“Blackstar” Orbital Spaceplane System
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White Paper 03 April 2006 THOUGHTS ON THE POSSIBLE EXISTENCE OF THE “BLACKSTAR” ORBITAL SPACEPLANE SYSTEM 1 SPACE IS GO 1200 Ashwood Parkway, Suite 506 | Atlanta, GA | USA 30338 1+770.379.8000 | 1+770.379.8001 [Fax] | www.sei.aero | [email protected] GOALS OF THIS REVIEW The purported reusable, crewed two-stage-to-orbit flight system referred to as “Blackstar” is briefly technically assessed in the context of previous studies and technological developments. Leading features of its “SR-3” first-stage carrier aircraft and its “XOV” upper-stage spaceplane vehicle are commented upon. Several key design problem areas are pointed out, e.g., takeoff/landing gear, transonic acceleration, upper-stage propulsion. Finally, an attempt is made to positively envision the Blackstar vehicle system as being a technically feasible development, an exercise leading to the still unanswered question: did it exist? References: 1. Scott, W.B., Aviation Week & Space Technology, 6 March 2006, pp. 48-53 (three articles) 2. Jenkins, D.R. and Landis, T., North American XB-70A Valkyrie, Specialty Press, 2002 1 SPACE IS GO BACKGROUND The following is a summary of what is known about the Blackstar system based upon an article in the March 2006 issue of Aviation Week & Space Technology and taken from Wikipedia [www.wikipedia.org]. Source: Wikipedia [http://en.wikipedia.org/wiki/Blackstar_(spaceplane)] Blackstar is the reported codename of a secret United States orbital spaceplane system. The possible existence of the Blackstar program was reported in March 2006 by Aviation Week & Space Technology (Aviation Week) magazine; the magazine reported that the program had been underway since at least the early 1990s, and that the impetus for Blackstar was to allow the United States Government to retain orbital reconnaissance capabilities jeopardized following the 1986 Challenger disaster. The article also said that the United States Air Force's Space Command were unaware of Blackstar, suggesting it was operated by an intelligence agency such as the National Reconnaissance Office. Aviation Week speculated that such a spacecraft could also have offensive military capabilities (a concept colloquially known as "The Space Bomber"). The magazine also said that it was likely that Blackstar would be mothballed, although it is unclear whether this is due to cost or failure of the program. Aviation Week describes Blackstar as a two stage to orbit system, comprising a high-speed jet "mothership" aircraft (which Aviation Week referred to as the SR-3). Its description of SR-3 is similar to the North American B-70 Valkyrie Mach 3 strategic bomber and to 2 www.sei.aero patents filed in the 1980s by Boeing. The SR-3 would carry a second, smaller airframe, codenamed the XOV (eXperimental Orbital Vehicle). This rocket-powered spaceplane, with similarities to the X-20 Dyna-Soar project, would be released by its mothership at an altitude of around 100,000 feet. The XOV would then light its rocket motor and could achieve both suborbital and orbital flight; one source quoted by Aviation Week estimates the XOV could reach an orbit of 300 miles above the Earth, depending on payload and mission profile. The XOV would then reenter the atmosphere, fly like a normal aircraft (possibly using aerospike engines, similar to those used by the Lockheed Martin X-33), and would land horizontally on a conventional runway. This combination of jet-powered mothership and a smaller rocket-powered spaceplane resembles the civilian Tier One spaceplane system, but capable of much higher velocities and of thus attaining orbit. 3 SPACE IS GO GENERAL DESCRIPTION The “Blackstar” two-stage to orbit launch vehicle system consists of an “XB-70 like” large airbreathing engine powered supersonic aircraft boost stage, carrying an underslung “boost-glide” fashioned upper stage vehicle1. The boost aircraft is referred to as the SR-3 and the upper stage as a “spaceplane” or an XOV (for experimental orbital vehicle). The SR-3 aircraft features a clipped delta wing with vertical tails at its extremity, and an extended fuselage. Shown as the powerplant is a set of supersonic air intakes, an extended flowpath and a set of either six, or four exhaust ports. The vehicle is described as having a laterally separated pair of flowpaths terminating with two exhaust ports. Given space requirements for the “semi-conformal” housing of the upper stage along the aircraft’s ventral surface, this approach seems appropriate. The XOV upper stage vehicle is shown to be configured as a blended wing-body with its outer wing panels canted slightly downward. A large bluntly terminated aft end is shown to be outfitted with four rectangular engine exhaust ports. Its large stub dorsal vertical fin is said to serve as the structural pylon connection to the boost vehicle. Both stages are implied to be crewed (cockpits with high-speed windscreens are shown). 4 www.sei.aero BACKGROUND OF SIMILAR (OR RELATED) TSTO SYSTEM CONCEPTS Two-stage reusable orbital launch system concepts have been extensively documented since the 1950s beginning with the original USAF-sponsored aerospaceplane study effort, and continuing with the NASA (MSFC-FPO) Reusable orbital Transport (ROT) study of the early 1960s. Following these all-rocket powered concepts, combined airbreathing/rocket systems were developed, the upper stages continuing as all-rocket systems. An early set of examples of these combined-propulsion systems were the Lockheed-designed TSTO HTHL vehicles expressed in the NASA-sponsored mid-1960s study under Contract NAS7-377 led by The Marquardt Corporation. Moving to contemporary times, the German Saenger project espoused a TSTO system with its boost stage powered by a set of hydrogen-fueled turbine/ramjet engines, and its upper stages (both reusable and expendable types) being all-rocket powered. A more recent set of TSTO concepts that used NASA’s revolutionary turbine accelerator (RTA) first- stage engines was developed by Boeing (FAAST) and Lockheed Martin. The Boeing concept staged at a relatively low speed (at RTA termination) requiring a combined airbreathing/rocket powered upper stage. The Lockheed Martin concept, using a ramjet-extended higher staging speed had an all-rocket upper stage, and, in this respect was similar to Saenger. 5 SPACE IS GO COMMENTS ON THE PROJECTED SR-3 BOOST AIRCRAFT By implications of being “XB-70 like” the Blackstar system staging speed would presumably be in accord with that airplane’s Mach 3 top-speed capability. However, since the SR-3 vehicle is, by appearances, not required to sustain a thermally-hostile cruise condition, being strictly an acceleration means, it might be capable of a somewhat higher staging speed which would be advantageous in terms of the post-staging, high delta-V requirements faced by the upper stage in going to orbit. If the SR-3 vehicle was to use the XB-70A’s J-93 class afterburning turbojet engines, which were rated for continuous afterburner-operation at Mach 3, and if these were to be then modified for water injection (and possibly liquid oxygen injection) along the lines of the MIPCC effort, a transient capability to accelerate to, say, Mach 4 – 5 might result. MIPCC stands for mass injection and pre-compression cooling. Experimental investigations of this interesting approach are currently underway. Configurationally, the clipped delta-wing layout with tip-mounted vertical fins would likely negate the unique variable-geometry “drooped” outer wing panels of the XB-70. These were used to gain high-speed compression lift and for lateral-stability augmentation, important steps for improving the aircraft’s cruising-flight performance. Not having this feature in the non-cruise SR-3 might not pose a significant disadvantage, and this would reduce both physical and operational complexity of this machine, vis-à-vis the XB-70A aircraft. 6 www.sei.aero The question arises as to the overall takeoff grow weight (TOGW) of the SR-3/XOV combined-element vehicle. This will be gone into later, but as a starting-point reference, the related characteristics of the XB-70A aircraft can be instructive. The stated maximum weight of this airplane was 540,000 lbm, its rated takeoff and landing weights being somewhat below this figure. It was powered by six General Electric YJ93-GE-3 engines, each providing a maximum sea-level thrust in full afterburner of 28,800 lbf. Based on an allowable TOGW of 520,000 lbm and a total thrust of 172,800 lbf, the overall thrust/weight ratio was 0.33, i.e., thrust was one-third weight. But the SR-3’s engine count might be less than the six engines of the XB-70: “At least four engine exhaust ports are grouped as two well- separated banks, with ports on each side of the aircraft’s centerline”1. Having but four engines would suggest that, assuming that the SR- 3/XOV combination was at least as heavy as the XB-70, higher thrust engines would be needed. The only turbojet engine on record that measurably exceeded the J93 engine’s thrust in the late 1950s was the developmental General Electric supersonic transport engine, the GE-4 afterburning turbojet. This engine was initially rated at 52,600 lbf, but “A later version of the engine achieved 63,200 lbf on 19 September 1968, establishing it as the most powerful jet engine in the world at that time”2. Just as a “thought exercise,” suppose that the GE-4 had been developed to operational status (in fact, the U.S. SST program was to be terminated, as was this engine program). Assuming that the SR-3 aircraft was now to be powered by four GE-4 engines providing a total thrust of 252,800 lbf, 7 SPACE IS GO at the overall thrust/weight ratio of the XB-70 (0.332), the SR-3/XOV TOGW would then be as high as 761,500 lbm.