Air-Launched Launch Vehicle

The use of orbiting vehicles for carrying out various types of missions in space has been the subject of intense research and development activity in the past couple of decades. As is well-known, the current system is a vertical takeoff system in which a transatmospheric shuttle vehicle is mounted piggyback on booster rockets for takeoff and launch. This system has had considerable success and has accomplished a number of missions. However, vertical takeoff systems in general have a number of serious limitations.

The problems associated with vertical takeoff systems include the need for complex, extremely heavy, and expensive ground support equipment in order to accomplish takeoff. Such equipment is necessary, for example, in order to handle the large vertically oriented booster stage and to accomplish the cumbersome process of mounting the orbiter vehicle up onto the booster stage in piggyback fashion. The need for such equipment results in very high launch costs and therefore a high cost for each of the missions performed by the orbit vehicle. In addition, such equipment is provided at only a very few highly specialized ground installations. This severe limitation on the choice of launch sites results in corresponding limitations on flexibility in the system in terms of obtainable orbits and/or times of launching.

Known vertical takeoff systems are also subject to the problem of nonreusability of portions of the booster structure. For example, some structural elements such as fuel tanks, are discarded at orbit altitude and cannot be recovered. The nonrecoverability and consequent total nonreusability of such elements adds significantly to the cost of the system since the total cost of such elements is a recurring cost that is fully experienced each time the orbit vehicle is launched. Other elements of the booster structure are recoverable but are reusable only in a limited sense since they generally require time consuming and expensive refurbishment. Therefore, only part of the cost of such recoverable elements is nonrecurring from launch to launch. The recurring portion of the cost of such recoverable elements further adds to the overall cost of the system.

Other problems associated with vertical takeoff systems include operational limitations that severely restrict the flexibility of such systems. The turn around time, or the time between launches, is quite long because of the need to recover and refurbish the recoverable booster structure and the relatively long time required to make all the preparations necessary for a vertical takeoff. These preparations include readying and positioning the booster stage and mounting the orbiter stage onto the booster stage. In addition to greatly extending turn around time, the long launch preparation time makes it virtually impossible to accomplish a launch on short notice.

The operational limitations also include severe limitations on the orbits that may be obtained from a given launch site without incurring unacceptable penalties. Such penalties include a great loss in time in waiting for the ground track of an orbiting structure that is to be intercepted by the transatmospheric vehicle to pass over the launch site. Efforts to avoid time penalties by providing the transatmospheric vehicle with significant orbit maneuver capabilities lead to the penalty of decreased payload capacity because of the need for the orbitor to carry with it into orbit a significantly increased amount of fuel. Such losses in payload capacity are generally prohibitive, and therefore, maneuvering in orbit is not a practical solution to the problem of providing orbit flexibility. The problem is further aggravated by the fact that orbits of inclination less than the launch latitude cannot be reached at all for most systems without an orbit plane change maneuver.

Launching systems for shuttle craft were disclosed in an article by Curtis Peebles, entitled "Air-Launched Shuttle Concepts", in the April 1983 issue of the Journal of the British Interplanetary Society, Vol. 36, No. 4. Each of the shuttle concepts discussed in the article include a first stage aircraft capable of taking off from a conventional runway and a second stage that goes into orbit after separation. A Soviet system is described as having a high speed separation in the order of Mach 6 or 7. The article also describes a U.S. Air Force proposal having a modified Boeing 747 launch vehicle and a "comparatively low" separation altitude and velocity. With regard to separation velocity, it should be noted that the Jackson et al. patent cited above describes a system in which the separation velocity is about Mach 0.8, and Jackson et al. also mention that separation velocities in the range of Mach 2 to Mach 3.5 would require higher development costs but would yield lower recurring operating costs.

Another launch system using a carrier aircraft to launch a winged booster vehicle while in flight has been proposed by Teledyne Brown Engineering. That system comprises an unmanned spaceplane adapted for horizontal launch from atop a conventional aircraft, such as a Boeing-747. This proposed "piggy-back" technique, however, contemplated starting and testing the spaceplane booster engines while the vehicle is still attached atop the carrier aircraft. Such launching methods are extremely hazardous, substantially limiting wide-scale adoption of this approach. In addition, the system also employs a booster vehicle having wings that remain with the vehicle, which would diminish the payload capacity of the vehicle.

Avoiding the hazards associated with launching from atop a carrier aircraft, certain high-speed research aircraft, e.g., the NASA/North American X-15, have been launched from the underside of carrier aircraft. To date, however, actual underside air launches have been limited to relatively low Mach number, suborbital vehicles, and no vehicle capable of orbital flight has been designed which is suitable for air deployment from a carrier aircraft. The X-15 vehicle attains only about 20% of the energy needed to achieve an orbital trajectory. Furthermore, neither the X-15 nor other aircraft-dropped, rocket-propelled vehicles had two, separable stages, the first providing propulsion as well as lift and aerodynamic control of the trajectory and the second providing propulsion and thrust control of the trajectory. In addition, the reusable configuration of the X-15 vehicle required additional complexity to enable it to survive reentry to the atmosphere and to land on horizontal runways.

Launching a booster vehicle from a carrier aircraft while in flight provides the substantial additional advantage of adding the trajectory contributions of the aircraft's velocity and altitude (kinetic and potential energy) directly to the ascent energy of the booster. These trajectory contributions are unavailable for ground-launched booster vehicles.

Another disadvantage of ground-launched vehicles is that the angle of inclination of the resultant orbit relative to the equator is constrained by the latitude of the launch location and by range considerations which limit the direction of launch (i.e., the launch path must not cross populated areas). One of the advantages of launching from an aircraft in flight is that the velocity vector of the aircraft can be aligned with the plane of the final, desired orbit. This is accomplished by flying the carrier aircraft to the desired launch location (at any desired latitude, usually over ocean areas) and giving it the desired velocity vector prior to drop. The principal advantage of being able to fly to the desired location and latitude and in the direction of the desired orbit is that the booster vehicle does not have to perform an energy-consuming inclination change maneuver to achieve the desired orbital inclination, which is much less efficient than using a carrier aircraft to effect the same maneuver.

Another advantage of air-launching over ground launching is the ability to fly to a launch site at any location having favorable weather conditions at the time of launch. Ground launches typically are restricted to only a few selected sites due to safety and security considerations and the availability of the required launch facilities, which usually are at fixed locations. Thus, air launches are less likely than ground launches to be delayed or cancelled due to unfavorable weather conditions.

The Makeyev Design Bureau proposed developing the Aerokosmos air-launched space transportation system based on the Shtil-3A or RIF-MA launch vehicles. Using II-76 MD, An-124, or An-225 cargo aircraft as launch platforms, the boosters would be carried internally, air-dropped, retarded by parachutes and then ignited. The Shtil-3A would have a LEO payload capacity of more than 600 kg, while the RIF-MA could carry nearly one metric ton (References 229, 232, 241).

A different air-launch concept was proposed by the Raduga Machine Building Design Bureau of Moscow in 1991. A Tu-160 strategic bomber would carry the Burlak missile under its fuselage for release at a high altitude and speed. The original Burlak design envisioned a payload capacity of 700 kg into equatorial orbits, but improvements were made by 1992 increasing the payload capacity to 1,100 kg. Later, the German space agency DARA joined the conceptual studies, and the launcher name was changed to Diana-Burlak (References 242-244).

References

• 229. Aviatsiya i Kosmonavtika, May 1933, pp. 42-44.
• 230. "Makeyev Offers Site", Aviation Week and Space Technology, 26 April 1993, p. 65.
• 231. S. Tutorskaya, Izvestlya, 7 August 1993.
• 232. G. Lomanov, "Americans To Join Missiles' Recycling Project 'Priboi"', Moscow News, 1 October 1993, p. 8.
• 233. S. Golotyuk, Vozdushnyy Transport, September 1993, p. 5.
• 234. J.M. Lenorovitz, "U.S. Entrepreneurs Seek Russian SLBMs", Aviation Week and Space Technology, 19 April 1993, p. 22-23.
• 235. J.M. Lenorovitz, "U.S.-Russian SLBM Venture Plans Initial Test for 1994", Aviation Week and Space Technology, 3 May 1993, p. 60-61.
• 236. "Surf Launcher Uses Recycled Missiles", Aviation Week and Space Technology, 21 June 1993, p. 62.
• 237. "Design Begins on Russian SLBM Conversion Plan", Aviation Week and Space Technology, 2 August 1993, p.25.
• 238. J.M. Lenorovitz, "Russian Maker of SLBMs Seeks Civilian Spin-Offsn, Aviation Week and Space Technology, 9 August 1993, pp. 48-49.
• 239. J.M. Lenorovitz, "Payloads Sought for Former SLBMs", Aviation Week and Space Technology, 4 January 1994, p. 54.
• 240. B. Iannotta, "Two U.S. Firms Set Sights on Sea-Launched Rockets", Space News, 29 November - 5 December 1993, p. 8.
• 241. A. Lomanov, Moskovskiye Novosti, 31 October 1993, p. B12.
• 242. Burlak Aviation Complex, brochure, 1991.
• 243. "Russians Improve Planned Payload of Air-Launched Booster", Aviation Week and Space Technology, 24 August 1992, p. 65.
• 244. J.M. Lenorovitz, "Germany's DARA Studies Burlak Booster", Aviation Week and Space Technology, 27 June 1994, pp. 73-75.
• Adapted from: Europe and Asia in Space 1993-1994, Nicholas Johnson and David Rodvold [Kaman Sciences / Air Force Phillips Laboratory]