Gun-Launched Probes Ballistic Research Laboratories 0V6P Bamos Aberdeen Proving Ground, Md
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gun-launched probes Ballistic Research Laboratories 0V6P BaMOS Aberdeen Proving Ground, Md. and Gerald V. Bull Space Research Institute, Inc. Northfield, Vt. Abstract 90 km were obtained by means of chemical releases. The use of 5- and 16-inch guns for vertical soundings Early in 1965, the altitude performance of the 16-inch over Barbados is described. Five-inch gun soundings gun was increased from 108 km to 144 km by the addi- have obtained numerous measurements of winds up to tion of a 50 ft long muzzle extension (Fig. 2). With 60 km and have made a few temperature measurements this extension, the gun is 119 ft long and weighs 200 with the development of appropriate sensors. Projectiles tons. By means of an improved ignition system and a launched from the 16-inch gun have made 67 measure- modified M-8 propellant, an identical gun at Yuma ments of winds above 85 km and these results have been Proving Ground, Arizona, has reached 180 km (Murphy correlated with ground based radio frequency mea- and Bull, 1966, 1967). surements to increase our understanding of Sporadic-E The Barbados gun work was initiated by McGill layers. University with the aid of a small U. S. Army contract which allowed the supply of a large quantity of surplus 1. Introduction U. S. equipment including the guns themselves. Addi- In the summer of 1962, the U. S. Army landing ship, tional financial support came from the Army during the the Lt. Col. John D. Page, moved through a hole blasted preliminary work up to July 1964. At this time, a three in the reef at Foul Bay on the Southeast coast of Bar- year joint U. S.-Canadian program called HARP-McGill bados and beached itself high on the sand. Two 140 was established. With the conclusion of this program, ton 16-inch gun barrels with associated mount parts budgetary pressures forced the Army to terminate its were unloaded and moved over land in flat cars on support and McGill University has withdrawn from temporary track two miles to a plateau 70 ft beneath the work. A nonprofit corporation, Space Research In- the East end of the jet runway at Seawell Airport stitute, Inc., has been set up under the control of Nor- (Fig. 1). In January 1963, first proof flights were made wich University and the Army has transferred most of by projectiles from this 16-inch gun and the island of its equipment to this company. The Barbados range as Barbados became the site of a new operational range well as an engineering test site at Highwater, Quebec, for scientific soundings. are being operated by this company (Bull, 1968). During 1963 and 1964, a number of successful firings of the 185 lb finned projectiles called Martlet 2's were made and first measurements of nighttime winds above Fio. 1. Barbados launch site. FIG. 2. Barbados 16-inch and 5-inch guns. 640 Vol. 49, No. 6, June 1968 Unauthenticated | Downloaded 10/05/21 07:08 PM UTC Bulletin American Meteorological Society In this paper, some of the more interesting scientific and 13 successful temperature measuring flights. In results obtained from probes fired from the Barbados the period January 1966 to July 1967, 98 firings of 16-inch gun and its associated 5-inch gun, which was the Barbados five-inch gun were made with 60 success- installed in January 1966, will be presented. Before ful wind measurements. Although some of the nondata- considering this work, we should give the advantages of gathering flights were caused by radar malfunctions, a gun probe system in comparison with the more con- most of these unsuccessful flights were due to a faulty ventional sounding rocket approach. These can be sum- ejection system which has been modified. All of these marized by the two words, economy and accuracy. The data have been published in the appropriate MRN economy of this method is based on the consideration Data Report. of the gun barrel as a reusable first stage booster. The The wind sensor used in these flights was an alu- accuracy can be expressed as a 2 <? impact circle of minized two-meter square parachute with a 280 gm three miles radius for the 16-inch gun and one mile weight. This was packed in a segmented steel can in radius for the 5-inch gun. This accuracy is illustrated the forward compartment of the projectile. A 120 sec- by the placement of the launch site at the end of a jet ond pyrotechnic fuse initiated by the gun launch ac- runway on one of the most densely populated islands celeration was used to ignite a 3 gm ejection charge in the world (Cox, 1967). of black powder. Although the MPS-19 radar would lose skin track of the projectile at 100-110 seconds, it 2. Winds and temperatures: 25-55 km could quickly acquire the parachute after ejection and Winds and temperatures in this altitude range are track it during its descent to measure the wind profile. the usual measurements of the small meteorological In Fig. 3, the mean profiles for 10 flights in February rockets and are published by ESSA in the monthly 1966 are plotted. The numbers on the right indicate Data Reports * of Meteorological Rocket Network Fir- the number of flights used in each 5 kilometer section. ings (MRN, 1965). The five-inch smoothbore gun can Thus, these mean profiles are probably fairly good for place a 11 kg finned projectile at altitudes up to 80 km although the usual payloads launched are only ef- fective below 65 km. In addition to the five-inch gun at Barbados (Boyer, 1966), five-inch guns are located at Wallops Island, Va.; White Sands Missile Range, N. Mex.; Fort Greely, Alaska; Highwater, Quebec; and Yuma Proving Ground, Ariz. As of 1 January 1968, these guns have made 221 successful wind measuring flights * $36.00 a year from the U. S. Government Printing Office. FIG. 4. Ambient air temperature measured by parachute supported 250 MHz telemeter with 10 mil bead thermistor. FIG. 3. Average winds for February 1966 measured by alu- A segment of the mean tropical atmosphere (Jordan, 1958) minized parachutes ejected from 5-inch projectiles is shown above and below the tropopause. 641 Unauthenticated | Downloaded 10/05/21 07:08 PM UTC Vol. 49, No. 6, June 1968 the interval 20-55 km. We see that the winds in this During a firing series, simultaneous measurements of interval are predominately easterlies with a maximum the ionosphere are made by a C-4 ionosonde located near 42 km. An interesting feature of this profile is the near the gun site and correlations between the loca- direction reversal to westerlies above 50 km. These tion of Sporadic E layers and the observed winds are qualitative features of the Barbados (13N) profiles are sought (Wright et al., 1967). A spaced array of receivers also seen at Panama Canal Zone (7N) and at Antiqua is also located near the ionosonde to measure move- (17N). ment of irregularities in the E-layer by comparison of Although the wind sensors are passive and quite re- the arrival time of signals at the different receivers. sistant to the large accelerations associated with gun These ionospheric drifts are compared with the neutral launch, temperature sensors are much more delicate wind profiles to improve our use of the radio frequency and usually require an operating telemetry system. sounding techniques (Wright et al., 1966). Finally, spec- Telemetry transmitters for 250 MHz as well as the me- trographs of twilight trails have been taken to corre- teorological frequency of 1680 MHz have been devel- late spectrum intensity at various wavelengths with oped to withstand gun acceleration as high as 50,000 g's height above ground, depression of the Sun below the and a small number of successful flights with a 10 mil horizon, and time after the initial release of the chemi- bead thermistor have been made (Mermagen et al cal (Millman, 1966). 1966). A temperature telemeter unit has only recently In Fig. 5, a sample wind profile is shown together reached an acceptable level of reliability and an addi- with the location of two Sporadic E layers which were tional number of flights are required to validate this present at the time of this measurement. The coinci- reliability. These telemeters weigh about 260 gm and dence of the Sporadic E layers with the maximum shear are attached to the two-meter parachutes replacing the of the zonal wind should be noted since this is a pre- usual metal weights. Most flights have been made with diction of a simplified wind shear model for the pro- the 250 MHz unit, so increased developmental effort duction of a Sporadic E layer. The high amplitude is being made on the 1680 MHz unit as well as on fluctuations of wind components with height is also the successful gun-launch of the more sophisticated characteristic of ionospheric winds. thin film resistors. In Fig. 4, temperature profiles for three successful flights over Barbados during the month of June 1967 are given. Although ejection occurred above 55 km for all flights, the bead thermistors were initially at 25C and required as much as 10 km of fall to yield good values of the ambient air temperature. The flight on 19 June suffered from RF interference from some unknown source and only partial data was obtained. The flights reflect the low temperatures of the tropical tropopause (Jordan, 1958). 3. Ionospheric winds The basic scientific measurements made by projectiles launched from the 16-inch gun were wind profiles be- tween 85 and 140 km.