Numerical Study of Flow Augmented Thermal Management for Entry and Re-entry Environments

Abstract

Tremendous amounts of heat and drag loads occur during entry and re-entry into planetary and earth atmospheres have posed grave challenges on maintaining structure integrity of space exploration vehicles. Though various thermal protection systems (TPS) have been employed to manage the heat loads, both localized and transient spikes at stagnation points, the use of TPS can substantially increase the weight of the vehicle. Hence, various concepts, such as aeroassisted orbital transfers and aerobraking, have been designed to mitigate the high heating rates such that the TPS weight can be minimized. Among those concepts, the use of a flow augmented thermal management system for entry and re-entry environments has shown some promises in reducing heat and drag loads. This concept relies on jet penetration from supersonic and hypersonic counterflow jets, that could significantly weaken and disperse the shock-wave system of the spacecraft flowfield to reduce wave drag and aerothermal loads. Greatly reducing wave drag and aerothermal loads significantly enhances aerothermal performance, allowing thinner or much lighter TPS to be used, which translates into spacecraft weight and cost savings. Other benefits include better aerodynamic efficiency and improved down-range and cross-range maneuverability. There are two jet penetration modes involved in a supersonic/hypersonic flow interacting with counterflow jets: short penetration mode (SPM) and long penetration mode (LPM) interactions. Previous studies have shown that the LPM jet significantly increases the shock stand-off distance, thus reducing the strength of bow shock, which leads to a reduction in wave drag. The LPM jet acts as, in essence, a "pencil" of fluid with high dynamic pressure, penetrating into the incoming freestream, to attenuate the shock system. Though the function of the LPM jet has been demonstrated in the previous study, further experimental and computational analyses through trade studies are required to determine the optimum operating conditions of the LPM jet.The objective of this study is to provide a practical design approach to the development of flow control technologies as spacecraft subsystem(s) for better thermal management, aerodynamic efficiency, control authority and range, and improvements in payload mass fraction of the spacecraft in entry and re-entry atmospheres using counterflowing LPM jets to significantly modify/reshape the external flow environment and weaken the shock. To achieve this goal, we have conducted numerous time-accurate and steady-state computational fluid dynamics (CFD) simulations of the supersonic flow around an Apollo-type capsule with and without the counterflow jet using a Reynold-averaged Navier-Stokes (RA S) flow solver--UNIC code. Axisymmetric RANS simulations were first conducted to investigate the grid convergence for this type of flowfield. Parametric studies of different freestream Mach numbers (3.48 and 4.96),

A tightly-coupled domain-decomposition approach for highly nonlinear stochastic multiphysics systems

“…For the boundary conditions formulated in Section 2, this approach results in deterministic boundary-value problems in Ω 2 and Ω 3 , which yields zero concentration variance to the right of x = α 1 , and hence cannot propagate the noise generated at x = 0 throughout the entire computational domain. 3 We will investigate the effect this has on the resulting average concentration profile in Section 5.1.…”

“…Many of these problems involve constituent processes that occur in separate spatial domains and influence each other through the interfaces between these domains. One example is conjugate heat transfer across a fluid-solid interface [1], which manifests itself in applications as diverse as gas turbine cooling [2] and vehicle entry and re-entry in planetary atmospheres [3].…”

“…5. Use JfNK to calculate new iterates of the interfacial concentrations,ρ n,k+11,N 1 andρ n,k+12,N 2 , and fluxes,F n,k+1 2,1/2 andF n,k+1 3,1/2 3. A stochastic boundary condition at x = L would require computation of N sam trajectories in Ω 3 , while still having to solve the deterministic problem in Ω 2 .…”

Application of a Reynolds-Averaged Navier–Stokes Approach to Supersonic Retropropulsion Flowfields

“…Daso et al, 14 Chang et al, 17 and Cheng et al 18 conducted analyses using a 2.6%-scale Apollo capsule with and without retropropulsion effects. In all cases, the analyses were attempting to predict the aerodynamic and aerothermal effects of a centrally-located nozzle exhausting air (into air) at freestream Mach numbers of 3.48 and 4.0.…”

Numerical Study of Counterflowing Jet Effects on Supersonic Slender-Body Configurations

“…[9][10][11][12][13][14] Two different modes of jet interaction with the oncoming freestream exist, namely the short penetration mode (SPM) and long penetration mode (LPM), pictorially represented in Fig. 1.…”