Project "Town Hall" B-58 Hustler
Minuteman Missile / ASAT / Spy Satellite
Project "Town Hall" detailed plans in 1962 to air-launch a modified Minuteman Missile from beneath a B-58 Hustler supersonic bomber, equipped with either a photoreconnaissance satellite payload (with film reentry bucket) or an antisatellite weapon system to shoot down enemy satellites. The air launched platform allowed them to exactly match the Soviet satellite's flight azimuth (inclination to the equator) making intercept much simpler for the ASAT system.
The B-58 was designed to carry large centerline stores containing weapons, fuel, or other equipment as integral part of the weapon system capability. Space availability is determined by the physical boundaries of the nose gear, main gear, engines, and ground clearance. Ground clearance is the most difficult to define because it must allow for missile loading and ground handling equipment space as well as takeoff and landing attitudes of the airplane under different conditions. Clearance at takeoff and landing was established by requiring 2 degrees margin in airplane attitude above the normal maximum. Normal practice is at a nose-up attitude of 9-12 degrees from the waterline plane and the ground. The pilot's view of the runway is lost at higher angles, providing an excellent reference. On this basis a 14 degree attitude was chosen as a boundary.
The B-58 return component has a dry weight of 58,500 pounds and a fueled weight of 129,500 pounds. The takeoff and landing performance was applicable to all configurations of the B-58 and was based upon flight test. Normal takeoff operations call for use of maximum afterburning power. These data are based upon rotation of the aircraft to approximately 10.5 degrees deck angle (waterline to ground) at 150 knots before attaining liftoff speed. It should be noted that the unstick speeds are selected so as to ensure a one-engine out climb capability of at least 300 fpm. The tire limit speed shown (233 knots TAS) was the maximum allowable presently for repeat operations. Critical field lengths are indicative of field lengths required for operation.
Landing performance was presented for the weights ranging from normal landing to the max allowable weight due to brake energy limit. The approach (flare) speeds were based on an 11 degree deck angle (approx. maximum for adequate runway vision) along a 3 degree glide path. Normal landing touchdown speeds were based on an 11 degree deck angle. Five seconds after touchdown the nose gear is brought in contact with the runway; the drag chute is deployed and full braking applied to stop.
A number of factors were considered, so that it was difficult to specify "maximum" missile weights and sizes. General capabilities are demonstrated by considering a specific family of missiles in which only one parameter is varied, such as shown on the chart on the following page. The Minuteman missile with an arbitrary nose cone was used as the basic vehicle and the overall length and weight varied by changing only the first stage as indicated. The smallest of these missiles was selected as being about the largest in this family which could be accomodated with "minimum" airplane modifications. The second missile represented approximately the largest of the family that can be physically accomodated on the present B-58A, and the largest was the full Minuteman.
The 51,300 pound missile represented the largest vehicle of this type that can be carried by the basic B-58 without making structural mods to the airframe, or unduly restricting operation. Only four basic modificaton weee required: 1) addition of trim compensator to the autopilot, 2) incorporation of the wing heaviness fix (trim), 3) installation of the necessary missile launch computer and equipment, and 4) addition of another attach point between fuselage and missile pylon. The maximum gross weights (structural limits) at takeoff (163,000 pounds) and in flight (207,000 pounds). Full in-flight refueling can be accomplished in this case (182,000 pounds). The cost of these modifications would be approximately $120,000 [$1962], half of which was for the missile pylon.
The 63,600 pound missile was approximately the largest vehicle of this family which can be physically mounted to the B-58 aircraft. Modifications to the airplane were the same as required for the 51,300 pound missile, with the exception of the aft attachment of the missile pylon to the plane. For the heavier missile, it was necessary that this aft attachment be capable of reacting not only to higher vertical and side loads but also a portion of the moment due to lateral inertia loads on the missile. Also, wing spars fore and aft of the attach points must be strengthened in the local area and designed to accomodate new pylon attach fittings. The cost of these mods would be about $180,000 and would require about 3 months, therefore, the changes are minimal. Overall wing and fuselage strength is adequate for the 64,000 pound missile without change to a factor of 1.5.
The 68,000 pound missile was too long for the installation on the basic B-58 airplane; however, versions of the B-58 with increased fuselage length and increased distance between the nose and main gear had been extensively studied. These models had a 60 inch forward fuselage extension, and certain versions had modified tail cones, larger fins, etc. Considerable wind tunnel testing and detail design work was performed on these airplanes, particularly the "B" model. Therefore, a selection of basic airframe mods studied in the past was made to create an airplane compatible with the 68,000 pound missile. Although the 22 inch fuselage extension would be physically adequate to accomodate the missile, it is more desirable to utilize the design work previously accomplished for the 60 inch extension. This extension would be made by disconnecting the fuselage nose at an existing bulkhead and splicing in a new 60 inch section.
Aft of the new sections the fuel tank area would be reworked to properly fair the upper contour. The volume in the extension would be used for additional fuel. To maintain proper airplane balance the present tail cone containing the gun and fire control system would be replaced with a new tail cone containing fuel. Refairing and structural mods to the area forward of the tail cone would not be necessary. An increase in vertical fin area may be required for directional stability because of the fwd fuselage extension. This would be accomplished by increasing the area of the leading edge and tip of the fin without modifying the basic structure. Such a tail has been designed and fabricated in the past in connection with the basic B-58 program. The third crewman, his escape pod and ECM equipment will be removed to improve balance. The cost of these mods would be approx. $1.5 million. About 2/3 of this cost is for increasing the fuselage length. These modifications would require about nine months to complete. In view of the small weight increase permitted over the 63,600 pound missile, this modification was not particularly attractive for the present missile family. However, it should be noted that with these mods, about 40 inches of increased length can be carried above the largest missile in this family.
Hanging a 70,000 pound store on the existing B-58A modifications were the change to the fitting at station 847 to accept vertical and rolling loads. The effect on the various components is quite apparent. The wing showed factors of safety below 1.5; however, this should not be too alarming since by simply reducing the manuever load factor from 2.0 to 1.8, a safety factor of 1.5 can be achieved. It should also be noted that this maneuver reduction only occurs at the extreme gross weight after refueling. This is a common practice in many operational aircraft. In the case of the fuselage, fairly extensive reinforcements are necessary to obtain a safety factor of 1.5. Between stations 470 and 850 it will be necessary to incrase the thickness of the fuselage skin to withstand the increased shears and moments. Although the area covered by this reinforcement appeared large, it was not a difficult job and would not require new tooling.
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