Project 7969

The Air Force initiated Project 7969, the manned ballistic rocket research system, in February 1956 with a stated goal of orbiting and recovering a manned space capsule. By the end of 1957, a joint Air Force-NACA team had evaluated at least 10 serious proposals during a conference held at Wright Field on 29-31 January 1958. Avco, Convair, Goodyear, Lockheed, Martin, and McDonnell proposed spherical reentry vehicles or blunt capsules, while Bell, North American, Republic, and Northrop all proposed winged vehicles.234

The North American proposal included a "stripped" X-15 with an empty weight of 9,900 pounds. Cape Canaveral would launch the vehicle on a two-stage booster that allowed a single orbit with an apogee of 400,000 feet and a perigee of 250,000 feet. The launch vehicle consisted of four Navaho boosters. Three were clustered together in the first stage and one acted as the second stage. The XLR99 in the X-15 was the third stage. The X-15 would be equipped with beryllium oxide leading edges and a Rene 41 alloy shingle heat shield, plus a thicker Inconel X hot structure. Due to the low perigee and aerodynamics of the X-15, no retrorocket was required for reentry. The pilot would eject and descend by parachute just before ditching the X-15 in the Gulf of Mexico, with the aircraft being lost. North American expected that it could conduct the first manned orbital flight 30 months after a go-ahead, at a cost of $120 million.-1135

Given the early state of development of the X-15, there was almost no real engineering associated with this proposal. Nevertheless, it was further along than many of the others since researchers already knew that the basic X-15 shape was stable in most flight regimes, and both the airframe and XLR99 were at least under active development.

After the launch of Sputnik 1, Project 7969 was reoriented into the Man In Space Soonest (MISS) project to ensure that a U. S. Air Force pilot would be the first human in outer space. On 27 February 1958, General Curtiss E. LeMay, the Air Force vice chief of staff, was briefed on three alternatives that included the X-15 derivative, speeding up the Dyna-Soar program, and building a simple non-lifting ballistic capsule that could be boosted into low orbit by an existing ICBM – derived booster. LeMay apparently expressed no preference, and although it was a long and complicated process, the result was that a ballistic capsule appeared to offer the best hope of immediate success. This idea formed the basis for Project Mercury after NASA was formed on 1 October 1958 and the first American manned space effort was transferred to the civilian agency.-135

X-15B

Nevertheless, engineers at North American continued to refine their Project 7969 concept. A few days after the Soviet Union orbited Sputnik 1 on 4 October 1957, North American packaged everything into a neat report and Harrison Storms took the idea to Washington. This version used two Navaho boosters clustered together as the 830,000-lbf first stage, a single Navaho booster as the 415,000-lbf second stage, and an X-15B powered by a 75,000-lbf Rocketdyne XLR105 Atlas sustainer engine as the third stage. Unlike the 7969 proposal, this one had a great deal more engineering in it, although it was still very preliminary since North American had not conducted wind-tunnel tests or detailed calculations on heating or aero loads.-137

The X-15B was larger than the basic X-15 and was capable of carrying two pilots. The Inconel X skin was made thicker to withstand the increased reentry heating, and the vehicle had larger propellant tanks to feed the Atlas sustainer engine that replaced the XLR99. However, the shape and many of the internal systems were identical to those of the basic X-15 then under construction. Engineers had already demonstrated the supersonic and subsonic stability of the X – 15 during numerous wind-tunnel tests, and keeping the same shape eliminated the need to repeat many of them.

The flight plan was simple. Eighty seconds after launch from Cape Canaveral, the first stage would drop away and the second stage would fire. At an altitude of about 400,000 feet, the second stage would burn out and the X-15B would continue using its own power. The vehicle would eventually get up to 18,000 mph, enough for three orbits. The pilot would fire the XLR105 at a point that would allow the X-15B to land at Edwards using the reentry profiles already developed for the basic X-15. It was a grand plan, and years ahead of its time. Unfortunately, when Storms got back from Washington he reported that "there were exactly 421" other people who had competing proposals. Eventually the X-15B just quietly faded from sight.138

In the excitement caused by the Soviet launch of Sputnik, North American proposed a heavily modified X-15B as an early orbital vehicle. Although the aerodynamics of the X-15 were well – understood by this time, the X-15B did not have nearly the maneuverability of the Air Force Dyna-Soar while returning from orbit, and in fact, many X-15B proposals had the pilot ejecting over water instead of attempting to land. (North American Aviation)