Yasunori Nagata

Deployment and Flight Test of Inflatable Membrane Aeroshell using Large Scientific Balloon

A flexible aeroshell for atmospheric entry vehicles has attracted attention as an innovative space transportation system because the aerodynamic heating during an atmospheric entry can be reduced dramatically due to its low ballistic coefficient. We have researched and developed a capsule-type vehicle with a flare-type membrane aeroshell sustained by an inflatable torus frame. One of the key technologies is to develop a large and low-mass aeroshell including inflatable structures. As a part of the development, a miniature experimental vehicle was developed and a balloon drop test was carried out in order to acquire the vehicle with inflatable structures in a high altitude and a free flight condition. The diameter, the total mass, and the ballistic coefficient of the experimental vehicle are 1.264m, 3.375kg, and 2.69kg/m 2 , respectively and its aeroshell consists of a thin membrane flare made of nylon and a torus which can be inflated by gas pressure. The inflatable aeroshell was deployed and the experimental vehicle was separated from the balloon at an altitude of 25km. After the separation, the vehicle flied 30 minutes until a splashdown. This balloon test is very successful and fruitful and following results were achieved. 1) Remote deployment system of the inflatable aeroshell by sending a command from a ground station

Reentry Demonstration of Flare-type Membrane Aeroshell for Atmospheric Entry Vehicle using a Sounding Rocket

A flexible aeroshell for atmospheric entry vehicles has attracted attention as an innovative space transportation system because the aerodynamic heating during the atmospheric entry can be reduced dramatically due to its low ballistic coefficient. We carried out wind tunnel tests, numerical simulations and flight demonstrations using balloons, focusing on a capsule-type vehicle with a flare-type membrane aeroshell sustained by an inflatable torus frame. For the next step, a reentry demonstration using a sounding rocket is planned as a important milestone. The experimental vehicle which has a 1.2-meter diameter flare-type thin membrane aeroshell sustained by an inflatable torus is being developed for the reentry demonstration. In the reentry demonstration using a sounding rocket, the experimental vehicle reenters the atmosphere from an altitude of 150 km and experiences a hypersonic free flight where the Mach Number is 4.5 and the moderate aerodynamic heating where the heat flux at a stagnation is about 20kW/m. The flight trajectory, the behavior of the aeroshell and the aerodynamic heating condition will be measured by onboard sensors and a telemetry system during the reentry. The performance of the flexible aeroshell as a decelerator for reentry vehicles can be demonstrated in this flight test and the results and knowledge obtained in ground tests beforehand can be validated using this flight data.

Test flow conditions for the expansion tube experiment

To investigate a hyper velocity flow field characteristics around a vehicle, such as a super-orbital atmospheric re-entry vehicle, the high enthalpy facilities are utilized. The expansion tube is among them. In this paper, the characteristic flow condition generated in the expansion tube was investigated to evaluate the test time period and the test flow condition realized in the expansion tube. For the investigation, the pitot pressure, the static pressure, the shock speed, and the flow field image around the cylindrical pitot pressure probe were measured, and several flow conditions ranging from 5.75 [km/sec] to 11.8 [km/sec] of the final shock speed are utilized. In the temporal pitot pressure history, the secondary pitot pressure jump indicates the contact surface arrival. This fact is also confirmed through observation of the flow field around the cylindrical pitot probe. For the highest flow velocity case, the measured static and pitot pressures after the final shock wave and the contact surface arrival time agrees with the ones estimated with the simple theoretical method assuming equilibrium flow, and the test period estimated with the theoretical method also agrees with the test time period determined experimentally. However, for the medium flow velocity cases, the present simple estimation method must be improved, especially including the effect of the boundary layer development.

Electrodynamic Control of Shock Interactions in a 25 - /55 - Double Cone Model in Hypersonic Flow

The numerical simulation for the magnetic interaction in the hypersonic flow around the double cone model predicts that as a result of the interaction, the shock wave generated by the second cone is primarily affected and is shifted away from the model surface, affecting the separation bubble. Furthermore, because of this interaction, the separation bubble is enhanced. To validate the numerical prediction, we have conducted an experimental investigation by mean of the expansion tube facility which enables us to generate a high speed flow of 12 km/sec. For measurement, the sequential images of the flow around a model were recorded. The experimental result agrees with the numerical prediction at least qualitatively. As a matter of fact, in the experiment, we can observe the effect of the applied magnetic field more clearly than expected. The flow control accomplished by the present magnetic interaction is qualitatively equivalent to the one accomplished by the increase of the half-angle of the second cone which may represent the aerodynamic control surface. In this context, the present magnetic interaction may have a possibility to replace the mechanical aerodynamic control surface.

Development of flare-type inflatable membrane aeroshell for reentry demonstration from LEO

An inflatable decelerator is promising for a next generation atmospheric-entry system, because it can be packed compactly in the launch and cruise phase and it can be deployed to a large aerodynamic device in the atmospheric-entry phase. Our group has researched and developed this technology since 2000, focusing on a flare-type membrane aeroshell sustained by a single inflatable ring, especially. In our activity, the re-entry demonstration using a Japanese S-310 sounding rocket was carried out successfully in 2012. As a next millstone of our research and development, the re-entry demonstration from the low earth orbit is planned utilizing an opportunity for piggy-back satellites. The overview of the planned reentry demonstration is introduced in this paper. There are several important technical issues to overcome in order to realize this demonstration. Two important issues of these is also introduced. First topic is the structural strength tests using a low-speed wind tunnel to understand the structural strength of a large flare-type membrane aeroshell supported by a single inflatable ring. Second topic is an evaluation on the thermal durability of inflatable structures using a newly developed inductively coupled plasma heater.

Influence of Hall Effect on Electrodynamic Flow Control for Weakly Ionized Flow

In the electrodynamic flow control, a weakly-ionized plasma flow behind the strong shock wave is expected to be controlled by the applied magnetic field around a reentry vehicle. Recently it was reported that the flow control is affected not only by the magnetic field intensity but also the magnetic field configuration such as the magnetic field inclination. This report was based on the numerical MHD simulation which neglects the Hall effect. In the real flight condition, however, the Hall effect can not be neglected and may affect the performance of the electrodynamic flow control. In this study, the numerical MHD simulation including the Hall effect was performed to investigate the influence of the Hall effect. It was found that the magnitude of aerodynamic force is affected by the Hall effect. As the Hall parameter is increased, the aerodynamic force (axial force and normal force) is reduced. Simultaneously, a new component of the aerodynamic force normal to both the normal and axial force appears with the Hall effect in the case of the inclined magnetic polar direction against a body axis. The dominant mechanism of these modification was found to be the modification of the electric current field and the Lorentz force field around the vehicle.

Hypersonic Double-Cone Flow with Applied Magnetic Field

The electrodynamic effect on the partially ionized flow around magnetized bodies was numerically investigated. In particular, the double-cone model was considered because, unlike a simple blunt-nosed model, it generates a complex flow including shock-shock and shock-boundary-layer interactions. Such flows are significantly affected by an applied magnetic field. The modification of the flowfield due to the applied magnetic field causes drag force enhancement and/or the mitigation of the aerodynamic heating. This is enhanced with increasing magnetic field intensity. Furthermore, local flow features such as the separation bubble and the local peak heating that appears near the kink point of the double-cone model are significantly affected. The size of the separation bubble increases with increasing magnetic field intensity and is clearly influenced by the configuration of the magnetic field. The local peak heating is reduced with increasing magnetic field intensity, but the effect of the magnetic field confi...

Validation of the scale effect for the electrodynamic interaction of a magnetized body in a weakly-ionized flow

In this study, the interaction of the magnetized axisymmetric blunt body with the hypersonic weakly-ionized flow was experimentally investigated. The magnetic interaction induces the shock layer enhancement and it is theoretically expected that the increase of the shock layer is correlated with the interaction parameter. By using a hypersonic flow generated by a expansion tube wind tunnel, we have examined the shock layer enhancement and its correlation with the interaction parameter. For this purpose, the radiating area in the shock layer was measured by a high-speed photography, and various interaction parameters were attained by altering not only the magnetic field strength but also the initial flow density and the model size. The correlation experimentally observed shows a good agreement with the numerically predicted correlation. Therefore it can be concluded that the correlation experimentally observed shows a correlation with the interaction parameter as theoretically predicted. For the comparison, the direct comparison was made using the numerical prediction of the radiating area.

Effect of Torsion on the Friction Factor of Helical Pipe Flow

Three-dimensional direct numerical simulations of a viscous incompressible fluid flow through a helical pipe with a circular cross section were conducted for three Reynolds numbers, Re (= 80, 300, and 1000), and two nondimensional curvatures, δ (= 0.1 and 0.05), over a wide range of torsion parameters, β (= nondimensional torsion/\(\sqrt{2\delta } \)), from 0.02 to 2.8. Well-developed axially invariant regions were obtained where the friction factors were calculated, in good agreement with the experimental data obtained by Yamamoto et al. [Fluid Dyn. Res. 16, 237 (1995)]. It was found that the friction factor sharply increases as β increases from zero, then decreases after taking a maximum, and finally slowly approaches that of a straight pipe when β tends to infinity. It is interesting that a peak of the friction factor exists in the region 0.2 ≤ β ≤ 0.3 for all the Reynolds numbers and curvatures studied in the present paper, which manifests the importance of the torsion parameter in helical pipe flow.

Experimental study on the magneto-aerodynamic force deflected by magnetic field interaction in a weakly-ionized plasma flow

By an electrodynamic flow control using a magnetic field interaction in a weakly ionized plasma flow, the aerodynamic force acting on hypersonic vehicles could be controlled without any mechanical architecture. The side force is generated on the symmetric body if the magnetic field is inclined against the body axis. The in-plane component of the side force based on the plane defined by the body axis and the magnetic pole is straightforwardly expected to generate because the magnetic field is no longer symmetry, and it was confirmed experimentally. On the other hand, the recent numerical study suggested that the out-plane component of the side force is also generated by the Hall effect even if the configuration such as the geometry and the magnetic field is symmetry. In the present study, the out-plane component of the side force acting on a magnetized model is experimentally measured utilizing the arcjet wind tunnel to verify the generation of it. As a result, it is confirmed that the out-plane force acts on the experimental model when the magnetic field is inclined against the body axis. This experimental result agrees with the numerical simulation.