Aeroheating Measurement of Apollo Shaped Capsule with Boundary Layer Trip in the Free-piston Shock Tunnel HIEST

An aeroheating measurement test campaign of an Apollo capsule model with laminar and turbulent boundary layer was performed in the free-piston shock tunnel HIEST at JAXA Kakuda Space Center. A 250mm-diameter 6.4%-scaled Apollo CM capsule model made of SUS-304 stainless steel was applied in this study. To measure heat flux distribution, the model was equipped with 88 miniature co-axial Chromel-Constantan thermocouples on the heat shield surface of the model. In order to promote boundary layer transition, a boundary layer trip insert with 13 "pizza-box" isolated roughness elements, which have 1.27mm square, were placed at 17mm below of the model geometric center. Three boundary layer trip inserts with roughness height of k=0.3mm, 0.6mm and 0.8mm were used to identify the appropriate height to induce transition. Heat flux records with or without roughness elements were obtained for model angles of attack 28 under stagnation enthalpy between H(sub 0)=3.5MJ/kg to 21MJ/kg and stagnation pressure between P(sub 0)=14MPa to 60MPa. Under the condition above, Reynolds number based on the model diameter was varied from 0.2 to 1.3 million. With roughness elements, boundary layer became fully turbulent less than H(sub 0)=9MJ/kg condition. However, boundary layer was still laminar over H(sub 0)=13MJ/kg condition even with the highest roughness elements. An additional experiment was also performed to correct unexpected heat flux augmentation observed over H(sub 0)=9MJ/kg condition

Spatial variation of surface mass balance and seasonal variation of dust deposition at EGRIP, Greenland

The Tenth Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and Glaciology, Wed. 4 Dec. / Entrance Hall (1st floor) , National Institute of Polar Researc

Measurement of Ultraviolet Radiative Heating Augmentation in HIEST Reflected Shock Tunnel

Radiance measurements in air at enthalpies from 8-20 MJkg have been made over a 250mm diameter flat-faced test article in Japan Aerospace Exploration Agency's HIgh-Enthalpy Shock Tunnel (HIEST). Measurements were made in the ultraviolet region (200-400 nm wavelength) in an attempt to resolve the long-standing discrepancy between theoryand measurements of heat flux over a blunt body; this discrepancy is often attributed toradiation. The spectra obtained indicate the presence of atomic iron vapor in the flowfield.At the highest enthalpies, the radiance is at the blackbody limit. An attempt to model theradiance is made by taking a nominal CFD flowfield without any contamination productsand processing it through a line-by-line radiation simulation tool. Iron vapor is introducedinto the shocked gas ahead of the model and radiation computations are repeated; the molefraction of iron vapor is adjusted to match the data. For the higher enthalpy conditions, theradiance was strongly absorbed and it was necessary to adjust the temperature and NOdensity in the freestream to match the signal below 300 nm. Once the observed spectrawere satisfactorily matched, the radiance to the stagnation point was then computed. It isshown that the impurity radiation is sufficiently large to explain the discrepancy

Raman spectroscopic detection of the T-HgII-T base pair and the ionic characteristics of mercury

Developing applications for metal-mediated base pairs (metallo-base-pair) has recently become a high-priority area in nucleic acid research, and physicochemical analyses are important for designing and fine-tuning molecular devices using metallo-base-pairs. In this study, we characterized the HgII-mediated T-T (T-HgII-T) base pair by Raman spectroscopy, which revealed the unique physical and chemical properties of HgII. A characteristic Raman marker band at 1586 cm−1 was observed and assigned to the C4=O4 stretching mode. We confirmed the assignment by the isotopic shift (18O-labeling at O4) and density functional theory (DFT) calculations. The unusually low wavenumber of the C4=O4 stretching suggested that the bond order of the C4=O4 bond reduced from its canonical value. This reduction of the bond order can be explained if the enolate-like structure (N3=C4-O4−) is involved as a resonance contributor in the thymine ring of the T-HgII-T pair. This resonance includes the N-HgII-bonded state (HgII-N3-C4=O4) and the N-HgII-dissociated state (HgII+ N3=C4-O4−), and the latter contributor reduced the bond order of N-HgII. Consequently, the HgII nucleus in the T-HgII-T pair exhibited a cationic character. Natural bond orbital (NBO) analysis supports the interpretations of the Raman experiments

Observation of hypersonic high-enthalpy boundary layer with gaseous injection

Transpiration cooling at hypersonic high-enthalpy real-gas flow was experimentally studied in the free-piston shock tunnel HIEST. Heat flux distribution on a flat plate of 1000 mm length was measured, which has an injector made of porous material. The material was permeable C/C, through which gaseous Helium was injected to the plate surface. To adjust unit Reynolds number to almost 2E6/m, which is the critical Reynolds number for transition, test free-steam condition was fixed; stagnation enthalpy was 8 MJ/kg and free-stream Pitot pressure was 200 kPa and unit Reynolds number 2E6/m. Changing of plenum chamber pressure, flow rate of gaseous helium as injectant was changed from 0 to 5 g/s. The measurement showed that the injection was effective to reduce surface heat flux downstream of injector, however, excessive injectant flow rate caused early onset of boundary layer transition, which increase higher heat flux rather than that of no-injection

Free-flight force measurement technique in a shock tunnel

A novel force measurement technique has been developed at the impulsive facility HIEST, in which the test model is completely non-restrained for the duration of the test, so it experiences completely free-flight conditions for a period on the order of milliseconds. This technique was demonstrated with a three-component aerodynamic force measurement with a blunted cone of total length 318 mm and a total mass of 22 kg in hypervelocity test flow. A miniature modelonboard data-logger, which was a key technology for this technique, was also developed in order to store the measured data. The data-logger was designed to be small enough to be instrumented in test models, with an overall size of 100 mm x 100 mm x 70 mm, including batteries. Since the logger was designed to measure force and pressure, it includes six piezoelectric amplifiers and four piezoresistive amplifiers, as well as high-speed analogue-digital converters, which digitize the measured data with 16-bit resolution. The logger’s sampling rate and sample size are 500 kHz and 400 ms, respectively. For the autonomous operation, the logger waits for a trigger signal (accelerometer output) and then starts to take measurements with arbitrary adjustable trigger threshold level and pre-trigger delay time. Measured data is stored to static memory for transfer to a PC via a USB interface after a wind tunnel test. To demonstrate the entire measurement system, wind tunnel experiments were conducted in HIEST. In the present wind tunnel test campaign, records of pressure, axial force, nominal force and pitching moment were obtained under conditions of H0 = 4 MJ/kg, P0 = 14 MPa. This demonstrated that the system worked correctly in the short test duration and harsh conditions typical of HIEST. Use of this data-logger allows the elimination of a large-diameter sting, ending concerns about the sting’s interference with the base flow of the model, which could cause serious errors in measurement in wind tunnel tests

Porous Injection Effect on Surface Heat Flux in High-Enthalpy High-Reynolds Number Flow

The experimental study was conducted on transpiration cooling in the free-piston shock tunnel HIEST. Under high-enthalpy and high-Reynolds number conditions, surface heat flux distributions on a flat plate were measured downstream of the C/C porous injector located 140 mm behind the plate leading edge. The test free-stream condition was varied; Stagnation enthalpy was 4 MJ/kg to 14 MJ/kg, the stagnation pressure 14MPa to 50MPa and free-stream Reynolds number was 0.8x10^6/m to 5x10^6/m. Changing the plenum chamber pressure for coolants, the flow-rate of gaseous helium and nitrogen was changed from 0g/s to 5g/s. The effects on surface heat flux of Reynolds number, enthalpy and coolants were discussed