FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1958
1958 - 0227.PDF
FLIGHT, 21 February 1958 TOWARDS ASTRONAUTICS ... boundary layers and wakes. The N.A.C.A. has started experi-ments in these domains, and photographs have shown a plasma jet of ionized air, hotter than the surface of the sun, disintegratinga small aircraft model; and a model of an ion propulsion unit producing thrust by the acceleration of electrically-charged par-ticles in a magnetic field. The principles of magnetohydrodynamics have been applied in the recently announced ZETA experimentfor the controlled fusion reaction. As aerodynamics has extended its scope to these very highMach numbers, so the research tools and facilities have changed. Wind-tunnel designers have manfully kept up with the theoreti-cians and have produced astonishingly different designs for tran- sonic, supersonic and hypersonic flow up to a Mach number ofabout 10. Shock tubes and shock tunnels, ballistic ranges and light gas guns extend the range to beyond M = 20. As the higherMach numbers introduce intensive aerodynamic heating the air- craft structural engineer joins forces with the aerodynamicist inthe provision of heating rigs consuming fabulous quantities of controllable electrical power. Turning now to astronautics, and to some immediate targets[continued the lecturer], I want to concentrate attention on the more immediate future—say, the next ten years. It is clear thatwhatever the ultimate objectives of space-flight will be, a high priority must be first accorded to experiments measuring thephysical, chemical and electrical properties of those regions of space extending a few thousand miles beyond the earth. Thephysicist and astronomer have depended on indirect methods of determining these quantities for several generations, but space-flight now gives the opportunity to make direct measurements. The Russian sputniks have demonstrated that the two majorproblems of placing satellites in orbit have been solved, viz., pro- pulsion to five miles per second and precise guidance. By 400,000 300,000 ALTITUDE (U) 200,000 100,000 1943 \ O 8EGIQ.M OF 19S8 y^^^^\^- k ^IRBM ^'^ I y • M ( GLIDE / ^f / mk ' MISSILE ^xCggjQjj ^^d ^^^^S-T5OT^.C HEATJNC j o 5,000 10,000 15,000 20,000 25,OOOVELOCITY (ft/sec) Fig. 2. The flight regime in which the vehicles listed in the table below operate is frequently referred to as the corridor of continuous flight into outer space. The "corridor" is the unshaded area of this graph. extensions of the present techniques, such as better propellants,lighter structures, miniaturized guidance and control gear and bigger vehicles, larger-payload satellites may be expected, goingto far greater distances than the first two. The Russians have officially announced their intention to fire objects to the surface ofthe moon, a task well within the reach of present technical cap- abilities. They have also spoken of sending transmitting labora-tories to the surface of the moon. This would require substantial extra development, but it would not be surprising if it were donein the next few years. The majority of experimental results can be obtained satisfac-torily by telerecording, so the inability to recover after re-entry will not seriously hamper this work. It is inevitable that physicalexperiments will be succeeded by biological investigations prior to placing a man in and recovering him from a satellite orbit.This has not yet been achieved technically, and does present some difficulties which have yet to be overcome. Many methods forrecoverable re-entry have been proposed and some of these are discussed next. A satellite can be brought down by air drag. Sputnik 1 washighly unsatisfactory from this point of view and physicists, or more important, the occupant of a satellite, will require more-certain knowledge of which week he will return to earth and whether on a foreign mountainside or in a lonely polar sea. There are three means of bringing a satellite out of orbit: (a) byretarding rocket impulse. This is extravagant in weight; (b) by air resistance. The drag can be increased either by variableconical skirt or by steel parachutes; and (c) by air lift. By this 100,000 BO.OOO- S^ F L'N^--'I /MINIUM I SPEED / i/uEVEL FLIGHT ! ^ 60,000 TURBOPROP ,'^H^- SPEED _1< 40,000 • 20,000 • 20 237 3O MACH N° A \ 800 120O 1600 TRUE AIR SPEED (kt) 2OOO Fig. 1. Typical aircraft flight-envelopes, showing advances in per- formance from piston engine to rocket (from the historical review in the first section of Mr. Allen's paper). means there is greater measure of control over the flight path, provided steps are taken to allow for severe heating effects. Some project studies have already been made of devices employ-ing lift during re-entry; some examples are described to indicate likely possibilities.Krafft Ehricke, now of Convair Astronautics, proposed a five- man three-stage orbital glider in which the last stage had highlyswept wing surfaces. It had a very low wing-loading of 11 lb/sq ft, and was estimated to be capable of descending from a satelliteorbit and landing on retractable skids. Weighing about a million pounds, it represents an ambitious project unlikely to be builtduring the next ten years. Dr. Ferri, of New York, prefers a boat-shaped configurationwith highly rounded, swept leading "edges." The payload or crew space is in the lee of the forebody and re-entry is made in a seriesof skips. Heat generation during a pull-up is radiated away during the subsequent path in free space, and by this means the excessiveweight of a heat sink is avoided. Dr. Hilton, of A.W.A., considered the more severe case ofre-entry from an interplanetary path at speeds greater than the orbital value, e.g., seven miles per second. In this case, con-siderable downward lift is required to curve the traj«ctory parallel to the earth. The associated high drag reduces velocity further,eventually to below the orbital value. The full brunt of the aerodynamic heating is taken on the flat pressure face which mustbe cooled or allowed partly to melt away. A near vacuum is formed on the lee side, which reduces heat transfer to the payload. A period of experiment must be expected to elapse before therelative merits of rocket, drag or lift for re-entry from a satellite orbit can be assessed. The best solution may well combine thevirtues of all three. Future High-altitude Aerodynamic Research Aeronautics and astronautics are about to embark on a mostfascinating period of exploration of altitudes and speeds which have only been tentatively evaluated so far. We must be preparedfor radically new shapes to appear. There will be a new emphasis on research and new experimental techniques. There is theballistic missile with crucial or blunt nose re-entering at steep angle, the hypersonic aeroplane with highly swept and roundedleading edges cruising at above 100,000ft, and the hemispherical satellite coming in at low flight path angle to be recovered byparachute. These three representative configurations have quite different flight characteristics, as shown in the table [foot ofthis column]. Experience gained with the re-entry of ballistic missiles will notbe wholly relevant to the hypersonic aircraft or the re-entering satellite, for both the angle of dive and the rate of heating aregreater and the ballistic device does not require lift. The flight regime in which these sort of vehicles operate is now FLIGHT PATHS OF UPPER AIR VEHICLES Class of vehicle IRBM(1,500n.m.) ICBM (5,000 n.m.) Hypersonic glider Re-entry from satellite orbit Experimental vehicle Altitude(ft) 200,000 200,000 120,000 250,000 250.000 Mach No. 15 23 5-10 20 10-25 Flight path angle (d«g) 38 23 near 0 0-10 0-10 Aerodynamic heating effects 800 kW/sq ft 3,000 kW/sq ft 5 kW/sq ft High rates 100-1,000 kW/sq ft High rates 100- 1,000 kW/sq ft Duration (~ 15 sec) (~ 15 sec) (i-2 hr) (2-5 min) (2-3 min)
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
