Solid Rocket Booster Research Articles

Artemis I Versus Wind-Tunnel Buffet-Induced Forces and Structural Responses

This paper presents comparisons of buffet forcing functions (BFFs) and associated structural responses for the Space Launch System from two data sources: 1) Artemis I (AR01) Developmental Flight Instrumentation (DFI) and 2) transonic wind-tunnel (WT) tests. Failures of DFI sensors prevented the development of a complete set of flight-based BFFs, where each BFF is based on azimuthal integration over 360 deg of unsteady pressures acquired by sensor rings placed at many longitudinal stations along the vehicle. Instead, a set of equivalent flight- and WT-based BFFs was developed based on functional DFI and WT sensors that share the same locations. Root-mean-square (rms) levels of equivalent BFFs from flight and WT data are in-family for most of the cardinal Mach numbers. However, at stations downstream of the solid rocket booster (SRB) forward attachment (FA) protuberance, the rms of flight-based BFFs exceeds their WT counterparts. Strikingly, vortex shedding off the FA protuberance occurs at lower frequencies during flight than in WT experiments. This frequency shift propagates onto the spectrum of flight-measured versus WT-based structural responses. As a result of this frequency mismatch, at certain AR01 vortex shedding frequencies, the flight responses are an order of magnitude higher than their WT-based counterparts. Thus, at AR01 vortex shedding frequencies, the WT-based BFFs do not provide an accurate estimation of the flight environments. Away from AR01 vortex shedding frequencies, the AR01-based responses are within or sometimes exceed a range of WT-based responses. This observation indicates that, outside of frequencies that are impacted by vortex shedding, the WT-based BFFs are fairly well representative of the flight environments.

Impact of Solid Rocket Propellant Grain Manufacturing Limitations on Launch Vehicle Capability

It is examined if any limitations in existing solid rocket propellant grain manufacturing methods adversely affected the payload capability of recent space launch vehicles. It is seen if the transition from heavy, segmented metal rocket motor casings to lightweight monolith composite casings is possible without loss of ability to design and realize high-performance grain configurations using simple and safe methods. Considering payload fraction as the comparative performance metric, recently flown solid rocket-propelled, small-lift launch vehicles were surveyed and ranked. Solid rocket boosters of underperforming launch vehicles were investigated for manufacturing factors influencing payload fraction by comparing them to boosters of better-performing launch vehicles in their weight class. Relationships between payload fraction and the solid boosters’ mass fractions, casing construction, shape of thrust profile, propellant grain configuration and method employed to manufacture the grain were analysed. It is shown that those launch vehicles that did not possess or use the technology necessary to manufacture high-performance grain configurations like undercut finocyl in monolith composite casings ended up having boosters delivering poor thrust profiles with high inert mass ultimately leading to low payload fractions.

Advances in Space Launch System Booster Separation Computational Fluid Dynamics

The Space Launch System (SLS) employs two Space Shuttle–derived solid rocket boosters, which separate from the SLS core while still experiencing appreciable aerodynamic loads. Creating an aerodynamic database for this phase of flight can be challenging due to the large number of independent variables needed to fully constrain the problem and the complex flow induced by exhaust plumes of the booster separation motors and core main engines impinging on other parts of the vehicle. This paper details recent efforts in generating aerodynamic data used to create databases for the SLS during the booster separation event using viscous computational fluid dynamics (CFD) simulations obtained using NASA’s FUN3D solver. Particular challenges faced when modeling a complex problem, such as booster separation, are presented. Reductions in interpolation error estimates were observed through the introduction of a physics-based covariance approach to building the CFD run matrix, eliminating infeasible booster location permutations that could potentially skew final response surfaces. Interpolation error control is shown using test cases outside of the main database. Code-to-code comparisons between the FUN3D and OVERFLOW solvers are also presented to further verify the results.

A study on the effect of weld repair on the structural margins of a solid rocket booster hardware

Cylindrical shells in one of ISRO’s solid rocket booster is fabricated from ultra-high strength steel (M250 Maraging steel) through rolled and welded construction. This steel being a fracture prone material, elastic-plastic fracture mechanics-based design is followed for the design of cylindrical shell. The no-flaw failure pressure i.e. elastic plastic failure pressure (Pb) of the cylinder is an important parameter in design. For a given diameter of cylindrical shell, Pb is a function of shell thickness and mechanical property. If any unacceptable flaw is found on welds during NDT, repairs are carried out in the weld region. Mechanical properties of weld/weld repairs are lower when compared to parent material. It is seen that, at any location, if it is repaired twice, the strength reduces by 21% when compared to the parent metal property. Thus, the mechanical properties of the weld region dictate the overall design thickness of the cylindrical shell. A study is carried out to find the effect of length of weld repair zone on the Pb. A parametric 3D FE model simulating the repair in long seam weld, cirseam weld and combination of long seam & cirseam weld in cylindrical shell is used for this purpose. It is found that the effect of parent metal property needs to be considered while estimating Pb. Further while considering the repair in long seam, the length of repair also needs to be considered. Pb is found to increase considering its effect. This study was helpful in establishing more realistic structural margins in a solid rocket booster case which had weld repair.

Comparison of Corcos-Based and Experimentally Derived Coherence Factors for Buffet Forcing Functions

In this paper, high-spatial-resolution unsteady pressure-sensitive paint (UPSP) data are utilized to compare two methods for panel buffet forcing function (BFF) estimation for the Space Launch System (SLS). Such methods are based on discrete pressure measurements within a panel but employ coherence factors to account for partially correlated fluctuating pressures across the whole panel. In one method, coherence factors are derived based on the Corcos model, whereas the second method utilizes experimentally derived coherence factors. To simulate discrete measurements using UPSP data, suitable subsets of the data are extracted. When full UPSP resolution is retained, UPSP data provide a benchmark to assess discrete-measurement-based methods. The analysis focuses on the peak SLS buffet environment located downstream of the forward attachment hardware (FAH) between the core stage and solid rocket boosters. Trends of the Corcos-based and experimentally derived coherence factors are in reasonable agreement with the benchmark. However, at certain frequencies, experimentally derived coherence factors are sensitive to the separation distance between pressure measurements utilized to compute coherence lengths. Such sensitivity originates from deviation of the experimentally based coherence function from an exponential decay assumption. On the other hand, the present implementation of the Corcos model fails to capture certain nonturbulent boundary-layer-related environments, such as a subharmonic of FAH vortex shedding. For all methods presented in this paper, at near-transonic conditions, increased pressure coherence and spatial nonuniformity lead to BFF overestimation and sensitivity to the pressure measurement location within the panel.

Solid Rocket Boosters Separation System Development for the ILR-33 Amber 2K Rocket

Abstract The paper presents the development process of the solid rocket boosters (SRBs) separation system of the ILR-33 AMBER 2K rocket. A redesign of the system was required due to the development of new, larger SRBs. The main system requirements were transmission of forces and moments between the SRBs and the main stage, execution of the separation process at a given moment in flight and mechanical integration simplification. A set of aerodynamics calculations were performed. With the use of computational fluid dynamics software, forces acting on the booster during separation for several angles of attack, as well as the critical booster deflection angle, have been determined. Next, a mathematical model was created to define the load spectrum acting on the system during the flight and separation phases, covering both static and dynamic loads. All the internal and external force sources were considered. A series of motion dynamics simulations were conducted for representative flight cases. Then, the system operational parameters were verified with the use of dedicated ground test facilities. Necessary calibrations of the mathematical model were then implemented, leading to a high level of confidence with the empirical data obtained, thereby leading to a successful system qualification for the flight campaign.

Experimental and numerical investigation on design parameters of slot nozzles

Slot nozzles are altitude compensation nozzles. In the overexpansion mode, slots in the expansion section can affect the flow separation and improve the thrust. In this study, cold-flow experiments and numerical simulation are performed to study the design parameters of slot nozzles. The effects of slot location, number, and vented area on the flow field, thrust, and average specific impulse of the first-stage rocket are investigated. The results show that the thrust increases due to two reasons: the advance of the separation position and the rise of wall pressure in the recirculation zone. Moreover, the slot location is more important than other parameters in the design of slot nozzles. Only when a slot is close to the flow separation point, the influence of the slot on the flow field is apparent, thus, the thrust significantly and efficiently increases. The performance of the first-stage rocket can be significantly improved by replacing the traditional bell nozzles with slot nozzles. The average specific impulse increase of the space shuttle solid rocket booster and first-stage rocket of the nano launch vehicle (NLV) is 5.1 s and 7.9 s, respectively; further analysis of NLV shows that its payload can be increased by 16.1%.

Recent Advances of Design Optimization Techniques in Solid Rocket

A solid-propellant rocket or solid rocket refers to a rocket with an engine using solid propellants. The earliest solid rockets were powered by gunpowder. It is still used today in military armaments worldwide, model rockets, solid rocket boosters and on larger applications for their simplicity and reliability. With the fast development in the complexity of rockets, the importance of optimisation where the overall performance is maximised has been shown. Engineers are routinely given design tasks to find a design meeting the stringent constraints. For instance, researchers developed different optimisation techniques to maximise the overall performance while decreasing the economic and time requirements. This paper has reviewed four types of recent advances in design optimisation techniques used in solid rockets, with all the findings and analysis summarised. In conclusion, this study provides a useful reference to people who would like to know about different types of optimisation used in the current astronautical engineering field.

Ascent adaptive energy management method for solid rocket‐powered hypersonic vehicle under uncertainties

SummaryThe solid rocket booster is widely used in the launch mission for hypersonic vehicles nowadays, whose ascent energy management is still a challenging problem due to the inherent dynamic nonlinearity. This paper casts the problem into an equivalent ascent guidance one and proposes a model predictive static programming (MPSP) based solution. The MPSP‐based method is a computationally efficient solver that adapts to different energy demands while guaranteeing the satisfaction of terminal constraints. To further improve the performance of MPSP in this problem, a Bézier spline guidance method is proposed to generate high‐quality reference trajectories such that the MPSP can converge with high accuracy while satisfying the real‐time requirement. Additionally, an online parameter estimation based on the extended Kalman filter is employed to avoid large terminal state deviations incurred by parametric uncertainties during the Bézier curve computation and linearization in MPSP. Numerical simulations with different hard terminal constraints and uncertainties are conducted to demonstrate the effectiveness and robustness of the proposed algorithm. The simulation results show that our proposed algorithm can guide the hypersonic vehicle to a given terminal state under uncertainties and outperforms several existing ascent energy management methods.

Space Launch System acoustics: Far-field noise measurements of the Artemis-I launch.

To improve understanding of super heavy-lift rocket acoustics, this letter documents initial findings from noise measurements during liftoff of the Space Launch System's Artemis-I mission. Overall sound pressure levels, waveform characteristics, and spectra are described at distances ranging from 1.5 to 5.2 km. Significant results include: (a) the solid rocket boosters' ignition overpressure is particularly intense in the direction of the pad flame trench exit; (b) post-liftoff maximum overall levels range from 127 to 136 dB, greater than pre-launch predictions; and (c) the average maximum one-third-octave spectral peak occurred at 20 Hz, causing significant deviation between flat and A-weighted levels.

Simulating Rocket Trajectory Using JSBSim and Optimal Thrust Profile for maximizing altitude of sounding rocket

Solid rocket boosters are commonly used for launching sounding rockets due to their simplicity and power-ness. The shape and geometry of the propellant grain determine the thrust-time profile which has a significant effect on rocket performance. In practical application, the thrust profile has three typical curves; regressive, neutral, and progressive. A great deal of studies has been focused on optimizing the trajectory based on various state variables in which the profile of the thrust-time curve was not among those variables. In this research, design variables were the thrust profile, the object function was maximizing the altitude subjected to constraints of a fixed amount of fuel. The trajectory was found by solving the equations of motion. For comparison purposes, the trajectory was also found using JSBSim, an open-source flight dynamic simulator. In the final results of the optimization process, the input thrust-time curve was evolved into an unusual shape, the letter “V” shaped. In this type of profile, the thrust curve starts regressively until reaches zero value at the middle of the burning time and then continues progressively until the end. This behavior can be satisfied only by two-stage boosters. Thus, these results show that two-stage boosters perform better than single-stage. The improvement is obtained by consuming the solid propellant more efficiently allowing fewer energy losses. This reason is added to the fact that two-stage boosters allow reducing the total masses due to the casste separation.

Arkema's specialty materials protect NASA's logo as it blasts off to Space

On December 7, 2022, Arkema announced it was selected to protect NASA's logo on the Artemis 1 Space Launch System (SLS). The coating is powered by Arkema's Kynar Aquatec® PVDF latex and is claimed to provide extreme durability to keep NASA's red “worm” logo on the solid rocket boosters intact while soaring to space.

Launching to an orbit with a chemical propellant staged rocket systems

There is one way to explore space by using the space launch vehicles, which is known as rockets, and it can carry useful load named simply as payload of satelite from Earth into Space. In this study, performance predictions of the multi rocket motors are discussed and compared with single rocket motor with the same amount of propellant used for space travel. In this article in serial or tandem staging schemes, the boosting stage is usually the largest, the second stage and subsequent upper stages are above it, usually decreasing in size are used. In boosting stage parallel staging schemes solid or liquid rocket boosters are used to assist with launch. At low level starting to high altitude higher density fuel solid fuels, kerogen and cryogenic hydrogen(-250°C) are used as fuel. In solid propellants oxidizer is generally ammonium per chloride is used but in cryogenic liquid propellants oxygen(183.3°C) are used. In the first stage, both liquid propellant in a booster and five solid rocket propellent are used to reach about a certain altitude and velocity. In second stage, after reducing the weight by ejecting the five solid rocket propellent and only liquid propellant is used only to reach the an extra altitudes and velocities at low earth orbit (LEO). Drag and gravity effects are successfully used in all of the calculations. The added total result of velocities and altidudes found by these staged rockets are higher than the first single staged case. The advantage of multistage rockets, having same amount of propellant in staged rockets where total velocity will be increased by separating and removing waste from the system weight out of the system. Use of staged rocket system are usefull for increasing the amount of payload and decreasing the cost per unit weight as well.

Acoustical measurement and analysis of an Atlas V launch without solid rocket boosters

In September 2021, an Atlas V rocket without solid rocket boosters was launched from Vandenberg Space Force Base, California, carrying the NASA/USGS Landsat 9 satellite. In this launch configuration, the plumes from the RD-180 engine’s two nozzles are unobstructed, providing the opportunity to analyze the sound generated by a liquid-fuel rocket engine with an azimuthally asymmetric nozzle geometry. Acoustical data were collected at various locations surrounding the launch pad, ranging from a few hundred meters to several kilometers. This paper discusses an overview of the measurement logistics, the types of analyses that may be performed using these data, and an initial analysis of the azimuthal variability of the overall sound pressure level and spectra.

Design of Supersonic and Hybrid engine based Advanced Rocket (SHAR)

The paper deals with the design of a two-stage to orbit rocket launcher loaded with a solid rocket booster, scramjet, and hybrid rocket for delivering a 100kg payload in 200 km circular orbit. The possibility of implementing a cavity-based axisymmetric circular combustor in a scramjet is proposed. Computational analysis on various injector locations in a circular combustor and their validation with the test bench results were performed. The utilisation of a hybrid rocket in the final stage of the launcher to deliver the payload is discussed and the performance characteristics of the circular scramjet combustor and the hybrid rocket are shown. The overall mission proposed based on the sustainable and reusable characteristics.

Effects of inclusions on the performance of a solid rocket motor

Some of the most common defects that can be generated during the production of solid propellant are voids and porosity, usually associated with the casting process, and cracks and debonding, typically initiated by the high stresses caused by the curing process. This paper presents the development of an algorithm capable of evaluating the burning surface regression of a solid rocket booster when inclusions are present within the grain. The effects produced by the cavities are evaluated both in terms of performance (i.e., comparison with the behavior of the nominal combustion surface), and in terms of safety (i.e., evaluation of the thermal protection increased exposure). The paper also documents the influence of uncertainties in the knowledge of the real dimension and position of the inclusions detected within the motor. The radiography inspection of the motor is able to detect the presence of cavities within a certain level of accuracy, and the worst combination of these uncertainties has to be determined in order to guarantee, even under such circumstances, the safe and successful firing of the motor. The methodology developed in the paper is adapted in order to identify the worst uncertainty combination, and to subsequently determine the corresponding performance deviation.

Vertical Wedge Drop Experiments as a Model for Slamming

_ A deeper comprehension of hydrodynamic slamming can be achieved by revisiting the wedge water entry problem using flexible structures. In this work, two wedge models that are identical, with the exception of different bottom thicknesses, are vertically dropped into calm water. Pressure, full-field out-of-plane deflection, strain, vertical acceleration, and vertical position are measured. Full-field deflections and strains are measured using stereoscopic-digital image correlation (S-DIC) and strain gauges. A nondimensional number, R, quantifying the relative stiffness of the structure with respect to the fluid load is revisited. An experimental parametric study on the effect of R on the nondimensional hydrodynamic pressure and the maximum strain is presented. It was found there is a sharp change in the trend of pressure and strain when R passes through a critical value. It was also discovered that the structural deformation causes a delay in the peak pressure arrival time and a reduction in the peak pressure magnitude during the wedge water entry. Introduction When high-speed planing craft operating in waves becomes airborne and reenters the water surface, a substantial impact or “slam” between the vessel bottom and the water surface will occur (Faltinsen 2005; Lloyd 1989). The bottom slamming events occur frequently and may injure the passengers, compromise the equipment onboard, or even damage the structure. Slamming is a major cause of speed reduction in small craft where slamming loads are important. Current design criteria are primarily based on empirical measurements with little regard for the fluid–structure interaction (FSI) physics of the slamming phenomenon. This study offers a first step toward better understanding of FSI in slamming for optimal structural design in the future. Since the cross sections of most surface effect ships may be approximated by a V-shaped wedge, the slamming characteristics of these sections may be examined by dropping a wedge model into water (Faltinsen 2005; Lloyd 1989). Studying the wedge water entry problem is also helpful in shedding light on the wet deck slamming of catamaran, sloshing under the chamfered roof of a partially filled tank (Faltinsen 2000), seaplane landing (Wagner 1932), water landing of spacecraft and solid rocket boosters, water landing/ditching of aircraft (Abrate 2013), and animal diving behavior (Chang et al. 2016).

Image-Based Analysis of Interactions Between a Steady Jet and an Impulsively Started Jet

Ignition overpressure (IOP) is a principal dynamic load experienced by a launch vehicle during liftoff. The IOP arises due to the sudden ignition of the solid rocket boosters (SRBs) of a launch vehicle. The present work attempts to simulate the ignition of an SRB with an impulsively started supersonic jet generated using a quick-open valve. High-speed schlieren flow visualization is used to document the evolution of an impulsively started jet flowfield that included the characteristic precursor shock wave (that simulates the blast wave causing the IOP) and the following vortex ring. The dynamic interactions between the impulsively started supersonic jet and an established steady supersonic jet from another nozzle () in close proximity are also investigated. Both the precursor shock wave and the vortex ring interact strongly with the established steady-jet column as they proceed downstream from the nozzle exit, thereby introducing new sources of acoustic waves. When a generic jet blast deflector is introduced downstream of the nozzles, the precursor shock wave reflected from it, propagating upstream toward the nozzle exit. The reflected shock wave is recognized as the source of IOP experienced by the launch vehicle. The results show that the quick-open valve presents a unique way to generate impulsively started jets for understanding transients associated with the ignition of the SRB leading to the IOP, without the complexity associated with the use of open-ended shock tubes for carrying out such simulations.

Analytical studies and numerical predictions of stresses in shear joints of layered composite panels for aerospace applications

Composite laminated structural members are joined to the neighbouring parts using mechanical fastening. The segmented composite motor case for solid rocket boosters is one of the typical examples where such a joint could be adopted effectively, in which segmentation of pressure vessels is essential to use such a joint. Design analysis of such a joint is made for assessing the load transfer mechanism among shear bolt rows, and a fitting factor is derived. The fastened joint is observed practically more reliable than bonded joints due to inherent bond quality issues. An analytical model is generated taking care of variation of laminate stiffness along bearing surface with consideration to vary the stiffness of laminates along the circumference using two layup sequences of Carbon Fibre Reinforced Polymer. Cutting of fibres around the shear hole causes strength properties to reduce significantly, around the drilled holes. Finite Element (FE) analysis is performed using ABAQUS to support the joint design and predict the propagation of damage using Tsai-Wu theory. The current study is to understand the stress conditions around the shear hole and check the proximity of FE predictions with analytical calculations on trends of stress components along the contact surface of each ply orientation.

Simulation of Ariane 5 Solid Rocket Booster Deformation by Internal Ballistics

During their operation, solid rocket boosters experience axial stresses caused among other things also by fluid mechanical loads from the internal flow. The accurate prediction of the flowfield is mandatory for an accurate prediction of axial stresses and strains during the mission. In the present Paper, a very efficient but still accurate approach is presented to simulate the internal flow featuring an erosive combustion process, which leads to a temporal variation of the fluid domain. The impact of the calculated fluid behavior on the calculation of axial strains is demonstrated using the example of a firing test, where it can be shown that by taking into account the fluid behavior a significant improvement on the axial strain prediction could be achieved compared to the previous method, in which the fluid mechanical impact partly had been neglected.