SPACE "ELEVATOR" - SIMPLE INEXPENSIVE?
Зарубежная фантастика. Книги, фантастические рассказы авторов дальнего зарубежья.
By Vitaly Katayev, Senior researcher, Center of Stability and Non-Linear Dynamics Studies, Blagonravov Institute of Mechanical Engineering, RAS
The list of machinery and eqiupment sent up into space is getting more and more impressive. By their parameters they are far superior to the original carrier rockets which called them up into this world, so to speak, and which will be marking their 50th birthday in the year 2007.
The fruits of the scientific and technological genius, they are, in principle, still at the level of "primitive" flyers - something like butterflies, which are born, natch their progeny-satellites in this case - and die down.
This sad reality could be shrugged of as an unavoidable paradox of progress had it not been for a well-known fact-most of these carrier rockets "derive their origin" from weapons of war. But is this "attachment" really permanent and unavoidable and what can be the role of Russia - this Motherland of cosmonauts - in changing this station?
Articles in this rubric reflect the opinion of the author. - Ed.
Russia's space industry and research are now in a tight corner for some very obvious economic reasons-a plight which, we hope, we shall be able to overcome. But there are certain areas in this general field in which no improvements will be possible if nothing is done to remedy the situation without delay.
Control of the aerospace market and considerable returns therefrom will be under total domination of a country or a financial-industrial group, which is able to offer the most practical, environment-friendly and inexpensive technologies for reaching near-earth orbits, performing some programs there and getting back to earth.
It should be pointed out that a large number of major projects have now been accumulated in various countries for the development of new space launchers. Their implementation is delayed mainly by an inadequately developed conceptual base with missile experts suggesting rockets and aircraft experts insisting on superplanes. And there are also all sorts of combinations, but there is no acceptable consolidating concept. This state of affairs means that the period of linear headway in this field of technology is nearing its end and is likely to be replaced with some major basic changes in the practical aspects and applications of aerospace technology.
It looks, for example, as though we are on the verge of a breakthrough in the development of a convenient and simple "elevator", riding up into orbit and back to earth. The engineering base for translating such a task into reality is available in the main and what is lacking is a commonly acceptable concept of its implementation. So, what is the reason for this uncertainty?
The currently visible path of development (with the other general requirements being met) of space launcher facilities consists in reducing the basic costs of building an appropriate transport system and the operational costs with the aim of bringing down transport or delivery rates to about 100 dollars/kg. This can only be done on the condition of pooling together all of the related progressive achievements in the world-an "integration of disciplines".
The project we have tried to formulate contains practically no points which warrant the name of a "technological revolution". It rests on the already available scientific and engineering capital which has been piled up in the field of space rocket and aircraft technologies. In sum total this backlog is quite enough for launching work on the idea of a space "elevator". On the other hand, we are suggesting some non-traditional design approaches which can, without major technological complications, help us correct the parameters of the proposed space-lift system in the process of its subsequent optimization.
So, what makes our project different from its predecessors?
Some overoptimistic extrapolations of the volumes of freight flows going into space, prepared back in the 1970s for the period up to the year 2000 and with emphasis on military applications, have led to some unjustified spendings on costly programs. Left unsubstantiated to this day, for example, are the economic arguments for the building of the American space Shuttles. The same can be said about the Russian Burans.
This program has proved to be a one-time exercise by all of its basic parameters such as the fuel tanks, engines and control system. And the total cost of that program was in excess of 18 bin dollars.
The main drawback of such multiple reentry vehicles lies in their limited potential in going into circular orbits above 300 to 500 km. In order to switch them into, for example, some higher geostationary orbit (36,000 km) it is necessary to have some additional interorbital "tugs"-a towing rocket, or some engine with a renewable volume of fuel located on the space vehicle directly.
By some other parameters, however, using a multiple space carrier offers a number of advantages. One can prognosticate, for example, that complex and costly space systems, whose value exceeds by far the cost of charter of their launchers, will be developed for switching vehicles from orbit to orbit, refuelling, orbital service and repairs and, finally, for landing. Incidentally, reentry vehicles will help us solve the problem of space garbage-one of the most nagging ones, which remains unresolved.
An alternative to multiple reentry spacecraft has been offered so far by "one-time" ballistic carrier rockets. Their use was justified at the time of bitter military confrontation of states and the development of new strategic rockets which provided the technical base for carriers of space vehicles. Used today as space carriers are former missiles(*) which have since been "demobbed" and spared for use in space programs, but their numbers are limited.
The present state of affairs in dealing with the problem of building a practical space "elevator" is as follows: work on projects like Hotol (England), Sanger-2 (Germany), Ariane- 5- Hermes (France), and H2-Hope (Japan) is practically at a standstill, the same as the Russian projects of the MAKS type (Molnya R&D Center, with the launch from board the AN-225 Mrya transport aircraft), Burlak-Diana (Raduga Design Bureau, with the launch from a reequipped TU-160SK strategic bomber). And it should be stressed that all of these systems are not fully "multiple reentry" craft, most of them being a kind of combinations of some space and aviation components.
Nor can one so far regard as attractive truly multiple space carriers of aircraft type and with horizontal take-off. This concept stems mainly from the possibility to operate them with uniflow jet engines and atmospheric oxygen. In actual fact this complicates in an unjustified measure the scientific and technical problems involved in the making of landing and take-off gear. And the development of an engine of this kind involves huge expenses.
Nor can one find some serious technical justification for a complex vertical landing system of the reentry spacecraft which is being considered by some experts now. To a very large extent this is being regarded as some deliberate misinformation.
Our proposed concept of a space take-off system (STS) has a history of its own. It emerged in the late 1970s-early 1980s as an alternative to the Buran project.
As different from the traditional
* See: V. Utkin et al., "Ballistic Missiles: Peaceful Uses", Science in Russia, No. 5, 2000- Ed.
approach, the emphasis here is not on the power capacity of the spaceship itself, but on making the whole system simpler and less expensive to operate, bringing it down to the level of matching aircraft systems. Naturally enough, some of our suggestions, when viewed from a local energy angle, do not look optimal, such as, for example, the longitudinal arrangement of the stages of the spacecraft ("tandem" type), having jet engines on the stage launched into orbit and tanks with some spare fuel for maneuvers at the atmospheric stage of the flight. But the extra expenses incurred in this way are made up for by the cutting of others. Thus, with the cost of development and manufacture of the take-off complex (of the order of 15 bin dollars) and with each of a fleet of ten spacecraft being "reusable" for about 500 times (preparation and launch into orbit of any of them will cost about 3 min dollars) and the cost of putting into a standard orbit of 1 kg payload (with the total payload of 30,000 kg) will be about 100 dollars. This figure, of course, covers only the basic (depreciation) expenses. And one should add to these the cost of servicing and fuel (0.1 and 0.15 min dollars respectively). But, as the reader can see for himself, this does not practically increase the cost of putting into orbit 1 kg payload.
So, it turns out that in the specific cost of orbiting 1 kg payload there prevail in our case the basic expenses while in the case of the Shuttle and Buran spaceships the operational expenses prevailed. And one more thing. In the cost of one STS carrier launch the share of the fuel amounts to 5 percent only. This covers all of the energy losses which come up from a system optimization we propose.
According to our preliminary assessments of the general layout and the components of the STS "Elevator" system, it looks about as follows.
The system includes: a spacecraft of two manned stages (booster and orbital), and a special ground launcher complex. Their servicing, loading and link-ups are on a horizontal level, so to say The fuelling and take-off take place with the craft being in the vertical position. The stages of the STS spacecraft have similar aerodynamical configurations such as variable wing geometry (with retractable or telescopic elements along the wingspan), systems of control, orientation and stabilization in flight. The horizontal landing velocity of the landing stage on an ordinary runway is 285 km/h (for comparison it is 260 km/h for the TU-154 passenger jet and 330 km/h for the Shuttle). The length of the runway does not exceed 2,500 m.
Using an aerodynamic diagram with controlled front carrier wings makes it possible to apply a broad range of stage alignment depending on the amount of spare fuel and useful payload.
Both of the stages, except for the sustainer liquid-propellant rocket engines, are equipped with jet engines of aircraft type operating on the "main" fuel. These are assembled from unified rocket sections: three on the first stage and on the second one-two plus a cargo one. The rocket block in the power diagram is of the carrier type with its dimensions fitting into the accepted technologies and dimensions. The blocks of the booster and orbital stages have the same unified liquid-propellant rocket engines, but the engine of the orbital stage is also equipped with high-altitude nozzle.
In view of the need to adapt the spacecraft to a range of loads, from zero to maximum values, provisions are made for its incomplete fuelling and for activating at one time not all of the sustainer liquid-propellant rocket engines. The thing is that a power reserve and the diagram of engine placement ensure a symmetrical thrust vector in all cases and also with one of the engines switched off by the on-board "diagnostic" system.
The air jet engines of each stage provide for broad maneuverability at landing and in autonomous flight in the aircraft mode, e.g. for moving the craft to a different airfield. Apart from that the first stage jets are also used at the take-off and in flight at the acceleration stage of the trajectory as an additional booster.
The first stage of the spacecraft is piloted by a crew of two and the second by a two-men or three-men crew. Their functions include keeping check on the automatic systems at take- offs and landings and during overflight in the aircraft mode from airfield to airfield as well as during orbital operations.
Each stage is provided with an autonomous crew rescue system in emergencies: at the booster stage this includes cutting off the pyrocord and separation of the crew cabin and its subsequent landing by parachute, and at the orbital stage-with the help of the commonly used landing module of the Soyuz type.
Each stage has its own landing gear used in the conventional aircraft mode and also during link-up of the first stage with the launching platform when the craft is elevated into a vertical position. And it is also used as a mooring device for two stages during docking in orbit.
The connections between the booster and orbital stages include props located on the first and responder logements, or catches, on the second (and there are also alternative versions of three props).
The layout of the spacecraft of a "tandem" type has been chosen with a view to simplifying the servicing of the separate stages and the craft as a whole. For the sake of comparison a parallel link-up of different stages was considered, which, of course could have improved the thrust-weight parameters of the spacecraft. But, as has been indicated by a detailed analysis, its implementation would require complicated lifting and transport machinery for the assembly, servicing, loading and vertical positioning of the craft on the launchpad. And although during the launching of a "tandem"
spacecraft and at the booster stage the sustainer jet engines of the orbital stage remain idle "passengers" this makes it possible to build them with an optimal high-altitude expansion of the nozzle, which means certain fuel savings for these most expensive jets.
Our choice of fuel for the spacecraft has been based not on the considerations of maximal specific energy effect, or productivity, but on the simplicity of operation, environmental safety and minimal expenses out of all the possible versions. This optimal choice is an oxygen-propane fuel pair or oxygen-liquefied natural gas. The thing is that the latter, cooled down approximately to the temperature of liquid oxygen, can be "packed" into fuel tanks no worse than kerosene, but twice as cheap, and many times cheaper than hydrogen (the prices are respectively 0.01 and 2.5-4.0 dollars/kg), although the energy yield is lower. But it does not require any complicated design steps which are usually required because of the high fluidity of hydrogen and an increased thermal insulation which means it can be used in all the energy systems of engines of all stages of the spacecraft.
The unified sustainer liquid jet engine for different stages with ground nozzle expansion for the first stage and a high-altitude expansion for the second is designed to match the thrust of the order of 250 tons and for an operational regime of some 200 tons.
Now let us take a look at the launching complex. This includes a podium, shelter and gas supply equipment. Their design makes it possible to lay out the infrastructure without exceeding land allocations prescribed for aircraft facilities today.
The podium is used for a horizontal link-up of the stages of the spacecraft, its lifting into a vertical position, system checks, fuelling and, finally, the blast-off. This is, in essence, a steel platform, cooled by inner channels, upon which the tug places the first and the second stages.
For the convenience of all-weather horizontal handling of the stages during their assembly, the placement of the pay load in the freight compartment and other operations, a light hangar, or shed, is provided which can be moved onto the launch pad together with the spacecraft on a rail track.
So, finally, the two stages are on the launch podium. Each bears upon it fiducial marks for the placement of optico-electronic matrix targets for the link-up. The latter are "targeted" with a laser beam during which operation commands are formed for placement corrections of the first stage relative to the mooring points of the launch pad and of the second stage, relative to the first, with the required alignments being done by means of movable pads for stage chassis. Then the fuelling gear on the podium is connected to the fuel tanks of the stages, the seals of all the connections are checked and horizontal checks are conducted of all the other systems of the spaceship.
The vertical positioning of the craft is done by hydraulic lifts with simultaneously taking into account the deformation of the gradually unloaded chassis props of the stages (these corrections are made using readings of the onboard optical "targets" which are later removed).
With the spacecraft in this position, the routine checks are made, including those with crew participation, secondary checks of the sealings of fuelling systems and preparations for rapid fuelling. This, like the subsequent disconnection of fuelling systems, is done in an automatic mode (without crew on board).
At this stage it is only the landing chassis or rack, which links the spacecraft with the podium. At the start of the blast-off these are disconnected and retracted.
When the booster stage spends its fuel, its sustainer jets are cut off. Then it performs braking, separates from the second stage and, using its own hydrogen jets, lands in the manner of a conventional aircraft.
After the separation of stages, the sustainer jets of the orbital stage are activated and keep going until entry into orbit.
For descent from orbit the orbital stage is decelerated by its sustainer jets after which it performs an aerodynamic "gliding" entry into the atmosphere. Incidentally, having its jet engines and a store of fuel sufficient for range and course maneuvers, there is no need for any high-precision descent trajectory to be observed.
An emergency descent of the orbital stage can be used, if need be, by means of activating for a long time its orientation and stabilization jets. And there are also provisions for an emergency autonomous descent and landing of the crew in the nose section of the space stage.
To translate the project into reality it would be necessary to set up a holding-an international design bureau (with offices in various countries) which could collect data on the latest scientific studies and advanced technologies. And setting up of an international student designer pool on the basis of aviation institutes and aerospace universities in various countries could also be an effective step for such an international organization in search for some non-traditional approaches to specific design problems and personnel training.
One can expect that translating this idea into reality, while offering inexpensive international services for delivery into orbit and return to earth of satellite systems and for the conduct of their pre-flight tests and repairs directly in orbit, will ensure the commercial success of the suggested project.
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