Approach

This study was performed at a comparative level only. The most relevant class of systems for comparison was aircraft, particularly military fighter aircraft. Most of the information used came from Janes' All The World's Aircraft. [8] These aircraft used jet engines, had considerable speed and altitude capability, and were well understood. Attempts were made to account for the major differences between such aircraft and the Pogo concept. Some comparison was also made to the DC-X[9] and Unmanned Aerial Vehicles.

In order to identify the potential benefits of such a Pogo, three basic questions were asked. First, what might the capabilities be of such a Pogo in terms of performance? Second, what would be the benefit to upper stages given the estimated performance of a Pogo first stage? And third, what would be the costs associated with such a Pogo?

The approach for the question of Pogo performance was to review the performance capabilities of current aircraft. Of particular interest were those which could fly high and fast but would also exhibit relatively low acquisition and operational costs. These capabilities and the aircraft configurations were then used to develop a notional Pogo configuration (see Figs. 1 and 2) and to estimate its performance capabilities.

The approach for the question of upper-stage benefits was to select three Pogo/upper stage configurations (five-engine Pogo/Pegasus, ten-engine Pogo/Taurus, and ten-engine Pogo/notional LOX/LH2 fueled upper stage) and compare the upper stage payload capacities with and without the Pogo. For simplicity and consistency these were all estimated for an LEO delivery.

The approach for the question of costs was to estimate the costs of owning and operating each of the Pogo variations and upper stage vehicles. The Pogo costs were estimated from known costs of components and operations. The engine costs were obtained from contacts at the Wright Laboratories.[c] The costs of development, test, and other components were estimated from this author's experience but were compared to known costs of vehicles, such as the DC-X, for reasonableness. The costs of the upper stages were taken from the open literature directly or comparatively.
[c] Personal communiques with Marvin Stibich, USAF Wright Laboratories, Aeropropulsion and Power Directorate, Wright Patterson AFB, OH

Baseline Vehicles, Five- and Ten-Engine Versions

Two variations (Five- and Ten-Engines) of the Pogo configuration depicted in Figure 1 were used for the basis of study. Both variations used a fabricated aircraft aluminum fuselage with areas for fuel, plumbing, avionics, and other equipment. Both used landing struts similar to those on the DC-X. Much of the avionics and software included on the DC-X were thought to be useable for the Pogo because of their somewhat similar flight profiles. Both Pogos had simple wings that required no movable surfaces because flight control was to be by thrust variation or vectoring only.

Of these Pogo variations, the first had five F-100-PW-200 engines for a total sea level static thrust of 135,000 lb. This was considered sufficient to lift the Pogo and a Pegasus-like vehicle. It also allowed a single-engine-out recovery of the Pogo, possibly with the upper stage attached.

The second Pogo variation had 10 F-100-PW-229 engines for a total sea level static thrust of 290,000 lb. This was considered sufficient to lift the Pogo and Taurus-like or equivalant weight LOX/LH2 upper-stage vehicles.

Pogo Operations. Pogo operations were assumed to be most similar to the DC-X. The upper-stage vehicle would be mounted atop the Pogo via a crane. Checkout of this upper-stage vehicle would be separate from the Pogo operations. The Pogo would be fueled, engines started, and a preflight checkout performed. A flight operations officer would monitor the pre-programmed flight sequence for anomalies. At the scheduled time, the Pogo would lift off, climb to about 8,000 ft (these altitudes and velocities were estimated from this author's experience and not calculated), slowly begin pitching over while maintaining a low angle of attack and gaining lift on the wings. At around 15,000 ft, the Pogo would pass through Mach 1 in level flight. The Pogo would climb to 80,000 ft and Mach 2.5, maintaining a constant Q and small angle of attack. During the climbout, the Pogo would perform any maneuvers needed to achieve the desired position within the launch range. For example, lift-off could be at Edwards AFB, CA, with release of the upper-stage vehicle over the Western Space and Missile Range, offshore from Vandenburg AFB. Once the desired altitude, velocity, and position were achieved, the Pogo would increase its pitch angle to about 30 deg., reduce engines to idle, separate from the upper-stage vehicle, and return to base for a vertical landing. The upper-stage vehicle would start its engine(s) and continue to orbit.

Pogo Maintenance and Support. Pogo maintenance and support were assumed to be similar to current military fighter aircraft between training missions. On-board health monitoring records would be analyzed, a visual inspection performed, and maintenance performed as necessary. Engine maintenance would probably require a special adaptor because of the unusual mounting orientation. The mean time between overhauls for the F-100 engines, as used in the F-15s, is about 2,000 hours, while the Pogo is not expected to exceed 200 hours of operation in its lifetime. Special instructions would have to be available to account for the minor modifications of the engines, such as engine oil gages, and for the uniqueness of the rest of the vehicle. Most of the components, such as avionics and fuel pumps, etc., would be off-the-shelf aircraft parts. Maintenance would be more simple than for a fighter aircraft because of the lack of crew facilities, weapons, complex landing gear, and movable flight controls.

Postulated Future Generations of Pogos

The Pogo variations discussed in this report are intended to achieve the lowest life cycle costs for the systems. These costs include development cost and interest. Also considered is the historically low launch rates. Should the Pogo concept achieve or exceed expectations, it is postulated that higher performing Pogos might become economically feasible. The following is a list of such notional vehicles.

....GENERATION 0: This would be a low-cost demonstrator using a small number of surplus engines to demonstrate the concept only.

....GENERATION 1: This would be the type of vehicle generally discussed in this report. It would use current production jet engines, standard aircraft materials and components, and stay within the performance of current military jet fighter aircraft.

....GENERATION 2: This might use engines specially designed for the mission, possibly with technology developed through the Wright Laboratories Integrated High Performance Turbine Engine Technology (IHPTET) program. This generation Pogo might achieve Mach 4.5 and 100,000 ft, similar to that of the X-7A tested during the 1950s.[d] Some special materials could be required because of the aerodynamic heating.
[d] Personal communique with Andreas Gehrs-Pahl, collector of military missile information, 14 Jun 95

....GENERATION 3: This might incorporate ramjets or other technologies on a large scale. Writings on ramjets[10-11] indicate they have been operated well above Mach 5 and should be viable to the Mach 6 to 8 region. One reference[12] indicates that ramjets could be operated at much higher speeds with very high fuel/air mixtures to keep the engine temperatures low. Extensive use of special materials would probably be required.

....GENERATION 4: This would use engine technologies which were just being studied at the time of this writing. These engines might be combined cycle rocket/air-breathing or supersonic combustion ramjets (scramjets). This generation Pogo might achieve Mach 10 to 15 and altitudes above 160,000 ft.

This Page Last Updated 29 May 97