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Space Systems Design Laboratory (SSDL)

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Author: McCormick, David Jeremy × Start date: 1997 × End date: 1999 ×

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Hyperion: An SSTO Vision Vehicle Concept Utilizing Rocket-Based Combined Cycle Propulsion

1999-11 , Olds, John R. , Bradford, John Edward , Charania, Ashraf , Ledsinger, Laura Anne , McCormick, David Jeremy , Sorensen, Kirk

This paper reports the findings of a conceptual launch vehicle design study performed by members of the Space Systems Design Laboratory at Georgia Tech. Hyperion is a conceptual design for an advanced reusable launch vehicle in the Vision Vehicle class. It is a horizontal takeoff, horizontal landing SSTO vehicle utilizing LOX/LH2 ejector scramjet rocket-based combined cycle (RBCC) propulsion. Hyperion is designed to deliver 20,000 lb. to LEO from the Kennedy Space Center. Gross weight is estimated to be 800,700 lb. and dry weight is estimated to be 123,250 lb. for this mission. Preliminary analysis suggests that, with sufficient launch traffic, Hyperion recurring launch costs will be under 200 dollars per lb. of payload delivered to LEO. However, nonrecurring costs, including development cost and acquisition of three airframes, is expected to be nearly 10.7B dollars. The internal rate of return is only expected to be 8.24 percent. Details of the concept design including external and internal configuration, mass properties, engine performance, trajectory analysis, aeroheating results, and concept cost assessment are given. Highlights of the distributed, collaborative design approach and a summary of trade study results are also provided.

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Component-Level Weight Analysis for RBCC Engines

1997-09 , Olds, John R. , McCormick, David Jeremy

Rocket-based combined-cycle engines (RBCC) engines have recently received increased attention for use on advanced, reusable space launch vehicles. By combining convention rocket and airbreathing operating modes into an integrated unit, they have given designers a middle ground between the high-thrust, low-Isp characteristics for a pure rocket and the low-thrust, high-Isp of pure airbreathers. Engine weight (or thrust-to-weight ratio) is a highly sensitive parameter in the design of advanced reusable launch vehicles. While substantial experience exists with ground-test engines from the 1960’s, little parametric data exists to help conceptual designers predict weight for today’s advanced technology, flight-weight RBCC engines. This paper reports a new set of component-level paramedic weight estimating equations for advanced rocket-based combined-cycle (RBCC) engines. These equations are derived from top-down regression analysis of historical data and include variables to account for advanced technologies and materials. Component weight equations are given as functions of engine geometry, internal pressure, flight modes, etc. Taken together, the equations are used to build up an overall RBCC weight estimation model - WATES. This spreadsheet-based model is not intended to replace a more detailed weight analysis, but rather to assist conceptual vehicle designers in assessing the relative advantages of various engine concepts. Sample RBCC engine weight predictions are given.

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Stargazer: A TSTO Bantam-X Vehicle Concept Utilizing Rocket-Based Combined Cycle Propulsion

1999-11 , Olds, John R. , Ledsinger, Laura Anne , Bradford, John Edward , Charania, Ashraf , McCormick, David Jeremy , Komar, D. R.

This paper presents a new conceptual launch vehicle design in the Bantam-X payload class. The new design is called Stargazer. Stargazer is a two-stage-to-orbit (TSTO) vehicle with a reusable flyback booster and an expendable LOX/RP upper stage. Its payload is 300 lbs. to low earth orbit. The Hankey wedge- shaped booster is powered by four LOX/LH2 ejector scramjet rocket-based combined-cycle engines. Advanced technologies are also used in the booster structures, thermal protection system, and other subsystems. Details of the concept design are given including external and internal configuration, mass properties, engine performance, trajectory analysis, aeroheating results, and a concept cost assessment. The final design was determined to have a gross mass of 115,450 lb. with a booster length of 99 ft. Recurring price per flight was estimated to be $3.49M. The overall conceptual design process and the individual tools and processes used for each discipline are outlined. A summary of trade study results is also given.

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System Robustness Comparison of Advanced Space Launch Concepts

1998-10 , McCormick, David Jeremy , Olds, John R.

This research proposes two methods to investigate the robustness differences between competing types of advanced space launch systems. These methods encompass two different phases of the advanced design process and are used to compare the relative advantages of two concepts in these phases. The first is a Monte Carlo simulation during the conceptual phase of design, where mold lines can be changed to account for uncertainty in weight assumptions. This tests the vehicle weight growth for a fixed mission. Here, the all-rocket single stage to orbit (SSTO) shows a more narrow distribution of dry weight, suggesting higher concept robustness. A study of vehicle mass ratio and mixture ratio combinations for both vehicles show the relative location of the results. The second phase represents the transition to detailed design. An optimization based on length determines the appropriate size for detailed design. This optimization takes into account uncertainties placed on both weight relationships and performance requirements. Both of these analyses utilize Crystal Ball Pro in conjunction with Microsoft Excel. This gives the technique compatibility with commonly used computer platforms. While the all-rocket SSTO does show an advantage in the area of system weight growth, several other factors are important in determining the viability of a reusable launch system, not the least of which is mission flexibility. Here the runway-operated RBCC SSTO has a distinct advantage.

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