New Methods of Manufacturing Space Suits for Deep Space Exploration

The Extravehicular Activity (EVA) spacesuit is a complex machine that provides astronauts with a flexible enclosure and life support system allowing them to perform EVAs in space or on planetary surfaces. As humans continue to explore the Solar System, the ability for space fairing organizations to become Earth-autonomous is a necessity, and the need for an Earth-independent spacesuit is unavoidable. With the evolution of additive manufacturing technologies, it may be possible to produce 3D-printed soft goods that can replace the labor-intensive bladders and restraint layers currently in pressure suits. The Human Spaceflight Laboratory (HSFL) at the University of North Dakota has demonstrated the ability to use additive manufacturing to develop various soft spacesuit components. By utilizing flexible filaments in combination with interwoven mesh fabrics for improved durability, the HSFL has been able to produce various soft goods components, a functional elbow mobility joint and a boot/ankle assembly. The components have been successfully tested at nominal spacesuit pressures along with burst tests at higher pressures. Through development and testing of these early prototypes, the HSFL has proved that additive manufacturing can be utilized to fabricate spacesuit elements. The HSFL plans to build upon the advancements discussed in this paper and continue to employ additive manufacturing techniques with the end goal of developing a fully functional 3D-printed pressure garment based on our existing NDX-1 planetary suit architecture

Latent solitons, black strings, black branes, and equations of state in Kaluza-Klein models

In Kaluza-Klein models with an arbitrary number of toroidal internal spaces, we investigate soliton solutions which describe the gravitational field of a massive compact object. We single out the physically interesting solution corresponding to a point-like mass. For the general solution we obtain equations of state in the external and internal spaces. These equations demonstrate that the point-like mass soliton has dust-like equations of state in all spaces. We also obtain the PPN parameters, which give the possibility to obtain the formulas for perihelion shift, deflection of light and time delay of radar echoes. Additionally, the gravitational experiments lead to a strong restriction on the parameter of the model: $\tau = -(2.1\pm 2.3)\times 10^{-5}$. The point-like mass solution contradicts this restriction. The condition $\tau=0$ satisfies the experimental limitation and defines a new class of solutions which are indistinguishable from general relativity. We call such solutions latent solitons. Black strings and black branes belong to this class. Moreover, the condition of stability of the internal spaces singles out black strings/branes from the latent solitons and leads uniquely to the black string/brane equations of state $p_i=-\epsilon/2$, in the internal spaces and to the number of the external dimensions $d_0=3$. The investigation of multidimensional static spherically symmetric perfect fluid with dust-like equation of state in the external space confirms the above results.Comment: 8 pages, Revtex4, no figures, minor changes adde

Kaluza-Klein models: can we construct a viable example?

In Kaluza-Klein models, we investigate soliton solutions of Einstein equation. We obtain the formulas for perihelion shift, deflection of light, time delay of radar echoes and PPN parameters. We find that the solitonic parameter k should be very big: |k|\geq 2.3\times10^4. We define a soliton solution which corresponds to a point-like mass source. In this case the soliton parameter k=2, which is clearly contrary to this restriction. Similar problem with the observations takes place for static spherically symmetric perfect fluid with the dust-like equation of state in all dimensions. The common for both of these models is the same equations of state in our three dimensions and in the extra dimensions. All dimensions are treated at equal footing. To be in agreement with observations, it is necessary to break the symmetry between the external/our and internal spaces. It takes place for black strings which are particular examples of solitons with k\to \infty. For such k, black strings are in concordance with the observations. Moreover, we show that they are the only solitons which are at the same level of agreement with the observations as in general relativity. Black strings can be treated as perfect fluid with dust-like equation of state p_0=0 in the external/our space and very specific equation of state p_1=-(1/2)\epsilon in the internal space. The latter equation is due to negative tension in the extra dimension. We also demonstrate that dimension 3 for the external space is a special one. Only in this case we get the latter equation of state. We show that the black string equations of state satisfy the necessary condition of the internal space stabilization. Therefore, black strings are good candidates for a viable model of astrophysical objects (e.g., Sun) if we can provide a satisfactory explanation of negative tension for particles constituting these objects.Comment: 11 pages, Revtex4, no figures, appendix and references adde

Lorentz violation and the speed of gravitational waves in brane-worlds

Lorentz violation in a brane-world scenario is presented and used to obtain a relationship between the speed of gravitational waves in the bulk and that on the brane. Lorentz violating effects would manifest themselves in gravitational waves travelling with a greater speed in the bulk than on the brane and this effect is independent of the signature of the extra dimension.Comment: 8 pages, to appear in PL

Static wormholes on the brane inspired by Kaluza-Klein gravity

We use static solutions of 5-dimensional Kaluza-Klein gravity to generate several classes of static, spherically symmetric spacetimes which are analytic solutions to the equation $^{(4)}R = 0$, where $^{(4)}R$ is the four-dimensional Ricci scalar. In the Randall & Sundrum scenario they can be interpreted as vacuum solutions on the brane. The solutions contain the Schwarzschild black hole, and generate new families of traversable Lorenzian wormholes as well as nakedly singular spacetimes. They generalize a number of previously known solutions in the literature, e.g., the temporal and spatial Schwarzschild solutions of braneworld theory as well as the class of self-dual Lorenzian wormholes. A major departure of our solutions from Lorenzian wormholes {\it a la} Morris and Thorne is that, for certain values of the parameters of the solutions, they contain three spherical surfaces (instead of one) which are extremal and have finite area. Two of them have the same size, meet the "flare-out" requirements, and show the typical violation of the energy conditions that characterizes a wormhole throat. The other extremal sphere is "flaring-in" in the sense that its sectional area is a local maximum and the weak, null and dominant energy conditions are satisfied in its neighborhood. After bouncing back at this second surface a traveler crosses into another space which is the double of the one she/he started in. Another interesting feature is that the size of the throat can be less than the Schwarzschild radius $2 M$, which no longer defines the horizon, i.e., to a distant observer a particle or light falling down crosses the Schwarzschild radius in a finite time

Dynamics of Quintessence Models of Dark Energy with Exponential Coupling to the Dark Matter

We explore quintessence models of dark energy which exhibit non-minimal coupling between the dark matter and the dark energy components of the cosmic fluid. The kind of coupling chosen is inspired in scalar-tensor theories of gravity. We impose a suitable dynamics of the expansion allowing to derive exact Friedmann-Robertson-Walker solutions once the coupling function is given as input. Self-interaction potentials of single and double exponential types emerge as result of our choice of the coupling function. The stability and existence of the solutions is discussed in some detail. Although, in general, models with appropriated interaction between the components of the cosmic mixture are useful to handle the coincidence problem, in the present study the coincidence can not be evaded due to the choice of the solution generating ansatz.Comment: 10 pages, 7 figure

Increasing Access to Food: A Comprehensive Report on Food Supply Options

Access to food is one of the most important aspects of a healthy, sustainable community. Grocery stores and other suppliers can serve as an economic anchor to provide social benefits to communities. Unfortunately, many communities do not have convenient and/or affordable access to grocery items, particularly fresh produce. As part of Virginia Commonwealth University\u27s Fall 2019 graduate course on Urban Commercial Revitalization, class members researched 13 retail and other food access options, which are described in this report. Each chapter covers a food access option and provides basic information that will be useful to individuals, organizations, or government agencies that wish to attract and/or develop grocery operations in their communities

Design development of a repeatable helmet test system for public order threat recreations

The prevalence of violence and blunt weaponry that Public Order (PO) officers are exposed to, place them at high risk of traumatic brain injury (TBI). Recreating these injurious occurrences, to assess protective equipment performance, can be problematic due to issues of repeatability when experimentally recreating PO threats. This led to the design of a bespoke helmet impact system. Following review of current test methods, the chosen design was a low-friction drop tower, compatible with anthropometric headforms as cradled, rigidly mounted, or affixed with a surrogate neck. Finite Element and torque calculations were used to optimise load bearing components, whilst maintaining low mass and safety requirements. The final system permits impact conditions in range for PO threat recreations, as well as meeting the standard test criteria of all non-vehicular sports, public sector and construction application standard drop tests

Fierz-Pauli equation for massive gravitons from Induced Matter theory of gravity

Starting with a 5D physical vacuum described by a 5D Ricci-flat background metric, we study the emergence of gravitational waves (GW) from the Induce Matter (IM) theory of gravity. We obtain the equation of motion for GW on an 4D curved spacetime which has the form of a Fierz-Pauli one. In our model the mass of gravitons $m_g$ is induced by a static foliation on the noncompact space-like extra dimension and the source-term is originated in the interaction of the GW with the induced connections of the background 5D metric. Here, relies the main difference of this formalism with the original Fierz-Pauli one.Comment: 9 pages, no figures, version accepted in Phys. Lett.