SUPERSONIC AIRCRAFT

Work on hypersonic aircraft has been in progress for quite some time. Today as many as thirteen countries are at it. According to the science weekly POISK (Search), years ago Russia used to be in the lead. Yet later, for a variety of objective and subjective reasons, she lost this edge. However, she still has a great research potential.

Thus, the Khristianovich Institute of Theoretical and Applied Mechanics (ITAM, Siberian Branch of the Russian Academy of Sciences, Novosibirsk) has been the world's pioneer in obtaining experimental data on mechanisms implicated in laminar* flow stabilization at great velocities, a major problem in present-day aerothermodynamics. Transition from one flow to another has an essential effect on a craft's air resistance**.

Meeting in September of 2010, the RAS presiding body heard a report on aerothermodynamics of the aerospace systems of the future. One of its authors, Acad. Vassily Fomin (ITAM director and deputy head of the RAS Siberian Branch), was interviewed by Olga Kolesova of the POISK weekly, and this is what he said about the prospects.

- It would be nice to fly from Moscow to New York and back aboard a supersonic jet via Novosibirsk and Vladivostok and save oodles of time. At this stage, however, hypersonic aerodynamics is facing problems: for one, smooth performance of the engine, flight control in air flows, adequate heat insulation materials and cooling.

A turboramjet engine (turboram) will be fine at high velocities. Unlike ordinary engines, this one has a supersonic combustion characteristic. For its effective performance it is essential to avoid aerobraking and ensure fuel combustion in a supersonic air flow. An engine like that has been tested at the ITAM Institute, and experimental results are positive anyway.

Supersonic jets flying through the atmosphere are heated up to high temperatures and become as hot as meteorites. The American Shuttle spaceship that went up in flames killing all those on board is a copybook example. It all depends on the skin. What is it to be like--smooth or porous? We at ITAM are pondering over that, too.

Such supersonic jets as TU-144 and Concord were good and reliable machines. Why were they written off? There were both subjective and objective causes. The sound shock, for one. Colliding with particles of the air,пїЅ a supersonicпїЅ craft generates Shockwaves.

* An air flow may be laminar (orderly) or turbulent (disorderly).--Ed.

** See: V. Klimov, D. Gapeyev, "Integrated" Circuit Aircraft", Science in Russia, No. 2, 2008.--Ed.

Reaching the earth surface, a Shockwave causes an instantaneous pressure differential. This is like a thundering gun report. Its intensity depends on many factors, such as altitude, velocity, body mass and atmospheric conditions (air temperature and humidity, wind velocity). The highest impact occurs with the transition from subsonic to supersonic velocities and vice versa--that is when an aircraft overcomes the sound barrier. In some cases the sound impact may be great indeed, causing vibes in people, destroying jerry-built structures and smashing windows in homes.

That is why the Americans banned supersonic flights over their territory. The United States did its utmost to get supersonic jets out of production. Competition was the decisive factor, of course.

ITAM experts are working on the sound shock problems. We are considering several options of bringing the Shockwave down. Other problems related to the optimal dimensions of a jet plane and its configuration are also on the anvil. In testing we are using wind tunnels of our own make. Other research centers, too, lend a hand. Back in the hard 1990s we joined hands with the famous TsAGI center and the Hydrodynamics Institute and built the AT-303 wind tunnel employed in more than 2,700 tests by now. Today we are building an upgraded wind tunnel, AT-303, to replace it.

Other countries--Germany, USA, Australia and Japan, for instance--are turning to us to check and double-check their experiments. We at ITAM have excellent equipment and topnotch experts.

What are the prospects for Russian-made supersonic aircraft? As Vassily Fomin sees it, small jets sitting 25 to 35 will appear soon, their sound impact would be a third or fourth as large as at Concord. The Sukhoi Design Office and ITAM are designing a Su-21 model that would fly at altitudes above 20 km. The Moscow Raduga (Rainbow) design office is also working on similar craft.

ITAM, Vassily Fomin said in conclusion, has a lot of work in its bag. It will check on design calculations, assess experimental results and obtain new data for basic physicochemical mechanics.

O. Kolesova, "So Much There Is to Hypersound", POISK, No. 44, 2010

Prepared by Vassily ALEXANDROV