Future Space Transportation Systems Research Articles

NASA's integrated space transportation plan

Improvements in the safety, reliability and affordability of current and future space transportation systems must be achieved if NASA is to perform its mission and if the U.S. space industry is to reach its full potential. In response to Presidential Policy in 1994, NASA, working with our industrial partners, initiated several efforts including the X-33, X-34, X-37 and Advanced Space Transportation programs with the goal of demonstrating the technologies that could enable these goals. We have learned that emerging technologies will enable the needed advancements but that more development along multiple, competing paths is needed. We have learned that developing requirements diligently and in partnership with industry will allow us to better converge with commercial capabilities. We have learned that commercial markets are not growing as fast as projected earlier, but there are still possibilities in the near-term to pursue alternate paths that can make access to space more robust. The goal of transitioning NASA's space transportation needs to commercial launch vehicles remains the key aim of our efforts and will require additional investment to reduce business and technical risks to acceptable levels.

X-38, CRV and CRV Evolution Program Overview and European Role

The X-38 Project forms part of the “X” prototype vehicle family developed by the United States. Its development was initiated by NASA to prepare the Crew Return Vehicle (CRV). The European participation in the X-38 Program has been significantly extended since the start of the X-38 cooperation in 1997 and is realized by ESA's “Applied Reentry Technology Program” and the German/DLR “Technologies for Future Space Transportation Systems” (TETRA) Project. European contributions to the X-38 Vehicle 201, (V-201) can be found in all technical key areas. The orbital flight and reentry with the X-38 V-201 will conclude the X-38 project in 2002. The CRV will be used from about mid-2005 as ’ambulance‘, ’lifeboat‘ or as alternate return vehicle for the crew of the International Space Station. Recognizing the very productive and mutually beneficial cooperation established on X-38, NASA and ESA have decided to continue this cooperation into the development of the operational CRV. The Phase C/D will be completed shortly after the Critical Design Review, scheduled for August 2002. The CRV production phase will start in October 2002 and will cover production of four CRV vehicles, ending in 2006. Based on the objective to identify a further evolution potential of the CRV towards a Crew Cargo Transfer Vehicle (CCTV), NASA has implemented upgrade studies in the CRV Phase C/D.

Concept and Preliminary Flight Testing of a Fully Reusable Rocket Vehicle

A fully reusable rocket vehicle is proposed to demonstrate good operability characteristics both on the ground and in e ight. For achieving technical readiness for future space transportation systems, design considerations not only for higher-performance-related issues but also those for good operability are needed. The proposed vehicle is to be used as a sounding rocket and has the capabilities of ballistic e ight, returning to the launch site, and landing vertically, making use of clustered liquid-hydrogen rocket engines. Before the development of this type of reusable rocket was initiated, a small test vehicle with a liquid-hydrogen rocket engine was built and e ight tested. A demonstration of vertical landing and exerciseof turnaround operation forrepeated e ightsare the major objectivesof the test vehicle. Two e ightswere performed in succession, and the e ight-test operation provided many valuable experiences for designing the fully reusable rocket vehicle.

Cycles for Earth-to-Orbit Propulsion

The reduction of Earth-to-orbit launch costs in conjunction with an increase in launcher reliability and operational efe ciency are the key demands on future space transportation systems. Results of various system analyses indicate that these demands can be met with future single-stage-to-orbit (SSTO) vehicles using advanced technologies for both structure and propulsion systems. This paper will provide a classie cation and description of all turbopump feed liquid rocket engine cycles, followed by a combined vehicle/propulsion analysis of the design parameters for the propulsion systems and their associated thermodynamic cycles for the launch of future SSTO vehicles. Existing and projected rocket engine cycles capable of SSTO missions will be presented.

Spaceplane Trajectory Optimization with Vehicle Size Analysis

A numerical method to solve simultaneous design and control optimization problems is considered. Firstly, the simultaneous optimization problem in this paper is transformed into a new formulated nonlinear programming problem. Considering using a sequential quadratic programming method, the diagonal form of the Hessian matrix for the Lagrange function is introduced in a new formulation named Block Diagonal Hessian (BDH) method. Finally, the present method is applied to simultaneous spaceplane design and trajectory optimization problems for feasibility study of a future space transportation system. Through several calculations, the proposed BDH method is confirmed to be effective for simultaneous optimization problems.

Future spacelift projection

In 1996 the NASA Advisory Council asked for a comprehensive look at future launch projections out to the year 2030 and beyond. In response to this request NASA sponsored a study at The Aerospace Corporation to develop long-range space transportation models for future commercial and government applications, and to analyze the design considerations and desired characteristics for future space transportation systems. Follow-ons to present space missions as well as a wide array of potential new space applications are considered in the study. This paper summarizes the space transportation system characteristics required to enable various classes of future missions. High reliability and the ability to achieve high flight rates per vehicle are shown to be key attributes for achieving more economical launch systems. Technical, economic and policy implications are also discussed.

ロケット用ターボポンプの極低温トライボロジー

The high-speed bearings and rotating-shaft seals of turbopumps which supply extremely low temperature propellants such as liquid oxygen (LO2) and liquid hydrogen (LH2) to liquid rocket engines are very important parts. However, the operating conditions of turbopump bearings and shaft seals are characterized by poor lubrication because of the low viscosity due to oxidation (LO2) or reduction (LH2). Therefore, turbopump bearings and shaft seals must be highly durable and reliable under extreme operating conditions in LO2 and LH2 environment. As a means of reducing launch costs, reusable rocket engines are required for future space transportation systems, and the durability of bearings and shaft seals in reusable turbopumps must be much greater than that of currently expendable turbopump bearings and shaft seals. For example, the required life of the reusable turbopump bearings and shaft seals of the space shuttle main engine (SSME) is 7.5 hours, which is 15 times longer than that required for the expendable LE-7 engine of the Japanese H-II rocket. However, a serious wear problem has been reported for the turbopump bearings of the SSME and hybrid ceramic bearings are now used in an attempt to reduce serious bearing wear. In order to develop turbopump bearings and shaft seals, many tribological problems for extremely low tomperatures and high rotating speeds must be solved. The cryogenic tribological problems experienced in the development of the turbopump bearings and shaft seals of the LE-5 engine for the H-I rocket and the LE-7 engine for the H-II rocket are introduced in this report. Additionally, the performance of a self-lubricating hybrid ceramic bearing developed to increase bearing life is described.

The actions of ESA to prepare for future European Space Transportation Systems

This paper describes the general characteristics of future space transportation systems, the preparatory work done by ESA beyond Ariane 5 and Hermes, the first results of the ESA General Studies on reusable launchers and winged launchers and the future European space transportation investigation programme.

On the optimum cruise speed of a hypersonic aircraft

Some preliminary results that have been obtained in the frame of the SANGER system studies are presented. SANGER is a West German study project and technology reference system for a future advanced space transportation system. The first stage of this vehicle is a hypersonic aircraft from which a passenger version could be derived. The analyses indicate that a speed of Mach 4.4 will lead to maximum seat mileage per day as well as to minimum propellant consumption. The speed-related cruise altitude of 24500 m or 80000 ft is above the most sensitive ozone layer and high enough to produce only one-third of the noise ground pressure which is considered as the acceptable limit (1 lb/ft/sup 2/) over populated areas. The aircraft surface temperatures at these conditions can still be managed by a conventional titanium alloy structure with special provisions only at the leading edge and the engine inlets. The potential route structure and economics of such an aircraft are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Flight analysis for a two-stage launch vehicle with a glideback booster

This paper focuses on the flight performance analysis conducted on a Future Space Transportation System (FSTS). The configuration chosen for the study was a two-stage, fully reusable, vertical liftoff, horizontal landing system with a payload capability of 150,000 Ib. The engines on the two stages are burned in parallel with the booster providing all the propellant for both stages until staging occurs at Mach 3. Because the orbiter tanks are full and the booster tanks are empty at staging, the center of gravity (e.g.) shifts dramatically from liftoff to staging conditions. A scheme to trim the vehicle with this large lateral e.g. travel has been developed that uses both gimballing and throttling of the engines. After staging, the booster glides back to the launch site. To demonstrate the feasibility of this maneuver, predicted booster aerodynamics have been analyzed, and the glideback trajectories have been modeled. Also, various adverse wind profiles have been used to show the performance margins inherent in the glideback of the booster. An abort analysis for the FSTS system was conducted to determine the ascent reserves required for each stage. The effect of losing one or two engines on either stage was also investigated.

Structural concepts for future space transportation system orbiters

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Honeycomb sandwich structure for future space transportation systemswith integral cryogenic tankage

This paper presents the status of the structural development of an integral cryogenic-tankage/hot-fuselage concept for future Space Transportation Systems (STS). The concept consists of a honeycomb sandwich structure which serves the combined functions of containment of cryogenic fuel, support of vehicle loads, and thermal protection from an entry heating environment. The inner face sheet is exposed to a cryogenic (LH2) temperature of -423°F during boost; and the outer face sheet, which is slotted to reduce thermal stress, is exposed to a maximum temperature of HOOT during a high-altitude, gliding entry. A fabrication process for a Ren£ 41 honeycomb sandwich panel with a core solidity less than 1% has been developed, which is consistent with desirable heat treatment processes for high strength. Preliminary structural allowables and thermal properties for use in structural system studies have been determined; two 1 x6 ft panels have been tested with combined thermal and mechanical loads; and the effects of slots used to reduce stresses in the outer face sheet on the lower surface of the vehicle have been evaluated in the cryogenic environment associated with containment of LH2 fuel. Based on the work presented in previous system studies and the hardware development described herein, the Rene' 41 honeycomb sandwich appears to be a viable structural concept for an integral cryogenictank/hot-fuselage structure; however, additional in-depth studies, hardware development, and testing are required to verify the concept fully.

Simulation model for the operation of space freighters

This paper makes the attempt to illustrate the need for a detailed operational analysis of future space transportation systems with the help of computer-based simulation models. The basic approach deemed suitable for such a systems simulation is explained in some detail. A reference program (100,000 Mg payload per year during 25 years) for a reference mission (heavy cargo transport to GEO for SPS construction) has been selected. A base-line launch vehicle (fully reusable ballistic all chemical three stage vehicle) has been defined, which is considered a serious applicant for such a mission. It was found that the take-off mass of this type of vehicle should be as large as practical from the viewpoint of cost-effectiveness. The example chosen has a GLOW of 10,000 Mg and lifts more than 100 Mg to GEO. With consideration of the operational parameters the simulation model evaluates the annual production rates, inventory of stages, utilization of facilities and operational cost, which amount within this frame of reference to about 96 $/kg net payload delivered to GEO in terms of 1980 dollars and contribute the main share to the total transportation cost.

Future low-cost space transportation system analysis

Future low-cost space transportation system analysis