Folks,
The below article mentions an orbital X-15 with no internal tanks but toroidal ones on the aft end, sadly no pictures…
But another article by L. Parker Temple III “X-15B - The Spaceplane That Almost Was.” Makes no mention of these but has some small illustrations which I have only recently noticed shows these! They are shown earlier in this thread.
Aviation Week January 18, 1960
Dyna-Soar Design Under Review;
New X-15 Proposed as Substitute
Washington – Complete re-evaluation of the design of Air Force’s Dyna-Soar vehicle is under way, with a ballistic configuration now being weighted against a winged glider. The review was ordered by Joseph Charyk, USAF assistant secretary for research and development, and now includes companies not previously involved in the protracted design studies.
Review, to be completed by Mar. 1, is called Phase Alpha. Assisting the Boeing Airplane Co., vehicle prime contractor, are Bell, Lockheed, General Electric, Avco, McDonnell and Chance Vought. Until now, only winged gliders have been considered. Avco, GE, McDonnell and possibly Lockheed, were believed to have been brought in to introduce the possibility of a ballistic configuration, which might be similar to the Mercury capsule.
Meanwhile, a substitute for Dyna-Soar has been proposed by North American , Inc. It would be a two-man research aircraft with the same external shape and dimensions as the X-15 but with almost entirely new materials and construction methods. It eventually would be boosted into orbit by a two-stage Saturn but initial phases are based on quick availability of hard-ware.
Wing leading edges, fuselage nose and other areas which would encounter high temperatures during re-entry would be made of a beryllium oxide of marble like appearance. This material, which would withstand temperatures up to about 4,900F., would be backed up with a coated graphite capable of withstanding temperatures of about 3,600F. Back of the leading edge, the wing structure would be made of molybdenum alloy, as would cooler portions of fuselage.
Major external innovation in the X-15 aircraft to permit orbital flight is the addition of two doughnut-shaped tanks for rocket engine fuel and oxidiser. These torus tanks will be placed on the aft end of the fuselage, and the opening in their center will be shaped so that they will form an extension to the nozzle of the Reaction Motors XLR-99 engine which is also used on the current X-15. The extension will provide a much greater nozzle expansion ratio and give the engine better performance for its task of providing the final velocity increment to place the aircraft in orbit.
All of the propellants for the main rocket engine would be carried in the external tanks, and the major portion of the internal volume of the orbital X-15 would be devoted to instrumentation. The second crewman in this proposed vehicle sits behind the pilot in what is the instrumentation bay on the current X-15.
One version of the orbital vehicle would have eight XLR-101 rocket engines mounted in the large, blunt trailing edge of the vertical tails to provide braking or retro-thrust during re-entry. Fuel for these rockets would be carried in the fuselage, and the main torus tanks would be dropped as soon as the vehicle achieved an orbit.
Nozzles on these eight retro-engines would face to the rear, and the aircraft would have to be pointed tail-first for them to provide braking thrust and initiate a re-entry maneuver. Maximum heating during such a re-entry would not occur for 10 min. or so after the retro rockets stopped firing, so the aircraft could be turned around with its attitude control jets before aerodynamic loads and heating became high.
It is also planned to carry a small amount of propellant after retro-firing so that these eight rockets could be used briefly during landing to improve the X-15’s characteristics during this flight phase, which is now considered marginal by many engineers. The XLR-101 engines proposed for retro-thrust use have been used successfully for some time as Vernier rockets in the Atlas, Thor and Jupiter missiles.
Useful payload of the orbital X-15 with retro-thrust engines would include 4,000 lb. of instrumentation in the former fuel tank area if the vehicle was sent into a 100 mi. circular orbit. If the retro-engines were discarded and only aerodynamic braking was used during the re-entry, the orbital altitude could be increased to about 200 mi. with the two ton instrument load. Maximum altitude for an elliptical orbit would go up to 1,900 mi. with zero instrumentation weight and using aerodynamic re-entry braking.
Performance figures of the orbital X-15 are subject to change if the Saturn booster undergoes further change. Present figures are based on the use of the eight engine Saturn first stage cluster now under development at Huntsville, Ala., which uses JP-4 and liquid oxygen propellants.
Regards,
Barry