Archive description
A measurement was made of the permanent earth movement in the neighbor hood of the tower caused by the nuclear explosion at trinity. The crat er was apparently formed by a compression phenomenon and was noted to be much shallower than craters formed by ordinary high explosives. Sc aling up existing information on the radius of craters, the tnt equiva lence of the nuclear bomb is given as 10,000 tons to within 50 percent . Observations were made on the damage in the crater region and sugges tions are given as the nature of structures which might be expected to withstand the blast close to the gadget. It is also noted that, despi te previous opinion to the contrary, it is apparently possible to redu ce greatly the volume of earth blown away by the blast by suitably pro tecting the ground.
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was made of the permanent earth movement in the neighborhood explosion at Trinityo The crater was apparently formed by a oompression phenomenon and was noted to be much shallower than craters oraters, the TNT e4uivalenoe of the nuolear bomb is given as ,10,000 tons to within 50 peroento Observations were made on the damage in the crater region and suggestions are gi~en as t~ the nature of structures whioh might be expected to withstand the blast cloae to the gadget o It is also noted that, de,spito previous opinion to the oontrary, it is apparently possible to reduce greatly the . volume of earth by the blast by suitably protecting the ·groundo • f IBEST AVAILABLE COPYBEST AVAILABLE COPY
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Steel atakea two !'oeit long aiad one: inch in dia.m~ter, provided by Jo. Coon, looated at variou& distances from the center ot the tower base along two lllutually The stakes were driven vertically into the ground allowing only the- top half distance& betwo~n .the stakes on ·a given line located 1,009 feet from tho center ot the ' elevations before and a:rter the shot. as well as commen'.t, on the appearance of th• Pictures of the ~takes ( F1g.o 3 Y taken after the ehot indicate the markecl deformation caus_ed by tlie blast. Fig _a 4 1a a goDBral view or the central crater · regiono It ia olear that because of the deformation of the ,atakee and the local irregularity of the ground oaused by the blast. the ia•aurement or an elention 1• arteoted by ignoranoe of the point .on tho stake: ~t whioh to measure. Pre-shot better than a hw tenths of a toot beoauaa of the ked deformation or tha •~~•- ot aer:o to 180 feet. Boring• l aia JJorBEST AVAILABLE COPYBEST AVAILABLE COPY
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crews did. their weeka after the They a pent about three hours in . tho contaminated area\ the highest d~eage recorded was 4Ro · $ome idea or the· extent of the area measured oan be ~ The most marke~ feature of the orater •• its great width, · 1,100 feet, and its 8111&11 depth. about 9-1/2 feet a-t the centero Contrary to expectations, based on the 1.00-ton shot·, which was located on a tower at a scaled elew.tion corresponding to 5000 tons Qf TNT at 100 feet, the orate was olean swept ·and -the ground hard packedo Roads leadine; into the orater from ,north, west and south, were merely depressed with the aw-rounding ground up to a •distanc• ot e.pproxiately 1 feet from ,the. center of the tower baseo The volume ot the orator as oaloulated from Small spheres of !'used earth were found in tho outer part ot the tuaecl region. Since those spheres are or high~r spooifio activity than tho aurroun41,ag tueed soil w can oonolude that they did not originate at the points where they were foundo In thla connection it might also be noted that the radioaoti vi ty . in the very center ot the . crater was small compared· to the activity further from the center 9 From 150 feet outwards, a thin laJU,- Qf. earth waa remove volume ot earth blown away from O to 1000 tee-t t:l"ca th• oater, ae aaloulat
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crater volume1, It would appear then, that the crater was largely formed r than gouging action of the blasto _ -aeaumed that the crater ~8 formed by compression of the ground to 20 feet, ·an increase in density or· ,._,10 peroent would be required Fig1. 6, 7, and 8 are plots of the ground contours be_:foro and atter tho testo two simply give the elevations taken on lines running from I to s . and to be essentially syuiu.trt0e.l 0 . The radiua of the c~liter, as aeon trom tbe air photo, The radius ' of the or&ter can be related, in a rough . empirical way, to the TNT . equivalence of the nuclear explosi vo·~ Scaling up tho radius ot the crater form.oc.i by tho 100-ton shot, and the crater information given in tho Weapons Yanual, we can,, oonclude that to within 50 peroent· the blast performance of the gadget•• equivalent to that of 10,000 tons of TNT pla.oed at. the same height. It, should . be noted that the that the depth is approximately one-quarter of the radiuso Tho horizontal move~en~ ot the gr~und wn:a quite different froa that predloted Y• In the nuclear bomb teat, however, ·i't wae notio~ct.
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1 result , ~eems ree.sonable in that the ground would be expected to be pushed away ffe have as ye.t had no success in interpreting the peculiar earth move100-ton test o The result in the gadget test mi&ht be explained that the ground behaved like a membrane in which the points were cra\m oenter as the membrane ns deformedo An att empt was made to check thi s by observing the positions in the ground of the earth movement atakes i but were too.short to be deforrned in a ms.nner definitive of the mode of deforby the eartho One would expect. for exampleg to find the part of the . stake remaining in the e";round to be bent to-wards the , blast and the part o_f the stake out of the ground be_blown away from the blast (Figo 9). The latter was observed but the former is expected to be slight, and actually was not detected, although it might have been observed at points very close to the center if the stakes had not been blo-tm out of the ground~ It is somewhat difficult to understand vtiy the gr-amd should act like a membrane since Trinity dirt has no apparent tensile strengtho An alternate hypothesis is that surface layers, direot1y under the blast, are compressed and flow outward; but no data are available to check this. conjecture, and since the surface and sub-surface. soil have the same structure (sand). ther0 seams to be no good ' reason for the surface not to move outward with the sub-surface layers 0 . The four tower bases were ori _:;inally placed with their tops tvro feot above· the s~face of -the gr9und, and their bottoms seven feet below the surface of tho the blas~- it was noted that, although the parts of tho bases origiually ~bove grou entire base struoture was pushed down with the ground to a depth of from five to seven feetc The steel work remained intact below the point which was -originally encased in ooncrote. At this poin~ it aa apparent ' _ that the steel had been burnt oft by the exploaicm (see Pigo 2)o It might be usetul to exoavate the stumps.. of tho tower base and en.mi.ne the oondi tion ot the b&ae lett - buried after the blast. This aug&estion is being oonsidered.
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Inspection of the damaged tower base, which was located' at the olosc dis- · tanoe of 100 fen ~om the gadget. leads one to conolude that i t is possible to bui l d underground structures which might be e:xpeoted to withstand demoliti on. by neJ.,\.rby detonation of & 6adget~ This is borne out by the fact that the position or the ba se, which was originally underground, was• despite fi8sures and spoiling of' t he concrete, es·sentie.lly intaot, and further, that thet f our tower be.sea- were sunk b y the bla st approximately the . same amounto It oan be concluded on t he basis of drunage to Trin:ity shelters, that any reasonably strong structure, ioeo, heavy earth· shelter, such as t he 10,000-yd structures at Trinity, would be expected to be safe for human occupants directly under the gadget in case of a comparatively ~istant air burst ( N 2000 feet) suoh e.s used over Japan o On this basis i :t , appears pos's~ble to provide shelter for human beings at a distance of 1500 feet, whi~h can be expoofted to withstand an air bu.rat extremely close to the ground¢ from this i t appears that a shelter could be designed which would make, it possible for human beings to survive within 500 feet of the bombo This ~uess is based on the appearance of the t ower base s which were only 100 feet from :f'rom the 1?ombo This does not apply to bombs buried in the eartho. Sugge~~ions for future tests If in any future tests of riuolear bombs it is decided to mount the bomb on a tower, as at Trinity, the earth mo·vement might be studied more a dequately i f steel stakes three inches in diameter and five feet long were use~ as eartrr movement markers o Geological ~amploa should be takc,n in the vicinity of the shot and te~ted with reapeot against sub~surtaoe installations, markers should be buried at various qistances trca ~e well .to test the conclusions about sheltering human beings in the neighborhood ot the blast by oonstruoting experimental shelters containing teat animals, in case it !s decided to make a. test or another gadget. In. addi t1on. variou• structures aiml&tingBEST AVAILABLE COPYBEST AVAILABLE COPY
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sub-surface tions -xnight well be placed underground at several distanceso In the Trinity test it was found that areas (at greater distances than 150 feet from the gadget) surfaced by macs.du were not broken up by the explosion and drawn into the ri~ing cloud ·~s dusto to be extremely useful o If the bomb were plaood. ou a tpwer about 250 .feet high and the ground were ooated by macadam it seems reasonablo to expoot that the quantity of I.dust raised would be oegligibleoBEST AVAILABLE COPYBEST AVAILABLE COPY
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e,cposed t o the depth incicuted b y th~ coa t h 1.:; of :·us{>d earth _, The distanoe betwecm tho tower base stumps is 28 f t 0 ,8 inohes 0BEST AVAILABLE COPYBEST AVAILABLE COPY
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