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Convair Model 58-9 SST

In the early 1950s, supersonic flight of military "century series" fighter planes became commonplace, and the U.S. Air Force developed the B-58 bomber, which had a supersonic "dash" capability of Mach 2twice the speed of sound. First flown in 1956, this airplane signaled the approach of the era of supersonic cruise flight. The Convair B-58 Hustler was the first airplane capable of sustained supersonic flight and a major contributor to early sonic boom research.

The Convair QRC-182-2 Special Purpose Airplane was a massively modified B-58 Hustler bomber, with relocated engines, wingtip fins and a stretched and widened fuselage. The QRC-182 could serve as a fast recon plane, a supersonic passenger transport for the USAF, even a supersonic high-value cargo plane.

In 1960 Convair proposed a three step program to an operational SST:

  1. An existing B-58 would fly commercial routes, operating from commercial airports, to provide needed information and experience on operational and logistical difficulties. [In fact, something along these lines took place during NASA testing]
  2. The weapon/fuel pod of a B-58 would be replaced with a new "people pod" with five seats. This pod would have the same external contour as the existing pod, but would be fitted out with a pressurized volume, door, windows and air conditioning system. It would be used to determine if there were any adverse effects on passengers flying at supersonic speeds. The pod could be used when getting important personnel to a location was critical and cost wasn't a problem
  3. The construction of an actual suspersonic transport based on the B-58, the first to fly in October 1963.. This commercial Hustler transport derivative featured a fuselage stretched by about 50% to provide seating for 52 passengers. This concept was designated the "Model 58-9".

The Convair 58-9 would be a Mach 2.4 medium-haul airliner , with a range of 2,525 n.m. (2,900 st.m.) with reserves, powered by four P&W J58s of 33,0001b dry thrust each. At a take-off weight of 190,0001b field length required would be 6,500ft, with a lift-off speed of 199kt (229 mph). Balanced landing field length would be 8,700ft at a touchdown speed at 110,420 lb of 148kt (170 mph). It would carry 52 passengers two-abreast in a conventional fuselage in place of the bomber body and with a horizontal tailplane. General configuration would not appear to be particularly unorthodox. The Convair 58-9 was based on work already done by Convair on the B-58C, a proposed development of the bomber based on four J58s.

By Convair's own admission and general agreement among competitors, Mach 2.4 was the wrong speed for a supersonic airliner. According to Aviation Week, "nobody believes that the Convair 58-9 is the optimum supersonic transport, but some do believe that it is the best supersonic transport that could become available in a short-time span . . . Convair is basing its program on the hope that progressive development through the supersonic range, with more complete understanding of the problems all the way along, will be of greater advantage than plunging directly into the Mach 3 speed range." The proposed program did not appear to change the agreed goal of the majority of American entrants now in the running namely a Mach 3 airliner.

The Model 58-9 was acknowledged to be a sub-optimal SST design, but was proposed by Convair as a realistic design that could see flight soon. The Convair program as of November 1960 assumed that the order to go ahead will be given in January 1961. The first four aircraft would be flight-tested by Convair in an 18-month program, starting in October 1963, and the remaining eight aircraft would be evaluated over a period of 15 months by the Federal Aviation Agency, the National Aeronautics and Space Administration, and the Department of Defense, Simulated commercial operations would begin early in 1965, with a MATS squadron "doing the operational shakedown." By October 1965 it is planned that the twelve aircraft in the program would have flown 2,500 hours.

The number of hurdles facing the concept from an engineering and operational standpoint, plus the overall lack of comfort for the passengers, that this was an airplane with nowhere to go. The project never really got off the drawing board.

North American Aviation won the B-70 contract in 1958, but the projected expense of the program and advances in missile technology led President Dwight D. Eisenhower to cancel all but one prototype in 1959. The administration of President John F. Kennedy eventually approved production of two XB-70As. Their main purpose would be to serve as Mach 3 test beds for what was becoming known simply as the SST, for Supersonic Transport. Despite being more than three times heavier than the B-58, the XB-70s bow shock wave eventually proved to be only slightly stronger, reflecting its more tailored aerodynamic design and the benefits of its large size.

The Boeing Airplane Company and Lockheed California Company were selected to assess the feasibility of four NASA-developed SCAT designs on a 3200-nautical-mile SST mission with 125 passengers at a cruise Mach number of 3, as well as the feasibility of one of the designs as an aluminum Mach 2 transport. In addition, they were to evaluate several engine types and levels of propulsion technology. In flying the mission, the sonic boom levels could be no more than 2 pounds per square foot (psf) in climb and no more than 1.5 psf while at cruise conditions. The engine noise would be comparable to present-day subsonic jet aircraft. The results of the NASA SCAT Feasibility Studies were reported on 17-19 September 1963.

On March 5, 1962, the Air Force showed off the long-range speed of the B-58 by flying one from Los Angeles to New York in just over 2 hours at an average pace of 1,215 mph (despite having to slow down for an aerial refueling over Kansas). After another refueling over the Atlantic, the same Hustler outraced the sun (i.e., flew faster than Earths rotation) back to Los Angeles with one more refueling, completing the record-breaking round trip at an average speed of 1,044 mph. An accompanying photo showed one flying over a populated area (presumably at a subsonic speed).

Capable of sustained Mach 2+ speeds, the four-engine, delta-winged Hustler (weighing up to 163,000 pounds) helped demonstrate the feasibility of a supersonic civilian transport. But the B-58s performance revealed at least one troubling omen. Almost wherever it flew supersonic over populated areas, the bomber left sonic boom complaints and claims in its wake. Indeed, on its record-shattering flight of March 1962, flown mostly at an altitude of 50,000 feet (except when coming down to 30,000 feet for refueling), the jet dragged a sonic boom 20 to 40 miles wide back and forth across the countryfrightening residents, breaking windows, cracking plaster, and setting dogs to barking. The B-58 (despite its small numbers) became a symbol for sonic boom complaints.

The Langley Research Center (often referred to as NASA Langley) served as the Agencys team leader for supersonic research. Langleys acoustics specialists conducted NASAs initial sonic boom tests in 1958 and 1959 at the Wallops Island Station on Virginias isolated Delmarva Peninsula. The 1959 test measured shock waves from 26 flights of a Chance Vought F8U-3 (a highly advanced prototype based on the Navys supersonic Crusader fighter) at speeds up to Mach 2 and altitudes up to 60,000 feet. A much larger B-58 from Edwards AFB also made two supersonic passes at 41,000 feet. Boom intensities from these higher altitudes seemed to be tolerable to observers.

In July 1960, NASA and the Air Force conducted Project Little Boom at a bombing range north of Nellis AFB, NV, to measure the effects on structures and people of extremely powerful sonic booms (which the Air Force thought might have some military value). F-104 and F-105 fighters flew slightly over the speed of sound (Mach 1.09 to Mach 1.2) at altitudes down to 50 feet above ground level. In late 1960 and early 1961, NASA and AFFTC followed up on Little Boom with Project Big Boom. B-58 bombers made 16 passes flying Mach 1.5 at altitudes of 30,000 feet to 50,000 feet over arrays of sensors, which measured a maximum overpressure of 2.1 psf. Varying the bombers weight from 82,000 pounds to 120,000 pounds provided the first hard data on how an aircrafts weight and related lift produced higher overpressures than existing theories based on volume alone would indicate.

Testing at Edwards also gathered the first data on booms from very high altitudes. Using an aggressive flight profile, AFFTCs B-58 crew managed to zoom up to 75,000 feet25,000 feet higher than the bombers normal cruising altitude and 15,000 feet over its design limit! The overpressures measured from this high altitude proved stronger than predicted (not a promising result for the planned SST).

A future SST would have to fly over heavily populated areas. Thus, from July 1961 through January 1962, NASA, the FAA, and the Air Force carried out the Community and Structural Response Program at St. Louis, Missouri. In an operation nicknamed Bongo, the Air Force sent B-58 bombers on 76 supersonic training flights over the city at altitudes from 31,000 to 41,000 feet, announcing them as routine SAC radar bomb-scoring missions. Investigators from Scott AFB, Illinois, or for a short time, a NASA-contracted engineering firm, responded to damage claims, finding some possibly legitimate minor damage in about 20 percent of the cases. Repeated interviews with more than 1,000 residents found 90 percent were at least somewhat affected by the booms and about 35 percent were annoyed. Scott AFB (a long distance phone call from St. Louis) received about 3,000 complaints during the test and another 2,000 in response to 74 sonic booms in the following three months. The Air Force eventually approved 825 claims for $58,648. These results served as a warning that repeated sonic booms could indeed pose an issue for SST operations.

To learn more, the FAAs Supersonic Transport Development Office with support from NASA Langley and the USAF (including Tinker AFB) conducted the Oklahoma City Public Reaction Study from February through July 1964. This was a much more intensive and systematic test. In an operation named Bongo II, B-58s, F-101s, F-104s, and F-106s were called upon to deliver sonic booms eight times per day, 7 days a week for 26 weeks. By the end of the test, 73 percent of those surveyed felt that they could live with the number and strength of the booms experienced, but 40 percent believed they caused some structural damage (even though the control houses showed no significant effects), and 27 percent would not accept indefinite booms at the level tested.






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