Strutjet Matures to Support Propulsion Needs in the 2000+ World

The Strutjet, Aerojet's Rocket Based Combined Cycle (RBCC) concept, was discussed in a previous ISABE paper as an enabling propulsion concept for single stage to orbit applications. This paper describes the technical progress of the Strutjet since 1996 together with a rationale why RBCC engines in general and the Strutjet in particular, lend themselves uniquely to systems having the ability to expand current space and also open new global "rapid delivery" markets. In particular, the paper substantiates the claims why for certain missions RBCC powered vehicles can be operated at higher margins than all rocket systems, and why within the family of conceivable RBCC systems the Strutjet excels due to its unique architecture and design features. A special emphasis is given to the selection of the engine's ram/scram mode design point because only that mode can add significantly to the mission effective Isp. The thrust produced by an airbreathing engine is directly related to the mass of air processed. This air is captured by the inlet and compressed to raise the pressure for combustion and subsequent expansion. The net accelerating force is the difference between the gross thrust and total vehicle drag (including the spill drag). This total drag is highest at low speeds when the gross thrust is lowest. When the net accelerating force is low, most of the fuel burned is wasted overcoming the vehicle drag. Higher thrust is necessary to perform the mission. One method is to leave the rockets on longer but this results in much higher propellant consumption

Recent Changes in the Law Affecting Educational Hearing Procedures for Handicapped Children

This article is a revised version of a report originally prepared for the Maryland State Bar Association, Special Committee on Law and the Handicapped by members of the Education Sub-committee. The article reviews and analyzes recent changes in the law affecting procedures for diagnosis, evaluation, and educational placement of handicapped children. The article reflects the views of the authors, and does not necessarily reflect the position of the Maryland State Bar Association

Environmental effects on progesterone profile measures of dairy cow fertility

Environmental effects on fertility measures early in lactation, such as the interval from calving to first luteal activity (CLA), proportion of samples with luteal activity during the first 60 days after calving (PLA) and interval to first ovulatory oestrus (OOE) were studied. In addition, traditional measurements of fertility, such as pregnancy to first insemination, number of inseminations per service period and interval from first to last insemination were studied as well as associations between the early and late measurements. Data were collected from an experimental herd during 15 years and included 1106 post-partum periods from 191 Swedish Holsteins and 325 Swedish Red and White dairy cows. Individual milk progesterone samples were taken twice a week until cyclicity and thereafter less frequently. First parity cows had 14.8 and 18.1 days longer CLA (LS-means difference) than second parity cows and older cows, respectively. Moreover, CLA was 10.5 days longer for cows that calved during the winter season compared with the summer season and 7.5 days longer for cows in tie-stalls than cows in loose-housing system. Cows treated for mastitis and lameness had 8.4 and 18.0 days longer CLA, respectively, compared with healthy cows. OOE was affected in the same way as CLA by the different environmental factors. PLA was a good indicator of CLA, and there was a high correlation (−0.69) between these two measurements. Treatment for lameness had a significant influence on all late fertility measurements, whereas housing was significant only for pregnancy to first insemination. All fertility traits were unfavourably associated with increased milk production. Regression of late fertility measurements on early fertility measurements had only a minor association with conception at first AI and interval from first to last AI for cows with conventional calving intervals, i.e. a 22 days later, CLA increased the interval from first to last insemination by 3.4 days. Early measurements had repeatabilities of 0.14–0.16, indicating a higher influence by the cow itself compared with late measurements, which had repeatabilities of 0.09–0.10. Our study shows that early fertility measurements have a possibility to be used in breeding for better fertility. To improve the early fertility of the cow, there are a number of important factors that have to be taken into account

On covers of cyclic acts over monoids

In (Bull. Lond. Math. Soc. 33:385–390, 2001) Bican, Bashir and Enochs finally solved a long standing conjecture in module theory that all modules over a unitary ring have a flat cover. The only substantial work on covers of acts over monoids seems to be that of Isbell (Semigroup Forum 2:95–118, 1971), Fountain (Proc. Edinb. Math. Soc. (2) 20:87–93, 1976) and Kilp (Semigroup Forum 53:225–229, 1996) who only consider projective covers. To our knowledge the situation for flat covers of acts has not been addressed and this paper is an attempt to initiate such a study. We consider almost exclusively covers of cyclic acts and restrict our attention to strongly flat and condition (P) covers. We give a necessary and sufficient condition for the existence of such covers and for a monoid to have the property that all its cyclic right acts have a strongly flat cover (resp. (P)-cover). We give numerous classes of monoids that satisfy these conditions and we also show that there are monoids that do not satisfy this condition in the strongly flat case. We give a new necessary and sufficient condition for a cyclic act to have a projective cover and provide a new proof of one of Isbell’s classic results concerning projective covers. We show also that condition (P) covers are not unique, unlike the situation for projective covers

New biphenyl iminium salt catalysts for highly enantioselective asymmetric epoxidation: role of additional substitution and dihedral angle

New biaryl iminium salt catalysts for enantioselective alkene epoxidation containing additional substitution in the heterocyclic ring are reported. The effects upon conformation and enantioselectivity of this additional substitution, and the influence of dihedral angle in these systems, has been investigated using a synthetic approach supported by density functional theory. Enantioselectivities of up to 97% ee were observed

Strutjet-powered reusable launch vehicles

Martin Marietta and Aerojet are co-investigating the feasibility and viability of reusable launch vehicle designs. We are assessing two vehicle concepts, each delivering 8000 lb to a geosynchronous transfer orbit (GTO). Both accomplish this task as a two-state system. The major difference between the two concepts is staging. The first concept, the two-stage-to-orbit (TSTO) system, stages at about 16 kft/sec, allowing immediate return of the first stage to the launch site using its airbreathing propulsion system for a powered cruise flight. The second concept, the single-stage-to-orit (SSTO) system, accomplishes stage separation in a stable low earth orbit (LEO)

The Strutjet Rocket Based Combined Cycle Engine

The multi stage chemical rocket has been established over many years as the propulsion System for space transportation vehicles, while, at the same time, there is increasing concern about its continued affordability and rather involved reusability. Two broad approaches to addressing this overall launch cost problem consist in one, the further development of the rocket motor, and two, the use of airbreathing propulsion to the maximum extent possible as a complement to the limited use of a conventional rocket. In both cases, a single-stage-to-orbit (SSTO) vehicle is considered a desirable goal. However, neither the "all-rocket" nor the "all-airbreathing" approach seems realizable and workable in practice without appreciable advances in materials and manufacturing. An affordable system must be reusable with minimal refurbishing on-ground, and large mean time between overhauls, and thus with high margins in design. It has been suggested that one may use different engine cycles, some rocket and others airbreathing, in a combination over a flight trajectory, but this approach does not lead to a converged solution with thrust-to-mass, specific impulse, and other performance and operational characteristics that can be obtained in the different engines. The reason is this type of engine is simply a combination of different engines with no commonality of gas flowpath or components, and therefore tends to have the deficiencies of each of the combined engines. A further development in this approach is a truly combined cycle that incorporates a series of cycles for different modes of propulsion along a flight path with multiple use of a set of components and an essentially single gas flowpath through the engine. This integrated approach is based on realizing the benefits of both a rocket engine and airbreathing engine in various combinations by a systematic functional integration of components in an engine class usually referred to as a rocket-based combined cycle (RBCC) engine. RBCC engines exhibit a high potential for lowering the operating cost of launching payloads into orbit. Two sources of cost reductions can be identified. First, RBCC powered vehicles require only 20% takeoff thrust compared to conventional rockets, thereby lowering the thrust requirements and the replacement cost of the engines. Second, due to the higher structural and thermal margins achievable with RBCC engines coupled with a higher degree of subsystem redundance lower maintenance and operating cost are obtainable

Effect of ionic strength on complexation of Pu(IV) with humic acid

International audienceSuccessful geochemical modelling of the migration of radioactive materials, such as the transuranic elements, from nuclear waste repositories is dependent upon an understanding of their interaction with biogeopolymers such as humic acids, the most likely complexing agents in groundwaters. An established silica/humic acid composite has been evaluated as a model substrate for naturally occurring humate-coated minerals that are likely to be present in the vicinity of the repositories. The binding of Pu(IV), the highly likely oxidation station, by the silica/humic substrate was examined at pH 4 in the range 0.02 to 3.00M NaClO$_4$ by the titration method. Pu(IV)-humate conditional stability constants have been evaluated from data obtained from these experiments by using non-linear regression of binding isotherms. The results have been interpreted in terms of complexes of 1:1 stoichiometry. Analysis of the complex formation dependency with ionic strength shows that the effect of ionic strength on humate complexation of Pu(IV) is not dramatically pronounced. The complexation constants are evaluated for the humate interaction with Pu$^{4+}$ and Pu(OH)$_3^+$ at pH 4. The complexation constants are found, respectively, to be log$^{HA}$$\beta ^0$(Pu$^{4+}$)=16.6$\pm$0.3 and log$\beta ^0_{1.3.1}$=46.6$\pm$2.3. The estimations through analogy from previous results are in agreement with these new experimental data

Kinetic Resolution in Asymmetric Epoxidation using Iminium Salt Catalysis

The first reported examples of kinetic resolution in epoxidation reactions using iminium salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes

Effects of Cryogenic Processing on Rapid Prototyping Materials (DSMSomos-8110 and DuraForm PA)

This research investigates the effects of cryogenic processing on the properties of rapid prototyped materials. Not much research has been done on the post-processing (aging) of rapid prototyped (RP) polymers at temperatures below 159K (–173˚F). Test specimens of RP thermoplastic resin DSM-Somos 8110 and DuraformPA Nylon were fabricated and cryogenically aged from 5-30 hours. The tensile strength and impact toughness were measured. The goal of this work was to study the effect of cryogenic aging on yield strength and ductility. This research investigated (1) the cryogenic aging of DSM-Somos 8110 and DuraformPA Nylon, (2) the effects of controlled ramp-downs/ups on the ultimate and tensile strengths of samples, (3) the experimental methods, and (4) the analysis and interpretation of the data.Part of this work was funded by a NSF Grant under Research Experiences for Undergraduates.Mechanical Engineerin