and eucrites to constrain their depletions in the Vestan mantle. We assess to what extent these depletions may be volatility-related, caused by partitioning into sulfides in the mantle, and/or a result of their preferential partitioning into the Vestan core during core-mantle equilibration. Our new estimates for VSE depletions in the Vestan mantle show no correlation with condensation temperature, suggesting the depletions are difficult to reconcile with partial condensation or degassing during accretionary processes only. Sulfide saturation of the diogenite and eucrite source region is also unlikely because of low indigenous S abundances in these samples compared to calculated S contents at sulfide saturation. Consideration of the metal-silicate partitioning behaviour of the VSE shows that most of these elements are sufficiently siderophile to explain a significant part of their observed depletions in the Vestan mantle by their preferential partitioning into a S-rich core.Moderately volatile elements As and Sb both appear more abundant in the Vestan mantle than expected from their highly siderophile behaviour in systems with basaltic melts. These apparent overabundances may be related to strong silicate melt compositional effects on their metal-silicate partitioning behaviour. On the other hand, Zn, and to a lesser extent Te and Tl are significantly more depleted than expected from metal-silicate partitioning alone. This could be evidence for volatile loss of these elements from Vesta through kinetic loss in a hard vacuum. Alternatively, the perceived loss of Zn may be the result of a Zn-poor Vestan bulk composition and/or partly by preferential partitioning of Zn into spinel. The additional depletion of Tl and by extension other highly chalcophile elements such as Se and Te may be explained by segregation of sulfides in the eucritic melt source region(s), if significant amounts of S degassed from eucritic melts after sulfide segregation.Our results underline the feasibility of planetary cores being a major reservoir for many volatile elements that are depleted in planetary mantles, and that are currently assumed to have suffered incomplete condensation during accretion or (partial) degassing after accretion.

Photoemission study of the electronic structure of the Kondo latticesYb2Pt6X15(X=Al, Ga)

The electronic structure of Yb-based Kondo lattices ${\mathrm{Yb}}_{2}{\mathrm{Pt}}_{6}{X}_{15}$ ($X$=Al, Ga) has been investigated by means of photoemission spectroscopy using hard x-ray ($h\ensuremath{\nu}=5.95$ keV) and vacuum ultraviolet ($h\ensuremath{\nu}=182$ eV) synchrotron radiation. The Yb $3d$ spectra of ${\mathrm{Yb}}_{2}{\mathrm{Pt}}_{6}{X}_{15}$ showed both ${\mathrm{Yb}}^{2+}$- and ${\mathrm{Yb}}^{3+}$-derived structures, directly indicating valence fluctuation. The Yb valences of ${\mathrm{Yb}}_{2}{\mathrm{Pt}}_{6}{\mathrm{Al}}_{15}$ were estimated to be $2.89\ifmmode\pm\else\textpm\fi{}0.01$ at 250 K and $\ensuremath{\sim}2.83$ at 20 K, while those of ${\mathrm{Yb}}_{2}{\mathrm{Pt}}_{6}{\mathrm{Ga}}_{15}$ were $\ensuremath{\sim}2.34$ at 300 K with almost no temperature dependence. With changing $X$ ions from Al to Ga, the Pt $5d$ and Pt $4f$ peaks were shifted to shallower binding energies, and the ${\mathrm{Yb}}^{3+}$ $4f$ peaks were shifted to the deeper binding energies. The $X$ dependences of the Yb valence and the Kondo temperature of ${\mathrm{Yb}}_{2}{\mathrm{Pt}}_{6}{X}_{15}$ are discussed based on the ${\mathrm{Yb}}^{3+}$ $4f$ hole level relative to the Fermi level ${E}_{F}$ and Pt-derived density of states at ${E}_{F}$.

Lunar regolith can allow the synthesis of cement materials with near-zero water consumption

With the continuous development of science and technology and the human understanding of the moon, many scientists have planned the creation of a space station on the moon using lunar building materials. Environmental factors mainly include large temperature differentials, and the presence of a hard vacuum on the surface of the moon is a huge challenge for the performance of lunar building materials. Geopolymer materials have the following properties: approximately zero water consumption, resistance to high- and low-temperature cycling, vacuum stability and good mechanical properties. Additionally, they meet most of the requirements for use in the lunar environment. Here, we present a potential lunar cement material that was fabricated using volcanic ash and sodium hydroxide solution as activator, based on geopolymer technology. The compressive strengths of the volcanic ash geopolymer specimens processed for 24h under vacuum conditions and 30 freeze-thaw cycles in liquid nitrogen are 45.53 and 44.95MPa, respectively. Additionally, 98.61% of water could be recycled, in consistence with the water recycling-simulated lunar environment in the lab. Although volcanic ash is not equivalent to the lunar soil, we speculate that the alkali activation of lunar soil could be very close to that of volcanic ash because of their similar chemical and mineralogical composition. In summary, this study provides a feasible approach for the development of near-zero water consumption lunar cement materials based on geopolymer technology.

XAFS beam lines at Aichi Synchrotron Radiation Center dedicated to industrial use

Aichi Synchrotron Radiation Center was designed for industrial use following five years of discussion among academia, industry and local government in the Aichi area. Among the six beam lines constructed, those that facilitated X-ray absorption fine structure (XAFS) analysis were given first priority. In addition to the hardware, attention was given to the development of operating procedures that were quick and user-friendly. The facility entered public service in March 2013. In the year 2013, 55% of the experiments involved XAFS analysis (hard X-ray, soft X-ray and vacuum ultraviolet regions) and in 2014 it was 57%. The range of research fields is very broad, emphasizing the importance of the XAFS beam lines.

A Model-Based Approach to the Protection of the Steering Mechanism of High-Power Antennas Placed in a Nuclear Fusion Tokamak

In most applications where motors control several degrees of freedom of a mechanical system, there is the necessity to implement protection that is able to stop the motors when the mechanical system reaches the extreme positions of its workspace. When the mechanical system is located in a hostile environment and/or when the limit positions define a complex surface, the protection strategy cannot be always implemented by simply placing sensors and limit switches in the proximity of the limit positions. We present in this paper a solution for the protection problem, which employs a model-based algorithm capable of estimating in real time the system state variables. The idea of the model-based protection scheme is to implement a model of the mechanical system forced by the emergency braking actions in order to predict, using the current estimated state of the system as initial condition, the trajectory of relevant system outputs, together with their uncertainties, during the braking transient. If the probability that the predicted output trajectories intercept the physical boundaries of the workspace exceeds a predefined threshold, the protection trips. With this approach, we aim to reach a greater exploitation of the system workspace than with a fixed-threshold algorithm, since in this case, the threshold is adapted to the current system state. In this paper, the aforementioned algorithm is developed for a particular application, namely, the protection of a set of steering microwave antennas placed in a hostile environment (hard vacuum condition, strong neutron and gamma radiation, and strong magnetic fields) inside a nuclear-fusion reactor. However, it is the opinion of the authors that the same procedure could also find good application in other systems that need protection with similar characteristics. Some simulations and preliminary test results will be also presented in order to better clarify how the protection works, and finally, some implementation issues will be discussed.

Active dust control and mitigation technology for lunar and Martian exploration

Mars is covered with a layer of dust that has been homogenized by global dust storms. Dust, levitated by these storms as well as by the frequent dust devils, is the dominant weather phenomenon on Mars. NASA's Mars exploration rovers have shown that atmospheric dust falling on solar panels can decrease their efficiency to the point of rendering the rover unusable. Dust covering the surface of the moon is expected to be electrostatically charged due to the solar wind, cosmic rays, and the solar radiation itself through the photoelectric effect. Electrostatically charged dust has a large tendency to adhere to surfaces. The Apollo missions to the moon showed that lunar dust adhesion can hinder manned and unmanned exploration activities. In this paper, we report on our efforts to develop an electrodynamic dust shield to prevent the accumulation of dust on surfaces and to remove dust already adhering to those surfaces. The technology uses electrostatic and dielectrophoretic forces to carry dust particles off surfaces and to generate an electrodynamic shield that prevents further accumulation of dust. The concept of the electrodynamic dust shield was introduced by NASA in the late 1960s and later reduced to practice during the 1970s for terrestrial applications. In 2003, our laboratory, in collaboration with several universities, applied this technology to space applications, specifically to remove dust from solar panels on Mars. We show how, with an appropriate design, we can prevent the electrostatic breakdown at the low Martian atmospheric pressures. We are also able to show that uncharged dust can be lifted and removed from surfaces under simulated Martian environmental conditions. We have also been able to develop a version of the electrodynamic dust shield working under hard vacuum conditions that simulate the lunar environment. We have implemented the electrodynamic dust shield on solar arrays, optical systems, spectrometers, viewports, thermal radiators, batteries, and power systems, as well as on fabrics for spacesuits. We present data on the design and optimization of the electrodynamic dust shields and provide data on the performance of the different implementations of the technology for lunar and Martian exploration activities.

Numerical assessment of plume heat and mechanical loads and contamination on multi-layer insulation in hard vacuum

The paper presents a numerical analysis of plume exhausted from the 10N bipropellant thruster. The computations have been performed for steady state and pulse mode firing of the thruster. The plume impinges a multi-layer insulation (MLI) that covers a satellite surface, where plume effects have been computed for ideal and bulged shapes of the MLI. The ideal shape is a circular cylinder surface, where the bulge is a deflection of the MLI due to satellite spin. Plume effects, pressure and heat flux, are almost doubled for the bulged MLI. An engineering model based on experimental data has been applied. It was shown that it is conservative against the numerical modeling in the plume backflow. An application of the pulse mode leads to a formation of droplets. One of the sources of the droplets is a rupture of liquid film at the nozzle lip. A parametric study with different droplet sizes and initial velocities has been performed for thrusters firing along and against the satellite spin. The thruster that fires against the satellite spin contaminates the MLI more than the other thruster. Droplets with an initial velocity smaller than 6m/s cannot contaminate the MLI.

Transfer of Electricity in Energy Engineering

This paper aims to suggest and research a revolutionary method-transfer of electricity in outer Space with distance of hundreds of millions kilometers by ultra-cool plasma cables. Theory of plasma cable transferring is offered, developed and its possibilities researched. Offers conclusions from the research of a revolutionary new idea-transferring electric energy in the hard vacuum of outer space wirelessly, using a plasma power cord as an electric cable (wire).Transference of hundreds kilowatts of energy to Earth’s Space Station, transferring energy to the Moon or back, transferring energy to a spaceship at distance 100 million of kilometers, the transfer energy to Mars when one is located at opposite side of the distant Sun, transfer colossal energy from one of Earth’s continents to another continent wirelessly – using Earth’s ionosphere as cable, using Earth as gigantic storage of electric energy, using the plasma ring as huge MagSail for moving of spaceships.

Controlled particle removal from surfaces by electrodynamic methods for terrestrial, lunar, and Martian environmental conditions

An Electrodynamic Dust Shield to remove already deposited micron-size particles from surfaces and to prevent the accumulation of such particles on surfaces has been developed. In addition to terrestrial application, our NASA laboratory is adapting this technology for the dusty and harsh environments of the Moon and Mars. The Apollo missions to the moon showed that lunar dust can hamper astronaut surface activities due to its ability to cling to most surfaces. NASA's Mars exploration landers and rovers have also shown that the problem is equally hard if not harder on Mars. In this paper, we show that an appropriate design can prevent the electrostatic breakdown at the low Martian atmospheric pressures. We are also able to show that uncharged dust can be lifted and removed from surfaces under simulated Martian environmental conditions. This technology has many potential benefits for removing dust from visors, viewports and many other surfaces as well as from solar arrays. We have also been able to develop a version of the electrodynamic dust shield working under hard vacuum conditions. This version should work well on the moon. We present data on the design and optimization of both types of dust shields as well substantial data on the clearing factors for transparent dust shields designed to protect solar panels for Martian exploration.

Transfer of electricity in space

PurposeThis paper aims to suggest and research a revolutionary method‐transfer of electricity in outer Space with distance of hundreds of millions kilometers by ultra‐cool plasma cables.Design/methodology/approachMethods of the plasma and electricity physic are used for research.FindingsTheory of plasma cable transferring is offered, developed and its possibilities researched.Research limitations/implicationsThis method uses a high voltage electricity and plasma source (accelerator).Practical implicationsOffers conclusions from the research of a revolutionary new idea‐transferring electric energy in the hard vacuum of outer space wirelessly, using a plasma power cord as an electric cable (wire). He computed the macroprojects: transference of hundreds kilowatts of energy to Earth's Space Station, transferring energy to the Moon or back, transferring energy to a spaceship at distance 100 million of kilometers, the transfer energy to Mars when one is located at opposite side of the distant Sun, transfer colossal energy from one of Earth's continents to another continent (for example, between Europe – USA) wirelessly – using Earth's ionosphere as cable, using Earth as gigantic storage of electric energy, using the plasma ring as huge MagSail for moving of spaceships.Originality/valueThe paper provides information on a revolutionary method for the transfer of electricity in outer space.

On the nature of man and disaster

Unique among animals, humans survive not by superb physical adaptation to our environment, but rather by intelligent, large-scale adaptation of the environment to our needs. We build houses with climate control systems that mimic the environment of sub-Saharan Africa. We safely live in environments where the temperature never rises above freezing and where the level of the sea is higher than the land we farm and build vast cities upon. We live in tropical rainforests teeming with hostile organisms, and atop arid, life-poor mountains and plains, at elevations in excess of 5000 m. As this editorial is written, a few of us live in space, circling the earth in an environment of hard vacuum, searing heat, and cryogenic cold. The sole endowment for our survival that evolution has bestowed upon us is reason and technologic civilization, which is its product. All human habitations, and all life on earth for that matter, are under continuous threat of some kind. Violent weather, earthquakes, volcanic eruptions, and even meteorite impacts represent threats of varying degrees of risk.

The interactions between fatigue, creep and environmental damage in Ti 6246 and Udimet 720Li

The paper reports the results of a comprehensive research programme on two different compressor disc alloys: titanium alloy Ti 6246 and the nickel based superalloy Udimet 720Li. Both alloys are used for disc applications in gas turbine engines under conditions where the rims are exposed to fatigue, creep and environmental damage. The titanium alloy was investigated at temperatures of 80, 450, 500 and 550 °C, whilst the nickel at 650 and 700 °C. The paper presents the strain-life response of plain specimens and relates these data to notch fatigue behaviour. It also explores fatigue crack propagation behaviour in air and under hard vacuum (10 −6 Torr), in order to characterise the creep/environment/fatigue interactions that occur at the crack tip. The growth data encompass R values of −3 to 0.5 for cyclic and dwell waveforms. The information obtained allows the effects of environment and creep at these temperatures to be partitioned. The observed R value dependence is related to both empirical models and closure measurements. The experimental data are supported by detailed metallographic and fractographic studies using optical and SEM techniques.