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By Gennady MALYSHEV, Dr. Sc. (Technology), Moscow Aviation Institute
Research space vehicles weighing 1 ton and more are on their way out. Coming in their stead are smaller spacecraft with a payload of 50 to 400 kg. They are the trend-setters, so to speak. Now, what is the best way of launching them? We can put them in orbit by conventional methods with the use of heavy booster rockets like "Rokot", "Kosmos" and others. But does it pay? Economically and in efficiency?
Putting an artificial earth satellite into a pre-assigned orbit requires what we call the circular, or orbital velocity equal to 7.8 km/s. This means that the ground-launched carrier (booster) rocket should have a velocity of 9.5 km/s at the start, since the loss of the characteristic velocity in launching (due to gravitational, aerodynamic and thrust losses in the atmosphere) amounts to something like 1.7 km/s.
But there is a way out-air-launched hardware. A plane lifts a carrier rocket and payload to an altitude of 18 - 25 km. And off it goes! Now what do we gain by that? First, minor satellites and rocket planes can be orbited in all directions (azimuths) and in any latitudes. The launching mobility is increased, while the launching control can be effected from a carrier plane's console. The characteristic velocity losses at the start, say, at an altitude of 11 km will be down to 1.17 km/s; and should the "ceiling" be up to 21 km, the loss will be a mere 0.95 km/s, or nearly half of what we have in ground launchings. What you need is this: find an adequate plane and design a system "satellite (payload)/carrier rocket". To begin with, we chose the fighter plane MIG-31 S which has no analogs in the world. This machine can take a load to a distance of 1,500 km, which means it can carry out launchings at any latitude and in any azimuth. The aircraft can be employed as an air-borne launching complex for smaller space rockets with a payload of 100 - 200 kg at an arbitrary tilt. Besides, the MIG-31 S saves three times as much energy as ground launchers do.
We had to invent many things in designing our "satellite/carrier rocket" system. We sorted out something like twenty variants before designing what we were after; and we did it in two modifications, the two- and three-stage systems which we dubbed Mikron. They look very much alike, especially if viewed full face-just like three fancy cigars packed tight, with two fins (stabilizers) in the afterbody.
The two outer rockets make up the first stage of the Mikron setup propelled by hybrid-type engines operating on liquid oxidant and solid fuel at a relatively low pressure. Their upper compartments are filled with a liquid which, fed into the combustion chamber under pressure (unaided by a turbo-pump), interacts with the solid component. The engine is started with the activation of the ignition system.
But this is not the main thing. There is also such a thing as the specific thrust (impulse), that is the ratio of thrust to fuel consumption per second: the higher this ratio, the more efficient the system. Now if with ground-launched rockets this index is within 300 to 330 s, in air launchings it is up to 360 s. In addition, our engine allows flexible control - it can be on and off many times, and the thrust can be increased or decreased, or as we say, it can be forced or throttled. And what really makes our Mikron system unique is that the spent first stage is not cast off at random (here are some of the parameters: for the two-stage version, this is 180 s/8 tons, and for the three-stage one, 123 s/8 tons). Aided by a steerable parachute operating in an automatic mode or under an air pilot's control, the first stage is landed in a designated area. Then the second stage (our middle "cigar") is activated, it is on for 170 or 124 seconds (depending on whether we have two or three stages), but in either case it develops a thrust of 4 tons. If Mikron has three stages, the third stage comes next (114 s/4 tons). The mass of an orbited satellite will be 100 kg (two-stage carrier) and 300 kg (three-stage carrier) respectively; the total weight of the Mikron system is about 6.5 tons (and it is 20 tons for ground launchings). The initial velocity of a carrier rocket launched at an altitude of 18 - 25 km is in a range of 680 - 750 m/s.
All these characteristics make Mikron without peer in the world, for the next ten or fifteen years anyway. Building the system to our design will take less than two years. And Mikron may find applications other than launching spacecraft.
In 1998 the X-PRIZE foundation of the United States announced an international competition for a sub-spaceship of research, sporting and tourist-travel designation; our Institute took part too. We designed an ARS (Aerospace Rally System) rocket plane, a universal multipurpose machine for hands-on suborbital research.
Outline of the MIKRON carrier: A -three stages: 1 -first stage; 2 -second stage; 3 -third stage; 4 -payload; В -two stages: 1 -first stage; 2 -second stage; 3 - payload.
This rocket plane can be employed in a variety of fields. First, for research of processes occurring in the upper layers of the atmosphere (up to 130 km) and in weightlessness (for as long as 3 min); second, for training space crews; third, in developing the techniques of supersonic flights, speed reduction prior to landing and during landing proper; fourth, for building regional systems of remote sounding of the earth. And last, our plane is "adapted" to aerospace sports (rallies) and tourism, and to high-altitude displays of illumination and advertising for an audience of millions.
Like Mikron, the ARS rocket plane is carried aloft by the MIG-31 S which, at prescribed altitude, is sent into a steep upward trajectory, a well-nigh vertical one. That's when the spacecraft is started: the on-board engine speeds it up to 1,300 m/s, and it zooms as high as 130 km. Then the ARS craft descends into the lower layers of the atmosphere, braving thereby intensive heating and overloads. It makes a landing approach and soft-lands on a regular airfield.
We offer yet another novelty. Say, if the engine is on for 32 seconds only and takes the vehicle to an altitude of 50 km, the subsequent maneuvers (ascent to 130 km altitude and return to earth) will occur through inertia. Our rocket plane has no power devices for flight correction, and it has no canonical flight control system either.
To make all that possible, we found a cute engineering solution. The engine is supported by a set of ball bearings; after working for a prescribed period, it starts rotating and creates a gyroscopic moment that offsets various perturbations of the plane and ensures its flight stability at steady orientation. This rotation should continue until the apparatus descends to an altitude of 50 km, and then it stops; thereupon the ARS plane flies like a glider on account of aerodynamic forces. Here a cosmonaut directs its flight by hand controls. Should the flight proceed in an automatic mode, with the rocket plane being within radio visibility for the carrier aircraft, this job is done by its pilot.
The ARS crew consists of three men: air pilot, flight engineer and navigator. Here are the basic technical characteristics: the get-away speed upon detachment from the carrier craft is 680 - 750 m/s (it is 1,300 m/s on a speed-up stretch); the independent flight time, 25 min; the launching mass, 1,700 kg. The apparatus is quite compact: wing span, 3.7 m; length, 5.7 m; and its height is only 1 meter. The rocket plane can fly in two modes-in the standard mode, with the engine on, and in the training mode, with the engine off. This mode is used in the psychological and physical training of crews learning the ropes of aerodynamic flight control, landing on an airfield runway and parachute descent. In this case the maximum flight altitude is not above 40 km.
Our rocket plane can become the best vehicle for air-launched piloted spacecraft and for hands-on problem solving. It is to be equipped with GLONAS, the Global Navigation System, and with reliable onboard communications. It will be carrying a complex of research instruments, e.g. optical-fiber hardware for the remote sounding of the earth, outfit for optical effects in advertising, among other things.
A single ARS model will be able to perform no less than 200 flights. What with the carrier aircraft and a minimum of technical servicing, the rocket plane will bring down the standard cost of mass unit orbiting to 2 - 3 percent. The designers seek to make the work of the entire system as safe as possible, and they plan to deploy a stand-by flight control and monitoring service on the ground. The onboard systems will be equipped with duplicate facilities at each of the flight stages.
An air pilot or cosmonaut will be able to choose among the flight modes so as to control the active speed-up as well as the altitude and time of the ballistic stretch of the flight (that is between the switch-off of the engine and the arrest of its rotation). The flyer will also be free to determine the overload and heat regimes of movement in the dense layers of the atmosphere, supersonic velocities, deceleration regimes before landing and accuracy of landing.
In a nutshell, the ARS plane will be equipped with the most up-to-date hardware, including life support systems for the crews (seats and suits to minimize overloads, helmets, ventilation devices). The cockpit pressurization equipment will make it possible to regulate the heat regime and gas composition on board.
The ARS system thus holds good promise for suborbital aerospace projects. Incorporated in it are the latest achievements in science and engineering, such as hybrid engines, wing parachutes, and GLONAS for control and navigation. And if we add the possibilities of a carrier craft pilot as an operator who is in charge of the rocket plane's launching, ballistic flight and landing, we get an absolutely novel orbital system capable of discharging most diverse functions-from studying the dynamics of the upper layers of the atmosphere to on-line monitoring and deliveries of goods in critical situations to districts difficult of access.
The above range of problems is of paramount importance. Working on related projects are teams of dedicated researchers and engineers, each group involved with a particular area. Thus the very idea is conceptualized by our Aviation Institute and the International Research Center of Payloads (at Mytishchi near Moscow). The life support system and the instruction program for space-minded sportsmen is tackled by the State Research Institute of Tests and War Medicine. The aerodynamics part of the job is done at the Central Aerohydrodynamic Institute named after Nikolai Zhukov- sky. The Artyom Mikoyan Design
Office, adapting Mikrom to a carrier aircraft, has developed a program of tests. The Research Laboratory of the Russian Defense Sporting-and-Technical Society is designing a system of navigation control and telemetry. The engine, which is one of the basic components of the system, is the brainchild of the Federal Amalgamated Enterprise, the Mstislav Keldysh Center. And last, the Research Institute of Parachute Making is involved with the manufacture and tests of the wing parachute. Cosmonauts V. Janibekov and I. Volk have helped us a good deal in conceptualizing the system's idea.
This cooperative project will make it possible to cut the estimated costs by nearly a third. The Mikron microcarrier and the ARS system are akin in many ways. Both offer certain operational advantages. For one, they need no gantry scaffolds for pre-launch fueling. The weight and designation of a payload may be varied depending on the coordinates of ground-launched craft, and the altitude and velocity of air- launched vehicles. And what is very important, aerospace vehicles can be carried aloft from low latitudes in the eastern direction. So we can nearly halve the weight of a satellite put into an equatorial orbit.
Considering the relatively low cost of our project, it might be possible to launch a cluster of interacting satellites by a group of carrier aircraft.
The Mikron and ARS research and commercial projects are protected by Russian Federation patents. Both incorporate Russian know-how which, if assimilated, will reinforce our aerospace capability.
Interviewed by Arkady MALTSEV
Illustrations supplied by the author.
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