Transient thermal performance of multilayer insulation systems during simulated ascent pressure decay

Transient thermal performance of multilayer insulation systems with liquid hydrogen tank during simulated Saturn 5 ascent pressure deca

Comparison of reusable insulation systems for cryogenically-tanked earth-based space vehicles

Three reusable insulation systems concepts were developed for use with cryogenic tanks of earth-based space vehicles. Two concepts utilized double-goldized Kapton (DGK) or double-aluminized Mylar (DAM) multilayer insulation (MLI), while the third utilized a hollow-glass-microsphere, loadbearing insulation (LBI). Thermal performance measurements were made under space-hold (vacuum) conditions for insulating warm boundary temperatures of approximately 291 K. The resulting effective thermal conductivity was approximately 0.00008 W/m-K (W = weight,Kg; m = measured; K = temperature) for the MLI systems (liquid hydrogen test results) and 0.00054 W/m-K for the LBI system (liquid nitrogen test results corrected to liquid hydrogen temperature)

EXPERIMENTAL INVESTIGATION OF THE SLOSH-DAMPING EFFECTIVENESS OF POSITIVE-EXPULSION BAGS AND DIAPHRAGMS IN SPHERICAL TANKS

Slosh damping effectiveness of positive expulsion bags and diaphragms in spherical tank

Experimental investigation of liquid sloshing in a scale-model Centaur liquid-hydrogen tank

Liquid sloshing in scale model Centaur liquid hydrogen tan

Program management model study

Two models, a system performance model and a program assessment model, have been developed to assist NASA management in the evaluation of development alternatives for the Earth Observations Program. Two computer models were developed and demonstrated on the Goddard Space Flight Center Computer Facility. Procedures have been outlined to guide the user of the models through specific evaluation processes, and the preparation of inputs describing earth observation needs and earth observation technology. These models are intended to assist NASA in increasing the effectiveness of the overall Earth Observation Program by providing a broader view of system and program development alternatives

Which Triggers Produce the Most Erosive, Frequent, and Longest Runout Turbidity Currents on Deltas?

Subaerial rivers and turbidity currents are the two most voluminous sediment transport processes on our planet, and it is important to understand how they are linked offshore from river mouths. Previously, it was thought that slope failures or direct plunging of river floodwater (hyperpycnal flow) dominated the triggering of turbidity currents on delta fronts. Here we reanalyze the most detailed time‐lapse monitoring yet of a submerged delta; comprising 93 surveys of the Squamish Delta in British Columbia, Canada. We show that most turbidity currents are triggered by settling of sediment from dilute surface river plumes, rather than landslides or hyperpycnal flows. Turbidity currents triggered by settling plumes occur frequently, run out as far as landslide‐triggered events, and cause the greatest changes to delta and lobe morphology. For the first time, we show that settling from surface plumes can dominate the triggering of hazardous submarine flows and offshore sediment fluxes

Oral language at school entry: dimensionality of speaking and listening skills

There has been a resurgence in concern about the levels of pupils’ oral language skills at school entry. To support and develop these skills effectively an understanding of the key components of oral language is required. We examined the oral language skills of monolingual children in Reception (MAge = 57.9 months; n = 126) and Year 1 (MAge = 69.07; n = 124) classes in England. Children were recruited from schools that were representative of London primary schools and were assessed on measures designed to tap phonology, core language skills (vocabulary and grammar) and discourse skills, both in the receptive and expressive modalities. Using confirmatory factor analyses, we examined the associations between oral language skills by component and modality for each age group. Oral language was best represented by four dimensions in Reception (receptive core language skills, receptive discourse, expressive core language skills, and expressive discourse). By contrast in Year 1, three dimensions were identified, irrespective of modality: phonology, core language skills and discourse. Our data speak to the importance of capturing these dimensions in assessments and teaching and monitoring their development at school entry. The results also highlighted the foundational role of discourse skills at the start of school

Purging of a multilayer insulation with dacron tuft spacer by gas diffusion

The time and purge gas usage required to purge a multilayer insulation (MLI) panel with gaseous helium by means of gas diffusion to obtain a condensable gas (nitrogen) concentration of less than 1 percent within the panel are stipulated. Two different, flat, rectangular MLI panels, one incorporating a butt joint, were constructed of of 11 double-aluminized Mylar (DAM) radiation shields separated by Dacron tuft spacers. The DAM/Dacron tuft concept is known commercially as Superfloc. The nitrogen gas concentration as a function of time within the MLI panel could be adequately predicted by using a simple, one dimensional gas diffusion model in which the boundary conditions at the edge of the MLI panel were time dependent. The time and purge gas usage required to achieve 1 percent nitrogen gas concentration within the MLI panel varied from 208 to 86 minutes and 34.1 to 56.5 MLI panel purge volumes, respectively, for gaseous helium purge rates from 10 to 40 MLI panel volumes per hour

Gamma-Ray Burst and Relativistic Shells: The Surface Filling Factor

The variability observed in many complex gamma-ray bursts (GRBs) is inconsistent with causally connected variations in a single, symmetric, relativistic shell interacting with the ambient material ("external shocks"). Rather, the symmetry of the shell must be broken on an angular scale much smaller than Gamma^{-1} where Gamma is the bulk Lorentz factor for the shell. The observed variability in the external shock models arises from the number of causally connected regions that (randomly) become active. We define the "surface filling factor" to be the ratio of the area of causally connected regions that become active to the observable area of the shell. From the observed variability in 52 BATSE bursts, we estimate the surface filling factor to be typically 0.005 although some values are near unity. We find that the surface filling factor is about 0.1 Delta T/T in both the constant Gamma phase (which probably produces the GRB) and the deaccelerating phase (which probably produces the x-ray afterglows). Here, \Delta T is a typical time scale of variability and T is the time since the initial signal. We analyze the 2 hr flare seen by ASCA 36 hr after the GRB and conclude that the surface filling factor must be small (0.001) in the x-ray afterglow phase as well. Explanations for low surface filling factor can either require more or less energy (by a factor of about 1000) compared to that expected for a symmetric shell.Comment: 26 pages, 5 embedded figures, Latex, revised version as in press, ApJ, added figure to show the possible expanding shell geometries that can give low filling facto

Experimental Investigation of Optimized Cold-formed Steel Compression Members

In the past, standard C - shaped metal studs have been the only option for designers and contractors when selecting a cross section for load bearing compression members. T he sigma shaped section has recently emerged as an alternative to the C - section. The sigma shaped section is very similar to the C - shape, with the exception of having an intermediate web return and complex stiffeners. The experimental results of concentric axial compression tests of fifty - eight sigma shaped members are reported. Specimen s were tested at various lengths to force global, distortional, and local buckling failure modes. Additionally, the test program contained members with and without web holes. Comparisons of experimental results with the American Iron and Steel Institute ( AISI) design methods, Effective Width Method (EWM) and Direct Strength Method (DSM), are discussed