Results of simulation and scaled flight tests performed on a rocket-plane at high angles of attack

Abstract

Purpose According to the study of the space flight market, there is a demand for space suborbital flights including commercial tourist flights. However, one of the challenges is to design a mission and a vehicle that could offer flights with relatively low G-loads. The project of the rocket-plane in a strake-wing configuration was undertaken to check if such a design could meet the FAA recommendation for this kind of flight. The project concept assumes that the rocket plane is released from a slowly flying carrier plane, then climbs above 100 kilometers above sea level and returns in a glide flight using a vortex lift generated by the strake-wing configuration. Such a mission has to include a flight transition during the release and return phases which might not be comfortable for passengers. Verification if FAA recommendation is fulfilled during these transition maneuvers was the purpose of this study. Design/methodology/approach The project was focused on the numerical investigation of a possibility to perform transition maneuvers mentioned above in a passenger-friendly way. The numerical simulations of a full-scale rocket-plane were performed using the simulation and dynamic stability analyzer (SDSA) software package. The influence of an elevator deflection change on flight parameters was investigated in two cases: a transition from the steep descent at high angles of attack to the level glide just after rocket-plane release from the carrier and an analogous transition after re-entry to the atmosphere. In particular, G-loads and G-rates were analyzed. Findings As a result, it was found that the values of these parameters satisfied the specific requirements during the separation and transition from a steep descent to gliding. They would be acceptable for an average passenger. Research limitations/implications To verify the modeling approach, a flight test campaign was performed. During the experiment, a rocket-plane scaled model was released from the RC model helicopter. The rocket-plane model was geometrically similar only. Froude scales were not applied because they would cause excessive technical complications. Therefore, a separate simulation of the experiment with the application of the scaled model was performed in the SDSA software package. Results of this simulation appeared to be comparable to flight test results so it can be concluded that results for the full-scale rocket-plane simulation are also realistic. Practical implications It was proven that the rocket-plane in a strake-wing configuration could meet the FAA recommendation concerning G-loads and G rates during suborbital flight. Moreover, it was proven that the SDSA software package could be applied successfully to simulate flight characteristics of airplanes flying at angles of attack not only lower than stall angles but also greater than stall angles. Social implications The application of rocket-planes in a strake-wing configuration could make suborbital tourist flights more popular, thus facilitating the development of manned space flights and contributing to their cost reduction. That is why it was so important to prove that they could meet the FAA recommendation for this kind of service. Originality/value The original design of the rocket plane was analyzed. It is equipped with an optimized strake wing and is controlled with oblique, all moving, wingtip plates. Its post-stall flight characteristics were simulated with the application of the SDSA software package which was previously validated only for angles of attack smaller than stall angle. Therefore, experimental validation was necessary. However, because of excessive technical problems caused by the application of Froude scales it was not possible to perform a conventional test with a dynamically scaled model. Therefore, the geometrically scaled model was built and flight tested. Then a separate simulation of the experiment with the application of this model was performed. Results of this separate simulation were compared with the results of the flight test. This comparison allowed to draw the conclusion on the applicability of the SDSA software for post-stall analyzes and, indirectly, on the applicability of the proposed rocket-plane for tourist suborbital flights. This approach to the experimental verification of numerical simulations is quite unique. Finally, a quite original method of the model launching during flight test experiment was applied.

Technique Used to Perform Rocket-Plane Free-Flight Tests

“…An exemplary set of data recorded during one of the flights is presented in Fig. 18; more results, with the corresponding analysis, can be found in a previous paper [14].…”

“…the probe was connected to the pressure sensor embedded in the eagle tree Universal Serial Bus (USB) Flight Data recorder. the wind tunnel test showed that the measurement of an AoA is possible at speeds >5.8 m/s; the measured characteristics of the five-hole pressure probe are presented in a previous paper [14]. therefore, an alternative technique for measurement of the AoA for very low airspeeds needs to be found.…”

“…this paper focuses on presentation of the flight test campaign preparation and the technique of performing the free-flight tests. the presentation and analysis of the data measured during those free flights can be found elsewhere [14].…”

An investigation into directional characteristics of the rocket plane in a tailless configuration

“…The rocket plane is lifted by the carrier up to 15 km, where the vehicles separate. The study into g-load acting on passengers during the separation process is presented in [14] and concluded that to achieve the lowest possible g-load the separation process should be performed with speed of 100 m/s. But the separation with speed of 155 m/s still gives the g-load that is lower than FAA recommendation and helps to achieve the necessary speed at the end of the climb phase.…”

“…It was assumed that it should satisfy the pitching and yawing moment control for both the low and high Mach numbers. Results of previous research of both the MAS project and the rocket plane are included in [7,8,11,12,13] While the result of numerical simulation and flight camping conducted to test the rocket plane response to control in longitudinal channel is presented in [14].…”