Low-Density Aerodynamics of the Stardust Sample Return Capsule

Self Cite

The supersonic transitional flow aerodynamics of the inflatable reentry vehicle experiment are simulated with the direct simulation Monte Carlo method. Also, results from Navier-Stokes calculations are presented that provide both a check on the direct simulation Monte Carlo results near continuum conditions and the general trend of the aerodynamic data at lower altitude conditions. Calculations of axial, normal, and static pitching coefficients are obtained for an angle-of-attack range of 0 to 180 deg. These results clearly demonstrate the strong sensitivity of the aerodynamic coefficients to the relatively low speeds encountered as the inflatable reentry vehicle experiment reenters the atmosphere, and that existing hypersonic aerodynamic data bases for similar geometric configurations are not appropriate for the inflatable reentry vehicle experiment environment. The current numerical simulations focus on the rigid body aerodynamics from 150 to 91 km altitude for the 0 to 180 deg angle of incidence sweep and to lower altitudes (46 km) while at zero incidence. Nomenclaturemaximum diameter of spacecraft, m Kn 1;D;HS = freestream hard sphere Knudsen number, 1 =D mcs = mean collision separation distance, m mfp = mean free path, m n = number density, m 3 p = pressure, N=m 2 q = wall heat transfer rate, W=m 2 T = temperature, K V 1 = freestream velocity, m=s x; y; z = model coordinates, m X = mole fractions = angle of incidence, deg 1 = mean free path in freestream, m 1 = freestream density, kg=m 3 Subscripts D = maximum spacecraft diameter HS = hard sphere W = wall 1 = freestream

Section: Comparisons Of Irve Data To Hypersonic Data For a Similarmentioning

confidence: 99%

Low-Density Aerodynamics for the Inflatable Reentry Vehicle Experiment

Moss

Glass

Hollis

et al. 2006

Self Cite

“…2¡6 The low-density aerodynamics of the Stardust SRC is discussed in Ref. 2. A subset of the DSMC results is presented in Table 1.…”

Section: Low-density Aerodynamicsmentioning

confidence: 99%

Aerodynamics of Stardust Sample Return Capsule

Mitcheltree

Wilmoth

Cheatwood

et al. 1999

Successful return of interstellar dust and cometary material by the Stardust SampleReturn Capsule requires an accurate description of the Earth entry vehicle's aerodynamics. This description must span the hypersonic-rarefied, hypersonic-continuum, supersonic, transonic, and subsonic flow regimes. Data from numerous sources are compiled to accomplish this objective. These include Direct Simulation Monte Carlo analyses, thermochemical nonequilibrium computational fluid dynamics, transonic computational fluid dynamics, existing wind tunnel data, and new wind tunnel data. Four observations are highlighted: 1) a static instability is revealed in the free-molecular and early transitionalflow regime due to aft location of the vehicle's center-of-gravity, 2) the aerodynamics across the hypersonic regime are compared with the Newtonian flow approximation and a correlation between the accuracy of the Newtonian flow assumption and the sonic line position is noted, 3) the primary effect of shape change due to ablation is shown to be a reduction in drag, and 4) a subsonic dynamic instability is revealed which will necessitate either a change in the vehicle's center-of-gravity location or the use of a stabilizing drogue parachute. IntroductionTARDUST', the fourth Discovery class mission, S is scheduled for launch in February of 1999. In addition to collecting interstellar dust, the robotic spacecraft will fly within 100 km of the comet Wild-2 nucleus and collect pre-solar cometary material from the coma parent-molecular zone. These materials will be returned to Earth for submicron level analysis. To accomplish the mission's objective, a capsule containing the collected particles must safely transit an intense Earth entry, descent, and landing. This paper focuses on the aerodynamics of the Stardust Sample Return Capsule (SRC) during that entry. The results also have relevance to other proposed sample return missions.The entry of the Stardust SRC at 12.6 km/s will be the fastest Earth entry ever attempted. Its trajectory traverses the hypersonic-rarefied, hypersonic- continuum, supersonic, transonic, and subsonic flow regimes. The passive capsule, once released from its host bus, will rely solely on the predetermined balance between aerodynamic forces and gravity to guide it through those regimes to a parachute landing, within a 75 km ellipse, in the Utah Test Landing Range. Highfidelity aerodynamic knowledge is essential for mission success. The drag coefficient must be accurately described within each flight regime so the cumulative effect of the deceleration results in a landing within the targeted Utah site. In addition, the capsule should possess sufficient aerodynamic stability to minimize angle-of-attack excursions during the severe heating portion of the trajectory. This stability must persist through the transonic and subsonic regimes to maintain a controlled attitude a t parachute deployment.The objective of this paper is to describe the aerodynamics of the Stardust SRC and assess if the requirements cited above are m...

“…The DSMC codes G2 (an earlier form of Bird's DS2V code) and DSMC Analysis Code (DAC) were used by Wilmoth et al [72] before the flight in 1998 to analyze the entry aerodynamics. Focused on aerodynamics, those early Stardust DSMC computations omitted ionization and employed simple thermochemical models.…”

Section: B Analyses Of Earth Entry Flowsmentioning

confidence: 99%

Computation of Hypersonic Flows Using the Direct Simulation Monte Carlo Method

Boyd

2015

The direct simulation Monte Carlo method has evolved over 50 years into a powerful numerical technique for the computation of complex, nonequilibrium gas flows. In this context, "nonequilibrium" means that the velocity distribution function is not in an equilibrium form due to a low number of intermolecular collisions within a fluid element. In hypersonic flow, nonequilibrium conditions occur at high altitude and in regions of flowfields with small length scales. In this paper, the theoretical basis of the direct simulation Monte Carlo technique is discussed. In addition, the methods used in direct simulation Monte Carlo are described for simulation of high-temperature, real gas effects and gas-surface interactions. Several examples of the application of direct simulation Monte Carlo to flows around blunt hypersonic vehicles are presented to illustrate current capabilities. Areas are highlighted where further research on the direct simulation Monte Carlo technique is required. Nomenclature A= surface element of area, m 2 C = particle velocity vector, m∕s e r = specific rotational energy, J∕kg f = probability density function g = relative velocity, m∕s Kn = Knudsen number k = Boltzmann's constant, J∕kg L = characteristic length scale, m m = mass of a particle, kg N = average number of particles in a cell N p = number of particles in a cell N t = number of iterations n = number density, m −3 P c = collision probability r = particle position vector, m T = temperature, K t = time, s V = cell volume, m 3 Δf = rate of change due to collision processes ε act = activation energy, J ε r = rotational energy, J ε tot = total collision energy, J λ = mean free path, m ζ = number of rotational degrees of freedom σ = collision cross section, m 2 τ r = rotational relaxation time, s ω = viscosity temperature exponent