Tu-360 - hypersonic hydrogen bomber
The general dialectic of the development of aviation technology, as well as the desire of the military-political leadership of the countries on both sides of the Iron Curtain to get their hands on yet another absolute weapon, posed for the aviation industry the advanced aviation powers the task of creating aircraft-type aircraft with high hypersonic speeds, corresponding to M = 3-10, capable of flying at altitudes of 30-35 km. Such an aircraft in its technical solutions (both in terms of the power plant and in its design) should have been significantly different from modern aircraft and spacecraft.
In the USSR in the early 1970s, work began on several projects of hypersonic attack aircraft for various purposes and classes (intercontinental strategic, front-line, etc.). The OKB worked out two directions in the GPUS: an attack machine designed for cruising speed corresponding to M = 4 and at cruising speed M = 6 (" 360 "). Several aviation design bureaus of the country and research organizations of the aviation industry were connected to work on this promising topic.
- research and design of a hypersonic long-range aircraft designed for cruising flight speed corresponding to M = 6 - project “260” (Tu-260). It was an aircraft with cruising engines using liquid hydrogen with a flight range of up to 12,000 km at 10 tons of payload;
- research and design of a hypersonic intercontinental aircraft designed for a cruising flight speed corresponding to M = 6, for a given maximum flight range of up to 16,000 km and with a payload of up to 20 tons - project “360” (Tu-360). Cruising altitude 30,000 - 33,000 m. Tupolev, hypersonic.
On the topic “260” and “360”, the OKB prepared several versions of a hypersonic aircraft with a power plant with 4-6 march ramjets and with six accelerating turbojet engines with a thrust of 22,000 kgf each. The calculated specific fuel consumption of the ramjet in cruise mode was 1.04 kg / kg / h. The selected layout and aerodynamic scheme made it possible to obtain design values of quality of 5.2 - 5.5. For accelerating TRDs it was supposed to use kerosene.
In the course of research on hypersonic aircraft, the Design Bureau conducted extensive research on materials and structures operating in conditions of intense aerodynamic heating. It was concluded that some of the most promising are structures with metal external surfaces. The development of such structures required solving a number of problems, the main ones being the search for new structural materials with increased oxidation resistance and increased creep strength, as well as the development of qualitatively new types of multilayer metal structures operating in conditions of high temperature gradients. The main types of such structures that were considered in the Design Bureau for hypersonic aircraft were metal heat shields to reduce heat fluxes to the main power structure, not included in the power structure work and designed for local transverse load; and panels with both structural properties and heat-insulating properties. Multilayer structures made of titanium alloys are one of the most effective in bearing capacity when working under conditions of heating to 250-500 ° C.
In the course of these studies, technologies were developed for producing multilayer titanium panels with truss filler by the SPF / DS method (superplastic molding and diffusion welding), in which, in one operation, the sheaths, filler, workpiece elements were formed from sheet material and they were joined together into a finished one monolithic construction.
Studies have been conducted on the low temperature thermal protection (NTI) of fuel tanks with cryogenic fuel. The most promising was considered thermal protection based on screen-vacuum thermal insulation (EVTI) with a soft sealed shell, compressed by atmospheric pressure for an external STI, or hydrogen pressure for an internal STI. The design of the tank can be performed both from aluminum or titanium alloys, and from composite materials. Design bureaus manufactured model tanks, both with NTI based on polystyrene foam, and with compressed air pressure EVTI. Life tests of these tanks were carried out using liquid nitrogen.
Much attention was paid to the design of cryogenic fuel tanks with a long service life. During their development, special strength standards have been created that provide the necessary tightness during operation.
As part of the work on hypersonic aircraft, the Design Bureau prepared a proposal for a project of a hypersonic passenger aircraft designed for cruising at a speed corresponding to M = 4.5-5 at altitudes of 28 - 32 km. The flight range was determined at 8500 - 10000 km. The number of passengers is 250 - 280 people. The power plant is combined (turbojet engine + ramjet engine), liquefied natural gas was to be used as fuel.
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