P-279 (1058975), страница 2

Просмтор этого файла доступен только зарегистрированным пользователям. Но у нас супер быстрая регистрация: достаточно только электронной почты!

Текст из файла (страница 2)

Figure 1. MAKS basic version with Orbiter and External Tank

Figure 2. MAKS-T cargo version

In parallel with the works on MAKS project, at NPO MOLNIYA the design studies on the concept of completely reusable Aerospace Plane (ASP) with LRE are conducted at different versions of start:

• horizontal start from a subsonic carrier-plane - ASP-D;

• horizontal start from a hypersonic booster-plane - ASP-H;

• vertical start with help of a reusable winged rocket booster with LRE - ASP-V;

• vertical start from ground single-stage-to-orbit ASP with LRE (of American launcher of SSTO type) - ASP-O;

• horizontal start with the help of ground-based accelerating trolley - ASP-R.

All these RSTS versions have passed the careful workout with results registration in the reports and technical proposals.

Completely reusable ASS with subsonic CP includes in its structure an aerospace plane (ASP-D) as the second stage, which has built-in tanks and LRE. Later on, such ASS was studied during the international research in the frame of AN-225/HOTOL-Interim study with participation of British Aerospace, ANTK Antonov and NPO MOLNIYA firms, and TsAGI and TsIAM institutes. Further development of this ASS version was continued in the project of Multipurpose Aerospace System, where it was considered as the third MAKS version (MAKS-M - see the paper ‘The MAKS Multipurpose Aerospace System’ in this book).

Completely reusable ASS can be created at the later stages on the experience of MAKS-OS and MAKS-Т partially reusable systems. The highest economic indices of such a system are gained in case of parallel maintenance together with the indicated basic MAKS versions.

In the ASP-D system (Fig. 3) the payload bay is located above the upper tanks’ surface, and in AN-225/HOTOL-Interim and MAKS-M systems – in the inter-tank department.

Figure 3. Completely reusable ASP-D system

On the example of ASP-D project with subsonic CP and completely reusable aerospace plane with LRE the analysis of influence of propellant type on main energy-mass launch characteristic was conducted. The versions with oxygen-kerosene engines of RD-120 type, perspective oxygen/hydrogen engines and three-component double-mode engines of RD-701 type were studied. The comparative launch characteristics of these three versions of the main propulsion unit (MPU) at a take-off mass of ASP-D of 250 tons are displayed in Tab. 2 for the reference circle orbit with the height of 200 km and inclination of 51^o.

The advantages of ASP with oxygen-kerosene engines of RD-120 type include rather a small value of structural mass and high level of lift-to-drag ratio. But these advantages can not indemnify the losses of the injected mass connected to low value of oxygen-kerosene LRE specific impulse. At allocated load-lifting ability of CP, the payload mass in this version appeared negative. Only in case of essential improvement of kerosene LRE characteristics, it is possible to expect the increase of payload mass to one ton approximately. At using the subsonic planes as ASS carriers, the kerosene engines can be of interest only in SFV versions having separated units on the active launch leg, for example in the systems made under X-34 (USA) scheme. The low LRE specific impulse in such systems is indemnified by the effect of expendable blocks’ dropping.

As it is visible from Tab. 2, the maximum total injected ASP mass is achieved in the version with perspective oxygen/hydrogen engines with high specific impulse. However, due to big mass of hydrogenous combustible at its low density, the structural mass in this case is maximal, which reduces the payload mass to a low level.

The optimum performances are achieved at using RD-701 engines, which have a high thrust in the first three-component operational mode at the start of launch, and a high specific impulse in the second mode at the end of the ascent, where only hydrogen and oxygen are spent. Owing to decreasing the hydrogen mass as compared to oxygen-hydrogenous LRE the structural ASP mass is reduced, and the gain in a structural mass exceeds the losses in total injected mass.

Similar results of the comparative analysis on LRE of different types were obtained later on by Prof. R. Parkinson from British Aerospace Corporation [2] and by specialist of Pratt and Whitney Corporation R. Joiner [3].

The version of ASP-D space system intended for inter-continental transportation of 52 passengers in sub-orbital ASP with rocket engines launched from AN-225 subsonic plane was also studied. The flight of such system consists of the following main legs. CP take-off with ASP on fuselage and climb, ASP separation from CP, ASP boost with the help of LRE, ASP flight outside of dense atmosphere along an elliptical trajectory, descent in atmosphere to the area of destination, non-powered runway landing. Throttling LRE thrust for holding acceptable g-load equal to 2 was stipulated. For 2.5…3 hours this system allows to transport the passengers into any point of Globe. The maximum duration of the flight leg in weightlessness is 30 min.

AN-225/HOTOL-Interim project close to ASP-D and MAKS-M was studied at first on the basis of the single-stage ASP HOTOL configuration intended for horizontal start from the ground with the help of a combined propulsion unit. The expertise, conducted in NPO MOLNIYA, has shown that at air start from CP, such ASP HOTOL version due to its high structural mass can not reach the orbit even without a payload. It was explained by an oversized wing, designed on conditions of start from the ground, non-optimal layout of tanks and other disadvantages of the parent version of the second stage. After the second phase of team workings it was shown that version ASP with three-component engines and with minimum mass of wing, undercarriage, tanks and other configuration items had optimum performances and was capable to inject into a low-height orbit with inclination of 51^o up to four tons of payload.

ASS with a hypersonic booster-plane and ASP (ASP-H) was studied in NPO MOLNIYA within the framework of KHOLOD theme and during the preparation of technical proposal on completely reusable ASP with different types of start (Fig. 4).

Presence of a group of specialists from DB named after Mikoyan has allowed to conduct the research on a booster-plane with a combined propulsion unit using the experience of works both on supersonic fighter-airplanes and on SPIRAL space system.

Figure 4. ASP-H with hypersonic
booster-plane

ASP-H two-stage system is close by its concept to the known Sanger German project with HYTEX hypersonic aircraft as the first stage.

Launch characteristics of ASP-D versions with different types of main engines Table 2

Recent researches under the Sanger project, as well as on the NASP aerospace plane, are turned off. The versions of reusable launchers with LRE are accepted in the USA and Western Europe as base on the nearest perspective. Apparently, the creation of systems with combined propulsion unit is removed for more remote period because of the high projects cost, necessity of complicated technologies development and high scale of technical risk.

Completely reusable two-stage RSTS of vertical start (ASP-V) studied at NPO MOLNIYA reminds a known system Shuttle-2 (USA) and similar projects of NPO ENERGIA (Fig. 5).

Figure 5. 2-stage RSTS (ASP-V)

Two versions of batch connection of a winged booster of 1-st stage and ASP injected into an orbit are considered: connection by bottom surfaces of two FV (the scheme was conventionally named ‘hands’) and arrangement of the 2-nd stage above the top of booster fuselage (‘biplane’ scheme). In the first version, both flight vehicles had only one fin, like BURAN, in the second version, two fins on wing edges were stipulated. Both versions had rather close characteristics of injection into an orbit.

In considered RSTS, three-component engines of 1-st and 2-nd stages are started at start and operate simultaneously with low-over of fuel from the tanks of the 1-st stage to the engines of the 2-nd stage.

Use of aerodynamic lift effect at the launch trajectory Table 3

At Mach number in the point of separation ~3.5 non-powered booster of the 1-st stage return to the airfield is provided located near the point of start. One of this system disadvantages is the essential non-equilibrium of booster return trajectory, which results in large aerodynamic loads on the construction. Such trajectory is close by stress to a trajectory of emergency return of BURAN, occurring in case of its rapid separation from ENERGIA launcher. Under such circumstances, the task of guaranteed return is complicated by the essential influence of disturbances: wind and deviations of thermodynamic parameters of atmosphere.

Характеристики

Список файлов статьи