An experimental investigation of high-enthalpy flow over a toroidal ballute (balloon/parachute) was conducted in an expansion tube facility. The ballute, proposed for use in a number of future aerocapture missions, involves the deployment of a large toroidal-shaped inflatable parachute behind a space vehicle to generate drag on passing through a planetary atmosphere, thus, placing the spacecraft in orbit. A configuration consisting of a spherical spacecraft, followed by a toroid, was tested in a superorbital facility. Measurements at moderate-enthalpy conditions (15-20 MJ/kg) in nitrogen and carbon dioxide showed peak heat transfer rates of around 20 MW/m 2 on the toroid. At higher enthalpies (>50 MJ/kg) in nitrogen, carbon dioxide, and a hydrogen-neon mixture, heat transfer rates above 100 MW/m 2 were observed. Imaging using near-resonant holographic interferometry showed that the flows were steady except when the opening of the toroid was blocked. Nomenclaturespacecraft center-to-center offset from toroid, mm h = specific enthalpy, J · kg −1 K = stagnation point streamwise velocity gradient, s −1 L = characteristic length scale, m M = Mach number m = order of truncation error in computational fluid dynamics (CFD) code N = number of cells in the simulation Pr = Prandtl number p = pressure, Pȧ Q = total heat flux, Ẇ q = heat flux, Wm −2 Re = Reynolds number based on freestream properties and U eq Re e = Reynolds number based on postshock properties and U eq r = toroid cylinder radius, 3 mm St = Stanton number based on freestream conditions St e = Stanton number based on postshock density using U eq as the velocity T = temperature, K U = velocity, m · s −1 U eq = equivalent flight speed √ (2 × stagnation enthalpy), m · s −1 γ = specific heat ratio x = length of a cell within the grid of the CFD code µ = viscosity (Pa · s) ρ = density, kg · m −3 Subscripts and Superscripts e = ballute stagnation conditions eq = equivalent flight conditions w = wall conditions 0 = isentropic total conditions 1 = initial (fill) value 2 = postprimary shock value ∞ = freestream in test section

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The achievement of optimal closure outcomes hinges on a robust planning and execution process. Closure planning should be an integral part of an asset's lifecycle, with a formal, detailed planning process being initiated towards the end of operational cessation. Useful guidelines, case studies, and project delivery models exist to assist the closure planning process. While these provide a structured framework for addressing key elements of closure, they do not transcribe all circumstances, complexities, and decisions faced by an asset owner and impacted parties.The ability to optimise closure execution diminishes once the preferred closure scenario is committed to by the appropriate decision-makers, with a subsequent escalation of change implementation cost over time. From a myriad of interdependent and sometimes conflicting requirements, variables and uncertainties, an asset owner must find a way to achieve a balanced scorecard while meeting its obligations and stakeholder expectations. To this aim, this paper presents a potential process map for determining the preferred closure scenarios, including instructional steps, a hybrid options assessment model, and examples for each component.Prior assumptions should be verified through data gathering to fill knowledge gaps, establish context and baseline knowledge, and define the relevant closure domains and work elements. With the necessary input of subject matter experts, technical practitioners and project stakeholders, a set of integrated trade-off studies can be carried out using multi-criteria analysis (MCA) to assess the merit and impact of key decisions under each closure scenario. Compatible options between trade-off studies can be linked up to form branches of a decision tree for each closure scenario, where preferences on possible decisions are revealed by the quantitative MCA scoring as well as qualitative ranking of the trade-off studies. Given the subjective nature of these assessments, different perspectives should be adequately considered/challenged, and the results tested through sensitivity analysis. The options selection process should be transparent, rigorous, defensible and well documented to form a robust basis for decisions that will have an enduring legacy.

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