Common Bulkhead Tank Design for Cryogenic Stage of an Indian Launch Vehicle

Indian Space Research Organization (ISRO) has been advancing in space technology with its cost-effective techniques. Currently, ISRO, in its cryogenic stages, uses truss type intertank structure, which induces large concentrated loads at the truss interfaces. As a remedial measure, works on closed intertank are being carried out by them, but this configuration will considerably increase the launch vehicle mass compared to truss type. Therefore, after a thorough literature survey, a Common bulkhead (CBH) tank seemed to be the best solution to the aforementioned problem. Detailed research on sandwich-type CBH has been carried out in this paper with the motivation of saving mass and height in launch vehicles. Suitable core and facesheet material were selected. A novel foam-filled honeycomb core is suggested in this work. Several comparisons in various CBH dome designs were carried out to reach for the best possible configuration and composition that can be used. MATLAB®, SolidWorks®, and ANSYS® were used in parallel for all computations dealing with design and analysis. A mass saving of approximately upto 490 kgs and a height reduction of upto 1.755 m was obtained with the final selected configuration with respect to the current GSLV configuration. These savings can add extra payload capacity to ISRO launch vehicles in their future missions.

Aerothermal databases and load predictions for Retro Propulsion-Assisted Launch Vehicles (RETALT)

The assessment of thermal loads occurring on reusable launch vehicles during the entire trajectory is essential for the correct dimensioning of the thermal protection system. Due to the costs and limitations of ground-based testing for large-scale vehicles, these predictions rely intensively on numerical simulations (CFD). The need of aero-thermal databases, as a fast-response surrogate model for the aero-thermodynamic heating, arises from the practical impossibility of performing unsteady CFD analysis over the entire trajectory due to the large disparity of fluid mechanical and structural time scales. The construction of these databases is based on a representative set of CFD simulations which cover, at a minimum, the flight regimes with significant thermal loads. The aim of this paper is to analyse the results of these representative CFD simulations during both the ascent flight and atmospheric entry for the RETALT1 vehicle to show typical flow field phenomena occurring during these phases and the resulting heating patterns.

A new method to specify the mitigated acoustic test conditions from flight telemetry based on the equivalence of vibro-acoustic response

Ground acoustic tests using stationary sound pressure level spectrum have been conducted to verify the spacecraft survivability against acoustic environment acting on a spacecraft during launch, which is a non-stationary and random dynamic load. In general, a stationary spectrum used in ground acoustic test is traditionally determined by a method called maximax spectrum, which is the enveloped spectrum of time varying non-stationary short-time Fourier transform. However, the maximax spectrum is more or less an excessively conservative test condition because this spectrum focuses on processing of a time-varying acoustic signal itself to extract maximum value, rather than on how the vibro-acoustic response of an excited structure is. In this paper, a new method is proposed to specify a stationary spectrum equivalent to a structural vibro-acoustic response under a non-stationary and random acoustic environment based on extreme response spectrum and fatigue damage spectrum. This proposed method was applied to flight telemetry of both liquid- and solid-propellant launch vehicles developed by JAXA, to show its effect to mitigate the acoustic test conditions compared to the maximax spectrum while maintaining the equivalence of the structural vibro-acoustic response. Furthermore, the maximum predicted environment, which is the statistical upper percentiles of the flight telemetry of eight liquid-propellant launch vehicles, by the proposed method achieved a mitigation of about 2.5 and 6.8 dB in the extreme stress and cumulative fatigue, respectively, compared to the that which is calculated by the conventional maximax spectrum.

Investigation of tape flexures for space borne deployable structures

Space exploration arises the demand for launching large size structures to satisfy the need of high bandwidth telecommunication, earth observation and deep space interplanetary missions. Launching of these monolithic structures of sizes 3 m or more are not feasible due to limited launch fairing space of state-of-the-art launch vehicles. Therefore, the development of innovative deployment mechanisms is need of the hour. Deployment process of space borne deployable systems is the process of transition from mechanism to structure which is one of the unreliable stage due to existence of many conventional rotary joints which causes loss of energy due to backlash, friction and misalignment. An investigation study is presented in this paper for churning out a solution of flexible hinges using tape springs in state-of-the-art space deployable configurations which eliminates the factors causing loss of energy. Analytical and experimental methods are evaluated for investigating the bending behaviour of tape flexures. Tape flexures demonstrate to be a suitable candidate for compliant deployable configuration. The proposed configuration with combination of two tape flexures mounted in such a way that concave curve of each tape faces each other are structurally analysed for desired rotation angle. A comparison study is carried out for various material options of single and double layered tape flexures proposed for a flexure hinge. Practical feasibility of the proposed configuration is also demonstrated successfully on space borne deployable structures.

A method of forming a spacecraft adapter layout to meet the requirements of dynamic compatibility by topological and parametric optimization methods

At present, the developers of launch vehicles impose a requirement for dynamic compatibility of the spacecraft with the launch vehicle, which consists in limiting the lower boundary of the first transverse and first longitudinal fundamental (primary) frequencies of the natural vibrations of the spacecraft fitted with an adapter of relatively rigid base. One of the tasks that must be solved in order to meet this requirement is the development of the spacecraft adapter layout. The traditional process of designing the adapter consists in developing its design on the basis of analogues and carrying out verification analysis with subsequent refinement of the design to meet the strength and stiffness requirements. However, this approach takes a lot of time and is not adaptable to constant changes in the input data at the initial design stage. The article presents a technique allowing the adapter layout to be quickly designed. The layout is determined to a greater extent by calculations using the topological and parametric optimization methods. The application of the developed technique is shown on the example of the development of an adapter for a promising spacecraft. It should be applied in the early stages of design. The results obtained by the method should be used as input data and recommendations for the design of the adapter.

Development of Advanced Technology and Equipment for Manufacture of Titanium Spherical Vessels

The most promising in the world practice are launch vehicles using titanium spherical vessels in a cryogenic medium at high pressure. The paper deals with an import-substituting technology, which provides a closed production cycle for the manufacture of titanium spherical vessels at the JSC “Chemical Automatics Design Bureau” and analyzes existing manufacturing technologies. We developed an innovative method of shaping and machining hemispheres from hard-to-deform advanced titanium alloys, providing maximum automation and productivity of the process. For hydraulic and cryogenic tests of submersible titanium vessels, bench equipment was developed and introduced into production. For simulating the facility operating conditions in order to reduce the cost and increase the safety of tests, liquid oxygen was replaced with liquid nitrogen and helium was replaced with high-pressure nitrogen. Within the study, we substantiated the area of ??effective use of the import-substituting technology and developed production facilities of a closed cycle for the production of titanium vessels with a capacity of 25 and 130 liters.