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Aviation History
1951
1951 - 2187.PDF
56o FLIGHT AIR AT iS C By Capt. L. ARTHUR, D.F.C., F.R.Met.S., A.R.Ae.S. 500 OOO Cu M OF AIR AT I2OO C* ^SEALED) Suggested general arrangement of the jet-ship (length 240ft, maximum diameter 60ft). Operating through an autopilot, the radio equipment would adjust direction, speed and altitude, and could also fuse the war-load. TANDEM JET UNIT (BOOSTER) FUEL SPACE AND (ATOMIC)LOAD AIRFLOW SKIN No I ,-DURAL(OUTER) STEEL- (INNER] SKIN No 2 ALUMINIUM (OUTER) - AIR AT-55'C JjQO. M.P.H.) STEEL^(INNER) MODERN MONTGOLFIER Theoretical Outline for a Jet-heated, Jet-propelled, Hot-air Dirigible Weapon THIS article propounds the concept of a military aircraft,the design of which is so startlingly at variance with con- temporary lines of thought—at least those in commoncurrency—that it arrests the attention. The author's theoretical examination is so sound as to suggest that suchan aircraft could undoubtedly be built and be made to work, but whether it will, in fact, ever be built is quiteanother matter. This would seem to rest chiefly upon the operational philosophy, which is more questionable. PERHAPS the jet airship has already been seen—it wouldnot surprise the writer; but in case there is any doubtabout its practicability, these notes on the subject may bring forth some interesting facts for consideration. Before going further, let it be clearly understood that, un- like the helium dirigible, this airship lends itself to high-speed, high-altitude work. It could carry a bomb-load; it could hover over a threatened country, or move away at high speed. As a "diplomatic" weapon, with atomic bomb-loads, it could hardly be shot down over the country over which it hovered; the only answer would be to evacuate or submit to an awaiting army. It is also a possible checkmate to war as at present envisaged. The hot-air principle is not unknown to aviation historians, and no doubt it is a great pity that the Montgolfiers were without the heat-energy of the Whittle turbojet. By studying the laws of gases, the volume occupied by air heated above standard temperature can be assessed. Thus the displacement theory can be used to show the weight of the displaced air and hence the total lift in pounds — V1=V0 TtPoTo Pi Raising 1,000 cu ft of air to 1,000 deg C (1,832 deg F) with pressure constant at 29.92m Hg (a purely theoretical 2000 o <J<1SOO IOOO 500 50 !OO 15O ZOO 25O 3OO GROSS WEIGHT (ibXIOOOJ Hot-air cell (500,000 cu ft) lift versus temperature. 350 450 pressure condition), it will be found that the new volume'Vj is about 4,400 cu ft. Therefore lift at 1,000 deg C on 1,00c cu ft is 0.076 (4,400)—76 lb at sea-level. The inverse-density law is used to discover the pressure attitude of a lighter-than-air vessel, and in this case the rela- tion has become 0.227. This is equivalent to an altitude of 41,000ft. At this point, 41,000ft, the differential pressure would be zero, so that pressure in the balloon would be 5.283m Hg. Correction for pressures is made to the figures for constant pressure as follows :— 1-29 92 Lift at 4i,oooft=o.O2i75 (4,400x1 ^ =465 lb/1,000 cu ft Lift at sea-level=0.076 x 4,400 (nil press, differential = 334-76 lb = 258 lb Lift/1,000 lb versus Temperature in Envelope_ _ _. ... Lift (lb) DegC 2,O0O I,50O I,OOO 5OO 250 IOO 50 15 v°/v O.I2 0.16 0.23 0.37 0.53 0.78 0.89 1.0 76O 560 46O 175 75 30 12 O Alt (ft)55,000 50,00041,000 30,00020,000 8,0004,000 o In practice, of course, a differential pressure exists'in an envelope until the pressure altitude is attained, and the lift in pounds will remain constant as the differential pressure reduces, up to the altitude selected. The capacity of the ship chosen here is only that of 500,000 cu ft. The dimensions would be : length, 240ft; maximum diameter, 60ft. The highest temperature com- mensurate with technical and metallurgical progress would be 1,000 deg; y to a maximum of 1,500 deg C. At 1,200 deg C the snip would lift a 230,000-lb gross weight to 41,000ft. . For military purposes payload need only be about 20,00010 (9 tons). One or two turbojets of 5,000 lb thrust would resuii in a speed of (a) 250 m.p.h. (single jet), or (ft) 360 m-P-"1- (twin jet) at 50,000ft. bOOOO £ 40.000 p zoooo MSI Lift comparison between normal helium-fill^ ship and jet-heated ship.
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